IL114563A - Thermostat with safety device - Google Patents

Description

THERMOSTAT WITH SAFETY DEVICE The present invention concerns a probe thermostat destined for example to regulate the temperature of water contained inside an electric water heater.

Thermostats are cyclically acting thermo-sensitive command devices, destined to maintain the temperature between two particular values under normal operation conditions and in which a regulation by the user can be provided.

Probe thermostats are electro-mechanical systems of regulation of temperature containing on one hand a metal tube having a high dilatation coefficient (copper, brass) inside of which is located a metal stem of low dilatation coefficient (invar), and on the other hand, an electric contact which commands the current to be sent into the heating resistance, actuated by the differential dilatation of the two metals which constitute the probe .

Known probe thermostats destined for electric water heaters operating under pressure, generally incorporate a safety device enabling to cut off the supply of electric current destined for heating from the enclosure in which the probe is located in case of inopportune rise of the temperature within that enclosure.

Thermostats of this type are known, which are described for instance in the Invention Patent 2 579 G13 belonging to the applicant, which more particularly include a convexing disc which deforms under the effect of a predetermined temperature to actuate a slide the movement of which provokes interruption of the heating circuit in the enclosure of which the thermostat probe is located.

This type of thermostat transmits the heat of the water contained in the enclosure by conduction to the metallic support of the body of the latter which houses the convexing disc. The latter must be designed to deform when the temperature, at the tip of the probe, inside the water heater, reaches a critical threshold, in order to cut off the electric circuits.

To obtain perfect operation, it is necessary to provide a convexing disc which deforms at a temperature quite below the critical threshold because of the distance which separates the tip of the probe from the support of the thermostat fixed against the enclosure.

The improvements object of the present invention aim at enabling the execution of a safety device which acts on the tip of the probe, hence on the heart of the system to be regulated.

For this purpose, the thermostat according to the present invention includes in proximity .to the free end of the probe and between the tube and the stem a safety device consisting of a spring made of a memory alloy in a manner that it acts by means of an intermediate piece on a slide the movement of which provokes the opening of electric interruptors whenever an inopportune rise of temperature occurs within the enclosure in which thesaid probe is immersed.

The attached drawing, given as example, would enable better comprehension of the invention, the characteristics offered thereby and the advantages which it is likely to provide : Fig. 1 is a blown up perspective view illustrating the safety device according to the present invention.

Fig. 2 is a cross section representing a probe thermostat equipped with safety device in operating position.

Fig. 3 is a cross section similar to that of Fig. 2, but illustrating the electric interruptors opened as a result of the dilatation of the safety device following a inopportune rise of temperature .

Fig. 1. to 3 show a probe thermostat 1 incorporating a baseplate 2 made of plastic material which carries on the one hand the command mechanism of the supply circuit of a heating system and on the other hand a metallic probe 3.

The probe 3 incorporates a tube 3a having a high dilatation coefficient which is subjected to a metallic vat 3b having two diametrically opposed legs 3c and 3d which insert in the grooves 2a and 2b made in the baseplate 2.

The leg 3c has a vertical extension 3e the base of which is adjacent to two wings 3f and 3g pointing in the same direction as the extension 3e. The wings 3f and 3g are flattened inside the groove 2a in a manner to hold the vat 3b in axial position with respect to the baseplate 2.

Similarly, the leg 3d includes two parallel claws 3h and 3i separated by a central trough 3j to enable thesaid claws to plunge into the groove 2b to constitute the second fixation of the vat 3b with respect to the baseplate 2.

Inside the tube 3a is located a metal stem 4 having a low dilatation coefficient one end of which is set to the tube 3a, while the other end co-operates with a regulation organ 5. It is also observed that the extension 3e of the leg 3c passes above the baseplate 2 to serve as articulation for one of the ends of an insulating amplification lever 6a of an electric contact 6 which is actuated by the stem 4 following temperature variations taking place within the enclosure in which the probe 3 is located.

The latter incorporates at its free end and between the tube 3a and the stem 4 a safety device 7. This device is composed of a spring 7a made of memory alloy in a manner that it is traversed by the stem 4. The spring 7a comes to lean on a disc 7b which in turn is traversed by the stem 4 and which is disposed in proximity to the setting of the tube 3a with the stem 4. As a variant, it can be provided that spring 7a be made to lean directly against the conical part 3k of the tube 3a without interfering thereby with the proper functioning of the safety device 7.

A cylindrical intermediate piece 7c is introduced in the remaining portion of the probe .3 between the tube 3a and the metallic stem 4. The intermediate piece 7c is slightly longer than the tube 3a and emerges in the space delimited by the vat 3b. The intermediate piece 7c leans against the spring 7a and remains free to move vertically inside the probe 3.

Above the intermediate piece 7c there is a slide 8 made of insulating material such as plastic, traversed by the stem 4 and able to move vertically back and forth inside an appropriate opening 2c made in the baseplate 2. The slide 8 incorporates a central part 8a extending by two diametrically opposed wings 8b, 8c each of which is integral with a stop end 8d, 8e extending vertically and parallel to the axis of movement of the slide 8.

One of the wings and more particularly the one referenced 8c incorporates in proximity to the stop end 8e a reset finger 8f which proceeds towards the exterior of the housing 9 shown in mixed lines (fig. 2 and 3).

Above the stop ends 8d and 8e are located elastic metal blades 10a and 11a pertaining respectively to the safety interruptors 10 and 11 of the thermostat 1. Each of the safety interruptors 10 and 11 is mounted on the electric current supply phases of the resistance of a water heater or similar apparatus, not shown. The extremities of the elastic blades 10a and 11a carry a mobile contact 10b and lib apt to co-operate with a fixed contact 10c and 11c which is integral part of connection terminals 12 of which only one is shown in fig. 2 and 3.

The mode of functioning of the thermostat 1 results from the above explanations. It is understood that the contact 6 is controlled by the amplifying lever 6a in function of the relative dilatation of the tube 3a with respect to the stem 4. Regulation of the thermostat 1 is done by the button 5. The latter may carry an index moving over a scale provided on the housing 9. If for any reason the temperature of the installation rises abnormally, beyond the minimal thermal threshold of the spring 7a, the latter dilates and moves vertically towards the top of the intermediate piece 7c inside the tube 3a. The movement towards the top of the intermediate piece 7c drags in the same direction the slide 8 of plastic material which, by means of the stop ends 8d and 8e, raises the elastic blades 10a and 11a to open the safety interruptors 10 and 11 thus assuring the interruption of the current in the heating installation.

Thus it is enough to press on the reset finger 8f to force the spring 7a in its initial position so that the safety interruptors 1Θ and 11 come in contact. The return of the spring 7a to its initial position can only be assured when the temperature at the tip of the probe 3a, that is inside the water heater, drops back to below the critical threshold.

The reset finger 8f may be eliminated to avoid the use of thermostats which underwent an inopportune rise of temperature.

Moreover, it should be understood that the above description is only given as example and that it does not in any way limit the scope of the invention and any replacement of the described execution details by any other equivalents shall not be considered as going beyond that scope.

Claims (6)

C L A I M S

1. Probe thermostat of the type that includes an electro-mechanical temperature regulation system provided with a probe consisting of a metal tube having high dilatation coefficient inside of which is placed a stem of metal of low dilatation coefficient and at least one electric safety interruptor controlling the electric current used in the heating resistance, characterised by that the probe (3) incorporates at its free end and between the tube (3a) and the stem (4) a safety device (7) consisting of a spring (7a) made of memory alloy in a manner that it acts by means of an intermediate piece (7c) on a slide (8) the movement of which provokes the opening of the electric interruptors (1G and 11) in case of a rise of temperature exceeding that of the minimal thermal threshold of the spring (7a) .

2. Probe thermostat according to claim 1, characterised by that the spring (7a) leans on a perforated disc (7b) disposed in proximity to the setting which 'enables fixation of the tube (3a) with the stem (4).

3. Probe thermostat according to claim 1, characterised by that the spring (7a) leans directly on the conical part (3k) of the tube (3a) of the probe (3).

4. Probe thermostat according to claim 1, characterised by that the intermediate piece (7c) passes over the vat (3b) to come in contact with the slide ( 8 ) .

5. Probe thermostat according to claim 1, characterised by that the slide (8) has a central part (8a) integral with two diametrically opposed wings (8b) and (8c), each extending with a vertical stop end (8d) and (8e).

6. Probe thermostat according to claim 5, characterised by that the slide (8) has on its wing (8c) and in proximity to its stop end (8e) a reset finger (8f) extending vertically according to the axis of movement of thesaid slide. , Sanford T. Colb & Co. C: 22461