GB2295034A

GB2295034A - Instantaneous water heater

Info

Publication number: GB2295034A
Application number: GB9522159A
Authority: GB
Inventors: Erwin Witzki
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-11-12
Filing date: 1995-10-30
Publication date: 1996-05-15
Anticipated expiration: 2015-10-30
Also published as: GB9522159D0; DE4440492A1; GB2295034B; CN1128855A; KR960018419A

Description

Instantaneous water heater 5 Prior art

The invention starts from an instantaneous water heater according to the generic category of the main claim. In a known water heater of this generic category (DE 38 05 441 C2), the adjusting device influencing the flow of water has an axially guided valve closing member whi ch can be adjusted by an electric motor via gearing. This embodiment is relatively complicated and requires_ additional means if pressure fluctuations in the water network are to be rapidly stabilized. For this purpose, an impeller driven by the f low of water and mounted on the actuating- stem of the valve closing member is provided in the known arrangament, to which impeller a permanent magnet is fastened which additionally acts on the electric motor- via a Hall transmitter and the regulating device. Advantages of the invention - The arrangement according to the invention, having the characterizing features of the main claim, is distinguished by a simple structure which works largely free of friction and in which network pressure fluctuations are also stabilized without additional means almost without delay. The invention can preferably be used in electrically heated instantaneous water heaters in which the temperature selector is the set-point adjuster of the temperature regulator.

Advantageous further developments of the arrangement according to the main claim are possible by the features recited in the subclaims.

An embodiment requiring only slight actuating forces as a result of servo action is obtained when the regulating pressure is formed in a control -pressure chamber which is defined by the diaphragm on the side 2295034 remote from the valve body and lies in the course of a bypass line which avoids the valve passage and whose effective cross-section of flow is preferably electrically controlled as a function of the set-point deviation from the outlet temperature.

A proven embodiment known from gas volume regulators is obtained when the effective cross-section of f low of the bypass is controlled by a valve device which is allocated to at least one of the two mouths of the bypass in the control -pressure chamber and has an electrically heated actuator changing its shape under the action of heat.

Various expansion elements can be used as electrically heated actuator. it is especially advantageous when the actuator is a bimetal element which is preferably heated by electrical pulses and responds especially quickly and accurately to changes in the heating. The heating can be effected directly with the bimetal element as electric resistance. However, it is also possible to attach an electric resistance wire to a bimetal strip in an insulated manner. To compensate for the ambient temperature, the support of the bimetal element can likewise be made of bimetal.

In order to eliminate the effects of pressure differences between control pressure and atmospheric pressure on the actuating forces, it is proposed that the actuator act on the valve device via a pivoted lever, the pivoting plane of which is arranged at least approximately perpendicularly to the regulator housing wall provided with the lever leadthrough.

The regulating valve can be under the effect of a regulating spring. If the valve body area and the effective diaphragm area are specially adapted to one another, the regulating spring can also be omitted.

If an orifice or a venturi tube to which the bypass leading through the control -pressure chamber is attached is provided at the outlet of the regulating valve, the control pressure also becomes dependent upon the flow volume.

3 - Drawing Three exemplary embodiments of the invention are shown in the drawing and are described in more detail below. In the drawing, Figure I shows in a simplified form an electrically heated instantaneous heater in accordance with the first exemplary embodiment, Figure 2 shows to an enlarged scale the water- volume regulator of the instantaneous heater according to Figure 1, and Figures 3 and 4 show the water-volume regulators of the second and third exemplary embodiment to the scale of Figure 2.

Description of the exemplary embodiments

The-instantaneous heater according to Figures 1 -and 2 has a cold-water connection 10 from which a line 12 is leads to an inlet 14 of-an inner body 16. The latter is provided on the inside with dividing walls 18 which form a meander-shaped flow passage 20 for the water to be heated, which flow passage 20 starts at the inlet 14 and leads to an outlet 22. The outlet 22 is connected via a line 24 to a hot-water connection 26 at the appliance. Arranged in the straight sections of the flow passage 20 are a plurality of electric heating bodies 28 which, depending on the heat requirement, can be connected individually or in groups to a network connection 32 via a control unit 30. The control unit 30 contains a temperature regulator (not shown in detail) which has a setpoint adjuster 34, which can be operated by the user of the appliance and serves to set the outlet temperature, and a temperature sensor 36, detecting the outlet temperature, on the line 24. The flow passage 20 is defined at one point by a diaphragm 38 which opens a network switch 40 via a plunger when the water pressure in the inner body 16 exceeds a predetermined value.

The line 12 coming f rom the cold-water connection 10 runs via a water-volume regulator 42, the regulating pressure of which is controlled by the control unit 30 in accordance with the set-point deviation of the outlet temperature. As long as a heat requirement predetermined by the degree of opening of a tap valve and by the desired temperature does not exceed the rated capacity of the appliance, the control unit 30 acts in a controlling manner only on the heating output for the purposes of keeping the set point of the outlet temperature constant.

However, as soon as and as long as the heat requirement exceeds the rated capacity of the appliance, the control unit 30 also acts on the watervolume regulator 42 for the purposes of throttling the flow in such a way that the set outlet temperature is maintained.

The water-volume regulator 42 (Figure 2) has a diaphragm-controlled regulating valve 44 which monitors a through opening 50 lying between an inlet chamber 46 and an outlet chamber 48. The regulating valve 44 has a valve body 52 which is loaded by a closing spring 54 and is connected to a diaphragm 58 via a plunger 56. The diaphragm 58 separates the inlet chamber 46 from a control -pressure chamber 60. The inlet chamber 46 is connected to the cold-water connection 10 and the outlet chamber 48 is connected to the inner body 16 of the appliance via the line 12.

The control chamber 60 is connected via a narrow passage 62 to the inlet chamber 46 and via a narrow passage 64 to the outlet chamber 48. A bypass avoiding the through opening 50 is thereby formed, the effective cross-section of flow of which is controlled by a valve device designated overall by the reference numeral 66. The latter has a bimetal body 68 as actuator, which can be electrically heated via a line 70 monitored by the control unit 30. The bimetal body 68 acts on a lever arm 72, passed through the valve housing in a sealed-off manner, of a double- armed lever pivotably mounted at 74, the other lever arm 76 of which has a closing member 78 which monitors the mouth 80 of the passage 66.

The water-volume regulator 42 works in a known manner such that a constant volumetric flow of water is obtained largely irrespectively of the inlet pressure p. in the inlet chamber 46 at each degree of opening of the tap valve. Pressure fluctuations in the water network are thereby stabilized and fluctuations in the outlet tem- perature at the appliance which are caused by such pressure fluctuations are avoided. The degree of opening of the regulating valve 44 also depends on the pressure in the control -pressure chamber 60, which pressure in turn depends on the position of the closing member 78 relative to the mouth 80 of the passage 62, that is on the degree of heating of the bimetal body 68.

As long as the heat requirement does not exceed the rated capacity of the appliance, the bimetal body 68 remains unheated and the regulating range for the flow volume is maintained without restriction up to the -predetermined maximum value specific to the appliance.

However, if the heat requirement -exceeds the rated -capacity of the appliance,- the control unit 30 brings -about -the heating of the bimetal body 68, which as a - result bends to a greater extent than shown in Figure 2 and thereby pivots the closing body 78 further towards the mouth 80 of the passage 62. The result of this is that- the pressure in the control -pressure chamber 60 drops towards the outlet pressure p. in the outlet chamber 48 and the regul_ating cross-section of the regulating valve 44 becomes constricted. The outlet pressure p, and with it the regulated volumetric flow of water are thereby also reduced. The regulation is designed in such a way that the volumetric flow of water is in each case throttled to such a considerable degree that the outlet temperature set at the set-point adjuster 34 is reached or maintained.

The exemplary embodiment according to Figure 3 differs from the embodiment described above only by virtue of the fact that the bimetal body 68 acts via a double lever 82 on a closing body 86 monitoring the mouth 84 of the passage 64. During heating of the bimetal body 68 as a result of increased heat requirement, the pressure in the control-pressure chamber 60 is here lowered towards the outlet pressure p. by opening the passage 64.

In the exemplary embodiment according to Figure 4, the bimetal body 68 acts on both closing bodies 78 and 6 - 86 via a lever system 88 in the sense described above, as a result of which lower actuating forces than in the other embodiments are obtained.

The pressure in the control-pressure chamber 60 can be made more dependent upon the outlet pressure p. if the passage 64, as shown in Figures 2, 3 and 4, is attached to a venturi tube 90 in the regulator outlet. But this is not absolutely necessary.

7 -

Claims

Claims

1. instantaneous water heater, having a temperature selector and a temperature regulator for the outlet temperature, which during a heat requirement exceeding the-rated capacity of the appliance acts on an adjusting device, influencing the flow of water, for throttling the water volume, characterized in that the adjusting device has a water-volume regulator (42) having a diaphragmcontrolled-regulating valve (44), the regulating pressure of which is controlledin-accordance with the deviation of thd outlet temperature from the set point.

2. Water heater according to Claim 1, characterized is in that the regulating pressure is formed in a control pressure-chamber (60) which is defined by the diaphragm (58) on the side re mote from the valve body (52) and lies in the course of a bypass line (62, 64) which avoids the valve passage (50)-and whose effective cross-section of flow is preferably electrically controlled as a function of the set-point deviation from the outlet temperature.

3. - Water heater according to Claim 2, characterized in that the effective cross-section of flow of the bypass (62, 64) is controlled by a valve device (78, 86) which is allocated to at least one of the two mouths (80, 84) of the bypass in the control -pressure chamber (60) and has an electrically heated actuator (68) changing its shape under the action of heat.

4. Water heater according to Claim 3, characterized in that the actuator (68) is a bimetal element preferably heated by electrical pulses.

5. Water heater according to Claim 4, characterized in that the actuator (68) is arranged on a support which is itself made of bimetal for compensating for ambient temperature fluctuations.

6. Water heater according to one of Claims 3 to 5, characterized in that the actuator (68) acts on the valve 8 device via a pivoted lever (72, 76, 82, 88), the pivoting plane of which is arranged at least approximately perpendicularly to the regulator housing wall provided with the lever leadthrough.

11. A water heater substantially as herein described with reference to Figures 1 and 2, Figures 1 and 3, or Figures 1 and 4 of the accompanying drawings.