US 5,310,028 A · S-cam for drum brake

Abstract

An S-cam assembly (33) is disclosed for expanding internal shoe brakes of the type comprising a pair of pivotally mounted brake shoes (17) located within a brake drum (11), each brake shoe carrying a cam follower (31). The assembly comprises an S-cam member (35) comprising a pair of substantially identical working portions (37), each working portion defining a working surface (39) and defining a nominal lift circle having a diameter D1. Each working portion includes a ramp member (43) pivotable about a pin (47) from a retracted position (FIG. 2) in which a ramp surface (51) is disposed within the nominal lift circle. Each ramp member has an extended position (FIG. 5) in which the ramp surface is disposed outward of the nominal lift circle and in engagement with the adjacent cam follower (31) and defining a larger lift circle having a diameter D2. The substantially increased reserve lift is accomplished without increasing the minimum installation diameter of the S-cam assembly.

Claims14

Dependent claims

A cam assembly for expanding internal shoe brakes of the type comprising a pair of pivotably mounted brake shoes located interiorly of a brake drum, each of said brake shoes carrying a cam follower urged into direct engagement with a cam member working surface, rotation of said cam assembly in a first direction of rotation from the fully disengaged condition forcing at least one of said brake shoes radially outwardly relative to said brake drum;

said cam assembly comprising a cam member pivotable about an axis of rotation (A), said cam member comprising a working portion, said working portion defining said working surface and further defining a nominal lift circle having a first diameter (D1), characterized by:
(a) said working portion including a ramp member movably fixed relative thereto;
(b) said ramp member defining a ramp surface and having a retracted position in which said ramp surface is disposed radially within said nominal lift circle thereby said ramp surface being out of engagement with said cam follower;
and
(c) said ramp member having an extended position in which said ramp surface is disposed radially outward from said nominal lift circle, and in direct engagement with its respective cam follower.

2 more elements

An S-cam assembly for expanding internal show brakes of the type comprising a pair of pivotably mounted brake shoes located interiorly of a brake drum, each of said brake shoes carrying a cam follower urged into direct engagement with a cam member working surface, rotation of said S-cam assembly in a first direction of rotation from the fully disengaged condition forcing said brake shoes radially outwardly relative to said brake drum;

said S-cam assembly comprising an S-cam member pivotable about an axis of rotation (A), said S-cam member comprising a pair of substantially identical working portions diametrically disposed about said axis of rotation (A), each of said working portions defining said working surface and further defining a nominal lift circle having a first diameter (D1), characterized by:
(a) each of said working portions including a ramp member movably fixed relative thereto;
(b) each ramp member defining a ramp surface and having a retracted position in which said ramp surface is disposed radially within said nominal lift circle thereby said ramp surface being out of engagement with said cam follower;
and
(c) each ramp member having an extended position in which said ramp surface is disposed radially outward from said nominal lift circle, and in direct engagement with one of said cam followers.

2 more elements

Dependencies are inferred from the claim text.

S-cam for drum brake

Life of this patent

S-cam for drum brake

Life of this patent

Abstract

Claims14