|
US2420059A
|
|
Skeleton mast having legs circular in cross section
|
|
US2389226A
|
|
Fast sheave mounting for oil well masts
|
|
US2365370A
|
|
Mast base
|
|
US2363106A
|
|
Mast structure and method of erection
|
|
US2380094A
|
|
Oil well derrick structure
|
|
US2332479A
|
|
Mast structure
|
|
US2271577A
|
|
Collapsible mast
|
|
US2271578A
|
|
Collapsible mast erection
|
|
US2293958A
|
|
Narrow bottom tiltable mast
|
|
US2300480A
|
|
Folding derrick base
|
|
US2166406A
|
|
Chain adjuster
|
|
US2210408A
|
|
Marine working platform substructure
|
|
US2210407A
|
|
Portable derrick
|
|
US2200775A
|
|
Derrick
|
|
US2225561A
|
|
Derrick
|
|
US2143734A
|
|
Spool arm
|
|
US2050318A
|
|
Beam hanger
|
|
US2016716A
|
|
Ball and socket bearing
|
|
US2053790A
|
|
Ball and socket bearing
|
|
US1867016A
|
|
Walking beam
|
