Miniature inertial grade high shock and vibration capability accelerometer and method with axis alignment and stability features

Claim 2

In an accelerometer, a support base, a pair of spaced spring support means attached to the support base, a moving system pivotally supported by said spring support members responsive to acceleration experienced by said support base, pickoff means disposed to sense motion of said moving system relative to said support base for providing output signals related thereto, torquing means responsive to said output signal for restoring said moving system to a neutral position, each of said spaced spring support means including preload and primary leaf springs, a pivot bearing mounted on each of said primary leaf springs, and engaging said moving system and a viscoelastic material positioned between said preload and primary leaf springs, whereby resonance of the moving system on said spring support means in inhibited by the damping characteristic of said viscoelastic material.

Claim 3

An accelerometer as in claim 1 together with pivots on said moving system formed to fit and rotate in said pivot bearings, means contacting said preload leaf spring for adjusting preload force exerted by said spring support members on said pivots, means for adjusting the alignment of the acceleration sensing axis relative to an external reference plane and shock stops on the support base for limiting motion of the moving system to preclude occurrence of damaging forces exerted on said pivot bearings by said pivots, said means for adjusting preload operating to provide for predetermined moving system performance in shock and vibration environments.

Claim 4

An accelerometer as in claim 1 wherein said pickoff means comprises first and second light emitting diodes mounted in the support base spaced apart from first and second photo transistors respectively and wherein said moving system includes first and second shutter flags interposed between said first and second light emitting diodes and said first and second photo transistors respectively.

Claim 5

An accelerometer as in claim 3 wherein said shutter flags are closer to said light emitting diodes than to said photo transistors thereby creating an optiCal lever between said light emitting diodes and photo transistors, whereby a small arc of shutter flag pivotal motion causes a larger translation of the light beam emitted by said light emitting diodes across the face of said photo transistor, said optical lever increasing the gain of the system.

Claim 6

An accelerometer as in claim 3 wherein said first and second shutter flags operate as a support for the moving member of said torquing means, as shock stops, and as light metering members for said photo transistors.

Claim 7

An accelerometer comprising a support base having an external reference defining the sensitive axis, a seismic mass pivotally supported in said support base, pickoff means disposed between the seismic mass and the support base for providing output signals due to pivotal motion of the mass from a neutral position relative to the support base, torquing means responsive to said output signal for restoring the mass to said neutral position, and a pair of spring support members attached to said support base for pivotally supporting said seismic mass, said spring support members including first and second leaf springs, and viscoelastic material positioned between said first and second leaf springs, whereby resonance of the mass on said spring support members is prevented by the damping characteristic of said viscoelastic material.

Claim 8

An accelerometer comprising a support base having an external reference defining the sensitive axis, a seismic mass pivotally supported in said support base, pickoff means disposed between the seismic mass and the support base for providing output signals due to pivotal motion of the mass from a neutral position relative to the support base, torquing means responsive to said output signal for restoring the mass to said neutral position, and a pair of spring support members attached to said support base for pivotally supporting said seismic mass, said spring support members including first and second leaf springs, and viscoelastic material positioned between said first and second leaf springs, whereby resonance of the mass on said spring support members is prevented by the damping characteristic of said viscoelastic material.

Claim 9

An accelerometer as in claim 6 wherein said spring support members include pivot bearings in said first leaf spring and said seismic mass has pivots defining a pivot axis and formed to fit and rotate in said pivot bearings, together with means for aligning the pivot axis relative to the external reference on said support base, means contacting said second leaf spring for adjusting preload force between said pivot bearings and said pivots, and shock stops on said support base for limiting motion of said seismic mass to preclude occurrence of damaging forces between said pivot bearings and said pivots, said means for adjusting preload force operating to provide predetermined shock and vibration capability.

Claim 10

An accelerometer as in claim 6 wherein said pickoff means comprises first and second light emitting diodes mounted in said support base spaced apart from first and second photo transistors respectively, and wherein said seismic mass includes first and second shutter flags interposed between said first and second light emitting diodes and first and second photo transistors respectively for metering the quantity of light received by said first and second photo transistors from said first and second light emitting diodes respectively.

Claim 11

An accelerometer as in claim 8 wherein said shutter flags are closer to said light emitting diodes than to said photo transistors thereby creating an optical lever between said light emitting diodes and said photo transistors whereby a small arc of shutter flag rotation causes a larger translation of the light beam emitted by said light emitting diodes across the face of said photo transistor, said optical lever increasing the gain of the system and decreasing error components due to photo transistor temperature sensitivity.

Claim 14

In an accelerometer, a support base, pivot bearings carried by said support base, a moving system, pivot elements defining a pivot axis mounted on said moving system for contacting said bearings, pickoff means including first and second light emitting diodes, first and second photosensitive devices disposed to receive the light energy from said first and second light emitting diodes respectively, said pickoff means further including a moving member responsive to acceleration mounted on said moving system for sensing motion of said moving system above said pivot axis and for providing output signals related to said motion, said moving member including first and second integral shutter flags for metering the amount of light energy received by said first and second photosensitive devices respectively, said shutter flags being located closer to said light emitting diodes than to said photosensitive devices, thereby creating an optical lever therebetween, whereby moving system pivoting motion causes said shutter flag to translate through a larger portion of the light energy beam emitted by said light emitting diodes and causes greater change per increment of moving system arc motion in the amount of light energy received by said phototransistors, torquing means carried on said moving system for providing a restoring torque to said moving system responsive to said output signal, said torquing means including a torque coil integral with said moving system and having a coil axis disposed at substantially 90* to said shutter flags about said pivot axis whereby said torquing means and pickoff means lever arms as measured from the pivot axis within a given accelerometer volume is maximized.

Claim 15

In an accelerometer, a support base, pivot bearings carried by said support base, a moving system, pivot elements defining a pivot axis mounted on said moving system for contacting said bearings, pickoff means including first and second light emitting diodes, first and second photosensitive devices disposed to receive the light energy from said first and second light emitting diodes respectively, said pickoff means further including a moving member responsive to acceleration mounted on said moving system for sensing motion of said moving system above said pivot axis and for providing output signals related to said motion, said moving member including first and second integral shutter flags for metering the amount of light energy received by said first and second photosensitive devices respectively, said shutter flags being located closer to said light emitting diodes than to said photosensitive devices, thereby creating an optical lever therebetween, whereby moving system pivoting motion causes said shutter flag to translate through a larger portion of the light energy beam emitted by said light emitting diodes and causes greater change per increment of moving system arc motion in the amount of light energy received by said phototransistors, torquing means carried on said moving system for providing a restoring torque to said moving system responsive to said output signal, said torquing means including a torque coil integral with said moving system and having a coil axis disposed at substantially 90* to said shutter flags about said pivot axis whereby said torquing means and pickoff means lever arms as measured from the pivot axis within a given accelerometer volume is maximized.

Claim 16

An accelerometer as in claim 11 together with spaced spring support means including preload and primary leaf springs, said pivot bearings being mounted on said primary leaf spring, a viscoelastic material positioned between said preload and primary leaf springs and means for applying force to said preload leaf spring, whereby preload forces are created on said pivot axis and resonance of the moving system on said spring support means is inhibited by the damping characteristic of said viscoelastic material.

Claim 17

In an accelerometer, a support base, a pair of spaced spring support assemblies secured to the support base, a moving system having a flag, pivot and bearing assembly engaging the moving system and a spring support assembly, pickoff means for sensing the position of the flag and for providing an output signal related to pivotal motion of said moving system and the flag carried thereby, restoring means responsive to said output signal for applying a force to the moving system, each of said spaced spring support assemblies including first and second leaf springs overlying each other, means for preloading said second spring to apply a force to said first spring, and a viscoelastic material positioned between said first and second leaf springs, whereby resonance of the moving system on said spring support assemblies is prevented by the damping characteristics of said viscoelastic material.

Claim 18

In an accelerometer, a support base, a pair of spaced spring support assemblies secured to the support base, a moving system having a flag, pivot and bearing assembly engaging the moving system and a spring support assembly, pickoff means for sensing the position of the flag and for providing an output signal related to pivotal motion of said moving system and the flag carried thereby, restoring means responsive to said output signal for applying a force to the moving system, each of said spaced spring support assemblies including first and second leaf springs overlying each other, means for preloading said second spring to apply a force to said first spring, and a viscoelastic material positioned between said first and second leaf springs, whereby resonance of the moving system on said spring support assemblies is prevented by the damping characteristics of said viscoelastic material.

Claim 19

In an accelerometer, a support base, a pair of spaced spring support means attached to the support base defining a pivot axis, a moving system pivotally mounted on said spring support members, pickoff means including a moving member mounted on said moving system for sensing motion of said moving system about said pivot axis and for providing output signals related to said motion, said spaced spring support means including preload and primary leaf springs, pivot bearings mounted on said primary leaf spring, and a viscoelastic material positioned between said preload and primary leaf springs, whereby resonance of the moving system on said spring support meanS is prevented by the damping characteristics of said viscoelastic material.

Claim 20

In an accelerometer, a support base, a pair of spaced spring support means attached to the support base defining a pivot axis, a moving system pivotally mounted on said spring support members, pickoff means including a moving member mounted on said moving system for sensing motion of said moving system about said pivot axis and for providing output signals related to said motion, said spaced spring support means including preload and primary leaf springs, pivot bearings mounted on said primary leaf spring, and a viscoelastic material positioned between said preload and primary leaf springs, whereby resonance of the moving system on said spring support meanS is prevented by the damping characteristics of said viscoelastic material.

Claim 21

An accelerometer as in claim 14 wherein said pickoff means includes a first photosensitive device and a first light source mounted on said support base to direct light energy toward said photosensitive device and wherein said moving member intercepts at least a portion of said light energy.

Claim 22

An accelerometer as in claim 15 together with a second photosensitive device and a second light source mounted on said support base at a substantial angle about said pivot axis from said first photosensitive device and wherein said moving member alternately intercepts at least a portion of light energy from said first and second light sources, said first and second photosensitive devices, being connected to provide a difference output whereby the magnitude of said output signals is increased for a given motion of said moving system about said pivot axis.

Claim 23

In an accelerometer, a mounting base, a pivoting element, bearings carried by said mounting base for pivotally supporting said pivoting element and defining a pivot axis for said pivoting element, means for generating a permanent magnetic flux field mounted in said mounting base, a torque coil carried by said pivoting element disposed in said magnetic flux field for providing a restoring torque to said pivoting element, said pivot axis lying in the plane of symmetry of said torque coil, pickoff means mounted on said mounting base including light source and a solid state photo sensing device positioned to receive light energy from said light source, a moving member responsive to acceleration carried by said pivoting element and positioned adjacent to said light source and spaced from said photo sensing device, said moving member position providing for an optical lever advantage providing system gain and reducing system noise, whereby said moving member meters said light energy received by said photo sensitive device producing an output signal therefrom indicative of acceleration.

Claim 24

In an accelerometer, a mounting base, a pivoting element, bearings carried by said mounting base for pivotally supporting said pivoting element and defining a pivot axis for said pivoting element, means for generating a permanent magnetic flux field mounted in said mounting base, a torque coil carried by said pivoting element disposed in said magnetic flux field for providing a restoring torque to said pivoting element, said pivot axis lying in the plane of symmetry of said torque coil, pickoff means mounted on said mounting base including light source and a solid state photo sensing device positioned to receive light energy from said light source, a moving member responsive to acceleration carried by said pivoting element and positioned adjacent to said light source and spaced from said photo sensing device, said moving member position providing for an optical lever advantage providing system gain and reducing system noise, whereby said moving member meters said light energy received by said photo sensitive device producing an output signal therefrom indicative of acceleration.