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Brake torque limiter

  • US 4,296,897 A
  • Filed: 01/22/1979
  • Issued: 10/27/1981
  • Est. Priority Date: 01/22/1979
  • Status: Expired due to Term
First Claim
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1. A torque responsive brake control apparatus for controlling a fluid pressure operated brake mechanism, operatively connected to a rotatable member, comprising:

  • said fluid pressure operated brake mechanism being mounted substantially coaxial with said rotatable member and adapted for exerting a braking force to resist rotation of said rotatable member;

    a metering valve being manually operated for controlling a flow of pressurized fluid to said brake mechanism;

    a torque arm connected to said brake mechanism;

    said torque arm being angularly movable in response to brake reaction torque associated with said rotatable member when a braking force is applied to resist rotation of said rotatable member;

    said torque responsive control apparatus having a brake rod assembly attached at one end to said torque arm and attached at an opposite end to a fixed support;

    said brake rod assembly being arranged between said torque arm and said fixed support, for resisting angular displacement of said torque arm;

    a brake torque limiter incorporated within said brake rod assembly and being interposed in the fluid circuit between said manually operated metering valve and said brake mechanism, for controlling the supply and release of fluid under pressure to and from said brake mechanism;

    said brake torque limiter comprising a cylinder head section with a dual-diameter internally stepped cylinder section, and a matching dual-diameter stepped piston slidably mounted therein;

    said brake rod assembly comprising a first brake rod segment fixedly attached to said dual-diameter stepped piston, and a second brake rod segment fixedly attached to said dual-diameter stepped cylinder and head section of said brake torque limiter;

    a first chamber formed between said cylinder head section and said dual-diameter stepped piston;

    said brake torque limiter being constructed and arranged with respect to said brake rod assembly, so as to normally bias said brake rod assembly in one direction of extending said brake rod assembly to its maximum overall length, by directing fluid pressure from said manually operated metering valve into said first chamber, and in the opposite direction for decreasing the overall length of said brake rod assembly by torque resulting from application of brakes;

    a control valve incorporated within said brake torque limiter and interposed in the fluid circuit through which fluid under pressure from said manually operated metering valve, is supplied to the brake mechanism;

    said control valve being normally in an open position, when said brake rod assembly is at its maximum overall length, for circulating fluid pressure from said metering valve through said control valve to said brake mechanism;

    said control valve being actuated to a closed position, when said brake rod assembly is decreased from its maximum overall length by predetermined excessive braking torque of said rotatable member, for blocking fluid flow between said brake mechanism and said manually operated metering valve, and for trapping metered fluid pressure between said brake torque limiter and said brake mechanism;

    a second chamber formed between said step sections of the dual-diameter piston and matching internal dual-diameter cylinder, for creating an expanding annulus volume in response to contraction of the overall length of said brake rod assembly, to receive hydraulic fluid trapped between said brake torque limiter and said brake mechanism, and thereby decrease the pressure of said trapped hydraulic fluid resulting in a decrease in the ratio of brake torque reaction relative to metered hydraulic pressure.

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