Abrading – Combined tool
Reexamination Certificate
1999-07-16
2001-03-06
Scherbel, David A. (Department: 3723)
Abrading
Combined tool
C451S259000, C408S145000, C408S206000, C408S207000
Reexamination Certificate
active
06196908
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to drills for drilling holes and, more particularly, to a diamond coated drill for drilling fiber reinforced composite materials.
BACKGROUND ART
In recent years, the use of fiber reinforced composite materials has been steadily increasing in many industries due to its lightweight and strength. As the use of such materials expands, there will be an increased need for a cost effective method of producing high quality holes in such materials with dimensions which are within narrow tolerances.
A number of problems arise in using known drilling and grinding techniques to produce holes in fiber reinforced composite materials. These problems include delamination and splintering of the materials and fiber breakout. Such phenomena are unacceptable in many applications for a number of reasons, including weakening of the structure through which the hole extends. Another reason is that in some applications the rear of the composite material cannot be easily accessed to prevent delamination and splintering or to remove the splintered material. For example, in long length fiber reinforced composite tubes, the inner surface of the tubes cannot be efficiently accessed to prevent fiber breakout or to remove the splintered material.
One conventional solution is to use special drills in combination with some kind of backing support. This approach is typically used with drills that rely on a sharp cutting edge. This is because these types of drills generally delaminate or fray the back side of the composite material as the drill is breaking through unless there is some support that keeps the backside surface in compression. Many cutting edge designs have emerged to eliminate the need for this backing support, but none have succeeded. For some structures, such as small diameter tubes, backing supports are not cost effective or easily used.
Another conventional solution is to implement a computerized numerical controlled (CNC) mill in a two step operation. First, an undersized hole is drilled with a drill that does not cause excessive delamination. Second, the CNC mill enlarges the hole using a diamond coated router. The desired size is achieved using a circle interpolation method. To be cost effective for the production machining of composite tubes, this method requires a large CNC mill to cover the full length of the tube. Even with a large mill, multiple set-ups and a trained machinist are required. Thus, the CNC mill approach is not cost effective for applications such as making repeatable, accurate, and clean holes in fiber reinforced composite tubes.
What is needed is a drill that does not require backing support or a CNC mill. The needed drill cannot cause fraying, splintering, fiber breakout, or delamination.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a diamond coated drill for drilling a composite material.
It is another object of the present invention to provide a diamond coated drill having a pair of prongs each having a tip for initiating a hole in a composite material, a grinder for grinding the hole, and a reamer for reaming the hole.
It is a further object of the present invention to provide a diamond coated drill having a pair of prongs each having a coarse grit diamond coated tip and grinder and a fine grit diamond coated reamer.
In carrying out the above objects and other objects, the present invention provides a drill for drilling a hole in a composite material. The drill includes a shank and a pair of prongs. The pair of prongs are diametrically opposed from one another and extend axially from the shank. Each of the prongs have a tip for initiating the hole. Each of the prongs further have a grinder disposed axially adjacent to the tip for grinding the hole. Each of the grinders have a tapered cylindrical surface axially tapering toward the tip and grinding means on the tapered cylindrical surface. Each of the prongs further have a reamer disposed axially between the grinder and the shank for finishing the hole. Each of the reamers have a constant diameter cylindrical surface and reaming means on the constant diameter cylindrical surface. The grinding means preferably include coarse grit diamond bonded to the tapered cylindrical surfaces of the grinders and the reamer means preferably include fine grit diamond bonded to the constant diameter cylindrical surfaces of the reamers.
The advantages accruing to the present invention are numerous. For instance, no delamination, fiber breakout, or splintering occurs throughout the process because the fiber reinforced composite material experiences a loading which extends radially from the drill rather than axially. Further, the composite material drilled by the drill naturally falls out of the drill during drilling.
The above objects and other objects, features, and advantages embodiments of the present invention are readily apparent from the following detailed description of the best mode for carrying out the present invention when taken in connection with the accompanying drawings.
REFERENCES:
patent: 4582458 (1986-04-01), Korb et al.
patent: 4720218 (1988-01-01), DeFries et al.
patent: 5069584 (1991-12-01), Obermeier et al.
patent: 5354155 (1994-10-01), Adams
patent: 5427477 (1995-06-01), Weiss
patent: 5466100 (1995-11-01), Ahluwalia
patent: 5645617 (1997-07-01), Frushour
Brooks & Kushman P.C.
Ojini Anthony
Scherbel David A.
Storage Technology Corporation
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