WO1994021918A1

WO1994021918A1 - Flexible tube pump

Info

Publication number: WO1994021918A1
Application number: PCT/NZ1994/000022
Authority: WO
Inventors: Robert Donald Grapes
Original assignee: Precision Dispensing Systems Limited
Priority date: 1993-03-22
Filing date: 1994-03-21
Publication date: 1994-09-29
Also published as: AU6387094A; CA2156827A1

Abstract

A pump for providing an accurate dosage or volume/rate of output. The pump comprises a flexible conduit (10), one end (11) being coupleable to a fluid source. The other end (12) forming or being coupleable to an outlet (24). Spaced apart longitudinally of the conduit (10) are pinching elements (14, 15 and 16). The pinch elements are arranged and controlled to successively pinch and release the conduit to result in a pulsed movement of fluid from the inlet end (11) of the conduit to the outlet end (12).

Description

FLEXIBLETUBEPUMP

This invention relates to a pump.

Peristaltic pumps as delivery pumps are known whereby fluid can be driven along a fluid flow passage. This is achieved by roller or like means coming in contact with a flexible tube (which forms, or is part of, the fluid flow passage) so as to compress the tube and move longitudinally therealong.

There are a number of draw backs with peristaltic pumps. While they can in some circumstances be arranged to provide measured "doses" or outputs it is usually not possible (or at least very difficult) to readily adjust the pump so that the measured dose or output can be altered. Also such pumps have been found to require a high level of maintenance and adjustment. For example they are not generally readily dismantled for replacement of the tube.

The present invention aims to provide a pump which is not of peristaltic action but nevertheless relies on compression and release of a flexible conduit to achieve the pumping action. It is envisaged that the pump of the present invention will provide an accurate means of regulating dosage or volume/rate of output yet be of straight forward construction. Broadly in one aspect the present invention provides a pump comprising a flexible conduit one end being coupleable to a fluid source and the other end forming or being coupleable to an outlet, there being pinching means spaced apart longitudinally of the conduit, said pinching means being arranged to successively pinch and release the conduit to result in a pulsed movement of fluid from said one end to said other end.

In the following more detailed description of the invention reference will be made to the accompanying drawings in which:-

Figure 1 is a schematic illustration of the main components of the pump, Figures 2a - 2e provide a graphic representation of the opening and closing action of the pinch means. Figure 3 is a side, partially sectioned, elevation of one embodiment of the pump according to the invention. Figure 4 is a plan view of the pump shown in Figure 3, Figure 5 is an exploded perspective view of the pump of Figures 3 and 4, and

Figure 6 is a perspective view of a bank of pumps of the type shown in Figures 3 to 5.

The pump according to the present invention is based on the concept of controlled compression and release of a flexible conduit. Accordingly in Figures 1 and 2 there is illustrated a flexible tube 10 which at one end 11 is coupled to or is adapted to be coupled to a fluid source (not shown). The fluid will generally not be under pressure but may be pressurised if the source is to be located so remote from the pump that assistance is required to move the fluid from the source to the pump, ie. to assist the action of the pump.

The other end 12 of flexible tube 10 is coupled to, is adapted to be coupled to or forms an outlet (not shown).

Three pinch means or elements are associated with the flexible tube 10. These are operative such that they can move between one state where the tube 10 is compressed (squeezed) and another state where the tube is substantially unrestricted. In this respect it should be noted that the pump elements do not need to totally release the flexible tube. Thus in the following description a reference to flexible tube 10 being not compressed covers situations where partial compression or deformation occurs. Likewise a reference to the tube being compressed includes a situation where the tube is substantially compressed but not necessarily fully pinched closed. The term "pinch" thus refers to any action applied to the tube whereby the tube can be compressed so that the flow passage therein is closed or substantially constricted. Each of the pinch elements 14, 15 and 16 can be formed by a known solenoid operated pneumatic pinch valve. The pinch element 14 can be arranged such that the flexible tube 10 can be inserted through a slotted end of the pinch valve to locate in a recess and be clamped therein by a manual clamp means. Thus with the solenoid in the inoperative position the flexible tube 10 is compressed. This type of arrangement is shown in Figure 3 in respect of inlet pinch element 14. For the purposes of description of Figures 1 and 2, however, all of the pinch elements 14, 15 and 16 are simply shown as compressing tube 10 when they are operative. Thus when pinch elements 15 and 16 are in the "rest" position the flexible tube 10 is unrestricted, ie. not compressed.

In the preferred form of the invention pinch elements 14 and 16 are located as close as possible together or at least the "nip" formed in flexible tube 10 by pinch element 16 is as close as possible to the nip of the flexible tube created by pinch element 14.

Pinch element 14 effectively forms an inlet valve, pinch element 15 an outlet valve and pinch element 16 a displacement section as will hereinafter become apparent.

In the schematic illustration of Figure 1 the pinch element 16 is preferably formed by two air cylinders or linear actuators while pinch elements 14 -and 15 are formed by single air cylinders or linear actuators. The pistons 17 of all the pump elements 14, 15 and 16 slide in bores formed in the pump body 18. The two pistons 17 of pinch element 16 bear on a compression plate 19 engaged with tube 10 while pistons 17 of pinch elements 14 and 15 are shown as bearing directly on tube 10. Seals 20 are provided with pistons 17. The pistons 17 are activated by air pressure applied thereto via air passages 21 under the control of electrically operated solenoid valves (not shown) but described hereinafter in connection with the embodiment of Figures 3, 4 and 5.

An electronic control circuit (not shown) is provided for control of the respective solenoid valves of the pinch elements 14, 15 and 16. The control circuit provides control of the sequence of opening and closing of solenoid valves over an operating (pumping) cycle. The control circuit also provides for ready adjustment of the number of cycles in given unit time as well as the number of cycles in a given period. Furthermore by altering the relative time between opening and closing of the solenoid valves and hence operation of the pinch elements 14, 15 and 16 the amount of output per pumping cycle can be regulated.

The control circuitry is of a type to achieve the functions described herein. The control behaviour in question may be achieved by hard-wire systems or by -the use of a suitably programmed microprocessor. Accordingly the actual hardware is not described herein as it is well within the scope of the skilled technician to arrive at circuitry designed to action the functional control of the solenoid valves as described herein.

In describing a pumping cycle (as shown in Figure 2) it is convenient to commence at a point where the pump is in reset mode with all pinch elements 14, 15 and 16 closed (tube 10 is constricted) as shown in Figure 2a. Pinch element 14 then opens (Figure 2b) thus the tube to the inlet side of pinch element 16 will fill with liquid. This corresponds to the "inlet valve" being open.

As the cycle proceeds pinch element 15 will remain closed while pinch element 16 opens so as to leave the flexible tube 10 unrestricted up to pinch element 15 (Figure 2c). This is followed by pinch element 14 closing and then pinch element 15 opening so that the inlet is closed and the outlet opened (Figure 2d). This is followed by pinch element 16 closing to thereby cause discharge of a pulsed flow of fluid in the direction of arrow A out the outlet end of tube 10 (Figure 2e). The volume of fluid (or pulsed flow) will essentially be the volume of fluid in tube 10 under the compression plate 19. Following this a new cycle commences by pinch element 14 opening and pinch element 15 closing to thereby return to the "inlet open" phase (Figure 2b). Pinch element 16 will then open (Figure 2c) thereby resulting in a pressure differential causing inlet fluid to be drawn into the empty space caused by fluid having been expelled from the flexible tube under the previous closing action of pinch element 16.

The pump according to the present invention is thus simple in construction and operation yet provides an effective means of drawing fluid from a bulk or fluid supply and dispensing same in a pulsed manner of a pre-determined volume per pumping cycle. Thus if a given total volume of liquid is to be dispensed in a given period of time the control circuit can be adjusted so as to determine the number of pumping cycles per unit time to provide the overall volume in a required time.

Additionally the relative position of pinch element 16 to the other pinch elements 14 and 15 could be adjusted so as to regulate the volume dispensed each pumping cycle. Also the degree of openness of the pinch elements could be adjusted to once again provide a physical adjustment of the dispensed volume. The flexible tube 10 is preferably a food grade silicone rubber which exhibits the required degree of elasticity as well as compressibility. The tube can easily be replaced by simply removing part of the body 18 and if required releasing any manual clamps of the solenoid operated pinch elements. Thus replacement of the flexible tube is a much simpler and more straight forward operation than with peristaltic delivery pumps. Furthermore as the tube does not need to be stretched for correct operation it is believed that the tube will be able to exhibit longer life characteristics.

Figures 3-5 of the drawings show a more detailed embodiment of the pump. In this embodiment body 18 is formed by a cylinder block 18a and a cover 18b which is attachable to the cylinder block via threaded fasteners 22 or other fasteners such as quick release clips, clamps or the like.

In the preferred form of the invention low restriction fittings 23 and 24 respectively form the inlet 11 and outlet 12. These low restriction fittings allow full rotation so as to suit different installation requirements.

In the preferred form the inlet fitting 23 is of larger bore diameter. Cover 18b effectively forms a removable anvil which not only clamps the tube 10 and fittings 23 and

24 in position but also, by being readily removable, provides for easy replacement of tube 10. As illustrated pistons 17c of pinch element 16 engage with a connector or compression plate 19 while piston 17b of pinch element 15 is coupled to a substantially V-shaped cross section engagement member 25.

In the manner described earlier piston 17a of pinch element 14 has an engagement member 26 through which tube 10 is threaded. Located above tube 10 and engagement member 26 are engagement surfaces 27 (Figure 3). When pinch element 14 is in the rest position the tube 10 is constricted and is unconstricted when the pinch element is operative. Thus when the pump is in the rest position piston 17a closes tube 10 so as to prevent siphoning and therefore back-flow. A bias spring (not shown) is preferably engaged between the underside of engagement member 26 and recess 33 in cover 18b to force the engagement member into the constricting (closed) position.

Air passages 21 (not shown in Figures 3-5) are coupled to transfer passages 28 in the upper surface 32 of body 18a as shown in Figure 5. This upper surface 32 and hence transfer passages 28 are covered by a manifold plate 34. A compressed air source is coupled via air inlet 43. In one form of the invention the manifold plate can be permanently connected to the cylinder block 18a. Bores 14, 15 and 16 of manifold plates 34 connect into respective ones of transfer passages 28. These bores mate with openings (not shown) in the base of solenoids 29, 30 and 31. Accordingly operation of the solenoid valve connects the corresponding piston(s) of pinch elements 14, 15 and 16 to either the source of compressed air or a vent to atmosphere whereupon the piston moves to compress the tube or allow the flow passage in the tube to open. Thus for each set of bores 14, 15 and 16 one bore is coupled to the respective air passage(s) 21 of the pinch element 14, 15 and 16, one bore is coupled to air inlet 43 and one is coupled to the vent. In operation the corresponding solenoid valve opens and closes the other bores so as to couple the air passage 21 to the source of compressed air or to vent depending on whether the respective piston 21 is to close or open the tube 10.

Control of compressed air into the various transfer passages via controlled operation of solenoid valves 29, 30 and 31 and hence to the air passages 21 causes the pistons 17a, 17b and 17c to operate in the sequence of steps as previously described. The solenoid operated pneumatic valves 28, 29 and 30 can, for example, be Burket type 375 pneumatic valves. These are fastened to the manifold plate 34 by fasteners 36. Also mounted to manifold plate 34 -is a cover 37 within which is mounted a PCB 38 having switches 39 and an L.E.D. counter/calibration display 40. To complete the pump a further cover 41 is provided ^"to cover the tops of the connector plugs 35 attached to the spade terminals on the tops of the solenoid valves. cover 37 and 41 can be combined into a single cover unit.

In the illustrated form of this embodiment of the invention two of switches 39 can be used to increase or decrease the cycle rate so as to increase or decrease (as the case may be) the output of the pump per unit time. The increased/decreased rate can be selected by reference to a readout appearing on display 40.

A further switch 39 can provide a calibration function where the pump operates for a pre-determined period. The user can measure (volumetrically) the total output over the period of time and work out the output of the pump for the selected rate of operation.

Another of the switches 39 can be a reset button to reset the display 40 when the control circuitry is operative to give a pre-selected period of operation or number of cycles. The control circuit can include a manual on/off switch, an automatic sensor switch (ie the pump switches on or off dependent on sensing an external event or operation of related equipment) or a pressure switch. Other activating means will be apparent to those skilled in the art.

To maintain operator/user selected operating parameters in the event of a power down (either due to temporary power feed problems or due to the pump being switched off) the control circuit includes an EEPROM to store the selected operating parameters.

The pump as illustrated in Figures 3-5 is of a simple and straight forward construction as well as being of aesthetically pleasing appearance.

The pump is self-contained thus a number of pumps can be clipped together to form a bank of pumps as shown in Figure 5. To this end the pump is preferably formed with an openable air outlet (not shown) which can be opened and mated with the air inlet 43 of the next adjacent pump. As a consequence a single air supply connected to the air inlet 43 of one pump can feed all pumps in the bank.

In one form of the invention clips 44 can be used to simply clip the pumps together into a bank as shown in Figure 5. The pump according to the invention can be used in many different applications and widely diverse fields. It has application in the medical, pharmaceutical, food, beverage, biotechnological, chemical and agricultural industries. The pump provides a simple means of dispensing a regulated dose of liquid from a non pressurised source.

Features of the pump are:-

1. Food Safe.

2. Easy to clean.

3. Self Priming.

4. Low Cost.

5. Reversible. 6. No seals or lubrication required.

7. Can be operated dry without damage.

8. High isolation between input and output.

9. Very low parts count in pump assembly.

The pump is open to modification. For example, it has been found that tube 10 has a favourable service life which equates to that of the pistons 17 and sealing rings 20. Thus body 18, tube 10 and the pistons could be of a disposable form whereupon the entire unit could be simply replaced. In another form of the invention the pinch elements can be formed by cams or eccentrics mounted on a shaft which is driven directly or indirectly by a motor. The axis of rotation of the shaft will generally be parallel to the longitudinal axis of tube 10. Accordingly the cams/eccentrics will engage with the tube to pinch the tube in the sequence described herein to achieve the pumping action.

Other means of controlling pinch elements can be employed or will be apparent to those skilled in the art and fall within the scope of the invention as defined in the following claims.

Claims

1. A pump comprising a flexible conduit (10) one end (11) being coupleable to a fluid source and the other end (12) forming or being coupleable to an outlet, there being pinching means (14, 15 and 16) spaced apart longitudinally of the conduit (10), said pinching means being arranged to successively pinch and release the conduit to result in a pulsed movement of fluid from said one end (11) to said other end (12) .

2. The pump according to Claim 1 wherein there are three pinch means which form an inlet pinch element (14), an outlet pinch element (15) and a discharge pinch element (16).

3. The pump according to Claim 2 wherein the volume of fluid discharged from the conduit (10) during each cycle of operation is substantially the volume contained in that part of the conduit compressed by the discharged pinch element (16).

4. The pump according to Claim 2 or 3 wherein one pinch element (14) is arranged to pinch closed conduit (10) in the inoperative state of the pump.

5. The pump according to Claim 2, 3 or 4 wherein the operative component of each of the pinch elements is a linear actuator (17a, 17b and 17c), there being a control means (29, 30 and 31) for controlling movement of the linear actuator.

6. The pump according to Claim 5 wherein each linear actuator is pneumatic piston (17) which engages with said conduit (10) .

7. The pump according to Claim 6 wherein the piston (17) engages with the conduit (10) via an engagement element (19, 25 or 26).

8. The pump according to Claim 5, 6 or 7 wherein the discharge pinch element (16) comprises two linear actuators (17c) coupled to a compression plate (19) engaged or engageable with the conduit (10).

9. The pump according to any one of Claims 5 to 8 wherein the control means is a pneumatic electrically operated solenoid valve (29, 30 or 31) which controls the coupling of air pressure to the respective linear actuator (17a, 17c or 17b) with which the solenoid valve is associated.

10. The pump according to Claim 5 wherein the linear actuators (17a, 17b or 17c) and conduit (10) are located in a body section (18) which is removable for replacement as a unit.

11. The pump according to Claim 10 wherein the body (10) is mounted to a manifold (34) with which is mounted control means (29, 30 and 31) for controlling movement of the linear actuators (17a, 17b and 17c).

12. The pump according to Claim 11 wherein the control means includes electrically operated solenoid valves (29,

30 and 31) which control the coupling of air pressure to the respective linear actuators (17a, 17b and 17c).

13. The pump according to Claim 2 wherein the operative component of each pinch element is a cam or eccentric coupled to drive means.

14. The pump according to Claim 2 wherein movement of the pinch elements (14, 15 and 16) is controlled by control means operable such that in a pumping cycle the inlet element (14) releases the conduit (10) followed by release of the discharge element (16) whereupon the inlet element (14) pinches the conduit (10) closed followed by the outlet element (15) releasing the conduit (10) followed by the discharge element (16) pinching the conduit (10) closed whereupon the outlet element (15) pinches the conduit (10) closed to complete the pumping cycle.