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
Smet Nik: Method and device for making a hole in the ground.. Smet Nik, February 24, 1988: EP0256601-A1 (6 worldwide citation)

The head (13,14) is carried by two flexible continuous drill pipes (4 and 5) 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 ...