and risking damage both to the workers and to the threads.
Cross-threaded pipes and injuries have occurred. Thus, this prior art approach is both wasteful and dangerous, as well.
Installation of such risers, must also accommodate a pull cord that is inserted through the riser before lifting. Such a pull cord has a free upper end for the workers use and, in turn, is connected to an electrical power cable at the lower end. That pull cord, after the riser sections are joined together, is pulled through the assembled sections in order to retrieve and advance the electrical power lines which must also be lifted through the installed riser pipes. In the prior art this cord became entangled in the rope slings as the twisting was taking place.
Each riser installationunusual benefits of the subject invention.
The specific areas of search included:
Class 294 sub-classes 90, 91, 82.14, 82.15 and 82.16 PA1 Class 24 sub-classes 317 and 24.
The search turned up several patents of interest. The patents found for review are:
______________________________________ 4,221,252 September 9, 1980 Bruce 2,519,288 August 15, 1950 Roberson 4,188,141 February 12, 1980 Stoot 14,253 January 23, 1917 Wigle 1,436,621 November 21, 1922 Coultas 1,798,296 March 31, 1931 Yerkes 2,149,938 March 19, 1936 Hickman ______________________________________
A brief discussion of this art follows: Taking the patents of the search in the order listed above:
U.S. Pat. No. 4,221,252 Sep. 9, 1980 Bruce
Bruce is simply a well known shackle apparatus. The primary emphasis of the Bruce patent concerns the manner of locking nut 5 to the shaft 6. Plastic locking pins and