Pneumatic control circuit for applying constant force

摘要

An air lifting and balancing unit including a cylinder, a piston in the cylinder, a ball screw affixed to the piston, a ball nut mounted for rotation on the ball screw, a drum mounted on the ball nut, a chain driven by the drum, and centrifugally actuated brakes mounted on the drum for stopping rotation of the drum when the drum exceeds a predetermined acceleration either due to a loss of load or to a loss of air pressure applied to the piston, and a pneumatic circuit in communication with the cylinder for providing air pressure thereto which applies a force on the piston which is at a substantially constant incremental value in opposition to the force exerted by the load applied to the piston through the chain and the drum and the ball screw regardless of variations in said air pressure to thereby cause the speed of the chain to remain substantially constant.