Slack adjuster built into a brake unit for a rail vehicle brake system

Claim 1

A slack adjusting brake unit mechanism for railway brake systems comprising in combination, a piston, a tube member attached to said piston and axially movable with said piston, an axially movable non-rotatable threaded spindle adapted for connection to the braking system coaxially positioned within said tube, a nut in non-self-locking thread engagement with said spindle having two opposed clutch surfaces axially displaced by the nut a first predetermined distance, a set of two clutch surfaces on said tube disposed for respectively mating with said clutch surfaces on said nut in different axial positions of said nut and spaced at an axial distance greater than said first predetermined distance thereby to transmit force from said piston to said spindle, two spaced shoulders on said nut, a fore control member and a rear control member both axially movable spaced between said two shoulders and adapted to engage them to limit axial movement of each respective control member in a corresponding direction, a spring between said control members urging them apart toward engagement with said shoulders, a housing, limit means affixed to said housing at two spaced positions limiting movement of said control members axially over a predetermined slack adjustment distance between said shoulders whereby contact of either said control member with a respective one of said limit means to move such away from one of said shoulders causes axial motion of said spindle to move said nut from a position with one opposed clutch surface thereon non-rotatably engaged with a corresponding mating clutch surface on said tube to an opposed axial position with the opposite clutch surfaces non-rotatably engaged passing through an intermediate position wherein the nut will rotate on said spindle with axial motion of the spindle.