Installation rod for an underground pipe installer device

A plurality of rigid steel rod sections for multiple coupled end to end arrangements, for use in an underground pipe installer device having reciprocating drive jaws to tightly engage said rod sections to form an underground hole between two given points in a first direction of operation by the pipe installer device and to withdraw a pipe, attached to a leading end of a coupled arrangement, into the length of the hole in a second direction of operation, said rod sections comprising a plurality of main predetermined rod section lengths of a substantially uniform predetermined outer diameter and including an axial outwardly extending reduced diameter threaded stud portion from each end of each rod section length, and an annular shoulder portion of a predetermined length and of a reduced diameter relative to said main length diameter and equal to the outer thread diameter of each said stud portion, and formed between said main length and the threaded stud portion;

• said threaded stud portion of each rod length being receivable in screw threaded engagement within one end portion of each of a plurality of standard rigid steel sleeve couplers which are provided and are of a same substantially uniform predetermined outer diameter as said main rod lengths and including a main mating continuously threaded interior portion along a main central length and terminating in an unthreaded open lead-in annular skirt portion at each end of a predetermined depth and diameter to receive one of said annular shoulders as a snug fit, the threaded stud and shoulder portions of each rod section length being receivable within each end of each of the couplers, each of said threaded studs being of such a length as to define a relatively short span between opposed end faces thereof of a length less than the length of the thread crests on said threaded studs when a plurality of rod lengths are fully threaded into each end of the couplers.