Slack adjuster for railway vehicle brake rigging

A double-acting compression actuatable slack adjuster for adjusting the slack in a railway vehicle brake linkage, said slack adjuster comprising:

• (a) an elongated hollow cylindrical housing member restrained against rotation and pivotally connectable at a first end thereof;
• (b) an elongated rod member restrained against said rotation and pivotally connectable at a first end thereof, said rod member having at least a portion thereof threaded, said threaded portion of said rod member extending into said housing member through a second end of said housing member;
• (c) a pair of opposite facing abutment surfaces positioned within a portion of said housing member;
• (d) a cone lock nut positioning means threadedly engaged with said threaded portion of said rod member intermediate a first and second end thereof, said positioning means axially movable between said abutment surfaces into respective first, second, and third positions for rotating about said threaded portion of said rod member when said positioning means is in said second position, thereby changing the length of said slack adjuster assembly by changing the relative longitudinal position between said housing member and said rod member;
• (e) a pair of opposed abutting surfaces carried by said positioning means for engaging respective adjacent abutment surfaces on said housing member to resist rotation of said positioning means about said rod member when said positioning means is in one of said first and said third positions;
• (f) a first spring urging means caged between said positioning means and a first spring seat carried by said rod member for urging said positioning means into said second position in disengagement from said abutment surfaces on said housing member;
• (g) a second spring urging means caged between said first end of said housing an abutment surface closely adjacent one end of a second spring seat for overcoming a force applied by said first urging means and for urging said positioning means into said first position, said second spring urging means having a load rating at least between about 2.0 and 3.0 times greater than the load rating of said first spring urging means;
• (h) a first overtravel control means having a portion thereof disposed axially reciprocal within said first end of said housing member for reducing a force applied by said second spring urging means to a force less than that applied by said first spring urging means, allowing said positioning means to move to said second position in response to overtravel, said first overtravel control means having a first ledge portion extending outwardly from an outer periphery thereof closely adjacent said one end which is engageable with said second spring seat;
• (i) an elongated hollow cylindrical portion removably engageable with said first end of said housing member for allowing reciprocal movement of said first overtravel control means;
• (j) at least one opening formed through a wall of said cylindrical portion;
• (k) an actuating means operable for actuating said first overtravel control means in response to a travel distance of a force applying member of the brake rigging, said actuating means comprising:
• (i) a bifurcated portion formed on said elongated hollow cylindrical housing member adjacent to and spaced from said first end thereof and having a first aperture formed therethrough, said first aperture having axis thereof being disposed generally vertically when said slack adjuster is installed in the brake rigging,
• (ii) a lever which has a first end thereof positioned within said bifurcated portion, a second end which extends through said at least one opening formed through a wall of said cylindrical portion past said elongated hollow cylindrical housing member, and an abutment which is formed intermediate said first and said second ends of said lever and which engages said first overtravel control means, said first end having a second aperture formed therethrough and aligned with said first aperture of said bifurcated portion, said second end has a third aperture formed therethrough, said third aperture having axis thereof being disposed generally horizontally when said slack adjuster is installed in the brake rigging,
• (iii) a pin inserted through said first and said second aperture and pivotally connecting said lever to said bifurcated portion, and
• (iv) a control member having a threaded portion received within said third aperture of said second end of said lever and connected thereto with a threaded fastener and a bifurcated portion being axially aligned with said threaded portion and having a forth aperture formed therethrough;
• (l) an eye portion formed as a single-piece casting with said cylindrical portion for pivotally connecting and restraining against rotation of said first end of said housing member;
• and
• (m) a second overtravel control means positioned in close proximity to said second end of said elongated hollow cylindrical housing member for reducing a frictional force generated during engagement of said respective abutment and abutting surfaces when said positioning means is in said second abutting engagement position and for preventing a jamming condition between said respective abutment and abutting surfaces causing operation of said slack adjuster to cease.