Duo-servo drum brake

A duo-servo drum brake comprising a brake drum and a mechanical expander and thrust bearing assembly for supporting a pair of brake shoes, the expander having an operating lever to which an operating force is transferred from an actuator substantially in a direction tangential to an edge of the brake drum, at least one of said brake shoes being movable in response to the expander in the direction of the actuating force, said one of said brake shoes being biased with respect to a thrust bearing by a first spring, an end of said first spring being mounted at one end upon a fixed member, a spring force of which, in the direction of the expanding force of the expander, acts upon said one of said brake shoes, and a retractor spring interconnecting the brake shoes disposed substantially in parallel to said first spring.

A duo-servo drum brake having a pair of brake shoes which at one end are biased together by retractor springs and separated by an expander and thrust bearing, said brake shoes being adapted to be forced outwardly against the bias of said retractor springs with respect to said thrust bearing against a brake drum in response to an actuating force applied to said expander, comprising a prestressed spring disposed substantially in parallel with said retractor springs between one of said brake shoes and a fixed member for restricting movement of said one of said brake shoes with respect to said thrust plate to prevent said one brake shoe from striking said thrust bearing.

A duo-servo drum brake comprising a brake drum and a mechanical expander and thrust bearing assembly for supporting a pair of brake shoes, the expander having an operating lever to which an operating force is transferred from an actuator substantially in a direction tangential to an edge of the brake drum, at least one of said brake shoes being movable in response to the expander in the direction of the actuating force, said one of said brake shoes being connected to a thrust bearing by a prestressed spring, a spring force of which, in the direction of the expanding force of the expander, acts upon said one of said brake shoes, wherein the prestressing force of the spring is greater than the force of a retractor spring assembly operative in parallel to the expander between the brake shoes.

A duo-servo drum brake having a pair of brake shoes which at one end are biased together by retractor springs and separated by an expander and thrust bearing, said brake shoes being adapted to be forced outwardly against the bias of said retractor springs with respect to said thrust bearing against a brake drum in response to an activating force applied to said expander, comprising a restricting means for restricting movement of one of said brake shoes with respect to said thrust plate to prevent said one brake shoe from striking said thrust bearing, wherein said restricting means includes a biasing means disposed between said one brake shoe and said thrust bearing.