Disc-shaped centering fixture for optical encoders

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to the lower portion of FIG.
1, there is shown a motor casing 10 having a shaft 11 extending upwardly therefrom.
The optical encoder itself includes a mounting member 12 having a circular periphery 13 and carrying a light source 14 adjacent to a point on the periphery.
Mounting member 12 is further provided with a central opening 15 of larger diameter than the diameter of the motor shaft 11 so as to surround this shaft when the mounting member 12 is secured to the casing without touching the shaft.
Referring to the upper portion of FIG.
1, the encoder further includes a shutter component 16 having a central hub 17 arranged to be received on the shaft 11 in a friction fit so that the shutter 16 will rotate with the shaft.
The assembly is completed by the provision of a cover member 18 carrying a photoelectric cell 19 adjacent to a peripheral point as shown.
In assembling the encoder, the mounting member 12 is secured to the motor casing 10 by way of a first screw 20 passing through an opening 21 in the mounting member 12 into a tapped hole 22 in the casing 10 and a second screw 23 passing through another opening 24 in the mounting member 12 into a tapped hole 25 in the casing member on the diametrically opposite side of the shaft 11.
Next, the shutter 16 has its central hub portion 17 secured to the shaft 11 which is now extending upwardly through the central opening 15 of the mounting member 12.
Thereafter, the top cover 18 is secured to the top of the mounting member 12.
As indicated in FIG.
1, top cover 18 has holes such as indicated at 26 for cooperation with appropriately upwardly extending dowel pins, one of which is shown at 28 at the periphery of the mounting member 12.
The position of the holes and dowel members are such that the photoelectric cell 19 will be properly aligned with the light source 14 on the mounting member 12 when the components are assembled assuming that the mounting member 12 is properly concentric with the motor shaft 11