Shirttails for reducing damaging effects of cuttings
View Patent ↗An earth-boring bit has a bit body that includes head sections, each having depending bit legs with a circumferentially extending outer surface, a leading side, and a trailing side. A bearing shaft depends inwardly from each of the bit legs for mounting a cutter. The bit includes a beveled surface formed at a junction of the leading side and the outer surface of each bit leg. The beveled surface is angled relative to a radial plane emenating from the axis of the bit. The angle of the beveled surface is at least 20 degrees, and extends to an inner surface of the bit leg. The bit can also have a layer of hardfacing on the leading, trailing and shirttail surfaces of the bit leg. A diversion finger of hardfacing extends circumferentially to direct cuttings.
1. An earth-boring bit comprising:
a bit body comprising a plurality of head sections, each of the head sections having a curved lower end defining a shirttail and an outer surface, the outer surface having a ball plug spaced above the shirttail;
a cutter rotatably mounted to a cantilevered bearing shaft depending inwardly from each of the head sections;
a layer of hardfacing on each of the head sections, the layer of hardfacing including a leading edge portion formed on a leading side of each of the head sections and a shirttail portion formed on the shirttail of each of the head sections below the ball plug; and
the layer of hardfacing including an outer surface portion of hardfacing joining the leading edge and the shirttail portions of hardfacing and formed on the outer surface of each head section above the ball plug, the outer surface portion of hardfacing having an upper edge and a lower edge below the upper edge, defining between the edges a gap wherein the outer surface of each head section is free of hardfacing.
2. The bit of claim 1 , wherein the gap extends toward a trailing side of each of the head sections.
3. The bit of claim 1 , wherein:
the gap extends upwardly and toward a trailing side of each of the head sections.
4. The bit of claim 1 , further comprising:
an inner layer of hardfacing extending along a portion of an inner surface of each head section.
5. The bit of claim 1 , wherein:
the gap has at least one edge that is straight.
6. The earth-boring bit of claim 1 , wherein:
the gap is defined by two straight parallel edges of the outer surface portion of the layer of hardfacing.
7. An earth-boring bit comprising:
a bit body comprising a plurality of head sections, each head section having a ball plug;
a cutter rotatably mounted to cantilevered bearing shaft depending inwardly from each of the head sections for mounting a cutter;
a layer of hardfacing formed on a leading side and on an outer surface of each of the head sections, the layer of hardfacing extending from the leading side to the outer surface of the head section above the ball plug and below the ball plug; and
wherein the ball plug is free of any hardfacing.
8. The earth-boring bit of claim 7 , wherein the layer of hardfacing extends toward a trailing side of each head section.
9. The earth-boring bit of claim 7 , wherein a portion of the outer surface of each head section above and below the ball plug is free of any hardfacing.
10. The earth-boring bit of claim 7 , wherein the layer of hardfacing of each head section has at least one gap therein above the ball plug where the outer surface of the head section is free of any hardfacing.
11. The earth-boring bit of claim 10 , wherein the gap extends toward a trailing side of each head section.
12. The earth-boring bit of claim 10 , wherein the gap is elongated, having a length greater than a width.
13. The earth-boring bit of claim 7 , wherein:
each head section has an inner surface; and
further comprising an inner layer of hardfacing extending along a portion of the inner surface of each head section.
14. An earth-boring bit comprising:
a bit body comprising a plurality of head sections, each head section having a shirttail at a lower end portion of each head section and a ball plug spaced above the shirttail;
a cutter rotatably mounted to a cantilevered bearing shaft depending inwardly from each of the head sections; and
a layer of hardfacing formed on each of the head sections, the layer of hardfacing having a leading edge portion extending along a leading side of each of the head sections, a shirttail portion joining the leading edge portion and extending along the shirttail below the ball plug, and an outer surface portion joining the leading edge portion and the shirttail portion and extending above the ball plug.
15. The earth-boring bit of claim 14 , wherein the outer surface portion of the layer of hardfacing on each of the head sections has at least one gap therein above the ball plug.
16. The earth-boring bit of claim 14 , wherein the gap is elongated and extends toward a trailing side of each of the head sections.
17. The earth-boring bit of claim 14 , wherein:
the gap is defined by two straight parallel edges of the outer surface portion of the layer of hardfacing.