GB1581536A - Control device for a metering pump - Google Patents

Description

(SA) iMPROVEMENTS IN OR RELATING TO A CONTROL DEVICE FOR A METERING PUMP (71) We, LIQUID CONTROL LIMITED, a British Company, of 25 Harcourt Street, Kettering, Northants NN16 ORR, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a control device for metering pump, the control device being adapted to ensure that the metering pump dispenses at least a predetermined volume of material in each operational stroke thereof.

Metering pumps are utilised to dispense and simultaneously meter pumpable materials such as fluids or viscous or thixotropic materials. In particular such pumps may be utilised, for example, to dispense predetermined quantities of two components of an epoxy resin adhesive.

When such a metering pump is utilised it is often important that the metering pump delivers at least a predetermined minimum quantity of material during each operational stroke of the metering pump.

In certain curcumstances failure of the pump to operate correctly in this respect can lead to a heavy financial loss. One example of such a situation is where metering pumps are being utilised to provide accuratelymetered quantities of the components of an encapsulation material utilised, for example, in the encapsulation of a large electrical transformer. Such a transformer may cost many thousands of pounds and if the encapsulation material is mixed incorrectly the entire transformer may have to he replaced.

From the foregoing it will be appreciated that there is a need for a device which is adapted to monitor the action of a metering pump and which is adapted to respond when a metering pump fails to dispense the appropriate quantity of material during a working stroke thereof.

The present invention seeks to provide such a device.

According to one aspect of this invention there is provided a control device for use with a metering pump, said control device comprising a housing including at least a first bore having a piston therein, said piston defining two chambers within the bore, said housing defining an inlet port for introducing material dispensed by said metering pump into only one of said chambers, and an outlet port for ejecting dispensed matial from the other of said chambers, and means interconnecting said chambers, there being means for detecting at least one terminal position of said piston and means responsive to the piston reaching said detected position to initiate a subsequent cycle of operation of the pump, the arrangement being such that in use, as material dispensed by the pump enters the first chamber the piston moves from a first terminal position to eject dispensed material from the second chamber reaching a second terminal position, and subsequently the piston returns to the first terminal position thereof drawing dispensed material from the first chamber to the second chamber through said means interconnecting the chambers.

Conveniently a pneumatically operated piston and cylinder device is provided to urge the piston from the said second terminal position to the first terminal position thereof and advantageously means are provided for operating said pneumatic device which means are actuated only when the said first piston is moved to said second position by the dispensed material.

Conveniently the housing includes a second bore constituting said interconnecting means which also communicates with said inlet port, said second bore communicating with the second chamber of the first bore by means of a controllable valve.

Conveniently means for detecting the said terminal position of the piston comprise means engageable with a member provided on the piston and movable thereby, and means responsive to movement of said member. Said means responsive to movement of said member may comprise means adapted to actuate an air control valve or a micro switch.

Advantageously means are provided to detect the two terminal positions of the piston said detecting means being connected to the said means to initiate a cycle of operation of the pump, the arrangement being such that, for said means continuously to initiate cycles of operation of the metering pump, the piston must reach each of the two terminal positions during each operational cycle of the metering pump.

In an alternative embodiment said piston is urged to one terminal position by means of a spring.

The invention also relates to such a control device in combination with a metering pump, and to material when prepared by such a metering pump and control device combination.

In order that the invention may be more readily understood, and so that further features thereof maybe appreciated, the invention will now be described by way of example with reference to the accompanying drawing which is a schematic view of one embodiment of the invention.

A control device in accordance with the present invention comprises a housng 1 which includes two elongate or cylindrical chambers 2, 3. The cylindrical chambers 2, 3 are generally parallel to one another and each, at one end thereof, communicates with an inlet aperture 4 provided in the housing. It is intended that a metering pump should have its outlet connected by a non-return valve (not shown) to the inlet 4.

One fo the chambers, 2, includes a piston member 5 which is mounted on an elongate piston rod 6. The piston rod 6 protrudes beyond both ends of the housing 1.

The second chamber 3 is provided, at the centre thereof with a ball valve 7 (or other suitable valve) and a control device 8 to control the valve 7. The ball valve 7 may be caused to seal the two ends of the chamber 3 from each other, thus preventing the flow of material through the chamber 3, or may be opened to permit the flow of material through the chamber 3.

The housing 1 also defines an outlet 9 which communicates with the ends of the chambers 2 and 3 remote from the ends of those chambers which communicate with the inlet 4.

The piston within the first chamber can move between two terminal positions, and means are provided to detect when the piston reaches at least one of the terminal positions.

In the illustrated embodiment when the piston 5 is in the position adjacent the inlet 4 to the first chamber the portion 10 of the piston rod 6 which protrudes from the housing 1 contacts a micro switch or an air control valve 11, or some other device, the arrangement being such that the return of the piston to this position is effectively detected by the contact of the portion 10 of the rod and the device 11. The micro switch or control valve may be adapted to initiate each cycle of operation of the metering pump so that operation of the metering pump will cease if the return of the piston to this actual position is not detected.

Similarly, in order to detect the position of the piston 5 when at the other end of the chamber 2, a disk or other protrusion 12 is provided on the portion 10 of piston rod 6 and this disk or protrusion 12 is engageable with a roller 13. The roller 13 is connected to a micro switch or air control valve or the like which is operated when the roller is moved as a result of being contacted by the disk or protrusion 12. The roller 13 is mounted on a movable carriage 14 which can be moved by rotating knob 15, the carriage 14 being movable along a track defined within a housing 16. The roller 13 may be moved between two terminal positions, one which is illustrated in solid line and the other of which is illustrated in phantom at 13'.The position 13 corresponds to a delivery per stroke of 0% of a predetermined value, and the position 13' corresponds to delivery of 100%. Thus it will be appreciated that the delivery afforded by the device may readily be adjusted.

The device is completed by a pneumatic piston and cylinder device 17 which is adapted to engage one end 18 of the piston rod, 6 and move the piston to the right as shown in the accompanying drawing, i.e.

to return the piston to a position adjacent the inlet 4.

The operation of the device will now be described.

For the purpose of explanation it is to be assumed that the device is primed, or in other words that the inlet 4 the chambers 2 and 3, the conduits leading to the outlet 9 are all full of material which has been dispensed by a metering pump. It is to be appreciated that the first chamber 2 is completely filled with such material on the side of the piston 5 remote from the inlet 4. It is further to be assumed that the roller 13 is in a position corresponding to the desired delivery volume. It is also to be appreciated that the piston 5 has been urged by the pneumatic piston and cylinder de vice 17 to its terminal position so that the end 10 of the piston rod 6 engages the micro switch or air valve 11. Operation of the device 11 causes the ball valve 7 to be closed and also initiates a cycle of operation of the metering pump.

The metering pump is operated to dispense a predetermined quantity of material (for example a nominal 15 cc.) through the non-return valve into the inlet 4. Since the material already present within the housing is not readily compressed the action of the metering pump urging material into the housing causes the piston 5 to move away from its initial position, the piston thus moving along the first chamber 2 towards the end of the first chamber 2 which is adjacent the outlet 9. This has the effect of urging the material present between the piston 5 and the outlet 4 through the outlet 4 and the material thus dispensed from the housing 1 may be led to a point of utilisation.

The material being urged into the housing by the metering pump substantially fills that part of the first chamber 2 on the inlet side of the piston 5 and as the piston gradually moves further and further away from the inlet 4 the disk or protrusion 12 provided on the piston rod 6 engages the roller 13 when a predetermined minimum quantity of material has entered the first chamber 2 (for example 14.9 c.c.), from the metering punts. When the roller 13 has been contacted by the protrusion the micro switch or control valve actuated by the roller operates and causes the ball valve to be opened, and terminates operation of the metering pump, and also initiates the pneumatic piston and cylinder device 17, which then operates to return the piston 5 to its initial position.During such movement of the piston the material present on the inlet side of the piston in the first chamber 2 is urged through the second chamber 3 and the material originally present in the second chamber is drawn into the first chamber 2 and occupies the space between the piston 5 and the outlet 4. Thus, effectively, material is transferred from the right hand side to the left hand side of the piston 5. The piston moves under the force of the pneumatic device 17 until it reaches its initial position when again the end 10 of the piston rod 6 contacts the micro switch or air control valve 11, thus indicating that the piston has returned to its initial starting position. This permits the metering pump to commence another cycle of operation.

Should the minimum quantity of material (in the example above 14.9 c.c.) not be discharged by the metering pump during a single operational cycle the piston 5 contained within the first chamber will not reach the correct position and consequently the disk or protrusion 11 provided on the piston rod 6 will not contact the appropriate roller 13. Thus the ball valve 7 will remain in a closed position and the piston in the first chamber will be locked in position. The piston will not be returned to its initial starting position and thus the metering pump will not commence a subsequent cycle of operation. It will be appreciated that, as a consequence, the entire operation of the device will cease, and the device will not, therefore, dispense any short measures of material.

Similarly, should the piston fail to return to the initial starting position for any reason the device will again cease operating and any fault in the device may be rectified before operation of the device is recommenced.

It will be appreciated that should the ball valve 7 fail for any reason the micro switches or air control valves provided to detect the two terminal positions of the piston within the first chamber may be interconnected with a control system for the metering pump in such a way that the piston within the first chamber must reach each of its terminal positions during each operation cycle if the pump is to be allowed to operate continuously.

Whilst the invention has been described with reference to one particular embodiment thereof it will be appreciated that many modifications or alterations may be made to the invention.

For example the pneumatic device 17 may be replaced by a spring or the like which biasses the piston to its initial position. In such an embodiment whilst the ball valve is closed the piston cannot return to its initial position, since such movement would result in oompression of the pumped material. However, once the ball valve is opened in response to detection of the desired position of the piston, and the pump has stopped operating, the piston can return to its initial position.

The ball valve may be replaced by a plug valve or the like in some embodiments the device 11 may be omitted or may be positioned to detect satisfactory operation of the pneumatic device. If the device 11 is omitted a control device would be provided, to close the ball valve 7 and initiate a cycle of operation of the metering pump after initial operation of the pneumatic device.

WHAT WE CLAIM IS:- 1. A control device for use with a metering pump, said control device comnrising a housing including at least a first bore having a piston therein, said piston defining two chambers within the bore, said housing defining an inlet port for

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. vice 17 to its terminal position so that the end 10 of the piston rod 6 engages the micro switch or air valve 11. Operation of the device 11 causes the ball valve 7 to be closed and also initiates a cycle of operation of the metering pump. The metering pump is operated to dispense a predetermined quantity of material (for example a nominal 15 cc.) through the non-return valve into the inlet 4. Since the material already present within the housing is not readily compressed the action of the metering pump urging material into the housing causes the piston 5 to move away from its initial position, the piston thus moving along the first chamber 2 towards the end of the first chamber 2 which is adjacent the outlet 9. This has the effect of urging the material present between the piston 5 and the outlet 4 through the outlet 4 and the material thus dispensed from the housing 1 may be led to a point of utilisation. The material being urged into the housing by the metering pump substantially fills that part of the first chamber 2 on the inlet side of the piston 5 and as the piston gradually moves further and further away from the inlet 4 the disk or protrusion 12 provided on the piston rod 6 engages the roller 13 when a predetermined minimum quantity of material has entered the first chamber 2 (for example 14.9 c.c.), from the metering punts. When the roller 13 has been contacted by the protrusion the micro switch or control valve actuated by the roller operates and causes the ball valve to be opened, and terminates operation of the metering pump, and also initiates the pneumatic piston and cylinder device 17, which then operates to return the piston 5 to its initial position.During such movement of the piston the material present on the inlet side of the piston in the first chamber 2 is urged through the second chamber 3 and the material originally present in the second chamber is drawn into the first chamber 2 and occupies the space between the piston 5 and the outlet 4. Thus, effectively, material is transferred from the right hand side to the left hand side of the piston 5. The piston moves under the force of the pneumatic device 17 until it reaches its initial position when again the end 10 of the piston rod 6 contacts the micro switch or air control valve 11, thus indicating that the piston has returned to its initial starting position. This permits the metering pump to commence another cycle of operation. Should the minimum quantity of material (in the example above 14.9 c.c.) not be discharged by the metering pump during a single operational cycle the piston 5 contained within the first chamber will not reach the correct position and consequently the disk or protrusion 11 provided on the piston rod 6 will not contact the appropriate roller 13. Thus the ball valve 7 will remain in a closed position and the piston in the first chamber will be locked in position. The piston will not be returned to its initial starting position and thus the metering pump will not commence a subsequent cycle of operation. It will be appreciated that, as a consequence, the entire operation of the device will cease, and the device will not, therefore, dispense any short measures of material. Similarly, should the piston fail to return to the initial starting position for any reason the device will again cease operating and any fault in the device may be rectified before operation of the device is recommenced. It will be appreciated that should the ball valve 7 fail for any reason the micro switches or air control valves provided to detect the two terminal positions of the piston within the first chamber may be interconnected with a control system for the metering pump in such a way that the piston within the first chamber must reach each of its terminal positions during each operation cycle if the pump is to be allowed to operate continuously. Whilst the invention has been described with reference to one particular embodiment thereof it will be appreciated that many modifications or alterations may be made to the invention. For example the pneumatic device 17 may be replaced by a spring or the like which biasses the piston to its initial position. In such an embodiment whilst the ball valve is closed the piston cannot return to its initial position, since such movement would result in oompression of the pumped material. However, once the ball valve is opened in response to detection of the desired position of the piston, and the pump has stopped operating, the piston can return to its initial position. The ball valve may be replaced by a plug valve or the like in some embodiments the device 11 may be omitted or may be positioned to detect satisfactory operation of the pneumatic device. If the device 11 is omitted a control device would be provided, to close the ball valve 7 and initiate a cycle of operation of the metering pump after initial operation of the pneumatic device. WHAT WE CLAIM IS:-

1. A control device for use with a metering pump, said control device comnrising a housing including at least a first bore having a piston therein, said piston defining two chambers within the bore, said housing defining an inlet port for

introducing material dispensed by said metering pump into only one of said chambers, and an outlet port for ejecting dispensed material from the other of said chambers, and means interconnecting said chambers, there being means for detecting at least one terminal position of said piston and means responsive to the piston reaching said detected position to initiate a subsequent cycle of operation of the pump, the arrangement being such that, in use, as material dispensed by the pump enters the first chamber the piston moves from a first terminal position to eject dispensed material from the second chamber, reaching a second terminal position, and subsequently the piston returns to the first terminal position thereof drawing dispensed material from the first chamber to the second chamber through said means interconnecting the chambers.

2. A control device according to claim 1 wherein a pneumatically operated piston and cylinder device is provided to urge the piston from said second terminal position to the first terminal position thereof.

3. A control device according to claim 2 wherein means are provided for operating said pneumatic device which means are actuated only when the said first piston is moved to said second position by the dispensed material.

4. A control device according to any one of the preceding claims wherein the housing includes a second bore constituting said interconnecting means which also communicates with said inlet port, said second bore communicating with the second chamber of the first bore by means of a controllable valve.

5. A control device according to any one of the preceding claims wherein means for detecting the said terminal position of the piston comprise means engageable with a member provided on the piston and movable thereby, and means responsive to movement of said member.

6. A control device according to claim 5, wherein the means responsive to movement of said member comprise means adapted to actuate an air control valve or a micro switch.

7. A control device according to any one of the preceding claims wherein means are provided to detect the two terminal positions of the piston said detecting means being connected to the said means to initiate a cycle of operation of the pump, the arrangement being such that, for said means continuously to initiate cycles of operation of the metering pump, the piston must reach each of the two terminal positions during each operational cycle of the metering pump.

8. A control device according to claim 1 wherein said piston is urged to one terminal position by means of a spring.

9. A control device for a metering pump substantially as herein described with reference to and as shown in the accompanying drawings.

10. A control device according to any one of the preceding claims in combination with a metering pump.

11. Material when prepared by a metering pump provided with a control device according to any one of the preceding claims.