Automatic-adjustment drum brake

A drum brake assembly with an automatic brake shoe wear adjustment mechanism responsive to the application of different magnitudes of force applied by actuating means on an adjusting member and coupling means to prevent over-adjustment of brake shoes, comprising:

• a drum, a support member, a pair of brake shoes mounted on said support member in end-to-end relationship, actuating means disposed between one pair of adjacent shoe ends, anchoring means disposed between the other pair of adjacent shoe ends, an adjusting member pivotally mounted to one of said shoes, said actuating means engaging the end of other shoe and said adjusting member for direct displacement of the adjusting member when the actuating member is actuated, unidirectional coupling means between said one brake shoe and said adjusting member for allowing pivotal movement of said adjusting member in a direction toward the other of said shoes and prohibiting movement in the opposite direction, retraction means for interconnecting and urging said shoes into deactivated position, a strut extending between said brake shoes and having a lost-motion connection with said adjusting member for pivoting said adjusting member upon displacement of said shoes beyond a predetermined amount fixed by said lost-motion connection, said actuating means engaging the adjusting member at a point between the axis of pivotal movement of the adjusting member and a point of engagement of the adjusting member with the strut to render the adjusting member and coupling means operatively responsive to different magnitudes of force exerted thereon by said actuating means, and resilient means between said strut and other shoe, whereby outward displacement of said shoes by said actuating means to engage the shoes with the drum and exceeding said predetermined amount effects pivoting of the adjusting member to adjust the deactivated position of said shoes, and engagement of the actuating means with said adjusting member in cooperation with said resilient means prevents further pivoting of the adjusting member when the shoes experience subsequent outward displacement.