Boring or penetrating the earth – Bit or bit element – With helical-conveying portion
Reexamination Certificate
1998-06-26
2001-04-10
Schoeppel, Roger (Department: 3672)
Boring or penetrating the earth
Bit or bit element
With helical-conveying portion
C175S401000, C175S413000, C175S399000
Reexamination Certificate
active
06213231
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to boring tools and, more particularly, to a reversing cut plate equipped boring tool.
BACKGROUND OF THE INVENTION
A reversing cut plate-equipped boring tool is described, for example, in EP 0 750 960 A1. This boring tool has a borer body which has a shaft arranged for fastening to a corresponding chuck on one end and two plate seats on its other end. On the plate seats there are held essentially square reversing cutting or cut plates each having four cutting edges which are constructed. The cutting edges are bent slightly concave in order to smooth the bore wall definitively with a side blade, which engages the bore wall solely with a corner or a short section.
The two reversing cut plates held on the face side of the boring tool in corresponding plate seats overlap reciprocally on the tool face. With this arrangement, in particular, the sections of the cutting edges following upon the corner blades act with a shaving removing effect. The exact relations of the two reversing cut-plates are dependent on the borer diameter and, accordingly, on the extent to which the reversing cut plates overlap. Furthermore, with square reversing cut plates of a given size, more than two reversing cut plates are required if the borer radius is greater than twice the edge length of one reversing cut plate.
Boring tools with reversing cut plates are also known from WO 93/02824. This boring tool has a borer body with two face-side plate seats on which there are held rotating cut plates essentially rectangular in shape. Specifically, on the rotating cut plate there are formed two shorter concavely curved cutting edges lying opposite one another, which over an arcuately curved projecting corner blade extend into similarly concave-constructed longer flanks which do not function as a cutting edge. The reversing cut plates are thus attuned in their size to the borer diameter in such manner that the radially farther outside positioned reversing cut plate stands with its inside-lying corner blade approximately in the area of the middle of the cutting edge of the reversing cut plate arranged radially inside. Therefore, the machining is concentrated mainly in the areas near the corner of each cutting edge, whereas the middle sections are largely unburdened.
A boring tool with triangular cutting plates is known from DE 4018043 A1. With this boring tool each cutting edge is constructed either arcuately convex or with a corresponding jog. With corresponding overlapping of several cutting edges on the reversing cut plates provided on the borer face side, a blade extending in a corrugated or in zig-zag manner is produced. The radially inside-arranged cutting plate extends with its corner edge somewhat beyond the axis of rotation. The point lying furthest forward axially, however, forms approximately the middle of the cutting edge of this reversing cut plate. This point lies at a relatively great distance from the axis of rotation. This can result in problems when starting a boring operation. Furthermore, the use of the same reversing cut plates on boring tools having different diameters can lead to different amount of overlapping of the reversing cut plates. As a result of their convexly curved or convexly bent geometry, the edges of the reversing cut plates come into engagement with the work piece in ever shorter sections which can lead to non-uniform stresses on the cut plates and the boring tool.
As general rule, cutting plates are designed for the borer, i.e. for the basic tool, for which they are provided. Thus, for different tool diameters, for right-spiral tools and for the left-spiral tools different cutting plates must be provided. As will be appreciated, this presents a significant economic burden.
Furthermore, in many boring tools, the cutting plates are set in such a way that during the machining process a radial force is produced which deflects the basic tool body in a radial direction. This leads to an increase of the bore diameter, which is otherwise dependent on the length of the tool, on the turning rate of the tool, and on the material removed.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, in view of the foregoing it is an general object of the present invention to provide a boring tool which can be used economically and provides good processing quality.
An additional object of the present invention is to provide a boring tool as characterized above which enables reversing cut plates to be used when the boring tool has a relatively small diameter.
A further object of the invention is to provide a boring tool of the foregoing type which has an improved useful life regardless of the diameter of the boring tool.
Still another object of the present is to provide a set of boring tools which can utilize the same reversing cut plates.
The present invention provides these and other advantages and overcomes the drawbacks of the prior art by providing a boring tool which has at least one, but preferably two rectangular plates, which have in each case a total of four edges. The two cutting edges lying opposite one another, of which one is active, i.e. is arranged on the face side of the borer, are entirely straight, i.e. constructed without curvature or jog. Active cutting edges are formed by the shorter and/or longer cutting edges of the rectangular plate, these active cutting edges are arranged approximately perpendicular to the longitudinal axis or axis of rotation of the borer. Alternatively, the cutting edges may also be slightly inclined with respect to the rotational axis of the borer.
In addition, the longer edges are preferably constructed completely straight, i.e. without jog or bend. The combination of a long straight cutting edge and with a short straight cutting edge permits the reversing cut plate to be selectively installed lengthwise or transversely in order to sweep a greater diameter range.
If the two longer cutting edges are used, an even greater sweeping of the diameter ranges of a reversing cut plate size is achieved. Through the straight construction of the overlapping cutting edges it is possible, with corresponding arrangement of the active cutting edges in the borer body, to achieve the result that independent of the extent to which the two reversing cut plates held on the borer overlap, i.e. independent of the borer diameter, the two active cutting edges are able to come into engagement over their entire length with the material of the work piece and accordingly act to remove the material. This increases the useful life of the boring tool. This advantage applies for both rectangular and also for slightly rhombic reversing cut plates.
Preferably, however, the reversing cut plates are constructed rectangular, i.e. in each case having a long and a short straight-constructed cutting edge which are connected to one another at a corner at a right angle. Reversing cut plates having such a configuration are particularly stable. Additionally, such reversing cut plates enable an improved distribution of the forces onto the plate seat and an increased spacing between the thread bore and the corner of the borer body. Thus, the danger of breakage of the borer body is reduced. Through the axially longer plate there is yielded a lower surface force and an improved reduction of non-uniform load distributions.
The rectangular cutting plates also can be used with both right-spiral and left-spiral tools, which can belong to one tool set. It is thus possible for many diameters and many tool types (i.e., right and left spiral) to utilize one cutting plate construction and size.
The reversing cut plate is preferably held by means of a fastening screw which grips through the reversing cut plate centrally at a fastening bore.
The two reversing cut plates of a borer tool are preferably arranged in different radial positions. In this arrangement one cutting plate connects to the outer circle of the boring tool and defines the latter, while the other reversing cut plate connects to the axis of rotation. The cutting relations of the reversing cu
Leydig , Voit & Mayer, Ltd.
Schoeppel Roger
Walter AG
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