Pallet truck with hydraulic lift
AssigneeEquipment Company of America
InventorTuval Kedem
Life of this patent
Estimating the term…
Abstract
A pallet truck hydraulic jack has a base plate mounting a lift cylinder with a reciprocal piston or lift rod and a pump cylinder with a reciprocal pump piston. A cartridge type directional control valve assembly within the base plate controls the flow of pressurized hydraulic fluid in respective manifold passages so that manual actuation of the pump effects a quick lift of the frame when it is unloaded, effects an additional application of lifting force through the lift cylinder when the frame is loaded, bypasses pressurized hydraulic fluid to the reservoir when the frame is overloaded, and provides a release of pressurized hydraulic fluid from the pump cylinder and the lift plunger and returns it to the reservoir for lowering the frame and forks.
Claims8
A hydraulic control system comprising a base plate forming a manifold, a lift cylinder mounted upon the base plate having therein a reciprocal rod and lift piston, and a pump cylinder mounted upon the base plate having an outlet and a reciprocal pump piston projecting therefrom;
- a hydraulic control mechanism including a body depending from the base plate having an elongated bore extending axially of and communicating with said lift cylinder;
- a plunger piston positioned within said body and projecting from said bore and at one end abutting said lift piston;
- there being a first passage in said base plate interconnecting said pump cylinder outlet and said bore;
- a reservoir mounted upon said base plate containing hydraulic fluid and having a first outlet communicating with said first passage for feeding hydraulic fluid into said pump cylinder on movement of said pump piston in one direction during its suction stroke;
- first valve means within said base plate blocking pressurized hydraulic fluid from said reservoir first outlet;
- movement of said pump piston in the opposite direction feeding pressurized hydraulic fluid through said first passage to said bore thereby moving said plunger piston and said lift piston and rod;
- said reservoir having a second outlet;
- there being a second passage in said base plate at one end communicating with said second outlet and at its other end communicating with said lift cylinder;
- and a normally seated valve means within said second passage;
- the movement of said lift piston and rod drawing hydraulic fluid from said reservoir through said second passage into said lift cylinder.
Dependencies are inferred from the claim text.