CA2059747A1 - Self-releasing lift hook - Google Patents

Abstract

A self-releasing lift hook includes a main cylinder with a main piston slidable in the cylinder and defining a main chamber above the piston and a main chamber below the piston. A hook is connected to one of the cylinder and the piston, and a lift ring is connected to the other. A coil spring biases the piston in a direction which causes the hook and the ring to approach each other, so that when a load is placed on the hook, the hook and ring move apart and cause energy to be stored in the spring. A main passage through the piston, incorporating a check valve, allows fluid to flow between the main chambers when the hook and ring are moving apart, but restrains such fluid flow when the hook and ring approach each other. A bleed passage is provided through the piston to allow slow transfer of fluid from one side to the other of the piston. A
hydraulic accessory is activated by an increase of fluid pressure in the chamber that decreases in volume when the hook and ring approach each other, and a mechanical connection, activated by the hydraulic arrangement, causes a load attachment to be disengaged from the hook.