Patent Grant
8210287
1. Field of Invention
The present application relates to diamond cutting tools. More particularly, the present application concerns new and improved diamond mining core drill bits or hole saws for cutting rock and earth, and to methods of manufacturing diamond mining core drill bits.
2. Description of Related Art
Diamond core drilling equipment is used extensively to drill circular or annular holes in a variety of materials. Annular holes are formed in rock, earth, concrete, asphalt, and related materials for a variety of reasons. For example, holes are drilled in rock during mining or during exploration for purposes of determining soil compaction, determining soil percolation or to perform other geological research. Further, for example, holes are also commonly drilled in concrete and similar materials for the purpose of correcting the settlement of pavement or to provide openings to utility conduit cells located beneath the surface of cast concrete floors of office and factory buildings. Further, for example, holes are also commonly drilled in concrete or masonry to facilitate the mounting of objects such as posts or pipes.
Examples of prior art diamond core drill bits or hole saws of a general type that are commonly used in construction and/or concrete applications are shown in Jedick, U.S. Pat. No. 5,996,571, which is assigned to the assignee of the present application. As discussed in the Jedick '571 patent, the segments of such bits are commonly attached using laser welding techniques.
Generally speaking, diamond core drilling equipment comprises a motor-driven core drill assembly including a down-hole mining core drill bit or hole saw. The core drill assembly may embody various configurations, but such assembly generally comprises a base and a guide column extending up from the base or a drilling rig. A carriage may be provided between the column and the motor for guiding the motor along the column as the pipe extensions and mining core drill bit are advanced beneath the ground surface. Generally, the core bit is attached to the pipe extensions using a driver or reaming tool.
The prior art provides various types of core drill bits for use in mining. However, the majority of commercial mining bits used today have cutting heads formed of a diamond impregnated material. More particularly, the cutting head comprises a plurality of cutting segments or teeth mounted at the distal end of the cylindrical body of the bit. Each of the segments is attached to the cylindrical body of the bit using an infiltration process. This, however, is a time consuming operation, it is costly, and may at times result in inadequate adhesion of the segments with the body. Often, the infiltrated material “drips” onto unintended portions of the body and must be cleaned afterwards. A substantial investment of energy and time may be required to clean the tool of the stray brazing material.
The present invention provides a new and improved mining core drill bit or hole saw for cutting annular holes in rock, earth, concrete, masonry, stone, asphalt and similar materials and, further, includes methods of manufacturing these mining core drill bits. The drill bit and method of making the drill bit provide several distinct advantages over the bits and methods of the prior art. More particularly, the present invention provides a drill bit with a cutting head securely mounted to the tool body. Bits having this construction have a lower cost and exhibit a truer cut, better tracking, and a longer life as compared to prior art bits. The present invention also provides a method for constructing a core drill bit that is simpler than the prior art methods and provides a lower cost drill bit that exhibits a better adhesion or coupling between the cylindrical body of the bit and the one or more cutting segments. The method of the present invention also allows for the use of segments having varied compositions without concern for loss of bond integrity as between the segments and the bit body.
In one preferred embodiment, the mining core drill bit comprises an elongate hollow cylindrical body and a cutting head mounted thereto. The cylindrical body has a first end section and an opposite second end section. The first end section has an attaching portion for selectively attaching the core drill bit to an associated driver for rotating the core drill bit relative to an associated material such as rock, stone, earth, or the like. The second end of the cylindrical body has an end face defining an annular non-planar surface. The cutting head is mounted to the end face.
In one form, the cutting head includes a plurality of cutting segments mounted on the annular non-planar surface. In one form, the cutting segments are electrically welded to the annular non-planar surface. One preferred method of electrically welding the cutting segments includes capacitive discharge welding the segments to the annular non-planar surface. Essentially, the non-planar surface functions during construction of the drill bit to channel current through localized regions at the interface between the tool body end face and the cutting head segments to act as one or more current concentrators for localized high energy concentrations. The high heat and current in these regions cause portions of the non-planar end face surface to melt together with, in some cases, portions of the cutting head segments thereby realizing a sound and secure connection therebetween.
In another form, the plurality of cutting segments are circumferentially spaced apart on the annular non-planar surface defining alternating sectors of cutting segment regions and gap regions of the cutting head. After the cutting segments are electrically welded to the annular non-planar surface, the sectors of the cutting segment regions define end faces substantially planar and conforming to a surface of the cutting segment being in abutment with the cylindrical body. In the sectors of the gap regions, the end face of the cylindrical body has a non-planar surface.
In a further form, the end face includes at least one of a ridge and a groove but, preferably, the end face includes a plurality of concentric ridge and groove portions.
In its preferred form, the cutting segments comprise a mixture of iron, carbides and diamonds. In one such embodiment the segments comprise by weight a mixture of about 30% iron, about 30% copper, 30% cobalt, and 10% tungsten carbide; and with diamond particles/grit/powder of about 0-25% by volume added to the foregoing mixture.
In another form, the cutting head provided includes providing a cutting head including a plurality of cutting segments and, the mounting includes mounting the plurality of segments to the body by first circumferentially spacing the segments out about the non-planar surface and, thereafter, welding the plurality of cutting segments with the body. Preferably, the welding is performed using a capacitive discharge welder.
In its preferred form, the electrical welding includes welding the segments with the cylindrical body whereby first portions of the non-planar surface of the end face concentrate an amount of current per square inch flowing through the cutting head and the cylindrical body during the electrically welding step and melts the first portion and conforms the first portion to the rear side of the segments. Overall, this provides a sound and secure bond between the segments and the tool body.
In another form of the method of making a core drill bit, during the welding step the segments may be pressed with the cylindrical body using a pressure of about 6.6 Bar.
In still another form, the welding step includes electrically welding the cutting head with the cylindrical body using a burst of energy of about 16K joules.
In yet another form, the invention provides a reaming tool having cutting segments that are electrically welded to the body of the reamer.
The foregoing aspects and others will be pointed out more fully hereinafter in conjunction with the written description of the preferred embodiments of the invention illustrated in the accompanying drawings in which:
Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiments of the invention only and not for purposes of limiting same, and initially to
In the preferred embodiment illustrated, the cutting head 14 of the subject drill bit 10 comprises a plurality of cutting segments 30 mounted to the end face 24 of the body 12 such that the cutting head and the body are one unitary piece. However, it will be appreciated that one could form bit 10 by electrically welding a cutting head portion to a drill bit body. As with conventional bits, the cutting segments 30 are slightly wider than the body 12 so as to provide sufficient clearance for the body during mining, drilling, or cutting operations. The end face 24 includes a non-planar surface 26 to facilitate the mounting of the segments as discussed further below. Preferably, the cutting segments 30 are circumferentially spaced apart evenly on the annular non-planar surface 26 as best illustrated in
With continued reference to the drawing figures and, in particular, to
In the gap regions 36, the non-planar surface 26 is exposed on the second end section 18 of the tool body 12. The surface in the gap regions 36 has a shape and configuration corresponding to the shape and configuration of those surfaces prior to the electrical welding of the cutting head to the body. However, as best shown in
In its preferred form as best illustrated in
The cutting segments preferably comprise a mixture of iron, copper, cobalt and carbide, and optionally diamonds. In one preferred embodiment the segments comprise by weight a mixture of about 30% iron, 30% copper, 30% cobalt, 10% tungsten carbide. Diamond particles/grit/powder of about 0-25% by volume may be added to the mixture. Other compositions may be utilized as well. Additionally, when diamonds are utilized, the distribution of the diamond may be varied throughout the width and height of the segments in order to affect the cutting properties of the segments.
The segments may be produced in a conventional manner using conventional means preferably include a dispersion of diamonds with a particle size of between 40/50 US Mesh and about 30/40 US Mesh. This designates a diamond particle size such that about 460 to about 1,300 of such particles are equivalent to one karat.
Core drill bits of the preferred embodiment exhibit truer cuts, better tracking and a longer life as compared to conventional bits which include cutting segments attached to the tool body using brazing or other techniques.
During the welding operation the segments (welded one at a time) may be pressed using a pressing force F during the electrical welding operation as shown in
It is to be appreciated that although a pressing force F is described and a particular range of energy other pressing forces may be utilized and other ranges of energy may be required more or less based upon application and specifically the size and number of segments being welded. In the subject embodiment, by way of example only and not for purposes of limiting the preferred embodiments, the cylindrical body 12 has a diameter of about 3.0 inches and a longitudinal length of about 2.375 inches. Accordingly, scaling of the above-mentioned energy burst and/or pressing force F is to be expected.
Referring now to
The claimed invention has been described in connection with the preferred embodiments. However, it is to be appreciated that the embodiments of the invention have use in equipment other than mining equipment, and in other applications such as drilling concrete, asphalt, masonry and related materials. Obviously, alterations and changes may occur to those of ordinary skill in the art upon a reading and understanding of this specification and any appended claims.
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| Number | Date | Country | |
|---|---|---|---|
| 61142398 | Jan 2009 | US |
