WO2024133665A1

WO2024133665A1 - A peristaltic pump

Info

Publication number: WO2024133665A1
Application number: PCT/EP2023/087243
Authority: WO
Inventors: Fokke Patrick VAN DER SPAN; Tiemen Rudolf POSTMA
Original assignee: Watson-Marlow Bredel B.V.
Priority date: 2022-12-23
Filing date: 2023-12-21
Publication date: 2024-06-27
Also published as: GB2625831A

Abstract

There is disclosed a peristaltic pump, comprising: a resilient tube having a primary tube chamber and an auxiliary tube chamber which are integrally formed with one another, wherein the primary tube chamber is configured to receive a working fluid and the auxiliary tube chamber is configured to receive the working fluid upon rupture of a wall of the primary tube chamber; and a sensor configured to detect working fluid in the auxiliary tube chamber. There is also disclosed a resilient tube for a peristaltic pump, comprising: a primary tube chamber and an auxiliary tube chamber which are integrally formed with one another, wherein the primary tube chamber is configured to receive a working fluid and the auxiliary tube chamber is configured to receive the working fluid upon rupture of a wall of the primary tube chamber.

Description

A PERISTALTIC PUMP

Field of Invention

The present disclosure relates to a peristaltic pump, and a resilient tube for a peristaltic pump.

Background

In a peristaltic pump, the fluid being pumped flows through and is completely contained within a flexible tube. In use, the tube is squeezed between a shoe (or any other pressing member, such as a roller) and a track on an arc of a circle, creating a seal at the point of contact. As the shoe advances along the tube, the seal also advances. After the shoe has passed, the tube returns to its original shape, creating a partial vacuum which is filled by fluid drawn from the suction port.

Before the shoe reaches the end of the track, a second shoe compresses the tube at the start of the track, isolating a packet of fluid between the compression points. As the first shoe leaves the track, the second continues to advance, expelling the packet of fluid through the pump’s discharge port. At the same time, a new partial vacuum is created behind the second shoe into which more fluid is drawn from the suction port.

During operational life of the pump, the flexible tube undergoes repeated cycles of compression and relaxation, eventually leading to failure due to fatigue. Whilst failure of the tube is a common problem, the failure occurs unexpectedly and without any prior indication. Statistical distributions can be used to model the failure mechanism to try and predict the expected time of failure of a tube. However, the values obtained from these models typically have a large variance, such that the expected time window for failure is very wide, in the order of weeks or months of operating time of the pump. Failure could occur unexpectedly at any point within this window.

Failure of the tube can be mitigated by performing regular preventative maintenance of the pump, including replacing the tube before the end of its typical life. However, this means that tubes are often replaced without being fully used to the end of their operational life, leading to wastage. Preventative maintenance can therefore lead to additional cost, which is undesirable. It is therefore desired to provide a tube for a peristaltic pump which addresses at least some of the aforementioned problems.

Summary

In accordance with a first aspect of the invention there is provided a peristaltic pump, comprising: a resilient tube having a primary tube chamber and an auxiliary tube chamber which are integrally formed with one another, wherein the primary tube chamber is configured to receive a working fluid and the auxiliary tube chamber is configured to receive the working fluid upon rupture of a wall of the primary tube chamber; and a sensor configured to detect working fluid in the auxiliary tube chamber.

The auxiliary tube chamber may extend only partially around the circumference of the primary tube chamber.

The resilient tube may comprise two auxiliary tube chambers disposed at diametrically opposed positions from the primary tube chamber.

The auxiliary tube chamber may surround the primary tube chamber.

The resilient tube may comprise a plurality of primary tube chambers arranged in parallel, wherein adjacent primary tube chambers are connected such that an auxiliary tube chamber is formed between adjacent primary tube chambers.

The adjacent primary tube chambers may be connected by resilient members extending between the respective walls of adjacent primary tube chambers to define the auxiliary tube chamber.

The sensor may be located within the auxiliary tube chamber.

The sensor may be configured to detect a change in the pressure of the working fluid in the resilient tube.

The sensor may comprise one or more of an optical sensor, an ultrasonic sensor, an infrared sensor, a conductivity sensor and a radar sensor. In accordance with a second aspect of the invention there is provided a resilient tube for a peristaltic pump, comprising: a primary tube chamber and an auxiliary tube chamber which are integrally formed with one another, wherein the primary tube chamber is configured to receive a working fluid and the auxiliary tube chamber is configured to receive the working fluid upon rupture of a wall of the primary tube chamber.

The tube may comprise two auxiliary tube chambers disposed at diametrically opposed positions from the primary tube chamber.

The auxiliary tube chamber may surround the primary tube chamber.

Brief Description of the Drawings

Exemplary embodiments will now be described, by way of example only, with reference to the following drawings, in which:

Figure 1 is a cross section through a prior art peristaltic pump;

Figure 2 is a cross section of an example resilient tube according to an embodiment of the invention;

Figures 3 and 4 are cross sections through an example peristaltic pump including the resilient tube of Figure 2, which is shown in a relaxed state in Figure 3 and in a compressed state in Figure 4; Figure 5 is a cross section of an example resilient tube according to another embodiment of the invention;

Figure 6 is a perspective view of an example resilient tube according to another embodiment of the invention.

Detailed Description of the Invention

Figure 1 shows a prior art peristaltic pump 1. The peristaltic pump 1 comprises a pump body 2 and a rotor 6 which is rotatably mounted within the pump body. The rotor 6 is provided with a central shaft (not shown) and a plurality of shoes 8 which extend radially outward from the central shaft. Each of the plurality of shoes 8 is provided at the same radial distance from the central shaft but are offset from one another circumferentially. In other examples, the shoes 8 may be replaced with rollers or any other type of pressing member. The rotor 6 is rotated about the central shaft by a drive unit.

The pump 1 further comprises an arcuate track 4 partially extending around the circumference of the rotor 6. The length of the track 4 corresponds to the swept volume of the shoes 8 as the rotor 6 rotates. The pump 1 further comprises a compressible tube 10 disposed between the shoes 8 and the track 4. The tube 10 comprises an internal bore 14 which is defined by a tube wall 12. In operation of the pump, a working fluid to be pumped flows through the internal bore 14 of the tube 10. The tube 10 has a suction port from which fluid is drawn and a discharge port from which fluid is expelled.

In operation of the pump 1 , the rotor 6 is driven by a drive unit. As the rotor 6 rotates, a first shoe 8 compresses the tube 10 in a radial direction, creating a seal at the point of contact. As the rotor 6 continues to rotate, the first shoe 8 advances along the tube 10 and the seal also advances. After the shoe 8 has passed, the tube 10 relaxes and returns to its original shape, creating a partial vacuum which is filled by fluid drawn from the suction port.

Before the first shoe 8 reaches the end of the track 4, a second shoe 8 compresses the tube 10 at the start of the track as the rotor rotates. This traps a packet of fluid within the tube 10. As the first shoe 8 leaves the track, the second shoe 8 continues to advance, expelling the packet of fluid through the discharge port. At the same time, a new partial vacuum is created behind the second shoe 8 into which more fluid is drawn from the suction port.

As the pump 1 continues to operate, the tube 10 undergoes repeated cycles of compression and relaxation through the action of the shoes. Over time, this repeated cyclic loading can lead to fatigue failure. Fatigue failure tends to occur by the formation of cracks in, and eventual rupture of, the tube wall. These cracks tend to be localised at the regions of the tube wall which experience the greatest stress in use, which are the regions of the tube wall which lie on a line perpendicular to the direction of compression. Eventual rupture of the tube is likely to occur at these regions, known as the ‘cheek’ regions of the tube. When rupture occurs, fluid can escape from the tube and the pump can no longer operate safely. Fatigue failure occurs suddenly and without warning.

Figure 2 shows a cross section of an example resilient tube 20 for a peristaltic pump according to an embodiment of the invention. The tube 20 comprises a primary tube chamber 22 and an auxiliary tube chamber 24 formed integrally with one another. In this example, the tube 20 comprises two auxiliary tube chambers 24 extending at diametrically opposite positions from the primary tube chamber 22. In other examples, the tube 20 may have only a single auxiliary tube chamber or more than two auxiliary tube chambers. In this example, the primary tube chamber 22 has a generally circular cross section. The cross section of the tube 20 may be substantially the same along the length of the tube 20.

The tube 20 has an external wall 28 defining its external profile. The tube further comprises an inner wall 26. The inner wall 26 delimits the primary tube chamber. Each auxiliary tube chamber 24 is delimited by portions of the external wall 28 and the inner wall 26. The primary tube chamber 22 and the auxiliary tube chambers 24 are separated by the inner wall 26. The external wall 28 defines a lozenge or rhombus shape and the inner wall 26 defines a circle therewithin. Each auxiliary tube chamber 24 is formed between that circle and a vertex of the external wall 28. Each auxiliary tube chamber 24 only extends partially around the circumference of the primary tube chamber 22. In particular, the auxiliary tube chambers 24 only surround the cheek regions of the primary tube chamber 22. The tube 20 is formed from a resilient material. This allows the tube 20 to be compressed by the shoes of the rotor in use and regain its shape when the shoes have passed. For example, the tube 20 may be formed from a thermoplastic or an elastomeric material. In further examples, the tube 20 may be formed from a thermoplastic polyurethane (TPU) material. The tube 20 may be formed using an extrusion process. Alternatively, the primary tube chamber 22 and the auxiliary tube chamber 24 may be formed in separate processes and subsequently attached to one another, for example using adhesives, or by welding.

Figure 3 shows an example peristaltic pump 100 which corresponds to the pump 1 described previously but utilising the tube 20 instead of the conventional tube 10.

As shown, the tube 20 further comprises a sensor 29. In this example, a sensor 29 is located in each of the auxiliary tube chambers 24. In other examples, a sensor 29 may be located in only one of the auxiliary tube chambers 24. The sensor 29 is configured to detect the presence of fluid in the auxiliary tube chambers 24. The sensor 29 may be any sensor suitable for this purpose, for example an optical sensor, an ultrasonic sensor, an infrared sensor, a radar sensor, a conductivity sensor or a pressure sensor. In other examples, the or each sensor 29 may be external to the tube 20. For example, an optical sensor may be arranged adjacent to the tube 20 (e.g. on the pump body) with one or both of the auxiliary tube chambers 24 in its field of view. In other examples, the or each sensor 29 may be external to the auxiliary tube chambers 24, but still formed as part of the tube 20 or connected to the tube 20. For example, the or each sensor 29 may be overmolded onto or otherwise attached to the tube 20 or provided in a separate cavity provided on the tube 20 in a position which is adjacent to the auxiliary tube chambers 24. The sensor 29 may be connected to a control module.

The or each sensor 29 may be provided on the pump 100 itself such that it does not need to be replaced with the tube 20. In such an arrangement, the or each sensor 29 may be engaged with the tube 20 during installation of the tube 20 in the pump 100 such that it is located within one of the auxiliary tube chambers 24.

In normal operation of the pump 100, a working fluid to be pumped flows through the primary tube chamber 22. The auxiliary tube chambers 24 remain empty (i.e., the working fluid is not present) in normal operation of the pump 100. Figure 4 shows the tube 20 in a compressed state. When the shoe 108 compresses the tube 20, the tube 20 is pinched between the track 104 and the shoe 108. This causes the primary tube chamber 22 to close, creating a seal at the point of contact. The auxiliary tube chambers 24 may be compressed but remain open during compression of the primary tube chamber 22.

As described previously, during the lifetime of operation of the pump 100, the resilient tube 20 is likely to fail by fatigue caused by the repeated cycles of compression and relaxation. Failure of the tube 20 is likely to occur in the cheek region of the primary tube chamber 22, as it experiences the most stress during use. In particular, the internal wall 26 is likely to crack and eventually rupture. Rupture of the internal wall 26 on either side of the primary tube chamber 22 causes the working fluid to enter the respective auxiliary tube chamber 24. The or each sensor 29 is configured to detect when fluid enters one of the auxiliary tube chambers 24. This may be detected by detecting presence of the fluid within the auxiliary tube chamber 24, for example where the sensor 29 is an optical sensor, an ultrasonic sensor, an infrared sensor, a conductivity sensor or a radar sensor. Alternatively, the presence of fluid within the auxiliary tube chamber 24 may be detected indirectly. For example, where the sensor 29 is a pressure sensor, fluid may be deemed to have entered the auxiliary tube chamber 24 based on a change in the pressure within the auxiliary tube chamber 24. Alternatively, fluid may be deemed to have entered the auxiliary tube chamber 24 based on a change in the pressure or flow rate within the primary tube chamber 22 itself or based on a change in load on the motor of the pump 100.

As described, the sensor 29 may be connected to a control module. The control module may be configured to alert an operator when fluid is detected within one of the auxiliary tube chambers 24 by the sensor 29.

Despite the inner wall 26 having failed, the pump 100 can continue to operate (at least for a short period)_with working fluid now flowing through one or more of the auxiliary tube chambers 24 instead of the primary tube chamber 22. The auxiliary tube chambers 24 ensure that the tube 20 remains sealed and the working fluid cannot escape from the tube 20. This enables the pump 100 to continue to operate safely. By detecting when fluid enters one of the auxiliary tube chambers, an operator of the pump can be alerted to the failure of the primary tube chamber 22, and have sufficient time to take appropriate action, such as replacement of the tube, before any fluid escapes from the tube. The pump can therefore operate with minimal downtime required for maintenance.

Alternatively, the control module may automatically shut down the pump 100 when fluid is detected within one of the auxiliary tube chambers 24. It may be expected that after failure of the primary tube chamber 22, the flow rate of the pumped fluid may reduce and so it may be necessary to shut down the pump 100 where the flow rate of the fluid is important (e.g., in metering or dosing applications). Further, the auxiliary tube chambers 24 may have a lower wall thickness and therefore lower pressure capability than the primary tube chamber 22, such that it is necessary to quickly shut down the pump 100 when fluid is detected within one of the auxiliary tube chambers 24.

Figure 5 shows a cross section through an example resilient tube 30 according to another embodiment of the invention. The tube 30 comprises two lumens 31 a, 31 b. Each lumen 31a, 31 b comprises a primary tube chamber 32a, 32b defined by a primary tube wall 36a, 36b. Each lumen 31a, 31b is provided with an auxiliary tube chamber 34a, 34b formed integrally with the respective primary tube chamber 32a, 32b. Each auxiliary tube chamber 34a, 34b is defined by an auxiliary tube wall 33a, 33b extending from the respective primary tube wall 36a, 36b. Each auxiliary tube wall 33a, 33b extends around a cheek region of the respective primary tube wall 36a, 36b to form the respective auxiliary tube chamber 34a, 34b. The auxiliary tube chambers 34a, 34b are disposed at opposing lateral sides of the primary tube chambers 32a, 32b. In this example, the auxiliary tube wall 33a, 33b has a semi-circular cross section.

The lumens 31a, 31b are connected by an intermediate auxiliary tube chamber 34c which is integrally formed with both primary tube walls 36a, 36b. Two resilient members 38 extend between the outer surface of the tube walls 36a, 36b, such that the intermediate auxiliary tube chamber 34c is formed by the space between the two resilient members 38 and the tube walls 36a, 36b. The intermediate auxiliary tube chamber 34c extends between opposing proximal sides of the primary tube chambers 32a, 32b and thus the opposing cheek regions of the two lumens 31a, 31b.

The tube 30 is for use in a multichannel (e.g., dual channel) peristaltic pump. For example, the pump may have two sets of shoes on a single rotor or two discrete rotors which are angularly offset from one another. Alternatively, the pump may have two separate tracks which are angularly offset from one another. Like the example tube described with reference to Figs 2-4, the tube 30 of Figure 5 is also formed from a resilient material. This allows each lumen 31a, 31 b of the tube 30 to be compressed by the shoes of the rotor in use and regain its shape when the shoes have passed. For example, the tube 30 may be formed from a thermoplastic or an elastomeric material. In further examples, the tube 30 may be formed from a TPU material. The tube 30 may be formed using an extrusion process. Alternatively, the lumens 31a, 31 b, the auxiliary tube chambers 24a, 24b, and the resilient members 38 may be formed in separate processes and subsequently attached to one another, for example using adhesives, or by welding.

In normal operation, the working fluid to be pumped flows through the primary tube chambers 32a, 32b, and the auxiliary tube chambers 34a, 34b and the intermediate auxiliary tube chamber 34c remain empty.

Over time, the tube walls 36a, 36b are likely to fail due to fatigue, causing rupture in the cheek regions of the tube walls 36a, 36b. If rupture occurs in the tube wall of either of the two lumens 31a, 31 b, the fluid will enter one or more of the respective auxiliary tube chambers 34a, 34b and the intermediate auxiliary tube chamber 34c. The tube 30 comprises sensors 39 configured to detect when fluid has entered either one of the auxiliary tube chambers 34a, 34b, or the intermediate auxiliary tube chamber 34c. In this example, sensors 39 are located in each of the auxiliary tube chambers 34a, 34b and the intermediate auxiliary tube chamber 34c. In other examples, sensors 39 may be located in only one or some of the auxiliary tube chambers 34a, 34b and the intermediate auxiliary tube chamber 34c. The sensors 39 may be any sensor suitable for detecting the presence of fluid within the auxiliary tube chambers 34a, 34b or the intermediate auxiliary tube chamber 34c. For example, the sensors 39 may be one or more of an optical sensor, an ultrasonic sensor, an infrared sensor, a radar sensor or a pressure sensor, as described with reference to the tube 20.

The sensors 39 may be connected to a control module of the pump which may be configured to alert an operator of the pump to a status of operation of the pump or to automatically shut down the pump when fluid is detected within one of the auxiliary tube chambers 34a, 34b, 34c, as described with reference to the tube 10. Figure 6 shows an example resilient tube 40 according to another embodiment of the invention. The tube 40 comprises four lumens 41 a-41 d. Each lumen 41 a-41 d comprises a primary tube chamber 42a-42d defined by an internal wall 46a-46d. Surrounding and formed integrally with the four lumens 41 a-41 d is an external wall 48. The external wall 48 defines the outer profile of the tube 40. The four lumens 41 a-41 d are spaced apart in parallel within the space formed by the external wall 48. An auxiliary tube chamber 44a-44d is formed either side of each lumen 41 a-41 d. For the two outermost lumens 41a, 41 d located at the outer edges of the tube 40, an auxiliary tube chamber 44a, 44e is formed by the space between their respective internal wall 46a, 46d and the external wall 48. The outermost lumens 41a, 41 d also have an auxiliary tube chamber 44b, 44d formed between their respective internal wall 46a, 46d, the external wall 48, and the internal walls 46b, 46c of adjacent lumens 41 b, 41c. For the two innermost lumens 41 b, 41c, which are located towards the centre of the tube, auxiliary tube chambers 44b-44d are formed either side of the innermost lumens 41 b, 41c by the space formed by their respective internal wall 46b, 46c, the external wall 48, and the internal walls 46a-46d of adjacent lumens 41 a-41 d. As a result, for each lumen 41 a-41 d, auxiliary tube chambers 44a-44e are disposed at diametrically opposed positions from their respective inner wall 46a-46d, so that the cheek regions of each lumen 41 a-41 d are covered by an auxiliary tube chamber 44a-44e.

The tube 40 is for use in a multichannel (e.g., four channel) peristaltic pump. For example, the pump may have four sets of shoes on a single rotor or four discrete rotors which are angularly offset from one another. Alternatively, the pump may have four separate tracks which are angularly offset from one another.

As for the example tubes described in the previous embodiments, the tube 40 is also formed from a resilient material. For example, the tube 40 may be formed from a thermoplastic or an elastomeric material. In further examples, the tube 40 may be formed from a TPU material. The tube 40 may be formed using an extrusion process. Alternatively, the lumens 41 a-41 d and the external wall 48 may be formed in separate processes and subsequently attached to one another, for example by using adhesives, or by welding.

In normal operation, the working fluid to be pumped flows through the primary tube chambers 42a-42d of the lumens 41 a-41 d, and the auxiliary tube chambers 44a-44e remain empty. Over time, the internal walls 46a-46d are likely to fail due to fatigue, causing rupture in the cheek regions of the internal walls 46a-46d. If rupture occurs in the internal walls 46a-46d of any of the four lumens 41a-41d, the fluid will enter one or more of their respective auxiliary tube chambers 44a-44e. The tube 40 comprises sensors 49 configured to detect when fluid has entered any one of the auxiliary tube chambers 44a- 44e. In this example, sensors 49 are located in each of the auxiliary tube chambers 44a- 44e. In other examples, sensors 49 may be located in only one or some of the auxiliary tube chambers 44a-44e. The sensor 49 may be any sensor suitable for detecting the presence of fluid within the auxiliary tube chambers 44a-44e. For example, the sensors 49 may be one or more of an optical sensor, an ultrasonic sensor, an infrared sensor, a radar sensor or a pressure sensor, as described with reference to the tube 20.

The sensors 49 may be connected to a control module of the pump, which may be configured to alert an operator of the pump to a status of operation of the pump or to automatically shut down the pump when fluid is detected within one of the auxiliary tube chambers 34a, 34b, 34c, as described with reference to the tube 10.

It will be appreciated that the invention may extend to tubes having any number of primary tube chambers and is not limited to the examples presented above.

It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

Claims

1. A peristaltic pump, comprising: a resilient tube having a primary tube chamber and an auxiliary tube chamber which are integrally formed with one another, wherein the primary tube chamber is configured to receive a working fluid and the auxiliary tube chamber is configured to receive the working fluid upon rupture of a wall of the primary tube chamber; and a sensor configured to detect working fluid in the auxiliary tube chamber.

2. A peristaltic pump according to claim 1 , wherein the auxiliary tube chamber extends only partially around the circumference of the primary tube chamber.

3. A peristaltic pump according to claim 1 or 2, wherein the tube comprises two auxiliary tube chambers disposed at diametrically opposed positions from the primary tube chamber.

4. A peristaltic pump according to claim 1 , wherein the auxiliary tube chamber surrounds the primary tube chamber.

5. A peristaltic pump according to any preceding claim, wherein the resilient tube comprises a plurality of primary tube chambers arranged in parallel, wherein adjacent primary tube chambers are connected such that an auxiliary tube chamber is formed between adjacent primary tube chambers.

6. A peristaltic pump according to claim 5, wherein the adjacent primary tube chambers are connected by resilient members extending between the respective walls of adjacent primary tube chambers to define the auxiliary tube chamber.

7. A peristaltic pump according to any preceding claim, wherein the sensor is located within the auxiliary tube chamber.

8. A peristaltic pump according to any preceding claim, wherein the sensor is configured to detect a change in the pressure of the working fluid in the resilient tube.

9. A peristaltic pump according to any of claims 1-7, wherein the sensor comprises one or more of an optical sensor, an ultrasonic sensor, an infrared sensor, a conductivity sensor and a radar sensor.

10. A resilient tube for a peristaltic pump, comprising: a primary tube chamber and an auxiliary tube chamber which are integrally formed with one another, wherein the primary tube chamber is configured to receive a working fluid and the auxiliary tube chamber is configured to receive the working fluid upon rupture of a wall of the primary tube chamber.

11. A resilient tube according to claim 10, wherein the auxiliary tube chamber extends only partially around the circumference of the primary tube chamber.

12. A resilient tube according to claims 10 or 11 , wherein the tube comprises two auxiliary tube chambers disposed at diametrically opposed positions from the primary tube chamber.

13. A resilient tube according to claim 10, wherein the auxiliary tube chamber surrounds the primary tube chamber.

14. A resilient tube according to any of claims 10 to 13, comprising a plurality of primary tube chambers arranged in parallel, wherein adjacent primary tube chambers are connected such that an auxiliary tube chamber is formed between adjacent primary tube chambers.

15. A resilient tube according to claim 14, wherein the adjacent primary tube chambers are connected by resilient members extending between the respective walls of adjacent primary tube chambers to define the auxiliary tube chamber.