GB2183011A

GB2183011A - Thermostatic valve actuator

Info

Publication number: GB2183011A
Application number: GB08625784A
Authority: GB
Inventors: John Patrick Driver
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-11-19
Filing date: 1986-10-28
Publication date: 1987-05-28
Also published as: GB8528395D0; GB8625784D0

Abstract

A thermostatically controlled valve actuator (1) comprises a temperature sensor (2), a drive means associated with said sensor, a valve actuation means (7) driven in a first mode by the drive means in response to a temperature value sensed by said sensor (2), and a heating element (8) juxtaposed the temperature sensor and adapted to heat the sensor thereby to cause the valve actuation means (7) to move to a second, at least partially closed, mode. With the actuator in its second mode the sensor (2) is still responsive to changes in ambient air temperature by virtue of the design being arranged to avoid "heat blanket" effects. As particularly described the valve and actuator form part of a space heating system and the element (8) is preferably operated by a timer to hold one zone, say a bedroom zone, at a lower temperature than the remaining zone(s). <IMAGE>

Description

SPECIFICATION Thermostatic valve The present invention relates to thermostatically controlled valves, and particularly to actuators therefor. It also relates to central heating and similar systems controlled thereby.

It is well known to provide in a central heating system, a plurality of radiators heated by a central heating fluid, said fluid being controlled individually at each radiator by a thermostatically controlled valve. These valves are so adjusted that they open and close in response to the ambient air temperature of the zone in which they are situated and hence control the temperature in any particular zone to a desired level.

Very few heating zones require heating only to a single temperature throughout, for example, a twenty-four hour period. Very often zones such as, for example, bedrooms, need to be heated to 20"C for short periods in the morning and in the evening whereas other portions of a dwelling may need to be heated to 20"C at times when the said bedrooms are not heated.

Conventionally, the control of such zones has been achieved by providing in the heatexchange fluid flow line a motorised valve associated with a timer. Such motorised valves are comparatively expensive both to manufacture and instal and must be associated with means for connection to the mains supply of electricity. Accordingly changing the zone characteristics of a heating area utilising motorised valves is. a complex business requiring re-routing of the necessary electrical cables, and re-plumbing the motorised valve.

An attempt has been made to achieve zone heating particularly in central heating systems by a more economical and readily installed means in GB-A-2017263. This has been arranged by arranging, in association with individual thermostatically controlled valves, a heating means associated with the heat sensor portion thereof. However, whereas this works well enough it requires a feed back to a central controller to control the heat output of the heating elements. This is because of the "heat blanket" effect in which the heat from the heating element heats the space adjacent the sensor and hence prevents the sensor from sensing anything other than major changes in the temperature of the ambient air.Because of this a central controller needs not only to switch the heating elements on and off, but also to control their heat output since the act of switching on the heating elements also practically removes the heat sensing capabilities of the sensor relative to the ambient air temperature.

The present invention is characterised by heating means which apply just enough heat to raise the temperature of the sensor to a value above the ambient air in the surrounding zone so as to close, or at least partially close, the valve actuator means during a timed period, while also allowing changes in the temperature of the ambient air to register and be acted upon by the sensor.

According, therefore, to the present invention there is provided a thermostatically controlled valve actuator comprising a temperature sensor, a drive means associated with said sensor, a valve actuation means driven in a first mode by said drive means in response to temperature values sensed by the said sensor, and a heating element juxtaposed the temperature sensor and adapted to heat the sensor and thereby to cause the valve actuation means to move to a second, at least partially closed, mode; characterised in that the actuator is so designed that in the second mode it is still responsive to changes in ambient air temperature.

Most preferably the heating elements are electrically controlled and comprise one or a plurality of electrical resistors, for example radio resistors. These may be connected to a source of electrical supply at a voltage of between 2.5 to 75 volts and preferably between 5 and 10 volts. Accordingly, the power input is small.

An electrical or other timer may be associated with the power supply to the heating element(s).

The sensor may be a substantially cylindrical body about which one or a plurality of heating elements may be arranged in a spaced array, said heating elements being in abutment with a circumference or end of the said cylindrical body but with spaces therebetween so that ambient air can impinge readily upon the sensor. In such an arrangement a protector-cap, in accordance with standard practice, can be slid over the sensor and the heating element to protect the same in situ; so long as said cap does not impede the ready flow of air over the sensor.

Thus, in accordance with the present invention, a central heating system may comprise a plurality of radiators each provided with a thermostatically controlled valve, said heating system being characterised in that said valve is provided with an actuator in accordance with the present invetion as hereinbefore set forth. Such a system may be arranged such that different groups of radiators each form a separate heating zone. The heating requirements of each of said zones may be controlled by adjusting the heat output of the heat elements on a zone by zone basis by adjusting the design parameters of the actuator.

Embodiments of the present invention will now be described, by way of illustration only, with reference to the accompanying drawing which shows in vertical elevation a portion of a valve actuation means in accordance with the present invention is part-section.

The valve actuator (1) in accordance with the present invention is provided with a cylindrical sensor (2) terminating at its lowermost portion in the drawing, in a flanged portion (5) which is affixed by a male screw thread to an actuator body (3) formed of a plastics material. The body (3) is provided about its upper extremity with a horizontally extending protector-cap engagement means (6) in the form of a toothed wheel for inter-engagement with a corresponding portion on the protectorcap (not shown). Disposed inferior to the protector-cap engagement means (6), and upon the body (3), is an axial adjustment thread (4).

Said thread (4) is a course adjusting thread extending some four or five turns about the body (3) and adapted to inter-engage with a lower plastics moulding (not shown) in accordance with conventional arrangements. The sensor (2) is provided with an axially depending rod (7) which is caused to move axially in response to a temperature sensed by the sensor (2), said rod (7) extending downwardly with an increase in ambient temperature. Thus it will be seen that with the actuator as shown assembled on a thermostatically controlled valve an increase in ambient temperature will cause the rod (7) to move axially downwardly thereby to shut off the supply of heating fluid to the associated radiator. The position at which this occurs is adjustable by rotation of the body (3) upon the screw threads (4) thereby to move the valve actuator axially relative to the valve per se.This last movement provides manual means of adjustment of the rod (7) relative to the valve per se.

In the present invention there is additionally provided one or a plurality of heating elements (8) of a generally elongate form. These are electrical radio resistors of standard type and are connected by lead wires (9) in standard fashion in parallel. The elements (8) are disposed upon the upper face of the sensor (2) and typically may number from one to six. A heat transfer paste (10) can be used to increase apparent heat output. With the amount of heat output by said resistors being comparatively low, the heat output is just sufficient to raise the sensed temperature to achieve the desired end without interfering with the sensing abilities of the sensor (2). In a preferred form the resistors may be formed with, and or attached to the interior of the protectorcap, so that engagement of the cap with the actuator body also correstly disposes the resistors relative to the sensor.

The desired end may for example be to control the temperature in a bedroom. During daylight hours this is required to be, say, 13"C whereas in early morning and late evening the desired temperature values may be 20"-21"C. To achieve this the central heating system which is, in the ordinary course of events, thermostatically controlled by a thermostat in the living area will be set to run at its desired value. A timer may be applied to switch on the heating elements in said bedroom at 8 a.m.The result of this will be that the sensor will actuate the rod (7) to close the valve until a value of about 13"C is reached in the ambient air, at which time the amount of heat lost to the ambient air from the heating element will be sufficient to allow a slight opening of the valve in response to a slight retraction of the rod (7). Thus the bedroom zone will be held at about 13"C until the timer switches off the low power heating elements, thereby allowing the temperature of the ambient air to impinge upon the thermostats (2) without modification such that the rod (7) will be fully retracted and allow the temperature of the radiator to rise to its desired level (21"C).

The heating elements (8) have been described as being superior to the sensor; being in abutment with the upper face of the sensor. This ensures that the "heat blanket effect" is reduced to a minumum. Other arrangements are also useful. For example, an annulus bearing heating elements (8) may be provided, which annulus just fits over the sensor (2) so that the heating elements (8) contact the flange (5). Surplus heat is then directed away from the sensor (2) by virtue of the close fit of the annulus with the sensor (2).

Alternatively, the heating elements (8) may be positioned upon the lower face of the sensor (2); air circulation to the rest of the sensor (2) being prevented by physical means such as flanges etc.

It will be appreciated therefore, that a- zone by zone timed control of heating can be achieved without the use of a motorised valve or a separate temperature controller by utilising very low electrical heating values supplied by a battery or low-powered transformer. It will also be appreciated that if it is desired to change the heating requirements of a zone it is only necessary to deal with some reconnection at a central point, as opposed to more fundamental re-wiring, and re-plumbing. Thus the present invention provides a facile means whereby zone control of a central heating system can be achieved without the use of motorised valves which are centrally controlled, and hence economies of manufacture and installation can be achieved.

The present invention provides, therefore, a valve actuator as described, a thermostatically controlled valve comprising such an actuator, and a central heating system comprising such a valve.

Claims

1. A thermostatically controlled valve actuator comprising a temperature sensor, drive means associated with said sensor, a valve actuation means driven in the first mode by said drive means in response to temperature values sensed by said sensor, and a heating element juxtaposed the temperature sensor and adapted to heat the sensor and thereby to cause the valve actuation means to move into a second, at least partially closed, mode; characterised in that the actuator is so designed that in the second mode it is still responsive to changes in ambient air temperature.

2. An actuator according to Claim 1 wherein the heating elements are electrical resistors positioned in operative abutment with the sensor, and superior to a horizontal face thereof thereby to avoid "heat blanket" effects.

3. An actuator according to Claim 1 wherein the heating element(s) are electrical resistors positioned in operative abutment with the sensor, and inferior to a horizontal face thereof and wherein means is provided to prevent excess heat from the heating unit impinging upon the superior faces of the sensor.

4. A valve comprising an actuator as claimed in any one of Claims 1 to 3.

5. A valve according to Claim 4 including a valve cap incorporating a heating element or elements wherein assembly of the cap with the valve causes the heating elements to be brought into operative interconnection with the sensor.

6. A space heating system including a plurality of valves as claimed in either of claims 4 or 5.

7. A thermostatically controlled valve actuator substantially as hereinbefore set forth with reference to, and/or as illustrated in, the accompanying drawing.