1
Nic H W Smet: Method and device for making a hole in the ground. Stevens Davis Miller & Mosher, July 25, 1989: US04850440 (37 worldwide citation)

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 ...


2
Nic H W Smet: Method and device for making a hole in the ground. Stevens Davis Miller & Mosher, May 1, 1990: US04921057 (12 worldwide citation)

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 i ...


3
Nic H W Smet: Apparatus for making a subterranean tunnel. Stevens Davis Miller & Mosher, April 25, 1989: US04823888 (7 worldwide citation)

The invention provides apparatus for making a tunnel. A flexible tube connects to a head consisting of a body and a nose mounted for movement thereon. The nose has an abutment face adjustable in position relative to said body, and carries a nozzle. The nose may be a bevelled cylinder which may be ro ...