IE930069A1

IE930069A1 - Fluid heater

Info

Publication number: IE930069A1
Application number: IE006993A
Authority: IE
Inventors: Robert Meadows; Nicholas John Beck
Original assignee: Caradon Mira Ltd
Priority date: 1992-02-08
Filing date: 1993-02-01
Publication date: 1993-08-11
Also published as: GB2263965B; GB9202694D0; GB2263965A

Abstract

An instantaneous electric water heater comprises an on/off water flow control valve (3) (Fig 2, not shown) and a water flow regulator (4) (Fig 2, not shown) mechanically controlled by independent user operable control knobs (9, 10) (Figure 1, not shown), whereby the knob (10) may be left in an adjusted position when the water flow is turned off and on by the valve (3). The on/off valve (3) comprises a pilot operated diaphragm valve that is closed by the pressure differential across a flexible diaphragm 42 when a pilot valve 48 is closed and is opened by a reverse pressure differential when the pilot valve 48 is mechanically opened by actuation of the knob (9) via a cam 30 and lever 55. Two electric heating elements are controlled by microswitches actuated by levers actuated by a diaphragm responsive to water pressure. The knob (9) selects the power input by selectively blocking pivoting of the levers, via respective cams.

Description

^LUID HEATER ί This invention concerns improvements in or relating to fluid heaters and in particular, though not exclusively, instantaneous electric water heaters for showers and the like ablutionary appliances.

It is known to provide an instantaneous electric water heater in which an on/off flow control valve and a flow regulator are operable by a common control knob.

With this arrangement, the setting of the flow regulator to obtain a desired water temperature for a given power input to the heat exchanger is changed when closing the control valve. As a result, the flow regulator has to be set each time the water heater is used.

It is also known to provide an instantaneous electric water heater in which the on/off flow control valve is a solenoid valve.

Such solenoid valve and associated switch adds to manufacturing costs and necessitates connection to an electrical supply for operation.

In addition, solenoid valves have a fast response so as to open and close almost instantly. As a result, on closing, the water remaining in the heat exchanger is heated by the residual heat in the heat exchanger giving rise to problems of temperature overshoot on subsequent operation of the water heater.

It has been proposed to overcome this problem by the use of an electronic time delay circuit for controlling closure of the solenoid valve but this adds further to the manufacturing costs.

The present invention has been made from a consideration of these problems.

According to the broadest aspect of this invention, we provide flow control apparatus in or for a fluid heater comprising a mechanically actuable on/off flow control valve operable by a first control means and a flow regulator operable by a second control means .

The invented flow control apparatus provides independent control of the on/off valve and flow regulator so that the setting of the flow regulator is not affected by operation of the on/off valve. In addition, operation of the on/off valve does not require an electrical supply thereby reducing manufacturing costs and facilitating installation.

Preferably the on/off flow control valve comprises a valve member for controlling the flow from an inlet chamber through a valve seating to an outlet in response to pressure differentials between the inlet chamber on one side of the valve member and a control chamber on the other side of the valve member.

Advantageously, the valve member is adapted for delayed closure so that the fluid heater is flushed with cooler fluid reducing the risk of temperature overshoot on subsequent operation of the fluid heater.

Conveniently, delayed closure is provided by a control hole connecting the inlet chamber and control chamber for damping movement of the valve member towards the valve seating. The control hole may be dimensioned to provide any desired time delay on closing for a given application. 3Q In a preferred embodiment, the valve member comprises a flexible diaphragm of rubber or similar elastomeric material and the control hole is arranged to extend through the diaphragm. 01 Advantageously, the pressure differential across the valve member is controlled by a pilot valve actuated by the first control means for controlling flow from the control chamber to the outlet such that, when the pilot valve is closed, flow of fluid from the inlet chamber is prevented by the pressure differential across the valve member.

Advantageously, the first control means is operable to open the pilot valve against the biassing of a restoring force such that the pressure differential across the valve member is reversed allowing fluid flow from the inlet chamber.

Conveniently, the first control means is a manually rotatable member for actuating a push-rod to open the pilot valve. For example, the push-rod may be actuated by a cam mounted on a shaft rotatable by a control knob accessible to the user.

Advantageously, a switch assembly responsive to fluid flow is provided for controlling the power supply to an associate heat exchanger.

Preferably, the switch assembly is responsive to a pre-determined fluid pressure downstream of the valve seating that is lower than the fluid supply pressure.

In this way, the power supply is interupted when there is insufficient fluid flow but is unaffected by small changes in the fluid supply pressure.

Conveniently, indicator means is operable to warn the user of low fluid pressure causing the switch assembly to interupt the power supply to the heat exchanger. The indicator means may provide a visual and/or audio warning of low fluid pressure. 0i Advantageously, the heat exchanger has a plurality of heating elements and the first control member controls the switch assembly connecting the heating elements to the power supply for varying selectively the power input to the heat exchanger.

Preferably, each heating element has an associated switch actuated by the switch assembly in response to fluid pressure and the first control member has means for selectively blocking actuation of each switch.

Conveniently, the blocking means comprises a respective cam for each switch.

Advantageously, the heat exchanger includes a thermal cut-out for interupting the power supply to the heat exchanger if the fluid temperature exceeds a pre15 determined value.

Preferably, indicator means is operable to warn the user of high fluid temperature causing the cut-out to interupt the power supply to the heat exchanger.

The indicator means may comprise a visual and/or audio warning of high fluid temperature.

Advantageously, the flow regulator is adapted for maintaining substantially constant a selected flow rate. In this way, variations in the fluid supply pressure are compensated and the fluid outlet temperature from the heat exchanger is maintained substantially constant for a given power input.

In a preferred embodiment, the flow control apparatus and heat exchanger are housed in a casing of the fluid heater with the flow regulator positioned between the on/off valve and heat exchanger which are adapted respectfully for connection to a water supply and an ablutionary appliance, for example a shower.

According to another aspect of the invention, we provide an instantaneous electric water heater comprising an on/off flow control valve having a valve member movable relative to a valve seating to open and close the valve in response to pressure differentials arising across the valve member on rotation of first control means to actuate mechanically a pilot valve, a flow regulator operable independently of the on/off control valve by second control means for adjusting the flow rate, a heat exchanger, and a switch assembly responsive to water pressure for controlling power input to the heat exchanger.

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 incorporating flow control apparatus according to the invention; FIGURE 2 is a front view of the water heater shown in Figure 1 with the front cover removed; FIGURE 3 is a front view of the flow control valve and switch assembly of the water heater shown in Figures 1 and 2; FIGURE 4 is a side view of the flow control valve and switch assembly shown in Figure 3 in the direction of arrow A; FIGURE 5 is a rear view, partly in section, of the flow control valve and switch assembly shown in Figure 3 and showing the flow control valve closed; and FIGURE 6 is a rear view, similar to Figure 5 with parts of the switch assembly removed for clarity, and showing the flow control valve open.

The instantaneous electric water heater 1 for a shower shown in the accompanying drawings comprises a generally rectangular casing 2 housing an on/off flow control valve 3, a flow regulator 4, a heat exchanger 5 and a switch assembly 6.

The casing 2 has a back plate 7 for mounting on a wall or similar support surface and a detachable front cover 8 for access to the internal components.

The flow control valve 3 and flow regulator 4 are controlled by separate manually operable control knobs 9,10. The flow control knob 9 also controls the heat exchanger 5.

The flow control knob 9 has four angularly spaced apart settings designated stop, cool, low and high on the front cover 8.

The flow control valve 3 is closed when the flow control knob 9 is set at the stop position and is open when the flow control knob 9 is set at each of the other three positions.

A rotatable shaft 11 on which the flow control knob 9 is mounted carries a collar 12 provided with four angularly spaced recesses 13 for engagement by a spring detent 14 to retain the control knob 9 at each selected position.

The flow regulator knob 10 has nine angularly spaced apart positions designated 1 to 9 on the front cover 8 for adjusting the flow rate between minimum and maximum values.

The flow regulator 4 is connected between the flow control valve 3 and heat exchanger 5 and is constructed to maintain a selected flow rate substantially constant. A suitable flow regulator is disclosed in our co-pending UK Patent Application No.2,237,860 the disclosure of which is incorporated herein by reference, 0i The heat exchanger 5 has an outlet 15 for connection to a shower head (not shown) and a thermal cut-out 16 arranged to sense the temperature of the water flowing through the outlet 15 such that the power supply to the heat exchanger 5 is switched off if the water temperature exceeds a pre-determined value.

A neon lamp 17 mounted on the front cover 8 is connected to the thermal cut-out switch and is illuminated when the switch opens to indicate to the user that the power supply to the heat exchanger 5 has been interupted.

The heat exchanger 5 is also provided with a pressure relief valve 18 for relieving excess fluid pressure within the heat exchanger 5. A suitable pressure relief valve is disclosed in our UK Patent No.2,167,842 the disclosure of which is incorporated herein by reference.

In this embodiment the heat exchanger 5 has two 4.2kW heating elements (not shown) and the switch assembly 6 is responsive to water flow on opening the valve 3 to control the power supply to the heat exchanger 5 for energising neither, one or both heating elements according to the set position of the control knob 9. It will be understood, however, that the number and/or power rating of the heating elements may be changed as desired to suit requirements for a particular application. For example, there may be a single heating element of suitable rating.

The switch assembly 6 has a push-rod 19 actuated by a diaphragm 20 responsive to the water pressure in a control chamber 21 for controlling pivotal movement of a pair of bellcrank levers 22,23 arranged to actuate respective microswitches 24,25 associated with each heating element. 01 The push-rod 19 is biassed towards the diaphragm 20 by a return spring 26 and carries a transverse beam 27 biassed in the opposite direction by a spring 28.

When the water pressure in the control chamber 21 reaches a pre-determined value sufficient to overcome the bias of return spring 26, the diaphragm 20 deflects to displace the push-rod 19 and beam 27 so as to pivot the levers 22,23 and actuate the microswitches 24,25 to 1θ connect the power supply to the heating elements.

The pre-determined water pressure is selected to be lower than the water supply pressure so that the power supply is interupted if there is insufficient water flow but is unaffected by small changes in supply pressure.

The control knob 9 selects the power input to the heat exchanger 5 by selectively blocking pivotal movement of the levers 22,23 by means of respective cams 29,30 mounted on the shaft 11 to provide a different power input for each of the set positions cool, low and high in which the control valve 3 is open. Selective blocking of the levers 22,23 is permitted by the spring loading of the beam 27.

More particularly, in the cool position, both levers 22,23 are blocked by the associated cams 29,30 to prevent energisation of the heating elements giving a power input of OkW for cold water flow only.

In the low position, one lever 23 is blocked by the associated cam 30 and the other lever 22 is free to pivot under the control of the push-rod 19 to actuate the associated microswitch 24 and energise one heating element giving a power input of 4.2kW.

In the high position, both levers 22,23 are free to pivot under the control of the push-rod 19 to actuate the associated microswitches 24,25 and energise both heating elements giving a power input of 8.4kW for hot water flow.

The incoming power supply is connected to a terminal block 31 within the casing 2 and, in known manner, a remote isolating switch (not shown) is provided to comply with safety regulations and allow the power supply to be switched off for servicing and/or repair of the water heater. A neon lamp 32 mounted on the front cover 8 is illuminated to indicate that the power supply to the water heater is switched on.

A neon lamp 33 mounted on the front cover 8 is connected to the normally closed contact of microswitch 24 and is illuminated when the microswitch 24 is deactivated due to low water pressure to indicate to the user that the power supply has been interupted with the control knob 9 in either the low or high positions.

To prevent the lamp 33 being illuminated with the control knob 9 in either the cool or stop positions, the lamp 33 is wired in series with a microswitch 34 controlled by a cam (not shown) on the shaft 11.

The on/off control valve 3 comprises a body 35 having an inlet 36 for connection to a cold water supply (not shown) by means of an elbow connector 37 and an outlet 38 for connection to the flow regulator 4.

The elbow connector 37 is of the type disclosed in our co-pending UK Patent Application of even date the disclosure of which is incorporated herein by reference.

The inlet 36 opens to an annular inlet chamber 39 surrounding a hollow cylindrical upstand 40. The upper free end of the upstand 40 provides a seating 41 for a rubber diaphragm 42.

The diaphragm 42 is of the rolling edge type clamped at the marginal edge and is provided with a rigid central reinforcement plate 43 of metal or plastics.

The reinforcement plate 43 has a central flow guide 44 that is received within the upstand 40 and a control hole 45 providing a permanent fluid connection between the inlet chamber 39 and a control chamber 46 on opposed sides of the diaphragm 42.

The diaphragm 42 is movable relative to the valve seating 41 to open and close a central transfer port 47 in response to pressure differentials arising between the inlet chamber 39 and control chamber 46.

The pressure differentials across the diaphragm 42 are controlled by a pilot valve 48 having a valve member 49 movable relative to a seating 50 for controlling fluid flow from the control chamber 46 to the outlet 38 through an orifice 51.

The pilot valve member 49 is biassed by a return spring 52 to close the orifice 51 in the stop position of the flow control knob 9.

In this condition, the diaphragm 42 is biassed by the pressure differential between the control chamber 46 and inlet chamber 39 to engage the seating 41 and close the transfer port 47 preventing water flow through the valve 3.

One end of a push rod 53 sealed intermediate its ends by a pair of O-rings 54 engages the pilot valve member 49 and the other end is engaged by a bellcrank lever 55.

The bellcrank lever 55 is pivotal by means of a cam 56 mounted on the shaft 11 to displace the pilot valve member 49 against the biassing of the return spring 52 to open the orifice 51 on rotation of the control knob 9 to select any one of the cool, low or high positions.

In this condition, flow of water from the control chamber 46 to the outlet 38 exceeds flow of water from the inlet chamber 39 to the control chamber 46 through the control hole 45 and the pressure differential across the diaphragm 42 is reversed causing the diaphragm 42 to move away from the seating 41 to open the transfer port 47 and allow water flow through the valve 3.

The switch assembly 6 is mounted on the valve body 35 and the switch control chamber 21 is connected in the water flow path downstream of the seating 41 whereby the switch diaphragm 20 is responsive to water pressure with the valve 3 open.

When the control knob 9 is returned to the stop position, the cam 56 releases the bellcrank lever 55 and push-rod 53 whereby the pilot valve member 49 is displaced by the return spring 52 and water pressure in the control chamber 46 to close the orifice 51.

In this condition, the water pressure in the control chamber 46 increases and the pressure differential across the diaphragm 42 is reversed causing the diaphragm 42 to move towards and engage the valve seating 41 to close the transfer port 47 preventing fluid flow through the valve 3.

The control hole 45 in the diaphragm reinforcement plate 43 is sized so that there is a short delay after rotation of the control knob 9 to the stop position for the pressure in the control chamber 46 to increase sufficiently to reverse the pressure differential across the diaphragm 42 to close the valve 3.

The length of the time delay is chosen so that the heat exchanger 5 is partially flushed with cold water to dissipate some of the residual heat remaining in the heating elements with the remaining residual heat being used to pre-heat the water in the heat exchanger 5 without giving rise to any significant temperature overshoot on subsequent operation of the heat exchanger. As a result of such pre-heating, the time taken to heat the water to the selected temperature is reduced as compared with start-up from cold without causing an initial shot of hot water which could scald the user. A time delay of approximately 2½ seconds is sufficient for many applications but it will be understood that this may vary depending on operating conditions such as the water flow rate and the heat exchanger capacity and power rating.

As will be appreciated from the foregoing description, the on/off flow control valve and flow regulator are independently operable such that, for a given power input, the flow regulator can be set to provide a desired water temperature and this setting is 25 unaffected when the flow control valve is turned off.

As a result, for subsequent operation, the water is heated to the desired temperature set by the flow regulator and only minor adjustment of the flow regulator may be necessary to correct for any change in the temperature of the incoming water.

Furthermore, the on/off flow control valve is actuated mechanically allowing water flow without connection to an electrical supply. As a result, the valve can be operated to check for leaks during installation and/or repair or servicing with the power supply isolated for safety. Also, the on/off valve can be used with coin operation on heating.

Claims

1. Claims:

1. Flow control apparatus in or for a fluid heater comprising a mechanically actuable on/off flow control valve operable by a first control means and a flow 05 regulator operable by a second control means.

2. Flow control apparatus according to Claim 1 wherein the on/off flow control valve comprises a valve member for controlling the flow from an inlet chamber to an outlet in response to pressure differentials 10 between the inlet chamber on one side of the valve member and a control chamber on the other side of the valve member.

3. Flow control apparatus according to Claim 2 wherein the valve member is adapted for delayed 15 closure.

4. Flow control apparatus according to Claim 3 wherein delayed closure is provided by a control hole connecting the inlet chamber and control chamber for damping closing movement of the valve member. 20

5. Flow control apparatus according to Claim 4 wherein the valve member comprises a flexible diaphragm of rubber or similar elastomeric material and the control hole is arranged to extend through the diaphragm. 25

6. Flow control apparatus according to any one of Claims 2 to 5 wherein the pressure differential across the valve member is controlled by a pilot valve actuated by the first control means for controlling flow from the control chamber to the outlet such that, 30 when the pilot valve is closed, flow of fluid from the inlet chamber is prevented by the pressure differential across the valve member. 1 δ 01

7. Flow control apparatus according to Claim 6 wherein the first control means is operable to open the pilot valve against the biassing of a restoring force such that the pressure differential across the valve 05 member is reversed allowing fluid flow from the inlet chamber.

8. Flow control apparatus according to Claim 6 or Claim 7 wherein the first control means is a manually rotatable member for actuating a push-rod to open the pilot valve.

9. Flow control apparatus according to Claim 8 wherein the push-rod is actuated by a cam mounted on a shaft rotatable by a control knob accessible to the user.

10. Flow control apparatus according to any one of the preceding Claims wherein a switch assembly responsive to fluid flow is provided for controlling the power supply to an associate heat exchanger.

11. Flow control apparatus according to Claim 10 20 wherein the switch assembly is responsive to a predetermined fluid pressure lower than the fluid supply pressure.

12. Flow control apparatus according to Claim 11 wherein indicator means is operable to warn the user of 25 low fluid pressure causing the switch assembly to interupt the power supply to the heat exchanger.

13. Flow control apparatus according to Claim 12 wherein the indicator means provides a visual and/or audio warning of low fluid pressure.

14. Flow control apparatus according to any one of Claims 10 to 13 wherein the heat exchanger has a plurality of heating elements and the first control means controls the switch assembly connecting the 01 heating elements to the power supply for varying selectively the power input to the heat exchanger.

15. Flow control apparatus according to Claim 14 wherein each heating element has an associated switch θ 3 actuated by the switch assembly in response to fluid pressure and the first control means has means for selectively blocking actuation of each switch.

16. Flow control apparatus according to Claim 15 wherein the blocking means comprises a respective cam 10 for each switch.

17. Flow control apparatus according to any one of Claims 10 to 16 wherein the heat exchanger includes a thermal cut-out for interupting the power supply to the heat exchanger if the fluid temperature exceeds a pre15 determined value.

18. Flow control apparatus according to Claim 17 wherein the temperature indicator means is operable to warn the user of high fluid temperature causing the cut-out to interupt the power supply to the heat exchanger.

19. Flow control apparatus according to Claim 18 wherein the temperature indicator means provides a visual and/or audio warning of high fluid temperature.

20. Flow control apparatus according to any one of 25 Claims 10 to 19 wherein the flow regulator is positioned between the on/off valve and the heat exchanger.

21. Flow control apparatus according to any one of the preceding Claims wherein the flow regulator is adapted 30 for maintaining substantially constant a selected flow rate.

22. A fluid heater comprising flow control apparatus according to any one of the preceding Claims. 01

23. An instantaneous electric water heater comprising an on/off flow control valve mechanically operable by first control means, a flow regulator operable independently of the on/off control valve by second 05 control means for adjusting flow rate, a heat exchanger, and a switch assembly responsive to water pressure for controlling power input to the heat exchanger.

24. Flow control apparatus in or for a fluid heater 10 substantially as hereinbefore described with reference to the accompanying drawings.