IE59262B1

IE59262B1 - Valve

Info

Publication number: IE59262B1
Application number: IE316486A
Authority: IE
Original assignee: Caradon Mira Ltd
Priority date: 1985-12-10
Filing date: 1986-12-02
Publication date: 1994-01-26
Also published as: GB2183789A; GB8530351D0; GB2183789B; IE863164L

Abstract

A fluid flow control valve 2, preferably for an instantaneous water heater to reduce risk of scalding, has a closure member 35 coupled with a flow regulator 38 positioned downstream of an inlet port 21 to control the flow rate from an inlet chamber 22 to an outlet 46a. The flow regulator 38 is constructed to provide a gradual reduction in the flow rate, from a maximum obtained on rotating in one sense a control knob mounted on the spindle 25 to open the inlet port 21, by further rotation of the control knob in the same sense. The closure member 35 and flow regulator 38 are preferably carried by a piston 30 connected to a spindle 25 through interengaging screw threads 28,29 for converting rotational movement of the spindle 25 into sliding movement of the piston 30 for moving the closure member 35 to open and close the inlet port 21 and simultaneously moving the flow regulator 38 to adjust the flow rate.

Description

This invention concerns valves for controlling fluid flow and water heaters incorporating such valves, » in particular so called instantaneous water heaters. * Instantaneous water heaters provide a source of k hot water on demand by heating a supply of cold water flowing continuously through the heater and are commonly provided in ablutionary installations, especially for showering.

Generally, the known instantaneous water heaters Ιθ include a heat exchanger to heat rapidly the water and a valve to control the flow rate through the heat exchanger and hence the final water temperature.

It is important in heaters of this type that the heat exchanger should be turned off when there is less 15 than a predetermined minimum flow rate through the heat exchanger corresponding to a safe maximum water temperature so as to prevent'water temperatures higherthan the safe maximum or even'boiling of the water being obtained.

For this purpose it is already known in instantaneous electric water heaters to control the power supply to a heating element of considerable heating capacity, generally about 7kW, by means of a switch assembly responsive to the water pressure in the heat exchanger downstream of the valve.

A disadvantage of such known arrangement is that the water pressure in the heat exchanger is relatively low as compared with the supply pressure and varies with the selected flow rate leading to unreliable φ operation of the switch assembly. For example, it is possible for the switch assembly to cut off the power · » -3to the heating element when selecting low flow rates to obtain high water temperatures.

To overcome this disadvantage it is known to arrange for the switch assembly to be responsive to the water pressure in the valve between a closure member operable to turn the water flow on and off and a flow regulator downstream of and operable independently of the closure member to adjust the flow rate to obtain the desired water temperature. With this arrangement, when the water flow is turned on, the water pressure controlling the switch assembly is substantially the water supply pressure. The supply pressure is considerably higher than the water pressure downstream of the valve in the heat exchanger and is substantially unaffected by variations in the water. pressure downstream of the flow regulator in the heat exchanger as above-described leading to reliable operation of the switch assembly.

A disadvantage of this arrangement however, is that the closure member can be operated to turn the water flow off with the flow regulator adjusted to provide the minimum flow rate and, if the closure member is operated to turn the water flow on with the flow regulator in this position of adjustment, the maximum water temperature is obtained. There is a significant risk of the user being scalded by such operation and this risk is further increased if the water flow is only turned off for a short period before being turned on again. In these circumstances, 30 the residual heat in the heating element on turning * the water flow' off heats the water remaining in the * heat exchanger and, on turning the water flow on again, this heated water is further heated so that a -4water temperature higher than the maximum water temperature is obtained initially.

It is an object of the present invention to provide a valve and a water heater incorporating the valve which overcome the problems and disadvantages afore-mentioned.

According to a first aspect of the present invention we provide a valve having an inlet for connection to a supply of fluid and an outlet for connection to a fluid heater, the inlet being in fluid communication with an inlet chamber through an inlet port, a closure member operatively connected to a control knob and movable on rotation of the control knob in opposed senses to open and close the inlet port to turn the fluid flow on and off respectively, a flow regulator coupled to the closure member for movement therewith on rotation of the control knob to control the flow rate from the inlet chamber to the outlet, the arrangement being such that, in use, said flow rate is gradually reduced from a maximum flow rate obtained on rotation of the control knob in one sense to open the inlet port by further rotation of the control knob in said one sense, and a switch assembly responsive to the fluid pressure in the inlet chamber for controlling the .25 fluid heater.

In the valve, according to the first aspect of this invention, rotation of. the control knob in the direction to move the closure member to open the inlet port also moves the flow regulator to reduce the flow rate. In this way rotation of the control knob in the opposed direction to move the closure member to close the inlet port also moves the flow regulator to increase the flow rate thereby ensuring that the flow regulator is automatically set to provide the maximum flow rate when the inlet port is opened. -5Preferably the flow regulator is adapted to maintain the flow rate substantially constant for a given setting of the control knob. In this way, when the valve is used to control the flow rate in an instantaneous water heater, the selected water temperature is -not affected by fluctuations in the water supply pressure.

In a preferred embodiment, the flow regulator comprises a core member having a plurality of circumferentially spaced apart longitudinally extending grooves arranged to define with a ring member a plurality of openings for flow of fluid from the inlet chamber to the outlet, the core member being movable relative to the ring member on rotation of the control knob to vary the size of the openings for adjusting the flow rate.

The grooves are conveniently of increasing crosssection, for example tapered to be of increasing depth and/or width, in the longitudinal direction leading away from the inlet port. In this way, the size of openings is reduced on rotation of the control knob to open the inlet port to provide the desired reduction in the flow rate.

Advantageously, the ring member is carried by a spindle mounted for rotation by the control knob and the core member and closure member are carried by a piston coupled to the spindle for longitudinal movement relative to the spindle on rotation of the spindle by the control knob both to move the core member relative to the ring member and to move the closure member relative to the inlet port.

Preferably, the spindle is mounted for rotational movement and is retained against longitudinal movement, and the piston is mounted for longitudinal movement and is retained against rotational movement. For example, the piston may be arranged for sliding movement in the inlet chamber with confronting surfaces of the piston and inlet chamber co-operating to prevent rotation of the piston. Thus, the confronting surfaces may have complementary axial splines or he of complementary noncircular cross-section.

Conveniently, the spindle and piston are coupled 10 by threadably engaged portions such that the piston is displaced longitudinally relative to the spindle on rotation of the spindle.

. The piston is preferably hollow for passage of fluid admitted to the inlet chamber and the spindle preferably has a bore for passage of the admitted fluid to the outlet.

Conveniently, the ring member is located and retained in the spindle bore, and the core member and closure member are mounted at opposed ends of the piston for co-operating with the'·'ring member and a valve seat defining the inlet port respectively.

Preferably, the spindle is mounted in a closure cap and the spindle and cap are provided with radial . ports for passage of fluid from the bore to the outlet.

Advantageously, the spindle includes a stop to limit movement of the core member to define the minimum flow rate, and the stop is conveniently adjustable to allow the minimum flow rate to be selected to suit any given application.

Advantageously, the switch assembly is responsive to the fluid pressure in the inlet chamber for controlling a heat exchanger of the fluid heater. This fluid pressure is zero when the closure member engages -7the valve seat to close the inlet port and is substantially the fluid supply pressure when the closure member is clear of the valve seat to open the inlet port. This pressure is substantially constant for all operating conditions and the switch assembly is conveniently arranged to operate at an intermediate fluid pressure. This intermediate pressure is selected to be as low as possible and corresponds to that required to provide the minimum flow rate for safe operation of the heater. A large pressure difference therefore exists between the operating pressure for the switch assembly and the actual pressure in the inlet chamber when the inlet port is open. As a result, minor fluctuations in the supply pressure do not affect operation of the switch assembly and the heat exchanger controlled by the switch assembly is only switched off if there is a large reduction in the fluid pressure in the inlet chamber, for example if the supply pressure drops below the minimum or on closing the inlet port.

In this way reliable operation' of the switch assembly is ensured under all conditions of use.

Preferably, the switch assembly includes an actuator responsive to the fluid pressure for controlling a heating element of the heat exchanger.

Conveniently, the actuator is resiliently biassed, for example by a return spring, towards a diaphragm . , arranged to sense the fluid pressure in the inlet chamber, and the resilient biassing is selected to be overcome by the operating pressure for the switch assembly. By this arrangement, the diaphragm deflects to move the actuator to turn the heat exchanger on when the pressure in the chamber is equal to or greater than the operating pressure and, the actuator and diaphragm -8are automatically returned to their original positions to tum the heat exchanger off under the biassing of the return spring when the fluid pressure in the chamber is less than the operating pressure. In this way, accurate response of the switch assembly to change in the fluid pressure in the chamber is obtained and the heat exchanger is only turned on when the minimum flow rate for safe operation of the heater is present.

Preferably, the switch assembly includes a switch . 10 controlled by the actuator for controlling the power supply to the heating element.’ Conveniently, the switch is operable by a lever pivotal under the control of the actuator, and the switch assembly includes a cam to block selectively the pivotal movement of the lever. By this arrangement, the heater may be operated with or without the power input to the heating element as desired.

Advantageously, the switch assembly has a pair of switches for controlling respective electric heating elements, a pair of levers each pivotal under the control of the actuator to operate a respective switch for each heating element, and a pair of cams, one for each lever, to block selectively the pivotal movement of the associated lever. By this arrangement, both, one or neither switch may be operated to alter the power input to the heating elements as desired.

Conveniently, the actuator comprises a push rod resiliently biassed towards the diaphragm by the return spring and a beam extending transversely through an elongate diametric slot intermediate the ends of the push rod. Each lever engages a respective one end of the beam and the beam is resiliently biassed, for example by a relief spring, to the outer end of the -9slot. In this way the relief spring permits deflection of the diaphragm to move the push rod when pivotal movement of one or both levers is blocked.

Preferably, the cam or each cam is mounted on a spindle for rotation therewith by a control knob to select-the required power input.

Advantageously, the inlet and outlet are provided by a one piece valve body and the outlet is conveniently adapted for connection to the heat exchanger.

According to a second aspect of the invention, we provide a water heater having a valve according to the first aspect of the invention and a heat exchanger controlled by the switch assembly.

In the water heater according to the second aspect of this invention, the maximum flow rate and hence the coolest water temperature is always obtained on initial rotation of the control knob to open the inlet port and higher water temperatures are obtained by further rotation of the control knob to'.reduce the flow rate.

In this way, the risk of the user being scalded is reduced.

Furthermore, the heat exchanger is flushed with the coolest water on rotation of the control knob to close the inlet port thereby reducing the risk of the user being scalded by water remaining the heat exchanger being heated to an elevated temperature if only a short period of time elapses between the heater being turned off and turned on.

Preferably, the heat exchanger is connected to the outlet from the valve and includes a plurality of electric heating elements controlled by the switch assembly. -10Advantageously, the switch assembly includes a separate switch for each heating element, the switches being operable by a common actuator responsive to the water pressure in the inlet chamber, and manually operable cam means for selectively controlling actuation of the switches for controlling the power input to the heat exchanger.

Preferably, the heat exchanger includes a thermal cut-out and a pressure relief valve.

According to a third aspect of the invention, we provide a control valve for a water heater, the control valve comprising a one piece valve body with a water inlet and a water outlet, and the control valve further comprising the following components :15 a. an on/off water flow control valve; b. a flow control valve for controlling the rate of water flow; and c. a switch assembly for controlling an associate water heater; wherein the on/off water flow control valve comprises a closure member for opening and closing an inlet port opening to an inlet chamber, the water flow rate control valve comprises a flow regulator for controlling the water flow rate from the inlet chamber . to the outlet for delivery to the associate water heater, and the on/off closure member and flow regulator are coupled and operatively connected to a common control knob to provide a maximum said flow rate on rotation of the control knob in a direction to open the inlet port and thereafter reduce said flow rate by further rotation in the same direction. -11According to a fourth aspect of the invention, we provide an instantaneous electric water heater incorporating a control valve according to the third aspect of the invention.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings wherein:FIGURE 1 is a front view of a water heater according to the second and fourth aspects of the invention incorporating a valve according to the first and third aspects of the invention; FIGURE 2 is a side view of the water heater shown in Figure 1; FIGURE 3 is a front view of the water heater shown in Figures 1 and 2 with the.front cover of the casing removed to show the internal parts; FIGURE 4 is a section through the valve shown in Figure 3; FIGURE 5 is a section on the line X-X of Figure 3; FIGURE 6 is a front view, to an enlarged scale, of the switch assembly shown in Figure 3; FIGURE 7 is a rear view of the switch assembly shown in Figure 6; and FIGURE 8 is a side view, partly in section, of the switch assembly shown in Figures 6 and 7.

Referring first to Figures 1 to 3 of the accompanying drawings, there is shown an instantaneous electric water heater having a generally rectangular casing 1 housing a valve 2, a heat exchanger 3 and a switch assembly 4. -12The casing 1 has a base plate 5 and a front cover 6 on which are arranged two rotatable control knobs 7,8. The front cover 6 is mounted on the base plate 5 and held in position by a screw 9 to permit removal of the front cover 6 from the base plate 5.

The base plate 5 is formed with a number of holes 10 by means of which the casing 1 is surface mounted, for example on a wall, by any suitable fasteners, such as screws 11. The base plate 5 also has a number of ducts (not shown) to permit top, bottom, side or rear entry of a cold water supply for connection to an inlet 12 to the valve 2 and an electrical supply for connection to one side of a terminal block 13 within the casing.

The control knob 7 selects the power input to the heat exchanger 3 and, as shown in Figure 1, has three angularly spaced apart settings A,B and C corresponding to a power input of 0kW,4kW and 7.2kW respectively.

The control knob 8 operates the valve 2 to turn the water flow on and off and to adjust the flow rate through the heat exchanger 3 and hence the final temperature of the water for the selected power input.

The heat exchanger 3 comprises a hollow body 14 having an inlet 15 connected to the valve 2 and an outlet 16 extending through the bottom of the cover 6 for connection to an ablutionary appliance, for example a shower (not shown). Arranged within the body 14 are two sheathed heating elements (not shown) coiled concentric with one another and connected through the switch assembly 4 to the other side of the terminal block 13. -13The switch assembly 4 controls the power to the heating elements and is set by the control knob 7 to provide automatically the selected power input in response to the water pressure in the valve 2. The heat exchanger 3 further includes a thermal cut-out 17 to prevent overheating of the heating elements and a safety valve 18 to release automatically an excessive pressure build-up in the body 14. The safety valve 18 is the subject of our granted U.K. Patent No.2,167,842 ' to which the reader is directed for further details of the construction and operation.’ Referring now to Figure 4, the valve 2 comprises a tubular one-piece body 19 having a lateral passage 20 leading from the inlet 12 to an inlet port 21 opening to an inlet chamber 22. The inlet port 21 is defined by an annular valve seat 23 arranged centrally on the longitudinal axis at one end of the body 19. The other end of the body 19 is closed by a cap 24 in which a spindle 25 is mounted and retained by a circlip 26 permitting rotation of the spindle 25 about the longitudinal axis of the body 19 but preventing movement of the spindle 25 longitudinally of the body 19.

The outer end of the spindle 25 is formed with axial splines 27 for engagement with complementary axial splines (not shown) on the control knob 8 to lock . . the spindle 25 for rotation with the knob _8 whilst permitting the knob 8 to be slid off the spindle 25, for example when removing the front cover 6.

The inner end of the spindle 25 is formed with a screw thread 28 on the outer surface engageable with a -14c complement ary screw thread 29 formed on the inner surface of a hollow piston 30. The outer surface of the piston 30 is of hexagonal shape in cross-section and the confronting inner surface of the body 19 is of complementary hexagonal shape in cross-section to prevent rotation of the piston 30 in the body 19 whilst permitting sliding movement of the piston 30 longitudinally of the body 19 on rotation of the spindle 25.

The end of the piston 30 remote from the spindle 25 is formed with a web 31 having a central through bore 32 and a plurality of circumferentially spaced’ apart holes 33. An elongate rod 34 extends through the bore 32 and is secured in fluid-tight manner by any suitable means, for example ultrasonic welding.

A closure member comprising a resilient annular washer 35 is mounted on one end of the rod 34 facing the valve seat 23. The washer 35 is seated in a recessed portion of the web 31 and is releasably secured by a nut 36 engaging a threaded end portion of the rod 34. The washer 35 engages the valve seat 23 to close the inlet port 21 in one extreme position of the piston 30 as shown in Figure 4 and disengages the valve seat 23 to open the inlet port 21 on clockwise rotation of the control knob 8 to slide the piston 30 to the left, as viewed in Figure 4, away from the valve seat 23 enabling water to enter the. inlet chamber 22 and flow through the holes 33 to the interior of the piston 30.

The inner end of the spindle 25 is formed with a central bore 37 in which is received a flow regulator 38 * mounted on the other end of the rod 34. -15The flow regulator comprises a substantially cylindrical core member 38 extending longitudinally of the body 19 and having a plurality of longitudinally extending circumferentially spaced apart grooves (not •5 shown) formed in the outer surface. An O-ring 39 located and retained against a shoulder 40 in the spindle bore 37 by a ring 41 engages the outer surface of the core member 38 to define with the grooves a plurality of circumferentially spaced apart openings (not shown) enabling water to flow from the interior of the piston 30 to the spindle bore 37 downstream of the core member 38.

The grooves are tapered to be of increasing depth and/or width in a direction away from the valve seat 23 so that the size of the openings decreases on clockwise rotation of the control knob 8 to slide the piston 30 to the left, as viewed in Figure 4, away from the valve seat 23. In this way, the maximum flow rate is obtained on initial clockwise rotation of the control knob 8 to open the inlet port 21 and thereafter further clockwise rotation of the control knob 8 gradually reduces the flow rate. The minimum flow rate is set by a stop comprising an adjustable set screw 42 mounted in the outer end of the spindle 25 and extending into the bore 37 for engagement with the end of the rod 34 to limit sliding movement of the piston 30 to the left, as viewed in Figure 4. The set screw 42 is adjusted on installation to set the minimum flow rate to obtain a safe maximum water temperature when using the highest power input available.

The water pressure in the inlet chamber 22 is substantially the same as the water supply pressure -16when the washer 35 is moved clear of the valve seat 23 by clockwise rotation of the control knob 8 to open the inlet port 21. Variations in the supply pressure are automatically accommodated by movement of the O-ring 39 .5 into or out of the grooves thereby adjusting the size of the openings to maintain the flow rate substantially constant for any given position of the core member 38.

Downstream of the flow regulator, the spindle 25 is formed with a plurality of .radial ports 43 leading from the bore 37. The cap 24 is also formed with a plurality of radial ports 44 and defines with the spindle 25 an annular channel 45 providing a flow path between the spindle ports 43 and cap ports 44 for all rotational positions of the spindle 25. The cap ports 44 open into a part circumferential outlet chamber (not shown) formed in the body 19 which opens into an axial passage 46 leading to an outlet 46a from the valve 2 having an external flange for connection to the heat exchanger inlet 15.

To render the valve 2 fluid-tight, the cap 24 is sealed in the body by a pair of longitudinally spaced apart O-rings 47,48 positioned between confronting surfaces of the cap 24 and body 19 on opposite sides of the cap ports 44. Likewise the spindle 25 is sealed in the cap 24 by a pair of longitudinally spaced apart Orings 49,50 positioned between confronting surfaces of the cap 24 and spindle 25 on opposite sides of the spindle ports 43.

Referring now to Figures 5 to 8, the switch assembly 4 includes a pair of bellcrank levers 51,52 pivotal under the control of an actuator 53 responsive to the water pressure in the inlet chamber 22 to -1710 operate respective microswitches 54,55 for each heating element and a pair of cams 56,57 mounted on a spindle 58 for rotation by the control knob 7 to block selectively the pivotal movement of both, one or neither lever 51,52 to provide the selected power input to the heating elements.

The spindle 58 is formed with axial splines 59 for engagement with complementary axial splines (not shown) on the control knob 7 to lock the spindle 58 for rotation with the knob 7 whilst permitting the knob 7 to be slid off the spindle 58, for example when removing the front cover 6. The cam 56 is formed with a plurality of recesses 60 in the marginal edge for selective engagement by a resilient abutment 61 to hold the spindle 58 and cams 56,57 at any selected one of positions A,B and C of the control knob 7.

The marginal edge of a flexible diaphragm 62 is clamped between co-operating flanges 63,64 of the valve body 19 and a mounting plate 65 for the actuator 53 to define a fluid chamber 66 on the outside of the valve body 19. The chamber 66 communicates with the inlet chamber 22 through an orifice 67 in the wall of the valve body 19 and a longitudinally extending groove 68 formed in the inner surface of the valve body 19 so that the water pressure in the chamber 66 is substantially the same as the water pressure in the inlet chamber 22.

The actuator 53 comprises a push rod 69 arranged for sliding movement in·an opening in the mounting plate 65 and a beam 70 positioned on the outside of the mounting plate 65 and extending transversely through an elongate diametric slot 71 intermediate the ends of the push rod 69. -18The inner end of the push rod 69 has a diaphragm plate 72 seated on the diaphragm 62 and a return spring 73 encircling the push rod 69 acts between the mounting plate 65 and the diaphragm plate 72 to bias '5 the actuator 53 towards the diaphragm 62 for movement therewith in response to the water pressure in the chamber 66.

Each bellcrank lever 51,52 engages a respective one end of the beam 70 and a relief spring 74 received within the push rod 69 acts between the beam 70 and diaphragm plate 72 to bias the beam 70 to the outer end of the slot 71.

When the bias of return spring 73 exceeds the water pressure in the chamber 66, the actuator 53 and diaphragm 62 adopt the position shown in Figures 6,7 and 8. In this position both microswitches 54,55 are open and there is no power input to the heating elements.

When the water pressure in the chamber 66 overcomes the resilient biassing of return spring 73, the diaphragm 62 deflects and moves the push rod 69 outwards of the mounting plate 65 to provide the power input to the heating elements selected by the control knob 7 as now explained. position A, the cams 56,57 block pivotal movement of both levers 51,52. The beam 70 is thus held stationary by the levers 51,52 compressing the relief spring 74 on outward movement of the push rod 69 so that neither microswitch 54,55 is closed and the power input is OkW.

In position B, the cam 57 blocks pivotal movement of lever 52 while cam 56 permits pivotal movement of lever 51. One end of the beam is thus held stationary -19by the lever 52 causing the beam 70 to tilt in the slot 71 under the bias of relief spring 74 on outward movement of the push rod 69 and pivot lever 51 to close the associated microswitch 54 and the power input is 4.0kW.

In position C, the cams 56,57 permit pivotal movement of both levers 51,52. The beam 70 is thus free to move with the push rod 69 under the bias of relief spring 74 on outward movement of the push rod 69 and pivots each lever 51,52 to close the associated microswitch 54,55 and the power input is 7.2kW.

The bias of return spring 73 is selected to be overcome by a water pressure corresponding to the minimum water pressure required to provide the predetermined minimum flow rate for safe operation of the heater. This water pressure is low as compared with the water supply pressure and in this way it is ensured that the selected power input to the heating elements is only provided when.there is sufficient water flow through the heater and is substantially unaffected by minor variations in the water..supply pressure for all conditions of use.

As will be appreciated from the foregoing description, by utilising a valve in which the closure member and flow regulator are coupled for operation by a common control knob to provide the maximum flow rate on rotation of the control knob to open the inlet port and thereafter a gradual reduction in flow rate on further rotation of the control knob in the same direction, it is ensured that the coolest water temperature is always obtained on initial rotation of the control knob for any selected power input. -20Additionally, on rotation of the control knob to close the inlet port, the flow rate increases to the maximum before the inlet port is closed so that the heater is flushed with the coolest water temperature.

In this way, the risk of the user being scalded is considerably reduced, especially when the heater is only turned off for a short period of time before reuse.

It will be understood that the invention is not 10 limited to the embodiment above-described and that the valve has application to all types and constructions of instantaneous electric water heaters as well as instantaneous water heaters in which the heat exchanger is adapted to heat the water by fuel-fired heating devices. For example, the electric heating elements of the heat exchanger above-described may be replaced by at least one gas burner and the switch assembly modified to operate a respective gas valve for controlling the supply of gas to the or each burner in response to the water pressure .in the inlet chamber.

Claims

Claims:

1. A valve having an inlet for connection to a supply of fluid and an outlet for connection to a fluid heater, the inlet being in fluid communication with an 5 inlet chamber through an inlet port, a closure member operatively connected to a control knob and movable on rotation of the control knob in opposed senses to open and close the inlet port to turn the fluid flow on and off respectively, a flow regulator coupled to the 10 closure member for movement therewith on rotation of the control knob to control the flow rate from the inlet chamber to the outlet, the arrangement being such that, in use, said flow rate is gradually reduced from a maximum flow rate obtained on rotation of the control 15 knob in one sense to open the inlet port by further rotation of the control knob in said one sense, and a switch assembly responsive to the fluid pressure in the inlet chamber for controlling the fluid heater.

2. A valve according to Claim 1 wherein the flow 20 regulator is adapted to maintain the flow rate substantially constant for a given setting of the control knob.

3. A valve according to Claim 2 wherein the flow regulator comprises a core member having a plurality of .25 circumferentially spaced apart longitudinally extending grooves arranged to define with a ring member a plurality of openings for flow of fluid frcm the inlet chamber to the outlet, the core member being movable relative to the ring member on rotation of the control 30. knob to vary the size of the openings for adjusting the flow rate. -224. A valve according to Claim 3 wherein the grooves are tapered to be of increasing depth and/or width in the longitudinal direction leading away from the inlet port. t 5 5. A valve according to Claim 3 or Claim

4. Wherein the ring member is carried by a spindle mounted for rotation by the control knob and the core member and closure member are carried by a piston coupled to the spindle for longitudinal movement relative to the 10 spindle on rotation of the spindle by the control knob both to move the core member relative to the ring member and to move the closure member relative to the inlet port. 6. A valve according to Claim 5 wherein the spindle 15 is mounted for rotational movement and is retained against longitudinal movement, and the piston is mounted for longitudinal movement and is retained against rotational movement. 7. A valve according to Claim 6 wherein the spindle 20 and piston have threadably engaged portions such that the piston is displaced longitudinally relative to the spindle on rotation of the spindle. 8. A valve according to any one of Claims 5 to 7 wherein the piston is hollow for passage of fluid .25 admitted to the inlet chamber and the spindle has a bore for passage of the admitted fluid to the outlet. 9. A valve according to Claim 8.wherein the ring member is located and retained in the spindle bore, and the core member and closure member are mounted at 30 opposed ends of the piston. 10. A valve according to Claim 8 or Claim 9 wherein the spindle is mounted in a closure cap and the spindle and cap are provided with radial ports for passage of fluid from the bore to the outlet. -2311. A valve according to any one of Claims 5 to 10 wherein the spindle includes a stop to limit movement of the core member to define the minimum flow rate. 12. A valve according to Claim 11 wherein the stop is 5 adjustable. 13. A valve according to any one of the preceding Claims wherein the switch assembly is responsive to the fluid pressure in the inlet chamber for controlling a heat exchanger of the fluid heater. 10 14. A valve according to Claim 13 wherein the switch assembly is adapted for response to a fluid pressure lower than the pressure of the fluid supply. 15. A valve according to Claim 13 or Claim 14 wherein the switch assembly includes an actuator responsive to 15 the fluid pressure for controlling a heating element of the heat exchanger. 16. A valve according to Claim 15 wherein the actuator is resiliently biassed towards a diaphragm arranged to sense the fluid pressure in the inlet chamber, and the .20 resilient biassing is selected'to be overcome by the operating pressure for the switch assembly. 17. A valve according to Claim 15 or Claim 16 wherein the switch assembly includes a switch controlled by the actuator for controlling the power supply to the 25 . heating element. 18. A valve according to Claim 17 wherein the switch is operable by a lever pivotal under the control of the actuator, and the switch assembly includes a cam to block selectively the pivotal movement of the lever. 30 19. A valve according to Claim 18 wherein the switch assembly has a pair of switches for .controlling respective heating elements, a pair of levers each pivotal under the control of the actuator to operate a -24respective switch for each heating element and a pair of cams, one for each lever, to block selectively the pivotal movement of the associated lever. 20. A valve according to Claim 19 wherein the actuator 5 comprises a push rod supporting a transverse beam engaged by the levers for pivotal movement in response to the fluid pressure acting on the push rod, and means resiliently biassing the beam for permitting responsive movement of the push-rod when one or both levers is 10 blocked by the associated cam.’ 21. A valve according to any one of Claims 18 to 20 wherein the or each cam is mounted on a spindle for rotation therewith by a control knob for controlling operation of selected heating elements by the switch 15 assembly. 22. A valve according to any one of Claims 13 to 21 wherein the outlet is adapted for connection to the heat exchanger. 23. A valve according to any one of the preceding 20 Claims wherein the inlet and outlet are provided by a one piece valve body. 24. A valve according to Claim 1 substantially as - hereinbefore described with reference to Figures 4 to 8 of the accompanying drawings. 25 · 25. A water heater having a valve according to Claim 1 and a heat exchanger controlled by the switch assembly. 2 6. A water heater according to Claim 25 wherein the heat exchanger is connected to the outlet and includes electric heating elements controlled by the switch 30 assembly. 27. A water heater according to Claim 26 wherein the switch assembly includes a separate switch for each heating element, the switches being operable by a -25common actuator responsive. to the water pressure in the inlet chamber, and manually operable cam means for selectively controlling actuation of the switches for controlling the power input to the heat exchanger. 28. A water heater according Claim 27 wherein each switch is operable by a respective pivotal lever under the control of the actuator and the cam means comprises a separate cam for selectively blocking each lever. 29. A water l^eater according to Claim 27 or Claim 2 8 wherein the actuator is biassed towards a diaphragm arranged to sense the water pressure in the inlet chamber and is operable to actuate the switches when the water pressure overcomes the biassing. 30. A water heater according to any one of Claims 25 to 29 wherein the heat exchanger includes a thermal cut-out. 31. A water heater according to any one of Claims 25 to 30 wherein the heat exchanger includes a pressure relief valve. 32. A water heater according to any one of Claims 25 to 31 wherein the valve and heat exchanger are housed in a casing. 33. A water heater according to Claim 32 wherein the casing comprises a base plate and a removable cover plate. 3.4. A water heater according to Claim 25 substantially as hereinbefore described .with reference to Figures 1 to 8 of-the accompanying drawings. 35. A control valve for a water heater, the control valve comprising a one piece valve body with a water inlet and a water outlet, and the control valve further comprising the following components:-26a. an on/off water flow control valve; b. a flow control valve for controlling the rate of water flow; and c. a switch assembly for controlling an associate water heater; wherein the on/off water flow control valve comprises a closure member for opening and closing an inlet port opening to an inlet chamber, the water flow rate .control valve comprises a flow regulator for controlling the water flow rate from the inlet chamber to the outlet for delivery to the associate water heater, and the on/off closure member and flow regulator are coupled and operatively connected to a common control knob to provide a maximum said flow rate on rotation of the control knob in a direction to open the inlet port and thereafter reduce said flow rate by further rotation in the same direction. 36. A valve according to Claim 35 wherein the outlet is adapted for connection to a heat exchanger of the water heater. 37. A valve according to Claim 36 wherein the outlet has an external flange for connection to the heat exchanger inlet. 38. A valve according to Claim 36 or Claim 37 wherein the switch assembly is adapted for controlling at least one heating element of the heat exchanger. 39. A valve according to Claim 38 wherein .the or each heating element is controlled by an associate microswitch operable in response to the water pressure sensed by the switch assembly. 40. A valve according to Claim 39 wherein the switch assembly includes blocking means for selectively blocking operation of one or more microswitches. -2741. A valve according to any one of Claims 35 to 40 wherein the water flow rate control valve is operable to maintain the flow rate substantially constant at a given setting.

5. 42. An instantaneous electric water heater incorporating the control valve according to any one of Claims 35 to 41.