Patent ID: 6374962
Filing Date: 2002-04-23
Classification: F16D

Abstract:
In a drum brake assembly having first and second brake shoes retained on a backing plate, each of said first and second brake shoes respectively having a first end and a second end with said first end being connected to a hydraulic actuator assembly associated with said backing plate and said second end being connected to an anchor block associated with said backing plate, said first ends being spaced apart by a strut mechanism having a extendable shaft having a first end member with a slot therein that engages a first web of said first brake shoe adjacent said first end to prevent said first end member from rotating and a second end member with a slot therein that engages a second web of said second brake shoe adjacent said first end to prevent said second end member from rotating, first resilient means for urging said first and second brake shoes toward said anchor block and second resilient means for urging said first and second brake shoes toward said hydraulic actuator assembly, said first end member of said extendable shaft being separated from said second end member by a rotatable stem, said rotatable stem having a first cylindrical surface retained in a bore in said first end member, a second cylindrical surface that engages said first end member and a third cylindrical surface with first threads thereon which mate with second threads in said second end member, said rotatable stem being adjustable to move said first end member toward said first web and said second end member toward said second web to maintain a predetermined running clearance between a drum and a first friction member on said first brake shoe and a second friction member on said second brake shoe, said hydraulic actuator assembly responding to a first input to respectively move said first friction member and said second friction member into engagement with said drum to effect a first brake application and a mechanical actuator connected to said strut mechanism for providing a second input to respectively move the first and second friction members into engagement with said drum to effect a second brake application, said mechanical actuator being characterized in that said second end member of said extendable shaft is defined by a flat base having a substantially first oval shape that transitions into a cylindrical projection, said second threads being located in said cylindrical projection with said second slot being located in said flat base along an axis of said second threads, said flat base having a first hole located adjacent said second slot; a lever having a first end with a second flat base thereon offset from said second end, said second flat base having a ledge thereon with a second hole located adjacent said ledge; a pin that extends through said first hole and said second hole to maintain said first flat base and said second flat base in substantially parallel planes with said ledge engaging said second web and said second end of said lever being in a plane substantial parallel with said cylindrical projection of said second end member; and in that linkage attached to said second end of said lever on receipt of a linear force applied to said second end along a plane perpendicular to said cylindrical projection of said second end member causes said second flat base to pivot on said pin and transfer an axial force from said ledge into said second web substantially along said axis of said cylindrical projection to effect said second brake application.