| 摘要 |
A rotary drill bit includes a cutting face (24) having a peripheral edge (26) and a central recess (28). A plurality of fluid discharge nozzles (18) are mounted in the cutting face (24). A plurality of cutter elements (14) are mounted in the peripheral edge (26) and in the recess (28) to fracture an earthen core formed as the drill cuts through a formation. A plurality of lateral discharge passages (36) extend radially through the bit body (10) from said recess (28) and extend longitudinally to the peripheral edge (26) to form circumferential interruptions in the peripheral edge (26). A convex protrusion (34) is diposed centrally at a longitudinally inner end of the recess (28) and includes a convex deflecting surface (40) arranged to contact and fracture the earthen core and deflect the cuttings to the lateral discharge passages (36). A ridge (50) is disposed along a trailing edge of each of the discharge passages (36) to retard the flow of drilling fluid into the associated discharge passage (36) from an adjacent one of the nozzles (18), whereby such fluid is caused to flow across cutter elements (14) located behind the ridges (50). |
