Electricity: circuit makers and breakers – Special application – Change of inclination or of rate of motion responsive
Patent
1989-10-23
1991-07-02
Scott, J. R.
Electricity: circuit makers and breakers
Special application
Change of inclination or of rate of motion responsive
335205, H01H 3514, H01H 900
Patent
active
050287508
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an impact sensor with a magnet which is especially usable for safety devices such as an airbag in motor vehicles.
BACKGROUND INFORMATION
An acceleration sensor is, for example, described in the German Patent Publication DE 2,158,800. When an acceleration force arises, a spherical ball which in its resting position is attracted by a permanent magnet, is moved away from the magnet by overcoming the attraction force for activating a switching operation. It is disadvantageous that the switch is a microswitch with an actuating push rod loaded by a spring force. In order to overcome the disadvantages of using springs in such systems, it has also already been recommended in German Patent Publication DE-3,338,287 to use a permanent magnet system in an acceleration sensor which comprises two permanent magnets facing each other with the same sign poles and which are slideably arranged in the direction of their lengthwise axes. The permanent magnets are ring magnets within which a reed switch is arranged. With such an arrangement perhaps one can avoid using springs. However, operating conditions for the reed switch are most difficult in practice; especially bouncing of the contacts is frequent.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a magnetic impact sensor for safety devices, which functions exactly according to a structurally given characteristic, even under difficult application and switching conditions and which achieves its proper function over a long working life.
This object has been achieved by an impact sensor according to the invention, wherein the impact sensor has at least one magnet which forms with its respectively shaped pole pieces two magnetic circuits magnetically connected in parallel with each other. The magnet is, for example, a permanent magnet. The magnetic pole pieces form a housing in which a ferromagnetic ball can move in response to impact forces to respectively influence one or the other magnetic circuit to thereby open or close a reed contact of a reed relay switch which is, for example, connected in a trigger circuit for activating a passenger safety device in a vehicle. The ball moves perpendicularly to the longitudinal orientation of the reed contacts, whereby the ball, in each of its end positions positively influences the respective magnetic circuit either to short circuit one of the two parallel magnetic circuits or to positively close the reed contacts
BRIEF DESCRIPTION OF THE DRAWINGS
An example embodiment of the invention is purely schematically
FIG. 1 shows two parallel magnetic circuits formed according to the invention;
FIG. 1a shows an electric reed switch arranged to be operated by the magnetic circuits of FIG. 1;
FIG. 1b is a lengthwise section through a sensor housing enclosing a free space in which a mass in the form of a spherical ball is movable in response to acceleration;
FIG. 1c is a top view onto another free space, wherein the spherical ball is free to move in response to acceleration;
FIG. 1d shows a modification of the present sensor with a funnel shaped housing for enclosing a free space in which the spherical ball is free to move in response to acceleration, whereby the free space is shaped for using gravitational force for resetting the ball in addition to the magnetic force and for a characteristic substantially determined by the funnel shape; and
FIG. 1e is a sectional view along section line 1e--1e
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BEST MODE
OF THE INVENTION
Referring to FIG. 1 the present impact sensor comprises a permanent magnet 1 and two soft magnetic circuits 1a and 1b normally connected in parallel with each other and having different magnetic resistances or conductances 8 and 9. The magnetic circuit with the lower magnetic resistance 8 is normally closed by a spherical ferromagnetic ball 2 which normally stays in a first position when there is no impact. The ball 2 is subject to gravity and also can move in response to impact for
REFERENCES:
patent: 3459911 (1959-08-01), Fischer
patent: 3743849 (1973-07-01), Iwata
patent: 3748415 (1973-07-01), Suzuki
Laucht Horst
Spies Hans
Woehrl Alfons
Fasse W. G.
Kane, Jr. D. H.
Messerschmitt-Boelkow-Blohm GmbH
Scott J. R.
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