GB2205129A - Pump - Google Patents

Abstract

A water pump for pumping hot and cold water, eg. in showers, has a centrifugal pump (13, 14, 15) mounted at one end of a housing (12) of an electric motor (10) having a double ended drive shaft (11) and a regenerative-type pump (16, 17, 19, 20) mounted at the other end. Alternatively, both pumps may be located at one end of the drive shaft. The centrifugal pump is for pumping cold water, whilst the regenerative-type pump is for pumping hot water. The regenerative-type pump has front and back chambers and an impeller (19), the latter comprising a disk having blades on the front and back faces. A flow guide ring (20) serves to ensure that water in the back chamber is only affected by the blades on the back face of the impeller (19), whilst water in the front chamber is only affected by the blades on the front face of the impeller (19). <IMAGE>

Description

PUMP The present invention relates to pumps, particularly, though not exclusively, to water pumps.

When supplying water to appliances such as showers, it is often necessary for pumps to be provided if a domestic water supply is to be used. Appliances such as showers, which require a supply of hot and cold water often require bboth supplies to be provided with pumps. It has been previously proposed to provide a pump comprising a central electric pump motor which has a centrifugal pump attached to each end of the drive shaft thereof. One pump is connected to a cold water supply and the other pump to a hot water supply.

However, because the operation of a centrifugal pump causes regions of reduced pressure within the pump housing and because hot water is readily degassed, the hot water pump of the previously proposed design can suffer from problems in maintaining supply due to the formation of air-locks.

It is an object of the present invention to provide a pump which reduces the problem outlined above and avoids the formation of air-locks in a hot water supply.

In accordance with one aspect of the present invention, there is provided a pump comprising a pump motor having a drive shaft, said drive shaft operating a centrifugal pump and a regenerative-type pump.

Conveniently, the pump motor has a double ended drive shaft, one end of which operates the centrifugal pump and the other end of which operates the regenerative-type pump. In an alternative embodiment both pumps are located on one end of the drive shaft.

It is preferred that the pump is adapted for pumping liquids, particularly water.

It is particularly preferred that the centrifugal pump end is adapted for connection to a supply of cold water and the regenerative pump end is adapted for connection to a supply of hot water.

In accordance with another aspect of the present invention, there is provided a regenerative-type pump comprising an impeller rotably mounted within a pump body; said impeller comprising a generally circular disc having a plurality of radially extending blades projecting from either face thereof; said body being formed so as to define two chambers such that the blades on one side of the impeller rotate in one chamber only, the action of the impeller on the medium to be pumped in one chamber being unaffected by the action of the impeller in the other chamber.

Preferably, the two chambers have a common inlet and a common outlet.

In a preferred embodiment, the body includes a flow dividing ring located around the periphery of the impeller and serves to define said chambers. The chambers are typically shaped to guide flow from said inlet to said outlet.

The advantage of the present invention proved that the previously proposed design of two ended pump is that the use of the regenerative type pump for the hot water supply overcomes the problems caused by the formation of air-locks as the water is always maintained under pressure. However, the regenerative type pump is less efficient than an equivalent centrifugal pump so the centrifugal pump is maintained for the cold water supply which is not susceptible to the problems described above.

The present invention has the further advantage that for an electric motor driven pump, the centrifugal pump requires less current when the flow is restricted whereas the regenerative type pump requires correspondingly more current when flow is restricted.

This means that the current consumption remains approximately constant with flow changes.

The present invention will now be described by way of example with reference to the accompanying drawings which shows a pump according to one embodiment of the present invention with the two pump ends shown in exploded diagramatic form.

Referring now to the drawing, the pump shown therein comprises an electric motor (10) having opposite ends of a double ended drive shaft (11) projecting from the respective ends of the motor housing (12). Attached to one end of the housing (12), is a centrifugal pump comprising back and front sections (13), (14) which together define a pump housing having an involute formed therein. An impeller (16) is mounted on the end of the drive shaft and located within the pump housing.

A regenerative type pump mechanism is attached to the other end of the motor housing (12). The regenerative type pump comprises back and front sections (16), (17) defining a second pump housing.

Each section (16), (17) has a channel (18) formed therein. As can be seen from the drawing, each channel (28) comprises an arcuately curved channel portion (18a) extending around the axis of the drive shaft (11) for nearly 3600, and a radially extending channel portion (18b). The channel portions (18b) provide a passage for water to flow from the pump. An impeller (19) is mounted on the end of the drive shaft (11) which projects into the pump body. The impeller (19) comprises a circular disk having a plurality of radially extending blades projecting therefrom and arranged around the edge portion of the front and back faces of the disk, the blades on the back face being located between the blades on the front face.A flow guide ring (20) is located within the pump housing around the periphery of the impeller (19) so as to define, with the channel portions (18a), front and backchambers in the pump, communication between the chambers being provided by a gap in the flow guide ring (20). The provision of the flow guide ring (20) means that water in the back chamber is only affected by the blades on the back face of the impeller (19) and likewise water in the front chamber is only affected by the blades on the front face of the impeller (19). An inlet (21) is defined in the front section (17) to allow water into the pump housing. The inlet (21) opens at that end of the channel portions (18a) which is remote from the channel portions (18b) adjacent to the gap in the flow guide ring (20) so as to divide the inlet flow between the front and back chambers.

As will be appreciated from the drawing, the impeller (19) of the regenerative-type pump mechanism serves to urge the water circumferentially around the channel portions (18a) from the inlet (21) to the channel portions (18b) from which the water flows radially outwardly through outlet (22). As a result of the guide ring (20), the water is urged as parallel flow streams through the front and back chambers by the blades on the front and back faces, respectively, of the impeller (19) before merging to form a single stream again the radially extending channel portions (18b).

The provision of the regenerative-type pump mechanism, where generally circumferential flow of water takes place in the pumping chamber(s) as opposed to generally radial flow in the centrifugal pump, means that the water is maintained under pressure and so degassing does not occur easily from hot water.

Furthermore, should air bubbles form, or any air bubbles enter the pump from the hot water cylinder, the operation of the pump is not seriously affected. The flow guide ring (20) serves to guide the flow in each chamber of the regenerative-type pump so as to render the pumping action more efficient.

Although the use of a flow guide ring to define the front and back chambers, any other suitable means can of course be used.

Claims (9)

CLAIMS.

1. A pump comprising a pump motor having a drive shaft, said drive shaft operating a centrifugal pump and a regenerative-type pump.

2. A pump as claimed in Claim 1, wherein the pump motor has a double ended drive shaft, one end of which operates the centrifugal pump and the other end of which operates the regenerative-type pump.

3. A pump as claimed in Claim 1, wherein both pumps are located on one end of the drive shaft.

4. A pump as claimed in any preceding claim, wherein the centrifugal pump end is adapted for connection to a supply of cold water and the regenerative pump end is adapted for connection to a supply of hot water.

5. A regenerative-type pump comprising an impeller rotably mounted within a pump body; said impeller comprising a generally circular disc having a plurality of radially extending blades projecting from either face thereof; said body being formed so as to define two chambers such that the blades on one side of the impeller rotate in one chamber only, the action of the impeller on the medium to be pumped in one chamber being unaffected by the action of the impeller in the other chamber.

6. A pump as claimed in Claim 5, wherein the two chambers have a common inlet and a common outlet.

7. A pump as claimed in Claim 5 or 6, wherein the body includes a flow dividing ring located around the periphery of the impeller and serves to define said chambers.

8. A pump as claimed in Claim 1 or 5, substantially as hereinbefore described with reference to the accompanying drawing.

9. A pump as claimed in any one of Claims 1 to 4, wherein the regenerative-type pump is as claimed in any one of Claims 5 to 7.