JPS5594837A - Hydraulic booster - Google Patents

Abstract

PURPOSE: To generate an optimum braking force according to all vehicle load condition by a mechanism wherein a set load of a relief valve that decides the intensifying characteristic may made variable corresponding to an occasional condition of load weight.

CONSTITUTION: A hydraulic booster B allows the spool 12 to relatively displace against a power piston 3 by operating the brake pedal 28, a throttle valve 13 actuated by the relative displacement whereof may throttle the hydraulic oil volume fed from a port 7. Then, the oil of upper stream of the throttle valve 18 is delivered into a booster chamber 26 passing through a throttle valve 19, a hole 61, a space 72 and a hole 62 to act against the left surface of a power piston 3. In this case, the hydraulic port 40 of the booster B is connected with a pipe 60 in the midway of a pipe 59 connecting a control valve 53 of a fork lift and a lift cylinder 51 to apply the oil pressure within the cylinder 51 variable on the weight of the load W to the hydraulic chamber 39, which allows to vary the set load of a relief spring 34 of a relief valve 32.

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