WO1993015367A1

WO1993015367A1 - Continuous water heater

Info

Publication number: WO1993015367A1
Application number: PCT/AU1993/000038
Authority: WO
Inventors: James Anthony Mckay; Lynton John Mckay
Original assignee: Sheringham Investments Pty. Ltd.
Priority date: 1992-01-29
Filing date: 1993-01-29
Publication date: 1993-08-05

Abstract

A continuous water heater (10; 40; 50) having a hot water tank (16), heating means (32) in tank (16) and a hot water outlet (34). Hot water is removed from outlet (34) by varying the volume of tank (16) using a resiliently biased piston (20) through the bias of spring (22) and/or water pressure from a cold water inlet (18). The invention also discloses use of an expansion chamber (76) coupled to tank (16) by a tube (84) having a pump (86) in line with tube (84).

Description

CONTINUOUS WATER HEATER

This invention relates to a continuous water heater and has been devised particularly though not solely for the continuous supply of boiling hot water in small quantities. The invention may also be applicable to any type of hot water service - including solar.

It is desirable to provide a continuous water heating unit which will enable boiling (which term includes near boiling, i.e. 98-

100 ^# C) hot water to be provided in small quantities on demand without manually refilling the unit. Such a unit is particularly desirable in applications where small quantities of tea or coffee are required to be made such as in the home or in small offices.

Units of the abovementioned type are described in Australian Patent Application Nos 36358/78 and 64290/80. These units are wall mounted and have a cold water tank separated from the area of a tank containing the hot water so that addition of further cold water does not have the effect of reducing the temperature of all the water within the tank. The hot water is gravity fed through an outlet in or near the base of the unit. In view of the gravity feed requirement these units cannot be incorporated in a cabinet with the tanks mounted below the hot water outlet. In addition, a conventional type of tank is not desirable because of the unacceptable level of cooling which occurs as cold water is added.

It is an object of the present invention to provide a continuous water heater that overcomes the abovementioned disadvantage.

In accordance with a preferred aspect of the present invention there may be provided a continuous water heater including a tank for containing hot water, heating means in said tank, a hot water outlet at or adjacent the top of said tank and said tank has a variable volume whereby hot water is released from said outlet by varying the volume of said tank. In one preferred embodiment the volume of said tank is varied by a resiliently biased piston within a closed cylinder, whereby said tank is located on one side of said piston.

In one practical embodiment the other side of said piston defines a cold water tank, said tanks being linked by a bleed tube.

A cold water inlet is provided into said cold water tank to provide pressure to cause displacement of said piston to force hot water from said outlet.

In a further practical embodiment the cold water inlet is provided adjacent the bottom of said tank and hot water is released through a valve in said outlet, said piston providing pressure to force hot water through said outlet.

In order that the invention may be clearly understood and readily put into practical effect, preferred non-limitative embodiments of a continuous water heater will now be described with reference to the accompanying drawings in which:-

Fig. 1 is a diagrammatic cross-sectional elevation of a first embodiment of a continuous water heater made in accordance with the invention; Fig. 2 is a diagrammatic cross-sectional elevation of a second embodiment of a continuous water heater made in accordance with the invention; and

Fig. 3 is a diagrammatic cross-sectional elevation of a third embodiment of a continuous water heater made in accordance with the invention.

In Fig. 1 there is shown a continuous water heater 10 which includes a storage vessel 12. Storage vessel 12 may be in any shape but it is preferably cylindrical. Vessel 12 is subdivided into two chambers 14, 16 by piston 20. Chamber 14 contains cold water whilst chamber 16 contains hot water. Cold water enters chamber 14 through a cold water inlet 18. Piston 20 is resiliently biased by a spring 22 of predetermined tension.

Cold water enters chamber 16 from chamber 14 via a bleed tube 24. The flow rate is controlled by a valve or throttle device 26 which may be variable to allow for adjustability. A temperature sensor 28, of any known type, in one embodiment is positioned adjacent the exit 30 of bleed tube 24 to sense the temperature of water in chamber 16. Sensor 28 is connected via electronics (not shown) to a heating device 32, normally an electric heating element, for maintaining the water in chamber 16 near boiling point. Hot water is drawn off through outlet 34 located on the top of, or adjacent the top of storage vessel 12.

In use, the water heater 10 operates by varying the volume of water in the chambers 14, 16. Cold water is introduced into chamber 14 through inlet 18 and causes piston 20 to move as a result of the pressure increase. Chamber 16 is thus reduced in volume and hot water issues from outlet 34. Thus, through the use of a valve (not shown) in inlet 18 or outlet 34 hot water is obtained from outlet 32. The amount of hot water obtained will equal the amount of cold water that enters chamber 14. Piston 20 will be under tension from spring 22 and will tend to return to its relaxed state. Return of piston 20 will force cold water through bleed tube 24. Temperature sensor 28 will detect the drop in temperature caused by the inflow of cold water and heating device 32 will be activated. The rate of inflow of cold water is controlled by the tension of spring 22 and the bleed rate of the valve or throttle device 26. The bleed rate should not be greater than the rate of heating of the heating device 32 thereby to maintain the temperature of the heated water within the chamber 16 substantially constant. Once piston 20 has reached the relaxed state of spring 22 heating device 32 will only be activated to maintain a steady-state condition until hot water is withdrawn again. Fig. 2 shows a second embodiment of a water heater 40 and identical reference numerals have been used for similar components to those shown in Fig. 1 to avoid duplication of description. The major differences between the embodiments are that cold water chamber 14 has been eliminated together with bleed tube 24. Cold water is fed into chamber 16 adjacent temperature sensor 28 via inlet 18. A pressure and volume regulator 42 is located in inlet 18 and an outlet valve 44 is provided in outlet 34.

In use, cold water is introduced at a slow rate through pressure regulator 42. Piston 20 is moved towards spring 22 to compress same. Movement of piston 20 continues until it hits stop 46. The further increase in pressure which will then occur will cause pressure and volume regulator 42 to shut off the cold water supply through inlet 18. Hot water is released as required through outlet valve 44 under pressure from piston 20.

The invention is not totally reliant on separating the hot and cold water by thermal stratification in view of the variable volume operation of the invention. Although shown as horizontally mounted the storage vessel 12 may be vertically mounted. hi Fig. 3 a third embodiment of a water heater 50 is shown and identical reference numerals have been used for similar components to those shown in Fig. 1 to avoid duplication of description. The major differences between Figs. 1 and 3 are that bleed tube 24, which was previously an external arrangement, has now become an internal arrangement by its incorporation in piston

20, and that the temperature sensor 28 is located above the heating element 32 whereby to more quickly detect the actual temperature of the heated water. Piston 20, in this embodiment comprises two parts 52, 54 which fit together to form a diaphragm type pressure sensitive flow regulator. Part 52 has a U-shaped passage 56 having an inlet

58 and an outlet 60. Outlet 60 opens into a reservoir 62. Leading from reservoir 62 is a passage 64 which opens into chamber 16 through outlet 66. Part 54 is a lid for part 52 and has a locating annulus 68 co-operating with a groove in part 52. Part 54 also acts as a diaphragm which deflects according to the pressure differential between chambers 14 and 62. Part 54 also incorporates a lip seal 75 to prevent leakage between chambers.

A boss 70 fits into inlet 58 and has a flowthrough bore 72 opening into chamber 14. A needle valve 74, preferably tapered as illustrated, is attached to the said diaphragm 54 and protrudes into outlet 60 to act as a flow restrictor. In the preferred embodiments illustrated, parts 54, 70, 72 and 74 and sealing lip 75 are constructed as a one-piece moulding, but it should be realised that in an alternative embodiment those parts 54, 70, 72, 74 and 75 could constitute separate component parts. In use, cold water is introduced into chamber 14 through inlet 18 and causes piston 20 to move as a result of the pressure increase. Chamber 16 is thus reduced in volume and hot water issues from outlet 34. The amount of hot water obtained will equal the amount of cold water that enters chamber 14. Piston 20 will be under compression from spring 22 and will tend to return to its relaxed state. Return of piston 20 will force cold water to flow through bore 72. Cold water will flow into passage 56 to reservoir 62 and exit through passage 64 under the control of tapered needle valve 74. The differential pressure between said chambers 14 and 62 will deflect said diaphragm 54 and force tapered needle valve 74 to restrict outlet 60 and control cold water entering chamber 16, via said passage 64, to allow a substantially constant flow rate of water to pass through said outlet 60 and therefore into said chamber 16 regardless of pressure differential caused by variations in spring tension and frictional forces. Temperature sensor 28 will detect the drop in temperature caused by the inflow of cold water and heating device 32 will be activated. Once piston 20 has returned to its rest position the said flow of water will cease and heating device 32 will only operate to maintain a steady temperature. The parameters of spring tension of spring 22, frictional forces of piston 20 and valve characteristics of valve 74 can be varied to achieve the desired flow rate, which should not be greater than the rate of heating of the heating device 32, thereby to maintain the temperature of the heated water within the chamber 16 substantially constant.

In Fig. 3 an additional improvement is also shown. This improvement could also be attached to the embodiments shown in

Figs. 1 and 2 if required. As storage vessel 12 is not under pressure when operating, a certain amount of steam can form around heating device 32. This formation of steam may displace hot water which may dribble from outlet 34. To avoid this problem an expansion chamber 76 is provided above storage vessel 12. Expansion chamber

76 has a vent 78 and inlet 80. An outlet 82 adjacent heating device 32 allows any increased volume of water produced by thermal expansion or displaced by the said steam, to pass from outlet 82 to inlet 80 through a connecting tube 84. The accumulated water in expansion chamber 76 can be returned to chamber 16 when hot water is drawn through outlet 34. A small pump 86, preferably of a centrifugal type, but which could also be a positive displacement type activated by the greater pressure of the incoming water at 18 empties expansion chamber 76 and returns the accumulated water to the bottom of chamber 16 adjacent heating device 32. This accumulated water may be at a lower temperature than that of chamber 16 but will be quickly reheated. Switching on pump 86 only when hot water is withdrawn from outlet 34 prevents backflow which is a common problem with prior art expansion chambers. Pump 86 will also allow flow of water in both directions when not operating. It is to be understood that the abovementioned expansion chamber arrangement is not restricted to the embodiments disclosed but may be included on other displacement type water heaters.

It is believed that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts and that changes may be made in the form, construction and arrangement of the continuous water heater described without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the forms hereinbefore described being merely preferred embodiments thereof.

Claims

1. A continuous water heater including a tank for containing hot water, heating means in said tank, a hot water outlet at or adjacent the top of said tank and said tank has a variable volume whereby hot water is released from said outlet by varying the volume of said tank.

2. The continuous water heater of claim 1, wherein the volume of said tank is varied by a resiliently biased piston within a closed cylinder, whereby said tank is located on one side of said piston.

3. The continuous water heater of claim 2, wherein the other side of said piston defines a cold water tank, said tanks being linked by a bleed tube.

4. The continuous water heater of claim 3, wherein said cold water tank includes a cold water inlet providing pressure to cause displacement of said piston to force hot water from said outlet.

5. The continuous water heater of claim 2, wherein adjacent the bottom of said tank and hot water is released through a valve in said outlet, said piston providing bias to force hot water through said outlet.

6. The continuous water heater of claims 3 or 4, further including a temperature sensor within said tank, said temperature sensor located between said heating means and said bleed tube adjacent the bottom of said tank.

7. The continuous heater of claim 5, further including a temperature sensor within said tank, said temperature sensor located between said heating means and said cold water inlet.

8. The continuous water heater of claim 1, wherein the volume of said tank is varied by a resiliently biased piston within a closed cylinder, said piston dividing said closed cylinder into said tank and a cold water tank, said piston including a flow regulator to allow controlled flow of water from said cold water tank to said tank.

9. The continuous water heater of claim 8, including a temperature sensor within said tank, said temperature sensor located above said heating means.

10. The continuous water heater of claim 9, wherein said flow regulator includes a tapered needle valve within said piston.

11. The continuous water heater of claim 10, wherein said flow regulator includes a lip seal and a pressure sensing diaphragm.

12. The continuous water heater of claim 11, wherein said flow regulator includes a needle valve, a lip seal and a pressure sensing diaphragm, and is constructed as a one-piece moulding.

13. The continuous water heater of any one of the preceding claims, further including an expansion chamber above said tank, said expansion chamber being coupled to said tank by a tube.

14. The continuous water heater of claim 13, wherein said tube connects to said tank adjacent said heating device.

15. The continuous water heater of claim 13 or 14, further including a pump in said tube, said pump returning any accumulated water in said expansion chamber when hot water is withdrawn from said outlet.

16. A continuous displacement type water heater including an expansion chamber above a tank to be heated, said expansion chamber coupled to said tank by a tube opening into said tank adjacent a heating device in said tank, and a pump in said tube, said pump returning any accumulated water in said expansion chamber when hot water is withdrawn from said water heater and said pump allowing flow in both directions in the off state.