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An improved method of lifting a load includes supporting a load on a first section of an extendible lift assembly, the first section being surrounded by a second section, a hydraulic cylinder being operatively coupled to the first section so as to be capable of lifting the first section, and the fir

An improved method of lifting a load includes supporting a load on a first section of an extendible lift assembly, the first section being surrounded by a second section, a hydraulic cylinder being operatively coupled to the first section so as to be capable of lifting the first section, and the first and second sections being supported on and vertically extendible with respect to a base. Then, while the load is supported on the first section, the hydraulic cylinder is extended to extend the first section relative to the second section and the base, thereby lifting the load to a first height. Then, the first section is secured to the second section so as to at least substantially prevent downward movement of the first section relative to the second section. The cylinder is then retracted and operatively coupled to the second section. Then, while the load is supported on the first section, the hydraulic cylinder is extended to extend the first and second sections relative to the base, thereby lifting the load to a second height which is higher than the first height. This procedure results in lifting the load through a range which is greater than a maximum range of extension of the hydraulic cylinder. The lift assembly also includes a locking device which, in the event of hydraulic pressure loss in the hydraulic cylinder, automatically mechanically engages one of the first and second sections to prevent unintended lowering of the load.

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[ I claim:] [1.]1. In a gantry including first and second extendible leg assemblies and a beam extending between and supported on said extendible leg assemblies, each said extendible leg assembly comprising: a base; a plurality of telescoping sections, each having an upper end and a lower end, mount

[ I claim:] [1.]1. In a gantry including first and second extendible leg assemblies and a beam extending between and supported on said extendible leg assemblies, each said extendible leg assembly comprising: a base; a plurality of telescoping sections, each having an upper end and a lower end, mounted on said base for vertical extension relative to said base, said plurality including an innermost section, an outermost section and an intermediate section immediately adjacent said innermost section; a hydraulic cylinder having a cylinder end and a rod end, disposed within said telescoping sections with said cylinder end uppermost and said rod end lowermost, said cylinder end having a coupling device being coupleable with and decoupleable from said innermost section, a detachable connection for detachably coupling said cylinder end to said adjacent intermediate section so that said cylinder end can be coupled to either said innermost section or to said adjacent intermediate section; and a selectively engageable connection between said lower end of said innermost section and said upper end of said adjacent intermediate section for detachably fixing said innermost section and said adjacent intermediate section to each other with said innermost section being extended relative to said adjacent intermediate section; said extendible leg assembly thereby being extendible over a range that is greater than the available extension of said cylinder, wherein said detachable connection includes coaxially alignable holes formed in said cylinder end and said intermediate section and further includes a pin insertable through said holes in said cylinder end and said intermediate section when said holes in said cylinder end and said intermediate section are coaxially aligned holes, a method comprising:(A) supporting a first end of said beam on said innermost section of said first extendible lift assembly;(B) supporting a second end of said beam on said innermost section of said second extendible lift assembly;(C) supporting said load on said beam and coupling said hydraulic cylinders to said innermost sections; then(D) while said load is supported on said beam, extending said hydraulic cylinders to extend said innermost section of each of said lift assemblies relative to said intermediate section and said base of each of said lift assemblies, thereby lifting said load to a first height; then(E) while said load is supported on said beam and said innermost section of each of said lift assemblies is extended relative to said intermediate section, detachably securing said innermost section of each of said lift assemblies to said intermediate section of each of said lift assemblies so as to at least substantially prevent downward movement of said innermost section of each of said lift assemblies relative to said intermediate section of each of said lift assemblies, the detachably securing step comprising, for each of said lift assemblies, detachably fixing said lower end of said innermost section to said upper end of said intermediate section using said detachably engageable connection; then(F) while said load is supported on said beam, decoupling said hydraulic cylinders from said innermost sections, retracting said hydraulic cylinders, and detachably connecting said hydraulic cylinder of each of said lift assemblies to said intermediate section of each of said lift assemblies using said detachable connection; and then(G) while said load is supported on said beam, extending said hydraulic cylinders to extend said innermost and intermediate sections of each of said lift assemblies relative to said base of each of said lift assemblies, thereby lifting said load to a second height which is higher than said first height, wherein the steps (D) and (G), in combination, lift said load through a range which is greater than a maximum range of extension of said hydraulic cylinders.