Patent ID: 6615957
Filing Date: 2003-09-09
Classification: F16D

Abstract:
A dual-mode drum brake assembly for a vehicle, comprising:a backing plate which is fixed to a body of the vehicle; first and second arcuate brake shoes which are disposed, substantially symmetrically with each other, on said backing plate such that said first and second arcuate brake shoes are movable toward and away from each other, said first and second arcuate brake shoes having a first pair of adjacent end portions each of which is provided by one of opposite end portions of a corresponding one of said first and second arcuate brake shoes and each of which is held by an anchor disposed on said backing plate, said first and second arcuate brake shoes further having a second pair of adjacent end portions each of which is provided by the other of said opposite end portions of a corresponding one of said first and second arcuate brake shoes; an actuator which is disposed on said backing plate such that said actuator is positioned between said second pair of adjacent end portions of said first and second arcuate brake shoes, and which is operable to move said second pair of adjacent end portions away from each other so as to force said arcuate brake shoes against a brake drum rotatable with a wheel of the vehicle so that the dual-mode drum brake assembly acts as a leading/trailing drum brake for generating a braking force for braking the wheel; an intermediate lever which is disposed substantially along said first arcuate brake shoe and which has an intermediate portion connected to an intermediate portion of a web of said first arcuate brake shoe such that said intermediate lever is pivotable relative to said web about a pivot axis that is substantially perpendicular to said backing plate, said web being provided by a flat plate portion of said first arcuate brake shoe which portion is substantially parallel to said backing plate; a second strut which is engaged at one end portion thereof with a first end portion of said intermediate lever, and associated at another end portion thereof with said second arcuate brake shoe; a positioning spring which positions said intermediate lever and said second strut in respective predetermined positions in which said intermediate lever and said second strut are held in engagement at respective engaging portions thereof with each other with said engaging portions lying on a plane that is tangent to said web, said engaging portions being provided by said first end portion of said intermediate lever and one of said opposite end portions of said second strut; a first strut which is engaged with one of said second arcuate brake shoe and a second end portion of said intermediate lever, said second end portion being located on one of opposite sides of said pivot axis which one is remote from said first end portion of said intermediate lever; a parking lever which is engaged with the other of said second arcuate brake shoe and said second end portion of said intermediate lever, said parking lever being operable to be pivoted so as to be brought into engagement with said first strut whereby said first and second arcuate brake shoes are moved away from each other by a link mechanism constituted by said first and second struts and said intermediate lever, so that the dual-mode drum brake assembly acts as a duo-servo brake for generating a braking force for braking the wheel; and a stopper on said intermediate lever which limits a displacement of said second strut relative to said intermediate lever in a direction away from said web and prevents disengagement of said second strut from said intermediate lever.