Extensible and collapsible portable derrick

Details Extensible and collapsible portable derrick Extensible and collapsible portable derrick

1975-02-07

1976-09-07

Spar, Robert J.

Traversing hoists

Overhead

Cable

214 75H, 212 28, 212 55, 187 2, B60P 146, B66P 2300, B66C 2362

Patent

active

039789896

ABSTRACT:
An extensible and collapsible portable derrick in which the various parts are made from a light weight metal and in which the parts can be disassembled and arranged in compact units, light enough in weight and small enough in size to be readily transportable by a person. The device is primarily designed to be used by operators who use tar paper and gravel for covering flat roofs of buildings whether or not the roofs are provided with parapets.

REFERENCES:
patent: 380206 (1888-03-01), Kane
patent: 733469 (1903-07-01), Dunbrook et al.
patent: 935413 (1909-09-01), Ryan et al.
patent: 1345008 (1920-06-01), Hill
patent: 2292353 (1942-08-01), Ennis et al.
patent: 2516364 (1950-07-01), Caddell
patent: 2661854 (1953-12-01), Adams
patent: 2804216 (1957-08-01), Farnam
patent: 2896908 (1959-07-01), Stone
patent: 3845869 (1974-11-01), Sowers et al.
patent: 3854594 (1974-12-01), Brooks

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