S-cam for drum brake
AssigneeEaton Corporation
InventorGeorge P. Mathews
Life of this patent
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Abstract
An improved S-cam (100) for expanding internal shoe (20) drum brakes (10) is provided. The working surfaces (116) of the S-cam are provided at their ends with an extremely high rise/low mechanical advantage portion (122) providing a warning ramp to indicate to the operator that brake relining is required and to minimize the possibility of cam flip.
Claims10
An S-cam member (100) for expanding internal shoe brakes (10) of the type comprising a pair of pivotably mounted brake shoes (20) located interiorly of a brake drum (12), each of said brake shoes carrying a cam follower (42) urged into engagement with a cam member working surface (116), rotation of said cam member in a first direction of rotation (112) from the fully disengaged condition of said brake forcing said brake shoes radially outwardly relative to said brake drum and rotation in the opposite direction of rotation (114) causing radial return of said brake shoes relative to said brake drum, each of said working surfaces comprising a first portion (118) engaged by said followers in the fully disengaged condition of said S-cam member and a second portion (120) extending from said first portion in substantially said opposite direction of rotation, said second portion of a substantially involute spiral shape in cross-section to provide a substantially constant first rate of lift, said S-cam characterized by:
- a third portion (122) of each of said working surfaces extending in substantially said opposite direction of rotation from said second portion, said third portion defined by a generally straight radially outwardly extending line in cross-section having a second rate of lift substantially greater than said first rate of lift.
Dependencies are inferred from the claim text.