WO2003062638A1

WO2003062638A1 - Liquid dispensing pump

Info

Publication number: WO2003062638A1
Application number: PCT/GB2003/000084
Authority: WO
Inventors: Kevin John Beaumont
Original assignee: Mount Packaging Systems Ltd.
Priority date: 2002-01-18
Filing date: 2003-01-14
Publication date: 2003-07-31
Also published as: GB2390843A; GB0300949D0; GB0201103D0

Abstract

Liquid dispensing pumps of piston type have required large volumes of water or other liquid cleaning agents to achieve thorough purging when dispensing of a particular kind of liquid has been completed. A single-acting pump of this type requiring very much smaller volumes of liquid cleaning agents for thorough purging comprises a cylinder (10) containing a pneumatically-reciprocated piston (18) and valve means for enabling a supply of liquid to communicate with one or both ends of the cylinder and for enabling the liquid to be dispensed only from the other end of the cylinder. A liquid supply conduit (26) has two branches (28) and (32) communicating with respective ends of the cylinder, and the valve means comprise a first pneumatically-actuated on/off valve (36) in the branch (32) communicating with the dispensing end of the cylinder, a second pneumatically-actuated on/off valve (38) in the dispensing outlet (40) of the cylinder, and a pneumatically-operated priming valve (42).

Description

"Liquid Dispensing Pum . " This invention relates to a pump for dispensing amounts of liquid, that is to say to a so-called volumetric dispensing pump. These pumps are typically employed to dispense foodstuffs, chemicals and the like into containers, and require thorough purging when dispensing of a particular batch of liquid, such as a coloured paint, has been completed. Hitherto, liquid dispensing pumps of piston type have been of two kinds. One kind has comprised a cylinder containing a reciprocating piston wherein liquid is supplied to, and the full amount required is dispensed at one stroke of the piston from, one end of the cylinder. The other kind has comprised a cylinder containing a reciprocating piston wherein liquid is supplied to both ends of the cylinder, and half the required amount is dispensed from each end of the cylinders to a common outlet by two successive strokes of the piston in opposite directions. By virtue of their construction, both of said kinds of pumps require relatively large volumes of water or other liquid cleaning agents to achieve thorough purging. Furthermore, liquid dispensing pumps of the piston type have generally been supplied with liquid fed by gravity from a hopper.

One object of the present invention is to provide a liquid dispensing pump which requires very much smaller volumes of liquid cleaning agents to achieve thorough purging. A further object is to provide a liquid dispensing pump which operates without a liquid supply hopper but does not preclude the use of such a hopper if desired.

According to the invention, a pump for dispensing measured amounts of liquids comprises a cylinder containing a reciprocating piston, and associated valve means for selectively enabling a supply of liquid to communicate with one or both ends of the cylinder and for enabling the liquid to be dispensed only from the other end of the cylinder.

Preferably, the pump comprises a liquid supply conduit having two branches communicating with respective ends of the cylinder, and the valve means include a first power- actuated on/off valve disposed in the branch communicating with said other end of the cylinder, and a second power- actuated on/off valve disposed in a liquid-dispensing outlet in said other end of the cylinder. The power-actuated valves may be operated pneumatically.

Alternatively, the power-actuated valves may be operated electrically.

The valve means preferably include also an on/off priming valve connecting said one end of the cylinder to atmosphere.

The priming valve may be operated pneumatically. Alternatively, the priming valve may be operated electrically.

Alternatively, the priming valve may be operated manually. The piston may be operated pneumatically.

Alternatively, the piston may be operated electrically.

Preferably, the length of the stroke of the piston is variable. The supply of liquid may be fed by a low-pressure pump.

Said low-pressure pump is preferably a double- diaphragm air pump .

Alternatively, the supply of liquid may be fed by gravity from a hopper.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings of whic :-

Figure 1 is a sectional side elevation of a liquid dispensing pump; and

Figure 2 is an end view thereof.

Referring now to the drawings, a liquid dispensing pump comprises a cylinder 10 clamped in liquid-sealed relationship between an upper closure member 12 and a lower closure member 14 by means of a plurality of tie-rods 16. A piston 18 is reciprocable in the cylinder 10 without an intervening seal by a piston-rod 20 which passes through a central hole 22 in the member 12 and sealing means 24 associated with said member. The piston-rod 20 is operated pneumatically by an air cylinder (not shown) , the length of stroke of the piston 18 being variable to enable the amount of liquid dispensed to be changed. A liquid supply conduit 26 has a branch 28 communicating with a radial port 30 in the member 12 and a branch 32 communicating with a radial port 34 in the member 14. Valve means are provided for selectively enabling a supply, of liquid to communicate with the upper end or both ends of the cylinder 10 and for enabling the liquid to be dispensed only from the lower end of said cylinder. Said valve means include a first power- actuated on/off valve 36 disposed in the branch 32 and a second power-actuated on/off valve 38 disposed in a liquid- dispensing outlet 40 in the member 14. The valves 36 and 38 are operated pneumatically independently of each other. Said valve means include also an on/off priming valve 42 disposed in a port 44 in the branch 28 and connecting the upper end of the cylinder 10 to atmosphere. The valve 42 is controlled pneumatically independently of the valves 36 and 38. The supply of liquid to the pump through the conduit 26 is fed by a low-pressure pump (not shown) consisting of a double-diaphragm air pump.

In operation, the pump is primed by opening the valves 36 and 42, closing the valve 38, and supplying liquid to the pump until the valve 42 ceases to bleed air and begins to seep liquid whereupon said valve is closed until such time as the pump needs to be re-primed. The pump is then filled by raising the piston 18 with the valve 36 open and the valve 38 closed, after which the valve 36 is closed, the valve 38 is opened, and the required amount of liquid is dispensed from the outlet 40 by lowering said piston. Further measured amounts of liquid are dispensed on a continuous basis by repeating these filling and dispensing steps. When dispensing of a particular batch of liquid has been completed and the supply of liquid is discontinued, purging of the pump is effected by raising the piston 18 right to the top of its stroke, opening all three valves 36, 38 and 42, and allowing the pump to drain. The valve 38 is then closed, the valves 36 and 42 remain open, the pump is filled with a liquid cleaning agent, then the valve 42 is closed and the piston 18 is reciprocated. Lastly the valves 38 and 42 are re-opened and said piston raised right to the top of its stroke to allow said agent to drain away. The purging steps set out in the two preceding sentences may be repeated as necessary depending upon the liquid which has been dispensed. By virtue of the construction of the pump, the liquid cleaning agent is moved back and forth between the ends of the cylinder 10 to provide a highly efficient purging action, and consequently only a small volume said agent is needed for the or each purging step. Modifications are possible without departing from the scope of the invention. In one such modification, the piston is provided with a peripheral seal. In another modification, the piston-rod is operated electrically by a servo-motor. In a further modification, the valves 36 and 38 are operated electrically. In yet another modification, the priming valve is operated electrically or manually. In yet a further modification, the supply of liquid is fed by gravity from a hopper.

Claims

Claims : -

1. A pump for dispensing measured amounts of liquids comprising a cylinder containing a reciprocating piston, and associated valve means for selectively enabling a supply of liquid to communicate with one or both ends of the cylinder and for enabling the liquid to be dispensed only from the other end of the cylinder.

2. A pump according to claim 1, comprising a liquid supply conduit having two branches communicating with respective ends of the cylinder, and the valve means including a first power-actuated on/off valve disposed in the branch communicating with said other end of the cylinder, and a second power-actuated on/off valve disposed in a liquid-dispensing outlet in said other end of the cylinder.

3. A pump according to claim 2, wherein the power- actuated valves are operated pneumatically.

4. A pump according to claim 2, wherein the power- actuated valves are operated electrically.

5. A pump according to any one of the preceding claims, wherein the valve means include also an on/off priming valve connecting said one end of the cylinder to atmosphere .

6. A pump according to claim 5, wherein the priming valve is operated pneumatically.

7. A pump according to claim 5, wherein the priming valve is operated electrically.

8. A pump according to claim 5, wherein the priming valve is operated manually.

9. A pump according to any one of the preceding claims, wherein the piston is operated pneumatically.

10. A pump according to any one of claims 1 to 8, wherein the piston is operated electrically.

11. A pump according to any one of the preceding claims, wherein the length of the stroke of the piston is variable.

12. A pump according to any one of the preceding claims, wherein the supply of liquid is fed by a low-pressure pump.

13. A pump according to claim 12, wherein the low-pressure pump is a double-diaphragm air pump.

14. A pump according to any one of claims 1 to 11, wherein the supply of liquid is fed by gravity from a hopper.

15. A pump for dispensing measured amounts of liquids constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.