BORING BIT AND METHOD OF MANUFACTURE
A boring bit has a shank, a head and teeth distributed around the head. The teeth have a root embedded within the head's core body, a tip extending out of the head, and a narrowing region between the root and the tip. More than approximately two-thirds of the tooth length is embedded in the core body, including a portion of the narrowing region. Stabilizing rods are welded to the tips of the teeth to form a temporary connection, and the core body is formed from a molten metal poured into a cavity of a cast mold. The rods are inserted into indentations in the cast to hold the teeth in place, and the molten metal heats the teeth and weld to substantially loosen the temporary connection. As the molten metal cools, it solidifies around the teeth and secures the root and narrowing region of the teeth within the core body.
This application claims priority from U.S. Provisional Patent Application No. 61/786,516 filed on Mar. 15, 2013 which is hereby incorporated by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCHNot Applicable.
APPENDIXNot Applicable.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to boring bits for the drilling heads of directional boring machines, and more particularly to the design and method of manufacture of the teeth used in the boring bits.
2. Related Art
Boring bits are used in a number of directional boring machines. Generally, directional boring or horizontal directional drilling (HDD) is a steerable trenchless method of installing pipes, conduits and cables along an underground route that is formed from a drilling rig at one end of the route. There are different types of heads used in the pilot-hole process, and they depend on the geological material.
In most boring operations, drilling fluid is used to cool the boring head and to lubricate and soften the spoils. The fluid is usually pumped and delivered to the end of the boring head by means of some conduit through the drill string, and the fluid exits the boring head through the fluid nozzle. The pumped fluid is ported around the cavity housing the electronic components, thereby cooling it. In most boring head assemblies, the fluid is not typically directed ahead of the boring bit to the front most part of the boring operation. Instead, the fluid may be directed toward the head of the boring bit, but the fluid is actually deposited on the shank of the boring bit, and it is not passed through the head of the boring bit or through the head of any other earth drilling or cutting tool that may be attached to the front of the boring head assembly. In the few boring head assemblies in which the fluid is directed ahead of the boring bit, the fluid is typically channeled into multiple conduits to help with the boring. However, the fluid exits at multiple conduits at different angles which vary from the axis of the drill stem and beacon housing unit so the fluid does not provide any significant assistance in the steering of the head.
In the manufacture of the boring bits, the body of the bit, including the head portion, may be formed from any known casting process. However, the carbide teeth are not typically formed in situ with the body of the bit during the casting process for current boring bits. Instead, the manufacturing processes for current boring bits require one or more post-casting steps to secure the carbide teeth into the body. For example, one post-casting step could be to press punch the teeth into the body of the bit so that there is formed an interference fit between the teeth and the body. Other methods to attach the teeth to the body include brazing the teeth onto the body, screwing or threading the teeth into the body, or spot welding the teeth to the body. For those manufacturing methods which incorporate teeth into the cast while molten metal is poured into the cast's cavities, these methods do not provide a good way to temporarily hold the teeth to indentations in the cast while the molten metal fills around the teeth and loosen the hold on the teeth as the metal solidifies.
SUMMARY OF THE INVENTIONIn one aspect of the invention, a boring bit for a directional drilling machine has a shank, a head and a plurality of teeth distributed around the head. Each of the teeth has a root embedded within the head's core body and a tip extending out of the head away from the head's peripheral surface. The teeth also have a narrowing region between the root and the tip. More than approximately two-thirds of the tooth length is embedded in the core body, including a portion of the narrowing region.
In another aspect of the invention, stabilizing rods are welded to the tips of the teeth to form a temporary connection, and the core body is formed from a molten metal poured into a cavity of a cast mold. The stabilizing rods are inserted into indentations in the cast to hold the teeth in place, and the molten metal heats the teeth and the weld and substantially loosens the temporary connection. As the molten metal cools, it solidifies around the teeth and secures the root and narrowing region of the teeth within the core body.
In yet another aspect of the invention, the peripheral surface of the head has a top surface, a bottom surface, a side surface between said top surface and said bottom surface in which the teeth are embedded, and an angled surface between the shank and the top surface. A single passageway extends through the core body from an entrance in the angled surface to an exit in the bottom surface. The single passageway has a planform centerline aligned with a longitudinal axis of the drill stem.
The present invention will become more fully understood from the detailed description and the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances, various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention; therefore the drawings are not necessarily to scale. In addition, in the embodiments depicted herein, like reference numerals in the various drawings refer to identical or near identical structural elements.
The following description of the inventive boring bit 10 for a horizontal directional drilling machine is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Generally, as shown in
The head 14 also has a passageway 68 that extends through the core body 34 from one location proximate to the shank portion 12 to another location at the periphery of the head 14 distal from the shank portion. The proximate location is on one side of the head and the distal location is on a second side of the head. As particularly shown in
As is also shown in
The fluid that flows through the drill stem can be controlled by the operator and as shown in
As particularly shown in
Several aspects of the teeth 16 are particularly shown in
The manufacturing process to produce the boring bit 10 is described in detail below with reference to
The particular casting process is described with reference to a sand cast 42, but it will be appreciated that other cast molds and casting techniques could also be used to create the boring bit 10 according to the present invention, such as investment casting process (“lost wax” cast mold) and other releasable connections 52 between the teeth and the cast may be possible, such as a heat-resistant epoxy temporarily connecting the cone section of the teeth and the cast. Accordingly, although the preferred embodiment of the invention uses stabilizing rods 40 welded to the teeth to hold the teeth in place in the sand cast 42, other releasable connections between the teeth and cast can be within the scope of the several aspects of the present invention.
A sand cast 42 is preferably formed with a cavity 44 having an inner surface 46 in the shape of the shank 12 and head 14. There are indentations 48 in the inner surface where the tips 20 of the teeth 16 are inserted into and releasably held within the sand cast 42. The teeth are radially distributed around the head in the rows described above, and additional teeth can be embedded in the sides 60b of the shank section. A root of each of the teeth extends outwardly from the sand cast into an interior space of the cavity corresponding with the head of the boring bit with a plurality of interstitial spaces between the teeth at their roots. A molten metal is poured into the shank section and head section of the sand cast and fills the interior space and the interstitial spaces between the teeth.
As explained above, it is also preferable to braze the rods onto the tips of the teeth. The rods are inserted into the sand cast which is then hardened with the teeth and the rods in situ. When the molten metal is poured into the sand cast, it heats the teeth and loosens the brazing between said rods and the teeth. The temporary or otherwise releasable connection 52 is generally shown in
It will also be appreciated that a mold pattern is prepared for the cast. The mold pattern includes recesses that can hold tooth blanks to form the indentations 48 in the inner surface 46 of the cast 42. Molding sand is packed into the mold pattern, and then the mold pattern and the tooth blanks are removed from the packed molding sand. When tooth blanks are used, they are removed from the packed molding sand which leaves a hollow at the periphery of the sand cast. The tips of the teeth are inserted into the hollow as the brazed stabilizing rods are pushed into the packed molding sand. Alternatively, the recesses can hold the carbide teeth with the stabilizing rods already welded to the tips of the teeth so that when the sand is packed into the mold pattern the teeth are already in place.
Accordingly, the present invention generally uses the sand cast mold method of pouring molten steel in to a cavity. The brazed rod is used to suspend the tungsten carbide buttons in a secured position within the sand cast while the molten steel is poured. To braze the rod to the tip of a tooth, the tungsten carbide tooth or button is heated to about 1100 degrees. A threaded carbon steel rod 20 is then brazed onto the end close to center of the tungsten carbide button 16. The rod is preferably long enough, about 12″ or so, to avoid burning the welder. Once the brazing weld is completed, the rod is cut down to about ¾″ long which provides a length that is strong enough to hold in the sand cast mold. Generally, the cut rod's length 56 is longer than the combined length of the root 24a and the narrowing region portion 24b which extends into the cavity 44. The length of the tooth's tip portion 24c that is inserted into the indentation 48 in the cast is less than approximately one third (⅓) the overall tooth length 24.
The sand cast mold can be chemically treated to harden the sand. The sand adheres well to the threaded part of the rod 40 and holds it in place until the molten steel is poured and then solidifies as it cools. As described above, the tungsten carbide teeth have an indent in their roots, preferably more than one indent in each root. The depth of the indent is about 0.005″ and the length is about ¼″ which allows the molten steel to fill in the notch and permanently prevent the teeth from coming loose from the boring bit. Accordingly, the notch provides a positive lock to hold the tungsten carbide teeth in place within the molten metal that solidifies around the teeth.
There are several techniques used for manufacturing the notches in the teeth. The notches can be formed by grinding the tungsten carbide teeth, such as with a green carbide grinding wheel. A carbide grade wheel is used to cut or grind away material (carbide) normally used to sharpen carbide cutters used in cutting steel. Alternatively, the notch or other indention can be cast or otherwise formed or machined in the tooth.
The melting point of the tungsten carbide is over 5,000° F. (approximately 5,200° F.) whereas the melting point of the steel is under 3,000° F. (approximately 2,500° F.-2,800° F.). Accordingly, the tungsten carbide teeth remain solid as the molten steel is poured into the cast. The tungsten carbide teeth conduct the heat to the welded brazing material at the tip of the teeth, the brass heats up and the weld is loosened, releasing the tungsten carbide teeth to the steel as it solidifies around the roots and allowing the rods to remain in the cast where they are embedded. Similarly, heat may reduce the strength of an epoxy temporarily fixing teeth in the indentations.
As shown in
The embodiments were chosen and described to explain the principles of the invention and its practical application to persons who are skilled in the art. Modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention. All matter contained in the foregoing description and shown in the accompanying drawings is illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
Claims
1. A boring bit, comprising:
- a shank portion;
- a head portion connected to said shank portion, said head portion having a core body and a peripheral surface; and
- a plurality of teeth distributed around said head portion, wherein each of said teeth has a root embedded within said core body, a tip extending out of said head portion away from said peripheral surface, a narrowing region between said root and said tip and a tooth length from a bottom of said root to a top of said tip, wherein said narrowing region has a decreasing width from a root width to said tip, wherein more than approximately two-thirds of said tooth length is embedded in said core body of said head portion, wherein said core body of said head portion covers a portion of said narrowing region.
2. The boring bit of claim 1, further comprising a plurality of stabilizing rods, wherein each of said teeth has one of said stabilizing rods releasably connected to said tip.
3. The boring bit of claim 2, further comprising a cast mold, wherein said cast mold forms a cavity and comprises an inner surface in contact with said peripheral surface and further comprises a plurality of indentations in which each tip of said teeth are embedded, wherein said stabilizing rods are encapsulated in said cast mold at said indentations and wherein said root and a portion of said narrowing region of said teeth extend into said cavity more than approximately two-thirds of said tooth length.
4. The boring bit of claim 3, further comprising a weld forming a temporary connection between each one of said stabilizing rods and said tip of said teeth, wherein said core body is formed from a molten metal poured into said cavity, wherein said molten metal heats said teeth and said weld and substantially loosens said temporary connection while said molten metal cools and secures said root and said narrowing region of said teeth within said core body as said molten metal solidifies around said teeth.
5. The boring bit of claim 4, wherein said teeth are formed from a carbide material having a first melting point at least 1,000° F. greater than said molten metal and wherein said weld is formed from a brazing material having a second melting point less than said first melting point by more than 1,000° F.
6. The boring bit of claim 3, wherein said stabilizing rods have a rod length and wherein said rod length is greater than a length of said root and said portion of said narrowing region extending into said cavity.
7. The boring bit of claim 1, further comprising a cast mold, wherein said cast mold forms a cavity and comprises an inner surface in contact with said peripheral surface and further comprises a plurality of indentations, wherein each of said indentations is comprised of a releasable connection with a corresponding one of said tip of said teeth.
8. The boring bit of claim 7, wherein said core body is formed from a molten metal poured into said cavity, wherein said molten metal substantially frees said releasable connection between each one of said indentations and said tip of said teeth.
9. The boring bit of claim 8, wherein said releasable connection is comprised of a stabilizing rod welded to said tip.
10. The boring bit of claim 1, wherein said shank further comprises a mounting face, a pair of sides and a set of teeth embedded into said sides, wherein said root is comprised of a substantially cylindrical surface and a notch in said cylindrical surface, wherein said core body of said head portion is in fixed contact with said cylindrical surface and with said notch.
11. The boring bit of claim 1, wherein said head portion further comprises an upper row of teeth, a lower row of teeth and a middle row of teeth, a top surface proximate to said upper row of teeth and a bottom surface proximate to said lower row of teeth, an angled surface between said shank and said top surface, a single passageway extending through said core body from an entrance in said angled surface to an exit in said bottom surface.
12. The boring bit of claim 11, wherein said single passageway at said entrance is further comprised of a countersunk hole having an outer diameter approximately twice an inner diameter of said passageway, wherein said exit in said bottom surface is located at a substantially planar surface and is not located between a pair of said teeth in said head.
13. The boring bit of claim 12, further comprising a drill stem with a nozzle extending to said passageway, wherein said drill stem has a longitudinal axis, and wherein said single passageway has a planform centerline aligned with said longitudinal axis.
14. A boring bit for a horizontal directional drilling machine having a drill stem with a longitudinal axis and a nozzle, comprising:
- a shank portion comprising a mounting face, a back face, a pair of sides between said mounting face and said back face, and a plurality of mounting holes;
- a head portion connected to said shank portion, said head portion having a core body and a peripheral surface, wherein said peripheral surface has a top surface, a bottom surface, at least one side surface between said top surface and said bottom surface, and an angled surface between said shank and said top surface, a single passageway extending through said core body from an entrance in said angled surface to an exit in said bottom surface, wherein said single passageway has a planform centerline aligned with the longitudinal axis; and
- a plurality of teeth distributed around said head portion, wherein each of said teeth has a root embedded within said core body, a tip extending out of said head portion away from said peripheral surface, a narrowing region between said root and said tip and a tooth length from a bottom of said root to a top of said tip, wherein said narrowing region has a decreasing width from a root width to said tip, wherein more than approximately two-thirds of said tooth length is embedded in said core body of said head portion, wherein said core body of said head portion covers a portion of said narrowing region.
15. The boring bit of claim 14, wherein said wherein said root is comprised of a substantially cylindrical surface and a notch in said cylindrical surface, wherein said core body of said head portion is in fixed contact with said cylindrical surface and with said notch and provides a positive lock between each one of said teeth and said head portion with said core body projecting from said cylindrical surface into said indentation.
16. The boring bit of claim 14, further comprising a plurality of stabilizing rods, a cast mold and a weld forming a temporary connection between each one of said stabilizing rods and said tip of said teeth, wherein each of said teeth has one of said stabilizing rods releasably connected to said tip, wherein said cast mold forms a cavity and comprises an inner surface in contact with said peripheral surface and further comprises a plurality of indentations in which each tip of said teeth are embedded, wherein said stabilizing rods are encapsulated in said cast mold at said indentations, wherein said root and a portion of said narrowing region of said teeth extend into said cavity more than approximately two-thirds of said tooth length, wherein said core body is formed from a molten metal poured into said cavity, wherein said molten metal heats said teeth and said weld and substantially loosens said temporary connection while said molten metal cools and secures said root and said narrowing region of said teeth within said core body as said molten metal solidifies around said teeth.
17. A method for manufacturing a boring bit, comprising the steps of:
- forming a cast having a cavity for a head portion with an inner surface and a plurality of indentations in said inner surface;
- embedding a plurality of teeth in said indentations of said cast, wherein a tip of each of said teeth contacts said indentations and wherein a root of each of said teeth extends outwardly from said cast into said cavity of said head portion, said tip being less than one half of a tooth length and said root extending more than one half of said tooth length into said cavity;
- creating a temporary connection between said tip of each of said teeth and said cast at said indentations;
- pouring a molten metal into said cavity of said cast, said molten metal surrounding said root of each of said teeth and filling said cavity to said inner surface, wherein said molten metal heats said teeth and loosens said temporary connection between said tip and said cast.
18. The method of claim 17, wherein said step of creating said temporary connection is further comprised of the steps of welding a plurality of stabilizing rods onto said teeth at said tip, inserting said stabilizing rods into said cast at said indentations and hardening said cast with said teeth and said rods in situ.
19. The method of claim 18, further comprising the step of cooling said molten metal to solidify into a core body supporting each of said teeth at said root as said temporary connection between said tip of said teeth and said cast is loosened, breaking off said cast from a solidified core body with said stabilizing rods remaining in said cast, and drilling a passageway in said head portion through said solidified core body.
20. The method of claim 19, further comprising the step of preparing a mold pattern for said cast, wherein said mold pattern includes a plurality of recesses for at least one of said teeth and a plurality of tooth blanks.
Type: Application
Filed: Mar 16, 2014
Publication Date: Sep 18, 2014
Applicant: Rockhound Boring Products, LLC (St. Louis, MO)
Inventor: Douglas R. Ford (Cedar Hill, MO)
Application Number: 14/214,976
International Classification: E21B 10/62 (20060101); B24D 18/00 (20060101);