초록 ▼

A telescopic boom comprises inner and outer boom sections; an elongated rotatable screw rotatably mounted on the outer section; a first thread on the screw engaged with a first nut on the inner boom section whereby screw rotation effects telescopic movement of the inner boom section and a second thr

A telescopic boom comprises inner and outer boom sections; an elongated rotatable screw rotatably mounted on the outer section; a first thread on the screw engaged with a first nut on the inner boom section whereby screw rotation effects telescopic movement of the inner boom section and a second thread of smaller lead superimposed on the first thread and engaged with a second nut mounted on a support which is movably mounted on the outer boom section whereby screw rotation also effects axial movement of the support at a slower rate than telescopic movement of the boom sections to a position wherein it supports the mid-section of the screw.

대표청구항 ▼

In a telescopic boom: a pair of relatively movable boom sections; an elongated rotatable screw rotatably mounted on one boom section; a primary thread on said screw engaged with a primary nut on the other boom section whereby screw rotation effects relative telescopic movement of said boom sections;

In a telescopic boom: a pair of relatively movable boom sections; an elongated rotatable screw rotatably mounted on one boom section; a primary thread on said screw engaged with a primary nut on the other boom section whereby screw rotation effects relative telescopic movement of said boom sections; a secondary thread on said screw of different lead than said first thread and engaged with a secondary nut; and a support connected to and movable with said secondary nut, said support being movably mounted on one of said boom sections whereby said screw rotation also effects axial movement of said support at a different rate than said telescopic movement of the boom sections to a supporting position wherein it supports said screw intermediately thereof.