Electro-optical tachometer

Claim 2

An electro-optical tachometer comprising: a transparent disc concentrically mounted on a hub and having around the periphery thereof a plurality of alternately light transmissive and opaque equiangular sectors defining an optical pattern; a generally U-shaped stationary assembly adapted for mounting around the rotatable shaft of a device the speed of which is to be monitored, said assembly including: a generally U-shaped mounting plate having means for mounting said stationary assembly on said device; a spacer member of generally U-shaped configuration mounted on a surface of said mounting plate; a circuit board of a configuration conforming to the configuration of said spacer member and mounted thereon and having a plurality of photosensors disposed on a surface thereof and connected via conductive paths formed on said circuit board to a plurality of output terminals thereon; said spacer member and circuit board each having aligned corner portions; a housing having a plurality of mounting posts attached to said mounting plate and configured to mate with said corner portions to accurately maintain alignment of said mounting plate, spacer member, circuit board and housing constituting said stationary assembly, said housing also having a reticle plate with a reticle pattern formed thereon of like alternately light transmissive and opaque equiangular sectors as said optical pattern on said disc, a light source in spaced-apart relationship with said reticle plate and an opening between said reticle plate and light source through which the periphery of said disc containing said optical pattern is rotatable; and said hub being adapted for attachment to said rotatable shaft for maintaining said disc in aligned disposition in the opening in said housing between said reticle and said light source, such that said optical pattern and reticle pattern are cooperative upon rotation of said disc relative to said reticle to produce a variable light pattern representative of the speed of said disc and in response to which said photosensors produce at least one output signal representative of the speed of said disc.

Claim 3

An electro-optical tachometer comprising: a stationary assembly adapted for mounting around the rotatable shaft of a device the speed of which is to be monitored, said assembly Including; a mounting plate having an opening therein and fastening elements for mounting said assembly on said device; an electrically insulative spacer member having a shape and an opening conforming to that of said mounting plate and mounted on a surface of said mounting plate; a circuit board having a shape and an opening conforming to that of said spacer member and mounted on a surface thereof; a plurality of photosensors disposed on a surface of said circuit board opposite to the surface confronting said spacer member and connected via conductive paths formed on said circuit board to a plurality of output terminals thereon; said spacer member and circuit board each having aligned recessed corner portions; and a housing having first and second portions disposed on respective opposite sides of said photosensors and an outwardly extending portion spaced from said first and second portions and defining a channel, and a plurality of mounting posts attached to said mounting plate and configured to mate with said aligned recessed corner portions of said spacer member and circuit board to accurately maintain alignment of said housing, mounting plate, spacer member and circuit board constituting said stationary assembly; a transparent disc concentrically mounted on a hub and having a plurality of alternately light transmissive and opaque equiangular sectors formed on a surface around the periphery of said disc and defining an optical pattern; and a transparent reticle plate disposed on said first and second portions of said housing and having a reticle pattern of alternately light transmissive and opaque equiangular sectors identical to the optical pattern on said disc, said reticle pattern confronting said photosensors; a light source disposed in said outwardly extending portion of said housing and confronting said channel therein in a position to illuminate the adjacent portion of said reticle pattern and said photosensors; said hub being adapted for attachment to said rotatable shaft for maintaining the optical pattern of said disc in aligned disposition in the channel in said housing between said reticle plate and said light source, said disc being operative upon rotation relative to said reticle plate to produce a variable light pattern by interaction of said optical pattern and said reticle pattern in response to which said photosensors produce at least one output signal representative of the speed of said disc.

Claim 4

An electro-optical tachometer comprising: a stationary assembly adapted for mounting around the rotatable shaft of a device the speed of which is to be monitored, said assembly Including; a mounting plate having an opening therein and fastening elements for mounting said assembly on said device; an electrically insulative spacer member having a shape and an opening conforming to that of said mounting plate and mounted on a surface of said mounting plate; a circuit board having a shape and an opening conforming to that of said spacer member and mounted on a surface thereof; a plurality of photosensors disposed on a surface of said circuit board opposite to the surface confronting said spacer member and connected via conductive paths formed on said circuit board to a plurality of output terminals thereon; said spacer member and circuit board each having aligned recessed corner portions; and a housing having first and second portions disposed on respective opposite sides of said photosensors and an outwardly extending portion spaced from said first and second portions and defining a channel, and a plurality of mounting posts attached to said mounting plate and configured to mate with said aligned recessed corner portions of said spacer member and circuit board to accurately maintain alignment of said housing, mounting plate, spacer member and circuit board constituting said stationary assembly; a transparent disc concentrically mounted on a hub and having a plurality of alternately light transmissive and opaque equiangular sectors formed on a surface around the periphery of said disc and defining an optical pattern; and a transparent reticle plate disposed on said first and second portions of said housing and having a reticle pattern of alternately light transmissive and opaque equiangular sectors identical to the optical pattern on said disc, said reticle pattern confronting said photosensors; a light source disposed in said outwardly extending portion of said housing and confronting said channel therein in a position to illuminate the adjacent portion of said reticle pattern and said photosensors; said hub being adapted for attachment to said rotatable shaft for maintaining the optical pattern of said disc in aligned disposition in the channel in said housing between said reticle plate and said light source, said disc being operative upon rotation relative to said reticle plate to produce a variable light pattern by interaction of said optical pattern and said reticle pattern in response to which said photosensors produce at least one output signal representative of the speed of said disc.

Claim 5

An electro-optical tachometer according to claim 2 wherein said stationary assembly is angularly adjustable with respect to the device on which it is mounted and to an extent permitted by the fastening elements of said mounting plate to provide a skewed orientation of said reticle pattern relative to the optical pattern of said disc thereby to provide upon rotation of said disc an interference pattern having radially directed fringes sensible by said photosensors.

Claim 6

An electro-optical tachometer according to claim 3 wherein said photosensors include a pair of photosensors connected in phase opposition to provide in response to said interference pattern an output signal representative of the speed of said disc and compensated for low frequency spurious variations in said output.

Claim 7

An electro-optical tachometer according to claim 3 wherein said photosensors include two pairs of photosensors each pair being connected in phase opposition to provide in response to said interference pattern a compensated output signal representative of the speed of said disc, said pairs of photosensors being arranged in spatial phase quadrature with respect to said interference pattern to provide output signals representative of the sense of rotation of said disc.