Loading dock and hydraulic system therefor

Abstract

A hydraulic system is provided for a loading dock installation wherein the latter has a plurality of independently operable dock levelers arranged in spaced relation along the loading dock. Each leveler includes a hingedly mounted deck member or ramp and a power unit for actuating the deck member to a predetermined upwardly inclined position from a horizontal cross-traffic position. The hydraulic system is provided with a common source of pressurized hydraulic fluid which is remotely disposed relative to the dock levelers. A primary line extends from the common source to each leveler. An adjustable control valve is provided for each leveler and includes a first port which is adapted to communicate with the primary line; a second port which is adapted to communicate with the power unit, and a third port which is adapted to communicate with a drain line. Each control valve is adapted to normally assume a first position of adjustment wherein the second and third ports are interconnected and the first port is blocked. When the control valve is adjusted to a second position of adjustment the first and second ports are interconnected and the third port is blocked thereby causing the deck member to be actuated to the predetermined upwardly inclined position.