GB1278041A - Positioning mechanism - Google Patents

Abstract

1278041 Cams H A H SPENCE-BATE 4 June 1969 [7 March 1968] 11180/68 Heading F2K [Also in Division G2] A positioning mechanism for use in a microfiche camera or projector includes a rotatable drum 15 having a cam groove 16 thereon engaged by a follower 17 secured to a frame 11 to be moved along rails 13, 14 parallel to the cam axis of rotation, the follower being precisely located at predetermined positions by engagement in respective notches 19 (Fig. 1). In Fig. 1, the drum 15 is spring-connected to its shaft 18 and has a helical cam groove 16 and return groove 20 interconnected by transfer slots 21, 22, 23. As the cam drum 15 is rotated in direction F, the frame 11 is advanced by the action of the continuous wall of the cam groove 16 on the follower. When a notch 19 has just passed the follower, the drum 15 is reversed and the follower engaged and located by the notch. Subsequent rotation of the drum 15 in direction F continues the advance of the frame 11. Reversal of a motor driving the shaft 18 is controlled by a microswitch 59/60 (Fig. 3) actuated by a two-part cam 50/51 on a shaft 52 connected to the shaft 18. A disc 51 freely rotatable on the shaft 52 is connected to a disc 50 secured to the shaft 52 by springs 55. Pegs 54 on the disc 51 co-operate with shoulders 61 on the disc 50 to limit relative rotation therebetween. During advance of the frame 11 the shaft 52 is rotated clockwise (Fig. 3), the disc 51 being held by the roller 58. At the limit position shown, corresponding to a notch 19 passing the follower 17, the rise 56 of disc 50 lifts the roller 58 to close the contacts 59, 60 to reverse the motor, and hence shafts 18, 52. The springs 55 cause disc 51 to catch up with disc 50, the cam surface 57 holding contacts 59, 60 closed while the notch 19 engages the follower 17. On restarting the motor to rotate the drum 15 in direction F, the roller 58 drops into the next cam recess, opening the contacts 59, 60. The depth of a notch 19 may be adjustable by means of a sliding wall portion (Fig. 7, not shown). Fig. 6 shows a modification allowing reversal of the drive to the frame 11 at almost any point on the cam groove 81, a deflector block 82 being provided adjacent each notch 86. In a microfiche positioner, a second mechanism as described above is mounted on the frame 11 to move a film carrier normal to the direction or motion of the frame 11.