Patent ID: 6377009
Filing Date: 2002-04-23
Classification: E05F,E05Y,H03K

Abstract:
A control system responsive to an obstruction to a panel closure, the panel adapted to be moved by a motor from an open state to a closed sate in which a leading edge of the panel is adjacent a predetermined portion of a frame, the system comprising;a controller adapted to control the motor; end-of-travel sensing means adapted to provide an output to the controller when the panel is in one of the open state or the closed state; capacitive obstruction sensing means comprising a plate disposed adjacent the predetermined portion of the frame, the plate electrically coupled to an electrical ground by a shunting conductor substantially conducting electrical current pulses having durations greater than a first predetermined value, the shunting conductor substantially not conducting current pulses having durations less than a second predetermined value, the capacitive obstruction sensing means having an output to the controller, the capacitive obstruction sensing means comprising: a source of DC current for charging the plate; a voltage pulse source adapted to output a discharging voltage pulse having a duration less than the second predetermined value; and a discharging switch having an open state and a closed state, the discharging switch moving from its open to its closed state responsive to the discharging voltage pulse, the discharging switch connecting the plate to a charge measuring means when in the closed state, the discharging switch otherwise not connecting the plate to the charge measuring means; wherein the controller is adapted to stop the motor if the output from the obstruction sensor exceeds a predetermined threshold value.