GB2039079A - Electric motor driving-gear - Google Patents

Abstract

An electric motor control apparatus has means for stopping the motor M when an output shaft 136 driven thereby is in predetermined angular positions. The said means includes a motor supply circuit containing, in addition to a main control switch CSW, light-emitting diodes LED1, LED2 and corresponding photo-transistors PT1 and PT2. In the said predetermined positions of the output shaft, openings (186, 188) or notches (190, 192) in a rotary member (160) fixed for rotation with the output shaft allow light from one or other of the light-emitting diodes to reach and activate the corresponding photo-transistor, thereby interrupting the circuit and stopping the motor with the output shaft in the respective angular position. Alternatively, permanent magnets mounted on the rotary member may co-operate with a Hall effect element to stop the motor in predetermined angular positions of the output shaft. <IMAGE>

Description

SPECIFICATION Electric motor driving-gear.

The present invention relates to an apparatus of the kind comprising an electric motor drivably connected through a gear train to an output shaft, means for detecting the angular position of the output shaft, an electrical supply circuit for the supply of electric current to the motor and a control switch and a detector switch both connected in the electrical circuit. The output shaft may be drivably connected to the ball of a ball valve so as to serve for opening and closing the latter.

To detect the angular position of such an output shaft, microswitches have been commonly used. Each such micro-switch has a contact member capable of being changed over with a snap action between two contact positions through an operating rod actuated by a cam drivably connected with the output shaft. Microswitches have the disadvantage in that, because of variation in action point, the setting thereof must be adjusted for each switch to operate exactly at the desired angular position of the output shaft. Since each such micro-switcli is operated by physical contact with the cam moved by the output shaft, it is subjected at all times to displacement and vibration of the output shaft and is liable to be damaged in particular when the cam rotates in the reverse direction to that which is intended.

Micro-switches are unsuitable for frequent operation, often vary in action point during service and have a short service life. Micro-switches are moreover disadvantageous in installation because of their large size and the amount of space which théy occupy.

An object of the present invention is to provide an improved apparatus of the kind initially referred to and in particular to provide such apparatus with an improved output shaft position detector. With this object in view the detecting means of the apparatus according to this invention includes one of more sensor-actuating elements drivably connected to the output shaft so as to be movable thereby along a predetermined path or predetermined paths and a sensor or sensors arranged or each arranged, without making contact with the sensor-actuating element or elements, to sense when the sensor or the corresponding sensor-actuating element is in a given position along its parts and wherein the detector switch is operable in response to such sensing to perform a switching operation.

Since there is no physical contact between the sensor or sensors and the said element or respective elements moved by the output shaft, the detector switch is not subjected to displacement or vibration by the output shaft, does not vary in action point, is not affected by the rotational direction of the said element or elements, is suitable for frequent operation and has a long service life. The space formed between the or each sensor and the corresponding element serves as a thermal insulator to protect the sensor or sensors. Non-contact sensor devices of this type are in general convenient to install and replace because the variation in action point can be reduced.

The invention will now be described by way of example with reference to the accompanying drawings, in which Fig. 1 is a circuit diagram containing a photo transistor embodying photo diodes; Fig. 2 is a vertical section of an apparatus according to a first embodiment of this drivably connected to a ball valve; Fig. 3 is a vertical section taken on line Ill-Ill in Fig. 2, with the ball valve omitted; Fig. 4 is a fragmentary sectional view taken on the line IV-lV in Fig. 3; Fig. 5 is a circuit diagram of the embodiment shown in Figs. 2 to 4; Figs. 6 and 7 are a fragmentary sectional view and a circuit diagram, corresponding to Figs. 4 and 5 respectively, illustrating details of another embodiment of the invention;; Figs. 8 to 10 illustrate further embodiments of this invention, Fig. 8 being a fragmentary sectional view similar to Fig. 4, Fig. 9 a block diagram of a circuit for producing output from a Hall effect element and Fig. 10 a simplified diagram of a motor supply circuit.

Referring to Fig 1 , the reference numeral 20 indicates a light emitting diode, the reference numeral 22 a resistor, the reference numeral 24 a photo diode, and the reference numeral 26 a transistor. An assembly enclosed by a broken line rectangle and indicated by the reference numeral 28 constitutes a photo transistor. If provision is made for a ray of light to be transmitted from the light emitting diode 20 to the photo diode 24 and a means for interrupting this ray of light is provided, the photo transistor 28 can be used as a switching element.

There are numerous devices other than photo transistors which make use of a photo diode; namely, photo SCR (LASCR: light activated silicon-controlled rectifiers), planar silicon photo switches (PSPS), and photo SCR (LASCS: light activated silicon-control switches). The sensor of a detector switch with a photo diode and a light emitting element such as a light emitting diode are arranged facing each other with a narrow space between them, If a thin disc having transparent and nontransparent part is rotated in the narrow space together with an output driven by an electric motor via reduction gearing, malfunctions due to disturbance light are reduced.

Detector switches having Hall effect elements are suitable for use as detector switches taking information from detector-actuating members without contact through an electro-magnetic field.

In this case it is recommended to use a small permanent magnet piece as a detector member.

In the embodiment of the present invention shown in Figures 2 to 5, the reference numeral 100 indicates an electric motor transmitting drive through a reduction gear and the reference numeral 102 indicates a ball valve.

The casing of the electric motor and reduction gear 100 comprises a main mounting base 104 made of a synthetic resing having good thermal insulating properties and a light, metallic cover 106 having good heat radiating properties. An 0ring gasket 108 composed of synthetic rubber is provided between the main mounting base 104 and the cover 106. A nipple 111 is screwed into the main mounting base 104 to serve as an outlet for lead wires (not shown in Figure 1) and a union nut 110 is screwed thereon to admit the end of a lead wire protector tube (also not shown). The electric motor and reduction gear 100 is mounted on the ball valve 102 by means of a mounting sleeve 112 made of stainless steel which has a low thermal conductivity. The mounting sleeve 112 to which a mounting plate 114 is welded, is moulded into the main mounting base 104.The mounting sleeve 112 is provided with radiator fins 11 6 and vent holes 118 for better dissipation of heat. To fix the mounting sleeve 112 to the neck 200a of a valve body 200, a clamping member 120 thereof is axially split into two halves which are clamped together by a screw 122. A screw 124 extends through a hole in the mounting sleeve 112 and is engaged in a tapped bore in the neck 200a of the valve body 200.

Within the casing 104, 106 is an electric motor 126 which is mounted on a gear box 128 comprising a reduction gear train which transmits drive from the shaft of the electric motor 126 to an output shaft 132. The gear box 128 is fixed to the main mounting base 104 by means of screws 130 the end parts of the shanks of which are screwed into the mounting plate 114. A synthetic rubber O-ring packing seated in an annular seating in the lower wall of the mounting base surrounds the output shaft 132. The output shaft 132 has an extension 136 the end part 138 of which protrudes outside the cover 106 and is provided with flats for engagement by a spanner. Since the gear train is provided with a one-way clutch, the output shaft 132 can be turned in a predetermined direction by applying a spanner to the end part 138 thereof.A synthetic rubber O-ring 140 seated in an annular seating in the upper wall of the cover 106 surrounds the extension 136 of the output shaft 132. The lead wires (not shown in Figure 1) of the electric motor 126 (not shown) are taken out through the lead wire outlet 142 and connected to plugs 144. The pins of the plugs 144 are equivalent to the terminals M 1 and M2 shown in Figure 5. Electric supply lead wires enter through the nipple 111 and are connected to terminals 146, 148 and 150 (equivalent to A, B and G in Figure 5 respectively). A change-over switch 152 is fixed on the gear box 128 by means of fittings 168 and screws 180. A base plate 166 for an electric current supply control circuit is removably secured to the fittings 168 by means of screws 154 and 156. The base plate 166 is provided with a printed circuit including electronic elements and switches.On the extension 136 of the output shaft 132 is mounted a disc-shaped detector-activating member 160 made of a nontransparent substance. The detector-actuating member 160 is provided with openings 186 and 188 and notches 190 and 192 permitting rays of light to pass, these openings and notches being disposed in each case 180 degrees apart on the circumference of a circle concentric with the detector-actuating member 160. The detectoractuating member 160 co-operates with two sensors 162 and 164, both fixed on the base plate 166, one sensor 162 comprising a light emitting element (LED 1) and a photoelectric element 1 62b (PT1) located opposite each other and the other sensor 164 comprising a light emitting element (LED2) and a photoelectric element 164b (PT2) also located opposite each other.The path of light 196 for the sensor 162 intersects the circular orbit of the notches 190 and 192 and the path of light 194 for the sensor 164 intersects the circular orbit of the openings 186 and 188. Figure 4 shows the position when the opening 188 coincides with the path of light 194. On completion of successive 900 clockwise rotational movements of the detector-actuating member 160 from the position shown in Figure 1, first the notch 190 will be brought into aligment with the light path 196, next the opening 186 will be brought into alignment with the light path 194, and then the notch 192 will be brought into alignment with the light path 196. The sensor 162 is fixed to the base plate 166 by means of screws 170 and 172. A condenser 174 is fixed to the fittings 1 68 by means of a screw 176.The detector actuating member 160 is fixed to the extension 136 of the output shaft 132 by a pin 178. The cover 106 is removably attached to the main mounting base 104 by means of screws 182 and 184.

A ball valve casing comprises the valve body 200 having the neck 200a and a union 202 screwed therein, the union 202 being provided with screw-threaded bores 204 and 206 for connection to piping. In the central part of the valve body is mounted a vertical spindle 208 the upper end part 210 of which is provided with flats to fit into a connector piece 212. The lower end part of the output shaft 132 fits into the upper end of the connector piece 212. The connector piece 212 is made of synthetic resin in order to provide thermal insulation and is reinforced by a metallic protector tube tightly surrounding it. An intermediate part 251 of the spindle 208 having flats on opposite sides thereof engages in a correspondingly shaped recess in the upper part of the valve ball 216 and a lower end part 250 of this spindle extends downwardly through the remainder of the valve ball 216 and across a transverse through bore 218 thereof. On the two opposite sides of the valve ball 216 are annular valve seats 220 and 222 composed of synthetic resin, which valve parts are pressed against the valve ball 216 by disc springs 228 and 230. The valve seats 220 and 222 are provided with O-ring packings 224 and 226 made of synthetic rubber.

The spindle 208 is provided with an annular flange 248 having a part-spherical lower surface against which a synthetic resin spindle sealing ring 232 is pressed upwardly by disc springs 238 and 240. A synthetic rubber O-ring packing 234 is seated in an annular seating in the lower part of the outer circumference of the sealing ring 232. To ensure smooth rotation of the spindle 208, the latter has fitted over it a washer 236 located between the disc spring 238 and the spindle sealing ring and a further washer 244 and a synthetic resin slide ring located above the flange 248. A snap ring 246 engaged in an annular seating in the bore of the neck 200a of the valve body engages over the washer 244 so as to limit upward movement thereof.The lower end of the part 250 of the spindle 208 projects downwardly from the bottom of the valve ball 216 and is rotatably mounted in a plain metal bearing 252 provided in the bottom of the valve body 200.

Referring to Figure 5, the symbol Qtu indicates an alternating current source and M the motor 126. Other symbols used in Figure 5 are used to indicate the following componenets A, B, G, Ml and M2, the terminals 146,148 and 150 and contacts of the plug 144 respectively: R, resistors: C, condensers: D, diodes: Z, Zener diodes: SCR, a thyristor (silicon controlled rectifier):TH, triacs: LED, light emitting diodes: PT, photo transistors: T, transistors: SW the change-over switch 152: CSW, a control switch. The alternating current voltage between the terminals A and B is halfwave rectified by the diode D1, made constant in voltage by the Zener diode Z1 and smoothed by the condenser C1. When the control switch CSW is open, the light emitting diode LED2 emits light.

Since at this moment the ball valve 102 is in the open position as shown in Figure 2 and the opening 188 of the detector 160 is aligned with the path of light 194, light impinges on the photo transistor PT2. Therefore, since the transistor T3 is ON, output pulses detected by the transistors T1 and T2 are shunted by the transistorT3 and the transistors T4 and T5 are OFF. The triac TH2 is not triggered and the motor M is not energised. The ball valve 102, therefore, remains in the open position shown in Figure 2 and the detector member 160 in the position shown in Figure 3.

If the control switch CSW is now closed, the light emitting diode LED2 is extinguished and the other light-emitting diode LED1 emits light At this moment light from the light emitting diode LED 1 does not reach the photo transistor PT1 because of the interruption thereof by the detector actuating disc 160. Therefore, since the transistor T3 is in the OFF position and output pulses detected by the transistors T1 and T2 keep the transistors T4 and T5 in the ON position, the voltage accumulated in the condenser C1 causes the triac TH2 to be triggered by means of the transistor T5. This process is repeated by every pulse from the transistors T1 and T2 and the triac TH2 is kept in the activated state. The motor, therefore, is energised to rotate the ball valve 102.

As the output shaft extension 136 and consequently the detector-actuating disc 1 60 rotate, both paths of light 194 and 196 are interrupted by the detector actuating disc 160 and the ball valve 102 assumes its closed position. When the path of light 196 coincides with the notch 190, light from the light emitting diode LED1 reaches the photo transistor PT1, causing the transistor T3 to assume the ON position.

Pulses from the transistors T1 and T2 are shunted by the transistor T3 and the transistors T4 and T5 assume the OFF position.

The triac TH2 cannot be triggered by the voltage through the transistor T5, being in the non-activated state. Therefore, the motor shaft stops rotating.

In this manner the motor can be controlled by opening or closing the control switch CSW while detecting the position of the output shaft (the shaft extension and detector-actuating member).

If the change-over switch SW is changed to the position shown in broken lines, the light emitting condition of the light emitting diode LED 1 or LED2 becomes the reverse of that described above with the open or closed position of the control switch CSW.

In the embodiment shown in Figures 2 to 5, the output shaft rotates in one direction only.

However, in the embodiments shown in Figures 6 and 7 the output shaft rotates alternately to and fro between the two predetermined positions.

In the following description, elements similar to those shown in Figures 2 to 5 will be referred to by the same reference numerals.

The detector-actuating member 160 is provided with a pair of interrupting protrusions 189 and 191 which are spaced apart by a predetermined angular distance. When the extension 136 of the output shaft 132 and the detector-actuating member 160 rotate through 90 degrees clockwise from the position shown in Figure 6 where the path of light 194 is aligned with the interruption protrusion 189, the path of light 196 is interrupted by the protrusion 191. Referring to Figure 7, if the motor M is energised through the terminal M2, the shaft thereof rotates in such a direction that the detector-actuating member 1 60 rotates clockwise (as seen in Figure 6).On the other hand, if the motor M is energised through the terminal M3, the motor shaft rotates in such a direction that the detector-actuating member 16Q rotates counter-clockwise (as seen in Figure 7).

The operation of the embodiment according to Figures 6 and 7 will now be briefly described.

When CSW is OFF, LED2 is emitting light At this moment, if the path of light 1 94 is interrupted by the protrusion 189 (Figure 6), PT2 is OFF and receives no light. Since pulses from T1 and T2 cannot pass PT2, T5 is OFF and the voltage is insufficient to trigger TH3. The motor cannot be supplied with electric current through the terminal M3 and its shaft therefore does not rotate.

On the other hand, if CSW is ON, LED2 is extinguished and LED1 emits light which reaches PT1. Pulses from T1 and T2 pass through PT1, making T4 and T5 ON. Since TH2 is triggered by the voltage accumulated at C1, the motor M is energised through the terminal M2 and its shaft begins to rotate. When the detector-actuating member 160 rotates clockwise (as seen in Figure 6) until the protusion 191 interrupts the path of light 196, light does not reach PT1 and the shaft of the motor M stops rotating. If CSW is OFF, similarly to the above, the motor M is energised through the terminal M3 and its shaft rotates in such a direction that the detector-actuating member 160 rotates couter-clockwise (as seen in Figure 6).

In this manner the motor shaft rotates alternately between two positions by opening or closing the control switch CSW while detecting the angular position of the detector-actuating member and hence that of the output shaft.

Figures 8 to 10 show an embodiment which communicates information between a detectoractuating member and a detector switch by way of electromagnetic fields.

The reference numeral 300 indicates an extension of an output shaft, the reference numeral 302 a detector-actuating member made, for instance, of synthetic resin, and the reference numerals 304,306,308 and 310 small permanent magnet pieces mounted on the detector-actuating member 302 at positions ahgularly spaced apart at 900 intervals. The magnet pieces 304 and 308 have positive poles at their outer ends while the magnet pieces 306 and 310 have positive poles at their inner ends. Close to the rotational orbit of the magnet pieces 304, 306. 308 and 310, a sensor comprising a Hall effect element 312 is arranged on a mounting base 314. The reference numeral 316 indicates an amplifying circuit, the reference numeral 318 a trigger circuit and the reference numeral 320 an output circuit.A direct current voltage is applied between the terminals 322 and 324. Since the Hall effect element 312 is opposite in output characteristics when a positive magnetic pole approaches it and when a negative pole does so, it is possible for the terminal 326 to produce output if a positive magnetic pole approaches it and for the terminal 328 to produce output if a negative pole approaches it. In Figure 10, the reference numeral 330 indicates an alternating current source; the reference numerals 332, 334 and 336 junctions of a control switch; the reference numeral 338 a break-junction which is opened by the output from the terminal 328; the reference numeral 340 a break-junction which is opened by the output from the terminal 326; and the reference numeral 342 an electric motor.

The operation of the embodiment shown in Figures 8 to 10 will now be described. When the junction 332 of the control switch is connected to the junction 336 and the positive magnetic pole 304 faces the Hall effect sensor 312 as shown in Figure 8, the terminal 326 produces output and the break-junction 340 is open, and therefore the motor shaft rotates. If the junction 332 of the control switch is connected to the junction 334, the motor shaft rotates. When the output shaft extension 300 rotates and the negative magnetic pole 310 faces the sensor of the Hall effect element 312, the terminal 328 produces output and the break-junction 338 is opened, and therefore the motor shaft ceases to rotate.

In this manner the motor can be controlled by detecting the invention of the output shaft electromagnetically by the use of a Hall effect element, with no physical contact with the detector actuating member 302.

Claims (10)

1. An apparatus comprising an electric motor drivably connected through a gear train to an output shaft, means for detecting the angular position of the output shaft, an electrical supply circuit for the supply of electric current to the motor, a control switch and a detector switch, said control switch and said detector switch both being connected in the electrical circuit, wherein said detecting means includes one or more sensoractuating elements drivably connected to the output shaft so as to be movable thereby along a predetermined path or predetermined paths and a sensor or sensors arranged or each arranged, without making contact with the sensor-actuating element or elements, to sense when the sensor or the corresponding sensor-actuating element is In a given position along its path and wherein the detector switch is operable in response to such sensing to perform a switching operation.

2. An apparatus as claimed in claim 1 wherein the electrical supply circuit comprises a circuit having a break-junction or a plurality of breakjunctions in parallel with one another, said break junction or break junctions being selectively connected to a current source by said control switch and opened by the detector switch in response to sensing by the or one of said sensors that the or one of said sensor-actuating elements is in said given position along its path.

3. An apparatus as claimed in claim 1 wherein the or each of said sensors is fixed on a removably mounted base plate of said electrical supply circuit in a predetermined position relative to the path of the or the respective sensor-actuating element.

4. An apparatus as claimed in claim 1 characterised in that the or each of said sensor actuating elements is a solid element.

5. An electric motor driving gear as set forth in claim 1 wherein the or each sensor is a photo electric cell and the or each of said sensor actuating elements is an opening or recess which, when located in said given position along the respective path permits light from a light source to pass through it and to impinge upon the or the respective sensors.

6. An apparatus as claimed in claim 5 wherein the or each sensor comprises a photo diode.

7. An apparatus as claimed in claim 5 wherein the or each sensor-actuating element consists of an aperture or recess in a disc fixed for rotation with the output shaft and arranged to control the supply of light to said photo electric cell.

8. An apparatus as claimed in claim 1 wherein the or each sensor is operable by magnetism.

9. An apparatus as claimed in claim 8 wherein the or each sensor is a Hall effect element.

10. An apparatus as claimed in claim 9 wherein the or each sensor-actuating element is a permanent magnet piece mounted eccentrically on a rotary member fixed for rotation with the output shaft so as to be movable thereby along a predetermined circular path and the or each Hall effect element is located adjacent a given position along said path so as to be operable electromagnetically when the or each permanent magnet piece is in said given position.