GB1597963A

GB1597963A - Thermostats

Info

Publication number: GB1597963A
Application number: GB721677A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-02-21
Filing date: 1977-02-21
Publication date: 1981-09-16

Description

(54) IMPROVEMENTS IN THERMOSTATS (71) I, JOHN CRAWSHAW TAYLOR, a British subject of 9, Homefield Park, Ballasalla Castletown, Isle of Man, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be particularly described in and by the following statement: This invention relates to a thermostat and more particularly though not exclusively to a thermostat to be positioned in a vehicle cooling system, preferably a wall of a motor vehicle radiator and arranged to control a radiator cooling fan.

It is known to provide (see for example co-pending Application 14431/76 (Serial No. 1 580 786) a thermostat of a particular construction and having a housing having a cylindrical portion with a smooth exterior which is adapted to be inserted in an aperture in a vehicle radiator wall and retained therein by means of a deformable bush compressed between the cylindrical portion and the edge of the aperture.

It is a standard practice in Europe to provide thermostats in vehicle radiators, the thermostat housing having an external thread and being screwed into a threaded aperture in the radiator wall. This has required an expensive housing for the thermostat specifically designed for use in a threaded aperture, the housing being formed by turning a solid brass bar. Such arrangement is much more expensive than for example the housing of 14431/76 (Serial No. 1 580 786) which may be formed by a simple pressing operation.

The present invention provides a thermostat including a housing, a pair of co-operable electrical contacts and a temperature responsive switch actuator both mounted within the housing, the housing including a pressed cylindrical part and an externally threaded sleeve formed from pressed sheet metal secured on the exterior of the cylindrical part.

The housing of a thermostat in accordance with the invention may be secured in a threaded aperture of a vehicle radiator wall, but is much less expensive to produce than the known housing referred to above turned from solid brass bar.

Further an existing theremostat housing which may have been suitable for securing in a radiator wall by for example a deformable bush as described above, can, in accordance with the invention, be adapted for securing in a threaded aperture in a vehicle radiator wall by virtue of securing the threaded sleeve to the exterior of said cylindrical part.

Preferably the housing is formed of pressed steel, (preferably stainless steel; other metals could if desired be employed) and the threaded sleeve is formed of brass for ease of forming the thread. Preferably the sleeve is formed from brass sheet; as an alternative another metal e.g. stainless steel could be employed for the sleeve. The sleeve may be attached to the housing by any suitable means and in particular may be soldered or welded to the pressed cylindrical part. As preferred however the sleeve is bonded to the cylindrical part with an adhesive. This has the advantage that the sleeve may be secured to a thermostat housing already containing the electrical contacts without affecting the temperature calibration of the thermostat.

A problem which arises with thremostats positioned within vehicle radiator walls is that of providing an efficient seal to prevent leakage of liquid from the radiator. In a preferred arrangement, the threaded sleeve has a closed end portion fitting over an end of the cylindrical part so that even if the securing of the sleeve to the cylindrical part becomes insecure the sleeve will provide a water tight seal.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a cross-sectional view of a first embodiment of a housing for a thermostat in accordance with the present invention; Figure 2 is a cross-sectional view of a second embodiment of a thremostat housing; and Figure 3 is a third and preferred embodi ment of a housing of a thermostat according to the present invention.

Referring to Figure 1 there is shown a housing for a thermostat. The construction of the electrical contacts and the actuator, which are both mounted within the housing, is not shown, it being understood that various constructions could be employed including that disclosed in copending Application 14431076 (Serial No.

1 580 786). The housing comprises a pressed steel member comprising two cylindrical parts 2, 4, part 2 being of smaller diameter than part 4 and there being a stepped portion 6 there between. A brass sleeve 8 is dimensioned to closely fit over cylindrical part 2. Sleeve 8 is formed by pressing from sheet material. Sleeve 8 comprises a threaded portion 10, being of 22 mm external diameter and having a 1.5 mm pitch thread. A flange 12 at the end of the sleeve abuts stepped portion 6. Sleeve 8 is secured to part 2 by a layer of adhesive 14 therebetween. Adhesive 14 is of a type which will not be attacked by chemicals with which it will come into contact in use, for example ethylene glycol, a constituent of anti-freeze. A preferred adhesive is an anaerobic adhesive manufactured by Lock-Tight U.K. Limited and comprising a primer "Lock-Qwik Primer T" and "Lock-Tight Retaining Compound 640".

An advantage of providing flange 12 is that upon screwing the thermostat housing into a threaded aperture 16 in a vehicle radiator wall 18, the pressure of the seal between the housing and the wall is taken by the relatively thick flange 12 and there is in consequence little danger of deformation of the relatively thin pressed housing.

However the adhesive 14 must provide a continuous seal around the circumference of the cylindrical part; otherwise there will be a danger of leakage in regions not covered with adhesive.

In the arrangement shown in Figure 2, similar parts to those shown in Figure 1 are indicated by the same numerals. The arrangement of Figure 2 differs from Figure 1 in that no flange is provided at the end of the threaded sleeve 8. Thus when the thremostat housing is screwed into a radiator wall the pressure of the seal is taken by stepped portion 6 of the steel pressed part. An advantage of this arrangement is that the adhesive 14 need not be continuous over the periphery of cylindrical part 2 since a seal will be provided direct between stepped portion 6 of the pressed housing and the radiator wall and thus any water penetrating through the adhesive will not be able to escape from the radiator.

In the preferred arrangement shown in Figure 3, similar parts to those shown in Figure 1 are again indicated by the same reference numerals. In the arrangement of Figure 3, the threaded sleeve 8 again has a flange 12 at its end adjacent to stepped portion 6 and has in addition at its other end a closing wall 20 which extends over the base 22 of cylindrical part 2. Wall 20 is made to conform to the generally concave shape of the base 22 of part 2 and the gap between the base 22 and wall 20 is made as small as possible to maximise heat conduction between wall 20 and the base 22, thereby ensuring the electrical contacts in the thermostat housing are properly responsive to the temperature of the vehicle radiator. Adhesive 14 is contained in the gap between wall 20 and the base 22 and may include metal particles to improve the thermal conduction.

As with the embodiment shown in Figure 1 a seal between the housing and the vehicle radiator wall is provided by flange 12. A particular advantage of the arrangement shown in Figure 3 is that should the adhesive bonding between the threaded sleeve and the pressed part loosen, this will not cause leakage of liquid from the radiator since the threaded sleeve will act as a plug in the aperture in the vehicle radiator wall. This also has the advantage that the adhesive will not be exposed to liquid in the vehicle radiator and may therefore be of any type suitable to bond the sleeve to the pressed housing.

The concave shape of base 22 of the base of the housing arises in consequence of the preferred form of thermostat employed, i.e. that disclosed and claimed in application No. 14431/76 (Serial No. 1 580 786): a thermostat including an electrical switch and a switch actuator comprising a bimetallic disc movable between oppositely dished configurations with a snap action, a stop engaging with one edge portion of the disc, said stop being adjustable in position for accurately locating the disc, a switch contact operating member with a generally diametrically opposite disc edge portion, a fulcrum engaging with said disc and about which said disc moves during its snap action, the fulcrum being disposed intermediate said disc edge portions and at or near the center of the disc, the base of the thermostat housing having a frusto-conical portion so that an edge of the frustoconical portion provides the fulcrum.

WHAT WE CLAIM IS: 1. A thermostat including a housing, a pair of co-operable electrical contacts and a temperature responsive switch actuator both mounted within the housing, the housing including a pressed cylindrical part and an externally threaded sleeve formed from pressed sheet metal secured on the exterior of the cylindrical part.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ment of a housing of a thermostat according to the present invention. Referring to Figure 1 there is shown a housing for a thermostat. The construction of the electrical contacts and the actuator, which are both mounted within the housing, is not shown, it being understood that various constructions could be employed including that disclosed in copending Application 14431076 (Serial No.

2. A thermostat as claimed in claim 1

wherein said cylindrical part is formed as pressed steel.

3. A thermostat as claimed in claim 1 or 2 wherein said housing comprises two coaxial cylindrical parts, said above mentioned cylindrical part having a smaller diameter than the other cylindrical part.

4. A thermostat as claimed in any preceding claim wherein the sleeve is formed from brass.

5. A thermostat as claimed in any preceding claim wherein said sleeve is secured to said cylindrical part by means of an adhesive bond.

6. A thermostat as claimed in claim 5 wherein said adhesive comprises an anaerobic adhesive.

7. A thermostat as claimed in claim 5 or 6 wherein said adhesive provides a continuous circumferential seal around said cylindrical part of said housing.

8. A thermostat as claimed in any preceding claim wherein said sleeve includes an annular flange at one end of said sleeve for providing a seal when said thermostat is secured in a member having a theaded bore.

9. A thermostat as claimed in any preceding claim wherein said sleeve has a closed end portion closely fitting over an end of said cylindrical part.

10. A thermostat as claimed in claim 9 wherein a thermally conductive adhesive bond is provided between said sleeve closed end portion and the end of said cylindrical part.

wherein said bond is provided by an adhes

11. A thermostat as claimed in claim 10 ive containing thermally conductive particles.

12. A thermostat as claimed in claim 9 wherein said sleeve closed end portion closely conforms to a concave shape of said cylindrical part end, said cylindrical part end having a quadrilateral cross-section.

13. A thermostat as claimed in any preceding claim employing the invention so far as is claimed in any claim in the complete specification of application No.

14431/76.

14. A thermostat substantially as described with reference to Figure 1 of the accompanying drawings.

15. A thermostat substantially as described with reference to Figure 2 of the accompanying drawings.

16. A thermostat substantially as desscribed with reference to Figure 3 of the accompanying drawings.

17. A thermostat as claimed in any preceding claim wherein during the assembly of the thermostat, said electrical contacts and said switch actuator are assembled in the thermostat and said sleeve is subsequently secured to said cylindrical part by means of an adhesive band.

18. A thremostat as claimed in any preceding claim the thermostat being mounted in a wall of a part of a vehicle cooling system.