4 is an enlarged fragmentary view, partially in section, of an embodiment of the present.invention FIG. 3 is a sectional view taken along the line 3-3 in FIG. 2 is a front elevational view, partially in section, of the automatic slack adjuster illustrated in FIG. 1 is a front elevational view of the automatic slack adjuster of the present invention FIG. Other means, such as variable diameter pivot pins, may be utilized to selectively vary the clearance between the pin and the bore.Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:FIG. The above is accomplished by utilizing a pivotal connection in the linkage assembly comprising a bore having a considerably larger inner diameter than the outer diameter of the pivot pin received therein and providing a member, such as a set screw accessible from the exterior of the adjuster, which can be variably extended into the bore to vary the effective clearance between the pivot pin and the bore to vary the lost motion in the linkage assembly and thus the preselected running clearance maintained by the adjuster.

However, in these prior art clearance sensing slack adjusters the preselected running clearance was a function of total 'lost motion' in the linkage and adjuster assembly and was not readily adjustable to compensate for factors such as different types of friction linings, different operating conditions, new linings or the like.In accordance with the present invention, the drawbacks of the prior art have been overcome by the provision of an automatic clearance sensing slack adjuster for brakes having a running clearance that may be adjusted by controlled rotation of a shaft, such as for example, cam actuated brakes, wherein the preselected running clearance maintained by the adjuster is quickly and easily adjusted without requiring substitution of parts or access to the interior of the adjuster.

The prior art clearance sensing types of automatic slack adjusters have been well received and are considered to be an improvement over earlier types of automatic slack adjusters. These prior art slack adjusters are generally referred to as clearance or force sensing slack adjusters and examples thereof may be seen by reference to United States Patents Nos.Re. In some of these prior art adjusters, in order to avoid an excessive adjustment, the one-way drive mechanisms were designed to either yield, declutch or to slip when the torque necessary to continue adjusting of the cam by rotation of the worm shaft exceeded a predetermined limit. More particularly, the present invention relates to automatic slack adjusters of the clearance sensing type for cam actuated brakes.It is known in the prior art to provide automatic slack adjusters for brakes, such as cam actuated brakes, which contain worm gearing and a drive mechanism, preferably a one-way drive mechanism which together with a linkage converts the angular rotation of the slack adjuster lever body which occurs when the preselected running clearance between the brake drum and lining increases beyond a preset limit into a rotary motion of a shaft, such as the wormshaft, to restore the preselected clearance. This invention relates to automatic slack adjusters for maintaining a preselected running clearance between the friction members of a selectively engageable friction coupling and in particular relates to automatic slack adjusters for brakes having a running clearance that may be adjusted by controlled rotation of a shaft, such as for example, cam actuated brakes.

Slack adjuster