EP0778391A2 - Rotary percussive twist drill - Google Patents

Abstract

The rotary percussion drill has the spiral fluting for cuttings, and a cutter plate at the end of the shaft. This is broadly X-shaped and fixed into the shaft with axial and radial projection. Additional cutters (11) are mounted peripherally in the cutter plate (6), with axial and/or radial projection. With respect to the direction of rotation, the angle between the additional cutters and the trailing cutter plate (6) is less than 90 degrees and each additional cutter (11) a preceding main clearing groove (4,5). Additional clearing grooves are provided, which trail the additional cutters. The radial projections of the cutter plate amount to at least 50 per cent of that of auxiliary cutters.

Description

The invention relates to a rotary impact twist drill according to the generic preamble of claim 1.

Rotary impact twist drills are drilling tools that are used in connection with axial impact supported rotary drilling rigs. In particular, these are generally rock or masonry drills that can be used for the rotary striking drilling or breakthroughs in concrete or masonry. From DE-C-30 20 284 a twist drill for drilling work in solid rock is known, which has a drill shank with two spirals running on the shaft for the drilling dust. Tungsten carbide cutting edges are provided at the end of the shaft that chisel and abrasively process the surface to create a borehole. The hard metal cutting edges are arranged in a cross shape in the end face of the shaft end and project axially beyond the end face. In particular, the hard metal cutting edges are provided on the one hand on a continuous hard metal plate which extends over the diameter of the drill shank, and on additional hard metal elements which are arranged along a diameter of the shank which is at 90 ° to the hard metal plate. Between the main cutting edges arranged on the hard metal plate and the additional cutting edges, grooves are provided which are essentially axially parallel to the shaft and which open into the removal grooves on the shaft. These serve to remove the drilling dust generated during the abrasive processing of the substrate. The main and additional cutting edges also have a radial projection over the sheath of the shank in order to prevent the drilling tool from jamming in the bore. This well-known twist drill allows a moderate drilling performance with reasonable wear of the hard metal cutting edges.

From EP-B-0 452 255 a rotary impact twist drill is known which has a cutting plate arranged along a diameter of the shank and additional cutting edges formed by hard metal pins, each of which has an axial and a radial one Have protrusion over the shaft. The main cutting edges of the drilling tool are provided on the carbide cutting tip. The additional cutting edges are axially set back compared to the main cutting edges and essentially only perform guiding functions for the drilling tool. In this improved rotary impact twist drill, the main and additional cutting edges are arranged at an angle other than 90 °. In particular, the arrangement is selected such that, based on the direction of rotation of the drilling tool, the additional cutting edge leading the cutting insert forms an angle with it that is greater than 90 °, while the additional cutting edge following the cutting insert includes an acute angle with it. This embodiment has the advantage that the area which is upstream of the respective main cutting edge is expanded and allows the opening of a broadened main process. In the narrower area, towards the trailing additional cutting edge, a narrow additional handling is also provided. In this "X-like" arrangement of the cutting insert and the secondary cutting edges, the widened main discharge guides in front of the cutting insert ensure improved drilling dust removal and adequate guidance is provided by the additional cutting edges.

However, there is a desire to further improve the drilling performance of the rotary impact twist drill. In particular, the prerequisite should be created in order to be able to optimize the insert and the additional cutting edges with regard to their specific stress. It should be noted that the central part of the hard metal cutting plate is subjected to different loads due to the axial impacts of the rotary impact drill than the peripheral areas of the cutting plate or the additional cutting edges, on which primarily shear forces occur. In particular when drilling a borehole, the entire impact energy of the rotary impact drilling device must be absorbed by the central part of the hard metal insert. It is therefore the object of the present invention to modify a rotary impact twist drill so that these different loads on the hard metal cutting edges can be taken into account. The performance of the drilling tool should at least be maintained and very good removal of the drilling dust should be guaranteed.

These problems are solved by a rotary impact twist drill which has the features stated in the characterizing section of patent claim 1. According to the invention, the additional cutting edges protrude axially and / or radially from the peripheral areas of the cutting insert. Relative to the direction of rotation of the rotary impact twist drill the angle between the additional cutting edges and the subsequent insert is less than 90 °. Each additional cutting edge is preceded by a main task. Because the additional cutting edges protrude axially or radially or both axially and radially from the peripheral areas of the cutting insert, the additional cutting edges take over the function of main cutting edges and experience the greatest shear stress when a borehole is created. Since the actual material removal takes place on the additional cutting edges, the broad main removal grooves for the drilling dust, in relation to the direction of rotation of the drilling tool, are located upstream of the additional cutting edges. In this way, the removed material is conveyed directly into the main discharge paths. The arrangement of the cutting insert and the additional cutting edges in the form of an X, in which the additional cutting edges leading in relation to the direction of rotation of the drilling tool with the subsequent cutting insert form an acute angle of less than 90 °, allows the main procedures to be broadened. This ensures even better removal of the drilling dust. The cutting edges of the insert only fulfill the guiding function for the rotary impact twist drill and can be further optimized with regard to their task.

Since the cutting insert is only exposed to low shear forces due to its tasks reduced to guiding the drilling tool, the risk of loosening of the cutting insert, which is only encircled along its long sides, is also reduced. The additional cutting edges, which provide the main material removal, do not extend over the entire diameter of the shank and are therefore embedded in the drill shank with at least a large part of their axial circumference. As a result, the risk of locking is reduced with the additional cutting edges, despite the large shear forces acting on them.

For a further improvement in the removal of the drilling dust, it proves to be advantageous if additional removal grooves are provided which are arranged downstream of the additional cutting edges in relation to the direction of rotation of the rotary impact twist drill. The additional removal grooves are arranged in the narrowed area between the leading additional cutting edges and the cutting insert.

When removing material from the borehole wall by means of the additional cutting edges, the end of the shaft tends to yield laterally. For the concentricity of the drilling tool, it is advantageous if the radial projection of the insert is at least 50% of the radial projection of the additional cutting edges. In this way, the evasion of the End of the shaft only take place to a very limited extent and sufficient concentricity is guaranteed.

The guiding function of the peripheral areas of the cutting plate is further improved in that the end faces of the cutting plate, which are parallel to the shank axis, are curved, their curvature being matched to the curvature of the casing of the drill shank. When the areas of the cutting plate protruding beyond the shank jacket come into contact with the borehole wall, they only slide along the borehole wall due to the curved shape of their end faces and make practically no contribution to the abrasive material removal. This reduces the friction of the drilling tool in the borehole.

In order to adequately center the rotary impact twist drill during drilling and during the creation of a borehole, the central region of the cutting plate preferably projects above the peripheral regions and the additional cutting edges. The central area is preferably axially thickened. In this way, the very high impact load on the center area of the insert is taken into account, particularly when drilling.

In an advantageous variant of the invention, the cutting insert is divided into segments which are connected to one another via thin material webs. In this way, predetermined breaking points are created on the cutting insert, which prevent the cutting insert from breaking in an uncontrolled manner if it is subjected to excessive mechanical stress. Another advantage is that the segmented design of the cutting plate saves material, usually an expensive, special hard metal.

In particular in the case of large diameter rotary drilling twist drills, it is advantageous if the radial distance of the additional cutting edges from the raised central region of the segmented cutting insert is greater than the length of the material webs. In the case of a drilling tool designed in this way according to the pattern of a breakthrough drill, the frictional resistance when creating the borehole is reduced. The non-abrasive machined annular area of the base has very little stability and is simply shredded by the leading insert or the end face of the shaft.

It is advantageous if the insert is made of an impact-resistant material. In this way, the fact is taken into account that in particular the central region of the cutting plate is exposed to a high impact load due to the axial impacts transmitted from the rotary drilling device to the drilling tool. The additional cutting edges, which provide the main material removal, advantageously consist of a harder material than the cutting insert in this embodiment variant of the invention. In this way, the cutting edges are optimized according to their different loads.

In an embodiment of the invention which is advantageous for reasons of symmetrical loading, the additional cutting edges lie opposite one another on a diameter and are arranged at the same distance from the center of the end face.

For the effectiveness of the additional cutting edges, which provide the main material removal, these are preferably designed as hard metal plates bearing roof-shaped cutting edges.

Fig. 1

eine Stimansicht eines ersten Ausführungsbeispiels eines Drehschlag-Wendelbohrers gemäss der Erfindung;

Fig. 2

eine Seitenansicht eines weiteren Ausführungsbeispiels eines Drehschlag-Wendelbohrers gemäss der Erfindung;

Fig. 3

eine Stimansicht des Ausführungsbeispiels gemäss Fig. 2;

Fig. 4

eine Seitenansicht einer segmentierten Schneidplatte;

Fig. 5

eine Aufsicht der Schneidplatte gemäss Fig. 4; und

Fig. 6 und 7

zwei Seitenansichten einer Zusatzschneide

Further advantages result from the description of exemplary embodiments of the rotary impact twist drill according to the invention with reference to the schematic drawings. Show it:

Fig. 1

a front view of a first embodiment of a rotary impact twist drill according to the invention;

Fig. 2

a side view of another embodiment of a rotary impact twist drill according to the invention;

Fig. 3

a front view of the embodiment of FIG. 2;

Fig. 4

a side view of a segmented insert;

Fig. 5

a top view of the insert according to FIG. 4; and

6 and 7

two side views of an additional cutting edge

The embodiment of a rotary impact twist drill shown in top view in FIG. 1 comprises a shank 1 with two main extraction grooves 4, 5 for drilling dust. At its one shaft end 10, the shaft 1 is equipped with a cutting plate 6, which is fixed in a groove 9 that extends over the diameter of the shaft 1, for example by soldering. The cutting plate 6 has roughly roof-shaped hard metal cutting edges 7, which axially withdraw from a cutting tip 8 rising above the end face 3 to the outside of the jacket 2 of the shaft 1. In addition, additional cutting edges 11 are arranged in the end face, the longitudinal axis L of which includes an acute angle with the longitudinal extension of the cutting plate 6. In the illustrated embodiment, two additional cutting edges 11 are arranged diametrically opposite one another, their longitudinal axes L coinciding with a diameter of the shank 1. In this way, the cutting plate 6 and the additional cutting edges 11 essentially form the shape of an X. In the exemplary embodiment shown, the additional cutting edges 11 are arranged at the same distance from the center of the end face 3.

The additional cutting edges 11 have a radial projection r relative to the jacket 2 of the shaft 1, which is greater than the radial projection s of the cutting insert 6. The radial projection of the cutting insert is at least 50% of the radial projection of the additional cutting edges. In this way, the additional cutting edges 11 define the enveloping circle H, which is indicated by dashed lines in FIG. 1. In relation to the direction of rotation R of the rotary impact twist drill, each additional cutting edge 11 is preceded by one of the main extraction grooves 4, 5. Between the additional cutting edges 11 and the cutting plate 6 lagging in the direction of rotation R, secondary extraction grooves 14, 15 for drilling dust are arranged, which preferably open into the main extraction grooves 4, 5 along the shaft 1.

As indicated in Fig. 1, the axially parallel end faces 13 of the cutting plate 6 are curved. The curvature of the end faces 13 is matched to the curvature of the jacket 2 of the shaft 1 and is preferably part of a cylindrical surface. The axially parallel end faces 12 of the additional cutting edges 11 defining the enveloping circle H are preferably designed as cutting edges 22 in order to further increase their abrasive effect.

2 and 3 show a further exemplary embodiment of a rotary impact twist drill according to the invention. It comprises a shaft 1 with two main discharge grooves 4, 5 for drilling dust and is at its one shaft end 10 with a cutting plate 6 equipped, which is segmented. In particular, the cutting plate 6 is divided into a central cutting edge 17 and into peripheral segments 18 which are connected to one another via narrow material webs 19, as is shown in more detail in FIGS. 4 and 5. The central cutting edge 17 projects beyond the peripheral segments 18 and has a cross-sectional thickening 20 in its central region. The groove 9, which extends over the diameter of the shank 1, has a recess 16 in the central region of the end face 3, which is designed to accommodate the thickened central region 20 of the cutting plate 6. In this way, the cutting plate 6 is positively fixed in the groove 9.

The additional cutting edges 11 project beyond the peripheral segments 18 of the cutting plate both axially and radially. The distance between the additional cutting edges 11 and the raised area of the central cutting edge 17 is greater than the length of the thin material webs 19. Thus, the peripheral segments 18 only perform more guiding functions for the rotary impact twist drill. The actual cutting performance is taken over by the additional cutting edges 11 and, to a smaller extent, also by the central cutting edge 17. Since the cutting plate 6 and in particular the central cutting edge 17 in the segmented variant of the cutting plate shown for example are primarily exposed to axial loads from the axial blows on the tool, it is advantageous to produce the cutting plate 6 from an impact-resistant material. The additional cutting edges 11, which perform the actual mining performance and are subject to high abrasive forces, consist of a harder material than the cutting plate 6. In both cases, these are suitable hard metal alloys which are known per se from the prior art.

It can be seen from FIG. 5 that the lateral end faces 13 of the cutting plate 6, or, in the case of the segmented cutting plate shown for example, the lateral end faces 23 of the peripheral segments 18 are curved. For example, the end faces 23 are parts of a cylindrical surface, the curvature of which largely corresponds to the curvature of the jacket 2 of the shaft 1.

6 and 7, an embodiment of an additional cutting edge 11 is shown in two side views. 7 is a front view from the direction of the free end face 12 of the additional cutting edge 11 which is in engagement with the borehole wall. The additional cutting edge 11 has approximately roof-shaped cutting edges 24. Its free end face 12 is also designed as a cutting edge 22 to make it abrasive To increase the effectiveness in use. The foot part 25 of the additional cutting edge is, for example, rounded and is in this way even better adapted to the shape of the base of the receiving groove 26 in the shaft 1. The receiving grooves 26 for the additional cutting edges, as shown for example in FIGS. 1 and 3, are designed as separate grooves. In this way, the additional cutting edges 11 can be arranged independently of one another in their alignment with the cutting plate 6. However, it is also conceivable to arrange the additional cutting edges 11 in a single receiving groove 26 which extends over the diameter of the shaft 1 and to fix them there, for example by soldering.

In the rotary impact twist drill according to the invention, the additional cutting edges protrude axially or radially or both axially and radially from the peripheral regions of the cutting insert. The additional cutting edges thus take over the function of main cutting edges and experience the greatest shear stress when a borehole is created. Since the actual material removal takes place on the additional cutting edges, the broad main removal grooves for the drilling dust, in relation to the direction of rotation of the drilling tool, are located upstream of the additional cutting edges. In this way, the removed material is conveyed directly into the main discharge paths. The arrangement of the cutting insert and the additional cutting edges in the form of an X, in which the additional cutting edges leading with respect to the direction of rotation of the drilling tool with the subsequent cutting insert form an acute angle of less than 90 °, makes it possible to broaden the main procedures. This ensures even better removal of the drilling dust. The cutting edges of the insert only fulfill the guiding function for the rotary impact twist drill and can be further optimized with regard to their task.

Claims (10)

Rotary impact twist drill with a drill shank (1) which is equipped with at least one main output (4, 5) for drilling dust which runs spirally along its longitudinal extension and is equipped with a cutting plate (6) and additional cutting edges (11) at the shaft end (10) which is substantially X-shaped to each other arranged in the end face (3) at the end of the drill shank (1) and fixed and the end face (3) and the casing (2) of the drill shank (1) project axially and radially, characterized in that that the supplementary cutting edges (11) / project radially beyond the peripheral areas of the cutting plate (6) axially and or that, based on the direction of rotation (R) of the rotary impact-twist drill, the angle between the supplementary cutting edges (11) and the trailing cutting plate (6 ) is less than 90 ° and each additional cutting edge (11) is preceded by a main process (4, 5). Device according to claim 1, characterized in that additional removal grooves (14, 15) are provided for drilling dust, which are arranged downstream of the additional cutting edges (11) with respect to the direction of rotation (R) of the rotary impact twist drill. Device according to claim 1 or 2, characterized in that the radial projection (s) of the cutting plate (6) is at least 50% of the radial projection of the additional cutting edges (r). Device according to one of the preceding claims, characterized in that the end faces (13; 23) of the cutting plate (6) which are axially parallel to the shank axis are curved, their curvature being matched to the curvature of the casing (2) of the drill shank (1). Device according to one of the preceding claims, characterized in that the central region of the cutting plate (6) projects beyond the peripheral regions and the additional cutting edges (11) and preferably has an axial thickening (20). Device according to one of the preceding claims, characterized in that the cutting plate (6) is divided into segments (17, 18) which are connected to one another via thin material webs (19). Apparatus according to claims 5 and 6, characterized in that the radial distance of the additional cutting edges (11) from the raised central area (17) of the segmented cutting plate (6) is greater than the length of the material webs (19). Device according to one of the preceding claims, characterized in that the cutting plate (6) consists of an impact-resistant material and that the additional cutting edges (11) consist of a harder material than the cutting plate (6). Device according to one of the preceding claims, characterized in that the additional cutting edges (11) lie opposite one another on a diameter of the shaft (1) and are arranged at the same distance from the center of the end face (3). Device according to one of the preceding claims, characterized in that the additional cutting edges (11) are designed as hard metal plates bearing roof-shaped cutting edges (22, 24).

Images