Load cell

Claim 2

A unitary load cell for measuring forces applied thereto, said load cell comprising: first end constraint means; second end constraint means; stabilizer flexure means including upper and lower flexures connected between said first and second end constraints to form a parallelogram, said first and second end constraints being relatively massive in relation to said stabilizer flexure means, said stabilizer flexure means permitting relative motion between said first end constraint and said second end constraint in response to a load applied in the sensing direction; a sensing beam with a first end thereof supported by the first end constraint at a point between said flexures; load directing flexure means between said second end constraint and a second end of said sensing beam for applying equal tensile and compressive stresses along a common surface of said sensing beam while avoiding any axial loading of said sensing beam, said load directing flexure means being disposed along a centerline which intersects said sensing beam near a midpoint thereof; and means for sensing said stresses in said sensing beam, said means for sensing stresses in said beam including a multiple element resistive strain gage mounted on a top surface of said sensing beam for responding to tensile and compressive strains in said sensing beam by variation in resistance in said strain gages.

Claim 3

The load cell defined in claim 1, wherein said stabilizer flexure means includes a plurality of parallel stabilizer flexures connected at their ends to said first and second end constraints.

Claim 4

The load cell defined in claim 2, wherein said centerline along which said load directing flexure means is disposed and which intersects a midpoint of said sensing beam is equi-distant from the ends of said stabilizer flexures.

Claim 5

The load cell defined in claim 2, wherein said stabilizer flexures include a plurality of fillets near their ends which define narrow flex points for said stabilizer flexures, said fillets being equi-distant from said centerline.

Claim 6

The load cell defined in claim 2, wherein said sensing beam is essentially parallel to said stabilizer flexures.

Claim 7

The load cell defined in claim 1, which further comprises an enlarged sensing beam end constraint at one end of said sensing beam, said sensing beam end constraint having a leg thereof underlying said sensing beam which permits the load directing flexure means connected between the leg of said sensing beam end constraint and said second end constraint to apply a bending moment, as well as a force representative of the measured force, to the end of the sensing beam.

Claim 8

The load cell defined in claim 1, wherein said load directing flexure means comprises at least two neck portions for compliantly rejecting any extraneous forces normal to the applied load direction, while transmitting the applied load to the sensing beam.

Claim 9

The load cell as defined in claim 1, wherein said load directing flexure means is disposed along a centerline which extends perpendicular to said sensing beam and which intersects a midpoint of said beam.

Claim 10

A load cell comprising spaced apart first and second end constraints, a pair of spaced apart parallel stabilizer flexures connected to their ends to the end constraints to form a parallelogram, a stress sensing beam extending parallel to said stabilizer flexures and having a first end supported by one of the end constraints at a point between said stabilizer flexures and a second end, and load directing flexure means extending between the other of said end constraints and said second end of said sensing beam including an enlarged sensing beam end constraint having a leg underlying at least half of the sensing beam and a load directing flexure depending from said leg along a centerline extending perpendicular to and intersecting the midpoint of said sensing beam the lower end of which is connected to a projection extending from the other of said end constraints.

Claim 11

A load cell comprising spaced apart first and second end constraints, a pair of spaced apart parallel stabilizer flexures connected to their ends to the end constraints to form a parallelogram, a stress sensing beam extending parallel to said stabilizer flexures and having a first end supported by one of the end constraints at a point between said stabilizer flexures and a second end, and load directing flexure means extending between the other of said end constraints and said second end of said sensing beam including an enlarged sensing beam end constraint having a leg underlying at least half of the sensing beam and a load directing flexure depending from said leg along a centerline extending perpendicular to and intersecting the midpoint of said sensing beam the lower end of which is connected to a projection extending from the other of said end constraints.

Claim 12

A load cell as defined in claim 9, wherein said first end constraint is fixed and said second end constraint is movable and the load to be measured is applied to said second end constraint, and said sensing beam is supported by said fixed end constraint.

Claim 13

A load cell as defined in claim 10, wherein said centerline intersects the midpoints of said stabilizer flexures.

Claim 14

A load cell as defined in claim 11, wherein said load directing flexure means includes a plurality of flex points.

Claim 15

A load cell for measuring forces applied thereto, said load cell comprising: first end constraint means; second end constraint means; stabilizer flexure means connected between said first and second end constraints to form a parallelogram, said first and second end constraints being relatively massive in relation to said stabilizer flexure means, said stabilizer flexure means permitting relative motion between said first end constraint and said second end constraint in response to a load applied to the sensing direction; a sensing beam with a first end thereof supported by the first end constraint at a point between said stabilizer flexure means; load directing flexure means between said second end constraint and a second end of said sensing beam for applying equal tensile and compressive stresses along a common surface of said sensing beam while avoiding any axial loading of said sensing beam, said load directing flexure means being disposed along a centerline which intersects said sensing beam near a midpoint thereof, said load directing flexure means including an enlarged center portion between a pair of neck portions; an enlarged sensing beam end constraint at one end of said sensing beam, said sensing beam end constraint having a leg thereof underlying said sensing beam which permits the load directing flexure means connected between the leg of said sensing beam end constraint and said second end constraint to apply a bending moment, as well as a force representative of the measured force, to the end of the sensing beam; and means for sensing said stresses in said sensing beam.

Claim 16

A load cell for measuring forces applied thereto, said load cell comprising: first end constraint means; second end constraint means; stabilizer flexure means connected between said first and second end constraints to form a parallelogram, said first and second end constraints being relatively massive in relation to said stabilizer flexure means, said stabilizer flexure means permitting relative motion between said first end constraint and said second end constraint in response to a load applied to the sensing direction; a sensing beam with a first end thereof supported by the first end constraint at a point between said stabilizer flexure means; load directing flexure means between said second end constraint and a second end of said sensing beam for applying equal tensile and compressive stresses along a common surface of said sensing beam while avoiding any axial loading of said sensing beam, said load directing flexure means being disposed along a centerline which intersects said sensing beam near a midpoint thereof, said load directing flexure means including an enlarged center portion between a pair of neck portions; an enlarged sensing beam end constraint at one end of said sensing beam, said sensing beam end constraint having a leg thereof underlying said sensing beam which permits the load directing flexure means connected between the leg of said sensing beam end constraint and said second end constraint to apply a bending moment, as well as a force representative of the measured force, to the end of the sensing beam; and means for sensing said stresses in said sensing beam.