Variable capacitor crash sensor

Claim 2

In a passenger conveyance the combination comprising an inflatable cushion, electrically operated actuator means for inflating said cushion; variable capacitance impact sensor means mounted on said vehicle and comprising members which are relatively displaceable upon impact of said vehicle to vary the capacitance of the sensor means in proportion to the relative displacement of said members; means for converting the capacitance of said sensor means to a signal proportional to the relative velocity of said members; means responsive to said signal for operating said actuator means an interval of time after the relative velocity of said members exceeds a predetermined velocity.

Claim 3

In a passenger conveyance the combination comprising an inflatable cushion, electrically operated actuator means for inflating said cushion; variable capacitance impact sensor means mounted on said vehicle and comprising members which are relatively displaceable upon impact of said vehicle to vary the capacitance of the sensor means in proportion to the relative displacement of said members; means for converting the capacitance of said sensor means to a signal proportional to the relative velocity of said members; means responsive to said signal for operating said actuator means an interval of time after the relative velocity of said members exceeds a predetermined velocity.

Claim 4

In a passenger conveyance the combination comprising an inflatable cushion, electrically operated actuator means for inflating said cushion; variable capacitance impact sensor means mounted on said vehicle and comprising members which are relatively displaceable upon impact of said vehicle to vary the capacitance of the sensor means in proportion to the relative displacement of said members; means for converting the capacitance of said sensor means to a signal proportional to the relative velocity of said members; means responsive to said signal for operating said actuator means an interval of time after the relative velocity of said members exceeds a predetermined velocity.

Claim 5

In an automotive vehicle the combination comprising, a source of pressure fluid, an inflatable cushion, electrically operated actuator means for communicating the cushion with said source, a bumper impact bar receptive to impact forces, energy absorbing means supporting the impact bar on the vehicle frame; variable capacitance impact sensor means mounted between said impact bar and said vehicle frame, said sensor means exhibiting a change in capacitance in response to a change in the relative distance between the impact bar and the vehicle frame; means responsive to the capacitance of said sensor means for developing a signal proportional to the relative velocity of said impact bar and said vehicle frame; means responsive to said signal for operating said actuator means an interval of time after the said relative velocity exceeds a predetermined velocity.

Claim 6

In an automotive vehicle the combination comprising, a source of pressure fluid, an inflatable cushion, electrically operated actuator means for communicating the cushion with said source, a bumper impact bar receptive to impact forces, energy absorbing means supporting the impact bar on the vehicle frame; variable capacitance impact sensor means mounted between said impact bar and said vehicle frame, said sensor means exhibiting a change in capacitance in response to a change in the relative distance between the impact bar and the vehicle frame; means responsive to the capacitance of said sensor means for developing a signal proportional to the relative velocity of said impact bar and said vehicle frame; means responsive to said signal for operating said actuator means an interval of time after the said relative velocity exceeds a predetermined velocity.

Claim 7

The combination defined in claim 2 wherein said sensor means comprises an outer cylindrical member mounted to said frAme and having an axis, an inner cylindrical member supported within said outer member in axial alignment therewith and electrically insulated therefrom, means for connecting said inner member to a source of potential, a cylindrical plunger mounted at one end to said impact bar, bearing means mounting the other end of said plunger for axial movement between said inner and outer members, said inner member and said plunger forming a first capacitor, said inner and outer members forming a second capacitor electrically in parallel with said first capacitor the total capacitance of which increases as the distance between the impact bar and the vehicle frame decreases.

Claim 8

The combination defined in claim 3 further comprising a normally open switch supported by said outer member and including an armature normally biased to the open position and movable to the closed position in response to relative movement of said plunger and said outer member, means connecting said switch in series with said actuator means to inhibit operation of said actuator means until said switch is closed.

Claim 9

In an automotive vehicle the combination comprising, a source of pressure fluid, an inflatable cushion, electrically operated actuator means for communicating the cushion with said source, a bumper impact bar receptive to impact forces, energy absorbing means supporting the impact bar on the vehicle frame; variable capacitance impact sensor means mounted between said impact bar and said vehicle frame, said sensor means exhibiting a change in capacitance in response to a change in the relative distance between the impact bar and the vehicle frame; multivibrator means including said sensor means and producing a substantially rectangular output wave whose ratio of on-time to off-time is proportional to the capacitance of said sensor means; means for averaging the output of said multivibrator means to produce a dc signal proportional to the capacitance of the sensor means; differentiator means responsive to said dc signal to provide a signal proportional to the velocity of impact; means responsive to the output of said differentiator means for operating said actuator means an interval of time after the velocity of impact exceeds a predetermined velocity.

Claim 10

In an automotive vehicle the combination comprising, a source of pressure fluid, an inflatable cushion, electrically operated actuator means for communicating the cushion with said source, a bumper impact bar receptive to impact forces, energy absorbing means supporting the impact bar on the vehicle frame; variable capacitance impact sensor means mounted between said impact bar and said vehicle frame, said sensor means exhibiting a change in capacitance in response to a change in the relative distance between the impact bar and the vehicle frame; multivibrator means including said sensor means and producing a substantially rectangular output wave whose ratio of on-time to off-time is proportional to the capacitance of said sensor means; means for averaging the output of said multivibrator means to produce a dc signal proportional to the capacitance of the sensor means; differentiator means responsive to said dc signal to provide a signal proportional to the velocity of impact; means responsive to the output of said differentiator means for operating said actuator means an interval of time after the velocity of impact exceeds a predetermined velocity.

Claim 11

In an automotive vehicle the combination comprising, a source of pressure fluid, an inflatable cushion, electrically operable actuator means for communicating the cushion with said source, a bumper impact bar receptive to impact forces, energy absorbing means supporting the impact bar on the vehicle frame, a plurality of electro-mechanical sensor means mounted between said impact bar and said vehicle, each sensor means forming a capacitor and each capacitor exhibiting a change of capacitance as the relative distance between the impact bar and the vehicle frame changes; variable duty cycle multivibrator means including each of said capacitors and producing a substantially rectangular wave whose ration of on-time to off-time is proportional to the capacitance of the capacitor exhibiting the largest capacitance; means for averaging the output of said multivibrator means to produce a dc signal proportional to the position of said impact bar relative to said vehicle frame; differentiator means for differentiating said dc signal to provide a signal proportional to the velocity of said impact bar relative to said vehicle frame; integrator means connected to said differentiator means and operative to develop a control voltage when the velocity of said impact bar relative to said vehicle frame exceeds a predetermined velocity, said control voltage attaining a predetermined magnitude in a time interval dependent on the impact velocity; voltage detector means for operating said actuator means in response to said control voltage attaining said predetermined magnitude.

Claim 12

In an automotive vehicle the combination comprising, a source of pressure fluid, an inflatable cushion, electrically operable actuator means for communicating the cushion with said source, a bumper impact bar receptive to impact forces, energy absorbing means supporting the impact bar on the vehicle frame, a plurality of electro-mechanical sensor means mounted between said impact bar and said vehicle, each sensor means forming a capacitor and each capacitor exhibiting a change of capacitance as the relative distance between the impact bar and the vehicle frame changes; variable duty cycle multivibrator means including each of said capacitors and producing a substantially rectangular wave whose ration of on-time to off-time is proportional to the capacitance of the capacitor exhibiting the largest capacitance; means for averaging the output of said multivibrator means to produce a dc signal proportional to the position of said impact bar relative to said vehicle frame; differentiator means for differentiating said dc signal to provide a signal proportional to the velocity of said impact bar relative to said vehicle frame; integrator means connected to said differentiator means and operative to develop a control voltage when the velocity of said impact bar relative to said vehicle frame exceeds a predetermined velocity, said control voltage attaining a predetermined magnitude in a time interval dependent on the impact velocity; voltage detector means for operating said actuator means in response to said control voltage attaining said predetermined magnitude.