Cutting by use of rotating axially moving tool – Tool or tool with support – Hollow milling tool
Reexamination Certificate
1999-11-23
2001-08-14
Howell, Daniel W. (Department: 3722)
Cutting by use of rotating axially moving tool
Tool or tool with support
Hollow milling tool
C408S204000, C408S205000
Reexamination Certificate
active
06273652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plug cutters. More specifically, the present invention relates to plug cutters with cutting blades containing a radial relief so that, while the plug cutter is cutting a plug from a piece of stock, the cutting blades are less likely to burn the outer surface of the plug and the plug is less likely to break away prematurely from the piece of stock.
2. Description of the Related Art
There are two types of conventional plug cutters, those that do not have radially relieved portions on the cutting blades and those that do.
Both types of plug cutters typically include a main body portion with a shank extending from one end along the cutter's axis of rotation. They also include a plurality of cutting tines, or blades, extending axially from the opposite end of the main body. The plurality of cutting tines define a bore that is circular in cross section. The configuration of the bore corresponds to the configuration of the plug produced with the plug cutter.
Both types of plug cutters typically are produced, first, by drilling a bore axially into a cylindrical piece of steel and, second, by milling the cutting blades out of the resulting annular wall surrounding the bore. Each blade has an inner surface that faces radially inwardly toward the center of the bore.
For plug cutters that do not include radially relieved portions on the interior surfaces of the blades, the entire inner surface of each blade lies at a constant radial distance from the center of the bore. In other words, the entire inner surface of each blade contacts the outer surface of the plug as it is being cut from the stock material.
At the speeds with which plug cutters rotate, contact between the inner surface of the blades and the outer surface of the plug can generate a sufficient amount of frictional heat to burn the outer surface of the plug. In addition, friction between the outer surface of the plug and the inner surface of the blades can generate a sufficiently large torque on the plug to cause the plug to break away prematurely from the stock and become lodged in the bore of the plug cutter. Should this occur, the plug may be removed from the plug cutter only by destroying the plug.
It is also true that, in plug cutters that do not include radially relieved portions on the interior surfaces of the blades, because the entire inner surface of the each blade contacts the outer surface of the plug, the outer surface of the plug is formed by shearing, rather than by cutting. This results in the creation of a plug with a rough outer surface.
For plug cutters that do include radially relieved portions on the inner surfaces of the blades, such as those described in U.S. Pat. No. 5,810,524 (the '524 Patent), which is incorporated herein by reference, the inner bore of the plug cutter is not perfectly circular. Instead, a radial relief is provided on at least a portion of the inner surface of each blade between the leading and trailing edges. As described in the '524 Patent, the radially relieved portions establish a gap between the inner surface of the blades and the plug so that only a portion of the interior surface of the blades contacts the outer edge of the plug. This minimizes the effect of frictional and torsional forces on the plug and improves the plug cutter's performance so that it may produce a higher quality plug (for example, a plug with little or no surface burning or roughness).
Traditional plug cutters have one further disadvantage. After being cut from the stock material, the only way to remove the plug from the conventional plug cutter is to extract the plug from the radial end of the bore. Naturally, if the plug becomes lodged within the bore or cannot be easily removed from the bore, valuable production time may be lost while an operator takes the time to dislodge the plug from the cutter. Often, manual removal of the plug results in damage to the plug or to its destruction.
To facilitate removal of plugs from the central bore in the conventional plug cutter such as the one described in the '524 Patent, the central bore may be slightly tapered so that the diameter of the bore at the tips of the blades is slightly larger than the diameter of the bore closest to the shaft. With an outwardly tapered bore, an operator can remove the plug more easily from the bore of the plug cutter after it has been cut from the stock material. Additionally, with a slightly tapered bore, the plug may slide more easily out of the end of the plug cutter when the cutting operation is completed.
SUMMARY OF THE INVENTION
The present invention avoids the above-described disadvantages encountered with both of the conventional plug cutter designs by combining a radial relief on a portion of the inner surface of each blade with a plug ejecting portion. As the prior art illustrates, the radial relief improves the quality of plugs cut from stock material. The plug ejecting portion permits a plug, once cut from the stock material, to be pushed down the bore of the plug cutter toward the shaft until it can be removed from the side of the cutter through the plug ejecting portion. In cases where the plug is less than 1 inch thick, the plug may self-eject from the plug cutter through the plug ejecting portion as a result of the rotation of the plug cutter without any intervention by an operator.
Therefore, according to the present invention, a plug cutter is provided that is rotatable about an axis of rotation. The plug cutter includes a main body that has a longitudinal axis coinciding with the axis of rotation. The main body defines a bore extending axially therein. A shank extends axially from one end of the main body along the axis of rotation. A plurality of cutting blades extend axially from an opposite end of the main body and terminate in a distal end. The plurality of blades are adapted to cut a plug from a piece of stock as the plug cutter is rotated about the axis of rotation and advanced axially into the piece of stock. Each of the blades has leading and trailing edges and also an inner surface and a radially relieved portion facing the bore. The radially relieved portion begins at a relief start position and ends at a relief end position so that, as the plug cutter is cutting the plug, a gap is defined between an outer surface of the plug being cut and the radially relieved portion. The plug cutter also includes a plug ejecting portion extending through the main body to permit removal of the plug from the plug cutter.
Further in accordance with the present invention, a plug cutter is provided that is rotatable about an axis of rotation. The plug cutter includes a main body that has a longitudinal axis coinciding with the axis of rotation. The main body defines a bore extending axially therein. A shank extends axially from one end of the main body along the axis of rotation. A plurality of cutting blades extend axially from an opposite end of the main body and terminate in a distal end. The plurality of blades are adapted to cut a plug from a piece of stock as the plug cutter is rotated about the axis of rotation and advanced axially into the piece of stock. Each of the blades has leading and trailing edges and also an inner surface and a radially relieved portion facing the bore. The radially relieved portion begins at a relief start position and ends at a relief end position. Each blade is shaped so that, at a given axial position along each blade, a radial distance from the axis of rotation is smallest along the inner surface and largest along the radially relieved portion, so that, as the plug cutter cuts the plug, substantially only the inner surface of each blade contacts with an outer surface of the plug. The plug cutter also includes a plug ejecting portion extending through the main body to permit removal of the plug from the plug cutter.
Other objects, features and characteristics of the present invention will become apparent upon consideration of the following description and the appended claims wi
Brutsman Paul
McCool Mark K.
Sanger Jay L.
Wirth, Jr. John
Howell Daniel W.
Pillsbury & Winthrop LLP
Woodworker's Supply
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