초록 ▼

This underreamer has a lower body and a tubular upper body connected above it. A pair of extendible cutter arms are scissored in the lower body for pivoting between retracted and extended positions. A sleeve fixed to the lower body extends upwardly within the upper body with an outside diameter smal

This underreamer has a lower body and a tubular upper body connected above it. A pair of extendible cutter arms are scissored in the lower body for pivoting between retracted and extended positions. A sleeve fixed to the lower body extends upwardly within the upper body with an outside diameter smaller than the inside diameter of the upper body to leave a fluid flow annulus between the sleeve and upper body. A piston in the sleeve is axially movable from an upward position toward a lower position in response to application of fluid pressure through a drill string for pivoting the cutter arms from the retracted position toward the extended position. Passages through the lower body convey drilling fluid through the lower body from the annulus between the upper body and the sleeve. Such fluid is discharged outside the lower body adjacent to cutters on the cutter arms, into a pocket in the lower body occupied by the cutters in their retracted position, and through the lower end of the lower body.

대표청구항 ▼

An underreamer comprising: a lower body; a plurality of cutter arms mounted in the lower body for pivoting between a retracted position and an extended underreaming position; a tubular upper body connected above the lower body; a sleeve within the upper body and fixed to the lower body, at least a p

An underreamer comprising: a lower body; a plurality of cutter arms mounted in the lower body for pivoting between a retracted position and an extended underreaming position; a tubular upper body connected above the lower body; a sleeve within the upper body and fixed to the lower body, at least a portion of the sleeve having an outside diameter sufficiently smaller than the inside diameter of the upper body to leave a fluid flow annulus between the sleeve and upper body; a solid piston in the sleeve axially shiftable from an upper position to a lower position in response to application of fluid pressure; means connected to the piston for pivoting the cutter arms from the retracted position toward the extended position when the piston shifts toward the lower position; and passage means through the lower body for conveying fluid through at least a portion of the lower body from the annulus between the upper body and the sleeve.