This invention relates to the cooling of electronic circuits and more particularly but not solely to the cooling of electronic control circuits of pump motors for bathing pools and the like.

Bathing pools such as spa baths, hot tubs and swimming pools generally comprise a pump which is either on or off, or a dual speed pump having windings which can be switched to vary the pump speed between two values. However, it is desirable in bathing pools to provide at least one water jet which can be infinitely varied in speed. Generally this is achieved either by using valves which can be adjusted to divert water through a parallel flow path to the jet, or by creating a restriction fluid flow to the jet.

A disadvantage of the above-mentioned arrangements is that the pump is always running at full speed and consuming unnecessary energy. In fluid pumping applications frictional losses occur in the pipe work and a considerable amount of energy can be saved by using a variable speed drive in combination with a centrifugal pump. The reason for this is that the power consumed is directly proportional to the speed cubed. Hence a 20% reduction in speed saves approximately 50% energy costs and a 50% reduction in speed saves approximately 80% energy costs. The same applies for fans in heating and ventilating systems.

Variable speed drives or so-called VSDs typically comprise a controller which outputs a variable frequency pulse-width-modulated signal to the motor. These controllers comprise an inverter which initially converts AC power into DC power. The DC power is then converted into quasi-sinusoidal AC power using inverter switching circuit, the inverter switches being used to divide the quasi-sinusoidal output waveform into a series of narrow voltage pulses and to modulate the width of the pulses to vary the speed of the motor. All VSD inverters control speed by varying current frequency however the newer vector drives use current-switching techniques to control motor torque as well.

VSD inverters comprise solid state devices which dissipate heat and hence need to be mounted on heat sinks. A disadvantage of this is that such heat sinks can be bulky and sometimes fans are needed to create an airflow over the heat sink. VSD drives for controlling pump motors are even larger in size due to the fact that they have to comprise special housings to prevent the ingress of water and moisture.

We have now devised a bathing pool which alleviates the above-mentioned problems.

In accordance with the present invention, as seen from a first aspect, there is provided a pump arranged to circulate water through a pool of water, wherein the pump comprises a motor and a motor control circuit having one or more electronic components mounted on a member having a relatively high thermal conductivity in fluid contact with the water being pumped and arranged such that the thermal energy generated by the or each component heats the water.

In use, any thermal energy generated by the or each component is transferred to the member, which then transfers the thermal energy to the cooler water and hence away from the component(s). Since heat is only generated when water is being pumped, the water in contact with the member is moving and hence the heated water is transferred away from the member.

In this manner a smaller control unit can be used because the heat generated is dissipated into flowing water: typical VSD inverters are cooled by large heat sinks in contact with the air and sometimes fans are used. This problem is exacerbated in pump control units because a large sealed housing is required to prevent the ingress of water. In the present invention the member is cooled by the flowing water which has a much better thermal conductivity than air and hence the unit can be made much smaller.

Another advantage of the invention is that the heat dissipated into the water acts to heat the water and thereby significantly reduces heating costs or makes unheated pools inherently warmer.

Preferably the member comprises one or more comb or fin-like protrusions which extend radially into the water flow path. Preferably the or each protrusion lies in a plane which extends axially of the fluid flow. Alternatively, the or each protrusion may be arranged to create turbulence in the fluid flow and thereby improve heat transfer. Preferably the member is provided on a cooling device disposed remote from the pump, the cooling device having a fluid flow passage through which water is pumped by the pump.

An advantage of providing the member on a remote device which is separate to the pump is that it allows conventional pumps to be used without the need for modification. Also, the remote device can be mounted anywhere in the pipe work extending from the pump, for example so that heat can be delivered adjacent a point where water enters the pool.

Preferably the cooling device is mounted upstream of any heater so that the water in contact with the thermally conductive member is as cold as possible.

In one embodiment the member comprises a tubular body of said material having a relatively high thermal conductivity, the flow passage extending through the body. In use the or each electronic component can be directly mounted to an external surface of the body. The body may be lagged or encased in order to enhance heat transfer from the or each electronic component into the flowing liquid.

In an alternative embodiment the device comprises a body of plastics or other material having a relatively low thermal conductivity, the flow passage extending through the body, said member being mounted in an aperture formed in a side wall of the body such that the member is in contact with the fluid flow in the flow passage.

Preferably the said material having a relatively high thermal conductivity comprises aluminium, copper or a thermally conductive plastics compound.

Preferably the device comprises a coupling at opposite ends of the flow passage for respectively connecting to fluid inlet and outlet ducts.

Preferably the body is formed with a plurality of apertures for receiving respective thermally conductive members on which the said components are mounted. The apertures may be disposed at circumferentially spaced positions around the longitudinal flow axis of the passage or at longitudinally spaced positions along the longitudinal flow axis.

Preferably the control circuit comprises an inverter arranged to apply pulse-width modulated drive signals to the motor of the pump. Preferably the control circuit uses current-switching techniques to control motor torque as well.

Also in accordance with the present invention, as seen from a second aspect, there is provided a pump comprising a motor, a pumping device and cooling device mounted remote from said motor and pumping device, motor being controlled by control circuit having one or more electronic components mounted on the thermally conductive portion of said cooling device, the cooling device comprising a fluid inlet port and a fluid outlet port for respectively coupling to inlet and outlet pipes arranged to carry fluid pumped by said pumping device, said thermally conductive portion being arranged to contact fluid flowing along a flow path extending between said inlet and outlet ports.

Preferably said thermally conductive portion comprises one or more comb or fin-like protrusions which extend radially into the water flow path. Preferably the or each protrusion lie in a plane which extends axially of the fluid flow. Alternatively, the or each protrusion may be arranged to create turbulence in the fluid flow and thereby improve heat transfer.

Preferably said inlet and outlet ports comprise respective unions for sealingly engaging said pipes.

In one embodiment the device comprises a body of material having a high thermal conductivity, the flow passage extending through the body and the or each electronic component being directly mounted to an external surface of the body.

In an alternative embodiment the device comprises a body of plastics where the material having a relatively low thermal conductivity, the flow passage extending through the body, said thermally conductive portion comprising a member formed of a material having a high thermal conductivity which is mounted in an aperture formed in a side wall of the body such that the member is in contact with the fluid flow in the flow passage.

Preferably thermally conductive material comprises aluminium, copper or a thermally conductive compound material, for example comprising a plastics material.

Preferably the control circuit comprises an inverter arranged to apply pulse-width modulated drive signals to the motor of the pump. Preferably the control circuit uses current-switching techniques to control motor torque as well.

Also in accordance with the present invention, as seen from a third aspect, there is provided a device for creating a flow of fluid along a duct, the device comprising an impeller, a motor for rotating the impeller and a motor control circuit having one or more electronic components mounted on a member having a relatively high thermal conductivity, said member having one or more protrusions extending into the duct.

Preferably the or each protrusion is comb or fin-like. Preferably the or each protrusion lies in a plane which extends axially of the fluid flow. Alternatively, the or each protrusion may be arranged to create turbulence in the fluid flow and thereby improve heat transfer.

The device may be a fan for creating a flow of gas along the duct. Alternatively, the device may be a pump for creating a flow of liquid along the duct.

Preferably the member is provided on a cooling device disposed remote from the device and the motor, the cooling device having a fluid flow passage along which fluid is driven by the device.

Also, in accordance with the present invention, as seen from a fourth aspect, there is provided a bathing pool comprising a pump arranged to circulate water through a pool of water, wherein the pump comprises a motor and a motor control circuit having one or more electronic components mounted on a member having a relatively high thermal conductivity in fluid contact with the water being pumped. Embodiments of the present invention will now be described by a way of examples only and with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of an embodiment of a bathing pool in accordance with the present invention;

Figure 2 is an exploded perspective view of a cooling device of an alternative embodiment of bathing pool in accordance with the present invention;

Figure 3 is a perspective view of the cooling device of Figure 2;

Figure 4 is a perspective view of a partially assembled cooling device of a second embodiment of bathing pool in accordance with the present invention; and

Figure 5 is an end view of the cooling device of Figure 4.

Referring to Figure 1 of the drawings, there is shown a bathing pool comprising a walled pool structure BP which contains a body of water W in which persons can bathe and/or swim.

The pump P is arranged to circulate the water W via inlet and outlet pipes D1 , D2 which are connected to the walled pool structure BP at spaced apart locations. The outlet pipe D2 may direct water into the walled pool structure BP via a water jet (not shown). A filter and/or heater (not shown) are preferably connected in series with the pump P.

A pump P comprises an impeller which is driven by a motor M. The motor M is controlled by a control circuit 22 provided on the cooling device 10 which is connected in series with the outlet pipe D2 extending from the pump P. The cooling device 10 comprises a hollow tubular body 11 formed of aluminium, copper or another material having a relatively high thermal conductivity. The control circuit 22 comprises a plurality of electronic components including one or more solid state switches 27 which are mounted in face-to-face contact with a flattened region of the external surface of the body 1 1 of the cooling device 10. A thermally conductive compound may be disposed between the solid state switches 27 and the surface of the body 10 in order to improve the thermal conductivity therebetween. A cover 30 extends over the control circuit 22 in order to sealingly contain the latter.

The control circuit 22 is arranged to apply control signals to the motor in order to vary the speed of the latter. A switch S or other manually-operable control device is connected to the control circuit 22 so that the user may select the desired speed of the pump P. Alternatively or additionally, the speed of the pump P may be controlled by a microprocessor or other program device.

In use, water is drawn along the inlet pipe D1 through the pump P into the outlet pipe D2. The water flowing in the outlet pipe D2 flows into an elongate flow passage 13 extending through the cooling device 10, such that the water acts to cool the body 1 1 of the cooling device 10. The heat generated by the solid state switches 27 is transferred to the body 1 1 of the cooling device 10, which is maintained at a low temperature by the water W. If necessary, one or more cooling fins may extend into the flow passage 13 in order to increase the surface area of the body 11 which is in contact with the water W. The heat generated by the solid switching device 27 is transferred by the water W away from the cooling device 10 into the walled pool structure BP, where it serves to increase the ambient temperature of the water W.

Referring to Figure 2 of the drawings, there is shown a cooling device 10 of a second embodiment of bathing pool in accordance with the present invention and like parts are given like reference numerals. In this embodiment, the cooling device 10 comprises a tubular body 1 1 formed of plastics or other material having a relatively low thermal conductivity.

An enlarged aperture 14 is formed in the side wall of the tubular body portion 1 1 for receiving a thermally conductive cooling member 15 formed of aluminium, copper or another material having relatively high thermal conductivity. The member 15 comprises an upper plate portion 20 having a flat outer surface and a plurality of fins 21 extending from the lower surface of the plate 20. The fins 21 extend parallel to each other and are arranged such that they lie in line with the longitudinal axis of the flow passage 13. An elastomeric seal 16 is disposed between the member 15 and the body portion 11 in order to form a water tight seal therebetween. The opposite ends of the body 11 are provided with externally screw-threaded portions 12 for respectively engaging internally screw-threaded locking rings 17. The locking rings 17 captively retain respective compression rings 18 which are urged against the respective end faces of the body 1 1 when the locking ring 17 is tightened. O-rings 19 are disposed between the rings 18 and the respective end faces of the body 11.

In use, the device 10 is connected in series with the pump P via respective sections of outlet pipe D2, the ends of the outlet pipe D2 being sealed to the body 11 by means of the locking rings 17 and compression rings 18. The solid state switches 27 of a control circuit are mounted to the flat outer face of the member 15 in a similar manner to the embodiment of Figure 1.

Referring to Figure 3 of the drawings, the electronic control circuit is sealingly contained inside an enclosure 30 which is fitted to the body 1 1 of the device 10.

Referring to Figures 4 and 5 of the drawings, in an alternative embodiment, the body 1 1 of device 10 is provided with a pair of apertures 14 which are disposed diametrically opposite each other on the side wall of the body 11. A pair of thermally conductive members 15 are mounted in the respective apertures. In this embodiment, the control circuit 22 is divided into two portions having respective solid state switches 27 mounted in thermal contact with the members 15. Other components 25 may be mounted on the same printed circuit board 23 which carries the solid state switches 27. A second printed circuit board 24 may be mounted parallel to the first printed circuit board 23 for carrying additional electronic components 26. The larger electronic components 25 are preferably positioned on the first printed circuit board 23 such that they extend alongside the body 1 1 of the device 10, thereby conserving space.

In an alternative embodiment the members 15 may cool the solid state switching devices of control circuits for controlling respective motors. A C-shaped or O-shaped housing may extend around the device to enclose both control circuits or just one control circuit together with the control electronics of other apparatus, such as the control circuit of a spa bath. Thus, heat generated by the control electronics of other apparatus is also dissipated into the flowing fluid. The cooling device may be formed integrally with a heater, the heater being disposed downstream of the thermally conductive member of the cooling device.

Whilst the embodiments shown are arranged to cool the control circuit of a pump the same arrangement could be used to cool the control circuit of a fan. The cooling device could be connected directly or indirectly to the inlet of the fan and the high airflow through the protrusions would cool the electronics extremely well.

A pump in accordance with a preferred aspect of the present invention is arranged to circulate water through a pool of water. The pump comprises a motor and a motor control circuit having one or more electronic components mounted on a heat sink disposed in flow contact with the water. In use, the thermal energy generated by the control circuit is quickly dissipated by the flowing water, thereby allowing a less expensive control circuit to be used which has a lower power rating. The dissipated energy advantageously also serves to heat the pool water, thereby reducing the amount of energy used by any separate heating device or heating an otherwise unheated pool.