Accelerometer strain isolator

An accelerometer suspension apparatus comprising:

• a means for measuring acceleration applied along an input axis;
• a means for supporting the acceleration measuring means;
• a means interconnected between the supporting means and the acceleration measuring means for suspending the acceleration measuring means from the supporting means for limited motion in a plane substantially perpendicular to the input axis, the suspending means comprising:
• a plurality of first flexure means each having spaced apart interconnecting means for interconnecting to the supporting means,
• a plurality of second flexure means each having spaced apart interconnecting means for interconnecting to the acceleration measuring means, and
• means for interconnecting each of the plurality of first flexure means with a respective one of the plurality of second flexure means at a position substantially intermediate between the respective spaced apart interconnecting means.

A suspension structure comprising:

• a substrate having substantially parallel and spaced apart top and bottom surfaces;
• an inner frame member formed in the substrate;
• an outer frame member formed in the substrate, the outer frame member spaced away from and substantially surrounding the inner frame member;
• a separation slot formed between the inner and outer frame members, the separation slot being defined by an outer side wall of the inner frame member and an inner side wall of the outer frame member spaced away from the outer side wall of the inner frame member and being contiguous therewith;
• a plurality of beams formed in the substrate within the separation slot at spaced positions around an outer periphery of the inner frame member, each of the beams being interconnected between the inner and outer frame members;
• an inner slot formed in the outer periphery of the inner frame member and adjacent to but spaced away from the outer side wall thereof, the inner slot having first and second spaced apart ends positioned on opposite sides of a first beam substantially equidistantly therefrom;
• and
• an outer slot formed in an inner periphery of the outer frame member and adjacent to but spaced away from the inner side wall, the outer slot having first and second spaced apart ends positioned on opposite sides of the first beam substantially equidistantly therefrom.

An apparatus comprising:

• a silicon substrate formed with substantially planar and parallel opposing offset upper and lower surfaces;
• an outer frame structure formed in the substrate;
• an inner frame structure formed in the substrate, the inner frame structure being at least partially surrounded by the outer frame structure and separated therefrom by a space;
• and
• a plurality of isolators formed in the substrate and extending between the upper and lower surfaces thereof, each of the isolators comprising a pair of inner flexures and a pair of outer flexures spaced away therefrom, proximal ends of each of the inner and outer flexures being interconnected, distal ends of the inner flexures being interconnected with the inner frame structure, and distal ends of the outer flexures being interconnected with the outer frame structure.

An accelerometer comprising:

• a silicon substrate having substantially parallel and spaced apart top and bottom surfaces;
• an accelerometer sensor mechanism having a inner sensor frame and proof mass formed in the substrate, the proof mass suspended pendulum fashion within the inner sensor frame by one or more flexures, and two mechanical resonators interconnected in push-pull fashion between the proof mass and the inner sensor frame;
• an outer frame formed in the substrate and substantially surrounding and spaced away from the accelerometer sensor mechanism;
• and
• a plurality of strain-isolating suspension members positioned in the space between the accelerometer sensor mechanism and the outer frame and coupled between the accelerometer sensor mechanism and the outer frame, pairs of the strain-isolating suspension members positioned on opposite sides of the accelerometer sensor mechanism, each of the strain-isolating suspension members being formed in the substrate and comprising:
• a first thin and elongated flexure having first and second ends coupled to an inner wall of the outer frame, and
• a second thin and elongated flexure having first and second ends coupled to an inner wall of the outer frame opposite from the first flexure, a portion of the second flexure intermediate between the first and second ends being interconnected to the first flexure at a portion thereof intermediate between the first and second ends thereof.

A method for suspending and isolating an apparatus comprising:

• substantially surrounding an inner frame member with an outer frame member spaced apart therefrom by a slot formed between an inner peripheral edge of the outer frame member and an outer peripheral edge of the inner frame member;
• interconnecting a plurality of first flexures spaced about the inner peripheral edge of the outer frame member;
• interconnecting a plurality of second flexures spaced about the outer peripheral edge of the inner frame member at a position opposite from a corresponding one of the first flexures;
• and
• interconnecting a center portion of each of the second flexures with a center portion of the corresponding first flexure.