Patent ID: 6206148
Filing Date: 2001-03-27
Classification: F16D

Abstract:
A drum brake assembly (10) having first (12) and second (14) brake shoes retained on a backing plate (16) by first (18) and second (20) pins, each of said first (12) and second (14) brake shoes having a first end (22,24) and a second end (28,30), said first ends (22,24) being connected to a hydraulic actuator assembly (26) secured to said backing plate (16) and said second ends (28,30) being connected to a an anchor block (40) secured to said backing plate (16), said first ends (22,24) being selectively spaced apart by an adjustable strut mechanism (32) having an extendable shaft (33) with first end (34) which engages said first brake shoe (12) adjacent said first end (22) and a second end (36) which engages said second brake shoe (14) adjacent said first end (24), first resilient means (48) for urging said first (12) and second (14) brake shoes toward said anchor block (40) and second resilient means (150) for urging said first (12) and second (14) brake shoes toward said hydraulic actuator assembly (26), said adjustable strut mechanism (32) having a length which establishes a predetermined running clearance between a first friction pad (42) associated with said first brake shoe (12), a second (44) friction pad associated with said second brake shoe (14) and a drum (46), said hydraulic actuator assembly (26) responding to a first input to respectively move said first (42) and second (44) friction pads into engagement with said drum (46) and effect a first brake application and a mechanical actuator (50) connected to said first (12) and second (14) brake shoes for providing a second input to respectively move said first (42) and second (44) friction pads into engagement with said drum (46) and effect a second brake application, said mechanical actuator (50) being characterized by said extendable shaft (33) having a shaft (33) with a first end (34) separated from a second end (36) by a rotatable stem (35), said rotatable stem (35) having a first cylindrical surface (31) retained in a bore in said first end (34), a second cylindrical surface (37) which engages said first end (34) and a third cylindrical surface (39) with threads thereon which mate with threads in said second end (36), said first end (34) having a slot (90) for receiving a web (13) of said first brake shoe (13) to prevent said first end (34) from rotating, said second end (34) having a slot (82) for receiving a web (15) of said second brake shoe (14) to prevent said second end (36) from rotating, said second end (34) having an arm (80) which extends in a plane substantially perpendicular to said slot (82), and in that said mechanical actuator (50) is characterized by a lever (52) having a first end (54) and a second end (56), said lever (52) being pivotally attached to said arm (80) in a plane substantially parallel with said web (15), said lever (52) having a variable surface (58) adjacent said second end (56) which engages said web (15), said first end (54) of said lever (52) on receiving said second input responding by rotating about said pivotal connection on said arm (80) to transmit an axial force through said variable surface (58) to said second brake shoe (14) by way of web (15) and through said adjustable strut mechanism (32) to said first brake shoe (12) by way of web (13) to effect said second brake application.