Piston braking device for hydraulic or pneumatic cylinders

Claim 1

A braking device for a hydraulic or pneumatic cylinder comprising: a cylindrical casing to be joined to one end of said cylinder and having an aperture in the outer end wall thereof for receiving a piston rod of said cylinder; a sleeve fitted on said piston rod within said casing; an annular braking plate loosely fitted on said piston rod within said casing; a resetting piston hermetically fitted between the inner periphery of said casing and the outer surface of said sleeve in side-by-side relation with said braking plate and axially supported on a fulcrum member for rocking movement thereabout together with said braking plate; a fluid chamber defined in said casing by said sleeve and resetting piston and connected to a pressure source; a plate driving means mounted at a position radially opposite to said fulcrum member and acting to rock said braking plate about said fulcrum member together with said piston into a braking position tilted relative to the axis of said piston rod; said braking plate having braking portions on the inner periphery thereof, said braking portions being brought into frictional contact with the circumference of said piston rod moving in one particular direction when said braking plate is tilted by said driving means thereby to apply to said piston rod a braking force increasing in proportion to the propelling force thereof; said resetting piston having a pressure receiving surface within said fluid chamber; and a brake control mechanism capable of applying pressure to said fluid chamber to push said resetting piston against said braking plate to maintain or reset said braking plate in normal position perpendicular to the axis of said piston rod.