EP0778390B1 - 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-A-39 19 264 a rotary impact twist drill is known which has a shaft has at least one lead in its coat, spiraling from the shaft end runs in the direction of the insertion end of the tool. Are at the end of the shaft Carbide cutting edges are provided, which are in front of the end face of the shaft end. The cutting edges are arranged on hard metal pins, which come from the end face of the Stick out. In particular, the known rotary impact twist drill at least one central hard metal pin and two on a diameter of Shanked opposing peripheral hard metal pins.

The peripheral carbide pins are set back from the central pin and are of the same type inserted into the end face of the shaft end that they are radial over their entire length protrude over the outer surface of the shaft. They have a polygonal one Cross-sectional profile and are used inclined to the axis of the shaft, that essentially only the cutting edges at their foremost free end with the Drill hole wall come into engagement. The above central carbide pin works like a centering element, however, this known rotary impact twist drill in Operation due to insufficient lateral guidance in the borehole. It can it may happen that the location hole is too large or the drilling tool even tilted in the location hole. By the opposite of the axis of the shaft inclined arrangement of the peripheral carbide pins do not act on all sides edged carbide pins have relatively high radial forces that lead to loosening and The peripheral hard metal pins can fall out.

In EP-A-0 226 537, which forms the generic generic term, is a rotary impact twist drill proposed the one over the entire diameter of the Has drill shaft extending carbide cutting plate, which in a continuous groove is inserted in the end face of the shaft. In addition to the Cutting plate are provided cutting pins that come from the end face of the shaft end Stick out of the shaft or from the jacket of the shaft. The free ends of the Cutting pins are in the spanned by the cutting edges of the hard metal plate Surface of revolution. The free ends of the shaft protruding from the jacket of the shaft When drilling, cutting pins come into contact with the wall of the borehole and roughen it during the drilling process. While in this known rotary impact twist drill there is already some guidance of the drilling tool in the hole the predominantly abrasive effect of the abutting against the borehole wall Cutting pins are given a certain stiffness, which is the achievable Mining capacity in the underground reduced.

The object of the present invention is therefore a rotary impact twist drill to improve in such a way that an optimal guidance of the drilling tool in the Location hole is guaranteed. A rotary impact twist drill is to be created be, which is easy to operate, has no tendency to tilt and one high mining performance allowed. The rotary impact twist drill according to the invention is intended moreover, be simple and inexpensive to manufacture.

These tasks are solved by a rotary impact twist drill, which the in characterizing section of claim 1 has features. According to the invention, at least one pin-shaped is in the area of the shaft end Guide element embedded in the shaft, its longitudinal axis essentially runs perpendicular to the longitudinal axis of the shaft. The free end face of the pen-shaped Guide element has a protrusion compared to the sheath of the shaft, the is smaller than the radial projection of the insert with the hard metal cutting edges. By providing at least one pin-shaped guide element on the drilling tool, the projection of which is smaller than the radial one compared to the jacket of the shaft The protrusion of the insert will be an excellent guide for the drilling tool achieved in the borehole without the disadvantage of a certain stiffness as a result of having to put up with an abrasive effect. This makes the prerequisites for given a high drilling performance. The pin-shaped guide element does not accept Part of the dismantling process, it has only management functions. This can do that Guide element without having to consider a cutting edge geometry, be very robust. By placing the pin-shaped guide element over its is embedded in the entire circumference, there is an optimal hold in the shaft. The essentially perpendicular alignment of its longitudinal axis to the axis of the shaft facilitates the manufacture of the rotary impact twist drill according to the invention. In the Preparation of the shaft only needs to be one that is perpendicular to the axis of the shaft Adequate depth must be drilled into which the pin-shaped Guide element is used.

In an advantageous embodiment variant, two or more are pin-shaped Guide elements are provided, each in pairs in diagonally opposite Quadrants of a cross section are arranged perpendicular to the axis of the shaft. The arranged in pairs for reasons of symmetry. This way sufficient scope for the arrangement of the extraction grooves for the drilling dust. In the case a carbide cutting insert, which fits into a groove in the end face of the Shaft end is used, can be in the space between the pin-shaped Guiding elements and the cutting plate a Abfuhmut be provided. By The arrangement of the pin-shaped guide elements can be varied standing space can be varied, so that wider Hauptffuhmuten are provided can, which are upstream of the main cutting edges on the cutting plate. in the Area between a pin-shaped guide element and that in the direction of rotation the subsequent part of the cutting plate can also have a narrower performance be provided.

For reasons of symmetry and for reasons of optimized concentricity of the rotary impact twist drill the pin-shaped guide elements are advantageously diagonal to one another arranged opposite one another, their longitudinal axes lying on one diameter. The angle at which the pin-shaped guide elements are radial protruding insert on the circumference of the jacket are offset, depending on Needs vary. An acute angle is advantageously chosen such that one wide main output in the direction of rotation of the drilling tool of a main cutting edge is upstream.

To ensure safe embedding in the shank of the drilling tool the pin-shaped guide elements preferably at a distance from the end face of the stem embedded in the sheath, which is about 1/4 to about 3/4 of the embedded Length of the carbide cutting edges is. The distance relates to the location of the Longitudinal axes of the guide elements. In this way, the Drilling tool in the exact area due to the cutting attack the hard metal cutting on the borehole wall the greatest stress is subject. The guide pins can be equidistant from the end face of the shaft or embedded at different intervals in the shaft.

In order to achieve the best possible dimensional accuracy of the borehole created, it is from Advantage if the pin-shaped guide elements compared to the jacket Have a projection that is at least half the radial projection of the Carbide cutting corresponds. In the case of pebble hits, this tends to be the insert to avoid supporting end of the shaft to the side. The pen-shaped ones work Management elements counter. The extent of the protrusion of the pen-shaped Guide elements thus defines the maximum distance that the free front end of the Dodge shaft. In this way, the greatest possible concentricity guaranteed without the pin-shaped guide elements permanently engaging with the borehole wall.

By the outstanding free end face of the pin-shaped from the jacket of the shaft Guide elements is at least partially curved, the abrasive Effect of the guide elements in contact with the borehole wall clearly reduced. The free end face preferably has that at least in regions Curvature of a spherical surface or a cylindrical surface, the curvature is matched to that of the sheath of the shaft.

Particularly advantageous for the manufacture of the rotary impact twist drill according to the invention it is when the pin-shaped guide elements are circular Have cross-section. The mounting holes in the shaft can be very easily with circular cross section can be created. When inserting the pen-shaped Guiding elements are particularly important in the case of design variants end faces curved in the shape of a spherical surface did not pay attention to the axial orientation become. With a symmetrical formation of the end faces of the pin-shaped Guide elements do not have to be aligned with the orientation of the Guide elements are respected. That way it doesn't matter if the Guide pins with one or the other of their two end faces ahead be used. This makes it easier to assemble the pen-shaped Guide elements in the shaft of the rotary impact twist drill.

To ensure in a simple manner that the pin-shaped guide elements a have defined projection over the sheath of the shaft, it is advantageous Provide a depth stop on the guide elements as an assembly aid. This can for example by one or more on the jacket of the guide elements arranged guide pins can be realized. In a departure from the symmetrical Formation of the end faces, the pin-shaped guide elements can be pointed have an enlarged head that bears against the jacket of the shaft during assembly and towering over it to the extent desired. By attaching depth stops on the pin-shaped guide elements must be essentially vertical to the axis of the shaft-running receiving bores not exactly in terms of their depth to be controlled. Only a minimum depth has to be guaranteed. The supernatant of the The end face of the pin-shaped guide elements is defined by the depth stop.

In an advantageous embodiment variant, the guide elements are in one through groove embedded in the shaft end, which extends over a diameter of the Shaft extends. This further facilitates the manufacture of the tool. It there is no need to drill holes with a more or less precisely defined depth. For the inclusion of the guide elements is in addition to the groove for the Insert another groove milled into the shaft end, which in the desired Angle to the receiving groove for the insert is inclined. This groove can be is a continuous groove, but grooves can also be milled in do not lie on a common diameter. The fixation of the guide elements in the groove can be done, for example, by soldering.

It proves to be advantageous for the stability of the guide elements fixed in the shaft, if this is embedded in the shaft to about 3/5 to about 3/4 of its longitudinal extent are.

Fig. 1

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

Fig. 2

eine teilweise geschnittene Stimansicht des Ausführungsbeispiels gemäss Fig. 1;

Fig. 3 und 4

zwei Ausführungsbeispiele von stiftförmigen Führungselementen;

Fig. 5

eine Seitenansicht eines weiteren Ausführungsbeispiels eines erfindungsgemässen Drehschlag-Wendelbohrers; und

Fig. 6

eine Stirnansicht des Ausführungsbeispiels gemäss Fig. 5

Further advantages of the invention result from the description of exemplary embodiments with reference to the schematic representations. Show it:

Fig. 1

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

Fig. 2

a partially sectioned end view of the embodiment of FIG. 1;

3 and 4

two embodiments of pin-shaped guide elements;

Fig. 5

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

Fig. 6

5 shows an end view of the exemplary embodiment according to FIG. 5

The embodiment shown in FIGS. 1 and 2 of the inventive Rotary impact twist drill comprises a shaft 1 which is provided with two main discharge grooves 4, 5 is equipped for cuttings that run in a spiral shape in its casing 2. At the Stimulating 3 of the shaft 1, a cutting plate 6 is arranged, which with Carbide cutting 7 is equipped. The preferably roof-shaped Tungsten carbide blades 7 extend axially recessed from a blade tip 8 outside to the jacket 2 of the shank 1. The insert is 6 in a groove 9 in the front end 3 of the shaft 1 fixed, which extends over its diameter. For example the cutting plate 6 fixed by soldering in the groove 9.

In the area of the shaft end 10 are two pin-shaped guide elements 11 in the Embedded shaft 1, the free end face 12 of the jacket 2 of the shaft 1 overtop. The radial projection r of the guide elements 11 is smaller than the radial one Projection s of the cutting plate 6 and corresponds to at least half the radial Overhang s of the insert 6. This ensures that the Guide elements 11 do not participate in the dismantling process, but merely Perform the guiding function for the rotary impact twist drill. The guide elements 11 are embedded in the shaft 1 such that their longitudinal axes L essentially run perpendicular to the longitudinal axis A of the shaft 1.

As shown in FIG. 2, the rotary impact twist drill can have two guide elements 11 exhibit. However, only a single guide element 11 can also be provided, as indicated in the side view of the rotary impact twist drill in Fig. 1. at the arrangement of more than one guide element 11 in the shaft end 10, as shown in Fig. 2, preferably in pairs in diagonally opposite Quadrants of a cross section perpendicular to the longitudinal axis A of the shaft 1 intended. As shown, the longitudinal axes L of the guide elements 11 are arranged on a diameter of the shaft 1. However, this arrangement is not absolutely necessary. The guide elements 11 can also be in the shaft end 10 in this way be embedded that their longitudinal axes in the cross-sectional plane of the shaft 1 straight lines deviating from a diameter, which are parallel or inclined to can run a diameter. The advantageously close Longitudinal axes L of the guide elements 11 with the cutting plate 6 an acute angle on. In this way, the hard metal blades 7 in the direction of rotation leading Hauptffuhmuten 4.5 wider.

The guide elements 11 are embedded in the shaft 1 such that their longitudinal axis has a distance from the front end 3 of the shaft 1 which is approximately 1/4 to is about 3/4 of the embedded length of the cutting plate 6. As can be seen from Fig. 2, are the guide elements 11 over about 3/5 to about 3/4 of their longitudinal extent l in the Shaft 1 embedded.

3 and 4 show two exemplary embodiments for guide elements 11. In both In some cases, the guide elements 11 have a circular cross section. This is but not absolutely necessary, the guide elements 11 can also be one have polygonal cross-section, for example be hexagonal or octagonal.

The guide element 11 shown in Fig. 3 has two identically designed End faces 12 to enable the guide element to also be rotated through 180 ° can be embedded in the shaft 1. The end face 12 of the in FIGS. 1 and 3 shown guide element 11 is in its curvature to the curvature of the jacket 2 of the shaft 1 adjusted. In particular, the end face 12 initially has one annular portion 14 of a spherical surface on the cylindrical part 13 of the Connects guide element 11. The radius of curvature corresponds to the spherical surface essentially the radius of curvature of the jacket 2 at the shaft end 10. The of the central area 15 of the end face 12 which is enclosed in the annular area 14 for example the curvature of a cylindrical surface; but he could also be trained.

The guide element 21 shown in Fig. 4 is with a depth stop as Installation aid equipped. According to the illustrated embodiment, the Depth stop formed by an annular shoulder 24, which on the cylindrical Section 23 of the guide element connects. The free end face 12 of the Guide element 21 is provided on a mushroom-shaped head 22, which the cylindrical region 23 of the guide element 21 protrudes. The radius of curvature of the Free end face 12 is the radius of curvature of the jacket 2 at the shaft end 10 equalized. The end face 12 can consist of different surface sections be composed, as explained using the exemplary embodiment in FIG. 3. The Free end face 12 of the guide element 21 can, however, as shown in FIG. 4, be formed by a spherical surface section with a suitable radius of curvature.

In the embodiment shown in FIGS. 1 and 2, the guide elements 11 inserted in bores vertically to the shaft axis A and over their entire circumference in embedded the shaft 1. 4 and 5 is an alternative embodiment of the Shown rotary twist drill according to the invention, in which the Guide elements 31 are embedded in a groove 16 in the front end 3 of the shaft. The The guide elements 31 are fixed in the groove 16 which is open at the end 3 for example by soldering. The additional groove 16 can, as shown, as continuous groove can be formed, which extends over a diameter D of the shaft 1st extends and preferably at an acute angle with respect to the receiving groove 9 is inclined for the cutting plate 6. As alternatives, however, can also be used for any Guide element separate grooves may be provided on a not with a Diameter D are coinciding lines, which are parallel or inclined runs a diameter D and opens only at one point of the jacket 2. The depth the additional groove (s) 16 is dimensioned such that the longitudinal axes L of the Guide elements 31 have a distance from the end face 3 of the shaft 1 which is about 1/4 to about 3/4 of the embedded length of the cutting plate 6.

By at least one pin-shaped on the rotary impact twist drill according to the invention Guide element is provided, whose protrusion relative to the jacket of the Shank is smaller than the radial protrusion of the insert, becomes a excellent guidance of the drilling tool achieved in the borehole without the disadvantage a certain stiffness due to an abrasive effect have to. This creates the prerequisites for high drilling performance. The pin-shaped guide element does not participate in the dismantling process, it has only Leadership functions and can therefore, regardless of a cutting geometry have to be trained to be very robust. By making the pen-shaped Guide element over a substantial part of its longitudinal extent in the shaft is embedded, there is an optimal hold in the shaft. The essentially vertical Alignment of its longitudinal axis to the axis of the shaft facilitates the manufacture of the inventive rotary impact twist drill.

Claims (10)

1. Rotary percussive twist drill, comprising a shaft (1) with at least one main drilling waste removal groove (4, 5) which preferably extends spirally in its casing and at its one shaft end (10) a cutting plate (6) with hard-metal cutters (7) which protrude axially over the end surface (3) of the shaft end (10) and radially over the casing (2) of the shaft (1), and in the area of the shaft end (10) is embedded into the shaft (1), which comprises a free end surface (12), at least one pinshaped guiding element (11; 21; 31) the longitudinal axis (L) of which extends substantially perpendicularly to the longitudinal axis (A) of the shaft (1), characterised in that the end surface (12) has a radial protrusion (r) relative to the casing (2) of the shaft (1), which is smaller than the radial protrusion (s) of the cutting plate (6).
2. Device according to Claim 1, characterised in that more than one pinshaped guiding element (11; 21; 31) is provided, and the guiding elements (11; 21; 31) are arranged respectively in pairs in diagonally opposing quadrants of a cross-section perpendicularly to the axis (A) of the shaft (1).
3. Device according to Claim 1 or 2, characterised in that the pinshaped guiding elements (11; 21; 31) are arranged in pairs diagonally opposite each other, and their longitudinal axes (L) preferably lie on a diameter of the shaft (1).
4. Device according to one of the above claims, characterised in that the pinshaped guiding elements (11; 21; 31) are embedded into the shaft (1) in such a manner that the distance of the longitudinal axis (L) from the end surface (3) of the shaft (1) equals between approximately ¼ and approximately ¾ of an embedded length of the cutting plate (6).
5. Device according to one of the above claims, characterised in that the radial protrusion (r) of the pinshaped guiding elements (11; 21; 31) relative to the casing (2) of the shaft (1) equals at least half the radial protrusion (s) of the cutting plate (6).
6. Device according to one of the above claims, characterised in that the free end surfaces (12) of the pinshaped guiding elements (11; 21; 31) are designed to be at least partially bent and preferably a part of a spherical surface or a cylindrical surface, and the curvature is matched to that of the casing (2) of the shaft (1).
7. Device according to one of the above claims, characterised in that the guiding elements (11; 21; 31) have a circular cross-section and symmetrically designed end surfaces (12).
8. Device according to one of Claims 1 - 6, characterised in that the pinshaped guiding elements (21) have a depth stop as assembly aid, preferably a mushroomshaped expanded head (22) which projects over the casing (2) of the shaft (1).
9. Device according to one of the above claims, characterised in that the pinshaped guiding elements (11; 21; 31) are arranged in additional grooves (16) in the shaft end (10), which are preferably on a diameter (D) of the shaft (1).
10. Device according to one of the above claims, characterised in that between 3/5 and 3/4 of the longitudinal extent of the pinshaped guiding elements (11, 21, 31) are embedded into the shaft (1).

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