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.

Abstract: A releasable lock mechanism is provided in combination with a stationary first member and a second member, the latter being adapted to assume various selected positions of rotary adjustment with respect to the first member. The lock mechanism includes a first lock component carried by one of the members and a complemental pivotally adjustable second lock component carried by the other member. The first lock component has a rounded periphery which is provided with a plurality of annularly spaced pockets; each pocket corresponding to a selected position of rotary adjustment of the second member with respect to the first member. The second lock component assumes an interlocking engagement with a peripheral pocket, when the second member is disposed at a selected position of rotary adjustment with respect to the first member, and retains the second member in the selected position.

Abstract: A hydraulically actuated device secures the back end of a truck against a surface of a loading dock during loading and unloading of the truck. The device includes a self-aligning hydraulic cylinder which is adjustably mounted on the loading dock, and a piston mounted within the cylinder and having an exposed portion to which an attaching means is connected. The attaching means is adapted to be releasably connected to the truck. Control means is provided for directing hydraulic pressure to the cylinder so as to effect movement of the piston in one direction whereby the attaching means exerts a pulling force on the truck to cause the latter to be secured against the loading dock surface, or in a second direction whereby the attaching means assumes a position wherein it may be disconnected from the truck. Signal means, responsive to hydraulic pressure, is provided to indicate when hydraulic pressure is being, or not being, exerted on the piston.