| 摘要 |
A fluid cutting head (8) of the type having a plurality of nozzles in a rotatable nozzle assembly (9) for cutting a bore hole in rock, has nozzles being arranged to be supplied with high pressure drilling fluid, forming jets positioned to cut adjacent rock. The nozzles include one or more generally axially facing pilot nozzles (1 and 2) and one or more generally radially facing reaming nozzles (3, 4, 5 and 6), at least the pilot nozzles being characterised by a non-tapering outlet section such that the jet issuing therefrom is of substantially constant cross-section in a zone immediately adjacent the outlet section. The pilot nozzles are located in a leading part (26) of the rotatable nozzle assembly (9), having a minimised diameter, while the reaming nozzles are located in the following part (27) of the rotatable nozzle assembly (9), formed in a step-wise fashion to keep the reaming nozzles close to the rock face. |
