Lift truck mast

Claim 1

A load lifting mast for use on a vehicle comprising a pair of primary upright sections and a pair of secondary upright sections telescopingly nestled in slidable relation to each other, said primary upright sections including a base section and carriage section, said secondary upright sections including a base section and a lift section, means supporting said base upright section of said secondary upright sections on said vehicle, a load carriage slidably mounted on said primary carriage upright section, a primary hydraulic expansion unit including a primary hydraulic lift cylinder connected between said primary base section and said carriage section to telescope said primary sections relative to each other, a flexible member connected between said primary base section and said carriage and sheave means on said carriage section for lifting said carriage relative to said carriage section when said primary sections are extended, a secondary expansion unit comprising a secondary hydraulic lift cylinder positioned between said secondary base section and a secondary lift section for telescoping said secondary sections, a flexible member connected between said secondary base section and said primary base section and sheave means on said lift section for lifting said primary sections when secondary sections are extended, a hydraulic system including a control valve mounted on said vehicle, a source of pressurized fluid for supplying pressurized fluid to said control valves, a conduit means connecting said control valve to said primary and said secondary hydraulic lift cylinders, said valve thereby providing means for controlling the expanding of said primary hydraulic lift cylinder and said secondary hydraulic lift cylinder for extending said mast.