Patent ID: 6166339
Filing Date: 2000-12-26
Classification: H01H

Abstract:
A safety switch intended to be fitted in an electrical circuit of a motor vehicle, said switch comprising:a hollow body for fixing to the motor vehicle and having a cavity with a transverse base wall and a transverse covering wall;an inertial mass in the form of a body of revolution capable of moving radially between the base wall and the covering wall, between a centred position and an infinite number of eccentric positions;a system of electrical contacts situated to a side of the base wall remote from the cavity and comprising a movable contact member capable of establishing first and second circuit states of the switch;a push rod associated with the movable contact member and extending centrally through the base wall to engage the inertial mass;opposing resilient means which tend to urge the movable contact member and the push rod to the position corresponding to the second state of the circuit;the arrangement being such that when the inertial mass is in the centred position, it retains the push rod held against the force of its opposing resilient means and enables the movable contact member to stay in the first state of the circuit, while when the inertial mass has moved to an eccentric position, the push rod is free to move under the force of its resilient opposing means, moving the movable contact member to the position corresponding to the second state; anda reset push button, accessible from the outside of the switch, which faces the covering wall outside the cavity, and which comprises a plurality of projections extending towards the base wall through the covering wall and having inclined active surfaces, which diverge towards the base wall; andresilient biasing means which urge the reset push button to a rest position in which it is remote from the covering wall;the arrangement being such that when the push button is in the rest position, its projections do not engage the inertial mass, while when the inertial mass is in an eccentric position and the push button is pressed against the force of its resilient biasing means, the projections engage the inertial mass with a cam action and move it to the centred position,wherein the inertial mass is in the form of a body of revolution about an axis at right angles to the base wall and the covering wall, and has a flat base surface engaged with the aforesaid base wall and a flat head surface having a peripheral edge which is engagable with a cam action by the projections of the push button,the base surface has a central depression shaped substantially as a flattened cone for housing the push rod and for maintaining the push rod in the position corresponding to the first state of the circuit, and an annular groove concentric with the depression into which, when the inertial mass is in an eccentric position, the push rod enters to reach a position corresponding to the second state of the circuit, the central depression and the annular groove being separated from each other by a crest;the annular groove is bounded by a radially inner annular side which has an annular bevel adjacent to the said annular crest to constitute a ramp adapted to cooperate in the manner of a cam with an end of the push rod against the force of its opposing resilient means to repel the push rod to a position such as to allow the annular crest to pass beyond said push rod when the mass is being brought back to the central position and to allow the push rod to enter the central depression; anddisengagement means are provided, which interconnect the push button and the push rod in an arrangement such that, when the internal mass is in an eccentric position with the end of the push rod inserted in the annular groove, a pressure on the push button moves, in a first time, the push rod to a partially withdrawn position in which, when the projections of the push button engage the inertial mass to move the latter to the centered position, the said annular bevel repels the push rod, in a second time, allowing the annular crest to pass beyond the latter.