GB2212862A

GB2212862A - A pump

Info

Publication number: GB2212862A
Application number: GB8827191A
Authority: GB
Inventors: Patrick Joseph Mckeown; Norman Wynne Slack
Original assignee: GALETOWN ENTERPRISES Ltd
Current assignee: GALETOWN ENTERPRISES Ltd
Priority date: 1987-11-25
Filing date: 1988-11-22
Publication date: 1989-08-02
Also published as: IE873196L; GB8827191D0

Abstract

A relatively low cost pump 1 comprises a tubular member 3 formed by deforming a pipe of circular cross section at 23. The tubular member 3 is clamped between end caps (6) and 7 to form a pumping chamber 5. An impeller 14 fast on a shaft is rotatable within the pumping chamber 5 for pumping slurry or other liquids through the chamber 5 from an inlet 17 to an outlet 18. The impeller 14 comprises a core with a plurality of radially extending flexible vanes 37 which are deformed by the deformed portion 23 to pressurize the slurry as it is being delivered through the outlet 18. A method of deforming the tubular member by the use of a deforming tool in a press is decribed (Figs 7 to 9). <IMAGE>

Description

Title: A PUMP The present invention relates to a pump and a method for forming a pump, and in particular though not limited to a pump for pumping slurry with or without particulate matter entrained therein.

Pumps for pumping slurry, and in particular pumps for pumping slurry with entrained particulate matter, such as, for example, fibrous material and the like, in general, comprise a housing which forms a pumping chamber and an impeller with a plurality of radially extending vanes is rotatably mounted in the pumping chamber. An inlet and outlet are provided to the pumping chamber.

In general, the pumping chamber is of circular cross section and the impeller is offset mounted relative to the central axis of the chamber. Alternatively, the impeller may be of non-circular cross section, and is co-axially mounted in the pumping chamber to build up a pressure to one side of the impeller for delivering the slurry through the outlet. Such known pumps suffer from a number of disadvantages. In general, they tend to be relatively expensive to manufacture.

In the case of pumps in which the pumping chamber is of circular cross section, it is important that the impeller should be mounted with high precision within the chamber to ensure adequate pressure being imparted to the slurry being pumped. In the case of pumps in which the impeller is of non-circular cross section, the cost of producing the impeller of the appropriate cross section is relatively expensive. In virtually all cases, it requires that the impeller should be moulded, and in general, because of the relatively complex shape of the impeller, the mould costs and subsequent cost of producing the impeller are relatively expensive.

There is therefore a need for a pump suitable for pumping liquids and in particular slurry, and preferably slurry with entrained particulate matter which overcomes the problems of known pumps. There is also a need for a method of producing such a pump.

The present invention is directed towards providing such a pump and a method.

According to the invention, there is provided a pump comprising a body member having a bore extending therethrough between a pair of opposite end faces, the bore defining a pumping chamber, end caps engaging respective end faces of the body member closing the pumping chamber, an inlet and an outlet being provided to the pumping chamber and an impeller rotatable in the pumping chamber, wherein the body member is formed from a tubular member having a main longitudinal central axis and a cylindrical side wall, portion of the side wall extending from one end face to the other being deformed inwardly.

In one embodiment of the invention, the tubular member prior to being deformed is of circular cross section, the central axis of curvature of the circular portion forming the main longitudinal central axis.

In another embodiment of the invention, the deformed portion of the side wall extends over an angular distance relative to the main longitudinal central axis in the range of 300 to 1800, and preferably, 60 to 1200, and advantageously 104".

In another embodiment of the invention, the deformed portion of the side wall is substantially flattened.

Preferably, a ridge extends inwardly into the pumping chamber from the deformed portion of the side wall, the ridge extending longitudinally of the pumping chamber.

In one embodiment of the invention, the ratio of the radial distance (H) between the inner surface of the deformed portion of the side wall and the main longitudinal central axis at its nearest point to the radius of curvature (R) of the inner surface of the portion of the side wall of circular cross section is in the range of 0.70 to 0.88, preferably, 0.76 to 0.85 and advantageously 0.78.

In one embodiment of the invention, the rotational axis of the impeller co-incides with the main longitudinal central axis of the tubular member.

Preferably, the impeller comprises a core and a plurality of vanes radially extending from the core, each vane having a root portion engagable with the core and a tip portion which, in use, wipes along the inner surface of the tubular member, each vane being of a resilient material over at least portion of its radial length intermediate the root and tip portions.

Additionally, the invention provides a method for forming the pump according to the invention, the method comprising the steps of forming a body member from a tubular member having a cylindrical side wall by deforming portion of the side wall inwardly over the length of the tubular member, and assembling a pair of end caps to respective end faces of the tubular member.

Preferably, the tubular member prior to being deformed is of circular cross section.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevational view of a pump according to the invention, Fig. 2 is a sectional side elevational view of the pump of Fig. 1 on the line II - II of Fig. 3, Fig. 3 is a sectional end view of the pump on the line III - III of Fig. 2, Fig. 4 is a partly cut away perspective view of the pump of Fig. 1 with portion of the pump removed, Fig. 5 is a perspective view of portion of the pump of Fig. 1, Fig. 6 is a perspective view of another portion of the pump of Fig. 1, Fig. 7 is a perspective view of a forming tool for forming portion of the pump of Fig. 1, Fig. 8 is a perspective view of the forming tool of Fig. 7 in use, and Fig. 9 is a cross sectional view of the forming tool of Fig. 7 also in use.

Referring to the drawings, and initially to Figs. 1 to 6, there is illustrated a pump according to the invention indicated generally by the reference numeral 1. The pump 1 is particularly suited to heavy duty pumping, such as, for example, pumping slurries and slurries with entrained particles such as fibrous material and the likedispersed therethrough. Such forms of slurry would normally be encountered on farms and the like. The pump is suitable for connecting to any power source, however, in this case, it is particularly suitable for connecting to the power take off (PT0) (not shown) of a tractor (also not shown).

The pump 1 comprises a body member 2 which is formed by a tubular member 3 having a bore 4 extending therethrough to form a pumping chamber 5. The bore 4 is closed by end caps 6 and 7 which engage respective end faces 8 and 9 of the tubular member 3. Fastening members provided by bolts 10 extend through holes 11 in the end caps 6 and 7. Nuts 12 and washers 13 on the bolts 10 secure the tubular member 3 between the end caps 6 and 7. An impeller 14, described in more detail below, is fast on a shaft 15 and rotatable within the pumping chamber 5. The shaft 15 is rotatable in bearings 16 in the end cap 6, also described below An inlet 17 and outlet 18 are provided in the tubular member 3 to the pumping chamber 5. The inlet 17 and outlet 18 are threaded at 19 to receive suitable pipe couplings.

The tubular member 3 in this case is provided by a steel pipe 20 of circular cross section which is cut to length, see Fig. 8. A portion of the pipe 20 is deformed inwardly to form a deformed portion 23 which extends from one end face 8 to the other end face 9.

The method for deforming the pipe 20 to form the tubular member 3 is described below. As can be seen, the deformed portion 23 is deformed inwardly into the bore 4 of the tubular member 3 and a ridge 24 extending inwardly into the bore 4 is also formed in the deformed portion 23. The ridge 24 extends longitudinally along the tubular member 3 from the end face 8 to the end face 9 and is substantially centrally disposed on the deformed portion 23. The deformed portion 23 extends over an angular distance of the side wall of approximately 1040. Accordingly, when deformed, the tubular member 3 has a side wall portion 25 of circular cross section of inner radius R having a central axis 26 and the deformed side wall portion 23, see Fig. 3. In this case, the axis 26 forms the main longitudinal central axis 26 of the pumping chamber 5.Side edges 72 of the deformed portion 23, as can be seen in Fig. 3, co-incide with the axes 71 of the inlet 17 and outlet 18.

Grooves 27 are machined into the end faces 8 and 9 of the tubular member 3 to receive an O-ring 28 which acts as a sealing means for sealing the tubular member 3 to the end caps 6 and 7. Circular recesses 29 are formed in the end caps 6 and 7 to receive the tubular member 3 and liner discs 30 are: provided in the central recesses 29 to abut the rings 28 and thereby form a seal.

Openings 31 are provided in the discs 30 so that the disc 30 adjacent the end cap 6 can accommodate the shaft 15. A keyway 76 on the end of the shaft 15 is provided for coupling the shaft to a drive shaft.

The end caps 6 and 7 may be formed by machining or may be cast as desired. A boss 32 integrally formed with the end cap 6 extends outwardly thereof, and a bore 33 extending through the boss 32 and end cap 6 carry the bearings 16 for rotatably mounting the shaft 15. One of the bearings 16 abuts a shoulder 21 in the bore 33 and the other bearing 16 is retained in position by a circlip 22. Circlips 44 on the shaft 15 retain the bearings 16 against the shoulder 21 and circlip 22, and also locate the impeller longitudinally in the pumping chamber 5. A groove 73 in the bore 33 receives the circlip 22 and grooves 74 in the shaft 15 receive the circlip 44. A sealing ring 34 is provided in the bore 33 to seal the bearings 16 from the slurry in the pumping chamber 5.

The impeller 14 is co-axially mounted with the main longitudinal axis 26 and comprises a core 35 formed by a sleeve 36 and six vanes 37 extending radially from the sleeve 6. The sleeve 36 is keyed to the shaft 15 by a key 38 in keyways 39 and 40 on the shaft 15 and sleeve 36 respectively. Each vane 37 is of plastics material, in this case a plastics material sold under the trade name HYTREL sold by The Du Pont Corporation of the U.S. Each vane 37 has a tip portion 41 and a root portion 42 joined by a central portion 43. As can be seen, the root and tip portions 41 and 42 extend the length of the vanes 37 and are of greater cross sectional thickness than the central portion 43.

The thickness of the central portion 43 is such that the central portion 43 is resilient, thus permitting each vane to bend as it passes the deformed portion 23 and return to'its normal shape having passed the deformed portion 23, see Fig. 3. The root portion 42 of each vane 37 is slidable in a groove 45 in the sleeve 36 and is retained therein by sidewardly extending retaining members 47 extending the length of the root portion 42 which engage corresponding retaining grooves 48 in the grooves 45. Thus, a worn vane 37 can readily easily be replaced by sliding the worn vane 37 out of the groove 45 and replacing it with a fresh vane 37. Sealing rings 49 of P.T.F.E.

material are provided at each end of the sleeve 36 to form a seal between the sleeve 36 and the liner discs 30, see Figs. 2 and 4. Grooves 75 corresponding to the grooves 45 in the sleeve 36 are provided in the rings 49 to engage the root portions 42 of the vanes 37. The width of the vanes 37 is such that they lightly bear on the liner discs 30 to prevent leak back of the fluid being pumped.

In this case, the vanes 37 and sleeve 36 are extruded, the vanes 37 being extruded from the HYTREL material and the sleeve 36 being extruded from aluminium.

A sheet metal plate 52 having downwardly and inwardly directed side walls 53 and 54 respectively is clipped on to two of the fastening bolts 10 and extend across the deformed portion 23 of the side wall of the tubular member 3. The plate 52 is provided for displaying data on the pump a.

An eye bracket 56 is secured to the end cap 6 by the nut and washer 12 and 13 on one of the fastening bolts 10 to engage a stabilising chain 57 (portion of which is illustrated) for stabilising and preventing rotation of the pump 1 when being driven by a PTO shaft of a tractor.

To extend the life of the pump, the interior surface of the tubular member 3 and liner discs 30 are coated with hard chrome.

In this case, the length of the tubular member 3 is 90 mm and the radius of the inner surface of the side wall 25 of the circular cross section is 82 mm.

The deformed portion 23 is so deformed that the radial distance H between the inner surface 70 of the ridge 24 and the central axis 26 is 64 mm. Thus, in this case, the ratio between the distance H and the radius R is 0.78. The wall thickness of the tubular member 3 is 10 mn.

Referring now to Figs. 7 to 9, there is illustrated a forming tool for forming the tubular member 3 from a pipe 20 of circular cross section. The forming tool comprises a first part and a second part, namely an upper part 61 and a lower part 62 both formed of tool steel. The lower part 62 comprises a recess 63 which defines the outer surface of the circular side wall 25 of the tubular member 3. In this case, the radius of the surface of the recess 63 is 92 mm. The upper part 61 also comprises a recess 64, however, as can be seen, portion 65 of the recess 64 defines the outer surface of the deformed portion 23 of the tubular member 3. The remaining portion 66 of the recess 64 defines the remaining circular part of the side wall 25 of the tubular member 3. End plates 67 are provided at each end of the lower part 62 to retain the pipe 20 in the forming tool 60 during forming.

Both upper and lower parts 61 and 62 are suitable for mounting in a hydraulic press (not shown), the lower part 62 is mounted on the bed of the press while the upper part 61 is mounted to the ram of the press.

To form a tubular member 3, a pipe 20 is cut to the desired length and the grooves 27 are formed in the end faces 8 and 9. The pipe 20 is placed in the recess 63 of the lower part 62. The upper part 61 is then brought into engagement with the lower part by the ram (not shown) as illustrated in Fig. 9, thereby forming the deformed portion 23 in the pipe 20 to form the tubular member 3. In this case, the internal radius of the pipe 20 prior to being-deformed is 80 mm. The internal radius R of the circular portion 25 of the tubular member 3 after the portion 23 is deformed, as already discussed, is 82 mm. This increase in radius is allowed to accommodate deformation of the portion 23. Openings for the inlet 17 and outlet 18 may be formed in the tubular member before or after the portion 23 has been deformed.

In use, the pump 1 is coupled to any suitable power source, for example, an electric motor or PTO shaft of a tractor. Where the pump 1 is to be driven by the PTO shaft of the tractor, a suitable coupling is used to connect the shaft 15 to the PTO shaft of the tractor. The stabilising chain 57 from the bracket 56 is anchored to a stable part of the tractor housing to prevent the pump 1 rotating with the shaft 15. Inlet and outlet pipes (not shown) are coupled to the inlet and outlet 17 and 18 respectively. The pump is then ready for use and the PTO shaft rotates the impeller 14 while the stablising chain 57 prevents the body member 2 of the pump 1 rotating and accordingly the impeller 14 is rotated in the pumping chamber 5.As the impeller 14 rotates in the direction of the arrow A in the pumping chamber 5, the liquid being pumped, in general slurry, is drawn in through the inlet 17 and moved in the direction of the arrow B through the chamber 5 under the action of the vanes 37 and is delivered through the outlet 18. The pumping action is achieved by virtue of the fact that as the slurry is being delivered through the pumping chamber 5 towards the outlet 18 each compartment 70 formed between an adjacent pair of vanes 37 and the adjacent portions of the core 35 and side wall 23 and 25 of the tubular member 3 is reduced in volume as the vanes 37 engage the deformed portion 23. As they move further along the deformed portion, the vanes 37 are further deformed, thus further reducing the volume of each compartment 70.Thus, as the volume of each compartment 70 is reduced as the vanes pass by the outlet 18 in engagement with the deformed portion 23, the slurry in the compartment 70 is delivered through the outlet 18. Deformation of the vanes 37 which reduce the size of the compartments 70 adjacent the outlet actually increases the compartments 70 adjacent the inlet 17. Accordingly, as the vanes 37 further rotate beyond the inlet 17, the size of the compartments 70 reduces and thus the slurry in these compartments 70 is pressurized. The further deformation of the vanes 37 adjacent the outlet 18 causes further pressurization, thus the slurry is delivered through the outlet 18 under pressure.

It has been found that a pump of the dimensions described delivers slurry through the outlet at a pressure of 50 pounds per square inch. Where an outlet pressure of 100 pounds per square inch is desired, this can be achieved by providing two pumps similar to that described in series so the outlet of one pump would feed the inlet of the next pump. It has been found that this arrangement can deliver slurry or other liquids through the outlet of the second pump with a pressure of 100 pounds per square inch.

The pump 1 according to the invention has many advantages. In particular, by virtue of the fact that the body member of the pump is formed by a tubular member which is formed by deforming a pipe of circular cross section, a relatively inexpensive pump can be produced. The cost of forming the body member is relatively low, and furthermore, the body member can be formed relatively easily. A further and particularly important advantage of the invention is that by virtue of the fact that the body member is formed by a tubular member formed from a pipe, pumps of varying capacity can be provided at virtually no additional cost. To increase or decrease the capacity of a pump, all that is required is to vary the length of the tubular member 3, and the length of the impeller 14 which requires lengthening or shortening the sleeve 36 and vanes 37.This, as will be appreciated by those skilled in the art, is a relatively simple and straightforward matter. Since the pipe from which the tubular member 3 is formed may be bought in relatively long lengths, and similarly since the sleeves 36 and vanes 37 are formed by extrusions, by keeping a stock of pipes, sleeves and vanes in long lengths, pumps of any desired capacity can readily easily and quickly be provided. The end caps and other components of the pump are common for all pump sizes.

A further advantage of the invention is achieved b virtue of the fact that the vanes of the impeller are releasably mounted to the sleeve. Accordingly, should a stone or grit damage or rupture a vane, the vane can readily easily be replaced without replacing the entire impeller. Further advantages are achieved by virtue of the shape and construction of the impeller and by providing the impeller with vanes of HYTREL material in that vanes of adequate resilience are provided. Indeed it has been found that vanes of HYTREL and of the construction illustrated can withstand a considerable amount of flexing which they are subjected to during normal running of the pump.

Furthermore, by virtue of the construction of the pump and the fact that the tubular member is manufactured from a steel pipe, a relatively robust construction of pump is provided which is particularly suited for pumping liquids with solid matter entrained therein, such as, for example, slurries found on farmyards where fibrous materials and the like are entrained in the slurry.

While a pump of a particular size has been described, it will be appreciated that pumps of any other suitable size could be provided without departing from the scope of the invention. Tubular members of greater or lesser diameter could be used, and as already discussed, tubular members of any length may be used.

It will also be appreciated that while a particular method for forming the tubular member has been described, any other suitable method could be used.

It will further be appreciated that in all cases it may not be necessary to provide the ridge in the deformed portion, the deformed portion may be provided simply by a flattened portion being formed on the tube.

While the deformed portion of the tubular member has been described as covering an angular distance of approximately 1040, it is envisaged that particularly good results could be achieved once the angular distance of the deformed portion was in the range of 600 to 1200. Indeed, it is believed that adequate results could be achieved where the angular distance of the deformed portion is in the range of 30 to 1800.

It will also be appreciated that while the ratio of H to R in this case is 0.78 it is envisaged that good results would be achieved where the ratio of H to R is retained in the range 0.76 to 0.85. Indeed, it is believed that adequate results would be achieved once the ratio of H to R is held within the range 0.70 to 0.88.

It will also be appreciated that end caps and impellers of other shape and construction could be used without departing from the scope of the invention.

It will of course be appreciated that the inlet and outlet may be provided in any suitable location on the tubular member, or indeed in certain cases on the end caps or end cap.

Needless to say, it will be appreciated by those skilled in the art that end caps of other shape and construction could be provided. Indeed, in certain cases, it is envisaged that the shaft may be rotatably mounted in each end cap, and in certain cases, it is envisaged that the shaft may extend out through each end cap so that the pump could be coupled at either end to a drive motor. It will, of course, be appreciated that any other suitable fastening means for retaining the tubular member clamped between the end caps could be used.

It will also be appreciated that an impeller of other shape and construction could be used without departing from the scope of the invention. Indeed, in certain cases, it is envisaged that the impeller may be formed as an integral unit rather than having a core or a sleeve and a plurality of releasably mounted radial vanes. In which case, it is envisaged that the core and vanes would be of the same material, and either formed integrally by injection moulding or by extrusion.

It will of course be appreciated, that while a particular construction of forming tool has been described for forming the tubular member, any other suitable shape and construction of forming tool could be provided. Needless to say, it will be appreciated that a tubular member of other shape and construction could be used as already discussed. The important aspect of the invention is that the body member should be formed from a tubular member by inwardly deforming the tubular member.

Needless to say, while in certain cases it is preferable, it is not necessary that the inner surface of the body member and/or liner discs be coated with hard chrome material or indeed any other hardened wear resistant material.

Claims

1. A pump comprising a body member having a bore extending therethrough between a pair of opposite end faces, the bore defining a pumping chamber, end caps engaging respective end faces of the body member closing the pumping chamber, an inlet and an outlet being provided to the pumping chamber and an impeller rotatable in the pumping chamber, wherein the body member is formed from a tubular member having a main longitudinal central axis and a cylindrical side wall, portion of the side wall extending from one end face to the other being deformed inwardly.

2. A pump as claimed in Claim 1 in which the tubular member prior to being deformed is of circular cross section, the central axis of curvature of the circular portion forming the main longitudinal central axis.

3. A pump as claimed in Claim 1 or 2 in which the deformed portion of the side wall extends over an angular distance relative to the main longitudinal central axis in the range of 30 to 1800.

4. A pump as claimed in Claim 3 in which the deformed portion of the side wall extends over an angular distance relative to the main longitudinal central axis of 60 to 1200.

5. A pump as claimed in Claim 4 in which the deformed portion of the side wall extends over an angular distance relative to the main longitudinal central axis of 104".

6. A pump as claimed in any preceding claim in which the deformed portion of the side wall is substantially flattened.

7. A pump as claimed in any preceding claim in which a ridge extends inwardly into the pumping chamber from the deformed portion of the side wall, the ridge extending longitudinally of the pumping chamber.

8. A pump as claimed in Claim 7 in which the ridge is substantially centrally disposed of the deformed portion of the side wall.

9. A pump as claimed in any preceding claim in which the ratio of the radial distance (H) between the inner surface of the deformed portion of the side wall and the main longitudinal central axis at its nearest point to the radius of curvature (R) of the inner surface of the portion of the side wall of circular cross section is in the range of 0.70 to 0.88

10. A pump as claimed in Claim 9 in which the ratio of the radial distance (H) between the inner surface of the deformed portion of the side wall and the main longitudinal central axis at its nearest point to the radius of curvature (R) of the inner surface of the portion of the side wall of circular cross section is in the range of 0.76 to 0.85.

11. A pump as claimed in Claim 10 in which the ratio of the radial distance(H) between the inner surface of the deformed portion of the side wall and the main longitudinal central axis at its nearest point, to the radius of curvature (R) of the inner surface of the portion of the side wall of circular cross section is 0.78.

12. A pump as claimed in any preceding claim in which the rotational axis of the impeller co-incides with the main longitudinal central axis of the tubular member.

13. A pump as claimed in any preceding claim in which the impeller comprises a core and a plurality of vanes radially extending from the core, each vane having a root portion engagable with the core and a tip portion which, in use, wipes along the inner surface of the tubular member, each vane being of a resilient material over at least portion of its radial length intermediate the root and tip portions.

14. A pump as claimed in Claim 13 in which the vanes extend substantially the longitudinal length of the pumping chamber.

15. A pump as claimed in Claim 13 or 14 in which the tip and root portions extend the length of the vane and are of thicker cross section than the portion of the vane extending between the root and tip portions, the portion of the vane intermediate the tip and root portions being of a resilient material.

16. A pump as claimed in any of Claims 13 to 15 in which each vane is releasably mounted in the core.

17. A pump as claimed in Claim 16 in which the root portion of each vane slidably engages a corresponding longitudinal groove in the core.

18. A pump as claimed in any of Claims 13 to 17 in which the core and each vane are formed by extrusions.

19. A pump as claimed in any of Claims 13 to 18 in which each vane is of a plastics material.

20. A pump as claimed in Claim 19 in which each vane is of a plastics material sold under the Trade Name HYTREL.

21. A pump as claimed in any of Claims 13 to 20 in which the core is formed by a sleeve mounted fast on a shaft.

22. A pump as claimed in Claim 21 in which the shaft extends from the pumping chamber through one of the end caps and is rotatably mounted in the end cap.

23. A pump as claimed in Claim 22 in which a boss extends outwardly from the end cap and carries a pair of spaced apart bearings to rotatably support the shaft.

24. A pump as claimed in any preceding claim in which sealing means are provided between the tubular member and each end cap.

25. A pump as claimed in Claim 24 in which each sealing means is provided by an O-ring mounted in a groove extending round each end face of the tubular member.

26. A pump as claimed in any preceding claim in which the end caps and tubular member are secured together by a plurality of fastening members extending between the end caps to retain the tubular member secured between the end caps.

27. A pump as claimed in Claim 26 in which the fastening members extend between the end caps outside the tubular member.

28. A pump as claimed in any preceding claim in which the inner surface of the tubular member is provided with a coating of hard metal.

29. A pump as claimed in Claim 28 in which the metal coating is a chrome coating.

30. A pump as claimed in any preceding claim in which the inlet and outlet are provided on the tubular member.

31. A pump as claimed in Claim 30 in which the centre line of the inlet and outlet substantially intersects respective boundary edges of the deformed portion of the side wall.

32. A pump substantially as described herein with reference to and as illustrated in the accompanying drawings.

33. A method for forming a pump of any of Claims 1 to 32 the method comprising the steps of forming a body member from a tubular member having a cylindrical side wall by deforming portion of the side wall inwardly over the length of the tubular member, and assembling a pair of end caps to respective end faces of the tubular member.

34. A method as claimed in Claim 33 in which the tubular member prior to being deformed is of circular cross section.

35. A method as claimed in Claim 33 or 34 in which the method includes substantially flattening the portion of the side wall to be deformed.

36. A method as claimed in any of Claims 33 to 35 in which the angular distance of the deformed portion is in the range of 30 to 1800.

37. A method as claimed in Claim 36 in which the angular distance of the deformed portion is in the range of 60 to 1200.

38. A method as claimed in Claim 37 in which the angular distance of the deformed portion is 104D.

39. A method as claimed in any of Claims 33 to 38 in which the side wall is deformed inwardly so that the ratio of the radial distance (H) between the inner surface of the deformed portion of the side wall and the main longitudinal central axis at its nearest point, to the radius (R) of the inner surface of the portion of the side wall of circular cross section is in the range of 0.70 to 0.88.

40. A method as claimed in Claim 39 ip which the side wall is deformed inwardly so that the ratio of the radial distance (H) between the inner surface of the deformed portion of the side wall and the main longitudinal central axis at its nearest point to the radius (R) of the inner surface of the portion of the side wall of circular cross section is 0.78.

41. A method as claimed in any of Claims 33 to 42 in which the method includes the step of forming an inwardly directed ridge in the deformed portion of the tubular member, the ridge extending longitudinally of the tubular member.

42. A method as claimed in Claim 41 in which the ridge is centrally disposed in the deformed portion.

43. A method as claimed in any of Claims 33 to 42 in which the tubular member is placed in a forming tool having a first part and a second part, the first part having a recess defining the outer cross section of the tubular member and the second part having a recess defining the outer cross section of the deformed portion of the tubular member.

44. A method as claimed in Claim 44 in which the recesses in the first and second parts of the forming tool when the mould is brought together define the outer surface of the tubular member when deformed.

45. A method substantially as described herein with reference to and as illustrated in the accompanying drawings.