Cutting by use of rotating axially moving tool – Processes – Bit detachable
Reexamination Certificate
2000-06-26
2001-10-23
Howell, Daniel W. (Department: 3722)
Cutting by use of rotating axially moving tool
Processes
Bit detachable
C408S080000, C408S204000, C408S201000
Reexamination Certificate
active
06305885
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the problem of guiding a hole cutter when enlarging an existing hole. More particularly this invention relates to the use of a simple disc which centers the larger hole cutter in the existing hole and a disc retention means which ensures that the disc does not fall unretrievably into the enlarged hole.
BACKGROUND OF THE INVENTION
The inventor is an electrician who has been involved in residential construction and remodelling. When the need arises to enlarge an existing hole some means of maintaining the pilot drill in the center of the existing hole must be provided for.
There are a number of relatively elaborate devices to center a pilot drill in an existing hole. Compared to a simple disc, which can only partially slide into an existing hole, these are expensive to manufacture and heavy to carry around. The problem with a simple disc however, is that if it is used to enlarge an existing hole in a wall—once the hole is cut, the disc, together with the round cut out piece may fall down into the wall where it cannot be recovered. Another problem with a simple disc is that it is difficult to hold in an existing hole while cutting. When a large diameter hole is being cut it is common for the cutting teeth to catch in the workpiece twisting the drill out of axial alignment in the hands of the user. When cutting in wood it is not uncommon to break pilot bits. When cutting in sheetrock the result is an enlarged pilot hole and a roughly cut hole.
U.S. Pat. No. 5,871,310 issued to R. Mortensen discloses the use of a tapered dowel plug. One problem with the tapered dowel plug is that it may vibrate loose in sheetrock or other workpieces. In other workpieces if it is able to be jammed into the existing hole sufficiently so that it does not vibrate or wrench free during the cutting process, then it must be subsequently removed for reuse. Yet another problem is that the tapered dowel plug, together with the cutout piece, may fall into the interior of a wall where it cannot be recovered.
OBJECTS OF THE INVENTION
It is an object of this invention to disclose an apparatus which utilizes a thin disc, and a disc bias means to center and maintain the drill bit in an existing hole. It is an object of this invention to disclose an apparatus which is simple and inexpensive to manufacture, and lightweight to carry around. The disc bias means adequately maintains the disc in the existing hole only during use; subsequently the disc is readily removed for reuse. Additionally, compared to other technologies, the thin disc is less likely to break the drill bit if the drill bit twists out of axial alignment when the hole cutter catches in the workpiece. It is yet a final object of this invention to disclose an apparatus which employs a retention means to prevent the hole enlargement apparatus from falling into the interior of a wall, where it would be practically unretrievable.
One aspect of this invention provides for a hole enlargement apparatus used to increase the diameter of an existing hole in a workpiece for use in conjunction with a conventional large hole cutter of the type having a cylindrical cup having a toothed peripheral rim, a hub axially secured in a bottom portion of the cup, and a pilot bit axially and removably secured through the hub and cup. The hole enlargement apparatus comprises: a guide member having a disc portion dimensioned to matingly fit within the existing hole, a rim portion connected to a rear portion of the disc portion adapted to seat on the workpiece, and a disc center guide opening dimensioned to slidingly accept a shaft the diameter of the pilot bit; a drill bit replacement shaft having a hub end portion and an opposite disc end portion; disc retention means carried by the disc end portion of the drill replacement shaft to prevent the guide member from sliding off the disc end portion of the shaft; and, a spring to bias and maintain the disc portion in the existing hole. In use the guide member is selected to mate within the existing hole and then slid onto the drill replacement shaft; the disc bias means is next slid onto the shaft; and then the shaft is inserted through and secured in the hub carrying the toothed cup having the desired diameter of the enlarged hole; so that the disc portion of the guide member may be fitted into the existing hole and so that the rim portion seats around the existing hole; so that when forward rotational thrust is applied to the drill bit replacement shaft the guide member will be biased and maintained in the existing hole and the rotating peripheral teeth will cut the enlarged hole.
In a preferred aspect of this apparatus the peripheral edge of the disc portion of the guide member is tapered to ensure a tight fit within and accommodate minor variations in the existing hole size.
Various other objects, advantages and features of this invention will become apparent to those skilled in the art from the following description in conjunction with the accompanying drawings.
REFERENCES:
patent: 3266345 (1966-08-01), Weisner et al.
patent: 4749315 (1988-06-01), Mills
patent: 4968189 (1990-11-01), Pidgeon
patent: 5413437 (1995-05-01), Bristow
patent: 5871310 (1999-02-01), Morternsen
patent: 6048141 (2000-04-01), Freeman
Gallinger G. F.
Howell Daniel W.
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