FR2527319A1 - Resettable thermal safety switch for heating appts. - uses spring immersed in wax to open contacts if wax melts and has external resetting button - Google Patents

Abstract

The safety cut-put uses a spring loaded contact which is normally held in the closed position against the spring force by a wax material which is solid at safe temperatures and melts when the temperature is excessive. The wax is in the tip of a tubular rod in the space in which the temperature is being monitored. The rod extends through a hole in the wall of the heated space and has the electrical contacts and switch together with a reset-indicator button in a housing at the outer end of the rod. Inside the tubular rod a solid rod couples the wax immersed spring to the switch and the reset indicator button. The heating appts. may be an instantaneous water heater or liq. fuel heater.

Description

The invention relates to a resettable safety device with a fuse for heating devices more particularly of the type of instantaneous water heaters or boilers with fluid fuel.

In devices of the aforementioned type, it is necessary to provide a certain number of safety devices the purpose of which is to automatically stop the device in the event of abnormal operation and especially in the event of accidental overheating. There are thus known overheating detectors which are placed either in the circuit of the burnt gases, or at the entry of the choke of the apparatus, to react to the heating due to any failure in the evacuation of the combustion gases, or again at various points of the heating body itself to avoid its deterioration, for example in the event of poor cooling of its skirt.

These anti-overheating safety devices are advantageously arranged to act directly on the thermoelectric ignition safety mechanism which is now routinely mounted on all modern devices. Thus we know a fuse system consisting of an electrically conductive material which melts under the action of heat, and in which the spaced ends of two conductors are embedded.

The electrically connected conductors form part of the circuit connecting the thermocouple to one electromagnet of the thermoelectric ignition safety mechanism. In the event of overheating, the fuse material melts, which electrically separates the two conductors and consequently triggers the device and stops the burners. The fuse is for this purpose, placed in close thermal contact with the combustion chamber of the appliance or placed in the area where one wishes to detect overheating, therefore its replacement is not always easy. when the fusible material melts, the contact is not always immediately interrupted, due to the proximity of the ends of the conductors and to the fact that a droplet of molten metal can possibly maintain the electrical contact above the admissible temperature.

To improve the functioning of this type of fused safety device, it has been thought to associate it with a small spring which acts on one of the conductors to release it as soon as the fusible material has started to melt and thus ensure a frank rupture of the electric contact.

These known systems - if they operate satisfactorily - have the disadvantage of not being easily resettable by the user. Indeed, once the fusible material has melted, it has flowed or accumulated in the lower part of its capsule, then resolidified due to the shutdown of the device, but obviously without having restored the electrical contact or reset its spring. The user must then replace the safety capsule in question to be able to restart the device. As during adjustments, it can happen that the device goes into safety several times, these replacements require a sufficient stock and are in any case expensive.

The invention overcomes these drawbacks in that it provides a safety device with a fuse which can be reset, which can easily be detached from the device without disconnecting it and which is safe to operate. , adaptable to any device.

The safety device according to the invention provides for filling the lower part of a detection rod intended to enter the hot zone to be monitored with a fusible material of the type of a wax in which a small precompressed spring is embedded, and with press on this fuse a connecting rod which slides inside this rod and which leads to an electrical contactor placed outside the hot zone.

The particular characteristics and advantages of the invention will appear on reading the following description of an embodiment, with reference to the accompanying drawings which represent - Figure 1: a sectional view of the resettable device
in the operating position, - Figure 2: an equivalent view of the device in posi
safety.

The figures show that the device essentially consists of a detection rod designated as a whole by the reference 1 and an electrical contactor generally designated by the reference 2.

The rod 1 is a metal tube closed at its lower part by a bottom 13 which contains a small spring 10 embedded in a fusible material 11 of the kind of a wax, this spring having the particularity of being kept precompressed by the solidified wax as illustrated in Figure 1.

A connecting rod 12 is in abutment against the upper turn of the spring 10, the lower turn of which is in abutment against the bottom 13. This rod housed in the rod 1 ends with a reset push button 20 projecting from the housing 2 of the contactor electric.

It further carries a metal strip 21 intended to cooperate with the electrical contacts (22-23) connected to the thermoelectric safety mechanism. The bar and consequently the rod 12 of which it is integral are recalled by a spring 24 bearing against the case 2 in the direction of closing the contacts (22-23). The detection rod 1 is fixed to a lower orifice of the housing 2, the assembly constituting the safety device according to the invention.

The rod is introduced into the hot zone to be detected by a well 4 provided in the wall 3 which separates the lower hot zone from the upper cold zone. Any snap-on system or pins 5 allow the rod to be held in position in the well without preventing it from being removed.

Figure 2 shows the device in the safety position. When the end of the rod 1 is in fact subjected to overheating greater than a predetermined threshold, the wax 11 becomes liquid and releases the pre-compressed spring 10 which relaxes and pushes the rod 12 against the spring 24 whose antagonistic force is obviously lower. Therefore the connection between the strip 21 and the contacts (22-23) is interrupted and the device is immediately put in safety.

The user can easily remove the detection rod from its location. Using a simple flame on the lower end of the cane, it will soften the wax 11 which had resolidified after the device had stopped; then by action on the push button 20, it can easily compress the spring 10 and place the bar 21 in the reset position; extinguishing the flame will cause the wax to solidify, which will keep the spring 10 again in the precompressed position. The device is ready for re-use in airs, a simple and quick resetting operation.

The sensitive end at the base of the rod 1 can be a removable capsule which is screwed and which contains the wax and the spring of variable characteristics, that is to say that it is easy to adapt fuse systems to the same device. of different sensitivities.

The invention which has been described on the basis of an embodiment taken by way of example, is not limited to this representation but also encompasses all the constructive variants thereof.

Claims (4)

Claims 1. Resettable safety device for devices  heater, comprising a fuse whose pitch  wise from solid to pasty or liquid  when overheating causes with the help of a  precompressed spring the breaking of an electrical contact  stick and stop the device, characterized by  the fact that the fusible element (11) which holds  in a manner known per se in the precompressed position  a spring (10) is disposed inside a  detector rod (1) introduced into the area  hot to watch, that a sliding rod (12)  inside this rod is connected to a contac  electric heater (2) outside said hot zone  and that this rod is associated with a push button  reset (20). 2. Device according to claim 1 characterized  by the fact that the detection rod (1) passes through  the wall (3) separating the hot zone from the zone  cold by a well (4) in which it is hand  held by pins (5). 3. Device according to claim 1 characterized by  the fact that the rod (12) carries a metal bar  that (21) cooperating with electrical contacts  (22, 23) connected to the thermo safety mechanism  electric. 4. Device according to claim 1 characterized by  the fact that a removable capsule containing the wax  and the spring is mounted at the end of the rod (1).