Railway vehicle brake rigging and adjusting means

Claim 1

A railway vehicle brake rigging on a railroad bogie comprising in combination, a movable member for applying the brakes, a live brake lever coupled to a first brake shoe pivotable wIth movement of said member, a dead brake lever linked to the live brake lever and coupled to a second brakeshoe, a pivot point in said dead brake lever substantially fixed relative to said bogie, and an automatic slack adjuster affixed to said bogie with an axial spindle containing said pivot point, wherein the slack adjuster comprises non-self-locking screw threads on the spindle carrying a rotatable nut, two stationary clutch surfaces disposed to engage said nut to terminate axial motion of the spindle in either direction, a movable abutment axially moved with said live brake lever to engage the nut and locate it axially on said spindle by rotation to move the spindle axially with respect thereto and carrying therewith the dead brake lever pivot point to automatically adjust the slack in the rigging to maintain it within predetermined limits wherein the movable member actuating the live brake lever is a cylinder-and-piston unit and the movable abutment is connected to the live brake so that the movable abutment travels axially in dependence upon the piston stroke of the cylinder-and-piston unit, biasing means applying a predetermined axial force to said spindle in opposition to the axial force exerted on the spindle by said dead brake lever during a braking operation operable to cause the slack adjuster spindle and the dead lever pivot point to move axially in the braking direction when said force is overcome, mounting means disposing one of said two clutch surfaces so that it is disengaged before a substantial braking force has been established if the slack becomes too great and thereby permits said rotatable nut to rotate in one direction on said spindle and take up the excess slack, and mounting means operable when the slack becomes too small and the dead brake lever transmits to said spindle a force exceeding that of said biasing means to permit the nut to rotate in the opposite direction on said spindle to increase the slack in said system before engagement of said movable abutment with said nut.