Patent ID: 7249660
Filing Date: 2007-07-31
Classification: F16D

Abstract:
1. A brake assembly for a vehicle having a drum that is rotatable about an axis with an inner cylindrical surface thereon defining a braking surface for first and second friction surfaces on first and second brake shoes that are moved from a position of rest by actuation means to effect a desired brake application, said brake assembly being characterized by said actuation means including a first cylindrical body that is fixed to a stationary member of the vehicle, said first cylindrical body having a first bore that extends from a second end toward a first end with a first groove therein and a first chamfer on a first wall of the first groove, a first seal located in said first grove, a first piston located in said first bore engages said first seal to define a first chamber in said first cylindrical body, and a second cylindrical body that is fixed to a stationary member of the vehicle, said second cylindrical body having a second bore that extends from a second end toward a first end with a second groove therein and a first chamfer on a first wall of the second groove, a second seal located in said second groove, a second piston located in said second bore engages said second seal to define a second chamber in said second cylindrical body; and first brake shoe having a first web with first end and a second end with said first end thereof being pinned to said first end of said second cylindrical body and a second end connected to said first piston through a first linkage; and said second brake shoe having a second web with a first end thereof pinned to said first end of said first cylindrical body and a second end connected to said second piston through a second linkage, said first piston and said second piston on pressurized fluid being presented to said first and second chambers respectively responding by moving from positions of rests by said first web on said first brake shoe pivoting about said first end of said second cylindrical body to move said first frictional surface thereon toward and into engagement with said braking surface and by said second web on said second brake shoe pivoting about said first end of said first cylindrical body to move said second frictional surface thereon toward and into engagement with said braking surface to effect the brake application, said first seal on movement of the first piston from its position of rest having a first portion thereof that resiliently moves into said first chamfer in said first bore and said second seal on movement of the second piston from its position of rest having a second portion thereof that resiliently moves into said second chamfer in said second bore and on termination of the presentation of pressurized fluid to said first chamber and said second chamber said first portion of said first seal acts on said first piston and said second portion of said second seal acts on said second piston to return said first and second piston to positions of rest to set a running clearance between said first and second friction surfaces and said braking surface, said reaction forces derived during a brake application are carried into said stationary member through a first pin connected to said first end of said first cylindrical member and a second pin connected to said first end of said second cylindrical member, said first and second cylindrical members being symmetrically positioned with respect to the axis of said drum, said first linkage is defined by a first shaft having a first end pivotally secured to said first piston and a second end that is pivotally secured to said second end of said first web and said second linkage is defined by a second shaft having a first end pivotally secured to said second piston and a second end that is pivotally secured to said second end of said second web, said brake assembly is further characterized by an arcuate strut having a first end connected to said second end of said first linkage and a second end connected to said second end of said second linkage such that movement of said second end of said first piston provides a first force that pulls said second end of said second piston and movement of said second end of said second piston provides a second force that pushes said second end of said first piston during a brake application.