HK1175762B - Diverter for sorter and method of diverting - Google Patents

Description

Diverter for a sorter and method of diverting

Technical Field

The present invention relates to a conveyor system, and more particularly to a diverter for use with a positive displacement sorter comprised of a traveling belt having an upper surface defining a longitudinally traveling conveying surface. The belt is defined by a series of interconnected transversely elongated slats and pusher shoes that travel along the slats. Diverting members on each shoe extending below the conveying surface are engaged by a particular diverting rail to divert articles traveling on the conveying surface laterally. The diverter selectively moves one or more of the diverting members to the associated diverting rail to initiate the diversion.

Disclosure of Invention

In accordance with one aspect of the invention, a positive displacement sorter and method of diverting articles using a positive displacement sorter includes providing a plurality of interconnected parallel slats defining an endless belt traveling in a longitudinal direction, an upper surface of the endless belt defining an article conveying surface. A plurality of pusher shoes each travel along at least one of the slats to laterally divert articles on the conveying surface. Each shoe has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters each selectively divert at least one diverting member from a non-diverting path extending longitudinally along the sorter to one diverting rail in a diverting state.

The diverter includes a gate having a diverting surface. The gate is selectively movable between a diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. The actuator is a rotary actuator having a generally horizontal axis of rotation.

The rotary actuator may be a rotary solenoid or a brushless torque actuator. The gate rotates between the diverting and non-diverting states about another horizontal axis that is generally concentric with the generally horizontal axis of rotation. A slip joint may be provided between the rotary actuator and the gate. The slip joint resists reversing motion transmitted from the gate to the rotary actuator.

Sensors may be provided to monitor the operation of the commutator. The sensor detects a commutation state of the gate and/or a non-commutation state of the gate. An electronic commutation controller may be provided which applies an activation control signal to the actuator to operate the gate between one state and another. The controller monitors the sensor and adjusts the start control signal in response to movement of the gate. The controller may adjust the activation control signal to provide critical damping of the movement of the gate between the two states.

The gate may include a mechanical biasing means which tends to return the gate to one of the states. The controller may provide a return control signal when the gate is moved to one of the states. The return control signal at least partially counteracts the biasing means. The controller may adjust the return control signal based on movement of the gate. The controller may adjust the return control signal to provide critical damping of the movement of the gate between the two states.

The gate may include a flexible member defining a diverting surface. The flexible member absorbs the impact due to contact between the diverting member and the diverting surface. The diverting member may include a rotational bearing and a pin extending below the bearing, the gate positioning the diverting surface to engage the bearing in the diverting state. The diverting surface may be in the form of a curved surface. Alternatively, the gate may position the diverting surface to engage the pin when in the diverting state.

The generally horizontal axis of the actuator may be oriented at least partially in the longitudinal direction. The generally horizontal axis of the actuator may be oriented at least partially in the lateral direction, or at some intermediate orientation between the longitudinal and lateral directions.

In accordance with another aspect of the invention, a positive displacement sorter and method of diverting articles using a positive displacement sorter includes providing a plurality of interconnected parallel slats defining an endless belt traveling in a longitudinal direction, an upper surface of the endless belt defining an article conveying surface. A plurality of pusher shoes each travel along at least one of the slats to laterally divert articles on the conveying surface. Each shoe has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters each selectively divert at least one diverting member from a non-diverting path extending longitudinally along the sorter to one diverting rail in a diverting state.

The diverter includes a gate having a diverting surface. The gate is selectively movable between a diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. The electronic commutation controller applies an activation control signal to the actuator to move the gate between one state and another. The controller monitors movement of the gate and adjusts the start control signal based on the movement of the gate.

The controller may adjust the activation control signal to provide critical damping of the movement of the gate between one state and another. The controller may adjust the activation control signal to apply an actuation current of a minimum duration that causes the gate to change state. The activation control signal may include an actuation signal applied to the actuator, and the controller interrupts the actuation signal before the gate reaches the other state and initiates the gate hold signal when the gate substantially reaches the other state. The controller adjusts the actuation signal or the gate hold signal based on a comparison of the time it takes for the gate to change from one state to another.

The controller may compare the most recent time taken for the gate to move between one state and another with a historical time taken for the gate to move between one state and another, and display an error condition if the most recent time is substantially different from the historical time.

The gate may include a mechanical biasing device that tends to return the gate to one state. The controller may provide a return control signal when the gate is moved to a state. The return control signal counteracts the biasing means. The controller may adjust the return control signal based on movement of the gate. The controller may adjust the braking signal to provide critical damping of the movement of the gate between the other state and the one state. The controller may apply a minimum duration of braking current that causes the gate to substantially avoid mechanical shock when returning to a state. The controller may adjust the return control signal based on a comparison of the time it takes for the gate to change from one state to another.

In accordance with another aspect of the invention, a positive displacement sorter and method of diverting articles using a positive displacement sorter includes providing a plurality of interconnected parallel slats defining an endless belt traveling in a longitudinal direction, an upper surface of the endless belt defining an article conveying surface. A plurality of pusher shoes each travel along at least one of the slats to laterally divert articles on the conveying surface. Each shoe has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters each selectively divert at least one diverting member from a non-diverting path extending longitudinally along the sorter to one diverting rail in a diverting state.

The diverter includes a gate having a diverting surface. The gate is selectively movable between a diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. An electronic commutation controller controls the actuator to move the gate between one state and another. The gate includes a mechanical biasing device that tends to return the gate to one of the states. The controller provides a return control signal when the gate is moved to one of the states. The brake signal at least partially obstructs the biasing means.

The controller may adjust the return control signal based on movement of the gate. The controller may adjust the return control signal to provide critical damping of the movement of the gate between the other state and the one state. The controller may apply a minimum duration of braking current that causes the gate to substantially avoid mechanical shock when returning to one of the states. The controller may adjust the return control signal based on a comparison of the time it takes for the gate to change from one state to another.

In accordance with another aspect of the invention, a positive displacement sorter and method of diverting articles using a positive displacement sorter and diverter assembly includes providing a plurality of interconnected parallel slats defining an endless belt traveling in a longitudinal direction, an upper surface of the endless belt defining an article conveying surface. A plurality of pusher shoes each travel along at least one of the slats to laterally divert articles on the conveying surface. Each shoe has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article.

A plurality of diverter assemblies are provided to selectively divert at least one diverting member from a non-diverting path extending longitudinally along the sorter to a diverting rail. At least one commutator assembly includes first and second redundant commutators. Each redundant diverter is capable of selectively diverting at least one diverting member from a non-diverting path to a diverting rail.

The first redundant diverter may be a magnetic diverter that at least partially diverts at least one diverting member from a non-diverting path to one of the diverting rails using magnetic force. The second redundant diverter may be a mechanical diverter that utilizes mechanical force to at least partially divert at least one of the diverting members from a non-diverting path to one of the diverting rails.

In accordance with another aspect of the invention, an actuator assembly includes an actuator having a shaft and a coil. The shaft is selectively movable between a first state and a second state. The coil moves the shaft between a first state and a second state. The electronic controller applies an activation control signal to the coil to move the shaft between one state and another state. The controller monitors the movement of the shaft and adjusts the activation control signal based on the movement of the shaft to provide critical damping for the movement of the shaft.

In accordance with another aspect of the invention, an actuator assembly includes an actuator having a shaft and a coil. The shaft is selectively movable between a first state and a second state. The coil moves the shaft between a first state and a second state. An electronic controller controls the coils to move the shaft between one state and another. The shaft includes a mechanical biasing device that tends to return the shaft to one of the states. The controller provides a return control signal when the shaft moves to one of the states. The return control signal at least partially counteracts the biasing means.

These and other objects, advantages and features of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a perspective view of a positive displacement sorter for use with the present invention;

FIG. 2 is a side view of a pusher shoe for use with the sorter of FIG. 1;

FIG. 3 is a top plan view of the reversing assembly for the access position;

FIG. 4 is an enlarged view of the area indicated at IV in FIG. 3;

FIG. 5 is an enlarged view of the area indicated at V in FIG. 3;

FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5, showing the commutator in a commutating condition;

FIG. 7 is an enlarged view of the area indicated at VII in FIG. 5 with the cover removed to reveal internal details thereof;

FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7, showing the commutator in a commutating condition;

fig. 9 is a sectional view taken along line IX-IX in fig. 7, showing the commutator in a non-commutating condition;

fig. 10 is a perspective view of the commutator;

FIG. 11 is a sectional view taken along line XI-XI in FIG. 10;

FIG. 12 is the same view as FIG. 11 showing an exploded side view of the slip joint;

FIG. 13 is the same view as FIG. 11, showing the gate in the diverting condition;

FIG. 14 is a perspective view of a gate condition sensor associated with the gate shown in FIG. 11 in a non-diverting state;

FIG. 15 is the same view as FIG. 14, showing the gate of FIG. 13 in the diverting condition;

FIG. 16 is a block diagram of an electronic commutation controller;

17 a-17 d are timing diagrams illustrating the operation of the commutation control module of FIG. 16;

18 a-18 q are flow charts of a commutation control routine, including occasional signal diagrams on certain map pages to show the state of the start control signal and the return control signal;

FIG. 19 is an electrical schematic of the drive circuit;

FIG. 20 is a perspective view of a commutator assembly with redundant commutators, with the mechanical commutator shown in a non-commutated state;

FIG. 21 is the same view as FIG. 20, with the mechanical commutator shown in the commutating condition;

FIG. 22 is the same view as FIG. 20 of an alternative embodiment thereof;

FIG. 23 is the same view as FIG. 22, with the mechanical commutator shown in the commutating condition;

fig. 24 is a sectional view taken along line XXIV-XXIV in fig. 22;

fig. 25 is a sectional view taken along line XXV-XXV in fig. 23;

figure 26 is a perspective view of a commutator in a non-commutating condition from the commutator assembly of figure 22;

FIG. 27 is the same view as FIG. 26 with the commutator in the commutating condition;

FIG. 28 is an end view of the diverter of FIG. 26 in the diverting state;

figure 29 is the same view as figure 28 of the commutator of figure 27 in the commutating condition;

FIG. 30 is the same view as FIG. 20 of another alternative embodiment thereof;

FIG. 31 is the same view as FIG. 30, with the mechanical commutator shown in the commutating condition;

FIG. 32 is a cross-sectional view taken along line XXXII-XXXII in FIG. 30;

FIG. 33 is a cross-sectional view taken along line XXXIII-XXXIII in FIG. 31;

figure 34 is a perspective view of a mechanical commutator from the commutator assembly shown in figure 30;

FIG. 35 is a bottom plan view of the commutator of FIG. 34 in a non-commutating condition;

FIG. 36 is the same view as FIG. 35 in the reverse condition; and is

Figure 37 is a cut-away perspective view of a brushless torque actuator for use with an embodiment of the present invention.

Detailed Description

Referring now to the drawings and the illustrated embodiment depicted therein, a positive displacement sorter 30 includes an endless belt (endless web)32 traveling in a longitudinal direction, an upper surface of the endless belt 32 defining an article conveying surface 34 (fig. 1). The belt 32 is defined by a series of transversely elongated parallel slats (slats) 36, which slats 36 are interconnected at their ends. A plurality of pusher shoes (38) travel along one or more of the slats to laterally divert articles a on the conveying surface 34, such as to a particular chute (not shown). The sorter 30 may be of any type known in the art, such as those described in commonly assigned U.S. patent nos. 5,127,510; 6,814,216, respectively; 6,860,383, respectively; 6,866,136, respectively; 7,086,519, respectively; 7,117,988, respectively; 7,513,356 and 7,240,781, the disclosures of which are incorporated herein by reference.

Each slide 38 comprises a diverting member 39, which diverting member 39 extends below the conveying surface 34 to laterally displace the pushing slide, as will be described in more detail below (fig. 2). The reversing member 39 may include a bearing 52 and a pin 54 extending coaxially below the bearing.

Sorter 30 also includes a divert assembly 41 (fig. 3) for each divert destination below conveying surface 34. The commutation assembly 41 includes a commutator module 50 and one or more commutation tracks 42, the commutator module 50 being comprised of a plurality of commutators 43, the commutation tracks 42 terminating at a termination assembly 45. Each diverter 43 is capable of selectively diverting one or more diverting members 39 from the non-diverting path 40 to a diverting rail 42 extending from the diverter assembly to cause the associated pusher shoe 38 to travel across the conveying surface 34 to laterally displace articles a traveling on the conveying surface. A non-diverting path 40 extends longitudinally along sorter 30 below conveying surface 34 to guide diverting member 39 of the slide until diverting member 39 is diverted. Each diverting rail 42 can engage the diverting member 39, such as at bearing 52 or alternatively at pin 54, to cause the associated shoe 38 to travel laterally to divert an article. Each diverting rail 42 may incorporate a nose 51, the nose 51 having a movable member 53, the movable member 53 being deflectable if it strikes the diverting member 39 of the pusher slider in a manner that tends to increase the opening facing the corresponding diverting rail 42 and thereby complete a partial divert, as disclosed in more detail in commonly assigned U.S. patent application publication No.2009/0139834a1, the disclosure of which is incorporated herein by reference (fig. 7).

The termination assembly 45 includes a series of generally boat-shaped bumpers 46, the bumpers 46 having first surfaces 47a, the first surfaces 47a guiding the diverting members 39 traveling along the associated diverting rail 42 to a diverting path 48. Bumper 46 also includes a second surface 47b, second surface 47b guiding diverting member 39 traveling along diverting path 48. In the illustrated embodiment, the bumpers 46 have a symmetrical configuration, which allows them to be efficiently installed regardless of orientation. The reversing rail 42 may be made of a structural plastic material, such as nylon, on a vertical steel support plate to reduce noise and/or cost. The bumper 46 and other portions of the reversing assembly 41 may also be made of structural plastic such as UMHW (ultra high molecular weight polyethylene).

Each diverter 43 is a mechanical diverter that at least partially diverts the diverting member 39 with mechanical force in a diverting state from the non-diverting path 40 to an associated one of the diverting rails 42 (fig. 6-11). Each commutator 43 is actuatable by an electronic commutation controller 56 shown in fig. 16 and described in more detail below. The electronic commutation controller 56 receives a timing input 318a from the slat sensor 61 a. In the illustrated embodiment, the slat sensor 61a is a proximity sensor (proximity sensor) that monitors movement of the slats 36 to actuate the diverter to engage the selected diverting member 39 when appropriate, without the diverting members not selected for actuation interfering with the diverter. However, other types of sensors are possible. The electronic commutation controller 56 can also receive timing inputs 318b from the pin sensor 61 b. In the illustrated embodiment, the pin sensor 61b is a proximity detector that detects the bearing 52 of the push slide 38 to allow the commutation controller 56 to incorporate the inputs 318a, 318b to more accurately determine the position of the commutation member 39.

A plurality of commutators 43 may be incorporated into one commutator module 50. Such diverter modules may be used to mount the diverter assembly and at least a portion of the diverting track 42 associated with a diverting location, such as a chute or an access conveyor, if the sorter is a parallel diverting sorter. Each diverter 43 includes a gate 72 having a diverting surface 74. Gate 72 is selectively movable between a diverting orientation or diverting state shown in fig. 6 and 8 and a non-diverting orientation or non-diverting state shown in fig. 9 and 10. When gate 72 is in the diverting state, diverting surface 74 can selectively divert one or more diverting members 39 from non-diverting path 40 to its associated diverting rail 42. When gate 72 is in the non-diverting state, the position of diverting surface 72 allows one or more diverting members 39 to continue traveling along non-diverting path 40. In the illustrated embodiment, the gate is formed from a durable polymeric material such as Delrin (Delrin), or the like.

Diverter 43 also includes an actuator 76, actuator 76 being capable of actuating shutter 72 between its non-diverting state and its diverting state. The actuator 76 is a rotary actuator having a generally horizontal axis of rotation. The rotary actuator 76 may be in the form of a rotary solenoid of the type known in the art. Alternatively, the rotary actuator 76 may be in the form of a brushless torque actuator 78 shown in fig. 37, the brushless torque actuator 78 having a connector 66 for connecting the electronic commutation controller 56. The gate 72 is rotatably mounted to the shaft 98 for rotation about another horizontal axis that is concentric with the generally horizontal axis of rotation of the rotary actuator 76 between the diverting and non-diverting orientations. A slip joint 80 may be provided between rotary actuator 76 and gate 72 to resist reversing motion transmitted from gate 72 to rotary actuator 76. In the illustrated embodiment, the sliding joint 80 is defined by a slot 90 in the gate 72, the slot 90 being engaged by an extension 92 of a paddle member 94, the paddle member 94 being mounted to a generally horizontal shaft 96 of the rotary actuator 76. Extensions 92 are free to move radially and/or axially within slots 90 relative to shafts 96 and 98, thereby preventing impacts from being transmitted from diverting surface 74 to shaft 96. The presence of the slip joint avoids the difficulties associated with known mechanical commutators that utilize a rotary solenoid having a vertically oriented shaft. In this known system, the shock and vibration in the commutator caused by the contact of the commutation member can be directly transmitted to the rotary solenoid, thereby reducing the service life of the rotary solenoid.

The commutator 43 may include a sensor 62 for monitoring the operation of the commutator. The sensor 62 detects rotation of the paddle member 94 to determine when the gate reaches a particular state. In the illustrated embodiment, the sensor 62 is comprised of a proximity sensor 84, the proximity sensor 84 detecting one or more markers 86a, 86b positioned at the paddle member 94, but the markers may be positioned at other locations of the gate. As the gate 72 rotates, the indicia 86a, 86b move out of the detection range of the sensor 84 to indicate a change in the state of the gate.

Gate 72 may include a flexible member 87 that defines diverting surface 74. Flexible member 87 absorbs the impact generated by contact between diverting member 39 and diverting surface 74. In the illustrated embodiment, a portion of gate 72 is hollowed out to define a cavity 88 at the rear of diverting surface 74. The presence of cavity 88, the thickness of member 87, and the material defining gate 72 may be selected to give member 87 a desired degree of flexibility that is within the ability of those skilled in the art.

Gate 72 is configured to position diverting surface 74 to engage bearing 52 of diverting member 39 when the gate is in its diverting orientation. This tends to reduce wear on the diverting surface 74 because the diverting surface 74 engages a freely rotating member. Thus, during commutation, the movement of the commutating member 39 relative to the commutating surface 74 is at least partially a rotation, rather than a sliding. To enhance the interaction between the diverting surface 74 and the bearing 52, the member 87 may be configured to provide a curved surface for the diverting surface. However, it will be appreciated that other embodiments of the invention provide a gate that positions the diverting surface to engage pin 54 when in the diverting orientation, as will be described in detail below. In the illustrated embodiment, no special material is applied to the diverting surface 74 to increase its stiffness. Diverting surface 74 is defined by the polymeric material forming gate 72.

In diverter 43, the generally horizontal axis of rotary actuator 76 is generally longitudinally oriented to align with the movement of belt 32. However, other horizontal orientations of the axis of rotation of the rotary actuator are possible. For example, in embodiments that will be described in greater detail below, the horizontal orientation of the axis of rotation of the rotary actuator may be generally oriented transversely to align with motion perpendicular to the belt 32, or may be oriented at an angle between the transverse and longitudinal orientations.

In the illustrated embodiment, shutter 72 is selectively movable by actuation system 300 from a non-reversing state to a reversing state under power of actuator 76, and back to the non-reversing state under the bias of a mechanical biasing device 332, which may be a mechanical spring or the like (fig. 16-19). Alternatively, the actuator may move the gate from the diverting state to the non-diverting state and return the gate to the diverting state using the biasing device 332. The actuation system 300 includes the electronic commutation controller 56, and the electronic commutation controller 56 applies an actuation current to the coil 302 of the actuator 76 at outputs 308a, 308b in accordance with the enable control signal 219 to move the gate 72 between one state and another state and to hold the gate 72 in that state. Controller 56 is comprised of a driver circuit 304 and a programmed microprocessor 306 or other type of logic control circuit known in the art. Microprocessor 306 receives inputs 318a from slat sensors 61a that detect the leading and trailing edges of slats 36, and inputs 318b from pin sensors 61b for detecting bearings 52, to provide timing signals for drive circuit 304 to move gate 72 as appropriate to intercept the desired diverting member 39 to be diverted without disturbing any preceding or trailing diverting member 39 that is not intended to be diverted by the gate. Microprocessor 306 also receives a gate movement input 309 from proximity sensor 84 to monitor movement of gate 72 and adjust an activation control signal 219 based on the movement of the gate, as will be described in greater detail below. The enable control signal 219 consists of an actuation signal 320, a flux dissipation interval 322, and a gate hold signal 324.

To control the drive circuit 304, the microprocessor 306 supplies the circuit 304 with a shutdown mode signal 310, a master enable signal 312, and a direction signal 314. The off mode signal 310 operates in a manner in which the drive circuit 304 interrupts the actuation signal 320 and dissipates the magnetic flux accumulated in the coil 302 during a magnetic flux dissipation period 322, as will be explained in more detail below. The master enable signal 312 instructs the drive circuit 304 to start and stop the actuation signal 320 and the gate hold signal 324. The directional signal 314 causes the outputs 308a, 308b to drive current through the coil 302 in a direction to produce an actuation signal 320 that moves the actuator 76 and a gate hold signal 324 that holds the actuator; or passing current through the coil 302 in the opposite direction to produce a demagnetization pulse 326 that quickly dissipates the magnetic flux in the coil 302. The driver circuit 304 supplies an acknowledge signal 316 to the microprocessor 306 to acknowledge the current supply to the coil 302. Microprocessor 306 uses this confirmation signal 316 to help monitor the movement of gate 72 so that microprocessor 306 will be able to discern whether marker 86a or marker 86b was detected by proximity sensor 84.

The manner in which the actuation system 300 operates can be seen by reference to fig. 17a to 17 d. Fig. 17a shows the movement of shutter 72 (from time stamp 1 to time stamp 2) during the start-up scan (sweep) when actuator 76 moves shutter 72 from one state to the other against the bias of biasing device 332. During the holding position (from time marker 2 to time marker 3), actuator 76 holds shutter 72 in the other state against the bias of biasing device 332. During the return scan (from time marker 3 to time marker 5), the bias of the biasing device 332 returns the shutter 72 from another position to one position or the home position. Fig. 17b, which is aligned with the time stamp of fig. 17a, shows that current is supplied to the coil 302 by the drive circuit 304. To begin moving shutter 72 to another position, drive circuit 304 applies an activation control signal 319, activation control signal 319 beginning with an actuation signal 320 applied to coil 302. This causes the shutter 72 to start moving. Before the gate 72 reaches another position, the actuation signal 320 is interrupted and the magnetic flux in the coil 302 dissipates during a flux dissipation interval 322. At about the time the gate reaches the other state (at time marker 2), a gate hold signal 324 is applied to the gate temporarily stationary to hold the gate in the other state against the bias of the biasing device 332 for the duration of the holding position (from time marker 2 to time marker 3).

As will be described in more detail below, the relative times of actuation signal flux dissipation interval 322 and shutter hold signal 324, which together make up actuation control signal 319, may be adjusted in a feedback loop to provide critical damping of the movement of shutter 72 during its actuation sweep. In particular, this critical damping causes the bias of biasing device 332 to stop gate 72 when the gate substantially reaches the other state. Return control signal 325 is executed when microprocessor 306 determines from slat sensor input 318a and pin sensor input 318b that it is time to return gate 72 to the home position. The return control signal 325 may optionally provide a demagnetization pulse 326 (at time mark 3) to quickly dissipate the magnetic flux in the coil 302 so that the gate 72 may immediately begin the return scan. The demagnetization pulse 326 is optional, and if the coil 302 is not large, the demagnetization pulse 326 may not be needed. After the demagnetization pulse 326 (if any), the coil 302 enters a no-motion period 328 (from the end of the demagnetization pulse to time marker 4), and no current is applied to the coil during the no-motion period 328. During the no-motion period 328, the bias of the biasing device 332 moves the shutter 72 toward its original state. Before the shutter reaches the original state, the drive circuit applies a de-actuation signal 330 (between time markers 4 and 5) that operates against a biasing device 332 to prevent movement of shutter 72 when shutter 72 substantially reaches the home position. The timing of return control signal 325 can be controlled in a feedback loop to provide critical damping of the motion of shutter 72 during the return scan.

It can thus be seen that the commutation controller 56 can adjust the start control signal 319 and/or the return control signal 325 to provide critical damping of the movement of the gate 72 between one state and another. The commutation controller 56 can adjust the start control signal 319 to apply an actuation current of a minimum duration that can cause the gate to change state. Commutation control module 56 may interrupt actuation signal 320 during flux dissipation interval 322 before the gate reaches another state. Critical damping of the movement of gate 72 may be achieved by reversing control module 56 adjusting enable control signal 319 based on a comparison of the velocity of gate 72, which is determined by the time it takes gate 72 to change from one, or original state, to another, or enabled state during a current or previous enable cycle. This may be accomplished by adjusting the enable control signal 319. In the illustrated embodiment, this is accomplished by having an actuation signal 320 of constant duration and adjusting the start time of the gate hold signal 324. However, alternatively, the duration of the actuation signal 320 may vary.

By providing critical damping for the actuation of the diverter gate, the actuation system can minimize the amount of time it takes for the gate to move from one state to another. This is because there is no need to wait for the gate to settle out of mechanical bounce that would otherwise be experienced when the gate reaches the mechanical limit of travel. As will be appreciated by those skilled in the art, the ability to reduce the time it takes for the diverter 43 to reliably change from the home position to the actuated position allows the belt 32 to move at a faster speed for a given slat pitch. Further, critical damping of the motion of gate 72 may eliminate the need for mechanical damping at the end of gate travel in the actuated state. Also, avoiding mechanical shocks that resist mechanical stops in the actuated state due to critical damping can extend the useful life of the commutator and its actuator.

In addition, the divert control module 56 may maintain a running average time for the gate 72 to move from one state to another. (time may be converted to gate speed, so time will be used interchangeably herein with speed.) control module 56 may compare the most recent time it took the gate to move between the two states with the historical time it took the gate to move between the two states, so that if the most recent time is substantially different from the historical time, an error condition is displayed on error display output 334. This extension in time can be the result of debris accumulation in a commutator operating in a relatively harsh environment. This lengthening of time is typically noted first during the return scan (from time marker 3 to time marker 5) as the movement of the shutter is guided by the mechanical biasing device 332. Error display output 334 may be supplied to, for example, a superordinate controller (not shown) to require maintenance of sorter 30.

As described above, the commutation control module 56 can provide a return control signal 325 when the gate 72 moves from the actuated state to the original state during the return scan. The return control signal 325 includes a brake signal 330, the brake signal 330 canceling the bias provided by the mechanical biasing device 332. The divert control 56 may adjust each occurrence of the return control signal 325 based on the movement of the gate 72. In particular, the commutation controller 56 can adjust the return control signal 325 to provide critical damping of the movement of the gate between the other, or actuated state, and the one, or original state. This may be accomplished by commutation controller 56 applying a minimum level of brake signal 330, where minimum level of brake signal 330 can cause gate 72 to avoid mechanical shock when returning to the original state. Diverter controller 56 may adjust return control signal 325 based on a comparison of the time it takes gate 72 to change from the actuated state to the original state to the same time during this or a previous cycle of diverter 43.

By providing critical damping using the return control signal, the system can further reduce the amount of time it takes to move between the two states. This is because there is no need to wait for the gate to settle in the original condition from mechanical bounce that would otherwise be experienced when the gate reaches the original condition under operation of the biasing device 332. As will be appreciated by those skilled in the art, the ability to reduce the time it takes for the diverter 43 to reliably change from the actuated state to the original state allows the belt 32 to move at a faster rate for a given slat pitch. In addition, critical damping of the motion of gate 72 may eliminate the need for mechanical damping at the end of gate travel in the original state. And, the service life of the commutator and its actuator can be prolonged by avoiding mechanical shock against mechanical stop in the original state due to critical damping of the return to the original state.

In the illustrated embodiment, the driver circuit 304 is a controlled current circuit. For reference, it can be seen in fig. 17c that the voltage measured across the coil 302 is shown as a voltage signal 336. However, as will be appreciated by those skilled in the art, it is understood that the driver circuit 304 may alternatively operate as a controlled voltage circuit. In the illustrated embodiment, the drive circuit 304 utilizes an H-bridge configuration to generate current in the coil 302 through the actuation/braking wires 308a, 308b (fig. 19). Control circuit 304 includes an H-bridge 340 comprised of separate legs, one leg comprised of series connected transistors Q7 and Q15 and the other leg comprised of series connected transistors Q3 and Q11, wherein the legs are connected in parallel between a DC voltage source 342 and ground 344. The node between transistors Q7 and Q15 provides one wire 308a to the coil 302. The node between transistors Q3 and Q11 provides another line 308b to the coil 302. A set of precision resistors R142, R148, and R153 connected in parallel with each other is used to detect the current flowing through the coil 302 on the current detection line 346. In the illustrated embodiment, the voltage supply 342 operates at 340VDC (nominal voltage). However, greater or lesser voltages may be used.

A pair of half-bridge drive circuits U22 and U23 each drive half of the bridge 340. In particular, the driver circuit U22 operates the transistors Q7 and Q15 to turn the transistors on and off in a proper sequence so that only one transistor is on at a time. In a similar manner, the driver circuit U23 operates transistors Q3 and Q11. A Pulse Width Modulation (PWM) circuit U48 coordinates the operation of the half bridge drive circuits U22 and U23 to produce a controlled current in the coil 302 by generating PWM to the coil. The PWM circuit U48 senses the voltage on the current sense line 346 and regulates the half bridge drive circuits U22 and U23 to produce a controlled current in the coil 302. To generate the actuation signal 320, the gate hold signal 324, and the brake signal 330, the transistors Q7 and Q11 are turned on and off, and the transistors Q3 and Q15 remain turned off or on.

The main enable signal 312 from the microprocessor 306 causes the half-bridge drive circuits U22 and U23 to enable the bridge 340. The off mode signal 310 from the microprocessor 306 in conjunction with the main enable signal 312 indicates what mode the drive circuits U22 and U23 are to employ to dissipate the magnetic flux in the coil 302, for example, when the actuation signal 320 is interrupted during the magnetic flux dissipation period 322. For example, in a mode known as a "reverse braking" mode, either the two top transistors Q7 and Q3 or the two bottom transistors Q15 and Q11 are turned on together to dissipate the magnetic flux in the coil 302 that causes the movement of the commutator gate to slow. Alternatively, in a mode referred to as a "regenerative" mode, all of the transistors Q3, Q7, Q11, and Q15 are open to more rapidly dissipate the magnetic flux in the coil 302 back through the voltage supply 342. In the reverse braking mode, in the illustrated embodiment, slower magnetic flux dissipation is used within magnetic flux dissipation interval 322 to enable more control over the relationship between actuation signal 320 and magnetic flux dissipation interval 322. However, alternatively, a regeneration mode may be used. To generate the demagnetization pulse 326, the transistors Q3 and Q15 are turned on to generate a reverse current in the coil 302, and the transistors Q7 and Q11 remain off or on.

The acknowledgement signal 316 is responsive to the voltage at the current sense node 346 to inform the microprocessor 306 that current is flowing through the coil 302. This allows the microprocessor 306 to verify proper electrical operation of the combination of the H-bridge drive circuit 304 and the actuator coil 302 of the commutator gate.

The commutation control routine 400 runs on the microprocessor 306. In the illustrated embodiment, routine 400 is an interrupt driver that is repeatedly executed based on an interrupt signal generated, for example, every 250ms (fig. 18a through 18 q). When an interrupt occurs (402), the program checks all its inputs (404) and evaluates the current state of the inputs (406) for use in subsequent evaluation of the program in the gate control state machine (410a, 410b.. 410 n). After performing additional administrative tasks (408), the program 400 then accesses the gate control state machine (410a, 410b.. 410 n). For each commutator 43, one state machine is set and managed per interrupt interval.

The state machine 410a accesses different portions of the routine 400 depending on whether the diverter 43 is in the home position (412), undergoes a start scan to the divert position (414, 414a.. 414d) at the divert position (416), or undergoes a return scan to the home position (418, 418a.. 18 g).

While in the home state 412 and at the home non-diverting position (420), the program determines whether the proximity sensor element 84 is in condition to monitor the flags 86a and 86b to confirm that the diverter gate is within range of the home position (422). If so, then a determination is made whether a start scan triggering event has started (424). If not, the program remains in state 420 to reevaluate subsequent interrupts until a start scan triggering event occurs (428). The current iteration (410a) of this state machine ends, allowing the processor to proceed through the state machines (410b.. 410n) associated with the other gates. If it is determined at 424 that a state initiated scan triggering event has occurred, then scan initiation is initiated by providing current to the actuator 76 (426) and the state machine advances for the management of the initiated scan on the next interrupt drive iteration of this gate state machine. The current iteration of this state machine ends.

If it is determined at 422 that the proximity sensor 84 confirms that the shutter is not at the home position, it is determined whether the reversing position (station) is in the automatic reversing mode (430). If so, then it follows that a significant error event has been detected during the automatic mode, which results in an error display in line 334 and a future automatically initiated lock of this gate until checked by a service technician (432). This prevents the "start scan trigger event" from starting when in the auto mode. If it is determined at 430 that the divert position is not in the automatic divert mode, then it follows that the position is in the service mode and the gate will be allowed to start in subsequent iterations (434). The current iteration (410a) of the state machine ends. For all processing blocks within the flow chart containing the end iteration declaration, this means that the state of the current diverter gate state machine is paused by the program, advanced through the state machines associated with the other gates until all processing is completed, and then finally the interrupt program is exited to wait for the next 250 microsecond interrupt event to occur.

When the gate control state machine 410a changes to the start-scan substate 414, the program maintains this substate 436 for a fixed period of time, e.g., 10ms in the illustrated embodiment. When this state is initiated (duration of the predetermined period), current is supplied to the actuator coil of the gate to effectively drive the gate toward the commutation position (actuation signal 320 of fig. 17 b). It is also contemplated that during this early stage of the start-up scan, the associated gate sensor element 84 will continue to indicate that the gate is within the home position (438). If not, an error flag is set and the diverter gate is not available for future starts (440). However, the current boot will be complete. An unexpected change in the reported state during this early stage of start-up indicates that the gate position sensor is faulty or has a deviation and therefore cannot be trusted. The internal flag is set so that when the predetermined start pulse time is complete (444, 446), control to start scanning will transition to the fixed error recovery timing method (450). Otherwise, at the end of the start pulse, control transitions to using a dynamic gate position feedback method (448).

For each interaction of this sub-state (414), the program enters at point 436 and once each iteration occurs evaluates the gate position status (438) reported by sensor element 84 and the internal timer (442) until it is determined at 442 that the timer has expired, resulting in setting the flag at 444 and setting the internal error flag (446) in the time since the start of the start scan. If the flag is set (450), the state machine advances to use a fixed timing error recovery method (substate 414 d). If not, the state machine advances to use the dynamic gate position feedback method (substate 414 a). In either case, in this embodiment, both transitions result in the control (302) of the gate actuator coil being in a reverse braking mode that will begin the flux dissipation interval 322. This has the effect of slowing down the movement of the gate towards the diverting position.

When the sub-state 414c is initiated (within the dynamic control method sequence of the gate initiation control), the program will begin processing the gate state machine on each iteration 410a at point 484. Beginning with a test whether the delay has expired 486. If so, R.E, (rising edge) the delay after the event is complete (490) and the H-bridge drive circuit 304 of the actuator coil 302 of the commutator gate restarts to provide the hold current 324 (if not done so in process block 480 of FIG. 18 e). The state machine then displays "start scan complete" and transitions to the "commutation position" state for the next iteration (to the main state 416 for the associated commutator gate). If not, then the current sub-state machine is held (414c) for re-evaluation in the next interrupt driven iteration (488).

If the error flag is set during the start-up scan sequence (sub-state 414, 414a or 414b), after setting the appropriate internal error flag and the drive circuitry controlling the diverter gate, the program will transition to the appropriate stage (starting) within the error recovery sub-state 414d to fully recover from the associated error event. When the error recovery sub-state is initiated at each interrupt driven evaluation interval, the routine enters at point 492, then checks the time since the start of the start scan and performs the appropriate action according to the predetermined timing events for the drive circuit control (494) until the start scan is shown to be complete and the state machine finally proceeds to the shift position state (416).

When the start-up scan state 414 is complete, the gate control state machine 410a enters a "commutation position" state 416. When this state is initiated, it is expected that the gate will remain in the commutating position because the hold current 324 should hold the gate in the commutating position against the action of the return spring 332 until such time as the "start gate return scan trigger" event occurs. For this purpose, when the 416 state starts, the program enters at point 495 on each iteration of 410 a. It is then determined (496) whether a "start gate return scan trigger" event has occurred. If not, then a determination is made as to whether the diverter gate position feedback sensor 84 indicates that the gate is at the divert position (497). If so, the program maintains the commutation position state (416) for re-evaluation on subsequent iterations until a return to start event occurs (498).

If it is determined at 497 that the gate position feedback sensor is not reporting a divert position, then an unexpected diverter gate movement has occurred.

The severity of the error report depends on whether the commutation position is in the automatic commutation mode or not (500). If the divert position is set to service mode (504), then the error report is local and the "start gate return scan request" will be initiated by the service personnel manual mode prior to control (which means that service mode is initiated by service personnel). If the commutation position is determined to be in the automatic commutation mode at 500, then a significant event is determined to have occurred (502). An error flag is set, a "start gate return scan request" is issued, and the automatic activation of the gate is locked until reset by an operator or the host system. In either case, if the commutation pattern is determined at 500, the commutation position state is maintained until the "start gate return scan request" is synchronized with the slat position timing for the "start gate return trigger event" to be initiated, and the state machine 410a of the gate is subsequently evaluated. The state machine then proceeds to the return scan state 418.

If it is determined at 496 that a "start gate return sweep trigger" event is initiated, then it is determined whether the gate position feedback sensor 84 indicates that the gate is at the commutation position (506). If not, then it is concluded that an unexpected timing event has occurred and the program cannot consider the output of sensor 84 to be reliable (508). An error flag is set and future start is not available until reset.

If it is determined at 506 that the gate position feedback sensor indicates that the gate is in the commutation position, then the dynamic gate position feedback technique is initiated during the return scan state by setting the internal flag (512). In either case (508, 512), process block 510 will be executed, and the return to scan state 418 begins by initiating a demagnetization pulse (326). Those skilled in the art will recognize that the demagnetization pulse is not strictly required, and that for the beginning of the return scan sequence (e.g., the first 8ms), a regeneration mode may be used instead. The advantage of the demagnetization pulse is that it dissipates the residual magnetic force in the coil core more efficiently than in the regenerative mode. This advantage becomes more pronounced in the shortened return scan effect as the core inductance value and/or size of the selected core 302 becomes larger. However, the demagnetization pulse 326 is optional, and the demagnetization pulse 326 may not be needed for small cores and low inductance values of the coil 302.

In this embodiment, the transition from the commutation position state (416) will always start the return sweep by initiating a demagnetization pulse, thereby transitioning to the sub-state 418 where control of the demagnetization pulse is managed using a fixed timing (time predetermined to maximize performance of the selected coil 302).

When the sub-state demagnetization (418) starts, the program will begin processing at point 512. Then, at each iteration of 410a, evaluation of the feedback sensor element 84 of the diverter gate will begin (514) to confirm that the gate remains within the range of the diverting position (marked portion 86a visible by sensor element 84) for the first 10ms of time since the start of the return scan. If not, a fixed error recovery timing method is marked for use on transitions away from this substate. After evaluation of the feedback sensor, an evaluation of "time since start of return sweep" is made to sequence the drive circuit through its required stages at appropriate time intervals to produce the desired demagnetization pulse (516). The demagnetizer state is held for re-evaluation at subsequent intervals until the 10ms event becomes active; at this point, an internal error flag, which would be set if unexpected gate movement were seen, is used to select between the two sub-state transitions. If gate motion is seen, then it follows that the sensor element 84 cannot be trusted and a fixed return scan error recovery timing must be used (transition to sub-state 418 where the "latency delay from A of the return scan 20 ms" flag is active). Otherwise, the dynamic gate position feedback method is used by transitioning to a wait for a falling edge (F.E.) event from sensor 84.

If the return scan substate 418a is initiated, the program will begin processing the gate state machine at point 518 on each iteration of the commutator gate state machine (410 a). It will then be determined whether a falling edge (F.E.) event of the sensor element 84 has occurred (520). If so, then an f.e. event has occurred within the expected timing window (522), and the dynamic timing sequence may continue by transitioning to the next iteration to wait on a rising edge (R.E.) event (transition to sub-state 418 b). If it is determined at 520 that an f.e. event has not occurred, then a determination is made (524) as to whether the time since the start of the return scan has exceeded the expected f.e. window (20 ms for the illustrated embodiment). If not, the program maintains the current sub-state for re-evaluation on subsequent iterations (526). If it is determined at 524 that the time since the start of the return scan has exceeded the expected f.e. window, then the appropriate error flag is set and the state machine transitions 528 to the fixed return scan error recovery timing sub-state 418 g.

If the return scan substate 418b is initiated, the program will begin processing the gate state machine at point 530 on each iteration of the commutator gate state machine (410 a). It is then determined whether an r.e. event has occurred for sensor element 84 (532). If so, then an R.E. event has occurred within the expected timing window (534), and the dynamic timing sequence can continue by calculating a velocity associated with the gate motion, the velocity being inversely proportional to the (R.E. -F.E.) event timing relative to the start of the return scan. A determination is then made as to whether the gate speed is fast enough to require a brake signal 330 to provide deceleration (536). If it is determined at 536 that additional deceleration is required, a 1.5ms delay is initiated and the width of the reverse pulse (counter pulse) is calculated in inverse proportion to the gate return speed previously calculated (540). The state machine then transitions to the management hold control sequence (to sub-state 418c to wait for the 1.5ms delay to expire). If it is determined at 536 that the gate is moving slowly enough that the braking signal is not needed, then the H-bridge drive circuit is ready to transition from reverse braking mode to regeneration mode (538). This is done by transitioning to the sub-state 418e for the next iteration of 410 a. If it is determined at 532 that an r.e. event has not occurred, then a determination is made at 542 as to whether the time since the start of the return scan has exceeded the expected r.e. window (30 ms for the illustrated embodiment). If not, the program maintains the current sub-state for re-evaluation on subsequent iterations of 410a (544). If it is determined at 542 that the time since the start of the return scan has exceeded the expected r.e. window, then the gate return motion is shown to be outside of acceptable limits and a significant error has occurred (546). The appropriate error flag is set and the state machine transitions to a fixed return scan error recovery timing substate (to substate 418g) with no brake signal applied.

If the return scan substate 418c is initiated, the program will begin processing the gate state machine at point 550 on each iteration of the commutator gate state machine (410 a). The associated delay will be reduced after the r.e. event is counted down by the interrupt interval time (552) and then it is determined whether the delay has expired (554). If not, then the current sub-state is maintained for re-evaluation over subsequent intervals of 410a until the timer expires (556). If it is determined at 554 that the delay has expired, then the H-bridge driver circuit 340 powers up to generate the inversion pulse 330 and transitions to the sub-state (558) awaiting expiration of the timing controlling the width of the inversion pulse (transition to sub-state 418 d).

If the return scan substate 418d is initiated, the program will begin processing the gate state machine at point 560 on each iteration of the commutator gate state machine (410 a). The associated reverse pulse width countdown will be decremented by the interrupt interval time (562), and a determination is then made as to whether the pulse width time has expired (564). If not, the current sub-state is maintained for re-evaluation at subsequent intervals of 410a until the timer expires (566). If it is determined at 564 that the pulse width timer has expired, then the H-bridge drive circuit 340 is in reverse braking mode to slightly oppose the return action of the spring and complete critical damping of the gate motion (568). A short delay is initiated to allow the gate to physically complete the return to the "home" position. The state machine transitions to sub-state 418f to wait for this short delay (3 ms in the illustrated embodiment) to expire.

If at 438 it is determined that a brake signal is not required, sub-state 418e is enabled for administrative tasks to place H-bridge driver circuit 304 in an off mode. This is a sub-state of a single iteration, so that a 250 microsecond delay (570) will result before the H-bridge control management is performed and a delay such as 3ms is initiated to provide sufficient physical time (572) for the gate to reach the "home" position. The delay countdown is initiated by block 572 and ends with the transition to the substate 418f waiting for the delay to expire.

If the return scan substate 418f is initiated, the program will begin processing the gate state machine at point 580 on each iteration of the diverter gate state machine (410 a). The associated delay time will then be decremented by the interrupt interval time (582) and a determination is then made whether the delay time has expired (584). If not, the current sub-state is maintained for re-evaluation over subsequent intervals of 410a until the time count expires (586). If the delay is determined to have expired at 584, then the H-bridge driver circuit 340 is in the OFF mode, internally managed, and displays return scan complete (588). The state machine transitions to the "home" position state of 412.

If an error is detected during the return scan sub-state (418, 418a.. 418c), the state machine should transition to the error recovery sub-state 418 g. When this sub-state starts, the program will begin processing the gate state machine at point 590 on each iteration of the diverter gate state machine (410 a). A related fixed timing event will then be performed to control the H-bridge drive circuit to complete the return scan (592). Once the "time since start of return scan" evaluates to 32ms, it is indicated that the return scan is complete and the associated management is performed and the state machine transitions to the "original" non-commutation state of 412, in which the error signal 334 is active.

It can thus be seen that the routine 400 is stably implemented through critical damping of the movement of the gate 72 during actuation by the activation control signal. The activation control signal includes a flux dissipation period 322, the flux dissipation period 322 allowing the biasing spring 332 to apply a braking force to the gate after a predetermined time of application of the actuation signal 320. The program then monitors the digital feedback from the gate position sensor 84. The time delay within the expected timing window between the first falling edge (F.E.) and the rising edge (R.E.) of the signal generated by proximity sensor 84 detecting markers 86a, 86b is used to determine the relative rotational speed of the gate activation scan to dynamically determine when to apply the gate hold signal 324 to provide critical damping to the mechanical activation response. For the case of return sweep, return control signal 325 includes applying a brake signal 330 to decelerate the motion of the gate, as is accomplished by the action of biasing device 332. Again, the time measurements of the falling and rising edges of the signal generated by the gate sensor 84 occurring within the expected timing window are used to determine the relative velocity of the gate during the return scan. This timing measurement is used to determine the time offset and duration of the brake signal 330 to provide critical damping for mechanical control of the gate. In addition, during the beginning of the return scan phase, an optional demagnetization pulse 326 can be used to quickly remove any residual flux within the inductive core of the actuator. This translates into an improved response at the beginning of the gate return scan.

Monitoring of the rising and falling edges of the gate position sensor 84 can also be used to determine the overall operability of the gate movement. This information can be used to detect any degradation in performance and statistically determine whether preventative maintenance is required before the commutator actually fails. At a higher level of system control, this information can be used to determine the maximum speed at which sorting can be performed by the sorter 30, or to cause the relevant sorting destination's lane to be shut down until maintenance is complete.

In the illustrated embodiment, the actuator 76 is a slightly modified version of a commercially available brushless torque actuator of the Model DTA-5 series sold by Sala-Burgess, Inc. However, other forms of rotary solenoids may be used.

Also, certain aspects of the disclosed embodiments may use other forms of actuators. For example, although the figures illustrate the use of a rotary actuator that turns a gate to change states, the actuation system 300 and the divert control routine 400 can use other forms of actuators, such as a linear actuator that moves in a straight line between two states. Other forms of actuation may also be used in certain aspects, such as pneumatic actuation, hydraulic actuation, and the like. Also, the actuator may be used for other control operations than moving the diverter gate by a sweeping motion, and may be used in other applications than sorters. While the sensor 84 monitors portions of the gate to determine movement of the gate, it should be understood that various encoders may be positioned on the gate shaft, the actuator shaft, etc.

Commutator 43 may be used in commutator assembly 44 as a redundant commutator 48 in combination with another commutator 46, such as an electromagnetic commutator (fig. 20 and 21). Each redundant diverter 46, 48 is capable of selectively diverting one or more diverting members 39 from non-diverting path 40 to an associated diverting rail 42.

In the illustrated embodiment, the first redundant diverter 46 is a magnetic diverter that utilizes magnetic force to at least partially divert the diverting member 39 in a diverting state from the non-diverting path 40 to the associated diverting rail 42. An example of such a magnetic commutator that utilizes only magnetic forces is disclosed in U.S. patent No.5,409,095, the disclosure of which is incorporated herein by reference. An example of such a magnetic commutator that is magnetically actuated but mechanically accomplishes commutation is disclosed in commonly assigned U.S. patent No.6,615,972, the disclosure of which is incorporated herein by reference.

An advantage of incorporating a redundant diverter for diverter assembly 44 is that if the diversion is performed magnetically by first redundant diverter 46, the diversion can be quieter because there is minimal impact between diverting member 39 and diverter 46. However, if for any reason the first redundant diverter 46 is not capable of diverting, then the second redundant diverter 48 may be used to divert the diverting members. This may be particularly useful in situations where increased friction between the push slide 38 and the slats 36 may make reversal of the push slide difficult to initiate. In the illustrated embodiment, the first and second redundant diverters 46, 48 are actuated for each commutation, as will be described in more detail below. However, those skilled in the art will appreciate that the second redundant commutator may only be actuated if the first redundant commutator fails to make the desired commutation.

The electronic commutation controller 56 can have a first drive circuit 304 that selectively actuates the first redundant commutator 48 and a second drive circuit 304 that selectively actuates the second redundant commutator 48. In one embodiment, the first and second drive circuits operate together to ensure that if commutator 46 is unable to commutate, then commutator 48 will commutate. In another embodiment, the first driver circuit 304 may operate as a master controller and the second driver circuit 304 may operate as a slave controller responsive to the operation of the first driver circuit. In this embodiment, the first drive circuit will respond to a signal from the slat sensor 61a and/or the pin sensor 61b initiating commutation, and a signal from a commutation sensor (not shown) indicating that commutation is occurring. In this embodiment, if the first drive circuit shows that no commutation has occurred, the second drive circuit, which is responsive to the first drive circuit, performs commutation. In this way, the second redundant commutator 48 is only activated when the first redundant commutator 48 fails. Thus, in either embodiment, the diverter assembly 44 operates very reliably.

In an alternative embodiment, the positive displacement sorter 130 includes a diverter module 150 comprised of a plurality of diverter assemblies 144, the diverter assemblies 144 having a first redundant diverter 146 and a second redundant diverter 148 (fig. 22-29). The second redundant diverter 148 may be in the form of a mechanical diverter 170 having a rotary actuator 176, the rotary actuator 176 having a generally horizontally oriented shaft (fig. 22-29). In particular, the rotary actuator 176 has a transversely oriented shaft 196, the shaft 196 being generally perpendicular to the movement of the belt (not shown) of the sorter 130. It should be understood that while shown as a redundant commutator, the mechanical commutator 170 may be used as a stand-alone commutator in the manner previously described.

The mechanical diverter 170 includes a gate 72, the gate 72 being rotatable between a non-diverting orientation shown in fig. 26 and 28 and a diverting orientation shown in fig. 27 and 29. The gate 172 defines a diverting surface 174, the diverting surface 174 diverting the diverting member 39 when in the diverting orientation. The diverter 170 may also include a slip joint 180 in the form of an elongated slot, and a paddle in the slot that allows relative movement of the gate 172 with respect to the shaft of the rotary actuator 176. The gate 172 is configured to position the diverting surface 174 to engage the bearing 52 of the diverting member 39 when in the diverting orientation. Thus, in a manner similar to the mechanical diverter 70, the diverter 170 can divert the rotatable body, thereby reducing wear on the diverting surface 174.

In another alternative embodiment, the positive displacement sorter 230 includes a diverter module 250 made up of a plurality of diverter assemblies 244, each diverter assembly 244 having a first redundant diverter 246 and a second redundant diverter 248 (fig. 30-36). The second redundant diverter 248 may be in the form of a mechanical diverter 270 having a gate 272 and a rotary actuator 276, the rotary actuator 276 having a generally horizontal axis that is angled with respect to the longitudinal and transverse directions of the sorter. In particular, the rotary actuator 276 has a shaft 296, the shaft 296 being angled with respect to the movement of the belt (not shown) of the sorter 230. It should be understood that while shown as a redundant commutator, mechanical commutator 270 may be used as a stand-alone commutator.

The mechanical diverter 270 includes a gate 272 that is rotatable between a non-diverting orientation, shown in fig. 30 and 32, and a diverting orientation, shown in fig. 31 and 33. The gate 272 defines a diverting surface 274 that diverts the diverting member 39 when in the diverting orientation. Diverter 270 may also include a slip joint 280 similar in construction to slip joint 80. The gate 272 is configured to position the diverting surface 274 to engage the pin 54 of the diverting member 39 when in the diverting orientation.

As seen in fig. 37, the brushless torque actuator 78 includes a rotor 100 that is rotated by electrical energy applied to coils 102, and includes an internal biasing device 332 (not shown in fig. 37).

Changes and modifications in the specifically described embodiments of the invention may be carried out without departing from the principles of the invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.

Claims (18)

1. A positive displacement sorter comprising:

a plurality of interconnected parallel slats defining an endless belt traveling in a longitudinal direction, an upper surface of said belt defining an article-conveying surface;

a plurality of pusher shoes, each said shoe traveling along at least one said slat to laterally divert an article on said conveying surface, each said shoe having a diverting member extending below said conveying surface, wherein said diverting member includes a rotational bearing and a pin extending below said bearing;

a plurality of diverting rails below the conveying surface, each diverting rail being engageable with the diverting member to cause the associated shoe to travel laterally to divert an article;

a plurality of diverters, each for selectively diverting at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails in a diverting state;

at least one of the diverters includes a gate having a diverting surface selectively rotatable about a generally horizontal axis between a diverting state and a non-diverting state, wherein the gate is positioned on the diverting surface to engage the bearing in the diverting state; and

an actuator to move the gate between the non-diverting state and the diverting state, the actuator comprising an electrically operated rotary actuator that is rotatable about another generally horizontal axis of rotation.

2. The positive displacement sorter as claimed in claim 1 wherein said rotary actuator comprises one selected from the group consisting of a rotary solenoid and a brushless torque actuator.

3. The positive displacement sorter as claimed in claim 1 wherein said generally horizontal axis is generally concentric with said another horizontal axis of rotation.

4. The positive displacement sorter as claimed in claim 3 including a slip joint between said rotary actuator and said gate, said slip joint resisting reversing motion transmitted from said gate to said rotary actuator.

5. A positive displacement sorter as claimed in any of the preceding claims including a sensor which monitors operation of the diverter.

6. The positive displacement sorter as claimed in claim 5 wherein said sensor detects at least one selected from the diverting state of said gate and the non-diverting state of said gate.

7. The positive displacement sorter as claimed in claim 6 including an electronic divert controller applying an activation control signal to said actuator to operate said gate between one state and another, wherein said controller monitors said sensor and adjusts the activation control signal applied to said actuator in accordance with movement of said gate.

8. The positive displacement sorter as claimed in claim 7 wherein said controller adjusts the activation control signal applied to said actuator to provide critical damping of movement of said gate between said one of the states and said another of the states.

9. The positive displacement sorter as claimed in claim 7 wherein said gate includes a mechanical biasing device tending to return said gate to said one state and wherein said controller provides a return control signal when said gate is moved to said one state, said return control signal counteracting said biasing device.

10. The positive displacement sorter as claimed in claim 9 wherein said controller adjusts the return control signal in accordance with movement of said gate.

11. The positive displacement sorter as claimed in claim 10 wherein said controller adjusts the return control signal to provide critical damping of movement of said gate between said other state and said one state.

12. The positive displacement sorter as claimed in claim 1 wherein said gate includes a flexible member defining said diverting surface, said flexible member adapted to absorb impact due to contact between said diverting member and said diverting surface.

13. The positive displacement sorter as claimed in claim 1 wherein said diverting surface comprises a curved surface.

14. The positive displacement sorter as claimed in claim 1 wherein said generally horizontal axis is oriented at least partially in the longitudinal direction.

15. The positive displacement sorter as claimed in claim 1 wherein said generally horizontal axis is oriented at least partially in the transverse direction.

16. The positive displacement sorter as claimed in claim 1 including a slip joint between said gate and said actuator to reduce the transmission of forces applied to said diverting surface to said actuator.

17. A sorter diverter adapted to selectively divert at least one of a plurality of pusher shoes, each of said shoes traveling along at least one of a plurality of slats to laterally divert articles on a conveying surface defined by said slats, each of said shoes having a diverting member extending below said conveying surface, wherein said diverting member includes a rotational bearing and a pin extending below said bearing, said diverter comprising:

a gate having a commutating surface selectively rotatable about a generally horizontal axis between a commutating condition and a non-commutating condition, wherein the gate is positioned on the commutating surface to engage the bearing in the commutating condition; and

an actuator to move the gate between the non-diverting state and the diverting state, the actuator comprising an electrically operated rotary actuator that is rotatable about another generally horizontal axis of rotation.

18. A method of diverting articles using a positive displacement sorter having a plurality of interconnected parallel slats defining an endless belt traveling in a longitudinal direction, an upper surface of the belt defining an article conveying surface; and a plurality of pusher shoes, each said shoe traveling along at least one said slat to laterally divert articles on said conveying surface, each said shoe having a diverting member extending below said conveying surface, wherein said diverting member includes a rotational bearing and a pin extending below said bearing;

said sorter also having a plurality of diverting rails below said conveying surface, each of said diverting rails being engageable with said diverting member to cause lateral travel of the associated shoe to divert an article; and a plurality of diverters, each for selectively diverting at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails in a diverting state, wherein the method comprises:

at least one of the diverters having a gate with a diverting surface selectively rotatable about a generally horizontal axis between a diverting state and a non-diverting state, wherein the gate is positioned on the diverting surface to engage the bearing in the diverting state; and is

The gate is selectively moved between the commutating and non-commutating states by a rotary actuator that is electrically powered to rotate about another generally horizontal axis of rotation.