Weighing scales – Structural installation – Furniture or room fixture
Reexamination Certificate
2000-06-30
2001-04-17
Gibson, Randy W. (Department: 2859)
Weighing scales
Structural installation
Furniture or room fixture
C177S2100EM, C073S862626, C361S287000, C361S292000, C180S273000, C280S735000, C340S667000, C340S562000, C324S660000
Reexamination Certificate
active
06218632
ABSTRACT:
BACKGROUND OF THE INVENTION
It is desirable to determine the weight of a vehicle occupant of a vehicle seat. Upon the occurrence of a crash event, for example, an occupant restraint device may utilize an individual's weight to determine an appropriate amount of restraining force. One common type of weight sensor which may be mounted to a vehicle seat is a strain gauge sensor. Various other types of weight sensing devices have been proposed.
U.S. Pat. No. 2,968,031 to Higa discloses an electronic micrometer which measures rotational displacement by monitoring a tuned resonant circuit. The displacement of a movable member is detected by detuning the resonant circuit with a three element capacitive pick-off. An output voltage has a magnitude which is a function of both the magnitude of the input signal and the amount of displacement. In order to obtain accurate results, this circuit requires balancing the resonant circuit to the zero condition prior to each measurement.
U.S. Pat. No. 5,804,885 to Cadwell discloses a displacement measuring device which includes a variable capacitor. The variable capacitor provides a DC output signal having an amplitude which is proportional to displacement. The output signal is fed back to the variable capacitor to automatically re-balance the electrodes which form the capacitor. The feedback provides a measure of the force being transduced.
U.S. Pat. No. 4,384,496 to Gladwin similarly discloses a variable capacitor for measuring a load applied to a housing. The variable capacitor is connected within the housing and provides an output signal having an amplitude which varies according to the movement of the housing.
SUMMARY OF THE INVENTION
The present invention is directed to a weight sensing apparatus for a vehicle seat. The weight sensing apparatus comprises a differential capacitor including a first capacitor and a second capacitor. The first capacitor includes first and second opposed plate assemblies. The second capacitor includes a third plate assembly and the second plate assembly. The second plate assembly is interposed between the first and third plate assemblies and axially adjoins the first capacitor to the second capacitor. Each plate assembly includes a conductive plate. The conductive plate of the first plate assembly extends parallel to and is fixed relative to the conductive plate of the third plate assembly. The conductive plate of the second plate assembly extends parallel to and is moveable in an axial direction relative to the first and third plate assemblies in response to a load being applied to the vehicle seat. Each plate assembly has a plurality of elongated members which extend in a substantially axial direction. Each elongated member is at least partially formed from a conductive member which is electrically connected to the conductive plate of the respective plate assembly. The plurality of elongated members of the first and third plate assemblies extends toward said second plate assembly. The second plate assembly has a plurality of elongated members extending toward the first plate assembly and a plurality of elongated members extending toward the third plate assembly. The plurality of elongated members extending from the second plate assembly terminates in gaps created by the elongated members of the first and third plate assemblies. The plurality of elongated members of the second plate assembly is movable relative to the plurality of elongated members of the first and third plate assemblies. The weight sensing apparatus further comprises a source of alternating electrical energy, which provides electrical energy to the differential capacitor, and an output circuit electrically connected with the differential capacitor, which provides an output signal indicative of the load applied to the weight sensing apparatus. The output signal of the output circuit varies as a function of the capacitance of both the first capacitor and the second capacitor.
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Feedback Control of Dynamic Systems, Franklin et al., Addison-Wesley Publishing Co., Reading,MA pp. 26-31, Mar. 1985.
Fullerton Michael G.
Lemense Thomas J.
McCarthy Michael C.
Gibson Randy W.
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Inc.
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