Patent ID: 9528323
Filing Date: 2016-12-27
CPC Classification: E21B

Claim Text:
1. A fluid drilling head for drilling a bore hole through rock, said fluid drilling head having: a rotatable nozzle assembly incorporating a plurality of nozzles arranged to form fluid jets when provided with a supply of fluid under pressure, said fluid jets including one or more pilot jets directed in the general direction of movement of the fluid drilling head and one or more reaming jets directed generally radially and arranged to enlarge the initial hole formed by the pilot jets, and a gauging ring located behind the rotatable nozzle assembly and sized to the intended diameter of the bore hole, said gauging ring being arranged to slide axially relative to the rotatable nozzle assembly between a rearward position where each reaming jet is exposed, and a forward position where some or all of the reaming jets are shrouded by the gauging ring so as to be inoperable beyond a point of obstruction by the gauging ring.