Patent ID: 6684986
Filing Date: 2004-02-03
Classification: F16D

Abstract:
An adjuster mechanism for a drum brake of a vehicle, said adjuster mechanism including an extendable strut that is located between a first web of a first brake shoe and a second web of a second shoe to define a running clearance between said first and second shoes and a drum, said first and second brake shoes being retained on a backing plate that is secured to the vehicle such that a first engagement end of said first web and said second web is aligned with an anchor on said backing plate and a second engagement end is spaced apart by an actuator member, a first spring attached to said first and second webs urges the first engagement ends toward said anchor while a second spring is attached to a pawl of said adjuster mechanism that is retained on said first web and said second web urges said second engagement ends toward said actuator member such that said first and second brake shoes are positioned with respect to said drum to define said running clearance when said actuator is in a rest position, said actuator responding to an input force by acting on said first and second webs in opposition to said first and second springs and moving said first and second brake shoes through said running clearance and into engagement with said drum to effect a brake application, said adjuster mechanism including a shaft with a star wheel located between a first threaded section and a smooth section, said smooth section being retained in a bore of a first body of said extendable strut while said first threaded is mated a second threaded section in a second body of said extendable strut, said pawl pivoting on said first web with movement of said first web with respect to said actuator and rotating said star wheel when a predetermined pivotal movement occurs correspondingly rotate said first threaded section with respect to said second threaded section causing said extendable strut to expand and maintain said running clearance, said star wheel being characterized by a plurality of teeth while said pawl is characterized by a base with a first slot for receiving a pivot pin secured to said first web for securing said base to said first web, an opening for receiving said first end of said second spring, a second slot for receiving a first end of said first body of said extendable strut and an arm extending from said base to align a first blade thereon in perpendicular alignment with a first tooth of said plurality of teeth on said star wheel and to align a second blade thereon in a plane that is substantially parallel with a pitch of a second tooth of said plurality of teeth on said star wheel, said first blade engaging said first tooth when lever and first web are in said rest position while said second blade is offset a distance from said second tooth, said base pivoting on said pivot pin during a brake application with movement of said first web and when said web has moved toward said drum a predetermined distance said lever will have pivoted through a predetermined angle such that first blade slides past said first tooth and moves into engagement with a third tooth adjacent said first tooth while said second blade moves through said offset distance and into engagement with said second tooth such that said lever is now locked into engagement with said star wheel and first blade is prevented from moving past said third tooth and when said lever returns to said rest position said first blade now engages said third tooth to rotate said star wheel an increment defined by the pitch of said plurality of teeth as said second blade moves away from said star wheel said offset distance.