| 摘要 |
The drum brake comprise two shoes (12, 14) equipped with friction elements (24, 26) capable of being urged into frictional engagement by an applying mechanism (28) arranged between two first ends (30, 32) of the shoes (12, 14), a fixed anchor block (34) disposed between the other two ends (36, 38) of the shoes, a spacer (44) mounted near the applying mechanism (28) and bearing at each end on one of said shoes, the spacer (44) including a device which lengthens automatically as a function of wear of the friction elements and constituted by a screw-nut system (58, 60) controlled by a pawl (76) mounted on an articulated arm (62) acting on a ratchet wheel (58). The deflectin of arm (62) and pawl (76) is an amplitude which increases as the distance between the drum and shoes increases, with the articulated arm (62) including an auxiliary portion (78) also acting on the ratchet wheel (58) when deflection of the articulated arm (62) reaches a predetermined displacement, whereby there is an increase in the rate at which the shoes are brought nearer to the drum.
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