Abstract: An anti-theft device for preventing unauthorized release of the air brakes on a vehicle includes a lockable button for the valve stem for the control valve. The lockable button includes a button body, a coupling member, and a lock assembly having a latch member that selectively inserts into an annular groove on the coupling member. The coupling member is secured to move axially with the axially movable valve stem of the air brake control valve. The latch member extends into the annular groove on the coupling member to position the button body so as to limit the axial movement of the valve stem and thereby prevent the release of the air brakes.

Abstract: A lock mechanism includes a casing having a cavity therein, a shaft with an annular recess insertable into the cavity, a lock tumbler with a rotatable output member, and a spring-biased rigid locking clip pivotally mounted to the casing in the cavity so as to normally engage the recess in the shaft to secure the shaft to the casing unless pivoted out of the recess by the output member of the lock tumbler. Such a lock mechanism can used be to solve many different security problems, including securing a ball to the ball socket of a trailer hitch as a deterrent to theft of the trailer.