Patent ID: 6044938
Filing Date: 2000-04-04
Classification: F16D

Abstract:
A dual-mode drum brake assembly for a vehicle wheel, comprising:a stationary backing plate in the form of a generally circular disc opposed to an opening of a brake drum rotated with the vehicle wheel;a wheel cylinder which is open at opposite ends thereof and which is disposed on a radially outer portion of said backing plate such that an axial direction of said wheel cylinder is tangential to a circumference of said backing plate, said wheel cylinder having a pair of pistons which are extendible outwardly from said opposite ends;an anchor fixed to a circumferential portion of said backing plate which is diametrically opposite to said radially outer portion;two brake shoes which are supported by said backing plate movably in a plane parallel to a plane of said backing plate, said two brake shoes having a first pair of adjacent ends opposed to said opposite ends of said wheel cylinder, and a second pair of adjacent ends opposite to said first pair and opposed to respective opposite ends of said anchor;a parking lever disposed substantially along one of said two brake shoes, and having a pivot axis at a portion thereof closer to said wheel cylinder than to said anchor, and a cable fixing portion at a free end portion thereof closer to said anchor than to said wheel cylinder, said pivot axis being perpendicular to the plane of said backing plate; anda link mechanism disposed between said parking lever and said two brake shoes, and operating to move said adjacent ends of said second pair of said two brake shoes away from each other, with a pivotal movement of said parking lever about said pivot axis, at least when a torque acts on said brake drum, and said link mechanism enabling the dual-mode brake assembly to act as a duo-servo brake at least when said torque acts on said brake drum,and wherein said one and the other of said two brake shoes consist of a first brake shoe and a second brake shoe, respectively, and said link mechanism includes:an intermediate lever having an intermediate portion connected to an intermediate portion of said first brake shoe such that said intermediate lever is pivotable about a pivot axis perpendicular to the plane of said backing plate, said intermediate lever including a first arm extending from said intermediate portion in a direction toward said wheel cylinder, and a second arm extending from said intermediate portion in a direction toward said anchor, said parking lever being connected to said first arm pivotally about said pivot axis of said parking lever;a first strut operatively associated at opposite end portions thereof respectively with portions of said first and second brake shoes which are closer to said wheel cylinder than to said anchor, said first strut being engageable with a portion of said parking lever between said pivot axis and said free end portion; anda second strut operatively associated at opposite end portions thereof respectively with said second arm of said intermediate lever and a portion of said second brake shoe which is closer to said anchor than to said wheel cylinder.