HK1178503B - Method of controlling an accumulation conveyor - Google Patents

Description

Method for controlling accumulation conveyor

Background

This application claims priority from U.S. provisional patent application (serial No.: 61/210750), filed 3, 19, 2009, the contents of which are incorporated herein by reference.

The present invention relates generally to conveyors and, more particularly, to accumulation conveyors (accumulation conveyors). The present invention will be disclosed with respect to, but not necessarily limited to, a zoned accumulation conveyor that includes a control module configured to control two zones that monitor and control product flow on the accumulation conveyor.

Disclosure of Invention

According to the present invention there is provided a method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone and a second zone, the second zone being downstream of the first zone, the method comprising the steps of: a. determining whether the second area is occupied by a second item; setting the first zone to an inactive state if it is determined that the second zone is occupied by the second item.

According to the present invention, there is provided a method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone, a second zone and a third zone, the second zone being downstream of the first zone, the third zone being downstream of the second zone, the method comprising the steps of: a. determining whether the second area is occupied by a second item and whether the third area is occupied by a third item; setting the first zone to an inactive state if it is determined that the second zone is occupied by the second item and it is determined that the third zone is occupied by the third item.

According to the present invention there is provided a method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone and a second zone, the second zone being downstream of the first zone, the method comprising the steps of: a. determining whether the second area is occupied by a second item; b. determining whether the first area is occupied by a first item; setting the first zone to an inactive state if it is determined that the first zone and the second zone are occupied.

According to the present invention, there is provided a method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone, a second zone and a third zone, the second zone being downstream of the first zone, the third zone being downstream of the second zone, the method comprising the steps of: a. determining whether the second area is occupied by a second item and whether the third area is occupied by a third item; b. determining whether the first area is occupied by a first item; setting the first zone to an inactive state if it is determined that the first zone, the second zone, and the third zone are occupied.

According to the present invention there is provided a method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, the plurality of zones comprising at least a first zone and a second zone, the second zone being downstream of the first zone, the method comprising the steps of: a. determining whether an item is at a predetermined location in the first region; b. determining whether the second area is in a congested state; c. determining whether the first region has been in a stacked state for at least a predetermined length of time; if it is determined that an article is at the predetermined location in the first zone, the second zone is in a crowded state, and the first zone has been in a stacked state for at least a predetermined length of time, i.e. activating the first zone for a first predetermined length of time; deactivating the first region.

According to the present invention there is provided a method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, the plurality of zones comprising at least a first zone, a second zone and a third zone, the second zone being downstream of the first zone, the third zone being upstream of the first zone, the method comprising the steps of: a. determining whether the first area is occupied by a first item; b. determining whether the first region is in an active state; c. determining whether the second area is occupied by a second item; d. determining whether the second region is in an active state; e. determining whether the third item has been at a third predetermined location in the third zone for at least a first predetermined length of time; if it is determined that the first zone is occupied, it is determined that the first zone is in an active state, it is determined that the second zone is not occupied, it is determined that the second zone is in an active state, and it is determined that the third item is at the third predetermined location in the third zone for at least the first predetermined length of time, then the third zone is controlled based on a condition of the second zone.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

Fig. 1 is a plan view of an accumulation conveyor embodying one or more teachings of the present invention.

FIGS. 2-5 are schematic side views showing different configurations of zone control modules and interface modules.

Fig. 6A, 6B, 6C show control logic for the coast to stop (stack) accumulation mode.

Fig. 7A to 7V are schematic regions showing the operation (operation) of the accumulation conveyor in the slide stop accumulation mode.

Fig. 8A, 8B, and 8C illustrate control logic for a stack mode with sensor-coupled slide stops.

Fig. 9A to 9L6 are schematic regions showing the operation of the stacking conveyor in the stacking mode in which the sliding of the sensor coupled is stopped.

Fig. 10A, 10B, 10C show control logic for run up (run up once) pile-up mode.

Fig. 11A to 11I are schematic regions showing the operation of the accumulation conveyor in the one-run-up accumulation mode.

Fig. 12A, 12B, 12C show control logic for a run-up pile-up mode coupled with sensors.

Fig. 13A to 13G are schematic regions showing the operation of the stacking conveyor in the one-run-up stacking mode with the sensor coupled.

Fig. 14 shows a control logic for congestion processing (generating).

FIG. 15 illustrates the control logic steps of the control logic shown in FIG. 14.

Fig. 16 illustrates an alternative embodiment of a portion of the control logic shown in fig. 14 and 15.

Fig. 17 shows the control logic associated with "waking up" a sleep zone.

Fig. 18 illustrates flow and occlusion detection control logic.

Reference will now be made in detail to the preferred exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Detailed Description

In the description below, like reference numerals designate like or corresponding parts throughout the several views. Also, in the following description, it is to be understood that terms such as front, rear, inside, outside, and the like are words of convenience and should not be construed as limiting terms. The terminology used in this patent is not meant to be limiting, as the devices described herein, or portions thereof, may be fixed or utilized in other orientations. Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

Referring to fig. 1, a plan view of an accumulation conveyor embodying one or more teachings of the present invention is shown. The accumulation conveyor, generally indicated at 2, comprises a plurality of individually controllable zones 4a, 4b, 6a, 6b, 8a, 8b, 10a, 10b and 12 a. Although nine regions are present in the embodiment shown in fig. 1, the present invention is not limited to nine regions. In the illustrated embodiment, the area is typically six feet long, twice as long as a typical accumulation conveyor area, resulting in a reduction in manufacturing costs. It will be appreciated that the present invention provides for efficient packing of packages even if the area is longer than typical. However, the present invention is not limited to long areas, nor to six foot long areas.

The zones are selectively driven in any suitable manner known in the art such as the drive arrangement shown in U.S. patent No.6889822, the contents of which are incorporated herein by reference. In the illustrated embodiment, each zone of the accumulation conveyor 2 contains a plurality of conveyor rollers (shown schematically) that can be selectively driven by pressing an underlying drive belt (not shown) against the conveyor rollers using a pneumatic actuator (not shown). In the illustrated embodiment, each module 4c, 6c, 8c, 10c and 12c is configured as a pneumatic actuator (not shown) that controls their associated zone and is therefore connected to a pneumatic source. The modules 4c, 6c, 8c, 10c and 12c may be pneumatically daisy chained (i.e., daisy chained) together. Other drive configurations include monitored drive rollers having modules 4c, 6c, 8c, 10c and 12c appropriately configured for them.

In the illustrated embodiment, each pair of zones has a corresponding zone control module 4c, 6c, 8c, and 10 c. Zone control modules 4c, 6c, 8c and 10c control two zones, respectively, while zone interface module 12c controls zone 12a, which zone 12a is the discharge zone to take-away conveyor 14, which in the illustrated embodiment is shown as a drop belt.

Each zone 4a, 4b, 6a, 6b, 8a, 8b, 10a, 10b and 12a contains a respective sensor 4d, 4e, 6d, 6e, 8d, 8e, 10d and 10e and 12d connected to the modules of the respective zone. Although any suitable sensor, such as a roller sensor or a diffusion scan sensor, may be used, in the illustrated embodiment the sensor is a photographic eye having a respective reflector. The location and orientation of the sensor, also referred to herein as the camera eye, within the area is selected based on system parameters such as the length or type of package.

FIGS. 2-5 schematically illustrate different configurations of zone control modules and interface modules. Referring to fig. 2, a configuration similar to the accumulation conveyor 2 of fig. 1 is shown, in which there are Z (n +2) zones represented by the schematically illustrated conveyors 16a, 16b, 18a, 18b and 20 a. The zone control modules 16c and 18c are arranged to control pairs of conveyors forming respective zones. The zone interface module 20c is arranged to control the conveyor 20a as a discharge zone, so that the zone interface module 20c is a discharge interface module.

The system acts through RS232 communication between the zone control modules 16c, 18c and the interface module 20c, as indicated by the lines therebetween in fig. 2. The zone control modules 16c and 18c are each configured to receive information from a respective sensor (not shown in fig. 2-4) of each of the two zones each controlled by a single control module to detect products in the respective zone, to control movement of products within each of the two zones (in the illustrated embodiment, pneumatically), and to allow zone information to be distributed between the modules.

The only difference in that the interface module 20c is configured to control a single zone in the manner discussed above with respect to the zone control module is limited to controlling a single zone. The interface module 20c also controls the direction of travel of the transmitter by using DIP switches. (zone controls 16c and 18c do have a default direction of travel). The interface module 20c is also configured to use separate I/O to allow control of the movement of product on the accumulation conveyor, to allow an external system to monitor the fill status of the conveyor and to allow an external system to monitor fault conditions. I/O from/to external devices is shown at 22.

Fig. 2 illustrates the use of an interface module 20c as a drain interface module by controlling a single area at the drain. Fig. 3 differs from fig. 2 in that instead of a discharge conveyor, an interface module 30c is provided to control the feed conveyor 24 a. The interface module 30c is designated as a feed interface module, thereby performing the same function as the discharge interface module 20 c.

Although the accumulation conveyor can be configured without an interface module, the embodiment shown here has an interface module. The determination of whether to have a feed or discharge interface module depends primarily on practical considerations, such as convenience, minimizing wiring, which end of the conveyor is desired to have an interface with the wire, and so forth.

Fig. 2 and 3 show a stacking conveyor with an odd number of zones, each with one interface module 20c or 30 c. Fig. 4 shows an accumulation conveyor having an even number of zones using two interface modules, a feed interface module 38c and a discharge interface module 44c, each configured as described previously.

Fig. 5 shows an accumulation conveyor that does not restrict the direction of product flow based on physical configuration. The system includes an intermediate module 58 that is configured to use separate I/O to allow control of movement of product on the accumulation conveyor, allow external systems to monitor the fill status of the conveyor, and allow external systems to monitor fault conditions without controlling the conveyor or zone. The intermediate module 58 is simply an I/O operator for external system requirements. Regardless of the upstream or downstream device, but when information is communicated to it, it will adjust the message according to its local I/O settings and send the adjusted message to its neighbors in the required communication flow direction. Any number of intermediate modules may be used in any location within the zone control module string.

Also shown in fig. 5 are optional feed interface modules 50c and optional discharge interface modules 52c, although it is preferred that each accumulation conveyor have at least one of either.

A stacking conveyor constructed in accordance with the teachings of the present invention operates in a stacking mode unless there is a release signal from an external source, such as a PLC. The present invention contemplates four basic stacking patterns: stopping sliding; a slide stop-sensor coupling; running at one time; and a run-sensor coupling. The pile-up pattern is determined by the position of the DIP switch on the interface module or the middle module.

Within the teachings of the present invention, a typical feed configuration for a nominal area six feet long comprises:

3' feed idler with interface module only (idler)

3' feed idler (slave) without any control module

6' feed idler with interface module only

6 'feed idler with zone control Module (two 3' zones)

9 ' feed idler with zone control Module (one 6 ' zone, one feed 3 ' zone)

9 'feed idler with zone control module and interface module (three 3' zones with interface on feed)

12 'feed idler with zone control Module (two 6' zones)

12 ' feed idler with zone control module and interface module (two 3 ' zones with interface on feed, then 6 ' zone)

Within the teachings of the present invention, a typical discharge configuration for a nominal six foot area comprises:

3' evacuation idler with interface module only

3' exhaust idler (slave) without any control module

6 'evacuation idler with interface Module only (6' Release area)

6 'exhaust idler with zone control Module (3' Release zone)

Referring to fig. 6A, 6B, and 6C, the same control logic representing the slide stop deposition mode, which is the deposition mode with the minimum advancement (aggregate), is shown. Unless there is a release command, the most downstream zone of the system (i.e., the discharge zone) will be inactive in the slip stop mode. The control logic is executed independently by each module of each zone being controlled. The difference between fig. 6A, 6B and 6C is the illustrated path after execution of the control logic. In step 62, it is determined whether the accumulation conveyor is in a slip stop mode. If not, the logic proceeds to step 64 where the other pile-up patterns are checked at step 64. If the slip stop mode is active, the logic proceeds to step 66 where it is determined if the downstream sensor is occupied.

As used herein, a sensor is considered occupied when the sensor is blocked and the time delay period expires. When the sensor is clear (not blocked) and the time delay period expires, the sensor is deemed unoccupied. The sensor time delay period is set by the DIP switch position on the most downstream interface module. The time delay period set by the DIP switch is applied to all modules in the string and their corresponding sensors. While the time delay period for determining to be occupied may be different from the time delay period for determining to be clear, this is not the case in one embodiment. In one embodiment, the DIP switch allows the delay to be set to zero, 0.75 seconds, 1.0 seconds, or 1.5 seconds.

If the downstream region is not occupied, then the control logic proceeds to step 68 as indicated by the thick solid line in FIG. 6A. At step 68, the local region (i.e., the region being examined) is set to active and control logic proceeds to step 70 where the local region is set to no pile-up at step 70. From here, the control logic returns to step 62. As used herein, active means that the conveyor or area is moving.

If the downstream region is occupied at step 66, control logic proceeds to step 72 where the local region is set to inactive at step 72. As used herein, inactive means that the conveyor or zone does not move. The control logic proceeds to step 74 where it is determined whether the local area sensor is occupied 74. If not, the logic proceeds to step 70 where the local region is set to no pile-up, which is the path indicated by the thick solid line in FIG. 6B. As used herein, no pile-up means that a particular region is inactive or its region sensor is clear. As used herein, when the output of the sensor is in a state consistent with seeing the reflector, the sensor is clear, meaning that the product is not directly detected by the local area sensor (no time delay-it is the actual sensor state). If the local area sensor is occupied in step 74, then the control logic proceeds to step 76 where the local area is set to be stacked (the course indicated by the thick solid line of FIG. 6C) at step 76. As used herein, pile-up means that the local area is inactive and the local area sensor is blocked. As used herein, when the output of the sensor is in a state consistent with the reflector not being visible, the sensor is blocked, meaning that the product is directly detected by the local area sensor (without a time delay-it is the actual sensor state).

Referring to fig. 7A to 7V, an example of the operation of the slip stop accumulation control logic is shown in a series of figures. 7A-7V each show regions 1-6, labeled only 78, 80, 82, 84, 86, and 88 in FIG. 7A, with sensors 78a, 80a, 82a, 84a, 86a, and 88a, respectively. Zone 1 is controlled by the feed interface module 90, zones 2 and 3 are controlled by the zone control module 92, zones 4 and 5 are controlled by the zone control module 94, and zone 6 is controlled by the discharge interface module 96. As mentioned above, in the slide stop pile mode, the region 6 is inactive until such time as a release command is received from an external system.

Fig. 7A and 7B show package 1 entering zone 1 and passing sensor 78 a. Fig. 7C shows package 1 being delivered to zone 2. In fig. 7D, sensor 80a becomes occupied by package 1 stopping zone 1, while zone 2 remains active. In fig. 7E, package 1 is delivered to zone 3 and zone 1 becomes active again. In fig. 7F, sensor 82a is occupied and zone 2 stops. Fig. 7G shows package 1 being delivered to zone 4, while zone 2 is active because sensor 82a is not occupied. In fig. 7H, sensor 84a is occupied by package 1, stopping zone 3. Fig. 7I shows package 1 being delivered to zone 5, while sensor 84a becomes unoccupied and zone 3 is activated. Fig. 7J shows sensor 86a becoming occupied by package 1, stopping zone 4. Fig. 7K shows package 1 being delivered to zone 6 so that sensor 86a is no longer occupied and zone 4 is activated. Fig. 7L shows package 1 sliding stopped due to zone 6 being inactive and causing sensor 88a to become occupied thereby stopping zone 5.

Fig. 7M shows a package 2 advancing along the conveyor substantially the same as package 1, having slid to a stop and blocking the camera eye 86a of zone 5, thereby deactivating zone 3. Fig. 7N shows packages 3 and 4 coming close together into the accumulation conveyor. Referring to fig. 7O, the sensor 78a of zone 1 becomes occupied, but no transmitter zone is affected thereby. Fig. 7P shows that sensor 80a of zone 2 has just become occupied by parcel 3, causing zone 1 to stop being driven, thereby stopping parcel 4. Fig. 7Q shows the gap formed between parcels 3 and 4 as parcel 3 continues to move past sensor 80 a. In fig. 7R, sensor 80a becomes unoccupied, causing zone 1 to activate and move package 4. In fig. 7S, sensor 82a of zone 3 is occupied by parcel 3, stopping zone 2, so that the gap between parcels 3 and 4 becomes larger. Fig. 7T shows package 3 delivered to zone 4 stopped as a result of sensor 86a of zone 5 being blocked by package 2. In fig. 7T, sensor 82a is not occupied, thereby again activating zone 2 and moving package 4 forward.

Fig. 7U shows a slide-stopped package 3 occupying sensor 84, causing zone 3 to become inactive. Thus, when parcel 4 reaches zone 3 as shown in fig. 7V, parcel 4 slides to a stop, stopping blocking camera eye 82a and causing zone 2 to be inactive.

Referring to fig. 8A, 8B and 8C, the same control logic representing a stacking mode of sensor-coupled slide stop is shown, respectively. Unless there is a release command, the most downstream zone of the system (i.e., the discharge zone) will be inactive. The second most downstream region will use simple slide stop logic. For each region thus controlled, the control logic is executed independently by each module. The difference between fig. 8A, 8B and 8C is the illustrated path after execution of the control logic.

In step 98, it is determined whether the accumulation conveyor is in a sensor-coupled slip-stop mode. If not, the logic proceeds to step 100 where the other stacking patterns are checked at step 100. If the mode of sensor-coupled slide stop is active, the logic proceeds to step 102 and step 102 determines if both downstream zone sensors are occupied. If both downstream zone sensors are not occupied, the control logic proceeds to step 104 as indicated by the thick solid line in FIG. 8A. At step 104, the local region (i.e., the region being examined) is set to active and the control logic proceeds to step 106 where the local region is set to no pile-up at step 106. From here, the control logic returns to step 98.

If both downstream zone sensors are occupied at step 102, then the control logic proceeds to step 108 where the local zone is set to inactive at step 108. The control logic proceeds to step 110 where it is determined whether the local area sensor is occupied 110. If not, the logic proceeds to step 106 where the local region is set to no pile-up, which is the path represented by the thick solid line of FIG. 8B. If the local area sensor is occupied at step 110, then the control logic proceeds to step 112 where the local area is set to piled up at step 112, which is the path represented by the thick solid line of FIG. 8C.

Referring to fig. 9A to 9L, a series of diagrams show an example of the operation of the slip stop sensor-coupled stacking mode control logic. 9A-9L show regions 1-6, labeled only 114, 116, 118, 120, 122, and 124 in FIG. 9A, having sensors 114a, 116a, 118a, 120a, 122a, and 124a, respectively. Zone 1 is controlled by the feed interface module 126, zones 2 and 3 are controlled by the zone control module 128, zones 4 and 5 are controlled by the zone control module 130, and zone 6 is controlled by the discharge interface module 132. As mentioned above, in the sliding stop-sensor coupled accumulation mode, zones 5 and 6 are inactive until such time as a release command is received from an external system.

In fig. 9A, package 1 advances and the slide stops, occupying sensor 124 a. Packages 2 and 3 are about to arrive with a gap in between. In fig. 9B, package 2 occupies sensor 114a, but no area is made inactive. In fig. 9C, package 2 is delivered to zone 2 as package 3 enters zone 1. In step 9D, package 2 occupies sensor 116a, but zone 1 remains active because sensor 118 of zone 3 is not occupied. Package 3 is occupying sensor 114 a. Fig. 9E shows packages 2 and 3 being delivered to the next series of zones. In fig. 9F, package 2 is occupying sensor 118a of zone 3 and package 3 is occupying sensor 116a of zone 2, which causes zone 1 to stop so that there is no effect in the example shown. Fig. 9G shows packages 2 and 3 being delivered to zones 4 and 3, respectively, so as to no longer occupy the sensors and cause zone 1 to become active.

Fig. 9H shows occupancy sensor 120a without affecting the stacked package 2. Fig. 9I shows packages 2 and 3 occupying sensors 120a and 118a, respectively, thereby deactivating zone 2. Package 2 is being transported to inactive zone 5. Fig. 9J shows package 2 having advanced far enough to no longer occupy zone 4, allowing zone 2 to become active, upon delivery to inactive zone 5, sensor 120 a. Fig. 9K shows package 2 occupying sensor 122a, sliding stopped in zone 5. Zone 3 is deactivated by camera eye 124a being blocked by parcel 1 and camera eye 122a being blocked by parcel 2, resulting in parcel 3 sliding (coast) in zone 4. Fig. 9L shows that packages 1 and 2 have not moved further, and that package 3 has slid to a stop to occupy sensor 120a, thereby causing area 3, which is no longer occupied, to be active.

One-run-up accumulation mode compensation (compensate for) long slip stop buffer between sensors when using an area longer than three feet that operates in a slip stop mode where there is no braking force applied to stop the crate (carton). This control strategy is implemented by allowing parcels in a local area to be driven all the way to the sensors in that area (i.e., run off the local area sensors) before eliminating the drive in the local area. Referring to fig. 10A, 10B and 10C, the same control logic representing a one-run-up pile-up mode is shown, respectively. Unless a release command is received from an external system, the most downstream region of the system (i.e., the drain region) will be inactive in the one-run-up mode. For each region thus controlled, the control logic is executed independently by each module. The difference between fig. 10A, 10B and 10C is the illustrated path after the control logic is executed.

In step 134, it is determined whether the accumulation conveyor is in a run-up mode. If not, the logic proceeds to step 136 where the logic checks for additional stacking patterns at step 136. If the one-run-up mode is active, the logic proceeds to step 138 and step 138 determines if the sensors of the immediately downstream zone are occupied. If the downstream zone sensor is not occupied, then the control logic proceeds to step 140 as indicated by the thick solid line in FIG. 10A. In step 140, the local region (i.e., the region being examined) is set to active and the control logic proceeds to step 142 where the local region is set to no pile-up in step 142. From here, the control logic returns to step 134.

If the downstream area sensor is occupied at step 138, then the control logic proceeds to step 144, as indicated by the thick solid line in FIG. 10C, to determine if the local area sensor is occupied at step 144. If not, then the logic proceeds to step 146, where the state of the local region is locked (latch), i.e., remains in its current inactive or active state, at step 146. The control logic proceeds to step 142 where the local region is set to no pile-up and returns to step 134. If the local zone sensor is occupied at step 144, the logic proceeds to step 148 where the local zone is set to inactive and then to step 150 where the local zone is set to stacked.

Referring to fig. 11A to 11I, a series of diagrams show an example of the operation of the one-run-up accumulation mode control logic. 11A-11I each show regions 1-6, labeled only 152, 154, 156, 158, 160, and 162 in FIG. 11A, with sensors 152a, 154a, 156a, 158a, 160a, and 162a, respectively. Zone 1 is controlled by the feed interface module 164, zones 2 and 3 are controlled by the zone control module 166, zones 4 and 5 are controlled by the zone control module 168, and zone 6 is controlled by the discharge interface module 170. As mentioned above, in the one-run-up pile-up mode, the region 6 is inactive until such time as a release command is received from an external system.

Packages 1 entering zone 1 and occupying sensor 152 are shown in fig. 11A and 11B. Fig. 11C shows package 1 occupying sensor 154a of zone 2 when package 2 enters zone 1 while zone 1 is still active. Fig. 11D shows package 1 advanced a little further than shown in fig. 11C, but still occupying sensor 154 a. Package 2 occupies sensor 152 a. Under the one run up control logic, zone 2, which is a downstream zone of zone 1, is occupied, and the state of local zone sensor 152 is checked. Since it is occupied by parcel 2, the control logic sets the local zone, zone 1, to inactive and stacked. In fig. 11E, the package passes sensor 154a, so zone 1 becomes active. In fig. 11F, package 2 occupies sensor 152a and package 3 occupies sensor 152a, resulting in zone 1 being deactivated such that package 3 remains in zone 1 until package 2 clears sensor 154 a. Fig. 11G shows package 1 arriving at zone 6, occupying sensor 162a, and package 2 arriving at zone 5, occupying sensor 160 a. Zone 5 is deactivated as the downstream sensor of zone 5 (sensor 162a of zone 6) and sensor 160a of zone 5 are occupied. Zone 5 will remain deactivated (locked) until sensor 162a of zone 6 is clear.

In FIG. 11H, package 3 occupies sensor 158a of zone 4, sensor 160a of zone 5 is blocked, and zone 4 is locked until sensor 160a of zone 5 is clear. Package 4 occupies sensor 154 a. Fig. 11I shows removal of the package 2 from the conveyor. The region 5 will remain locked until the region 6 becomes clear. However, as sensor 160a of zone 5 becomes unoccupied, zone 4 will become active (unlocked), thereby moving package 3 into zone 5. In doing so, the camera eye 158a of zone 4 will become clear, unlocking zone 3, thereby advancing the package 4.

Referring to fig. 12A, 12B and 12C, the same control logic representing a run-up pile-up mode with sensors coupled is shown, respectively. Unless there is a release command, the most downstream region of the system (i.e., the drain region) will be inactive in the one-run-up mode with the sensor coupled. The second most downstream region will use simple slide stop logic. For each region thus controlled, the control logic is executed independently by each module. The difference between fig. 12A, 12B and 12C is the illustrated path after the control logic is executed.

At step 172, it is determined whether the accumulation conveyor is in a run-up mode with sensors coupled. If not, the logic proceeds to step 174 where the logic checks for additional stacking patterns at step 174. If the one-run-up mode with sensors coupled is active, the logic proceeds to step 176 where step 176 determines whether both downstream zone sensors are occupied. If both downstream zone sensors are not occupied, then control logic proceeds to step 178 as indicated by the thick solid line in FIG. 12A. At step 178, the local region (i.e., the region being examined) is set to active and control logic proceeds to step 180 where the local region is set to no pile-up at step 180. From here, control returns to step 172.

If both downstream zone sensors are occupied at step 176, then the control logic proceeds to step 182 to determine if the local zone sensor is occupied at step 182. If not, then the logic proceeds to step 184 as indicated by the thick solid line in FIG. 12C, where the local region is locked, i.e., remains in its current inactive or active state, at step 184. The control logic proceeds to step 180 where the local region is set to no pile-up and returns to step 172. If the local zone sensor is occupied at step 182, the logic proceeds to step 186 where the local zone is set to inactive and then to step 188 where the local zone is set to piled up.

Referring to fig. 13A to 13G, an example of the operation of the one-run-up accumulation mode control logic to which the sensor is coupled is shown in a series of diagrams. 13A-13G each show regions 1-6, labeled only 190, 192, 194, 196, 198, and 200 in FIG. 13A, with sensors 190a, 192a, 194a, 196a, 198a, and 200a, respectively. Zone 1 is controlled by the feed interface module 202, zones 2 and 3 are controlled by the zone control module 204, zones 4 and 5 are controlled by the zone control module 206, and zone 6 is controlled by the discharge interface module 208. As mentioned above, in the one-run-up pile-up mode, the region 6 is inactive until such time as a release command is received from an external system.

Fig. 13A shows packages 1, 2, and 3 on an accumulation conveyor. Package 1 occupies sensor 198a of zone 5, and zones 1-5 are active and zone 6 is inactive. In fig. 13B, package 1 is being conveyed onto inactive zone 6, and packages 2 and 3 occupy sensors 194a and 192a of zones 3 and 2, respectively. Zone 1 is set to inactive as package 4 occupies sensor 190. In fig. 13C, package 2 is no longer occupying sensor 194a, and therefore zone 1 has been set to active. Fig. 13D shows package 2 occupying sensor 198a of zone 5. Zone 5 is the second most downstream zone following the one-run up control logic, with the intermediate downstream sensor 200a occupied and the zone 5 sensor occupied, zone 5 set to inactive. In fig. 13E, zones 3 and 4 are inactive as a result of these zones being occupied and their respective two downstream zones being occupied.

Fig. 13F shows removal of the package 3 from the accumulation conveyor. Since zone 4 is locked as a result of the two downstream sensors 198a and 200a being occupied, zone 4 remains inactive despite sensor 196a being clear. As a result of the sensor 196a not being occupied, zone 3 becomes active. Fig. 13G shows package 4 advanced to occupy sensor 196a of zone 4, with zone 4 becoming inactive and locked as sensors 198a and 200a are occupied, and package 5 advanced to occupy sensor 194a of zone 3, with zone 3 becoming inactive and locked as sensors 196a and 198a are occupied.

One aspect of the invention that may be incorporated is zone crowding as a control strategy designed to optimize the use of an accumulation conveyor. The accumulation conveyor typically still has significant gaps between packages. This is especially true when extended length regions are used. The zone congestion handling control logic is to reduce gaps between parcels after the local zone is determined to have been accumulated.

Physical congestion processing is realized by means of transmitter pulsation (pulsing) realized by a congestion processing control algorithm, such as that shown in fig. 14. Congestion handling control logic is executed for each local area, and is activated if the intermediate downstream area has been congested for a period of time and the local areas have been piled up for a period of time. In one embodiment, the time period is five seconds.

Referring to fig. 14, congestion handling logic determines whether the local sensor is clear at step 210. If it is clear, the area is not piled up and the congestion handling routine (routine) and the five second delay are reset in step 212. If the local sensor is not clear, control proceeds to step 214 to determine if the local area has been designated as congested. If so, the control logic returns to program housekeeping (programhousekeeping), and if the local area is not already congested, the logic proceeds to step 216 and determines whether the local area is designated as having been piled up for more than five seconds. If not, the congestion handling routine will return to the procedural housekeeping. If the local area has been piled up for more than five seconds, then the control logic determines whether the downstream area is congested at step 218. If not, the control logic will return to the program housekeeping. If the downstream area is congested, the control logic will initiate physical congestion handling of the routine at step 220. Referring to fig. 15, steps of step 220, initiated at 222, are shown activating the region for a crowd-on-time period determined by the DIP switch setting. The local area is then deactivated at step 224 for the congestion off time, also determined by the DIP switch settings. Steps 226 and 228 increase and compare the number of iterations performed and, once the number of iterations meets a desired or defined number, the control logic returns to step 230 shown in fig. 14 where the logic determines whether the local sensor is clear at step 230. If it is, the congestion handling routine and time delay are reset at 212. If not, control continues to step 232 and checks whether the congestion processing has ended. If it is not, then control returns to congestion handling in a forward step 220. If the congestion processing is finished, the local area congestion flag is set in step 234.

Referring to fig. 16, an alternative embodiment of a portion of the control logic shown in fig. 14 and 15 is shown. The step numbers in fig. 16 correspond to the step numbers in fig. 14 and 15, respectively, with a' added to each number. The step with the truncated leads in fig. 16 is connected with the corresponding steps found in fig. 14 and 15.

In one embodiment, the DIP switch setting is configured to select between the following congestion on time/congestion off time/number of iterations: 0/not applicable/0; 0.400 sec/2.0 sec/3 iterations; 0.550 seconds/2.5 seconds/3 iterations; and 0.700 sec/3.0 sec/3 iterations. The crowd-sourced time must be long enough to be effective-it must be long enough to achieve a transmitter speed that is sufficient to transmit the desired surge (surge). Other considerations include the desired density of the crates and the collision tolerance of the crates. The congestion shutdown time is selected to be long enough to allow the transmitter to stop. In combination with high congestion on time, high congestion off time may be required.

Congestion handling need not be implemented on a global basis and some areas may have disabled congestion handling routines set by the position of the DIP switch. Any zone or control module with congestion handling disabled does not run the congestion handling routine and will report to its upstream neighbors that it is congested. The discharge area may always have congestion processing disabled.

One aspect that may be included in embodiments of the present invention is a zone sleep feature that advances the reactivation of two zones. The sleep function temporarily suspends the action of the active area for a period of time where no product movement is sensed. Sleep may be a global setting and may be turned on and off at the interface module. The sleep logic monitors the status of the local area sensor and the status of the first and second upstream sensors. If all three regions are clear for a time period tracked by the sleep timer, which is set to twenty seconds in one embodiment, then the local region will enter sleep mode. When a zone is in sleep mode, the zone is inactive.

FIG. 17 illustrates the control logic steps associated with "waking up" a sleep zone that are repeatedly performed for each zone sensor of the stacked conveyor regardless of whether the associated zone is sleeping. Step 236 verifies that sleep is enabled for a particular zone. At step 238, the logic determines whether the local area sensor is blocked. If not, no action is taken and the program returns to the beginning. If the local area sensor is blocked at 238, the logic proceeds to step 240 where the sleep timer and sleep state (if set) are reset for all areas controlled by the particular module at step 240. This means that if the sleep state of a zone is sleeping, its state is reset and the zone is woken up. Control then proceeds to step 242 and resets the sleep timer and sleep state (if set) for the nearest downstream zone. Control then proceeds to step 244 and resets the sleep timer and sleep state (if set) for the second proximate downstream zone. Basically, when its local area sensor or two intermediate upstream area sensors are blocked, the area will exit the sleep mode. If the sensors of the sleep zone become blocked, the lower two downstream zones will wake up.

Another feature that may be included in embodiments of the present invention is flow and occlusion detection. An alarm flag is set if the local area sensor is blocked and the local area is active and the sensor of the downstream area is clear for a period of time greater than, for example, ten seconds and the downstream area sensor is blocked. The system attempts to push any parcel in the upstream region through by coupling the local region with the logic state of the downstream region. In effect, the local area reports to the upstream area the same logical state (blocked, clear, occupied, or not occupied) that it is receiving from the downstream area. This results in the upstream zone being active. If the upstream zone sensor remains blocked for a period of time greater than, for example, 30 seconds and the downstream zone sensor is not blocked for the same period of time, then a blockage is detected and the local zone is decoupled from the downstream zone and reports that the upstream is occupied, thereby initiating the accumulation process upstream of the blockage. If the "push through" becomes blocked by the downstream zone sensor during the 30 second time period, then it indicates that the product may move through the localized zone and that the localized zone remains coupled to the downstream zone. The system stays in the blocked or coupled state until the local area sensor becomes clear, at which point all error and alarm flags associated with the local area are eliminated. Meanwhile, in such a blocking situation, the global slab (slug) release downstream of the blocking will work properly. The local area release function is disabled for blocked areas so that the release is subject to the block detection and push through logic functions described herein.

Referring to FIG. 18, which illustrates flow and occlusion detection control logic, at 246, the control determines whether the local area sensor is blocked and whether the local area is active. If the local area sensor is not blocked or the local area is inactive, then control moves to 248 where, at 248, it is determined whether the local area sensor is clear and the control logic resets the flag and decouples the local area (if it is coupled). If the local area sensor is blocked, the control logic exits. If the local area sensor is blocked and the local area is active 246, then control moves to step 252 to determine if the JAM flag is set (indicating that the area has been marked as blocked) in step 252. If the JAM flag is set, then the control logic will return to the beginning at step 246. If the JAM flag is not set, control proceeds to step 254. If the downstream region is clear and active at 254, and the upstream region is occupied for a period of time greater than the 10 second period shown in the embodiment, then control will proceed to step 256 where the downstream region is coupled with the local region, i.e., the logical state of the downstream region is sent to the local region. From here, control proceeds to step 258, setting a flag ZoneFlow alarm and flashing the local area LED. Control proceeds to step 260 and detects whether the downstream region is clear and active, the upstream region being blocked for a period of time greater than 30 seconds in the embodiment. If so, the push through blocking attempt terminates and, at step 262, the local region is decoupled from the downstream region. If less than 30 seconds, the control logic loops back to 246 and continues to attempt to push through the congestion. From step 262, control sets the JAM flag at 264 and then returns to 246. With the JAM flag set, the control will loop out at step 252, avoiding further push through blocking attempts.

In some of the figures used herein, abbreviations are used. Some of which are listed below:

DZCM-double-zone control module

DZIM-double-area interface module

DZCS-double-zone control system

LZ-local zone

DSZ-downstream zone

USZ-upstream region

DSS-downstream sensor

LSS local area sensor

The foregoing description of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments were chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. The scope of the invention is to be defined by the claims as filed below.

Claims (37)

1. A method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone and a second zone, the second zone being downstream of the first zone, the method comprising the steps of:

a. determining whether the second area is occupied by a second item; and

b. setting the first zone to an inactive state if it is determined that the second zone is occupied by the second item.

2. The method of claim 1, further comprising the step of setting said first zone to an active state if it is determined that said second zone is not occupied.

3. The method of claim 1, wherein if the first zone is set to an inactive state, further comprising the steps of:

a. determining whether the first area is occupied by a first item; and

b. setting the first zone to a stacked state if it is determined that the first zone is occupied by the first item.

4. The method of claim 1, wherein the step of determining whether the second zone is occupied by the second item comprises the step of determining whether the second item has been present at a predetermined location for a predetermined length of time.

5. A method according to claim 3, wherein the step of determining whether the first area is occupied by the first item comprises the step of determining whether the first item has been present at a predetermined location for a predetermined length of time.

6. A method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone, a second zone and a third zone, the second zone being downstream of the first zone, the third zone being downstream of the second zone, the method comprising the steps of:

a. determining whether the second area is occupied by a second item and whether the third area is occupied by a third item; and

b. setting the first zone to an inactive state if it is determined that the second zone is occupied by the second item and it is determined that the third zone is occupied by the third item.

7. The method of claim 6, further comprising the step of setting the first zone to an active state if it is determined that either of the second zone and the third zone is not occupied.

8. The method of claim 6, further comprising, if said first zone is set to an inactive state, the steps of:

a. determining whether the first area is occupied by a first item; and

b. setting the first zone to a stacked state if it is determined that the first zone is occupied by the first item.

9. The method of claim 6, wherein the step of determining whether the third area is occupied by the third article comprises the step of determining whether the third article has been present at a predetermined location for a predetermined length of time.

10. The method of claim 6, wherein the step of determining whether the second zone is occupied by the second item comprises the step of determining whether the second item has been present at a predetermined location for a predetermined length of time.

11. The method of claim 8, wherein the step of determining whether the first area is occupied by the first article comprises the step of determining whether the first article has been present at a predetermined location for a predetermined length of time.

12. A method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone and a second zone, the second zone being downstream of the first zone, the method comprising the steps of:

a. determining whether the second area is occupied by a second item;

b. determining whether the first area is occupied by a first item; and

c. setting the first zone to an inactive state if it is determined that the first zone and the second zone are occupied.

13. The method of claim 12, further comprising the step of maintaining said first zone in its current state if it is determined that said first zone is not occupied.

14. The method of claim 13, wherein the current state of the first region is active.

15. The method of claim 13, wherein the current state of the first zone is inactive.

16. The method of claim 12, wherein if said first zone is set to an inactive state, further comprising the step of setting said first zone to a stacked state.

17. The method of claim 12, further comprising the step of setting said first zone to an active state if it is determined that said second zone is not occupied.

18. The method of claim 12, wherein the step of determining whether the second zone is occupied by the second item comprises the step of determining whether the second item has been present at a predetermined location for a predetermined length of time.

19. The method of claim 12, wherein the step of determining whether the first area is occupied by the first article comprises the step of determining whether the first article has been present at a predetermined location for a predetermined length of time.

20. A method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, one of the plurality of zones comprising a discharge zone, the plurality of zones comprising at least a first zone, a second zone and a third zone, the second zone being downstream of the first zone, the third zone being downstream of the second zone, the method comprising the steps of:

a. determining whether the second area is occupied by a second item and whether the third area is occupied by a third item;

b. determining whether the first area is occupied by a first item; and

c. setting the first zone to an inactive state if it is determined that the first zone, the second zone, and the third zone are occupied.

21. The method of claim 20, further comprising the step of maintaining said first zone in its current state if it is determined that said first zone is not occupied.

22. The method of claim 21, wherein the current state of the first region is active.

23. The method of claim 21, wherein the current state of the first zone is inactive.

24. The method of claim 20, wherein if said first zone is set to an inactive state, further comprising the step of setting said first zone to a stacked state.

25. The method of claim 24, further comprising the step of setting the first zone to an active state if it is determined that the second zone or third zone is not occupied.

26. The method of claim 20, wherein the step of determining whether the third area is occupied by the third article comprises the step of determining whether the third article has been present at a predetermined location for a predetermined length of time.

27. The method of claim 20, wherein the step of determining whether the second zone is occupied by the second item comprises the step of determining whether the second item has been present at a predetermined location for a predetermined length of time.

28. The method of claim 20, wherein the step of determining whether the first area is occupied by the first article comprises the step of determining whether the first article has been present at a predetermined location for a predetermined length of time.

29. A method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, the plurality of zones comprising at least a first zone and a second zone, the second zone being downstream of the first zone, the method comprising the steps of:

a. determining whether an item is at a predetermined location in the first region;

b. determining whether the second area is in a congested state;

c. determining whether the first region has been in a stacked state for at least a predetermined length of time; and

d. if it is determined that an article is in the first zone at the predetermined location, the second zone is in a crowded state, and the first zone has been in a stacked state for at least a predetermined length of time, then,

i. activating the first region for a first predetermined length of time; and

deactivating the first region.

30. The method of claim 29, wherein deactivating the first area comprises deactivating the first area for a second predetermined length of time.

31. The method of claim 29, wherein the steps of activating the first area and deactivating the first area are repeated at least once.

32. The method of claim 29, comprising the steps of: after performing the steps of activating and deactivating the first zone at least once, it is again determined whether an item is at the predetermined location in the first zone.

33. The method of claim 32, wherein the steps of activating and deactivating the first zone, and re-determining whether an item is at the predetermined location in the first zone, are repeated a plurality of times.

34. The method of claim 32, comprising the steps of: repeating the steps of activating and deactivating the first zone if an item is determined to be at the predetermined location in the first zone after the step of again determining whether the item is at the predetermined location in the first zone.

35. A method according to claim 29, comprising the step of setting said first zone to a congested state.

36. A method of controlling an accumulation conveyor to selectively accumulate a plurality of articles conveyed by the accumulation conveyor, the accumulation conveyor comprising a plurality of zones, the plurality of zones comprising at least a first zone, a second zone downstream of the first zone, and a third zone upstream of the first zone, the method comprising the steps of:

a. determining whether the first area is occupied by a first item;

b. determining whether the first region is in an active state;

c. determining whether the second area is occupied by a second item;

d. determining whether the second region is in an active state;

e. determining whether the third item has been at a third predetermined location in the third zone for at least a first predetermined length of time; and

f. controlling the third zone based on a condition of the second zone if it is determined that the first zone is occupied, the first zone is determined to be in an active state, the second zone is determined to be unoccupied, the second zone is determined to be in an active state, and the third article is determined to be at the third predetermined location in the third zone for at least the first predetermined length of time.

37. The method of claim 36, further comprising the steps of, while controlling the third zone based on the condition of the second zone:

a. determining whether the second area is occupied;

b. determining whether the second region is in an active state;

c. determining whether the third region has been occupied for at least a second predetermined length of time; and

d. ceasing to control the third zone based on the condition of the second zone if it is determined that the second zone is not occupied, it is determined that the second zone is in an active state, and it is determined that the third zone is occupied for at least the second predetermined length of time.