Hydraulic lorry hoist ram control system - has circuit by-passing variable quantity from pump outlet back to tank

摘要

A passage leading to the ram is connected either to a pump delivering fluid under pressure, or to a return reservoir. Fluid pressure at the pump outlet is regulated by a control circuit which bypasses a variable amount of fluid back to the reservoir. The control circuit can incorporate one or more ball-valves thrust against their seats by springs whose loadings are varied by hand control levers. The ram can be double-acting, connected to two supply passages, one of which is connected to the pump and the other to the return pipe as desired.