Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1997-09-10
1998-12-08
Gaffin, Jeffrey A.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
441 93, 441 94, 222 5, H01H 3518
Patent
active
058474730
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/FR96/00341, filed Mar. 10, 1995 which designated the U.S.
The present invention relates to the field of the sensing of immersion in a liquid medium.
More specifically, the invention relates to an electrical contactor placed between an electrical power source and a receiver device, the contactor closing the electrical circuit only if it is immersed to a predetermined depth and for a predetermined period of time in a defined liquid medium. A preferred application of a contactor according to the invention is in the field of the inflation of life-jackets.
Electrical contactors for underwater work, such as for example the actuation of a pyrotechnic cable cutter, are already known, for example from U.S. Pat. No. 3,739,673. The contactor described in that patent comprises, in particular, a rigid cup which can move axially with respect to the body of the contactor under the effect of the pressure and thus bring two blades initially separated by a partially deformable spacer into contact with each other. Such contactors are entirely satisfactory for high-pressure fields and in particular for the pressures generated by an underwater explosion. However, such contactors are not reliable under shallow-immersion conditions, in particular because of the rubbing of the seal positioned between the moveable cup and the rest of the body of the contactor.
Contactors have therefore been sought which operate under shallow-immersion conditions and therefore under a small change in pressure with respect to atmospheric pressure. Such a contactor has, for example, been proposed in Patent FR-B-2,569,305 or in its corresponding Patent EP-B-0,174,891. According to this solution, the contactor does not form an independent element but is integrated into a pyrotechnic device. Actuation of the electrical circuit is not due to the mechanical deformation of a component but is caused by a sudden change in conductance associated with the ingress of the liquid into the electrical casing through a very low-porosity membrane set to allow the liquid to pass through only for continuous immersion.
Although such a contactor is, in theory, perfectly reliable, in practice its operation depends on its position at the moment of immersion and it is not totally reliable.
For various applications such as, for example, the inflation of life-jackets, those skilled in the art are therefore always searching for an electrical contactor having a very high operating reliability under shallow-immersion conditions.
The object of the present invention is specifically to provide such a contactor.
The invention therefore relates to an electrical contactor which can be actuated by immersion in a liquid medium and comprises a casing which includes a liquid-tight sealed compartment which contains an electronic circuit interposed between a DC power source and a power outlet, the said circuit comprising at least one connection component which connects the DC source to the outlet only if a sufficient voltage is applied to it, the said compartment having an immersion-sensitive wall with an external face which is in direct contact with the liquid in which the contactor is immersed, characterized in that: free ends of which lie on the external face of the immersion wall and which thus constitute a variable resistor whose resistance depends on the nature of the medium with which the said wall is in contact; free ends of which are connected to an element which is sensitive to the pressure applied to it and at least part of which lies on the external face of the said immersion wall so as to make the said electrodes sensitive to the pressure of the medium with which the said wall is in contact; microporous membrane which is permeable to gases and impermeable to the said liquid medium; connection component only if each pair of electrodes has identified an occurrence of a threshold, predetermined in respect of its operating parameters, being crossed.
Thus, when the power outlet is connected to a receiving device
REFERENCES:
patent: 3739673 (1973-06-01), Temple
Anfosso Roger
Garde Franck
Gaffin Jeffrey A.
Pyromeca S.A.
Zura Peter
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