Electricity: circuit makers and breakers – Special application – Change of inclination or of rate of motion responsive
Patent
1981-03-13
1983-02-01
Grimley, A. T.
Electricity: circuit makers and breakers
Special application
Change of inclination or of rate of motion responsive
200 6145M, 200 6152, H01H 3502
Patent
active
043717632
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to an inertia switch device for opening or closing electrical contacts in response to movement of the device.
BACKGROUND ART
Devices of this kind are known in which an inertia mass held in an operative position by a spring or a magnet is freed by an acceleration or a deceleration of a predetermined intensity to effect the opening or closing of the electrical contacts. Such devices are usually mounted in a vehicle in a position such that they respond to acceleration or deceleration in a horizontal direction, so that if the vehicle is subject to an impact from the front, the side, or the rear, the electrical contacts are operated. It is a disadvantage of such devices that they may not be capable of being easily reset to their original, unoperated, condition.
An object of this invention is to provide an inertia switch device which mitigates this disadvantage.
DISCLOSURE OF THE INVENTION
According to one aspect of the present invention an inertia switch device comprises an inertia mass which is movable from a rest position when the device is subjected to an applied acceleration or deceleration in a horizontal plane, a first electrical contact movable between a first stable position in which it engages a second electrical contact and a second stable position in which it no longer engages the second electrical contact, support means having a bifurcated portion for carrying a bifurcated portion of the first electrical contact, operating means engageable by the inertia mass on movement of the inertia mass as a result of the applied acceleration or deceleration exceeding a threshold value, to move the first electrical contact from the first to the second stable position, or vice versa, the operating means comprising a first limb which is struck by the inertia mass when the threshold value is exceeded and a second limb having a bifurcated portion which is pivotally mounted on the support means, resilient biassing means which lie within the bifurcated portions and connect the first electrical contact and the second limb so as to bias the first electrical contact towards the first or second stable position depending on the position of the second limb, and resetting means comprising an operating member movable to operate the resilient biassing means and thereby return the first electrical contact to its original stable position.
Conveniently the operating member may be arranged to actuate a linkage which bears against the resilient biassing means to return the first electrical contact to its original stable position.
Preferably the operating member is arranged to actuate a cranked lever which bears against the resilient biassing means to return the first electrical contact to its original stable position.
The resilient biassing means may comprise a helical tension spring hooked at opposite ends into respective holes in the first electrical contact and the second limb of the operating means.
The inertia mass, the electrical contacts, the operating means and the resilient biassing means may be accommodated in a housing and the operating member may extend out of the housing by an amount which provides a visual indication as to whether or not the operating means have been struck by the inertia mass.
It is also a disadvantage of some inertia switch devices that they do not necessarily respond and operate the electrical contacts if the device is subjected to a rotary motion such as that occurring when the vehicle rolls about its longitudinal axis.
Furthermore, where such devices are designed to operate the electrical contacts in response to rotary motion of the vehicle, this may be accompanied by a tendency to operate the electrical contacts in response to a relatively low force applied in a vertical direction. This is disadvantageous in that the device may respond to forces applied in a vertical direction such as are caused by bumps in a road along which the vehicle is travelling.
According to another aspect of the present invention an inertia switch device comp
REFERENCES:
patent: 2206067 (1940-07-01), Waltamath
Crick David W.
Jackman Peter R.
First Inertia Switch Limited
Ginsburg Morris
Grimley A. T.
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