Patent EP-3559497-A1 (EP)
Title: A device for adjusting the clearance of a drum brake
Inventor: WOLOSZYN TOMASZ
IPC: F16D63/00
Filed: 2017-12-15
Abstract: A device for adjusting the clearance of a drum brake (1) capable of avoiding the canceling of the minimum operating clearance also in case of repeated brakes without the wear of the shoes, and arranged between two shoes (2, 3) which cooperate with a braking surface (4) of a drum (5), said shoes (2, 3) are moved by an actuation device (6) which stresses them from a resting position, wherein the shoes (2, 3) are away from said braking surface (4) at least by a minimum operating clearance, to a braking position, wherein the shoes (2, 3) abut against said braking surface (4), wherein said clearance adjustment device (1) comprises an extensible strut assembly (7) arranged between the shoes (2, 3), which creates a reaction action on the shoes (2, 3) when stressed by a braking action applied by the actuation device (6); said extensible strut assembly (7) comprising: a piston (8) rotationally constrained to a first shoe (2); a support (9) rotationally constrained to a second shoe (3) and slidingly connected to said piston (8) making the strut (7) extensible to adjust the distance of said first and second shoe (2, 3); a toothed ring (10) rotational with respect to said piston (8) and abutting against said support (9), by rotating said toothed ring (10) applies an action on said piston (8) and on said support (9) thus extending said strut (7) and moving away said shoes (2, 3); and wherein said clearance adjustment device (1) further comprises: a lever assembly (11) having a first lever end (12) arranged in contact with one of said shoes (3) and biased in rotation by said shoe (3) when said shoe (3) is stressed by said actuation device (6); said lever assembly (11) rotating about a lever pin (12); and wherein said clearance adjustment device (1) further comprises a sliding guide (13) associated with said lever assembly (11) with at least one sliding guiding portion (14) thereof being inserted in the extensible strut assembly (7); said sliding guide (13) slides with respect to said extensible strut assembly (7) during the rotation of said lever assembly (11); said sliding guide (13) comprising a ratchet mechanism (14) which acts on said toothed ring (10) so as to turn said toothed ring (10) when said sliding guide (13) slides with respect to said extensible strut assembly (7) and when it exceeds a predetermined idle stroke (15) thereof of said ratchet mechanism (14) with respect to said toothed ring (10); wherein said coupling of said sliding guide (13) and said extensible strut assembly (7) makes the sliding of said sliding guide (13) possible when the reaction action (Fr), equal and contrary to the braking action (Ff), is lower than a predetermined threshold (Fs), thus allowing the ratchet mechanism (14) to run said idle stroke (15) and possibly actuate said toothed ring (10) extending said extensible strut assembly; and wherein said coupling of said sliding guide (13) and said extensible strut assembly (7) prevents the sliding of said sliding guide (13) when the reaction action (Fr), equal and contrary to the braking action (Ff), is higher than the predetermined threshold (Fs), thus allowing the ratchet mechanism (14), before reaching said threshold (Fs), to run said idle stroke, but, once reached said threshold (Fs), preventing the actuation of said toothed ring (10) and preventing the extension of said extensible strut assembly (15).