Patent ID: 6131711
Filing Date: 2000-10-17
Classification: F16D

Abstract:
A duo-servo drum brake comprising: a primary shoe and a secondary shoe which are disposed opposite to each other inside a brake drum, counter braking force acting on the primary shoe being used for pressing the secondary shoe against the brake drum; and an anchor pin disposed forward further than the secondary shoe in the direction in which the brake drum is rotated forward and used for receiving the counter braking force, further including:a shoe expanding mechanism having a first link for pressing the primary shoe against the brake drum and a second link for pressing the secondary shoe synchronously when the first link presses the primary shoe;a control lever which is held around the anchor pin and when its end portion on one side receives counter braking force acting on the secondary shoe, its end portion on the other side is capable of swinging around the anchor pin in the direction of the secondary shoe;a balance link which is pivotally supported with the secondary shoe in a manner capable of swinging, has a contact surface in one end portion with the other end portion of the control lever and a contact surface in the other end portion with a pressing portion of the second link, and swings when the pressing force received with the contact surface in the one end portion from the control lever exceeds the pressing force received with the contact surface in the other end portion from the second link; anda projected portion which is provided for the first link and when the other end portion of the control lever is displaced toward the secondary shoe after swinging the balance link, engages with the secondary shoe in order to reduce the pressing force of the first link.