Patent ID: 7886735

Claim:
A drive control mechanism for a vertically retractable down draft vent system, the drive control mechanism comprising: a first switch that interrupts a drive circuit that supplies power to a drive motor, the first switch interrupting the drive circuit when a framework of the vent system encounters a downwardly directed force equal to or greater than a threshold force; a second switch that interrupts the drive circuit when the framework of the vent system encounters an upwardly directed force equal to or greater than the threshold force; and an actuating element that is connected to the framework, the actuating element moving in response to the downwardly directed force equal to or greater than the threshold force to actuate the first switch to interrupt the drive circuit when the framework reaches a fully extended position, and the actuating element moving in response to the upwardly directed force equal to or greater than the threshold force to actuate the second switch to interrupt the drive circuit when the framework reaches a fully retracted position, wherein the actuating element moves in response to the downwardly directed force equal to or greater than the threshold force to actuate the first switch to interrupt the drive circuit when the framework is at a position other than the fully extended position and encounters the downwardly directed force equal to or greater than the threshold force, and the actuating element moves in response to the upwardly directed force equal to or greater than the threshold force to actuate the second switch to interrupt the drive circuit when the framework is at a position other than the fully retracted position and encounters the upwardly directed force equal to or greater than the threshold force.