Patent Application
20080296069
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(1) Field of the Invention
The present invention is a drill bit for cutting materials such as concrete, asphalt, masonry, rock, stone and other similar materials. More specifically, it is a drill bit for cutting cylindrical holes wherein a core sample of the material being cut is produced.
(2) Description of Related Art
Presently there are a number of core drill bits available commercially. Some of these bits are disclosed in U.S. Pat. Nos. 5,069,584, 5,393,175, 5,996,571, and 7,204,244. However, the devices in these patents all provide a flat mounting platform secured perpendicular to the top of the cylindrical body for affixing the bit to a drill. In order to increase the strength of this design and to prevent the top from warping or the disengaging the platform from the cylindrical body the mounting platform is often made from heavier gauge metal than the cylindrical body. Unfortunately this adds a substantial amount of weight to the bit making manipulation of the bit difficult and requiring more energy to rotate the bit during cutting thereby reducing the life expectancy of the drill.
Consequently, there is a need in the industry for a core drill bit design that reduces warping and disengaging of the top plate from the cylindrical body.
The present invention provides a drill bit for cutting holes in materials such as concrete comprising a cylindrical body having a leading edge and a top edge, a conical top plate affixed to said top edge of said cylindrical body having an aperture about the center of said conical top plate and a threaded nut affixed through said aperture of said top plate, said leading edge able to receive one or more cutting or abrasive pads for cutting cement or stone and said threaded nut having a shaped upper portion and a cylindrical shaped lower portion.
In one embodiment the drill bit further comprises a brace wherein the brace is donut shaped having an internal perimeter and external perimeter. The internal diameter of the internal perimeter allows the cylindrical shaped lower portion of the nut to extend through the brace. The exterior perimeter of the brace is affixed to the conical top plate and the internal perimeter is affixed to the cylindrical portion of the nut.
In another embodiment the conical shaped top plate forms an angle between the cylindrical body and the conical top of not less than 2 degrees and not more than 35 degrees. The conical shaped top plate may be provided in a conical domed shape.
In another aspect of the present invention a method of cutting cement or stone is provided using a drill bit comprising a cylindrical body having a leading edge and a top edge. A conical top plate having an aperture about its center is affixed to the top edge of the cylindrical body. A threaded nut is affixed through the aperture of the conical top plate for attaching the bit to a drill. The leading edge is able to receive one or more cutting or abrasive pads for cutting through cement or stone. The threaded nut may be provided in a number of configurations but is preferably a hexagonal shaped on the upper portion and cylindrical shaped on its lower portion. This method may also be provided for cutting stone or cement wherein the drill bit further comprises a brace and/or wherein the conical top plate is a domed conical shape.
Unless defined otherwise, all terms used herein have the same meaning as are commonly understood by one of skill in the art to which this invention belongs. All patents, patent applications and publications referred to throughout the disclosure herein are incorporated by reference in their entirety. In the event that there is a plurality of definitions for a term herein, those in this section prevail.
The term “affixed” as used herein refers to securing one element of the invention to another element by a variety of methods known to one skilled in the art such as for example welding, brazing or soldering. Preferably elements of the present invention are welded together.
The present invention is a drill bit for cutting holes in materials such as concrete comprising a cylindrical body having a leading edge, a top edge and a conical top plate. The top plate has an aperture about its center and is affixed to the top edge of the cylindrical body. A threaded nut having a shaped upper portion and a cylindrical shaped lower portion is affixed through the aperture of the top plate for connecting the bit to a drill. The leading edge is able to receive one or more cutting or abrasive pads for cutting concrete or stone.
Cylindrical Body
The cylindrical body 12 may be provided in a variety of diameters and lengths depending on the size and depth of the holes to be created. For example, the drill bits may be provided in a number of standard diameter sizes such as 6, 12, 18, 24, 30, 36, 42, 48 or 54 inches. Alternatively, drill bits may be custom made to a particularly desired diameter. In addition, a number of standard lengths may be provided such as 6, 8, 10, 12, 18 or 24 inches. Correspondingly, custom lengths can also be prepared as desired.
The materials used to prepare the cylindrical body 12 must have sufficient strength and durability to reduce bending and prevent shearing. Materials such as steel, e.g. mild steel or stainless steel may be used to construct the cylindrical body 12. The thickness of the material used will depend on the type of material, the forces and pressures anticipated when cutting concrete or stone and the size of the cutting or abrasive pads that will be affixed to the leading edge. If steel is used to prepare the drill bit the thickness for bits having diameters from about 3 inches to about 6.25 inches is about 0.050 to about 0.083 inches. For diameters of about 6.50 to about 16 inches, the thickness is about 0.120 to about 0.134 inches, and for diameters of about 16 inches and above, the thickness is about 0.134 to about 0.250 inches.
The cylindrical body 12 may be prepared from tubular or sheet stock material. If tubular stock is available, the drill bit body may be provided by selecting the desired diameter and cutting the tubular stock to the desired length. The top and bottom edges of the cylindrical body 12 thus formed are then faced on a lathe to ensure that they are concentric. If sheet stock material is utilized to prepare the cylindrical body 12 the width of the sheet for a given diameter may be determined by the following equation:
Width=(desired tube diameter−thickness of the sheet stock)×Pi
The length of the sheet is the desired length of the drill bit. Once cut the sheet is rolled on a rolling machine until the lengthwise sides are close to touching each other. The rolled sheet is then compressed so that the sides are touching and welded in several locations along the seam. The tack-welded tube is then placed in a seam welder (Jetline Seam Welder Irvine, Calif.), to uniformly weld the entire length of the seam. The tube may then be placed in a planisher to press the welded area flush and to ensure that the tube is round. The cylindrical body 12 thus formed is then placed in a lathe and both the top and bottom ends are faced to ensure that they are concentric.
Conical Top Plate
The conical top plate 14 is preferably made of the same material as the cylindrical body 12. The angel formed between the underside of the top plate 14 and a the plane created by the top edge of the cylindrical body 12 is not less than about 2 degrees and not more than about 45 degrees. Preferably this angle is not less than about 5 degrees and not more than about 35 degrees and most preferably the angle is about 10 degrees. The diameter of the conical top plate 14 will depend on the angle between the top edge and the underside of the top plate 14. The diameter can be determine by the following equations:
A
2
+B
2
=C
2
wherein A is the length from the center of the conical top plate 14, B is the length from A to the interior sidewall of the cylindrical body 12 forming a 90 degree angle with A and C is the hypotenuse of this right triangle. The diameter of the conical top plate 14 is then twice the radius or:
2×C=Diameter of the top plate
The actual radius desired may be greater then that calculated when overlap is desired so that the welded area between the conical top plate 14 and the cylindrical body 12 may be milled flush with the exterior side of the cylindrical body 12.
The top plate 14 in commercially available drill bits for cutting annular holes in concrete, asphalt, rock or stone are positioned perpendicular to the drill body and therefore are required to be made of a thicker stock sheet material than the body (see U.S. Pat. Nos. 5,069,584, 5,393,175, 5,996,571 and 7,024,244). This design increases the weight of the drill bit making manual manipulation difficult and increases the forces during drilling that can shear the top from the body of the drill bit. In the present invention the conical shape provides additional structural integrity during drilling that allows the top plate 14 to be made of stock material that is less than or equal to the thickness of the cylindrical body 12. This configuration significantly reduces both the overall weight of the drill bit and the shear forces between the top plate 14 and the cylindrical body 12. While the conical shape is preferred other shapes such as a domed shape could also be utilized for the top plate 14 in the same manner to increase the structural integrity of the drill bit.
The exterior perimeter edge of the top plate 14 may be modified to more tightly receive the cylindrical body 12. In one configuration the exterior perimeter edge is grooved so that the top edge of the cylindrical body 12 fits flush against the top plate 14 as seen in
The top plate 14 also comprises a centrally located aperture 16 or hole through which one end of a threaded nut 18 may be press fit and then affixed to the top plate 14. This aperture 16 may be provided in a variety of desire shapes including for example triangular, square, pentagonal, hexagonal or circular. Preferably the aperture 16 is circular. The diameter of the aperture 16 will depend on the size of the threaded nut 18 required to enable the drill bit to be affixed to a desired drill. The threaded nut 18 may range from ½ to 2 inches in diameter. Consequently, depending on the threaded nut 18 desired, the aperture 16 will have an identical diameter or a slightly smaller diameter so that the nut may be securely press fitted in to the top plate 14 prior to affixing. Preferably the threaded nut 18 is welded into place on the top plate 14.
Threaded Nut
The threaded nut 18 affixed to the top plate 14 may be provided in a variety of sizes, shapes and number of threads per inch. Preferred nut sizes are from about ½ inch to about 2 inches having from 6 to 20 threads per inch. The actual size of the nut 18 and the number of threads per inch will depend on the drill shaft on which the drill bit will be connected during use.
The threaded nut 18 may be prepared from solid or tubular stock material having the desired external configuration. In a preferred configuration the threaded nut 18 is prepared from tubular stock material having an external hexagonal shape. A desired length of stock material is cut for preparation. The internal perimeter is then tapped to provide the desired number of threads per inch. If the aperture 16 in the top plate 14 is circular, the exterior of one end of the nut 18 is turned on a lathe so that it too is cylindrical having the same or slightly larger diameter for press fitting into the aperture 16. If solid stock is used, the desired length of stock material must first be drilled to provide the desired opening for tapping.
The threaded nut 18 may be prepared from solid or tubular stock that does not provide the desired external configuration but which can be obtained during fabrication. For example, two parallel grooves to receive the jaws of a open ended wrench may be desired as opposed to a hexagonal configuration. If cylindrical tubular stock is utilized a desired length for the nut 18 is cut from the stock. The internal perimeter is then tapped to provide the desired threads per inch. One end of the nut 18 is turned to provide the desired diameter for press fitting into the top plate 14. The grooves are then cut into the other end for receiving the open-ended wrench so that the drill bit may be securely connected to the drill. If solid stock is used, the desired length of stock material must first be drilled to provide the desired opening for tapping.
Brace
The brace 22 may be utilized to add additional structural integrity and support at the bottom of the top plate 14. It is provided with a central aperture 16 being of the same or slightly smaller diameter than the portion of the threaded nut 18 extending through the top plate 14. A variety of shapes may be utilized that provide additional strength to the top plate 14 when welded in position including a circular donut shape, triangle shape, square shape, pentagon shape or the like. The brace 22 may be constructed from sheet stock material of a variety of thickness'. Preferably the thickness is the same or less than the stock material used to construct the cylindrical body 12. Once prepared the brace 22 is placed over, or press fit onto, the end of the threaded nut 18 that extends through the top plate 14. The interface between the threaded nut 18 and the brace 22 is fused preferably by welding to secure the brace 22 to the threaded nut 18. The exterior perimeter of the brace 22 is then fused to the bottom of the top plate 14. If the brace 22 is provided in a circular donut shape it is preferable that the entire exterior perimeter be fused to the bottom of the top plate 14 preferably by welding. Alternatively, it may be spot welded in two or more places along the perimeter of the brace 22 to secure the brace 22 to the bottom of the top plate 14. Correspondingly, if the brace 22 is provided in a geometric shape, the points of the braces geometric shape that contact the bottom of the top plate 14 may be spot-welded to the top plate 14.
Cutting or Abrasive Pads
A variety of cutting or abrasive pads are available commercially for affixing to the leading edge of the drill bit. The core bit manufacturer often provides these abrasive pads. Methods for preparing such pads are disclosed in U.S. Pat. Nos. 5,996,571 and 7,204,244 and are incorporated herein by reference. The width of the material used to construct the cylindrical body 12 of the drill bit of the present invention will assist in determining the size or width of the pad or pads to be affixed to the leading edge. The pads may be affixed permanently or removably. If removable, the pads may be replaced when they become worn or if different types or sizes of cuts are desired.
A. Cylindrical Body Construction from Sheet Stock
A drill bit that is 8 inches in diameter having a length of 15 inches will be prepared with a wall thickness of 0.120 inches. Obtain a sheet metal stock steel of thickness 0.120 inches. The width of the sheet to be cut is determined by the formula (Diameter−Width of sheet stock)×pi (3.1416) of (8 inches−0.120 inches)×3.1416=24.7423 inches. The length of the sheet stock will be the length of the desired cylindrical body of the drill bit to be prepared or 15 inches.
This sheet of dimensions 24.7423 inches by 15 inches is placed in a rolling machine (Wysong, Los Angeles, Calif.) consisting of either 2, 3 or 4 rolls with varying roll diameter and length. The rolling process will continue until the sheet stock is cylindrical and both 15-inch side lengths are close together. The rolled tube is then removed from the machine and compressed to bring the 15-inch side lengths into contact. Once flush the seam is tack welded in several places. The cylindrical tube is then placed in a seam welder (Jetline, Irvine, Calif.) to uniformly weld the seam. Once completed the welded cylindrical tube is place in a planisher (Jetline, Irvine, Calif.) that will press the welded seam flush with the surface of the cylindrical tube and ensure that the tube is round. When this process is completed the cylindrical body is turned on a CNC lathe (HwaCheon Los Angeles, Calif.) to reface the top and leading edges to assure that they are concentric.
B. Construction of Top Plate from Sheet Stock
Cut sheet stock material of thickness 0.120 inches into a circular plate having a diameter approximately 0.125 inches greater than that of the diameter of the cylindrical body or 8.125 inches. Place the circular plate into a die in a 200 to 400 ton press shaping the disc into a cone. The rise of the cone forming a 10-degree angle from a horizontal plate created by the cone's perimeter edge.
An aperture is then machined into the center or apex of the cone having the same or slightly smaller diameter than the threaded nut to be received in the aperture.
The nut is prepared from stock material having either a square, round or hexagonal exterior surface configuration. The stock material is cut to the desired length and placed in a CNC Lathe or Mill (HwaCheon, Los Angeles, Calif.). This length is generally a sufficient amount extending above the top surface of the top plate to provides an adequate amount of threads for securing the drill bit to the drill and a sufficient amount extending through and below the bottom surface of the top plate to affix a brace if desired. Preferably the amount of threaded nut extending above the top surface of the top plate is between about 0.50 to about 3.0 inches depending of the diameter of the drill bit. The minimum amount of the threaded nut extending through and below the bottom surface of the top plate can be determined by the equation:
A+(thickness of the sheet stock material used to construct the top plate)=length of the nut desired
wherein A is determined by the equation:
A
2
+B
2
=C
2
and A is the shorter side forming the right angle with B.
The stock material is machined with the proper internal diameter and thread number required for the drill on which the drill bit will be secured for use. One exterior end of the threaded nut is machined to a desired cylindrical diameter for inserting into the aperture of the top plate.
The cylindrical end of the threaded nut is then inserted or press fit into the aperture of the top plate and welded along the entire interface between the cylindrical portion of the nut and the bottom of the top plate.
If a brace is desired, sheet stock material of thickness 0.120 inches or less is cut into a circular plate having a diameter approximately one-half the diameter of the top plate or 4 inches. An aperture is then machined into the center of the circular disc having the same or slightly smaller diameter than the threaded nut to be received in the aperture.
The brace is then placed on or press fit onto the end of the threaded nut extending through the top plate such that the external perimeter edge of the brace is contacting the bottom surface of the top plate. The entire interface between the threaded nut and the brace as well as the brace and the top plate are welded securing the brace in position.
The top plate containing the nut is then placed in a CNC lathe (HwaCheon, Los Angeles, Calif.) wherein a groove is machined into the perimeter edge of the top plate so that it may be tightly press fit into the top edge of the cylindrical body. The entire interface between the top plate and the cylindrical body is welded. This welded area can be further milled to provide a uniform flush surface between the top plate and the cylindrical body.
