Lock mechanism for service brake

Claim 1

A combined service and park brake arrangement, comprising: a support; a pedal arm pivotally mounted on the support for movement about a first axis between brake-release and brake-engage positions; biasing means mounted between the support and arm and urging the latter toward its brake-release position; a locking pawl pivotally mounted on the arm for movement about a second axis, extending parallel to the first, between an arm lock position, wherein it engages the support and prevents movement of the arm from its brake-engage position, and an unactuated position wherein it permits free movement of the arm between the brake-release and brake-engage positions; linkage means mounted solely on the arm and being pivotally connected between the arm and pawl and selectively operable to move the pawl between its arm lock and unactuated positions; said pedal arm including an integral foot pad facing in a first direction for engagement by an operator's foot; said linkage means including a first link having a first end pivotally connected to the pawl, a second link having a first end pivotally connected to the pedal arm adjacent said foot pad and the first and second links being of such length and having respective second ends pivotally interconnected to each other to form a knee joint which is displaced from the pad in a second direction 90° from the first direction and is elevated from the pedal arm in said first direction when the pawl is in its arm release position and is depressable to a position alongside the pedal arm to move the pawl to its arm lock position; and a pawl return spring connected between the pawl and the pedal arm and biasing the pawl toward its arm release position.