Hydraulic system with an unloading valve

摘要

A relief valve in a hydraulic system in a machine selectively sends pressurized oil to both a brake cooling apparatus and a cylinder used to hoist a load. A relief valve lowers pressure spikes in a brake cooling line by dumping fluid in a brake cooling line to tank responsive to a pressure spikes at the head end of the cylinder during hoisting or other transitions in the hydraulic system. Reducing the pressure spikes in the brake cooling line improves reliability of the brake cooling apparatus by protecting seals from undue stresses.

主权项

1. A hydraulic system comprising:
a hoist cylinder having a rod end and a head end; a brake cooler having a brake cooler port configured to receive dispelled fluid from the rod end in response to pressurized fluid being directed to the head end to extend the hoist cylinder; and an unloading relief valve in fluid communication with the rod end and the brake cooler port, the unloading relief valve being movable between a biased first position and a second position, in response to fluid being dispelled from the rod end to the brake cooler port and pressurized fluid being directed to the head end, the unloading relief valve is movable to the second position based on a signal pressure of the head end to allow the dispelled flow from the rod end to flow to a tank.