This invention relates to a thermostatic hot water valve.

Thermostatic hot water radiator valves, for example, hot water central heating systems, are well known and typically function by the response of a set of liquid filled anaeroid bellows to the ambient air temperature within the room to be heated. In most cases the required response temperature is set by rotating the top cover of the valve so that this action compresses the bellows to the required degree so that a further rise in temperature expands the bellows and shuts off, or restricts, the flow of heating water in the system.

There are many occasions when it is not desired to heat various rooms in the home and in this case it is tedious and laborious to have to visit each room in turn and shut off the valve setting only to later return to turn the valve back to its control setting. It would be extremely convenient and labour saving to be able to keep each radiator thermostatic valve at some desired fixed setting and to be able to shut it off completely at each location or at some single console location.

Accordingly the present invention provides a hot water valve including an adjustable thermostatic control element responsive to the ambient air temperature, and heating means for heating the control element sufficiently to close the valve irrespective of the ambient air temperature and without disturbing the adjustment of the control element.

In an embodiment of the invention the valve comprises a conventional anaeroid bellows control element which has in intimate contact therewith a resistor element which can generate the few watts of energy needed to keep the bellows in the expanded condition so that the flow of hot water to the radiator is completely interrupted so long as the heating element is energised.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawing, which is a sectional elevation through the thermostatic valve.

The thermostatic valve comprises a valve body 1 whose valve seating IA can be closed by a seating washer 2 which is fixed to a valve stem 3. The movements of this stem 3 are determined by the equilibrium state of two distinct forces. The first force is generated by the action of a spring 4 tending to keep the valve open because of its action against a stem stop 5. The second force is a forward, or closing, force and is generated by the thermal expansion of an anaeroid bellows 6 which, via a bellows shaft 7a, pushes the valve stem forward at 7. The valve has an outer cover 8 which is mounted on the valve body 1 for rotation about the axis of the valve

stem 3, in particular by means of a fixed external circumferential rib 11 on the valve body which locates in and serves as a bearing for a circumferential groove 12 on the inside surface of the outer cover 8.

The inside surface of the outer cover 8 also has a continuous spiral groove 13, which is engaged by the opposite ends of a cross-member 14, such that rotation of the outer cover 8 causes the cross-member 14 to move axially left or right relative to the valve body 1. At its centre the cross-member 14 engages one end of a bellows spring 9, and hence rotation of the outer cover 8 loads the spring 9 to an extent determined by the axial position of the cross-member 14.

Thus the valve is adjusted, that is, the control setting for a desired air temperature is obtained, by rotating the outer cover 8 to load the spring 9 of the bellows to a desired degree. It should be noted that the cross member 14 has an aperture 14a through which the bellows shaft 7a passes, so that the cross-member only engages the spring 9.

Up to this point in the description of this embodiment the valve is constructed in a similar manner to those of the prior art, but the valve additionally has an electrical cut-off control which is obtained by the incorporation of a resistive heating element 10 into the valve so that good heat transfer occurs between it and the top surface of the liquid-filled anaeroid bellows 6. The preferred resistive heating element need only dissipate a few watts, sufficient to expand the bellows 6 to close the valve irrespective of the ambient temperature, and it is preferably selected from the cheap range of cracked carbon low voltage

composition resistors which are freely available at component shops. The resistor 10 is preferably fixed directly to the top of the bellows 6, for example using a metal-based resin adhesive, and has low voltage leads 16 which passes through the top end 15 of the outer cover 8 of the valve.

To avoid the leads 16 being twisted when the temperature setting of the valve is adjusted by rotating the valve cover 8, the top end 15 is formed as a separate component to the main body of the valve cover 8 and has a circumferential edge which sits in a groove on the inside surface of the valve cover 8. By this means the top end 15 is rotatable relative to the main body of the cover 8 so that it can remain stationary as the valve cover 8 is rotated.

In use in a typical hot water central heating system, at least one radiator has a valve as described above whose resistive heating element 10 is connected across a low voltage source indicated schematically at 17, and can be switched on and off using a switch 18. The switch may be located locally at the valve or radiator, or preferably lead back to some convenient central point where a number of like thermostatic valves associated with the radiators of the whole central heating system, can be wired into a small central console so that any valve in any room can be remotely switched on or off at will. Such wiring is inconspicuous, and the element 10 does not disturb the desired normal setting of the valve for varying ambient temperatures. In practice the low voltage supply 17 can be between 9 and 12 volts ac/dc and is easiest obtained from a good quality double insulated mains transformer with an isolated secondary winding.

Other ways of applying heat energy to the liquid filled bellows of thermostatic valves will be apparent to those skilled in the art, but the innovative principle of this invention lies in the thermal driving of the bellows or other thermostatic control element to a shut-off condition irrespective of the ambient temperature which normally is the control factor of the valve.