Breakable washer earth boring bit

[0001] This application claims the benefit of U.S. provisional application Ser. No. 60/346,227, filed Nov. 16, 2001, entitled Breakable Washer Earth Boring Bit.

[0002] This invention relates to earth boring bits and more particularly, to earth boring bits and a breakable washer for facilitating removal of the earth boring bit from a drill string.

[0003] Conventional earth boring bits have an integral threaded pin for attachment of the bit to a drill string. The screw threads of the threaded pin and of the drill string have an orientation such that the various connections all tend to be tightened by the rotary motion of the bit during drilling operation. If the bit was not properly tightened at installation, this tends to result in over tightening of the drill bit to the drill string. When the over-tightened bit is expended there may be significant difficulty in removing the bit from the drill string. Various techniques have been used to remove an over-tightened bit including use of an oxygen/acetylene torch to heat the threaded connection in an attempt to release the over-tightened bit from the drill string. This is a time consuming operation and many times results in significant down time for a rig. Another often used technique is to use a sledge hammer in an attempt to loosen the drill bit from the over-tightened condition. This bit removal problem has always been a serious one and very little effort has been directed to finding an acceptable solution.

[0004] U.S. Pat. No. 5,234,063 describes a break-out ring for mounting on a circular surface of a drill bit at the connecting pin to facilitate removal of the over-tightened bit from the drill string. However, the break-out ring described in this United States patent has parallel surfaces and when assembled between a shoulder of the drill bit and a special bit sub required for installation of the drill bit there is little improvement for removal of the bit. The break-out ring of this patent is described as having weakened portions to facilitate removal of the ring thereby releasing the over-tightened drill bit from the drill string. Because of the parallel surfaces of the break-out ring there is considerable difficulty in removing the ring to release the over-tightened drill bit. The parallel surfaces of the break-out ring becomes a part of the over-tightened connection and requires considerable force for removal from between the drill bit and the drill string.

[0005] Thus there is a need for a breakable washer for assembly between a drill bit and the standard connection of a drill string that enables removal of a drill bit in an over-tightened condition without destruction of the drill bit, and with relative ease.

[0006] In accordance with the present invention, there is provided a breakable washer to facilitate removal of an earth boring bit or other tool when the connection with a drill string has been over-tightened or when there is not means available to loosen the bit. The breakable washer of the present invention provides for removal of a drill bit when equipment is not available to apply sufficient break-out torque. When assembled, the surfaces of the breakable washer are positioned between the mating surfaces of the threaded connection between the earth boring bit, or other tool, and the standard receiver of a drill string.

[0007] To accommodate the breakable washer of the present invention the conventional shoulder of the threaded pin of a drill bit is modified to receive the washer. The combination of the modified threaded pin and the washer comprise the standard geometry to mate with a standard receiving connection of a drill string in accordance with API specifications. The modified earth boring bit and the breakable washer of the present invention make up to a drill string in a conventional manner, with the washer between mating shoulders of the bit and the drill string. The breakable washer has a planar face perpendicular to the axis of the threaded pin and this planar face mates with the planar face of a conventional receiver of a drill string or bit sub. The surface of the breakable washer opposite from the planar face has a conical face. This conical face mates with a matching conical face of the drill bit at the threaded pin. The planar face of the washer combined with the conical face results in a radially diverging cross section for the washer, thinner at the inside diameter and thicker at the outside diameter.

[0008] To remove an over-tightened drill bit or other tool the breakable washer of the present invention is broken and driven from between the connecting parts by suitable means such as a hammer and chisel or other tool designed for the purpose. As a result of the conical face only a small movement of the broken washer is required to release the washer from between the mating connecting surfaces.

[0009] In accordance with the present invention there is provided apparatus for earth boring comprising a tool for attachment to the conventional makeup end of a drill string wherein the apparatus comprises a tool body having a longitudinal axis and including a makeup end. A tool joint pin extends from and is integral with the makeup end of the tool body and includes a radially extending circumferential surface. The circumferential surface is part of the makeup end of the tool body. The radially circumferential surface extends outward from the tool joint pin to the outer surface of the tool body. The radially-extending surface comprises a conical face at an angle of up to 15 degrees with reference to a surface perpendicular to the longitudinal axis of the tool body. A breakable washer is assembled between the radially extending surface of the tool body and a makeup end of the drill string. The breakable washer has a first surface normal to the longitudinal axis to the tool body and a conical-shaped second surface at an angle of up to 15 degrees with reference to the first surface.

[0010] Further in accordance with the present invention there is provided a breakable washer for assembly between a tool and the conventional end of the makeup end of a drill string, wherein the breakable washer comprises a ring shaped body having a first planar surface and a second conical surface such that the breakable washer comprises a radially diverging cross section. Two or more breakout recesses are included in the outer surface of the ring shaped body to facilitate fracturing and removing the washer.

[0011] A technical advantage of the present invention is to facilitate removal of a drill bit or other tool from a drill string without the use of heat or excessive forces. This technical feature is achieved by a breakable washer having a radially diverging cross section with one surface planar and a second surface having a conical configuration.

[0018] Reference is now made to the drawings wherein like reference characters denote like or similar parts throughout the various figures. Although the invention is described with reference to a drill bit as the preferred embodiment, it has utility for use with other tools used for earth boring.

[0019] Referring to FIGS. 1 and 2, there is shown a drill stem assembly including a conventional roller cone earth boring bit 10 comprising a body 12 having a longitudinal axis 14. A plurality of journal pins (not shown) extend from the sections 16 of the body 12 for supporting roller cones 18 having conventional inserts arranged in accordance with recognized patterns. Although FIGS. 1 and 2 illustrate a three cone bit it should be understood that the present invention of a breakable washer is not limited to use with such bits but also find utility with drag bits, diamond bits, and other earth boring tools.

[0020] The drill bit 10 is threadedly coupled to a conventional makeup end receiver of a drill string 20 illustrated as having a fluid passage 22. Assembled between the drill bit 10 and the makeup end of the drill string 20 is a breakable washer 24 for facilitating removal of the drill bit from the drill string. Again, it should be mentioned that the drill bit 10 may not directly couple to the drill string 20 but may be coupled to a drill bit sub (not shown).

[0021] Referring to FIG. 3, there is shown a plan view of the breakable washer 24. As illustrated, the breakable washer 24 has a ring-shaped configuration with an inner diameter slightly larger than the outer diameter of the threaded pin 26 of the drill bit 10. The breakable washer 24 has an outer diameter approximately equal to the diameter of the bit body 12. The outer surface of the breakable washer 24 includes two diametrically opposed semi-circular breakpoint recesses 28 and 30. Similarly, the inner surface of the breakable washer 24 includes two semi-circular diametrically opposed breakpoint recesses 32 and 34. Between the recesses 28 and 32 is a fracture link 31 and between the recesses 30 and 34 there is a fracture link 33. It should be understood that more than two breakpoint recesses may be included in the inner or outer surfaces of the breakable washer 24 and the semi-circular configuration shown in FIG. 3 is exemplary only.

[0022] Referring to FIG. 4, there is shown an alternate embodiment of the breakable washer 24. As illustrated in FIG. 4, the breakable washer 24 has a ring-shaped configuration with an inner diameter slightly larger than the outer diameter of the threaded pin 26 of the drill bit 10. The breakable washer 24 has an outer diameter approximately equal to the diameter of the bit body 12. The outer surface of the breakable washer 24 includes three break point recesses 44, 46 and 48 spaced approximately 120 degrees apart. Similarly, the inner surface of the breakable washer 24 includes three break point recesses 50, 52 and 54. The recesses of the breakable washer 24 of FIG. 4 have a configuration of a truncated triangle. Between the recesses 44 and 50 and between the recesses 46 and 52 and similarly between the recesses 48 and 54, there is a fracture link 56. The cross-section configuration of the breakable washer of FIG. 3 and the breakable washer of FIG. 4 is similar.

[0023] Referring to FIG. 5, there is shown a cross section of the washer 24 assembled between the conventional makeup end 36 of the drill string 20 and the shoulder 38 of the drill bit 10. The surface of the makeup end 36 is normal to the longitudinal axis 14 and has a substantially ring-shaped configuration similar to the ring-shaped configuration of the breakable washer 24. The shoulder 38 has a conical shape (not necessarily planar) at an angle with reference to the longitudinal axis 14 to mate with a conical-shaped surface of the breakable washer 24.

[0024] With reference to the breakable washer 24 as illustrated in FIG. 5, the washer includes a first surface 40 having a planar configuration and normal to the longitudinal axis 14 (centerline axis 35) when installed between the drill bit 10 and the drill string 20. In addition, the breakable washer 24 has a second surface 42 having a conical shape (not necessarily planar) at an angle with reference to the first surface 40. In cross section, the breakable washer has a radially diverging configuration. The angle between the surface 40 and the surface 42 must be shallow enough to hold the washer 24 in position between the makeup end 36 and the shoulder 38, typically 15 degrees or less. The preferred angle between the surface 40 and the surface 42 is 5 degrees. If the angle between the two surfaces is too large then the washer 24 will be subject to breakage and will be forced out from between the makeup end 36 and shoulder 38 when the drill bit 10 is made up to the drill string 20.

[0025] The technical advantage of the conical shape of the second surface 42 is facilitating the removal of the washer from between the drill bit 10 and the drill string 20. To remove the breakable washer 24 from between the drill bit 10 and the drill string 20, the fracture links 31 and 33 are broken thereby fracturing the washer into pieces. After the washer 24 has been fractured a small movement of the pieces of the washer from between the drill bit 10 and the drill string 20 results in a separation between the surfaces 36 and 40 and the surfaces 38 and 42 thereby enabling easy removal of the washer 24.

[0026] Although the invention has been described in detail, it is to be understood that the explanation is by way of illustration an example only and is not to be taken by way of limitation, the spirit and scope of the invention being limited only to the terms of the claims.