US 5,057,684 AGranted

Unitary aligning and gapping apparatus for modular optical shaft encoder

AssigneeRobbins & Myers/Electro-Craft, a wholly owned sub. of Robbins & Myers, Inc.

InventorGregg R. Service

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Abstract

An apparatus and method is disclosed for centering a pattern wheel of a modular optical shaft encoder and setting a predetermined gap distance between the pattern wheel and a mask and photodetector. The apparatus is built in to the encoder and facilitates aligning and gapping of the pattern wheel with respect to the mask and photodetector during installation of the encoder about a rotatable shaft. The apparatus consists of a slidable linear cam which cooperatively engages a centering collar to urge the collar against a pattern wheel, the pattern wheel is in turn urged into a predetermined position. The collar is retractable from contact with the pattern wheel after the pattern wheel is mounted in position on the rotatable shaft to allow rotation of the wheel and the shaft.

Claims12

Dependent claims

An improved modular optical shaft encoder having an encoder body with an upper body surface constructed and arranged for receiving a pattern wheel generally radially parallel to the upper surface, the encoder body also having a light source affixed to the upper surface and an opening constructed and arranged for receiving a rotatable shaft, the encoder body being constructed and arranged for mounting on an external element stationary with respect to the rotatable shaft, the encoder also having a mask mounted above the encoder body upper surface aligned opposite the light source, the pattern wheel positioned between the upper body surface of the encoder body and the mask, the hub coaxially aligned with the opening of the encoder body, the hub having a central shaft hole for receiving the shaft inserted through the opening in the encoder body, the hub of the pattern wheel being constructed and arranged for axial positioning and mounting on the shaft, the encoder also having a photodetector positioned behind the mask from the wheel on the upper surface of the encoder body, the photodetector aligned with the light source and facing the upper body surface through the mask such that light from the light source is detectable by the photodetector through the pattern wheel and through the mask, wherein the improvement comprises:

the encoder body defining a radial enclosed passage parallel to the upper surface, the proximal end of the passage communicating with the opening and the distal end communicating with an exterior of the encoder body;
a linear cam mounted for slidable movement from a first to a second position along the passage within the encoder body for extension through the proximal and distal ends of the passage;
a centering collar having a central collar bore, the collar coaxially positioned for axial translation within the opening, an outside circumference of the collar constructed and arranged for nesting within a circumference of the opening, the collar also having a plurality of circumferential indentations and projections constructed and arranged for operative engagement with the linear cam extending through the proximal end of the passage;
such that movement of the cam to the first position displaces the collar from contact with the hub and movement of the cam to the second position urges translation of the collar into a light press fit contact with the wheel and establishes an interference fit between the hub and an inside circumference of the collar bore, with the light press fit contact and interference fit together causing alignment of the pattern wheel with the mask and the light source and positioning of the wheel a predetermined gap distance from the mask, the alignment and the gap distance being maintained during mounting of the pattern wheel on the shaft and mounting of the encoder body on the external element.

1 more element

In a method of mounting and aligning a modular optical shaft encoder of the type wherein a rotatable shaft is inserted through an opening in an encoder body and through a hub of a rotatable pattern wheel, the hub having a central shaft hole to receive the shaft, the encoder body having an upper body surface to receive the pattern wheel, the encoder having a photodetector mounted above a mask, the photodetector facing a light source through the mask and the pattern wheel, the light source being mounted on upper body surface of the encoder body, the improvement comprising:

immobilizing the pattern wheel, aligning the pattern wheel with respect to the mask and the photodetector and positioning the pattern wheel a predetermined gap distance from the mask and the photodetector through an interference fit between an inside circumference of a center bore of a centering collar and the pattern wheel hub, and a light press fit contact between the collar and the wheel, the centering collar positioned for axial translation within the body opening, the encoder body also having a radial enclosed passage generally parallel to the upper surface of the encoder body, a proximal end of the passage communicating with the opening and a distal end of the passage communicating with an exterior of the encoder body, the encoder body also having a linear cam mounted for slidable movement from a first to a second position along the radial passage, the cam operatively engaging a plurality of indentations and projections on the outer circumference of the centering collar such that the immobilizing, aligning and positioning of the pattern wheel is effected by moving the cam to the second position which urges the collar toward the pattern wheel and into the light press fit contact with the wheel and interference fit with the hub;
inserting a rotatable shaft through the opening in the encoder body, through the centering collar, center bore and through the central shaft hole in the pattern wheel hub;
mounting the pattern wheel hub on the shaft;
mounting the encoder body to an element fixed with respect to the rotatable shaft;
an
moving the linear cam to the first position radially inward toward the opening from the second position such that the centering collar is displaced from the light press fit contact with the wheel and interference fit with the pattern wheel hub.

3 more elements

Dependencies are inferred from the claim text.

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Abstract

the encoder body defining a radial enclosed passage parallel to the upper surface, the proximal end of the passage communicating with the opening and the distal end communicating with an exterior of the encoder body;
a linear cam mounted for slidable movement from a first to a second position along the passage within the encoder body for extension through the proximal and distal ends of the passage;
a centering collar having a central collar bore, the collar coaxially positioned for axial translation within the opening, an outside circumference of the collar constructed and arranged for nesting within a circumference of the opening, the collar also having a plurality of circumferential indentations and projections constructed and arranged for operative engagement with the linear cam extending through the proximal end of the passage;
such that movement of the cam to the first position displaces the collar from contact with the hub and movement of the cam to the second position urges translation of the collar into a light press fit contact with the wheel and establishes an interference fit between the hub and an inside circumference of the collar bore, with the light press fit contact and interference fit together causing alignment of the pattern wheel with the mask and the light source and positioning of the wheel a predetermined gap distance from the mask, the alignment and the gap distance being maintained during mounting of the pattern wheel on the shaft and mounting of the encoder body on the external element.

1 more element