Importance

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Abstract

A control circuit for an electrically adjustable patient chair that is adapted when actuated by the momentary depression of a start button, to automatically return the chair to its fully down and tilt forward position. The control circuit includes a multiple-pole relay that is latched in the closed position to energize both motor windings by a solid state switching device that is gated to the on state by a current transformer that senses the load current in a conductor that passes through the core of the transformer. The adjustment motors remain energized until a pair of limit switches are opened upon the chair attaining its exit position. The resulting current drop to zero in the load line is sensed by the current transformer which turns off the solid state switching device which in turn unlatches the relay. Thus, it will be appreciated that the present control circuit automatically 'resets' itself after the chair has returned to its fully down and tilt forward position so as to permit normal operation of the height and tilt adjustment motors.

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First Claim