GB2443423A

GB2443423A - Water pump

Info

Publication number: GB2443423A
Application number: GB0621863A
Authority: GB
Inventors: Matthew Robert Riley
Original assignee: Aqualisa Products Ltd
Current assignee: Aqualisa Products Ltd
Priority date: 2006-11-02
Filing date: 2006-11-02
Publication date: 2008-05-07
Also published as: GB0621863D0

Abstract

A water pump for use downstream of a water mixing flow rate control valve of a shower assembly. The pump has an inlet 22 for connection to the flow rate control valve, an outlet 26 for connection to a shower outlet and a pump chamber 24 configured to pump water from the inlet to the outlet. A bleed channel 28 including a bleed valve 30 selectively connects the outlet to the inlet in response to reduced inlet water pressure to reduce cavitation in the pump chamber when the control valve flow is very low. The bleed valve comprises a member (56 Fig. 6) spring biased to close the bleed channel but exposed on its underside to inlet pressure and separated from atmosphere by a diaphragm 64. Once inlet pressure falls atmospheric pressure opens the valve to allow bleed flow.

Description

WATER PUMP

The present invention relates to a water pump, in particular for use in a mixed water delivery system, such as a domestic shower arrangement or batWbasin water delivery arrangement, where the pump is located downstream of a flow rate control valve, and relates to a method of pumping water with this arrangement.

A wide variety of valves are known for mixed water delivery systems, such as domestic shower arrangements, which vary flow rate and mix hot and cold water to provide a desired outlet water temperature. Where supply water pressure for one or both of the hot and cold water inlets is relatively low, it is also known to provide one or more pumps for increasing the pressure and flow rate of the hot andlor cold water supplies provided to the inlets of these valves.

The present invention is at least partly based on consideration of an alternative arrangement where a single pump is provided downstream of the one or more control valves. In particular, the present application considers the problem that can arise when a user uses the flow rate control valve to provide only a small flow rate such that a large restriction is provided by the flow rate control valve at the inlet to the pump. As a result of this restriction, there can occur a significant drop in pressure both at the inlet of the pump and upstream of the pump such that cavitation occurs for instance in the flow rate control valve and causes noise in the pump due to the cavitation gas entering the pump. Si

According to the present invention there is provided a method of pumping water from downstream of a flow rate control valve using a valve with an inlet for connection to the flow rate control valve, an outlet and a pump chamber connecting the inlet to the outlet and configured to pump water from the inlet to the outlet, the method including: selectively bleeding water from the outlet to the inlet in response to reduced water pressure at the inlet so as to reduce cavitation upstream of the pump chamber.

According to the present invention, there is also provided a water pump for use downstream of a flow rate control valve of a mixed water delivery system, the pump having: an inlet for connection to a flow rate control valve; an outlet; a pump chamber connecting the inlet to the outlet and configured to pump water from the inlet to the outlet; and a bleed channel including a bleed valve for selectively connecting the outlet to the inlet in response to reduced water pressure at the inlet so as to reduce cavitation upstream of the pump chamber.

In this way, when flow to the inlet of the pump is restricted, for instance by means of the flow rate control valve, the bleed channel allows water to recirculate from the outlet to the inlet so as to keep the water pressure both at the inlet and also upstream of the pump above a predetermined value and, hence, prevent cavitation upstream of the pump. -3..

Preferably, the bleed valve provides an aperture of variable cross-section connecting the outlet to the inlet and the pump is configured to vary the cross-section of the aperture provided by the bleed valve according to the water pressure at the inlet.

In this way, it is possible to provide only the required bleed of water from the outlet to the inlet to prevent cavitation whilst otherwise maintaining maximum efficiency for the pump. As restriction of water into the inlet of the pump is increased, the cross-section of the aperture provided by the bleed valve is also increased so as to allow increased bleeding of water from the outlet to the inlet and increased recirculation of water. In this way, irrespective of the restriction provided at the inlet to the pump, the water pressure at the inlet of the pump and upstream of the pump can always be maintained sufficiently high as to prevent cavitation.

Preferably, the water pump further includes a bleed valve actuator for controlling the bleed valve.

The actuator can be used automatically to control the bleed valve so as to prevent cavitation.

Preferably, the bleed valve actuator is responsive to a difference between water pressure at the inlet and atmospheric pressure outside the pump.

In this respect, it is important to note that it is the actual pressure at the inlet or upstream of the pump that determines whether or not cavitation occurs, rather than any differential pressure between the inlet and outlet of the pump. Hence, the bleed valve can be controlled according to the difference in pressure between the water pressure at the inlet and atmospheric pressure.

Preferably, the bleed valve actuator includes a flexible diaphragm having an inner surface in communication with inlet water pressure and an outer surface in contact with atmospheric pressure.

The flexible diaphragm can be provided within the bleed channel with the bleed channel in direct communication with the inlet such that the water pressure within the bleed channel is the same as the water pressure at the inlet. The bleed channel can take the form of a cavity in which the diaphragm is mounted such that its inner surface is in contact with the water in the bleed channel. An outer wall of the bleed channel can include an opening providing communication of outside ambient air with the outer surface of the diaphragm.

Thus, the diaphragm preferably forms at least part of a wall of the bleed channel.

In this way, the diaphragm directly responds to differences in pressure between the water inside the bleed channel and atmospheric pressure outside the pump.

Preferably, the bleed channel extends between a valve aperture at the outlet and a connecting aperture at the inlet. The bleed valve may include a valve member resiliently biased in a position to close the bleed aperture and the diaphragm, in response to a drop in pressure at the inlet, may act on the valve member so as to move the valve member in such a way as to open the bleed aperture.

Thus, the water in the bleed channel permanently communicates with water at the inlet such that it is at the same pressure as water at the inlet. On the other hand, the bleed channel only communicates with the outlet by means of the valve aperture which is selectively opened or closed by means of the diaphragm.

Preferably, the pump further includes a valve spring for biasing the diaphragm outwardly of the bleed channel wherein a drop in pressure at the inlet causes the diaphragm to move inwardly of the bleed channel against the bias of the valve spring so as to move the valve member into the outlet in such a way as to open the bleed aperture.

In this way, with unrestricted flow to the inlet of the pump, the valve spring holds the bleed aperture closed so as to maintain maximum efficiency for the pump. Only when there is a drop in pressure at the inlet beyond a predetermined amount does the difference in pressure between the water in the bleed channel (corresponding to the pressure at the inlet) and atmospheric pressure cause the diaphragm to move against the bias of the valve spring and open the bleed aperture.

Preferably, the pump further includes a movable pump element within the pump chamber, a motor for moving the pump element within the pump chamber so as to pump water from the inlet to the outlet and a motor controller configured to operate the motor at constant speed.

A simplified pump can thus be provided with a motor which always runs at a constant speed. When water flow is restricted by a control valve upstream of the pump, the pump allows a bleed of water from the outlet to the inlet. Although this reduces efficiency of the pump, the overall design is simplified, because it is not necessary to control the motor speed of the pump in any way.

According to the present invention, there may also be provided a shower assembly including a flow rate control valve having a hot water inlet, a cold water inlet and a control outlet wherein the inlet of the water pump described above is connected to the control outlet of the flow rate control valve.

Preferably, the flow rate control valve includes a hot water valve defining a throughhole of variable cross-section to control the flow of hot water to the control outlet and an independently controllable cold water valve defining a throughhole of variable cross-section to control the flow of cold water to the control outlet.

The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates schematically a shower assembly embodying the present invention; Figure 2 illustrates schematically a pump embodying the present invention; Figures 3, 4 and 5 illustrate various views of the housing of a pump embodying the present invention; Figure 6 illustrates a cross-section through the valve actuation part of the pump of Figure3,4ands;and Figures 7(a), (b) and (c) illustrate component parts of the valve actuation part.

Domestic showers are well known where hot and cold water is mixed according to the user's requirements and then provided to a shower handset. The present invention is also applicable to other mixed water delivery systems, for instance supplying baths and/or basins.

Figure 1 illustrates an arrangement including a pump embodying the present invention. In particular, a shower assembly 2 is connected to a hot water inlet 4 and a cold water inlet 6. The shower assembly 2 controls the proportionate mix of hot and cold water and overall flow rate to an outlet 8 connected to a shower handset 10. In the illustrated embodiment, a remote controller 12 is provided for controlling operation of the shower assembly 2 and includes controls preferably allowing a user to control the temperature of the mixed water at the outlet 8 and also the overall flow rate.

As illustrated, the shower assembly 2 includes a flow rate control valve unit 14 and a water pump 20 downstream of the flow rate control valve unit 14.

For the purposes of understanding the present invention, it is the fact that the flow rate control valve unit 14 controls and, in particular, restricts, flow to the water pump 20 that is important. However, it will be appreciated that, in practice, the flow rate control valve unit 14 will also control the proportionate mix of hot and cold water from the hot water inlet 4 and cold water inlet 6. In a preferred embodiment, the flow rate control valve unit 14 includes a hot water valve 16 and a cold water valve 18 which are controllable independently of one another to control flow from the hot water inlet 4 and cold water inlet 6 respectively. In this way, not only can the proportion of hot and cold water be varied, but also the overall flow rate through the shower assembly 2 can be controlled.

It should be appreciated that the water pump 20 of the present invention can be used in any other shower anangement where water flow to the water pump might be restricted by the user when controlling flow rate or temperature.

Figure 2 illustrates schematically a valve 20 embodying the present invention.

The valve 20 includes an inlet 22 to be connected to the outlet of a flow rate control valve such as the flow rate control valve 14 described above. The inlet 22 feeds water to a pump chamber 24 which pumps the water to an outlet 26, for instance for connection to the outlet 8 described above.

A bleed channel 28 is provided for selectively connecting the outlet 26 to the inlet 22. In particular, a bleed valve 30 is provided in the bleed channel 28 for selectively opening and closing flow through the bleed channel 28.

The means by which pumping is achieved can take any known form. Irrespective, the pump chamber 24 is expected to include a movable pump element 32 which is moved, for instance rotated, by means of a motor 34. In this respect, a motor controller 36 may be provided to control the motor 34 and, hence, the pumping operation of the water pump 20.

In a preferred embodiment, the motor controller 36 controls the motor 34 to run at a constant speed. Hence, the motor controller 36 acts merely to turn the pump on or off.

In an arrangement such as described with reference to Figure 1, the motor controller 36 can operate in conjunction with the remote controller 12 such that the motor 34 is turned on when the flow rate control valve unit 14 enables flow through the shower assembly 2.

When the water flow to the inlet 22 of the water pump 20 is restricted, for instance where a user has chosen a low flow rate and a flow rate control valve upstream of the water pump 20 restricts the flow to the water pump 20, the water pressure at the inlet 22 and upstream toward the flow rate control valve can be reduced below atmospheric pressure.

When this occurs, it is possible for gas/air to be released from the water. This effect is generally referred to as cavitation and the pressure below atmosphere at which it occurs is a function of the water temperature. In one embodiment, the maximum mixed water temperature might be approximately 55 degC causing cavitation to occur at approximately 0.7 bar below atmosphere. As the pressure reduces, cavitation occurs first for the higher temperatures so the maximum mixed water temperature is the worse case. When cavitation occurs, the gas bubbles enter the inlet 22 of the water pump causing an unacceptable level of audible noise as they pass into higher pressure regions and collapse.

Cavitation can also cause wear on the internal parts of the pump.

To avoid or at least reduce cavitation, the bleed valve 30 is arranged to open so as to allow water from the outlet 26 to bleed back to the inlet 22. In other words, the bleed channel 28 thus allows recirculation of some of the water being pumped by the water pump 20. Although this reduces the efficiency of the water pump 20 to some degree, it reduces the pressure drop at the inlet 22 or upstream portions of the pump chamber 24.

Furthermore, of course, since the user has already decided to have a low flow rate by restricting the flow upstream of the water pump 20, it is unnecessary anyway for the water pump 20 to provide its maximum pumping flow rate.

In preferred embodiments, the bleed valve 30 can vary the amount by which the bleed channel 28 is opened such that as flow to the inlet 22 is increased, the flow of recirculating water through the bleed channel 28 is similarly increased. In particular, in preferred embodiments, the bleed valve 30 is arranged to ensure that the pressure drop at the inlet 22 does not fall below approximately 0.6 bar below atmosphere.

In preferred embodiments, the bleed valve 30 works automatically according to the pressure at the inlet 22. This may be achieved by actuating the bleed valve 30 according to the difference in pressure between the water pressure at the inlet 22 and atmospheric pressure. In this respect, a preferred embodiment will be described below.

S

The water pump of Figure 3 includes a housing 40 defining within it the pump chamber 24. As illustrated, the housing 40 and pump chamber 24 are generally cylindrical and the water inlet 22 is provided axially at one end of the housing 40. A motor (not illustrated) may be provided on the other end of the housing 40 for driving any suitable pump element within the pump chamber 24. The outlet 26 is located at a circumferential side surface of the housing 40 and the bleed channel 28 is provided in a manner extending between the outlet 26 and inlet 22 around the housing 40. The bleed valve 30 is provided along part of the bleed channel 28.

Figure 4 illustrates the water pump of Figure 3 from below with the bottom of the housing 40 removed so as to show the inside of the pump chamber 24. As illustrated, the inlet 22 feeds into the pump chamber 24 axially at the top of the pump chamber 24. An opening 42 is provided in the circumferential side wall of the housing 40 and pump chamber 24 connecting with the outlet 26.

Figure 4 also illustrates a connection aperture 44 which connects the bleed channel 28 with the inlet 22.

In Figure 5, the bleed channel 28 is shown with the bleed valve actuator cap 50 (illustrated in Figure 3) removed so as to expose the interior of a portion of the bleed channel 28. A cross-section through this portion of the bleed channel 28 is illustrated in Figure 6.

The bleed channel 28 is formed with a valve chamber 52 along its length, the valve chamber being positioned above the outlet 26 and communicating with the outlet 26 through a valve aperture 54. A valve member 56 is arranged to move within the valve aperture 54 and, as illustrated in Figure 6, to close the valve aperture 54.

The valve chamber 52 is closed by means of the cap 50. A coil spring 58 acts between a surrounding surface of the valve aperture 54 and a flange 60 of the valve member 56 so as to bias the valve member 56 towards the cap 50 and into the position illustrated in Figure 6 where the valve member 56 closes the valve aperture 54.

As illustrated in Figure 6, the cap 50 includes a throughhole 62. A flexible diaphragm 64 is provided internally of the cap 50 and maintains a seal for preventing water escaping from the bleed channel 28 to atmosphere. In the illustrated embodiment, this may be achieved by clamping the flexible diaphragm 64 to the outer walls of the valve chamber 52 around its periphery by means of the cap 50.

Figures 7(a), (b) and (c) illustrate the cap 50, diaphragm 64 and valve member 56 respectively.

From the above, it will be appreciated that the bleed channel 28 (by means of the connecting aperture 44) provides direct communication between water at the inlet 22 and water in the valve chamber 52 portion of the bleed channel 28 such that the water in the valve chamber 52 is at substantially the same pressure as the pressure of water at the inlet 22. Thus, when water flow to the inlet 22 is restricted and the water pressure at the inlet 22 drops, the water pressure in the valve chamber 52 drops similarly.

The diaphragm 64 acts as an actuator for the valve member 56. In particular, as the water pressure in the valve chamber 52 drops, atmospheric pressure provided via the throughhole 62 in the cap 50 on the outer surface of the diaphragm 64 causes the inner surface of the diaphragm 64 to act on the flange 60 of the valve member 56 such that the diagram 64 and flange 60 both move inwardly of the valve chamber 52 against the resilient resistance of the spring 58. In this way, the valve member 56 is moved into the outlet 26.

In the illustrated embodiment, the valve 56 is formed as an elongate member extending from an end 66 for closing the valve aperture 54. Away from the end 66, at least one aperture 68 is provided through the side walls of the valve member 56. When the diaphragm 64 acts to move the valve member 56 into the outlet 26, the sealing end wall 66 is moved into the outlet 26 and the aperture 68 becomes exposed to water in the outlet 26.

In this way, water from the outlet 26 is able to bleed through the aperture 68 and valve aperture 54 into the valve chamber 52 and bleed channel 28.

In this preferred embodiment, as the water pressure at the inlet 22 and bleed channel 28 drops further, the difference in pressure across the diaphragm 64 causes the diaphragm 64 to move further against the resistance of the spring 58 and, hence, allows more bleeding of water from the outlet to the inlet so as to raise once again the water pressure at the inlet. This feedback loop enables the appropriate amount of recirculation of water via the bleed channel 28 according to restrictions to the water flow to the inlet 22.

It should be appreciated that other types of valve could similarly be controlled by a diaphragm-type arrangement or any other valve actuator arrangement. In some arrangements, the valve might be arranged to open inwardly of the valve chamber 52 and away for the outlet 26.

Claims

I. A water pump for use downstream of a flow rate control valve of a mixed water delivery system, the pump having: an inlet for connection to a flow rate control valve; an outlet; a pump chamber connecting the inlet to the outlet and configured to pump water from the inlet to the outlet; and a bleed channel including a bleed valve for selectively connecting the outlet to the inlet in response to reduced water pressure at the inlet so as to reduce cavitation upstream of the pump chamber.
2. A water pump according to claim 1 wherein: the bleed valve provides an aperture of variable cross-section connecting the outlet to the inlet; and the pump is configured to vary the cross-section of the aperture provided by the bleed valve according to the water pressure at the inlet.
3. A water pump according to claim 1 or 2 further including: a bleed valve actuator for controlling the bleed valve.
4. A water pump according to claim 3 wherein the bleed valve actuator is responsive to a difference in water pressure at the inlet and atmospheric pressure outside the pump.
5. A water pump according to claim 4 wherein the bleed valve actuator includes a flexible diaphragm having an inner surface in communication with inlet water pressure and an outer surface in contact with atmospheric pressure.
6. A water pump according to claim 5 wherein: the diaphragm forms at least part of a wall of the bleed channel.
7. A water pump according to claim 5 or 6 wherein: the bleed channel extends between a valve aperture at the outlet and a connecting aperture at the inlet; the bleed valve includes a valve member resiliently biased in a position to close the bleed aperture; and the diaphragm, in response to a drop in pressure at the inlet, acts on the valve member so as to move the valve member in such a way as to open the bleed aperture.
8. A water pump according to claim 7 further including: a valve spring for biasing the diaphragm outwardly of the bleed channel wherein a drop in pressure at the inlet causes the diaphragm to move inwardly of the bleed channel against the bias of the valve spring so as to move the valve member into the outlet in such a way as to open the bleed aperture.
9. A water pump according to any preceding claim further including: a movable pump element within the pump chamber; a motor for moving the pump element within the pump chamber so as to pump water from the inlet to the outlet; and a motor controller configured to operate the motor at a constant speed.
10. A shower assembly including: a flow rate control valve having a hot water inlet, a cold water inlet and a control outlet; and a water pump according to any preceding claim wherein the inlet of the water pump is connected to the control outlet of the flow rate control valve.
11. A shower assembly according to claim 10 wherein the flow rate control valve includes a hot water valve defining a throughhole of variable cross-section to control the flow of hot water to the control outlet and an independently controllable cold water valve defining a throughhole of variable cross-section to control the flow of cold water to the control outlet.
12. A method of pumping water from downstream of a flow rate control valve using a valve with an inlet for connection to the flow rate control valve, an outlet and a pump chamber connecting the inlet to the outlet and configured to pump water from the inlet to the outlet, the method including: selectively bleeding water from the outlet to the inlet in response to reduced water pressure at the inlet so as to reduce cavitation upstream of the pump chamber.
13. A water pump constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.
14. A shower assembly constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.
15. A method of pumping water substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.