Pressure seal for pumping instruments through drill rod

Claim 1

In a system for taking surveys of borehole conditions in a generally horizontal borehole being drilled, said system comprising a drill rod, a survey probe in the drill rod adapted to be pumped through the drill rod and retrieved by reeling in a cable attached to the probe, a pump for pumping fluid through the drill rod to force the survey probe therethrough, a rotary motor between the pump and the drill rod, and a pipe extending from the rotary motor in alignment with the drill string; the improvement wherein a sealing device positioned between said pipe and said drill rod is provided, said sealing device comprising: (a) a housing having a central flow passage therethrough and an enlarged recessed opening in each end therethrough, said housing being of split construction and having two half sections; (b) a first seal in one end of said housing adapted to sealingly engage said drill rod when pressed thereagainst; (c) a second seal in the other end of said housing adapted to sealingly engage said pipe when pressed thereagainst; (d) an instrument cable entrance opening extending from outside said housing to said flow passage, said opening being bisected by the connecting plane of said two half sections, said opening being at an acute angle with respect to said flow passage; and (e) packing means in said opening allowing movement of an instrument cable therethrough and preventing leakage therefrom.