Cutters – for shaping – Including tool having plural alternatively usable cutting edges – With integral chip breaker – guide or deflector
Reexamination Certificate
2000-03-02
2001-09-25
Tsai, Henry (Department: 3722)
Cutters, for shaping
Including tool having plural alternatively usable cutting edges
With integral chip breaker, guide or deflector
C407S115000, C407S116000, C407S023000
Reexamination Certificate
active
06293738
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to a thread cutting bit made of a carbide cutting material with a bearing face and a cover face essentially parallel to it, as well as with at least one face edge or cutting corner which, depending on the type of thread being cut, forms a profiled cutting tip, with cutting edges. Above the cutting faces is located a chip forming element with flanks, of which, in the manner of the steep walls of a spur or plateau, maintain a distance from the neighboring cutting edges that contain, enclose or includes the associated cutting faces. The term “spur” is used to provide a graphic description of the configuration of the chip forming element between the cutting faces located on a face edge or cutting corner. According to the “Brockhaus Enzyklopädie” [Brockhaus Encyclopedia] 1993, Volume 19, the geological feature called a “spur” is defined as a “projecting land form, generally steep-walled, in particular at the intersection between two deep valleys that intersect at an acute angle.” A triangular thread cutting bit of the known art with three geometrically identical faces and having the generic characteristics as indicated above is disclosed in WO 95/07159.
2. Background Information
The purpose of the thread cutting bit of the known art is to control the shaping of the chip by means of the geometric configuration of the respective cutting face that is in the engaged position, so that shorter chips are formed. The purpose of this type of operation is to prevent a clogging of the chip flute, which is hazardous for the operator. Consequently, this thread-cutting bit of the known art can also be used in mass-production operations where it is not constantly monitored by operating personnel.
The invention is based on the knowledge that when threads are being cut using conventional cutting bits, the surface of a cutting face is provided with a chip shaping stage that is shaped at an angle. Generally, such cutting bits are perforated, disposable bits having a triangular shape with a cutting face shaped onto each corner in the form of a thread profile tooth. When threads are being cut with such cutting bits, because the cutting or feed parameters can change either very little or not at all, very stable ribbon or mingled-up chips with a V-shaped cross section are formed, which have a very disruptive effect on CNC drilling machines that are installed in very tight spaces, as well as on the fabrication process as a whole.
OBJECT OF THE INVENTION
The object of the present invention is to propose another solution to this problem encountered with thread cutting bits of the known art.
A further object of the present invention, in at least one possible embodiment, is to substantially reduce clogging of the chip flute when different cutting or feed parameters are used.
SUMMARY OF THE INVENTION
The object of the present invention can be achieved in a substantially spur-shaped chip forming element that can project beyond the cutting faces in the manner of a table mountain or plateau, where the distance from each of the chip-forming element's flanks to the cutting edges is different, forming a broader cutting face on one side and a narrower cutting face on the other side. The present invention teaches that the spur-shaped chip forming element can project beyond the faces in the manner of a table mountain or mesa or plateau. In this case, the term “table mountain” is used as another graphic description of the shape of the chip forming element claimed by the invention, and is also borrowed from geology. According to the “Brockhaus Enzyklopädie,” Volume 21, 1993, the term “table mountain” is described as an “isolated, plateau-like form of mountain . . . with a surface that is generally flat like a table”.
An essential characterizing feature of the object of the present invention that distinguishes it from the known art described above is that the distances between the flanks of the spur-shaped chip forming element and the profile of the cutting edge on both sides of the chip forming element are different. A broader cutting face can be formed on the one side of the chip forming element, and a narrower cutting face can be formed on the other side. This shape has been found to be particularly appropriate for working the thread cutting bit with varied or modified flank feeds when cutting threads.
When cutting threads, there are essentially three different types of feed of the thread cutting tooth. There is a radial feed, a feed along the flank of the thread cutting tooth, and a combination between these two types of feeds. This combination is designated a “modified or altered flank feed” (see the applicant's promotional brochure 602.00 D entitled “Gewindedrehen”, or the English-language edition entitled “Threading”, 602.00 GB, page 39 in both versions). When the thread cutting bit of the present invention with modified or altered flank feed is used, the cutting edge of each cutting tip provided with the broader cutting face on the flank side that lies in the feed direction can be larger than the cutting edge on the flank side facing away from the feed direction. With a thread cutting bit designed as shown in at least one embodiment of the invention, and with a flank feed modified by approximately 3-5 degrees (see the applicant's brochure 602.00, page 39, left column in the figure with the title “Type of Feed”, 3rd figure from the top), it is possible to achieve a substantially short chip length. In this case, it is assumed that the cutting and feed parameters have been determined optimally for the material in question. In one economically efficient realization, the thread cutting bit claimed by the invention can be a triangular bit with three identical cutting tips, somewhat analogous to WO 95/07159. This embodiment can also be realized in the form of a thread chasing tool, in which case it will have different thread profile shapes.
The above discussed embodiments of the present invention will be described further hereinbelow with reference to the accompanying figures. When the word “invention” is used in this specification, the word “invention” includes “inventions”, that is, the plural of “invention”. By stating “invention”, the Applicants do not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicants hereby assert that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.
REFERENCES:
patent: 4131383 (1978-12-01), Powers
patent: 4218159 (1980-08-01), Langen
patent: 4278373 (1981-07-01), Wolfe, III
patent: 4669925 (1987-06-01), Lowe et al.
patent: 4681487 (1987-07-01), Pettersson
patent: 4993892 (1991-02-01), Takahashi
patent: 2254026 (1992-09-01), None
patent: 9507159 (1995-03-01), None
Catalog excert “Iscarthread” 1982.
Hartlohner Rudi
Prokop Hermann
Kennametal PC Inc.
Nils H. Ljungman & Associates
Tsai Henry
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