EP0778391B1 - Rotary percussive twist drill - Google Patents

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 conjunction with axial impact assisted Rotary drilling rigs are used. In particular, it concerns in usually around rock or masonry drills that are used for the rotary impact creation of holes or breakthroughs in concrete or masonry can be used. From the DE-C-30 20 284 a twist drill for drilling work in solid rock is known, the a drill shaft with two spirals running on the shaft for the Has drilling dust. Tungsten carbide cutting edges are provided at the shaft end Chisel and abrasively process the subsurface to create a drill hole. The Tungsten carbide blades are arranged in a cross shape in the end face of the shaft end protrude axially beyond the end face. In particular, the hard metal cutting edges on the one hand, on a continuous, over the diameter of the population extending hard metal plate, and provided on additional hard metal elements, the along a diameter of the shaft standing at 90 ° to the hard metal plate are arranged. Between the main cutting edges arranged on the hard metal plate and the additional cutting edges are each essentially axially parallel to the shaft extending grooves provided, which open into the Abfuhmuten on the shaft. These serve the removal of the resulting from the abrasive processing of the surface Drill dust. The main and additional cutting edges also have a radial projection opposite the jacket of the shank to prevent jamming of the drilling tool in the To prevent drilling. This well-known twist drill allows a moderate Drilling performance with reasonable wear of the carbide cutting edges.

From EP-B-0 452 255 a rotary impact twist drill is known, one along of a diameter of the shank and arranged carbide pins formed additional cutting edges, each having an axial and a radial Have protrusion over the shaft. They are on the carbide insert Main cutting of the drilling tool provided. The additional cutting edges are opposite axially reset the main cutting edges and essentially only meet Management functions for the drilling tool. With this improved rotary impact twist drill are the main and additional cutting edges in one that deviates from 90 ° Angle to each other. In particular, the arrangement is selected such that in relation to the direction of rotation of the drilling tool that leading the cutting insert Additional cutting edge with this includes an angle that is greater than 90 °, while the the additional cutting edge following the insert with it an acute angle includes. This embodiment has the advantage that the area which the respective main cutting edge is upstream, expanded and the mouth of a widened main courage allowed. In the narrower area, to the trailing one Additional cutting edge, a narrow additional handling is provided. At this "X-like" arrangement of the insert and the secondary cutting edges is due to the Cutting plate upstream widened Hauptfahmuten an improved Drill dust removal and adequate guidance is ensured via the additional cutting edges.

However, there is still a desire to improve the drilling performance of the rotary impact twist drill continue to improve. In particular, the prerequisite should be created to Cutting insert and the additional cutting edges with regard to their specific stress to be able to optimize. It should be noted that the central part of the Carbide cutting insert by the axial blows of the rotary impact drill others Is subjected to loads as the peripheral areas of the insert or the Additional cutting edges, which primarily cause shear forces. Especially when Drilling a borehole must have the entire impact energy of the rotary impact drill be taken up by the central part of the hard metal insert. The object of the present invention is therefore a rotary impact twist drill to be modified in such a way that these different loads of Carbide cutting can be taken into account. The performance should of the drilling tool at least remain and a very good removal of the Bohrmehls be guaranteed.

DE 4306981 A discloses a rotary impact twist drill with a drill shank that with at least one spiraling along its length Main discharge groove is equipped for drilling dust and at the shaft end with a cutting plate and is equipped with additional cutting edges that are substantially X-shaped to each other in the End face at the end of the drill shaft are arranged and fixed and the end face and protrude axially or radially from the casing of the drill shaft, the additional cutting edges project peripheral regions of the cutting plate axially and / or radially, with reference to the direction of rotation of the rotary impact twist drill the angle between the additional cutting edges and the trailing insert is smaller than 90 ° and each additional cutting edge is one Main discharge groove is upstream.

These tasks are solved by a rotary impact twist drill, which is the features stated in the characterizing section of claim 1. According to the invention, the additional cutting edges project beyond the peripheral areas of the Cutting plate axially and / or radially. Relative to the direction of rotation of the rotary impact twist drill is the angle between the additional cutting edges and the subsequent one Cutting plate less than 90 °. Each additional cutting edge is one of the main tasks upstream. By the additional cutting axially the peripheral areas of the cutting insert or protrude radially or both axially and radially, take over Additional cutting the function of main cutting and experience when creating one Borehole the greatest shear stress. Since the actual material removal to the If additional cutting is carried out, the broad main delivery paths for the drilling dust are covered in front of the direction of rotation of the drilling tool, the additional cutting edges. To this The removed material is conveyed directly into the main discharge paths. The Arrangement of the insert and the additional cutting edges in the shape of an X, in which the additional cutting edges leading in relation to the direction of rotation of the drilling tool form an acute angle of less than 90 ° with the following insert, allows to broaden the main process. This way is an even better one Removal of drilling dust guaranteed. The cutting edges of the insert only fulfill Management function for the rotary impact twist drill and can with regard to their Task can be further optimized. For a further improvement in the removal of the drilling dust, it proves to be advantageous if additional removal paths are provided which are related to the direction of rotation of the Rotary impact twist drill are located downstream of the additional cutting edges. The Additional execution paths are in the narrowed area between the preceding ones Additional cutting and the insert arranged.

Because the insert was reduced to the guidance of the drilling tool as a result of it Tasks exposed to low shear forces are also at risk Lockems of the insert, which is only framed along its long sides, is reduced. The Additional cutting edges that remove the main material do not extend over the entire diameter of the shaft and are therefore at least with a large part their axial circumference embedded in the drill shaft. As a result, the Additional cutting, despite the large shear forces acting on them, poses the risk of Lockems reduced.

This tends to result in material being removed from the borehole wall by the additional cutting edges End of the shaft for lateral evasion. It is for the concentricity of the drilling tool of advantage if the radial projection of the insert is at least 50% of the radial Protrusion of the additional cutting edges. In this way, the evasion of the Shaft end only to a very limited extent and it is a sufficient concentricity guaranteed.

The guiding function of the peripheral areas of the cutting plate is thereby further improved that the end faces of the Cutting plate are curved, their curvature of the curvature of the Jacket of the drill shaft is aligned. If the over the shaft coat protruding areas of the insert in contact with the borehole wall come, because of the curved shape of their end faces they only slide on the Along the borehole wall and make practically no contribution to the abrasive Material removal. This reduces the friction of the drilling tool in the borehole.

Around the rotary impact twist drill when drilling and while creating one To center the borehole sufficiently extends beyond the center area of the insert preferably the peripheral areas and the additional cutting edges. Here is the Center area preferably axially thickened. That way it becomes very high impact load on the center area of the insert, especially when Tapping into account.

In an advantageous variant of the invention, the cutting insert is divided into segments, which are connected to each other via thin material webs. That way, be on The insert creates predetermined breaking points that prevent the insert breaks uncontrollably if it is subjected to excessive mechanical stress. Another advantage is that the segmented design of the Insert material, usually an expensive, special hard metal, can be saved can.

In the case of large diameter rotary drilling twist drills in particular, it is advantageous if the radial distance of the additional cutting edges from the raised central area of the segmented cutting insert is greater than the length of the material webs. At a Such is designed according to the pattern of a breakthrough drill Frictional resistance when drilling the hole The non-abrasive machined annular area of the subsurface has a very low stability and is simply through the leading insert or the face of the shaft crushed.

It is advantageous if the insert is made of an impact-resistant material. On this takes into account the fact that in particular the Center area of the insert a high impact load from the Rotary drill is subjected to axial impacts transmitted to the drilling tool. The Additional cutting edges, which provide the main material removal, exist at this embodiment of the invention advantageously made of a harder material than that Cutting board. In this way, the cutting edges are different according to their Stress optimized.

In an advantageous for reasons of symmetrical loading Embodiment of the invention, the additional cutting edges lie on one another Diameter opposite and are the same distance from the center of the end face arranged.

For the effectiveness of the main material removal Additional cutting edges are preferably load-bearing as edge-shaped cutting edges Tungsten carbide plate formed.

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 supervision in FIG. 1 comprises a shaft 1 with two main discharge grooves 4, 5 for drilling dust. On its one shaft end 10, the shaft 1 is equipped with a cutting plate 6 which in a groove 9 extending over the diameter of the shaft 1, for example by soldering. The cutting plate 6 has an approximately roof-shaped design Tungsten carbide blades 7, which rise from a surface 3 above Knife tip 8 withdraw axially outwards to the jacket 2 of the shaft 1. In addition, additional cutting edges 11 are arranged in the end face, the longitudinal axis L includes an acute angle with the longitudinal extent of the cutting plate 6. in the illustrated embodiment, two additional cutting edges 11 are diametrically opposed to each other arranged opposite, their longitudinal axes L with a diameter of Shank 1 collapse. In this way, the cutting plate 6 and the Additional cutting 11 essentially the shape of an X. In the illustrated Embodiment are the additional cutting edges 11 at the same distance from the center of the End face 3 arranged.

The additional cutting edges 11 have one in relation to the jacket 2 of the shaft 1 radial projection r, which is greater than the radial projection s of the cutting plate 6. The radial projection of the insert is at least 50% of the radial one Overhang of the additional cutting edges. In this way, the additional cutting edges 11 Envelope circle H fixed, which is indicated by dashed lines in Fig. 1. Based on the direction of rotation R of the rotary impact twist drill, each additional cutting edge 11 is one of the main discharge paths 4, 5 upstream. Between the additional cutting edges 11 and R in the direction of rotation trailing cutting plate 6, secondary removal grooves 14, 15 are arranged for drilling dust, which preferably open into the main discharge grooves 4, 5 along the shaft 1.

As indicated in Fig. 1, the axially parallel end faces 13 are the Cutting plate 6 is curved. The curvature of the end faces 13 is the Curvature of the jacket 2 of the shaft 1 adjusted and preferably part of a Cylindrical surface. The axially parallel end faces 12 of the. Envelope circle H fixing additional cutting edges 11 are preferably designed as cutting edges 22 to increase their abrasive effect.

2 and 3 show a further embodiment of an inventive Rotary percussion drill spiral. 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 in a central cutting edge 17 and divided into peripheral segments 18 which are narrow Material webs 19 are connected to one another, as shown in FIGS. 4 and 5. The central cutting edge 17 projects beyond the peripheral segments 18 and points in its Center area a cross-sectional thickening 20. Which is about the diameter of the shaft 1 extending groove 9 has a in the central region of the end face 3 Recess 16 on which to accommodate the thickened center region 20 of the Cutting plate 6 is formed. In this way, the cutting plate 6 is positively in the groove 9 fixed.

The additional cutting edges 11 protrude beyond the peripheral segments 18 of the cutting insert both axially and radially. The distance of the additional cutting edges 11 from the raised one The 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 management functions for the Rotary percussion flute drill bit. The actual cutting performance is from the additional cutting edges 11 and to a smaller extent also taken over by the central cutting edge 17. Since the Cutting plate 6 and in particular the central cutting edge 17 in the example shown segmented variant of the insert primarily axial Axial impact on the tool, it is from Advantage to produce the cutting plate 6 from an impact-resistant material. The Additional blades 11, which perform the actual mining performance and high subject to abrasive forces are made of a harder material than that Cutting plate 6. In both cases, these are suitable hard metal alloys, which are known per se from the prior art.

From Fig. 5 it can be seen that the lateral end faces 13 of the cutting plate 6, or, in In the case of the segmented cutting insert shown, for example, the lateral ones End faces 23 of the peripheral segments 18 are curved. For example are the end faces 23 parts of a cylindrical surface, the curvature of the curvature of the Shell 2 of the shaft 1 largely corresponds.

6 and 7 is an embodiment of an additional cutting edge 11 in two Side views shown. 7 is a front view from the direction of the Use with the borehole wall engaging free end face 12 of the Additional cutting edge 11. The additional cutting edge 11 has approximately roof-shaped cutting edges 24 on. Its free end face 12 is also designed as a cutting edge 22 to make it abrasive To increase the effect in use. The foot part 25 of the additional cutting edge is for example, rounded and is even better in shape the bottom of the receiving groove 26 in the shaft 1 adjusted. The receiving grooves 26 for the additional cutting edges are, as shown in FIGS. 1 and 3, for example, as separate Grooves formed. In this way, the additional cutting edges 11 can be used independently from each other in their orientation to the cutting plate 6 are arranged. But it is also conceivable, the additional cutting edges 11 in a single, over the diameter of the Arrange shaft 1 extending receiving groove 26 and there for example by Fix in place.

In the rotary impact twist drill according to the invention, the additional cutting edges protrude the peripheral areas of the cutting plate axially or radially or both axially and radial. The additional cutting edges thus take over the function of main cutting edges and experience the greatest shear stress when drilling a hole. Since the actual material removal on the additional cutting edges are the broad ones Main procedure for drilling dust, related to the direction of rotation of the Drilling tool, the additional cutting edges. That way it will removed material is conveyed directly into the main discharge path. The arrangement of the Cutting insert and the additional cutting edges in the form of an X, in which the covered additional cutting edges leading in the direction of rotation of the drilling tool with the subsequent cutting insert an acute angle less than 90 ° allowed it to spread the main business. This way an even better discharge of the drilling dust guaranteed. The cutting edges of the insert only fulfill Management function for the rotary impact twist drill and can with regard to their Task can be further optimized.

Claims (9)

1. Rotary twist-drill with a drill-bit shaft that is provided with at least one, spiral main removal groove (4, 5), for boring dust and cuttings, running along its longitudinal extent, and that is provided, at the end of the shaft (10) with a cutting plate (6) and with supplementary cutting edges (11) that are disposed and fixed essentially in an X-form, in relation to each other, on the face (3) at the end of the drill-bit shaft (1) and that project axially or radially from the end face (3) and the surface (2) of the drill-bit shaft (1), whereby the supplementary cutting edges (11) project axially and radially beyond the peripheral areas of the cutting plate (6), and, in relation to the direction of rotation (R) of the rotary twist-drill, the angle between the supplementary cutting edges (11) and the cutting plate (6) that follows it is less than 90° and each supplementary cutting edge (11) is placed before a main removal groove (4, 5),
   characterized in that supplementary removal grooves (14, 15) are provided for boring dust and cuttings, the said supplementary removal grooves (14, 15) being positioned, in relation to the direction of rotation (R) of the rotary twist-drill, after the supplementary cutting edges (11) and opening into the main removal grooves (4, 5) along the shaft (1).
2. Device in accordance with claim 1, characterized in that the radial projection of the cutting plate (6) is at least 50% of the radial projection of the supplementary cutting edge (r).
3. Device in accordance with claim 1 or 2, characterized in that the end faces (13; 23), of the cutting plate (6), running parallel to the axis of the shaft, are developed arched whereby their curvature is adapted to the curvature of the surface (2) of the drill-bit shaft (1).
4. Device in accordance with one of the preceding claims, characterized in that the central area of the cutting plate (6) projects out beyond the peripheral areas and the supplementary cutting edges (11), and preferably has an axial thickening (20).
5. Device in accordance with one of the preceding claims, characterized in that the cutting plate (6) is divided up into sectors (17, 18) that are connected to each other by means of thin webs (19).
6. Device in accordance with claims 4 and 5, characterized in that the radial separation of the supplementary cutting edges (11) from the raised, central area (17) of the sectioned cutting plate (6) is larger than the length of the webs (19).
7. Device in accordance with one of the preceding claims, characterized in that the cutting plate (6) is made of a material that yields in response to blows, and that the supplementary cutting edges (11) are made of harder material than the cutting plate (6).
8. Device in accordance with one of the preceding claims, characterized in that the supplementary cutting plates (11) lie opposite each other on either side of the diameter of the shaft (1) and are disposed with the same separation from the centre of the end face (3).
9. Device in accordance with one of the preceding claims, characterized in that the supplementary cutting edges (11) are developed as small, hard, metal plates carrying ridge-form cutting edges (22, 24).

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