GB2211557A - Low drag peristaltic pump - Google Patents

Abstract

A nip is created in a resilient tube 16 by compressing the tube between a housing and a roller 20. The roller is rotatable about its own axis only so that the "nip" magnitude is stationary and the rotation of the roller acting on the tube at the nip volume forces fluid along the tube. The pump shown includes five driven rollers 20 spaced around the housing to define five stationary nips. The rollers are each coupled by a friction drive to a single central drive roller 18 so that the rollers 20 are driven simultaneously in the same direction. The housing has a removable lid (22, Fig 1) and the lid, housing and rollers define the nip at which uncontrolled deformation of the resilient tube 16 is limited in order to maximise pumping action, fluid flow rate and fluid pressures developed by the pump. <IMAGE>

Description

LOW DRAG PERISTALTIC PUMP The present invention relates to a peristaltic pump and particularly, but not exclusively, to a low drag peristaltic pump for pumping biological fluids and the like which are susceptible to degradation by heat.

A peristaltic pump should satisfy a number of desirable criteria, in addition to being sterilizable and readily assembled. The pump should be operable to pump fluid at relatively high flow rates at high pressures, and the drag on tubes carrying fluid should be minimised to minimise heat created by friction which can degrade fluids being pumped. In addition, uncontrolled deformation of the tubes points of compression or "nips" should be minimised to maximise the peristaltic pumping action.

Existing high flow peristaltic pumps consist of a housing for accommodating one or more tubes carrying fluid to be pumped. The housing defines a generally circular cavity which accommodates one or more cylindrical rollers which are rotatable about the central axis of the circular cavity. The housing and the curved surface of each of the rollers define a "nip" on the tube, and as each roller rotates around the cavity the "nip" also rotates and segments, or "slugs", of fluid defined by the length of tube between each "nip" are forced through the tube.

However, with such arrangements each roller moves along the outer surface of the tube and considerable friction or "drag" is created between the tube and each roller. In order to achieve high fluid flow rates at relatively high pressures the rotational speed of the rollers has to be increased. However, this creates increased drag or friction which results in increased heat generation. This is a particular problem when biological fluids such as blood and dialysate are being pumped because they can be degraded by the heat with potentially harmful effects.

An object of the present invention is to obviate or mitigate at least one of the aforesaid problems associated with existing peristaltic pumps.

This is achieved by providing a low drag peristaltic pump in which a nip is created in a resilient tube by compressing the tube between the housing and a roller.

The roller is rotatable about its own axis so that the "nip" magnitude is stationary and the rotation of the roller acting on the tube at the nip volume forces fluid along the tube.

In one embodiment, the pump includes a plurality of rollers spaced around the housing to define a plurality of stationary nips. The rollers are each coupled by a friction drive to a single central drive roller so that the rollers are driven simultaneously in the same direction. The housing has a removable lid and the lid, housing and rollers define the nip at which uncontrolled deformation of the resilient tube is limited in order to maximise pumping action, fluid flow rate and fluid pressures developed by the pump.

In another embodiment the rollers are coupled by a gear drive and each nip roller and the drive roller have gear teeth for providing meshing engagement to effect said gear drive.

Accordingly, in one aspect of the present invention there is provided a peristaltic roller pump comprising a pump housing and at least one rotatable roller disposed in the pump housing, said housing having a cavity for receiving at least one resilient tube carrying a fluid to be pumped, said housing and said roller being arranged to compress said tube to define a nip, the roller surface contacting said tube and, the roller surface housing defining a nip volume within the tube over the length of contact of said roller surface, said nip magnitude and position being substantially constant relative to the tube, the arrangement being such that, in use, rotation of said roller about its own axis over said contact surface causes fluid in said tube to be forced along said tube.

Preferably, a plurality of rollers are spaced around the internal walls of said pump housing cavity, each of said rollers and the housing defining a nip.

Conveniently, there are five driven rollers spaced around the internal walls of said pump housing.

Preferably also, said rollers are rotated by a common drive means which drives all rollers simultaneously and in the same direction.

Preferably also, said common drive means are provided by a friction drive, said friction drive consisting of at least one O-ring disposed around the periphery of a central drive roller between said drive roller and the driven rollers.

Alternatively, said drive means are provided by a gear drive arrangement, and said common drive roller and said driven rollers having portions adapted to intermesh to provide said gear drive arrangement.

Preferably also, each driven roller is secured in said cavity by a guide plate which accommodates each of said driven rollers being located in said cavity, said guide plate permitting each roller to be rotated about its own axis.

Preferably also, said housing and said roller define tube confining means to minimise unrestricted tube deformation at each nip. Conveniently, fluid temperature control means can be provided to vary the temperature of said fluid by introducing a temperature variable fluid into said pump body so that the viscosity of the liquid being pumped can be varied, and the fluid in said tubes can be circulated at a suitable rate.

These and other aspects of the present invention will become apparent in the following description when taken in combination with the accompanying diagrams in which: Fig. 1 is an exploded view of a peristaltic pump in accordance with an embodiment of the invention; Fig. 2 is a plan view of an assembled pump with the upper casing removed for clarity; Fig. 3 is a cross-sectional elevation of the assembled pump, taken along lines 3-3 in Fig. 2; Fig. 4 is an enlarged plan view of one of the "nips" shown in Fig. 2; Fig. 5 is an end elevation of the embodiment of the assembled pump; and Fig. 6 is part of an end elevation of an alternative embodiment of a pump similar to that shown in Figs. 1-4 Reference is first made to Fig. 1 which shows a low drag peristaltic pump generally indicated by reference numeral 10, comprising a housing 12 which is generally circular in plan which defines a circular cavity 14 for receiving two resilient tubes 16 (shown in part) which carry fluid to be pumped and a roller drive arrangement consisting of a central roller 18 and five driven rollers 20 which compress the resilient tubes 16 to define a plurality of stationary nips, so that when the central roller 18 rotates the driven rollers rotate to pump fluid along the tubes with minimal heat generation as will be described.

The pump 10 includes a lid 22 which has four apertures 24 for receiving threaded rods 26 to position the lid 22 on the housing 12. The lid 22 is secured in place by four wing nuts 28. A guide plate 30 is also provided for orienting the central roller 18 and the drive rollers 20 with respect to the interior of the pump housing for maximising pumping effectiveness as will be described.

Reference is now made to Fig. 2 which is an assembled pump of Fig. 1 with lid 22 removed in the interest of clarity. The five rollers 20 are disposed around their central roller 18 in cavity 14. The central roller 18 rotates anti-clockwise as shown around the central roller axis 32. Rotation of central roller 18 causes a clockwise rotation of driven rollers 20 due to friction drive by three spaced O-rings mounted on the central roller 18 as will be described.

Reference is now made to Fig. 3 which is a cross-sectional elevation of the assembled pump and which shows of one of the five "nips" 34 around the cavity 14.

The tube 16 is shown disposed on the housing wall 36 in both the compressed and uncompressed conditions. Each rotatable or driven roller 20 and the housing 12 defines the I' nip" 34 at which point the tube 16 is compressed to have a lumen of smaller cross-section. At the "nips" fluid is pumped through the tubes as will be described.

In addition the housing 12, the lid 22 and the roller 20 define tube confining means which limit the deformation of tube 16 at each "nip" 34 which would otherwise limit the effect of the peristaltic pumping action.

Disposed around the central drive roller 18 are four spaced O-rings 38. These O-rings engage with each of the five driven rollers 20 and provide sufficient friction to rotate the driven rollers in a clockwise direction when the central drive roller 18 rotates in an anti-clockwise direction around the central roller axis 32.

Reference is now made to Fig. 4 which is an enlarged plan view of one of the "nips" 34. The roller 20 compresses the tube 16 along the length of their contact, and the narrowest tube portion is the nip magnitude. The length of contact defines a "nip volume" 40 shown as the shaded area in Fig. 4. As the roller 20 rotates clockwise as shown the fluid in the tube 16 is pumped through tube 16. Because the nip is stationary relative to the tube there is local drag on the tube surface, but only on the contact surface which is small in comparison to the drag with existing devices, thus there is minimal heat generation because of friction created during operation of the pump.The liquid is moved in the tube by the drag effect between the roller and the contacted surface whereby the tube at that location is alternately dragged partly round with the roller surface and is then released returning to its original position because of the resistance in the tube. As the tube is dragged fluid is squeezed along the tube in the direction of rotation.

Reference is now made to Figs. 5 and 6 of the drawings. Fig. 5 shows an end elevation of the pump in Figs. 1 to 4 which is a low drag peristaltic pump 10 as described with two tubes 16 containing fluid to be pumped. Another embodiment of a pump shown in part in the end elevation of Fig. 6. This is a low drag peristaltic pump 10 of a similar construction to that shown in Figs. 1 to 5 but with four tubes 16 accommodated therein.

Several modifications can be made to the structures hereinbefore described without departing from the scope of the invention. Firstly the rollers could be driven individually or by gears instead of the friction drive.

Also, a single or double tube could run round the entire cavity instead of half of the cavity as described above, in fact, any number of tubes could be accommodated around the cavity as long as "nips" are effective upon each tube. The dimensions, the rollers and the tubes may be altered to give higher or lower flow rates of the fluid being pumped and the rollers can be adjusted using spacers or sleeves to vary the nip magnitude. Also, a temperature controlled fluid may be introduced into the pump body containing the rollers to vary the temperature and hence viscosity of the fluid being pumped so that the fluid can be circulated at a suitable rate.

Advantages associated with the present embodiments are that the peristaltic pump generates less heat due to minimised drag of the rotating rollers. The peristaltic pump contains tube confining means to limit the deformation of the tubes at each "nip" so that greater flow rates and pressures can be achieved without excessive heat generation.

Claims (11)

1. A peristaltic roller pump comprising a pump housing with at least one rotatable roller disposed in the pump housing, said housing having a cavity for receiving at least one resilient tube carrying a fluid to be pumped, said housing and said roller being arranged to compress said tube to define a nip, the roller surface contacting said tube, the roller surface and housing defining a nip of the tube over the length of contact of said roller surface, the nip magnitude and position being substantially constant relative to the tube, the arrangement being such that, in use, rotation of said roller about its own axis over said contact surface causes fluid in said tube to be forced along said tube.

2. A peristaltic roller pump as claimed in claim 1 wherein a plurality of rollers are spaced around the internal walls of said pump housing cavity, each of said rollers and the housing defining a nip.

3. A peristaltic roller pump as claimed in claim 2 wherein there are five driven rollers spaced around the internal walls of said pump housing.

4. A peristaltic roller pump as claimed in claims 2 or 3 wherein said rollers are rotated by a common drive means which drives all rollers simultaneously and in the same direction.

5. A peristaltic roller pump as claimed in claim 4 wherein said common drive means is provided by a friction drive, said friction drive consisting of at least one O-ring disposed around the periphery of a central drive roller between said drive roller and the driven rollers.

6. A peristaltic roller pump as claimed in claim 4 wherein said drive means is provided by a gear drive arrangement.

7. A peristaltic roller pump as claimed claim 6 wherein a common drive roller and said driven rollers have portions adapted to intermesh to provide said gear drive arrangement.

8. A peristaltic roller pump as claimed in any preceding claim wherein each driven roller is located in said cavity by a guide plate which accommodates each of said driven rollers in said cavity, said guide plate permitting each roller to be rotated about its own axis.

9. A peristaltic roller pump as claimed in any preceding claim wherein said housing and said roller define tube confining means to minimise unrestricted tube deformation at each nip.

10. A peristaltic roller pump as claimed in any preceding claim wherein fluid temperature control means are provided to vary the temperature of said fluid by introducing a temperature variable fluid into said pump body so that the viscosity of the liquid being pumped can be varied, and the fluid in said tubes can be circulated at a suitable rate.

11. A peristaltic roller pump substantially as hereinbefore described with reference to Figs. 1 to 5 or 6 of the accompanying drawings.