High-visibility two-stage mast assembly for lift trucks

摘要

A high visibility telescopic mast assembly for lift trucks having a pair of mutually reciprocable mast sections, a load carriage movably mounted thereon and a fluid actuated extensible-contractable fluid ram assembly for selectively lifting the load carriage and one of the mast sections with respect to the other mast section. The fluid ram assembly is mounted centrally between the uprights of the respective mast sections and is contractable to a height adjacent the longitudinal midpoint of the fully contracted mast so as to provide relatively unimpeded visibility over the top of the ram assembly between the uprights when the mast is contracted. The ram assembly is connected to the extensible mast section in such a way that the ram begins to lift the mast section at a speed identical to the speed of ram extension while the ram assembly is still substantially fully contracted. Two alternative embodiments of the invention are disclosed, one featuring no free-lift and one featuring partial free-lift of the load carriage.