GB2175672A

GB2175672A - Thermostatic gas valve

Info

Publication number: GB2175672A
Application number: GB08605201A
Authority: GB
Inventors: Peter Derek Roberts
Original assignee: Concentric Controls Ltd
Current assignee: Concentric Controls Ltd
Priority date: 1985-05-22
Filing date: 1986-03-03
Publication date: 1986-12-03
Also published as: GB2175672B; GB8512971D0

Abstract

A thermostat for a gas valve is calibrated by moving the expansible element 22 in and out of a sleeve 30 32. The sleeve 32 is rotationally free but axially captive in the body of the valve, at least during the calibration step. Hence the element moves 24 axially when the sleeve is rotated. When set to the required position, the element 22 is angularly fixed and this prevents axial movement and prevents the calibrated position being disturbed. The fixing is achieved by making the element angularly fast with the sleeve so that if it turns, both turn together, or by fixing the sleeve 32 against rotation relative to the body relying upon alternative means such as the stiffness of the capilliary tube connected to the expansible element, to prevent angular movement of the element in the fixed sleeve. The sleeve may be crimped to the element 22 to prevent relative movement. Alternatively, fixing may be effected with adhesive or cement. <IMAGE>

Description

SPECIFICATION Thermostatic gas valve It is known to mount the expansible element of a thermostatic valve in the wall of the valve by complementary engaged screw threads.

The valve is calibrated for example to cut off gas flow when a particular temperature is sensed, by screwing the element in or out, and then locking it in the desired position with a lock nut. The problem with this is simply that tightening the lock nut tends to move the expansive element with the lock nut relative to the female screw-threaded aperture in the valve wall and hence displaces the expansive element axially so that the element is moved from what was intended to be the calibrated position. It is also found that the extent to which the element moves during tightening of the lock nut depends to some extent upon the individual operator performing the calibration.

The object of the invention is to provide an improved design capable of calibration in a simpler fashion.

According to the invention the expansible element of a thermostatic valve is located in a sleeve by complementary engaged screw threads, the sleeve is rotatable in the wall of the valve but axially captive therein, and the expansible element is relatively angularly fast.

By these means, calibration is effected by turning the sleeve and the setting is fixed by making the sleeve rotationally fast by any desired means.

The sleeve can be made relatively stiff to turn for example by means of a trapped 0ring or by the ring being fixed to the wall of the valve by a peened portion creating a frictional resistance to turning movement. Then, the expansible element never has to be turned although it is displaced axially inwardly or outwardly by turning the sleeve. There is little tendency for the expansible element to be displaced from the calibrated position during the fixing of the parts which effectively renders the two rotationally fast which means that if the expansible element is turned, it turns with the sleeve and the calibrated position is unaltered.

Various possibilities exist for rendering the sleeve and expansible element fast with one another, including the possibility of using a lock nut. In this case however tightening the lock nut may simply tend to turn the parts (expansible element and sleeve) as a unit with out affecting the calibration. However it is preferred to dispense with the lock nut and alternative possibilities for connecting the parts together include crimping them or glueing or cementing them.

Moreover, there are two possibilities for the fixing step. One possibility is to arrange for the expansible element to be inherently limited in its turning capacity, in which case fixing the sleeve against rotation will have the desired effect. A second possibility is to fix the sleeve and expansible element together and a third possibility is to fix the sleeve to the body and the sleeve to the expansible element.

The invention is more particularly described with reference to the accompanying drawing in which the sole figure is a sectional elevation showing the essential parts of a thermostatic gas valve according to the invention.

The valve comprises a chamber defined by a body part 10, and an outlet 12 from the chamber is controlled by a valve plug 14 carried by one end of a beam 16 which is urged by spring 18 in a valve opening direction, and is contacted by end 20 of the expansive element 22 to close the valve when a particular temperature is reached. The temperature sensor (not shown) is connected by the capillary tube 24 here shown as looped so as to pass over a lug 26 provided for the purpose and held to the lug by a springy sheet metal clamp 28 which is located as close as possible to the expansive element 22 so as to provide the required angular fastness of the element 22.It will be appreciated that if the clip 28 were provided for example in the vicinity of the arrow 30, the flexibility of the pipe would allow the angularity of the expan- sive element to be changed, and that is undesirable.

The element 22 is provided with male screw threads complementary to and engaged with female screw threads in sleeve 32. The sleeve is rotationally free but axially captive in the body 10, for example by having a shoulder 34 externally of the valve, conveniently of hexagonal shape to facilitate spanner turning, and possibly with an O-Ring or other seal 36 between the head 34 and the body 10. The opposite end of the sleeve may be spun, peened or otherwise engaged with the body for the axial captiveness. However alternative means may be provided for example circlips, spring washers or the like having the same effect of maintaining the sleeve axially captive but rotationally free.

To calibrate the valve, the sensor is placed in a suitable temperature environment and the sleeve is rotated until the valve 14 is in appropriate condition. For example the valve may be required to be (just) closed at one temperature and just opening at the slightly lower temperature. When the necessary adjustment has been completed to calibrate the valve, it is preferred to crimp the sleeve 32 to the expansive element for example by a series of indentations 36. This ensures that if the sleeve were to turn, it would only be with the expansive element and hence the calibrated position would be unaltered. However, it may be possible to get a satisfactory result by fixing the position of the sleeve relative to the body for example by an appropriate adhesive or cement provided between adjacent parts, or similarly with such adhesive or cement provided between the screw threads.

The crimping illustrated is, as mentioned, the present preferred means for holding the calibration separate, and for this purpose (as illustrated) the collar 32 is provided with a relatively thin tubular extension in which the crimping indentations are made.

Claims

1. A thermostatic gas valve having the expansible element located in a sleeve with complementary engaged screwthreads, and with the sleeve rotatable but axially fast in the wall of the valve, in which the thermostat is calibrated and subsequently the expansible element is made relatively angularly fast.

2. A valve as claimed in Claim 1 in which the element is made relatively angularly fast by fixing the said element to the sleeve.

3. A valve as claimed in Claim 2 in which the sleeve is crimped to the element.

4. A valve as claimed in Claim 2 wherein the sleeve is rendered angularly fast to the element by adhesive or cement.

5. A valve as claimed in Claim 1 in which the element is made relatively angularly fast by fixing the sleeve against rotation.

6. A valve as claimed in Claim 5 in which the sleeve is fixed by adhesive or cement.

7. A valve as claimed in any preceding claim in which the expansible element is connected to a capillary tube which is clamped to the wall of the valve at a position close to the expansible element.

8. A thermostatic gas valve substantially as described with reference to the accompanying drawings.