04850440 is referenced by 37 patents and cites 6 patents.

The head is carried by two flexible continuous drill pipes which surround each other and which are flexible enough to be uncoiled from a reel but which are still rigid enough almost not to get twisted in the ground on themselves or relative to each other during the operation of the head. The head is directed in the ground by means of fluid which is pumped through one of the pipes and wherewith the head is repelled relative to the wall of the already formed portion of the hole. One of the pipes connects to one or more directable spray nozzles on the front end of the head, the other one connects to one or more sidewise-issueing openings wherein preferably a directable spray nozzle is mounted.

Method and device for making a hole in the ground
Application Number
Publication Number
Application Date
August 10, 1987
Publication Date
July 25, 1989
Nic H W Smet
Kasteelstraat 29, B-2400 Mol
Stevens Davis Miller & Mosher
E21B 7/18
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