Load cell and seat occupant weight sensing system
First Claim
1. A load cell having an axis, and comprising:
- two force input members for receiving force applied to said load cell, a first spring and a second spring, and force sensing means responsive to said force applied to said load cell by producing a force signal, and wherein;
each said spring comprises;
(1) a first part linked with one of said force input members for movement therewith, (2) a second part linked with the other of said force input members for movement therewith, and (3) a uniting part unitary with said first and second parts, and said uniting parts are offset from each other in the direction of said axis, whereby said force signal indicates the axial component of said force applied to said load cell and is minimally affected by components of said force applied to said load cell having directions perpendicular to said axis.
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Abstract
A load cell particularly useful for a seat occupant weight sensing system includes a liquid filled chamber and a pressure sensor providing an electric signal indicating the pressure in the liquid. Four load cells supporting a seat provide four signals that are added to determine the weight of the seat occupant. The load cell comprises two flanged conical springs stressed to provide preload. One of the springs also forms part of the surface of the liquid filled chamber. The two springs operate in concert to resist side forces and moments. The load cell is responsive to both compressive and tensile forces while being substantially unaffected by lateral forces and moments. A seat belt tension sensor may be included to measure seat belt tension. Preferred manufacturing methods provide low cost,
26 Citations
22 Claims
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1. A load cell having an axis, and comprising:
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two force input members for receiving force applied to said load cell, a first spring and a second spring, and force sensing means responsive to said force applied to said load cell by producing a force signal, and wherein;
each said spring comprises;
(1) a first part linked with one of said force input members for movement therewith, (2) a second part linked with the other of said force input members for movement therewith, and (3) a uniting part unitary with said first and second parts, andsaid uniting parts are offset from each other in the direction of said axis, whereby said force signal indicates the axial component of said force applied to said load cell and is minimally affected by components of said force applied to said load cell having directions perpendicular to said axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A seat occupant weight sensing system comprising:
- (1) a seat, (2) a load cell. and (3) a processing unit for reckoning weight applied to said seat; and
wherein;
said seat is adapted for receiving force from an occupant of said seat and applying force derived from said received force to said load cell, said load cell comprises;
(1) two force input members for receiving force applied to said load cell, (2) a spring, and (3) force sensing means for producing a force signal;
said spring comprises;
(1) an outer cylindrical flange linked with one of said force input members for movement therewith, (2) an inner cylindrical flange linked with the other of said force input members for movement therewith, and (3) a uniting component unitary with said flanges; and
whereinsaid force signal is responsive to said force applied to said load cell, and said processing unit is adapted to consider said force signal when said reckoning weight applied to said seat. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
- (1) a seat, (2) a load cell. and (3) a processing unit for reckoning weight applied to said seat; and
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21. A method of making a load cell comprising a spring and a force input member, the method comprising:
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(1) pressing a surface of said spring against a surface of a said force input member, while (2) performing a weld fixing the position of said spring relative to said force input member, (3) stressing said spring to form a gap between said surfaces, (4) injecting said liquid through an opening into said gap, and (5) sealing said opening;
wherebythe effects of temperature on the performance of said load cell are accurately controlled.
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22. A load cell having an axis, and comprising:
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force input members for receiving force applied to said load cell, a spring, a link linking said spring to a said force input member, and force sensing means responsive to said force applied to said load cell by producing a force signal; and
wherein;
said spring comprises;
a first part linked by said link with one of said force input members for movement therewith, a second part linked with another of said force input members for movement therewith, and a uniting part unitary with said first and second parts; and
whereinsaid link is made of material having a larger thermal expansion coefficient than the thermal expansion coefficient of the material of which said spring is made, whereby the variation of said force signal with temperature is controlled.
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Specification