Vorrichtung zum selbsttaetigen Ausrichten von Werkstuecken

1,218,855. Photo-electric position finding. INTERNATIONAL BUSINESS MACHINES CORP. 14 June, 1968 [26 June, 1967], No. 28406/68. Heading H4D. [Also in Division B8] Though the invention broadly relates to an arrangement for positioning an article in a preselected translational and rotary orientation, the embodiment particularly described relates to a photo-electric arrangement for detecting the deviation of a semi-conductor chip 14, Fig. 2, from said preselected orientation and for causing the detected deviation to control servo-motors 29, 31, 33, whereby a platform 10, on which the chip is positioned is moved until said deviation is zeroed. The preselected orientation is defined by fixed axes X and Y, Fig. 1A, along which the edges of the chip are to be lined, Fig. 1B. Movement of the platform is caused by three servo-actuated screw piston/spring-loaded reaction piston pairs 16/17, 19/20 and 22/23- pairs 16/17 and 19/20 causing movement of the platform and chip along the X and Y axes respectively and pair 22/23 acting along a line parallel to axis to cause rotational movement of the platform. If the necessary movement of the pairs 16/17, and 19/20 are X 1 and Y 1 respectively, then the necessary movement of pairs 22/23 is given by where A is the distance between the lines of action 15 and 21 of pairs 16/17 and 22/23 and X 2 is the perpendicular distance detected between the Y axis and the edge 12 of the chip along a line 25 parallel to the X axis but spaced therefrom by a. Three photo-detectors 26, 27 and 28 respectively scan along lines 15, 18 and 25, and axes X and Y are defined by light projection thereof upon the platform. In the arrangement of Fig. 5 the photodetectors are indicated as 36, 37 and 38, wherein on detecting the projection of the X axis, detector 37 starts the operation of a pulse counter 40. Detection of the (illuminated) edge 13 of the chip stops the count, whereby the count represents distance Y 1 . This count then activates servomotor 31 such that screw piston 19 moves the platform until Y 1 becomes zero. In the same manner counter 39 connected to detector 36 produces a count representing X 1 , which count activates servomotor 29. Counter 41 connected to detector 38 produces a count representing X 2 . The outputs of counter 39 and 41 are fed to an inhibited gate 42 such that the gate produces a count representing (X 2 -X 1 ). In the same manner inhibited gate 44 produces a count representing (X 1 -X 2 ). Pulse multiplifiers 47 and 48 co