GB1421666A - Medical penetrative ray apparatus - Google Patents

Abstract

1421666 Control of AC motors SIEMENS AG 15 June 1973 [15 June 1972] 28688/73 Addition to 1392468 Heading H2J [Also in Division H5] Movement of an X-ray table to a pre-set position relative to a fixed starting position by a synchronous electric motor is achieved either by use of an adjustable timer in the motor control circuit, Fig. 2 (not shown), permitting energization of the motor in either direction for a desired period, or, as shown, by use of a pulse counter 23, light from a source 26 being reflected onto a photocell 29 by a scale 21 fixed to the X-ray table and producing a pulse at each scale division due to modulation of the reflected light. The capacity of the pulse counter is pre-set by a dial 12, the direction of rotation of which also operates a reversing switch 25, the counter also controlling a switch 24 to switch off the motor 8 when the pre-set pulse count has been achieved. Reference is made to an alternative control arrangement in which a self-balancing resistance bridge is employed, one arm of which is pre-set, and another of which is adjusted by movement of the table. Members 21-25 may be taken out of use by operating a changeover switch 13 whose contacts 19, 20 open and contacts 16, 17 close, whereby the motor 8 is supplied through a reversing switch 15 to drive the table to a desired starting position.