Automatic window/door system

Claim 1

A motor-driven window/door system comprising: a pressure responsive sensor arranged in association with a window or door; detector circuit means coupled to said pressure responsive sensor for detecting a squeezed object caught in the way of said window or door; an electric motor for driving said window or door to open and close said window or door; control circuit means for controlling said motor; said pressure responsive sensor comprising a coaxial sensor having an inner electrode, an outer electrode and a pressure responsive element interposed between said inner and outer electrodes and having a variable resistance responsive to pressure on said pressure responsive sensor; said detector circuit means comprising a pressure detector means coupled to said pressure responsive sensor for generating a signal indicative of a pressure on said pressure responsive sensor, and differentiation means coupled to said pressure detector means for generating a signal indicative of a rate of change of said pressure; said control circuit means comprising direction control means coupled to said detector circuit means for controlling said motor in response to the squeezed object in the way of said window or door in such a direction to release said object from said window or door, motor pulse detector means coupled to said motor for detecting pulses having a repetition rate essentially proportional to a rotational speed of said motor from said motor; power-down means coupled to said motor pulse detector means for restricting the power to said motor in response to reduction in repetition rate of the pulses indicative of an overload state of said motor; said power-down means includes a stopping means for selectively stopping power supplied to said motor in accordance with the repetition rate of the pulses; said stopping means includes a charging-and-discharging circuit, said charging-and-discharging circuit including means for charging said charging-and-discharging circuit in response to a pulse from said motor to establish a reference potential at an output terminal of said charging-and discharging circuit, and means for discharging said charging-and-discharging circuit until the next pulse is supplied from said motor to increase the potential at said output terminal of said charging-and-discharging circuit, and said stopping means further includes a means coupled to said output terminal to said charging-and-discharging circuit for deenergizing said motor and for stopping the pulses supplied to said power-down means when the potential at said output terminal exceeds a predetermined level.