04921057 is referenced by 12 patents and cites 5 patents.

The head is carried by two flexible continuous drill pipes which surround each other and which are flexible enought 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 wich 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.

Title
Method and device for making a hole in the ground
Application Number
83191
Publication Number
4921057
Application Date
May 1, 1989
Publication Date
May 1, 1990
Inventor
Nic H W Smet
Kasteelstraat 29, B - 2400 Mol
BE
Agent
Stevens Davis Miller & Mosher
IPC
E21B 7/18
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