Thermistor temperature measurement for a heating element

The present invention relates to a means for fixing and taking a temperature using a thermistor on a heating element, and more particularly on an electronically regulated iron soleplate.

The means closest to that which is the subject of the present invention for taking the temperature using a thermistor consists in sealing the thermistor in an electrically insulating ceramic, to include the latter in an orifice made in the sole, and seal it with a putty or cement. This process has the drawback of being bulky and consequently of constituting, on the sole of the iron, a heat dissipating protuberance. The measurement no longer corresponds to the temperature of the sole and is only a distant and not very faithful image.

The aim of the invention therefore consists in having a means of fixing and taking a temperature which does not dissipate heat, giving a measurement; faithful and without inertia. To achieve this result, the thermistor should not be an element whose outer wall is under electrical voltage, and above all it would be necessary for said thermistor to be made integral with the metal mass by an in situ overmolding, during production by casting. in the foundry of the heating element. This in situ molding technique is commonly used for the inclusion of the shielded heating resistor, but the molding temperatures do not allow this technique to be applied to the inclusion of the thermistor. The present invention tends to artificially reproduce the thermal and mechanical advantages of such in situ molding.

To this end, it is characterized in that the thermistor is inserted into the very mass of the heating element, the orifice made to introduce the thermistor being closed using a metal part substantially of the same type as the element. heating, the adjustment of this metal part in its housing being carried out as perfectly as possible, either by tight fitting, or by metal flow, with the possible addition of a mastic. The thermistor, for its part, is characterized in that it is electrically insulated by a thin shrinkable PTFE sheath.

The temperature measurement according to the invention therefore comprises an orifice, for example rectangular in which is engaged after introduction of the thermistor, a metal part also rectangular, hereinafter referred to as the term. cap. If the heating element, which can be an iron soleplate, is made of an alloy called AS9.3, the insert is also made of AS9U3, or another aluminum alloy such as AS13, A5L.

On the lower face and the two opposite lateral faces of the orifice are respectively hollowed out the half-footprint of the thermistor and the half-footprints of the connecting wires. It is the same on the homologous faces of the stopper. As the PTFE sheath is installed by retraction, no air pocket remains between this insulation and the thermistor.

The insertion of this sub-assembly in the imprint left between the stopper and the heating element is carried out with the addition of silicone sealant. This mastic, the excess of which is removed during the assembly of the parts, fills all the gaps and interstices that may exist, for example along sharp angles. There is therefore no space that can contain air. . No solution of continuity can therefore affect thermal transmission.

So that the response time of the thermistor is very short, the half-indentation made at the bottom of the orifice is made on the shielding tube of the electric resistance.

The invention will in any case be well understood with the aid of the description which follows, relating to an exemplary embodiment. Reference will be made to the accompanying drawings in which

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<td>the</td><td>figure 1 is a section</td><td>partial transverse of a sole</td>

<td>of</td><td>iron,</td><td></td>

<td>the</td><td>figure 2 is a section</td><td>longitudinal of this sole,</td>

<td>the</td><td>figure 3 is a section</td><td>transverse of the sole after</td>

<td colspan="2">crimping the cap.</td><td></td>

The sole 1 of the iron comprises a heating resistor 2 included in a shielding tube 3. A rectangular orifice 4 has a semicircular groove 5 on the undersides 5.1 and side faces 5.2 and 5.3. The / is lower groove 5.1 / located directly on the resistor shielding tube. A slight veil of material may however remain, originating from the clearances of the constituent parts of the mold. The thermistor 6, sheathed with a retractable polytetrafluoroethylene tube 7, is placed in the bottom groove 5.1, the connection conductors 8 being housed in the lateral grooves 5.2 and 5.3. A drop of silicone sealant (such as silastene) is deposited at the bottom of the orifice 4. A stopper 9, having shapes homologous to those of the orifice 4 provided with the thermistor 6, is then slipped into the orifice 4 and in a hurry. The excess mastic is evacuated by the interstices due to the rounding of the parts which cannot have, in practice, sufficiently sharp angles. To keep the cap 9 in place, it can be forced into the orifice 4, or, if the manufacturing tolerances are too wide, crimp the metal of the sole 1 by creep at points 10 and 11.

All contacts of the thermistor to the PTFE sheath and of the PTFE sheath to the sole or plug 9 are made /. either directly, or through the silicone sealant, but in no place remains an air, water or water vapor pocket.

Of course, the invention is not limited to the example described, but covers all the minor variants within the reach of those skilled in the art. Thus the invention is not limited "to cylindrical thermistors or to in-line connections."

For other known thermistor configurations, it suffices to modify the geometry of the U orifice, of the grooves 5 and of the plug 9. The jointing mastic can be replaced by other products having sufficient thermal transmission characteristics, such as than cements.