GB2074317A - Thermostat Element - Google Patents

Abstract

A thermostat element (1) has a housing comprising a bottom (2) and a top (3), which also acts as a guide for a thrust pin (5) movable by a diaphragm (4) in dependence on the thermal expansion of a wax filling (9). An incompressible body (7) is arranged in the bottom (2) and serves to shape the filling (9) into a thin film. By virtue of the relatively large area of the thin film of expandible filling and, its small volume the speed of response of the thermostat element is rapid. <IMAGE>

Description

SPECIFICATION Thermostat Element This invention relates to a thermostat element including an expandible substance, located in an essentially rigid housing, which acts via a diaphragm on a thrust pin.

In the case of the thermostat elements of this type in common use the expandible substance is enclosed in a rigid cup-shaped capsule. Here the expandible substance assumes the form of a solid cylinder whose surface is relatively small compared with its volume. Thus, combined with the relatively unfavourable thermal conductivity of the usual expandible substances, means that these known thermostat elements therefore exhibit a sluggish time response or low response speed so that these known thermostat elements are particularly unsuitable for use in sanitary cold and hot water mixing valves.

To overcome these deficiencies it is known practice, from West German Published Application, DE-OS 24 41 224, to locate the expandible substance in a displacement body which is bounded by an inner and an outer cylindrical shell engaging in one another coaxially and forming a hollow cylinder and in the transition area with the diaphragm is interspersed with the tubes forming passages which connect the space inside and outside the hollow body. This design may improve the speed of response but manufacture and filling of the housing is difficult and very costly.

According to the present invention, there is provided a thermostat element including an expandible substance, located in an essentially rigid housing which acts via a diaphragm on a thrust pin, wherein an incompressible displacement body is arranged in the housing such that the expandible substance is in the form of a relatively thin film between the housing walls and the displacement body.

The expandible substance, e.g. wax, is thus located with an optimum distribution in relation to the surface of the thermostat housing so that the fast speed of response of the thermostat necessary for sanitary cold and hot water mixing valves can be achieved. The cheaply manufactured design of the thermostat housing, the filling with the expandible substance and the closure of the capsule, for example by flanging, by methods in common use can be retained.

The displacement body can be produced at low cost by pressure die casting from aluminium or zinc alloys or from a plastics material with low coefficient of thermal expansion.

The invention thus provides a thermostat element with a high speed of response which can be manufactured by simple means.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 shows a longitudinal section through a thermostat element according to the present invention, and Fig. 2 shows a section taken through line Il-Il of Fig. 1.

The thermostat element 1 consists of a housing comprising a cup-shaped bottom 2 and a top 3 incorporating a concentric guide and support for a thrust pin 5, a disc 6 and a diaphragm 4. In the substantially cylindrical bottom 2 is located an incompressible displacement body 7 with spacer ribs 8 which are arranged with slight clearance relative to the walls of bottom 2. There are four spacer ribs 8 which are formed on the cylindrical surface of displacement body 7 and project beyond the two circular end faces of body 7 in each case by an extent equivalent to a predetermined distance from the housing so that the displacement body 7 is located both axially and radially in a central position in the housing. The thin walled interspace between housing and displacement body 7 is filled with an expandible substance 9, for example, a wax.After pouring in the expandible substance 9 and inserting displacement body 7 in the bottom 2 and inserting the diaphragm 4 in the top 3, the bottom 2 and top 3 are brought together and are flanged to one another to form a seal by means of a flange projection 10 on bottom 2. If now temperature changes occur in the area surrounding the thermostat element thus formed, these are transmitted directly to the expandible substance 9 on account of the large surface area presented by displacement body 7 which is large in relation to its volume and thus produces a change in volume of the expandible substance which accordingly deflects diaphragm 4 and thus displaces thrust pin 5.

In such cases the diaphragm 4 is made of rubber or a similar material and its radially outer edge also acts as a seal between top 3 and bottom 2 in the region of flange projection 10. It is also possible of course to use a metal diaphragm instead of the rubber diaphragm and for the top 3 to be welded to the bottom 2.

The displacement body 7 can be made by pressure die casting from zinc or aluminium alloys, or from a plastics material with a low coefficient of thermal expansion.

Whereas the displacement body 7 has been described as having four spacer ribs, alternatively three or more than four may be employed. Instead of having spacers provided on the body 7 itself, the body 7 could be located in a central position relative to the housing by projections formed in the housing.

Claims

1. A thermostat element including an expandible substance, located in an essentially rigid housing, which acts via a diaphragm on a thrust pin, wherein an incompressible displacement body is arranged in the housing such that the expandible substance is in the form of a relatively thin film between the housing walls and the displacement body.

2. A thermostat element as claimed in claim 1, wherein the displacement body is located in a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Thermostat Element This invention relates to a thermostat element including an expandible substance, located in an essentially rigid housing, which acts via a diaphragm on a thrust pin. In the case of the thermostat elements of this type in common use the expandible substance is enclosed in a rigid cup-shaped capsule. Here the expandible substance assumes the form of a solid cylinder whose surface is relatively small compared with its volume. Thus, combined with the relatively unfavourable thermal conductivity of the usual expandible substances, means that these known thermostat elements therefore exhibit a sluggish time response or low response speed so that these known thermostat elements are particularly unsuitable for use in sanitary cold and hot water mixing valves. To overcome these deficiencies it is known practice, from West German Published Application, DE-OS 24 41 224, to locate the expandible substance in a displacement body which is bounded by an inner and an outer cylindrical shell engaging in one another coaxially and forming a hollow cylinder and in the transition area with the diaphragm is interspersed with the tubes forming passages which connect the space inside and outside the hollow body. This design may improve the speed of response but manufacture and filling of the housing is difficult and very costly. According to the present invention, there is provided a thermostat element including an expandible substance, located in an essentially rigid housing which acts via a diaphragm on a thrust pin, wherein an incompressible displacement body is arranged in the housing such that the expandible substance is in the form of a relatively thin film between the housing walls and the displacement body. The expandible substance, e.g. wax, is thus located with an optimum distribution in relation to the surface of the thermostat housing so that the fast speed of response of the thermostat necessary for sanitary cold and hot water mixing valves can be achieved. The cheaply manufactured design of the thermostat housing, the filling with the expandible substance and the closure of the capsule, for example by flanging, by methods in common use can be retained. The displacement body can be produced at low cost by pressure die casting from aluminium or zinc alloys or from a plastics material with low coefficient of thermal expansion. The invention thus provides a thermostat element with a high speed of response which can be manufactured by simple means. An embodiment of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 shows a longitudinal section through a thermostat element according to the present invention, and Fig. 2 shows a section taken through line Il-Il of Fig. 1. The thermostat element 1 consists of a housing comprising a cup-shaped bottom 2 and a top 3 incorporating a concentric guide and support for a thrust pin 5, a disc 6 and a diaphragm 4. In the substantially cylindrical bottom 2 is located an incompressible displacement body 7 with spacer ribs 8 which are arranged with slight clearance relative to the walls of bottom 2. There are four spacer ribs 8 which are formed on the cylindrical surface of displacement body 7 and project beyond the two circular end faces of body 7 in each case by an extent equivalent to a predetermined distance from the housing so that the displacement body 7 is located both axially and radially in a central position in the housing. The thin walled interspace between housing and displacement body 7 is filled with an expandible substance 9, for example, a wax.After pouring in the expandible substance 9 and inserting displacement body 7 in the bottom 2 and inserting the diaphragm 4 in the top 3, the bottom 2 and top 3 are brought together and are flanged to one another to form a seal by means of a flange projection 10 on bottom 2. If now temperature changes occur in the area surrounding the thermostat element thus formed, these are transmitted directly to the expandible substance 9 on account of the large surface area presented by displacement body 7 which is large in relation to its volume and thus produces a change in volume of the expandible substance which accordingly deflects diaphragm 4 and thus displaces thrust pin 5. In such cases the diaphragm 4 is made of rubber or a similar material and its radially outer edge also acts as a seal between top 3 and bottom 2 in the region of flange projection 10. It is also possible of course to use a metal diaphragm instead of the rubber diaphragm and for the top 3 to be welded to the bottom 2. The displacement body 7 can be made by pressure die casting from zinc or aluminium alloys, or from a plastics material with a low coefficient of thermal expansion. Whereas the displacement body 7 has been described as having four spacer ribs, alternatively three or more than four may be employed. Instead of having spacers provided on the body 7 itself, the body 7 could be located in a central position relative to the housing by projections formed in the housing. Claims

1. A thermostat element including an expandible substance, located in an essentially rigid housing, which acts via a diaphragm on a thrust pin, wherein an incompressible displacement body is arranged in the housing such that the expandible substance is in the form of a relatively thin film between the housing walls and the displacement body.

2. A thermostat element as claimed in claim 1, wherein the displacement body is located in a central position in the housing by means of spacers.

3. A thermostat element as claimed in claim 2, wherein spacer ribs are formed on the displacement body.

4. A thermostat element as claimed in claim 3, wherein the displacement body is substantially cylindrical in form and three or more spacer ribs are formed on the cylindrical surface of the displacement body, which spacer ribs project beyond the circular end faces of displacement body to an extent equivalent to a predetermined distance from housing, which spacer ribs maintain the displacement body axially and radially at a predetermined distance from housing.

5. A thermostat element as claimed in any one of claims 1 to 4, wherein the displacement body is made from an aluminium or zinc alloy.

6. A thermostat element as claimed in any one of claims 1 to 4, wherein the displacement body is made from a plastics material with a low coefficient of thermal expansion.

7. A thermostat element substantially as herein described with reference to and as illustrated in the accompanying drawings.