FLEXIBLE IMPELLER PUMP

Abstract

The present invention relates to improvements in the area of flexible impeller pumps. In particular, the present invention relates to flexible impellers with improved profiles (such as dual sealing lips), which are particularly well-suited to multiple cam pumps. A novel mounting hub configuration for mounting an impeller on a drive shaft is also provided. Pumps comprising such impellers and/or mounting hubs are provided, as are associated methods of installation and removal.

Claims

1. A mounting hub operable to connect a flexible impeller to a drive shaft.

2. The mounting hub of claim 1, wherein the hub is adapted to permit the impeller to be decoupled rotationally from the impeller drive shaft during installation, and then recoupled rotationally once the flexible impeller is in position.

3. The mounting hub of claim 2, wherein the hub comprises a drive shaft-engaging portion and an impeller body-engaging portion.

4. The mounting hub of claim 3, wherein the drive shaft-engaging portion comprises an aperture located axially in the hub which, in use, engages with the drive shaft and rotationally locks the hub relative to the drive shaft.

5. The mounting hub of claim 1, wherein the hub comprises a profiled portion on the outside of the hub which, in use, engages with the impeller body, and rotationally locks the hub relative to the impeller body.

6. The mounting hub of claim 1, wherein the hub is elongate and the length of the hub corresponds substantially to the full width of the impeller body.

7. The mounting hub of claim 1, wherein the hub comprises a tubular member which has a suitable cross-section such that the internal and external surfaces of the tubular member are adapted to engage with the drive shaft and the impeller, respectively, and rotationally lock them together.

8. The mounting hub of claim 1, comprising an impeller body engaging portion and drive shaft engaging portion each of which is independently selected from, corresponding splines, corresponding key and slot arrangements, and corresponding polygonal cross-sections.

9. The mounting hub of claim 1, comprising an elongate member defining a polygonal profiled inner lumen and a polygonal profiled outer surface.

10. The mounting hub of claim 9, wherein the inner lumen profile and the outer profile are generally triangular in cross section.

11. The mounting hub of claim 10, wherein the cross sections of inner and outer profiles of the hub are substantially truncated equilateral triangles.

12. The mounting hub of claim 1, wherein the hub is tapered along its length to facilitate insertion of the hub, and to provide centring of the impeller relative to the drive shaft as the hub is inserted.

13. The mounting hub of claim 1, wherein the hub is adapted to be secured to the impeller and/or the drive shaft to prevent relative axial movement between the hub and/or drive shaft using a suitable fixing means.

14. The mounting hub of claim 1 wherein the hub comprises an extraction means to assist in extraction of the hub.

15. A method of installing a flexible impeller into a flexible impeller pump housing, the method comprising: a) providing a flexible impeller; b) providing a flexible impeller pump housing having disposed therein a drive shaft for the flexible impeller; c) inserting the flexible impeller into the pump housing, preferably using a rotating action to facilitate insertion impeller; and d) providing a mounting hub operable to connect a flexible impeller to a drive shaft, and inserting the hub so that the hub rotationally locks the flexible impeller relative to the drive shaft.

16. The method of claim 15, wherein the drive shaft is rotationally static during the method steps.

17. The method of claim 15, comprising engaging a fitting tool with the impeller body, and using the fitting tool to rotate the impeller during insertion into the pump housing.

18. The method of claim 15, comprising securing the hub in position using a fixing means.

19. The method of claim 15, comprising installing a housing cover, and optionally any associated seals or gaskets or the like, to seal the pump housing.

20. A method of extracting an impeller mounted on a drive shaft via a mounting hub as set out above from a pump housing, the method comprising the steps of: a) engaging an extraction tool with an extraction means provided on the hub; b) operating the extraction tool to extract the hub from the drive shaft; and c) thereby extracting the impeller from the housing.

21. The method of claim 20, comprising disengaging a fixing means securing the hub to the drive shaft.

22. An impeller assembly, the impeller assembly comprising a flexible impeller and a mounting hub operable to connect the flexible impeller to a drive shaft.

23. The assembly of claim 22, wherein the impeller is a flexible impeller comprising a body and a plurality of vanes extending outwardly from the body, wherein each vane comprises a root and a tip and at least two sealing elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which:

[0087] FIG. 1 is a schematic representation of a flexible impeller pump according to an embodiment of the present invention;

[0088] FIG. 2 is an exploded perspective view of a flexible impeller pump according to an embodiment of the present invention;

[0089] FIG. 3 is a schematic representation of a flexible impeller according to the present invention;

[0090] FIG. 4 is a schematic detail view of three vanes of the impeller of FIG. 2;

[0091] FIG. 5 is an exploded perspective view of a flexible impeller, hub and extraction tool according to the present invention;

[0092] FIG. 6 is an end view of the flexible impeller, hub and extraction tool; and

[0093] FIG. 7 is a cross-section view through line B-B of FIG. 6.

DESCRIPTION OF AN EMBODIMENT

[0094] FIG. 1 shows a dual cam flexible impeller pump 10 according to an exemplary embodiment of the present invention. The flexible impeller pump 10 comprises a pump housing 12, having a first inlet 14, a first outlet 16, and second inlet 18, and a second outlet 20. The pump comprises a flexible impeller 22, which is rotatably mounted in the pump housing 12 on an impeller drive shaft 24.

[0095] The housing comprises cammed surfaces (also referred to as cams) 26 and 28, and cylindrical inner surfaces 30 and 32.

[0096] The impeller 22 comprises a body portion 34, 35 from witch a plurality of vanes 36 extend outwards, extending radially when adjacent to the cylindrical surface of the housing, and deflected into a bent configuration when in contact with the cammed surfaces. Each vane comprises a tip 38, a root 40 and a stem 42 extending between the root and this tip. An inter-vane volume 44 is defined by the trough between a vane and the adjacent vane, in which the fluid being pumped is held as it moves between the inlet and the outlet. The tip 38 of each vane 36 includes a bulbous sealing element, which is provided by an enlarged portion at the tip. In the illustrated embodiment the enlarged portion has a generally circular cross-section and acts to provide a seal between the vane and the inner surface of the housing 12. The sealing function provided by the tip of each vane performs two functions: firstly, it provides a seal against the pump housing to enable the pumping vanes to force the fluid from the first inlet to the first outlet, where it is squeezed into the outlet by the cam, and, secondly, it ensures separation of the first inlet and second outlet and second inlet and first outlet when the vanes are deflected by contact with the cammed surfaces, to prevent slippage of fluid from the outlet to the inlet past the cam surfaces.

[0097] In the present case the body of the impeller comprises a two piece body, which comprises as outer body 35 and an inner body 34 (which is shown in honeycomb hatching in FIG. 1). The outer body 35 is formed from an elastomeric material, such as natural rubber, neoprene or the like; this is typically the same material as the vanes, and the vanes and the outer body are contiguous with the outer body. The inner body 34 is formed of a plastics material, such as high density polyethylene or the like. Such a construction of impeller is preferred as it allows the elastomeric vanes and outer body to be mounded onto a comparatively rigid inner body. The inner body provides a suitable substrate for the moulding process, and allows for the moulded article to be readily removed from the housing. It will be apparent to the skilled person that other forms of flexible impeller are possible, e.g. where the entire impeller is formed from a flexible, elastomeric material.

[0098] The flexible impeller is mounted on a mounting hub 42, which in turn is mounted on the drive shaft 24. As can be seen, the hub comprises a tri-lobed form, wherein the inner and outer profiles of the hub are defined by three circular arcs 56 where each arc 60 is connected by a chord 62. The inner profile of the impeller has a corresponding inner profile, and the drive shaft has a corresponding outer profile. Accordingly, the shaft, hub and impeller are rotationally coupled together by the corresponding profiles.

[0099] A cover plate (not illustrated) is, of course, fitted to the outside of the housing to seal the impeller housing.

[0100] FIG. 2 shows an exploded view of a flexible impeller pump according to the present invention.

[0101] The ports in the housing 12 from the first inlet 14 and second outlet 20 can be seen. From this view circumferential support ribs 46 provided in the inlets and outlets can be clearly seen.

[0102] The impeller 22 is shown adjacent to the housing 12. Slots 48 can be seen on the end of the impeller, which are residuals from the injection moulding technique. The internal tri-lobe profile can be engaged by a fitting tool (not shown) during installation of the impeller in the housing. The tool is used to rotate the impeller as it is inserted, which advantageously allows for the vanes to be manoeuvred past the various impediments which the vanes abut against during insertion. For example, the vanes typically abut against the outer rim of the housing and the circumferential support ribs 46.

[0103] The hub 42 is shown, and its tri-lobe tubular form can be clearly seen. The central lumen 50 can be clearly seen, and, again, the tri-lobe profile can be seen. The hub 42 acts to rotationally lock the impeller 22 to the drive shaft 24. When the hub 42 is not in position, the impeller is free to rotate relative to the drive shaft. This allows for the impeller to be rotated when it is inserted into the housing, even where the drive shaft is rotationally locked in position. When the impeller is fully inserted, it is rotated to an appropriate point where the profiles of the drive shaft and the impeller are appropriately aligned, and the hub is inserted to rotationally couple the impeller and drive shaft together. The impeller comprises three threaded apertures 66 (best seen in FIG. 5) which provide an interface (extraction means) which is particularly useful during extraction of the hub, as described below.

[0104] FIGS. 3 and 4 show cross-sections of the impeller 22 and the vanes, in particular, in more detail. FIG. 3 shows a cross section of the impeller, and FIG. 4 shows the area marked c in close up.

[0105] Each vane comprises a tip 38, a root 40 and a stem 42 extending between the root and this tip. Between adjacent vanes 36 there is a trough 37, which defines and inter-vane volume. The tip of the vane defines a first sealing element 52. In the present embodiment the first sealing element is in the form of a bulbous portion, having a partial circular cross-section. In other words, the profile of the vane at the tip expands to form a portion of generally circular cross-section. This bulbous profile extends along the entire length of the vane. A second sealing element 54 is provided at about the midpoint of the vane, i.e. equidistant between the root and the tip of the vane. The second sealing element is defined by a bulbous protrusion from the leading side of the vane (the right side in the Figure). As can be seen, the protrusion has a cross-section of partial outer diameter of a circlethe illustrated protrusion forms a convex protrusion being an arc of about 90 degrees.

[0106] Referring back to FIG. 1, it can be seen that when the vane is passing around the cylindrical inner surface of the housing, the first sealing element located at the tip of the vane is in a sealing engagement with the inner surface of the housing. The vanes at this point are referred to as pumping vanes, and they are only very slightly bent. When the vanes meet the cammed surfaces 26, 28 the vanes are deflected and bent, and both the first sealing element and second sealing element engage with the cammed surface. Between each inlet and outlet at a cammed 26, 28 surface, there is a cammed sealing surface 56, 58. As the vanes pass across the cammed surface from an outlet to an inlet, the deflected vanes maintain a seal to isolate the inlet form the outlet. Where each vane provides only a single sealing element, the cammed sealing surface must be large enough to accommodate the single sealing element of two vanes such that there is at least one deflected vane providing a seal between the inlet and outlet. It will be appreciated that through the addition of the second sealing element between the root and tip of the blade the length of the cammed sealing surface can be greatly reduced. Correspondingly the overall length of the cammed surface can be reduced allowing the length of each cylindrical inner surface 30, 32 to be increased. By increasing the length of the cylindrical inner surfaces in this manner the number of utilised pumping vanes can be maximised whilst minimising the overall impeller diameter required.

[0107] Describing the operation of the pump, the impeller rotates and fluid is drawn in through the first inlet 14. The fluid is then carried around by the impeller in the inter-vane volume 44 between the vanes, and the fluid is retained by the sealing engagement between the vane and the housing surface. When the vanes reach the cammed surface of the first outlet 16, the cammed surface deflects the vanes and displaces the fluid, and the fluid is expelled through the outlet. It will be appreciated that, in order to do useful work, a pump must generate pressure/head at its outlet and the amount of pressure/head generated is of critical importance in selecting a pump for an application. As the pump is working the pressure/head applies a resultant force against the pumping vanes upstream of the cammed surface. This force is opposed by all of the upstream pumping vanes and their associated sealing elements, and the more pumping vanes between the outlet and the inlet, the better the pump is able to prevent slippage, i.e. leaking of fluid past the vanes back to the inlet port. While it is possible to improve sealing by, for example, forcing the pumping vanes against the inner housing surface with more force, this increases running friction, increasing energy consumption and wear. Shortening the vanes also allows the vanes to more effectively resist back pressure, but the vanes must have a suitable length to pass the cammed surface, and maintain an appropriate pumping capacity. Vanes made of stiffer materials can also better resist back pressure, but stiffer vanes wear more quickly and are less able to deflect at the cammed surface. Thus, it is desirable to maximise the number of pumping vanes available to resist this back pressure. In the embodiment of FIG. 1, it can be seen that there are 5-6 pumping vanes. If the vanes did not have the dual sealing elements, it would be necessary to have larger cammed sealing area, which would necessitate a reduction of the number of pumping vanes to 3-4. While this may not seem dramatic, the result of such a reduction in the number of pumping vanes would cause a significant reduction of the pressure/head the pump can generate, and consequently an increase in slippage.

[0108] Installation of an impeller into the housing, e.g. during routine maintenance, is performed as follows. The impeller is brought into position to be inserted into the housing. A fitting tool is connected to the impeller. The impeller is then pushed into the housing whilst being rotated via the fitting tool. Rotation is facilitated because the impeller is free to rotate about the drive shaft. This rotation eases the vanes into the housing, and allows the foremost edge of the vanes to be urged past various impediments to insertion such as the edge of the housing (in particular the cammed surfaces), the edges of the inlets and outlets, and the circumferential support ribs present in the outlets. Once the impeller is fully inserted into the housing, the impeller is rotated until it is correctly aligned with the drive shaft and the fitting tool is disengaged; correct alignment occurs three times per revolution with the profiles illustrated. The hub is then inserted to rotationally couple the impeller to the drive shaft. Retainers such as c-clips or the like can then fitted to lock the hub to the shaft and to lock the impeller to the hub. The housing cover is then fitted to seal the housing.

[0109] Suitable materials for the construction of the various components of a pump according to the present invention will be apparent to the skilled person. Typically the impeller will be formed from a resilient polymeric material, such as a natural or synthetic elastomer, e.g. natural rubber, nitrile rubber, or neoprene. The pump housing will typically be constructed from metal, e.g. a bronze or aluminium alloy, or stainless steel. The drive shaft is typically constructed from stainless steel, but other known drive shaft materials can be used, such as steel or aluminium. The impeller body typically is formed from a metal, such as a bronze or aluminium alloy, or from a strong plastics material such a glass reinforced plastic, HDPE or the like.

[0110] The pump housing may comprise a lining, e.g. a lining formed from plastics material. The lining defines the sealing surface against which the vanes of the flexible impeller press to form a sealing engagement. Such a lining can advantageously be produced from a polymer having a low coefficient of friction, therefore reducing friction between the impeller and the sealing surface of the housing compared to a metal surface. Furthermore, such a lining can allow convenient replacement of the lining when it becomes worn. The lining is typically substantially cylindrical, having apertures corresponding to the inlets and outlets provided in the housing.

[0111] FIG. 5 shows an impeller 22, along with a hub 42, which cooperates to mount and rotationally lock the impeller on a drive shaft. When the hub is inserted into the impeller, a snap ring 64 mounts in an annular groove on the impeller, and axially secures the hub within the lumen of the impeller. This allows for both a secure assembly, and for the hub to be used to assist in extraction of the impeller, as will be described below.

[0112] An extraction tool 80, for use in extracting the impeller is shown. It comprises a shaft 86, with a hex head 84 at the distal end. At the proximal end of the shaft there is mounted a body 87 having a circular flange 88. The head comprises a threaded central aperture which is mounted on a treaded portion of the shaft, such that rotation of the shaft relative to the body results in relative axial movement of the body relative to the body. Three bolts 89 are rotatably mounted in the flange, and they are evenly spaced circumferentially (120 degrees apart). The threaded portion of these bolts are adapted to engage with three corresponding threaded apertures 66 provided in the hub (this defines an extraction means or interface in the hub). Thus, when the bolts are screwed into the apertures in the hub, the hub and body 87 are secured together.

[0113] As best seen in FIG. 7, rotation of the shaft, which can be readily achieved using a suitable hex driver such as a spanner (wrench) or socket, results in movement of the tip 92 of the shaft 86 toward (clockwise rotation) or away (anti-clockwise rotation) from the drive shaft of the pump (not shown in this figure). As will be apparent to the skilled man, once the tip 92 of the shaft is brought into abutment with the drive shaft, continued clockwise rotation of the shaft will result in the hub been drawn (pulled) off the drive shaft. Because distal movement of the hub relative to the impeller is prevented\limited by the snap ring 64, the impeller will consequently also be pulled in a distal direction as the hub is moved. Thus, the shaft 92 can be rotated until the hub and impeller are pulled together from the drive shaft and pump housing.

[0114] Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention. For example, as mentioned above, the tri-lobed profiles of the hub and shaft/impeller can be replaced with another profile, such a spline or the like. Furthermore, the hub profile for engagement with the shaft need not be the same as the profile for the impellerthe important thing is that suitable profiles are selected which allow the impeller to be rotated independently of the shaft, and then be coupled to the shaft by the hub. The first and/or second sealing profiles could be defined by, for example, a blade profile, which has one or more sealing lips, or by any other protrusion. The impeller can be adapted for reversible operation, i.e. by providing a second sealing element on both sides of the vanes.