GB2079062A

GB2079062A - Thermal switches

Info

Publication number: GB2079062A
Application number: GB8119531A
Authority: GB
Original assignee: CALORSTAT INVESTISSEMENTS
Current assignee: CALORSTAT INVESTISSEMENTS
Priority date: 1980-07-02
Filing date: 1981-06-24
Publication date: 1982-01-13
Also published as: DE3125643A1; FR2486238B1; FR2486238A1; IT1138818B; GB2079062B; IT8122567A0

Abstract

A thermal switch for controlling a two speed fan for cooling the engine of a motor vehicle comprises a capsule 11 containing wax 13 which is sensitive to the temperature of the cooling fluid of the engine, a piston 12 movable by the wax 13, a slide 28 movable by the piston 12 and carrying two switch actuating members 30, 31, and switch means 16 having connection terminals 17, 18, 19 and two push buttons 20, 21 which are actuable at different temperatures by the actuating members 30, 31. <IMAGE>

Description

SPECIFICATION Improvements to electrical contact devices sensitive to temperature The invention relates to a staged thermocontact, that is to say an electrical contact device capable of establishing at least two different electrical circuits at successive temperature thresholds, and it relates more particularly, but not exclusively, among these staged thermocontacts, to those which are associated with the cooling installation of the engine of a motor vehicle and are adapted to switch on, at average speed and at full speed, the electric motor of a fan according to whether the temperature of the engine of the vehicle reaches a first threshold or a second threshold higher than the first.

In order to switch on the electric motor of the fan at average speed or at full speed, two different thermostatic members have hitherto been used to evaluate the two temperature thresholds. It would be preferable to use, as a control parameter, the temperature of the cooling liquid which circulates inside the radiator of the installation. This necessitates drilling, in the water tank of the radiator, as many holes as there are thermostatic members. Now it is difficult and expensive to drill such holes.

This is why, at present, only one hole is generally provided in the water tank of the radiator for the fitting of one of the thermostatic members, of the wax type, in order that this member may effectively measure the temperature of the cooling liquid, while the second thermostatic member is placed in the current of air which has passed through the radiator under the effect of the fan. Contrary to the first, therefore, the second thermostatic member is not directly sensitive to the temperature of the cooling liquid, which causes difficulties in harmonizing the adjustment of the two thermostatic members, particularly according to the latitude (outside temperature) of the place where the motor vehicle is to be used.

The object of the invention is to create a staged thermocontact which will be sensitive to a single temperature. It is also an object of the invention to create a staged thermocontact which only necessitates the drilling of a single hole in the water tank of a radiator, while being sensitive to two different thresholds of the temperature of the water circulating in this radiator.

For this purpose, the staged thermocontact according to the invention is essentially characterised in that it comprises a case to one end of which there is fixed a wax-type thermostat in such a manner that the capsule of this thermostat is situated outside the case and that the piston of the thermostat penetrates more or less into the interior of the case according to the temperature of the waxy material contained in the capsule; in that the case contains a contactor comprising an input and at least two outputs and control members associated respectively with said outputs; in that the input and the outputs of the contactor are respectively connected to connection terminals accessible outside the case; and in that a mechanism is interposed between said piston and the control members in such a manner as to actuate these members successively in the course of the penetration movement of the piston inside the case.

Thus a staged thermocontact is obtained which only comprises one wax-type thermostat, which reduces its prime cost and facilitates its adjustment.

Preferably, the body of the contactor is fixed in relation to the case and said mechanism is movable in translation inside the case, parallel to the piston of the thermostat. It is preferable to constitute the mechanism essentially by a slide guided in translation parallel to the piston of the thermostat and urged by a spring towards this piston. According to an advantageous construction, the body of the contactor is approximately parallelepipedic and the slide encases this body in such a manner as to be guided by this.

When the mechanism consists of a slide it is an advantage to cause it to carry two ramps cooperating respectively with the control members of the contactor, the assembly being such that one of the ramps acts on one of the control members before the other ramp acts on the other control member, in the course of the outward movement of the piston of the wax-type thermostat. According to a particularly simple mode of embodiment, the control members of the contactor consist of pushbuttons carried by one face of the body which is parallel to the piston of the thermostatic member and the ramps carried by the slide are oblique in relation to the axis of the piston.In order to facilitate the adjustment of the temperature thresholds, each ramp may consist of a resilient strip, the inclination of which, at the level of the corresponding pushbutton, is adjustable, particularly by means of a screw. Finally, it may be an advantage to make the resilient strips in one piece with a common bar serving to fix them to the slide.

The invention will now be described in more detail with reference to the accompanying drawings.

Figure 1 shows the motor serving to drive the fan of a cooling installation for the engine of a motor vehicle as well as the feed circuit of this motor.

Figure 2 shows, in longitudinal section, a staged thermocontact which is associated with the feed circuit of Fig. 1 and which is constructed in accordance with one mode of embodiment of the invention.

Figure 3 illustrates a detail of this thermostat in section on the line Ill-Ill of Fig. 2.

A cooling installation for the engine of a motor vehicle comprises a liquid circuit passing through a radiator. This radiator is cooled, if necessary, by a fan which is driven by an electric motor 1. This motor 1 is fed by a source of current (battery) 2, by means of a contact 3 coupled to the ignition contact of the engine of the vehicle and either a contact 4 with a resistor 5 connected in series or a contact 6 without the resistor 5 connected in series, the two contacts 4 and 6 being actuated depending on the temperature at least at one point of the cooling installation. It would also be possible to replace the contact 4 by a group of contacts adapted to be closed at different temperatures and to connect resistors of different values in series.In any case, when the contact 4 (or when one of the contacts of the above-mentioned group) is closed, the motor 1 drives the fan at an intermediate speed.

The object of the invention is to cause the contacts 4 and 6 to be actuated by means of a single thermostatic member or wax-type thermostat 7, in such a manner as to constitute a staged thermocontact.

As Figs. 2 and 3 show, this staged thermocontact 8 comprises a case in two parts 9 and 10, to one end of which there is fixed the wax-type thermostat 7 in such a manner that the capsule 11 of this thermostat 7 is situated outside the case 9, 10 and the piston 1 2 of the thermostat penetrates more or less into the interior of the case 9, 10 according to the temperature of the waxy material 1 3 contained in the capsule 11. A diaphragm 14 is interposed between the material 1 3 and the piston 1 2 which is accommodated in a guide 1 5. In accordance with the French Patent 78 07432/2.420.124, the effective stroke of the piston 1 2 is preferably at most equal to 1 1 times its diameter.

The case 9, 10 contains a contactor 1 6 comprising an input 17, two outputs 1 8 and 1 9 (see also Fig. 1) and control members or push-buttons 20 and 21 (Fig. 3) associated respectively with said outputs 18 and 19. The contactor 1 6 in-cludes the two contacts 4 and 6 of Fig. 1 with which there are associated respectively the outputs 18 and 1 9 and the push-buttons 20 and 21. The input 17 and the outputs 1 8 and 1 9 consist of conductors which pass through the upper portion 9 of the case 9, 10 in such a manner as to form connection terminals outside the case.

Finally, a mechanism which will be described below is interposed between the piston 12 and the push-buttons 20, 21 in such a manner as to actuate these push-buttons 20,21 successively in the course of the raising of the piston 12.

The lower portion 10 of the case is fixed to the upper portion 9 thereof for example by means of crimping 22. The capsule 11 of the thermostat 7 is itself fixed, by crimping 23 for example, to the lower portion 10 of the case.

In the vicinity of the thermostat 7, the lower portion 10 is equipped on the one hand with a threaded bearing surface 24 which enables it to be fixed by screwing in the wall 25 of the water tank of the radiator and on the other hand with a hexagon 26 adapted to receive a spanner. The guide 1 5 passes through the lower portion 10 of the case at the level of the threaded bearing surface 24 with the interposition of a seal 27.

The body of the conductor 16, which is approximately parallelepipedic in shape, is fixed in relation to the case 9, 1 0. A slide 28 encases this body in such a manner as to be guided in translation by the latter, parallel to the axis of translation (vertical in Fig. 2) of the piston 1 2. The slide 28 is urged towards the piston 1 2 by a spring 29 bearing against the body of the contactor 1 6.

Laterally, the slide 28 carries two partially oblique ramps or resilient strips 30 and 31 (see also Fig. 3), the positions and/or the shapes of which are such that the strip 30 acts first on the push-button 20, then the strip 31 acts on the push-button 21, when the piston 1 2 rises. According to the form of embodiment illustrated, the push-buttons 20 and 21 project to the same height on a lateral face of the body of the contactor 1 6 and the strips 30 and 31 have different and adjustable inclinations, preferably each by means of a screw such as 32 passing through the slide 28. The two strips 30 and 31 may be made integral with a bar 33, this being fixed to the slide 28 by means of screws or rivets 34.

Facing the regulating screws 32, the upper portion 9 of the case 9, 10 comprises an access opening which is normally closed by a stopper 35.

Thus a thermocontact 8 is obtained, the operation of which is as follows. Before placing it in position on a water tank, the operating threshold of the contacts is adjusted by inclining the strips 30, 31 more or less by means of the screws 32. Then the thermocontact is placed in position, screwing it by means of the threaded bearing surface 24, the capsule 11 containing the waxy material 1 3 thus being licked by the cooling water circulating in the water tank.

When the temperature of this water is lower than a first threshold, the piston 1 2 is sufficiently driven into the guide 1 5 for the two strips 30, 31 carried by the slide 28 not to touch the push-buttons 20, 21. The contacts 4 and 6 of Fig. 1 are then both open and the motor 1 of the fan is not excited. The fan is therefore stopped.

When the temperature rises beyond a first threshold but remains lower than a second threshold, the piston 1 2 raises the slide 28 sufficiently for the strip 30 to push in the push-button 20, which corresponds to the closing of the contact 4 of Fig. 1, the contact 6 remaining open. The motor 1 is therefore fed by means of the resistor 5 and drives the fan at a moderate speed.

When the temperature rises beyond the second threshold, the piston 1 2 raises the slide 28 sufficiently for the strip 31 to push in the push-button 21, which corresponds to the closing of the contact 6 of Fig. 1. The motor 1 is thus fed directly by the current source 2.

The same operations take place in reverse when the temperature of the water again drops below the second threshold, then the first threshold.

Instead of effecting the individual adjustment of the two temperature thresholds by means of the screws 32, it would be possible first to adjust the ramps 30 and 31 in such a manner that they determine a predetermined spacing between the temperature thresholds corresponding to the tripping of the pushbuttons 20 and 21, then to adjust only the first temperature threshold by straining (or controlled local driving in) of the capsule 11 of the thermostat 7. The screws 32 and the stopper 35 are then eliminated.

Claims

1. A staged thermocontact, adapted, in particular, to switch on, at moderate speed and at full speed, the electric motor of the fan of a cooling installation for the engine of a motor vehicle according to whether the temperature of this latter engine reaches and exceeds a first threshold or a second threshold higher than the first, characterised in that it comprises a case (9, 1 0) to one end of which there is fixed a wax-type thermostat (7) in such a manner that the capsule (11) of this thermostat (7) is situated outside the case (9, 10) and the piston (12) of the thermostat (7) penetrates more or less into the interior of the case (9, 10) according to the temperature of the waxy material (1 3) contained in the capsule (11); in that the case (9, 10) contains a contact (16) comprising one input (17) and at least two outputs (1 8, 1 9) and control members (20, 21) associated respectively with said outputs (18, 19); in that the input (17) and the outputs (18, 19) of the contactor (16) are connected respectively to connection terminals accessible at the outside of the case (9,1 0); and in that a mechanism (28, 30, 31) is interposed between the said piston (12) and the control members (20, 21) in such a manner as to actuate these members (20, 21) successively in the course of the movement of penetration of the piston (12) into the interior of the case (9, 10).

2. A thermocontact as claimed in Claim 1, characterised in that the body of the contactor (16) is fixed in relation to the case (9, 10) and in that said mechanism (28, 30, 31) is movable in translation inside the case (9, 10) parallel to the piston (12) of the thermostat (7).

3. A thermocontact as claimed in one of the Claims 1 and 2, characterised in that the mechanism consists essentially of a slide (28) guided in translation parallel to the piston (12) of the thermostat (7) and urged by a spring (29) towards this piston (12).

4. A thermocontact as claimed in all the Claims 3 and 4, characterised in that the body of the contactor (16) is approximately parallelepipedic and in that the slide (28) encases this body in such a manner as to be guided by this.

5. A thermocontact as claimed in one of the Claims 3 and 4, characterised in that the slide (28) carries two ramps (30, 31) cooperating respectively with the control members (20, 21) of the contactor (16), the assembly being such that one of the ramps (30) acts on one of the control members (20) before the other ramp (31) acts on the other control member (31) in the course of the outward movement of the piston (12).

6. A thermocontact as claimed in Claim 5, characterised in that the control members of the contactor (16) consist of push-buttons (20, 21) carried by one face of the body which is parallel to the piston (12) and in that the ramps (30, 31) carried by the slide (28) are oblique in relation to the axis of the piston (12).

7. A thermocontact as claimed in Claim 6, characterised in that each ramp consists of a resilient strip (30, 31), the inclination of which, at the level of the corresponding pushbutton (20, 21) is adjustable, particularly by means of a screw (32).

8. A thermocontact as claimed in Claim 7, characterised in that the resilient strips (30, 31) are made integral with a common bar (33) serving to fix them to the slide (28).

9. A staged thermocontact, adapted, in particular, to switch on, at moderate speed and at full speed, the electric motor of the fan of a cooling installation for the engine of a motor vehicle according to whether the temperature of this latter engine reaches and exceeds a first threshold or a second threshold higher than the first, constructed and adapted to operate substantially as hereinbefore described with reference to and as shown in the accompanying drawings.