Patent ID: 7731208
Filing Date: 2010-06-08
Classification: B62D

Abstract:
1. A tag axle operating system for a tag axle having wheels with tires and air brakes wherein the tag axle is suspended from a motor vehicle and is raised and lowered by pivotal movement about a first axis by operation of parallel-arranged hydraulically-operated actuators and can also pivot about a second axis located equidistant from the tag axle wheels and laying in a plane at right angles to the first axis, said system comprising a closed gas circuit charged with a gas at a prescribed gas pressure, a hydraulic circuit adapted to deliver hydraulic fluid under pressure to the actuators to raise and establish the tag axle in an inactive condition and to lower and establish the tag axle in an active condition, said hydraulic circuit adapted when the tag axle is in said active condition to establish a prescribed hydraulic operating pressure opposing the gas pressure and a resulting force on the tag axle forcing the tires to bear against a road surface and the tag axle to accept a predetermined load, a brake valve adapted to allow air under pressure to be delivered to operate the air brakes while said prescribed hydraulic operating pressure is maintained and to prevent such delivery to thereby disable the air brakes when said prescribed hydraulic operating pressure is relieved, and said hydraulic circuit adapted while the tag axle is in said active condition to relieve said prescribed hydraulic operating pressure and thereby relieve the force on the tag axle and disable the air brakes when the tag axle experiences a predetermined tilt angle when pivoting about the second axis.