GB2243872A

GB2243872A - Pressure control in a pump

Info

Publication number: GB2243872A
Application number: GB9111670A
Authority: GB
Inventors: Terence Leslie Winnington; Nicholas John Beck
Original assignee: Kohler Mira Ltd
Current assignee: Kohler Mira Ltd
Priority date: 1988-07-08
Filing date: 1991-05-31
Publication date: 1991-11-13
Anticipated expiration: 2011-05-31
Also published as: GB9111670D0; GB2243872B

Abstract

A regenerative water pump has an impeller 6 mounted for rotation in a chamber 2 having an inlet 15 and an outlet 16 separated by a diffuser 17. The impeller 6 has radially extending blades 12. Means for providing a substantially constant delivery pressure over a range of flow rates comprises a relief valve 24 between the outlet passageway 23 and the inlet passageway 22. At delivery pressures above a predetermined pressure (Px, figure 5) the valve opens thereby relieving the excess pressure. The pump may be used in ablutionary installations; for example, showers. <IMAGE>

Description

PUMP This invention relates to pumps, in particular though not exclusively water pumps for use in ablutionary installations, for example showers.

Mixing valves for mixing hot and cold water to provide a blended water of pre-determined temperature for showering are well known and require minimum pressures for the hot and cold water supplies to provide adequate flow rate over the operating temperature range.

In certain installations where the pressure of the hot and/or cold water supplies is less than the necessary minimum, it is known to use a pump to increase the pressure.

It is also known to pump the hot and/or cold water supplies even where the pressures exceed the minimum for normal showering to increase substantially the flow rate to provide a so-called "power shower".

Both centrifugal and regenerative type pumps are commonly used in shower installations but neither is completely satisfactory. Centrifugal pumps are prone to formation of air locks in the impeller housing when pumping hot water which contains large quantities of entrained air. Regenerative pumps are susceptible to variations in the delivery pressure with changes in the flow rate, for example on adjusting the selected temperature of the blended water, which adversely affects the operation of the valve. In addition, the known centrifugal and regenerative type pumps are often noisy and inefficient.

It is an object of the present invention to provide a pump suitable for use in ablutionary installations such as a shower which mitigates at least some of the problems and disadvantages of the known centrifugal and regenerative pumps afore-mentioned.

According to the present invention, we provide a pump, preferably a regenerative type pump, comprising a pump casing having a fluid chamber provided with an inlet and an outlet, an impeller mounted for rotation in the chamber, the impeller having a plurality of radially extending blades, and means arranged to control gradually shut-off of the blades in the region of the inlet and/or outlet.

By gradually controlling blade shut-off on entry and/or exit of fluid to and from the chamber, pressure pulses and hence noise levels in operation of the pump are reduced.

Conveniently, the blade shut-off means is located opposite and radially outwardly of the peripheral edge of the impeller and is tapered in the direction of rotation of the impeller to control gradually shut-off of the blades at the peripheral edge of the impeller.

More particularly, as the impeller rotates, fluid is picked up in the radially extending recesses defined between adjacent blades and is discharged from the recesses at the peripheral edge of the impeller and the blade shut-off means controls gradually the exposure of the ends of the recesses in the region of the inlet and/or outlet.

Preferably, the blade shut-off means is arranged to reduce gradually blade shut-off in the direction of rotation of the impeller at the inlet (i.e. to open the ends of the recesses) and/or to increase gradually blade shut-off in the direction of rotation of the impeller at the outlet (i.e. to close the ends of the recesses).

In a preferred arrangement, the blade shut-off means comprises the tapered end portions of a diffuser arranged to separate the inlet and the outlet.

Advantageously, the fluid chamber is divided into two channels between the inlet and the outlet, one on each side of the impeller, with the inlet and outlet being common to each channel, and the impeller has a respective set of blades on each side. For example, the pump casing and impeller may be constructed with limited clearance between the sidewall of the chamber and the peripheral edge of the impeller.

Alternatively, a flow splitter ring may be positioned on the sidewall of the chamber opposite the peripheral edge of the impeller with limited clearance therebetween.

By this arrangement, the fluid entering the chamber is split into two streams passing along the channels on opposite sides of the impeller and is recombined into a single stream on exiting the chamber.

The blades of one set may be aligned with or offset relative to the blades of the other set. For example, each blade of one set may extend between two adjacent blades of the other set.

The blades may be straight or curved in the radial direction. Where the blades are curved, the curvature is preferably in the direction of rotation of the impeller. In this way, fluid pick-up is improved leading to increased pump efficiency.

The blades may be of uniform (regular) or nonuniform (random) pitch. Where blades of non-uniform pitch are used, pump noise may be reduced as compared with blades of uniform pitch due to the noise spectrum being spread over a range of frequencies.

Preferably, means is provided for maintaining the fluid delivery pressure substantially constant over a range of fluid flow rates. This is of particular benefit in ablutionary shower installations employing a mixing valve for mixing and blending hot and cold water where the hot and/or cold supplies may be pumped to provide a constant delivery pressure over the ablutionary operating temperature range irrespective of variations in the flow rate caused by temperature changes of the blended water.

Advantageously, the constant pressure means comprises a valve constructed and arranged to relieve excess fluid pressure on the delivery side of the pump.

Conveniently, the relief valve comprises a valve member biassed to a closed position and movable to an open position against the biassing to release excess fluid pressure on the delivery side when the delivery pressure exceeds a pre-determined value sufficient to overcome the biassing. In this way, the delivery pressure is maintained substantially constant.

Preferably, the relief valve is arranged between the inlet and outlet sides and is operable to relieve excess pressure on the delivery side by return of fluid to the inlet side.

In a preferred arrangement the valve member is biassed by a spring to engage a valve seating and close a port opening to the delivery side. The spring biassing may be adjustable to select the pressure required to overcome the biassing and move the valve member to disengage the valve seating and open the port for relieving excess pressure on the delivery side.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings wherein: FIGURE 1 is an end view, partly in section of a first embodiment of a regenerative pump according to the invention with the cover plate removed to show the components of the pump; FIGURE 2 is a section on the line 2-2 of Figure 1; FIGURE 3 is a section on the line 3-3 of Figure 1; FIGURE 4 shows in detail, to an enlarged scale, part of the impeller shown in Figures 1 to 3; FIGURE 5 is a graph showing the variation of delivery pressure with flow rate; FIGURE 6 is an end view similar to Figure 1 of a second embodiment of a regenerative pump according to the present invention; FIGURE 7 is a section on the line 7-7 of Figure 6; FIGURE 8 shows in detail, to an enlarged scale, part of the impeller shown in Figure 6;; FIGURE 9 is a plan view of an alternative impeller; and FIGURE 10 is a section on the line 10-10 of Figure 9.

The regenerative water pump shown in Figures 1 to 4 of the accompanying drawings comprises a pump casing 1 having a fluid chamber 2 defined by a main pump body 3 and a cover plate 4 secured to the body 3 by releasable fasteners such as screws (not shown) and sealed by an O-ring 5.

Mounted in the casing 1 is an impeller 6 having close fitting thrust washers 7 on opposed sides and a central hub portion 8 releasably secured to the end of a shaft 9 driven by a motor (not shown) by means of which the impeller 6 is rotatable in a clockwise direction as shown by arrow A in Figure 1.

Hub portion 8 is connected by radial spokes 10 to a rim portion 11 positioned in the fluid chamber 2.

The rim portion 11 is disc-shaped and has a respective set of radially extending blades 12 on each side.

Each blade 12 is curved in the direction of its radial length and defines with the adjacent blades 12 a plurality of radially extending recesses 13 on each side of the impeller 6.

The curvature of the blades 12 is in the direction of rotation of the impeller 6 and the recesses 13 are open at the peripheral edge of the impeller 6. As a result, pick-up of water by the blades 12 and discharge from the recesses 13 is more effective leading to improved efficiency of the pump.

As best shown in Figure 4, the blades 12 are of non-uniform or random pitch so that the noise spectrum obtained'on rotation of the impeller 6 is spread over a range of frequencies. As a result, operating noise levels are reduced as compared with an impeller having blades of uniform or regular pitch which produce a fixed frequency drone.

Mounted on the outer sidewall of the chamber 2 aligned with the impeller 6 is a circumferentially extending splitter ring 14 of generally C-shape. The splitter ring 14 extends with limited clearance for approximately 3000 around the peripheral edge of the impeller 6 and divides the fluid chamber 2 into two channels 2a,2b having a common inlet 15 and a common outlet 16 provided in the outer sidewall of the chamber 2 at opposite ends of the splitter ring 14.

Also mounted on the outer sidewall of the fluid chamber 2 is a diffuser 17 arranged to extend with limited clearance around the peripheral edge of the impeller 6 to separate the inlet 15 and outlet 16 between the ends of the splitter ring 14.

By this arrangement, fluid entering the chamber 2 is split at the inlet 15 into two separate streams which pass along the channels 2a,2b on opposite sides of the impeller 6 and are recombined at the outlet 16 on exiting the chamber 2. As a result, the effect of the sets of blades 12 positioned on opposite sides of the impeller 6 is improved leading to increased efficiency of the pump.

In addition to separating the inlet 15 and outlet 16, the opposed ends of the diffuser 17 are forked to form, at each end, respective circumferentially extending beaks 18 positioned opposite and radially outwards of each set of blades 12 in the region of the inlet 15 and the outlet 16.

The beaks 18 shut-off the blades 12 at the peripheral edge of the impeller 6 and each beak 18 is tapered in the circumferential direction towards the distal end.

As a result, in the region of the inlet 15, blade shut-off is gradually reduced in the direction of rotation of the impeller 6 and, in the region of the outlet 16, blade shut-off is gradually increased in the direction of rotation of the impeller 6. That is to say, as the impeller 6 rotates, the radially outer ends of the recesses 13 are gradually opened in the direction of rotation at the inlet 15 and are gradually closed in the direction of rotation at the outlet 16.

In this way, fluid pick-up and discharge is controlled to reduce pressure pulses at the inlet 15 and outlet 16 leading to further reduction in noise levels.

The pump casing 1 has an inlet connection 20 and an outlet connection 21 for mounting the pump in the hot or cold supply to a mixing valve (not shown) of an ablutionary shower installation.

An inlet passageway 22 extends between the inlet connection 20 and the inlet 15 to the chamber 2, and an outlet passageway 23 extends between the outlet 16 from the chamber 2 and the outlet connection 21.

Mounted in the casing 1 between the passageways 22,23 is a relief valve 24 arranged to provide a substantially constant delivery pressure over a range of flow rates.

The valve 24 comprises a valve body 25 having a valve member 26 biassed by a spring 27 to engage a valve seat 28 and close a relief port 29 opening to the outlet passageway 23.

Referring now to Figure 5, the delivery pressure varies linearly with flow as shown by the unbroken line X. The rating of the spring 27 of the pressure relief valve 22 is chosen so that, at pressures lower than a pre-determined pressure Px, the valve member 26 engages the valve seat 28 to close the relief port 29 under the biassing of the spring 27. With the inlet port 29 closed, the outlet passageway 23 is isolated from the inlet passageway 22 and the delivery pressure varies linearly with flow as shown by the lower part X' of line X.

At pressures higher than pressure Px, the valve member 26 is moved against the biassing of the spring 27 and disengages the valve seat 28 to open the inlet port 29. With the inlet port 29 open, the outlet passageway 23 and the inlet passageway 22 are connected and fluid flows from the outlet passageway 23 through the valve body 25 to the inlet passageway 22 relieving the excess pressure so that the delivery pressure remains substantially constant over a range of flow rates as shown by the broken line Y.

In this way, the operating characteristics of the pump can be tailored to provide a substantially constant delivery pressure independent of flow rate over the ablutionary operating temperature range. As a result, the valve is not affected by variations in the flow rate so that smooth selection and control of the temperature of the blended hot and cold supplies is ensured.

Referring now to Figures 6 to 8, a second embodiment of regenerative water pump is shown in which the flow splitter ring is omitted and the impeller and diffuser are modified. Like reference numerals in the series 100 are used to indicate parts corresponding to the first embodiment above-described.

As best shown in Figure 6, the rim portion 111 of the impeller 106 extends with limited clearance adjacent to the outer sidewall of the chamber 102 to divide the chamber 102 into two channels 102a,102b extending on opposed sides of the impeller 106 between the inlet 115 and the outlet 116 with the diffuser 117 being recessed into the outer sidewall to separate the inlet 115 and the outlet 116.

The curved blades 112 on each side of the impeller 106 are of uniform or regular pitch (Figure 8) with the blades 112 on one side being offset relative to the blades 112 on the other side (Figure 7).

The diffuser 117 has a single beak 118 at each end which is tapered towards the distal end and is symmetric about the centre line of the impeller 106 to control blade shut-off on both sides of the impeller 106 at the inlet 115 and the outlet 116.

In other respects, the construction and operation of this embodiment is similar to that of the first embodiment and will be readily understood from the description of the first embodiment.

Referring now to Figures 9 and 10, there is shown a alternative impeller 206 which may be used in place of the impellers 6,106 of the embodiments above-described, like reference numerals in the series 200 being used to indicate corresponding parts.

The impeller 206 has a central hub portion 209 connected by radial spokes 210 to a rim portion 211 comprising an inner ring 211a from which a plurality of curved blades 212 of uniform or regular pitch extend radially and are connected by an outer ring 211b at the peripheral edge of the impeller 206. In a modification (not shown), the outer ring 211b may be omitted. With this construction, fluid can pass from one side of the impeller 206 to the other through the gaps between the blades 206. As a result, friction on the impeller 206 may be reduced thereby improving efficiency.

As best shown in Figure 10, the outer ring 211b is of generally triangular section having opposed curved surfaces meeting at a radially inwardly directed apex mid-way between the opposed sides of the impeller. The curved surfaces provide a contoured flow path' which may enhance further the flow characteristics of the fluid.

It will be understood that the invention is not limited to the embodiments above-described, for example whilst the impeller blades are preferably curved as described this is not essential and the blades may be straight. Also the blades may be of uniform or nonuniform pitch as desired.

The impeller may have blades on both sides or one side only of a disc-shaped rim portion. Where the blaes are on both sides, the blades on side may be aligned with or offset relative to the blades on the other side, for example each blade on one side may extend between two adjacent blades on the other side.

Where the blades are on one side only, the inlet and outlet may be arranged to communicate with that side only. Also the beaks of the diffuser for controlling blade shut-off at the inlet and outlet may be modified accordingly.

The diffuser may be constructed to control blade shut-off at both the inlet and the outlet or at one only of the inlet and outlet.

The end portion(s) of the diffuser may be of any suitable size and shape for controlling blade shut-off and the diffuser may be formed as an integral part of the pump casing.

The pressure relief valve may be of any suitable construction arranged to maintain the delivery pressure substantially constant for a range of flow rates. For example, the relief valve may reduce excess pressure on the delivery side by return flow of fluid to the inlet side for recirculation as described or by discharge of fluid to waste.

The pressure relief valve may be adjustable to set the required constant delivery pressure. For example, the spring biassing of the valve member as described may be adjustable to control the pressure required to open the relief port.

It will be understood that the invented pump has a number of features which contribute to an improvement in performance and/or reduction in noise, in particular the features of the diffuser, curved impeller blades, non-uniform or random impeller blade pitch, axial flow path between impeller blades, and pressure relief-valve and that each of these features may be provided separately or in combination with any one or more of the other features.

Finally, whilst the invention has been described with reference to the use of the pump in the water supply to a mixing valve for a shower, it will be appreciated that the pump may be used in any ablutionary installation requiring boosting of the water pressure, hot and/or cold. Also, it is envisaged within the scope of the invention that the pump may have application for pumping water or other fluids in installations other than ablutionary installations.

Claims

Claims:

1. A pump, preferably a regenerative type pump, comprising a pump casing having a fluid chamber provided with an inlet and an outlet, an impeller mounted for rotation in the chamber, and means for maintaining the fluid delivery pressure substantially constant over a range of fluid flow rates.

2. A pump, preferably a regenerative type pump, comprising a pump casing having a fluid chamber provided with an inlet and an outlet, an impeller mounted for rotation in the chamber, the impeller having a plurality of radially extending blades, and means arranged to control gradually shut-off of the blades in the region of the inlet and/or outlet.

3. A pump according to Claim 2 wherein the blade shut-off means is located opposite and radially outwardly of the peripheral edge of the impeller and is tapered in the direction of rotation of the impeller to control gradually shut-off of the blades at the peripheral edge of the impeller.

4. A pump according to Claim 3 wherein the blades define a plurality of radially extending recesses and the blade shut-off means controls gradually the exposure of the ends of the recesses at the peripheral edge of the impeller in the region of the inlet and/or outlet.

5. A pump according to Claim 3 or Claim4 wherein the blade snut-off means is arranged to reduce gradually blade snut-off in the direction of rotation of the impeller at the inlet and/or to increase gradually blade snut-off in the direction of rotation of the impeller at the outlet.

6. A pump according to any one of Claims 3 to 5 wherein the blade shut-off means comprises the tapered end portion(s) of a diffuser arranged to separate the inlet and the outlet.

7. A pump according to any one of Claims 2 to 6 wherein the blade shut-off means controls shutoff of the blades at the inlet and the outlet.

8. A pump according to any one of Claims 2 to 7 wherein the fluid chamber is divided into two channels between the inlet and the outlet, one on each side of the impeller, with the inlet and outlet being common to each channel, and the impeller has a respective set of blades on each side.

9. A pump according to Claim 8 wherein the impeller extends with limited clearance between the peripheral edge and the sidewall of the chamber.

10. A pump according to Claim 8 wherein the impeller extends with limited clearance between the peripheral edge and a flow splitter ring mounted on the sidewall of the chamber between the inlet and the outlet.

11. A pump according to any one of Claims 8 to 10 wherein the blades of one set are aligned with the blades of the other set.

12. A pump according to any one of Claims 8 to 10 wherein the blades of one set are offset relative to the blades of the other set.

13. A pump according to any one of Claims 2 to 12 wherein each blade is straight in the direction of its length.

14. A pump according to any one of Claims 2 to 12 wherein each blade is curved in the direction of its length.

15. A pump according to Claim 14 wherein the blades are curved in the direction of rotation of the impeller.

16. A pump according to any one of Claims 2 to 15 wherein the blades are of uniform pitch.

17. A pump according to any one of Claims 2 to 15 wherein the blades are of non-uniform pitch.

18. A pump according to any one of Claims 2 to 17 wherein means is provided for maintaining the fluid delivery pressure substantially constant over a range of fluid flow rates.

19. A pump according to Claim 18 wherein the constant pressure means comprises a valve arranged to relieve excess fluid pressure on the delivery side of the pump.

20. A pump according to Claim 19 wherein the relief valve comprises a valve member biassed to a closed position and movable to an open position against the biassing to release excess fluid pressure on the delivery side when the delivery pressure exceeds a predetermined value sufficient to overcome the biassing.

21. A pump according to Claim 20 wherein the relief valve is operable to relieve excess pressure on the delivery side by return of fluid to the inlet side.

22. A pump according to Claim 20 or Claim21 wherein the valve member is biassed by a spring to engage a valve seating and close a relief port opening to the delivery side.

23. A pump according to Claim 22 wherein the spring biassing is adjustable.

24. A purtip according to any one of Claims 2 to 23 wherein the impeller comprises a central hub portion for mounting on a driven shaft and connected te a åisc-shapea rim portion having the blades on at least one side.

25. A pump according to any one of Claims 2 to 24 wherein the pump casing comprises a main body and a cover plate releasably secured to the body to define the chamber.

26. A pump according to any one of Claims 2 to 25 wherein the pump casing has respective internal passageways extending between the inlet and an inlet connector and between the outlet and an outlet connector.

27. A pump substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

28. A pump substantially as hereinbefore described with reference to Figures 6 to 8 of the accompanying drawings.

29. A pump substantially as hereinbefore described with reference to either Figures 1 to 5 or Figures 6 to 8 of the accompanying drawings as modified by Figures 9 and 10 of the accompanying drawings.

30. An ablutionary shower installation including a mixing valve for mixing hot and water supplies and a pump according to any one of Claims 2 to 29 for pumping one of the hot and cold supplies.

31. A pump, preferably a regenerative type pump, comprising a pump casing having a fluid chamber provided with an inlet and an outlet, and an impeller rotatably mounted in the chamber, the impeller having a plurality of radially extending blades with each blade being curved in the direction of the length thereof.

32. A pump, preferably a regenerative type pump, comprising a pump casing having a fluid chamber provided witr an inlet and an outlet, and an impeller mounted for rotation in the chamber, the impeller having a plurality of radially extending blades with the blades being of non-uniform pitch.

33. A pump, preferably a regenerative type pump, comprising a pump casing having a fluid chamber provided with an inlet and an outlet, and an impeller mounted for rotation in the chamber, the impeller being a close fit in the chamber in the radial direction and being constructed and arranged to permit permit axial flow of fluid from one side of the impeller to the other side between the blades.