Tricone Bit Construction

Abstract

A roller cone drill bit having detachable rotatable arms. The arms are connected at a mounting pad to the bit body. Each arm has its own grease delivery system to provide lubrication to the interface between the arms and rolling elements at an end of each arm. The forward-facing contact surface between the bit body and the arms is at an angle, relative to the central axis of the bit, that is ninety degrees or more.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of provisional patent application Ser. No. 61/845,621 filed on Jul. 12, 2013, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates generally to roller cone drill bits.

SUMMARY

The present invention is directed to a bit. The bit comprises a body, a plurality of bit arms, a cone and a pin. The body comprises a center axis and a mounting pad and is connectible to a drill string. The bit arms are mounted on the body at the mounting pad. The cone is rotatable attached to each bit arm and comprises a plurality of teeth. The pin is located within each bit arm and the body through the mounting pad.

In another embodiment the invention is directed to a method for lubricating internal components of a bit having a bit body, a plurality of removable arms attached to the bit body, rolling elements attached to each of the removable arms, and at least one ball bearing located between the rolling elements and each of the removable arms. The method comprises connecting a removable arm with the bit body using a pin comprising a hollow passage, providing grease to a pressurized reservoir in the bit body, conveying grease into the removable arm through the hollow passage of the pin, providing a continuous passage through the removable arm proximate the ball bearings, and rotating the rolling elements to distribute grease from the continuous passage to the ball bearings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a tricone rolling element bit.

FIG. 2 is a side perspective view of a ⅓rd segment of a tricone bit.

FIG. 3 is a perspective view showing three preassembled segments of a tricone bit.

FIG. 4 is a perspective view of an alternative tricone bit.

FIG. 5 is a sectional side view of the tricone bit of FIG. 4.

FIG. 6 is another sectional side view of the tricone bit of FIG. 4.

FIG. 7 is a detail view of the joint shown in FIG. 6 labeled “A”.

FIG. 8 is a side view of a horizontal directional drilling apparatus.

DESCRIPTION

With reference to FIG. 1, shown there in is a tricone drill bit 10. A tricone hit 10 is characterized by three rolling cone cutting elements 24. A tricone bit, used in the oilfield, may have a useful life of a single bore. Tricone bits are also used in installation of buried utilities. This application, known as Horizontal Directional Drilling or “HDD”, typically has shorter length runs and less economic consequence in the case of bit failure. HDD typically involves bores between 300 and 1,200 feet, allowing for inspection, evaluation and service of the bit between bores. To improve the per-foot cost of operation of tooling, parts are typically rebuilt and reused to the limit of endurance and wear. A brief discussion of HDD is given with reference to FIG. 8.

With reference to the figures in general and FIG. 1 specifically, a tricone bit 10 is shown therein. The bit 10 comprises a body 12 and a plurality of arms 14. The body 12 comprises a base 16 and a mounting pin 18. The mounting pin 18 is threaded as shown herein for connection to a drill string (FIG. 8). Alternatively, the mounting pin 18 may be splined or geometrically aligned for connection to a drill string. The base 16 supports a fluid delivery system 20 and the plurality of arms 14. As shown, the fluid delivery system 20 comprises a plurality of nozzles 22. The plurality of nozzles 22 supply a fluid, such as drilling mud, for lubrication of the bit 10. As shown, each of the plurality of nozzles 22 is directed to a corresponding one of the plurality of arms 14.

Each of the plurality of arms 14 comprises a rolling element 24 comprising carbide teeth 26, a ball port 28, and a grease port 30. The carbide teeth 26 engage material to be moved by the tricone bit 10. The teeth 26 may be equalized and dispersed about the rolling elements 24. The precise pattern of the teeth 26 may vary by size of the bit 10 and material being removed. The teeth 26 may take on various profiles as a function of the insert orientation. For some bits 10, this may result in three different unique rolling elements 24a, 24b, 24c making up bit assembly 10.

Bearing balls (FIG. 5) may be used to reduce friction and facilitation rotation of rolling elements 24. These may be assembled through the ball port 28. Preferably, the ball port 28 is closed with a plug (FIG. 5) after assembly. Drilling mud is used by the fluid delivery system 20 to facilitate removal of the cuttings and clean the rolling elements 24a, 24b, 24c. Drilling mud is discharged through the nozzles 22, which are supplied with mud through the drill pipe bolted to mounting pin 18. Grease port 30 allows access to an internal reservoir for lubrication. Grease may be added through grease port 30, and the reservoir is pressure balanced to maintain lubricant pressure similar to that of the bore hole. Bore hole pressure is accessed through a pressure port 32.

In operation, the bit 10 of FIG. 1 bores through a subsurface by rotation of the rolling elements 24 and grinding of the subsurface by the carbide teeth 26. Drilling fluid provided by the nozzles 22 softens the area being drilled and prolongs the life of the carbide teeth. As material is removed from the subsurface, forming a borepath, the bit 10 is advanced along the bore path by sections of drill string (not shown).

With reference now to FIG. 2, shown therein is one third of the tricone bit 10 of FIG. 1. This section is referred to as a “shirttail sub-assembly” 40. The shirttail sub-assembly 40 comprises one third of the cylindrical bit body 12 with one arm 14 and one nozzle 22. Each shirttail sub-assembly 40 is joined into the tricone bit 10 (FIG. 1) via welding along split plane 42. After welding, the mounting pin 18 may be threaded or geometrically formed. Alternatively, the threads or geometric characteristics of the mounting pin 18 may exist on the shirttail subassembly 40 prior to welding. Three shirttail sub-assemblies 40 are formed into the tricone bit 10 of FIG. 1 through welding at the split plane 42, as shown in FIG. 3. With reference now to FIG. 4, an alternative tricone bit 10a comprising a mounting pad 50 is shown. The mounting pad 50 is generally the interface between the arms 14 and bit body 12. The arms 14 are attached to the bit body 12 at the mounting pad 50 by bolts 54. As shown, there are three bolts 54 in each arm 14. The arms 14 are disposed about a center axis 58. The grease port 30 provides access to internal lubrication systems (FIG. 5) from the outside of the bit body 12. The ball port 28 provides access to internal ball bearings (FIG. 5) located proximate each rolling element 24.

With reference to FIG. 5, the tricone bit 10a comprises a fluid delivery system 60 in each of the arms 14 and the bit body 12. The fluid delivery system 60 comprises a pressurized pocket 62, a spring 64, a lubrication piston 66, a shear pin 68 comprising a hollow central passage 69, a middle grease passage 70, an upper grease passage 72, and a bushing 74. The lubrication piston 66 produces grease pressure within the fluid delivery system 60 by the applied load of the spring 64. As shown, the piston 66 and spring 64 are at the full range of travel within the pressurized pocket 62. Thus, grease pressure may only be increased further by addition of additional grease pressure through grease port 30.

Grease flows through the central passage 69 of shear pin 68. This cylindrical pin 68 is a close fit seal through mounting pad 50, a shear pin to resist shear forces due to bit torque and as a conveyance tube. Grease from pocket 62 is able to flow to the bushing 74 through middle grease passage 70 and upper grease passage 72. A plug 76 is shown within ball port 28. Preferably, the plug 76 has a reduced diameter proximate the central passage 70 and upper grease passage 72 to enable flow of grease through the fluid delivery system 60. Fluid for lubrication reaches the bushing 74 and greases ball bearings 80 to allow free rotation of the rolling elements 24 relative to the bit arms 14. In this way, fluid for lubrication, or grease, travels through a continuous passage from the shear pin 68 to the bushing 74.

The bit arms 14 further comprise a cone seal 82. The cone seal 82 seals the bushing 74 and limits lubricant leakage as the rolling element 24 rotates in operation. Preferably, the grease port 30 is formed inside a pocket 84 formed in the bit body 12 to protect the grease port from damage when bit 10a rotates in use.

The bit 10a defines a central fluid cavity 90 and nozzle feed passages 92. Drilling fluid enters the central fluid cavity 90 from the drill string (not shown), is discharged into the nozzle feed passages 92, and exit the bit 10a through nozzles 22. As shown in the figures, three independent nozzles 22 exist, one feeding each bit arm 14 and rolling element 24. Alternative designs are contemplated, including the use of a greater number of nozzles 22 to direct drilling fluid at the rolling elements 24.

With reference now to FIG. 6, the bit 10a is shown in cross-section. The bit arms 14 comprise a counterbore 100. Connectors, such as bolts 54 are shown within the counterbores 100. The counterbore 100 protects the bolt 54 from wear as the bit 10a operates. The bolt 54 extends through bit arm 14 through the mounting pad 50 into the bit body 12. The bit body 12 comprises a threaded hole 102 corresponding to the counterbore 100 of each bit arm 14. Insertion of the bolt 54 into the threaded hole produces a clamping load between the arm 14 and bit body 12, engaging the features of the mounting pad 50.

The mounting pad 50 comprises lands 110 located on each bit arm 14 and grooves 112 located on the bit body 12. The lands 110 and grooves 112 correspond and may be straight, circular, curved, geometrically shaped, or any other corresponding configuration. With reference now to FIG. 7, detail section “A” of the mounting pad 50 is shown in greater detail. The lands 110 of arm 14 engages groove 112 of bit body 12 upon tightening of bolt 54. The grooves 112 comprise a front-facing wall of the bit body 12 for engagement of the lands 110 at a corresponding surface. Note that a reference line 114, parallel to a center axis 58 (FIG. 4) of the bit body 12, creates an angle 116 with a line 118 collinear to one of the grooves 112. The angle 116 as shown is 105 degrees. Preferably, this angle is not less than 90 degrees. With an angle 116 greater than 90 degrees, thrust loads applied primarily to the front of the bit 10a and generally directed along its central axis encounter greater stability.

With reference now to FIG. 8, a horizontal directional drilling system 200 for use with the bit 10 disclosed herein is shown. The system comprises a drilling machine 202, a drill string 204, and the bit 10. The bit 10 is advanced through a subsurface 205 by thrust and rotation of the drill string 204 provided at the drilling machine 202. As a result of this operation, a borehole 206 is created in the subsurface 205. The bit 10 exits the borehole 206 at an exit side 208. A utility line (not shown) may be pulled in behind the drill string 204, or alternatively, a separate backreaming assembly (not shown) is attached at the exit side 208 and pulled back through the borehole 206 to the drilling machine 202.

Various modifications can be made in the design and operation of the present invention without departing from its spirit. Thus, while the principal preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, it should be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Claims

1. A bit comprising:

a body comprising a plurality of grooves, the body connectible to a drill string;

a plurality of bit arms each comprising a plurality of lands corresponding to the plurality of grooves, each of the plurality of bit arms affixed to the body;

a cone rotatably attached to each bit arm, each cone comprising a plurality of teeth;

a fluid delivery system comprising: a fluid reservoir disposed within the body; a fluid passage formed within the bit arm; and a ball bearing in communication with the fluid passage, the ball bearing located between the cone and the bit arm; and

a connector to connect the plurality of grooves of the body to the plurality of lands of one of the plurality of arms.

2. The bit of claim 1 further comprising:

a drilling fluid passage located within the body portion; and

a nozzle for conveying drilling fluid to an exterior of the plurality of bit arms.

3. The bit of claim 2 wherein the nozzle is directed at the cone of each of the plurality of bit arms.

4. The bit of claim 3 comprising three bit arms and three nozzles.

5. The bit of claim 1 wherein the fluid delivery system further comprises a pin comprising a central passage located within each bit arm and the body.

6. The bit of claim 1 comprising three bit arms.

7. The bit of claim 1 wherein the connector comprises a bolt.

8. The bit of claim 1 wherein the internal fluid reservoir comprises a spring and a piston to provide fluid pressure to the fluid delivery system.

9. The bit of claim 1 wherein the plurality of grooves are straight, curved, or circular.

10. The bit of claim 1 further comprising:

a bore located within each of the bit arms for receiving the connector; and

a plurality of threaded holes corresponding to each of the bores in the bit arms for receiving the connector.

11. The bit of claim 1 wherein the plurality of grooves comprise a front-facing sidewall, wherein an angle between the front-facing wall and a center axis of the body portion is at least 90 degrees.

12. The bit of claim 11 wherein the angle is 105 degrees.

13. The bit of claim 11 further comprising:

a drilling fluid passage located within the body portion; and

a plurality of nozzles for conveying drilling fluid to the cone section of an exterior of the plurality of bit arms.

14. The bit of claim 13 comprising three bit arms and three nozzles.

15. The bit of claim 1 wherein the fluid reservoir comprises a spring and a piston to provide fluid pressure to the fluid delivery system.

16. A bit comprising:

a body comprising a center axis and a mounting pad connectible to a drill string, the mounting pad comprising a plurality of grooves;

a plurality of bit arms comprising a plurality of lands, each of the plurality of bit arms mounted on the body at the mounting pad;

a cone rotatably attached to each bit arm, each cone comprising a plurality of teeth; and

a connector located within each bit arm and the body through the mounting pad.

17. The bit of claim 16 wherein the plurality of grooves of the mounting pad comprises a front-facing wall at which one of the plurality of lands of the plurality of bit anus contacts the mounting pad.

18. The bit of claim 17 wherein the angle between the center axis and the front-facing wall is 90 degrees or greater.

19. The bit of claim 16 further comprising a fluid delivery system, the fluid delivery system comprising:

a fluid reservoir disposed within the body;

a fluid passage formed within the bit arm;

a pin within the bit arm and the body and placed through the mounting pad, wherein a hollow passage of the pin is in communication with the fluid reservoir and the fluid passage; and

a ball bearing in communication with the fluid passage, the ball bearing located between the cone and the bit arm.

20. The bit of claim 16 further a drilling fluid passage located within the body portion and a nozzle for conveying drilling fluid to an exterior of the plurality of bit arms.

21. A method for attaching a plurality of removable but arms to a bit body, the bit body comprising a mounting pad comprising grooves, the plurality of bit arms each comprising lands and a rolling element, the method comprising:

placing the lands of one of the plurality of bit arms on the mounting pad of the bit body such that the lands and grooves correspond;

placing a connector through the one of the plurality of bit aims and the bit body at the mounting pad;

conveying grease into the removable arm through bit body;

providing a continuous passage through the removable arm proximate ball bearings; and

rotating the rolling elements about the ball bearings to distribute grease from the continuous passage to the ball bearings.

22. The method of claim 21 wherein the grease is conveyed to the removable arm from the bit body through a hollow pin.

23. The method of claim 21 wherein an angle between a center axis of the bit body and a front-facing wall of the grooves is ninety degrees or more.