WO2009006648A1

WO2009006648A1 - Peristaltic pump

Info

Publication number: WO2009006648A1
Application number: PCT/ZA2008/000057
Authority: WO
Inventors: Raymond William Hinks
Original assignee: Raymond William Hinks
Priority date: 2007-07-04
Filing date: 2008-07-04
Publication date: 2009-01-08
Also published as: ZA201000796B; WO2009006649A1

Abstract

A peristaltic pump which has a wheel structure, inside a casing, which is supported by bearings on opposed sides of the structure, and a hydraulic mechanism for adjusting the pressure exerted by the wheel structure on a hose inside the casing.

Description

PERISTALTIC PUMP

BACKGROUND OF THE INVENTION

[0001] This invention relates to a peristaltic pump.

[0002] One type of peristaltic pump makes use of a fixed wheel drive with protruding, diametrically opposed, fixed shoe members which, upon rotation of the wheel, compress a hose which is located inside a suitable casing. This type of pump, because of the heat generated by the sliding movement of the shoes over the hose, is limited at any particular required pumping pressure in respect of its speed of operation.

[0003] The substitution of the shoes by a rotating wheel member which compresses the hose closed while orbiting an internal diameter of the casing allows for a substantially higher operating speed and hence pumping rate. The wheel is mounted to a crank and, typically, an eccentrically bored sleeve, which supports the wheel, is rotatable about a pin of the crank to adjust a compressive force exerted by the wheel on the hose. As the speed of rotation and pumping pressure are increased substantial compressive loads are transferred, as a bending moment, to a region at which the crank pin is supported. This can lead to mechanical fatigue and eventual fracture, aspects which can only be overcome by the use of larger crankshafts and support bearings. In practical terms these technical factors restrict the maximum bore of the hose, which can be used, to about 80mm. This restriction should be viewed against the requirement that an interior of the casing must be accessible, when necessary, to change the hose and to clean leakage from internal areas. To achieve these objectives use is made of a removable cover which is engaged with the casing and this carries with it the limitation that it is possible to support the crankshaft from one end only.

[0004] Another difficulty arises when the hose is to be replaced. The eccentrically bored sleeve, which is used to adjust the degree of compression exerted by the wheel on the hose, does not allow for sufficient movement so that the wheel can be backed off completely from the hose. The replacement of a hose then becomes particularly tedious and time-consuming and requires multiple rotations of the wheel inside the casing. Safety regulations call for an electrical lock-out procedure each time the casing is internally accessed. A cover to the casing must thus be opened after each lock-out and closed each time before movement of the wheel takes place.

[0005] The invention aims to provide a peristaltic pump and a cartridge for use in a peristaltic pump which allow for higher pumping rates at high pressures and which substantially facilitate the replacement, when required, of the hose.

[0006] Thus an objective of the invention is to address current limitations on pump size so that higher pumping rates can be achieved.

SUMMARY OF INVENTION

[0007] The invention provides, in the first instance, a cartridge for a peristaltic pump which includes a structure which is rotatable about a first axis of rotation, a wheel which is mounted to the structure for rotation about a second axis of rotation which is parallel to the first axis of rotation and which is spaced from the first axis of rotation in a first direction, and a hydraulically actuable mechanism for adjusting the spacing between the first axis and the second axis. [0008] The cartridge may include at least one locking device for locking the spacing at a selected value,

[0009] The structure may include opposed first and second shaft ends which are axially aligned with the first axis of rotation, a support member, and first and second bearing assemblies which are respectively engaged with the first and second shaft ends, the first shaft end being engagable with a drive arrangement, and the second bearing assembly being mounted to the support member.

[0010] The structure may include a torque-transferring arrangement, connected to the first and second shaft ends, at least part of which is displaced from the first axis of rotation in a second direction which opposes the first direction.

[0011] The invention further extends to a peristaltic pump which includes a casing, a chamber inside the casing, a reaction surface which partly bounds the chamber, a wall on one side of the chamber, an inlet port to the chamber, an outlet port from the chamber, a resilient, flexible hose which extends, inside the chamber, from the inlet port, along the reaction surface, to the outlet poirt, a cartridge of the aforementioned kind located so that the structure is inside the chamber and the wheel is in contact with the hose, and a cover which is mounted to the casing and which, in a first position, opposes the wall.

[0012] The reaction surface may extend circumferentially around the chamber.

[0013] Preferably the cover is pivotally movable relatively to the casing between the first position and a second position at which the cartridge, inside the chamber, is exposed. [0014] The invention also provides a peristaltic pump which includes a casing, a chamber inside the casing, a reaction surface which partly bounds the chamber, a wall on one side of the chamber, an inlet port to the chamber, an outlet port from the chamber, a resilient, flexible hose which extends, inside the chamber, from the inlet port, along the reaction surface to the outlet port, a support member which opposes the wall and which is detachably engagable with the casing, first and second opposed bearing assemblies on the wall and support member respectively, structure, inside the chamber, which is between and supported by the bearing assemblies for rotation about a first axis of rotation, a drive arrangement for rotating the structure about the first axis of rotation, and a wheel which is mounted to the structure for rotation about a second axis of rotation which is parallel to the first axis of rotation and spaced from the first axis of rotation in a first direction, and which is engagable, and in compressing contact, with the hose.

[0015] The pump may include a mechanism which is actuable to adjust the spacing between the first axis and the second axis and a locking device for locking the spacing at a selected value.

[0016] The mechanism may be actuable to reduce the spacing to a value at which the wheel is removed from compressing contact with the hose, and to increase the spacing thereby to adjust the extent of compression of the hose by the wheel.

[0017] The structure may include a torque-transferring arrangement at least part of which is displaced from the first axis of rotation in a second direction which opposes the first direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention is further described by way of examples with reference to the accompanying drawings in which:

Figure 1 is a view of a peristaltic pump according to the invention with a cover removed;

Figure 2 is a view in cross-section of the pump in a direction which is transverse to the side view of Figure 1 ;

Figures 3 and 4 are similar to Figures 1 and 2 respectively but illustrating further constructional details; Figures 5 and 6 are side views of the pump, with a cover in an open position, illustrating the replacement of a hose in the pump;

Figures 7 and 8 are similar to Figures 3 and 4 respectively, but simplified and illustrating the use of a hydraulically actuated adjusting mechanism;

Figures 9 and 10 are similar to Figures 7 and 8 and also illustrate the use of the hydraulically actuated adjusting mechanism;

Figure 11 is a plan view of the pump shown in Figure 9;

Figure 12 is a cross-sectional simplified rendition of Figure 4 illustrating a rigid driving or torque-transferring mechanism embodied in a structure of the pump; and

Figure 13 depicts the removal of a cartridge from the pump.

DESCRIPTION OF PREFERRED EMBODIMENT

[0019] Figures 1 and 2 of the accompanying drawings are side and cross-sectional views respectively of a peristaltic pump 10 according to the invention. Figures 3 and 4 are views which are similar to Figures 1 and 2 but illustrating further constructional details of the peristaltic pump. [0020] The pump includes a casing 12 which has a wall 14 and a circumferentially extending section 16 secured to the wall. A reaction surface 18 is formed by an inner surface of the section 16. The wall and section are mounted to a pedestal 20. The various components are fixed together by the means of suitable bolts and fasteners. Alternatively the wall and section 16 can be integrally formed e.g. by casting.

[0021] A pumping chamber 22 is defined inside the circumferential section 16. A structure 24 is positioned inside the chamber. The structure carries a wheel 26.

[0022] The structure 24 has a first shaft end 30 and an axially opposed second shaft end 32. The shaft ends are axially aligned on a first axis of rotation 34. A first bearing assembly 36 is engaged with the first shaft end. The bearing assembly is of a conical nature and is located in a complementary recess 38 formed in a boss 40 on the wall 14. A cylindrical recess 42 is formed in an axial direction in the first shaft end 30. A keyway 44 is machined in a surface of the cylindrical recess. An electric drive arrangement 46, of a kind known in the art, has a drive shaft 48 which extends into the cylindrical recess and is locked to the first shaft end by means of a key positioned in the keyway.

[0023] A second bearing assembly 54 rotatably supports the second shaft end 32. A bearing cap 56, is engagable, with a close-clearance fit, with an outer surface of the second bearing assembly. The bearing assembly is attached by means of bolts to a support member 60 which, in turn, is attached by means of suitable bolts to a flange 62 on the circumferential section 16. The bearing assembly is also attached to a cover 64 which is pivotally mounted by means of hinges 66 to a structure on the circumferential section 16.

[0024] The wheel 26 has an outer ring 70 which opposes the reaction surface 18 and a hub 72 which is mounted on a bearing arrangement 74 fixed to a shaft 76. The shaft has opposed projecting ends 78 and 80 respectively which project from the bearing arrangement and which extend into slots 82 and 84 respectively in opposed plates 86 and 88 which form part of the structure 24.

[0025] The shaft 76 is circular in cross-section over its central portion and each of the projecting ends 78 and 80 is formed with opposed flat surfaces 90 and 92 respectively - see Figure 3 for example. Each slot (82, 84) extends in an axial direction in the corresponding plate (86, 88) and is dimensioned so that the slot closely receives the associated projecting end of the shaft with the flat surfaces abutting opposing surfaces of the slot. The shaft is aligned on a second axis of rotation 96.

[0026] Hydraulically actuable cylinder and piston assemblies 100 and 102 are positioned on opposing sides of the wheel 26. The cylinders are externally threaded. The cylinders pass through holes 104 and 106 which extend from ends of the plates 86 and 88 and are threadedly engaged with corresponding threaded holes in the projecting shaft ends 78 and 80 respectively. An end of each piston reacts against the structure in the corresponding slot e.g. a base of the slot.

[0027] A threaded passage 114 extends from a side of each respective plate 86 and 88 transversely to the corresponding slot. A mechanical locking device 116 is mounted to each plate. Each device includes a bolt 118 and a lock nut 120 which is engaged with the bolt which, in turn, is threadedly engaged with the passage. The bolt has a leading conical end 122 and this is positioned inside a V-shaped slot 124 in a curved side of the shaft end.

[0028] The slots 82 and 84 extend in a radial sense in a first direction 130 away from the first axis of rotation 34. The shaft 76, which has opposing ends in the slots, is also displaced in the first direction. Thus the second axis of rotation 96, which is parallel to the first axis of rotation 34, is displaced in the first direction from the first axis of rotation.

[0029] The plates 86 and 88, on the other hand, extend, in a radial sense, in a direction 132 which opposes the direction 130. A bridging plate 134 is connected between extremities of the plates 86 and 88.

[0030] The support member 60 has a circumferential peripheral portion 6OA, and inwardly extending arms 6OB and 6OC respectively which terminate in a hub 6OD which provides support for the second bearing assembly 54. The portion 6OA may, alternatively, extend circumferentially only through an arc of about 180° in a lower half of the casing. Apertures 6OE and 6OF on opposing sides of the arms provide access to interior recesses of the chamber 22.

[0031] The wheel 26 has a relatively thin web 26A between the outer ring 70 and its hub 72 and a plurality of apertures 26B are formed through the web to allow for internal reaches in the chamber to be accessed without removing the wheel.

[0032] The casing 12 has an inlet port 140 on one side of a lower end and an outlet port 142 on an opposing side of the lower end. A reinforced, flexible and resilient hose 144 of a kind known in the art extends from the inlet port along the reaction surface 18 with a single helical turn to the outlet port 142. Opposing ends of the hose are fixed to the ports using appropriate fasteners and seals 146 which are not further described herein.

[0033] Referring particularly to Figures 7 to 11 the assemblies 100 and 102 are connected in a common hydraulic system by means of a hydraulic line 150 which extends along the plates 86 and 88 and the intermediate bridging plate 134. The line 150 terminates in a quick release coupling 152 which is adjacent the support member 60. A hydraulic hand pump, not shown, is readily connected to the connector 152. Upon actuation of the hand pump the assemblies 100 and 102 are equally pressurized and are therefore extensible in unison. A pressure gauge 154, which is conveniently mounted to the line 150, or to the hand pump, is used to measure the pressure in the hydraulic system.

[0034] The hydraulically actuable piston and cylinder assemblies 100 and 102 have two significant benefits: firstly, they enable the degree of compression which is exerted by the wheel 26 on the hose 144 to be accurately controlled, during operation and, secondly, their use considerably simplifies the replacement of the hose when necessary.

[0035] Assume that the locking devices 116 have been slackened. To do this the lock nuts 120 are loosened and the locking bolts 118 are turned so that their tapered leading ends are completely disengaged from protruding into the slots. To assure this there is only a short threaded portion so that when the bolts 118 turn freely upon thread disengagement, the tapered ends are free of the slots. If the pump is then operated the assemblies 100 and 102 are extended. The piston ends bear against a bottom recess in the form of a blind hole in each slot and the shaft ends are moved in unison in the direction 130. The wheel 26 thus bears with increasing force on the hose. A first pressure rise is indicated on the gauge 154 as the wheel 26 is urged into compressive contact with the hose. Ultimately the hose is flattened against the reaction surface of the cylindrical section 16. If the pump is used to increase the hydraulic pressure further then the hose material is compressed. This is accompanied by a sharp rise in the gauge reading. The magnitude of the pressure is directly related to the degree of compression applied in decreasing the clearance gap between the reaction surface and an opposing outer surface of the outer ring 70. At a known clearance 156 (see Figure 8) that enables the hose to operate correctly with regard to required parameters of pressure and flow, determined by the required pumping duty, the locking devices 116 are actuated. In each instance the bolt 118 is rotated with a suitable tool so that the conical leading end of the bolt is driven into tight frictional engagement with the corresponding slot in the associated shaft end.

The shaft end in turn is urged into tight frictional engagement with a side wall of the slot. Thereafter the lock nuts 120 are used to lock the bolts 118 in position. Once the locking devices have thus been mechanically actuated the hydraulic pressure in the cylinders can be reduced to less stressful levels, if required, for the forces which are exerted from the compressed hose are carried by the locking devices and by the jamming effect which the locking devices exert via the sides of the' shaft against the corresponding sides of the slots.

[0036] An important aspect is that the locking devices ensure accurate location and positional fixture of the shaft and, therefore, the wheel assembly. The shaft is restrained against axial movement and contact between the plates 84, 86 on the one hand, and the corresponding bearing-retaining plates on the other hand, is avoided.

[0037] The locking devices 116 are separately actuated. The apertures 26B in the wheel enable the locking device 116 adjacent the wall 14 to be accessed with relative ease. During this process however the locking device which is adjacent the support member 60 is kept in a locked position. With this precaution if a failure in the hydraulic system should occur then the wheel 26 cannot be urged downwardly by the hose for it is retained in position by the locking device which is adjacent the support member.

[0038] The support member 60 allows for the stiff and proper support and location of the bearing assembly 54 when conducting a hose change or other maintenance procedure. A vital aspect of the cover 64, however, is to provide additional bearing support and radial stiffness when the pump is operating in addition to that which is provided by the support member alone. It is essential therefore that the cover must be automatically aligned with the housing of the bearing assembly 54 before being bolted to the casing 12 and to the support member 60. This cannot be accomplished by simply swinging the cover over the bearing housing for the requirement of a close- fitting, centrally located, hole formation, engageable with the bearing housing,

I prohibits angular movement of the cover relatively to the housing.

[0039] The bearing cap 56 is removed by releasing an outer ring of bolts. A nut formation 162 is positioned on an outer surface of the bearing cap to loosen any stiffening which may have taken place. Onces the bearing cap has been removed and the bolts which secure the cover to the casing have been released then the cover is supported only by the hinges 66 orh one side and by a tapered shank element 164 on an opposing side. This eleme nt has a central parallel shank which terminates in a threaded length at one end arid, at an opposing end, has a wider diameter surface machined off-centre to it. This larger diameter surface is parallel for a distance which is equal to the thickness of the cover 64 and terminates in a shallow taper towards its end. The cover has a slotted formation 166 with parallel sides which are machined so that the slotted formation can closely engage with the shank when the cover is in a closed position. This cam-type configuration enables the central position of the cover 64 to be accurately aligned with the bearing assembly 54 and allows for any misalignment to be trimmed.

[0040] The cover 64 can be of significant size and weight and it is therefore desirable for the cover to be retained in hinged and supporting engagement with the casing. This considerably reduces the work required to change the hose. On the other hand, as noted, the cover must be capable of adequately supporting the second bearing assembly which is engaged with the shaft end 32.

[0041] The hose 144 has a limited lifetime. Although the hose is made to exacting technical standards it is subjected to considerable stress and strain by the rotating wheel, during operation of the pump, and wear on the hose is exacerbated by high flow rate and pressure requirements and replacement of the hose is necessary from time to time.

[0042] In order to access the hose, the cover 64, which is supported on the hinges 66, is swung aside to reveal the inner, adjacent, support member 60 - see Figure 6. This support member remains in situ while the hose is changed. Sufficient access to the hose is made possible via the apertures 6OE and 6OF to enable the hose to be helically coiled inside the chamber and for ends of the hose to be engaged with the inlet port 140 and outlet port 142.

[0043] The drive arrangement 46 is initially actuated to bring the wheel 26 to a top central location as is shown in Figures 7 and 8. A safety bolt, not shown, is then engaged in a shallow slotted formation in the support member 60 at a location marked 168 in Figure 7 and is screwed into a blind tapped hole in an outer side of the plate 88. This assures that the rotor assembly cannot rotate under its own mass during the hose replacement procedure. Preferably this bolt is one of the bolts which are used to retain the bearing cap structure in position and which must be removed to facilitate opening of the cover 64. Use of one of these bolts serves to stop closure of the cover without prior removal of the bolt. This prevents operation of the pump while the bolt is in place.

[0044] The locking devices 116 are released so that the ends of the shaft can move downwardly inside the corresponding slots. The hydraulic system is, if necessary, then depressurized in a controlled way to allow the rotor assembly to move slowly downwardly under its own weight until the ends of the shaft come into contact with the bases of the corresponding slots. As the rotor assembly moves downwardly the compressive force on the hose is reduced and finally is eliminated - see Figures 9 and 10. The hose can then be replaced without the need for further rotation of the rotor by the drive arrangement 46. Thus the electrical lock-out procedure, prescribed for safety reasons, is required once only.

[0045] A hose for a high capacity high pressure pump is extremely heavy. The existing installed hose is first released by uncoupling the fasteners 148. The hose is then manipulated, primarily working through the opening 6OF, so that ends of the hose are brought closer together and a central upper portion 170 of the hose is pulled out of the chamber, away from the reaction surface, whereupon the hose projects upwardly due to its inherent resilience. This is shown in Figure 5. The used hose is then removed. The interior of the casing can be accessed completely for cleaning of leakage residues.

[0046] A fresh hose is then inserted into the chamber. The hose is curved so that the arms 6OB and 6OC help to support the weight of the hose. A hose end is first engaged with and secured to the inlet port 140. Thereafter the opposing hose end is engaged with and secured to the outlet port 142. At this time the hose has positioned itself in the chamber above the wheel at the top central position, as shown in Figure 6. The hydraulic system can then be used to bring the wheel to an operative, pumping position.

[0047] A significant benefit of the peristaltic pump is its ability to exert high pumping pressures. This is due to the fact that the plates 86 and 88 and the bridging plate 134 constitute a rigid, torque-transferring arrangement which effectively constrains both sides of the structure 24, to which the wheel 26 is mounted, to be rotated in unison.

[0048] Although the bridging plate 134 transmits the primary driving torque from the plate 86 to the plate 88 the shaft 76, which is locked to the slots 82 and 84, acts in unison with the plate 134 and form a stiff driving mechanism, shown by a hatched area 180 in Figure 12, which extends from the drive arrangement 46 along two paths to the bearing assembly .54 which is rigidly supported by the support member 60 and the cover 64.

[0049] The structure 24 with the hydraulic system, the wheel 26 and the support member 60 make up a cartridge 182 which can be removed, as one element, from the chamber 22. The heavier items in the pump namely the casing, the cover 64 and the drive arrangement 46 are not items which are exposed to excessive wear during operation. These items may remain in situ while the cartridge can easily and safely be removed as a discrete single unit from the casing and taken to a workshop for repair when necessary. This capability also means that a spare cartridge can be held in reserve and installed immediately to replace a defective cartridge, and so return the pump to service with a minimum of down-time.

[0050] Figure 13 is a plan view, partly sectioned, of the pump. The bearing cap 56 has been removed and the cover 64 has been released and hinged aside to allow for full access to the cartridge.

[0051] A security bolt is engaged with the support member and the plate 88, at a location 188, to prevent unwanted rotation of the wheel. A trolley, not shown, has a support which is inserted into the casing through the aperture 6OE in the support member. [0052] With due precaution taken from the safety and technical points of view the hydraulic system is used in a controlled manner, after loosening of the locking devices 116, to enable the wheel 26 to settle downwardly onto the trolley support, under its own weight. At this stage the bearing assembly 36 is disengaged from the conical recess in the boss 40. If necessary a jacking bolt can be inserted into one of the holes in the casing hub to exert positive force against the bearing housing. Only a small axial movement of the housing member is required before the full weight of the cartridge is taken by the trolley. Thus, as is shown in Figure 13, the cartridge 182 can be removed in toto from the chamber. The cartridge, after repair, can be re- engaged with the casing or a fresh cartridge can be used in place of the removed cartridge.

[0053] The invention offers significant advantages over prior art devices of which the applicant is aware.

[0054] The support structure afforded by the cover and the support member means that effective support is provided on the first axis of rotation for the rotor assembly on both sides. Significant pressures can therefore be exerted by the wheel on the hose without giving rise to metal fatigue as is the case with a pump of the kind in which a crank-type arm which supports, in cantilever fashion, a compression wheel.

Secondly, the use of the hydraulically-actuated adjustment mechanism means that the pressure on the hose, exerted by the wheel, can be accurately controlled to achieve a desired operating pump pressure. Moreover the degree of adjustment is such that the wheel can be completely disengaged from the hose and this helps materially in hose replacement and internal cleaning of the chamber when necessary. In this respect it is to be borne in mind that the cover provides support for the cartridge on its outer side but is displaceable, when necessary, to allow relatively unhindered access to the chamber. With the cover hinged to an open position the outer end of the cartridge is supported by the support member. A further benefit lies in the rigid torque-transferring configuration shown in particular in Figure 12.

[0055] The cartridge is designed to be an integral self-contained unit. If repair to any component in the cartridge is required then the cartridge is easily removed from the casing and a fresh cartridge can be inserted into the pump rapidly and relatively easily to ensure that down-time is minimized.

Claims

1. A cartridge for a peristaltic pump which includes a structure which is rotatable about a first axis of rotation, a wheel which is mounted to the structure for rotation about a second axis of rotation which is parallel to the first axis of rotation and which is spaced from the first axis of rotation in a first direction, and a hydraulically actuable mechanism for adjusting the spacing between the first axis and the second axis.

2. A cartridge according to claim 1 which includes at least one locking device for locking the spacing at a selected value.

3. A cartridge according to claims 1 or 2 wherein the structure includes opposed first and second shaft ends which are axially aligned with the first axis of rotation, a support member, and first and second bearing assemblies which are respectively engaged with the first and second shaft ends, the first shaft end being engagable with a drive arrangement, and the second bearing assembly being mounted to the support member.

4. A cartridge according to any one of claims 1 to 3 wherein the structure includes a torque-transferring arrangement, connected to the first and second shaft ends, at least part of which is displaced from the first axis of rotation in a second direction which opposes the first direction.

5. A peristaltic pump which includes a casing, a chamber inside the casing, a reaction surface which partly bounds the chamber, a wall on one side of the chamber, an inlet port to the chamber, an outlet port from the chamber, a resilient, flexible hose which extends, inside the chamber, from the inlet port, along the reaction surface, to the outlet port, a cartridge according to any one of claims 1 to 4, located so that the structure is inside the chamber and the wheel is in contact with the hose, and a cover which is mounted to the casing and which, in a first position, opposes the wall.

6. A peristaltic pump according to claim 5 wherein the cover is pivotally movable relatively to the casing between the first position and a second position at which the cartridge, inside the chamber, is exposed.

7. A peristaltic pump which includes a casing, a chamber inside the casing, a reaction surface which partly bounds the chamber, a wall on one side of the chamber, an inlet port to the chamber, an outlet port from the chamber, a resilient, flexible hose which extends, inside the chamber, from the inlet port, along the reaction surface, to the outlet port, a support member which opposes the wall and which is detachably engagable with the casing, first and second, opposed bearing assemblies on the wall and support member respectively, structure, inside the chamber which is between and supported by the bearing assemblies, for rotation about a first axis of rotation, a drive arrangement for rotating the structure about the first axis of rotation, and a wheel which is mounted to the structure for rotation about a second axis of rotation which is parallel to the first axis of rotation and spaced from the first axis of rotation in a first direction, and which is engagable, and in compressing contact, with the hose.

8. A peristaltic pump according to claim 7 wherein the reaction surface extends circumferentially around the chamber.

9. A peristaltic pump according to claim 7 or 8 which includes a mechanism which is actuable to adjust the spacing between the first axis and the second axis, and a locking device for locking the spacing at a selected value.

10. A peristaltic pump according to claim 9 wherein the mechanism is actuable to reduce the spacing to a value at which the wheel is removed from compressing contact with the hose, and to increase the spacing thereby to adjust the extent of compression of the hose by the wheel.

11. A peristaltic pump according to any one of claims 7 to 10 which includes a cover which is mounted to the casing for pivotal movement between a first position at which the cover opposes the wall and a second position at which the cover opposes the structure inside the chamber.

12. A peristaltic pump according to claim 11 which includes a bearing support which is engagable with the cover and the second bearing assembly.

13. A peristaltic pump according to any one of claims 7 to 12 wherein the structure includes a torque-transferring arrangement at least part of which is displaced from the first axis of rotation in a second direction which opposes the first direction.