Rotary drill bit

A rotary drill bit for cutting in earth formations, comprising:

• a bit body including a cutting face having a central recess extending longitudinally inwardly,
• a plurality of fluid discharge nozzles mounted in said recess for emitting drilling fluid under pressure,
• a plurality of cutter elements mounted in said recess to fracture an earthen core formed as the drill cuts through the formation,
• a plurality of lateral discharge passages formed in said body, said passages extending completely radially through said body from said recess, and extending longitudinally to a forward end of said bit body,
• a convex protrusion disposed centrally at a longitudinally inner end of said recess for fracturing the earthen core and displacing the cuttings to said discharge passages, and
• a plurality of ridges disposed along trailing edges of said passages, said ridges extending along said recess and projecting outwardly from said cutting face to retard the flow of fluid into the associated passage from said nozzles, whereby such fluid rebounds and flows across cutter elements mounted behind respective ridges.

A rotary dill bit for cutting earth formations, comprising:

• a bit body rotatable about its longitudinal axis and including a cutting face having a peripheral edge and a central recess extending longitudinally rearwardly from said peripheral edge, said recess including side walls facing said longitudinal axis, said side walls being inclined with respect to said axis so as to approach said axis in a rearward direction, said peripheral edge and said side walls having recesses therein,
• a plurality of cutter inserts, some of which being mounted in said recesses in said peripheral edge, and others of which being mounted in said recesses in said side walls to fracture an earthen core formed as the drill cuts through the formation,
• a plurality of generally forwardly directed fluid discharge nozzles mounted in said cutting face for emitting pressurized drilling fluid into said central recess, said nozzles being oriented to direct drilling fluid along said side walls and said peripheral edge and across said cutter elements to flush and cool said cutter elements,
• at least one of said cutter inserts in said side walls being situated at least as far rearwardly in said recess as said nozzles,
• a plurality of lateral discharge passages formed in said body, said passages extending radially through said body from said central recess and extending longitudinally to said peripheral edge to form circumferential interruptions in said peripheral edge, said passages each including longitudinally spaced rearward and forward ends, and
• a convex protrusion disposed centrally at a longitudinally rearward end of said central recess and including a convex deflecting surface, said protrusion arranged to contact and fracture the earthen core and deflect the cuttings to said lateral discharge passages, said deflecting surface being disposed closer to said rearward ends of said passages than to said forward ends thereof.

A rotary dill bit for cutting in earth formations, comprising:

• a bit body including a cutting face having a peripheral edge and a central recess extending longitudinally inwardley from said peripheral edge,
• a plurality of fluid discharge nozzles mounted in said cutting face for emitting drilling fluid under pressure,
• a plurality of cutter elements, some of which being mounted in said peripheral edge, and others of which being mounted in said recess to fracture an earthen core formed as the drill cuts through the formation,
• a plurality of lateral discharge passages formed in said body, said passages extending radially through said body from said recess and extending longitudinally to said peripheral edge to form circumferential interruptions in said peripheral edge,
• a convex protrusion disposed centrally at a longitudinally inner end of said recess and including a convex deflecting surface, said protrusion arranged to contact and fracture the earthen core and deflect the cuttings to said lateral discharge passages, and
• a ridge disposed along a trailing edge of each of said discharge passages, each ridge projecting from said cutting face by a distance less than that of said cutter elements and being arranged to retard the flow of drilling fluid into the associated discharge passage from an adjacent one of said nozzles, whereby such fluid is caused to flow across cutter elements located behind said ridge.