Automatic slack adjusting device of brake linkage

A device for automatic adjustment of the slack of brake linkage on a rail vehicle and the like, comprising first and second telescoping rod members at least one of which is tubular, one of said rod members being connected to a brake motor and the other rod member connected to brake linkage on a vehicle, a screw coupling between said first and second rod members and comprising first and second screw coupling members, one of said screw coupling members comprising a nut threaded upon the other screw coupling member comprising a spindle shaft having a non-self-locking thread, one of said nut and shaft being rotatable and connected for limited axial movement to said one rod member and the other of said nut and shaft being nonrotatable and rigidly connected to said other rod member, a moveable stop member engageable with a stop upon travelling a distance corresponding to the desired slack in the brake linkage, a first spring exerting a force upon said moveable stop member toward said stop and parallel to the direction of the braking force, a control clutch member slideably mounted upon said rotateable screw coupling member for axial movement thereon and having a closed position connecting said rotateable screw coupling member to said one rod member, said control clutch member requiring a force substantially less than the force exerted by said first spring to move out of its closed position to an open position, said control clutch member having a control element urged by said first spring in a direction to close said control clutch member, a rotary clutch between said one rod member and said rotateable screw coupling member to transmit braking force from said one rod member to said rotateable screw coupling member when in the closed position and displaceable into its closed position in a direction opposite to that of said control clutch member, a pretensioned second spring between said first and second rod members and urging said one rod member in a direction opposed to the braking force, said control clutch member being free of force exerted by said second spring.