EP0739673A1 - Tube for hole saw - Google Patents

Abstract

The inner and/or outer peripheral surfaces (2,3) of the drill bit tube (1) incorporate a structure (4-7,9,10) providing stiffening in the axial direction, without increasing material thickness. The structure can be formed by embossed protrusions (9) and/or recesses (10) formed in one of the surfaces. These can consist of grooves running for the full length of the bit, and which can be closed. The structure can extend over the entire cross-section of the tubular bit. Alternatively it can be formed by curved wall segments. The bit can be of polygonal cross-section, or can have corrugations running in the peripheral, direction.

Description

The invention relates to a drill bit tube according to the preamble of claim 1.

Pipes for core bits, in particular for diamond core bits, are generally made from soft structural steel in the form of drawn precision tubes. These pipes are usually painted, in some cases also chromated. They have a uniformly round cross-section from the drill bit to the lid area. In the case of small drill bits, typically with pipe diameters that are smaller than 40 mm, thickenings with milled grooves are sometimes provided at the cutting end. These thickenings are necessary so that the drill segments can be attached with sufficient strength. The grooves in the thickened areas serve to absorb the drilling dust generated during drilling.

Furthermore, drill bits for dry drilling have become known which have mutually opposite bores which serve to remove the core located inside the drill bit after drilling. Longitudinal slots up to the lid are sometimes also provided. In turn, drilling dust is taken up in these longitudinal slots during drilling. They also serve, like the round holes mentioned, to remove the drill core located in the drill bit. These longitudinal slots were only so-called for the dimension Can countersink (maximum drilling depth 70 mm) practicable. Wet drill bits, on the other hand, cannot have any breakthroughs, since otherwise there is a bypass in the flow of the flushing agent, which flows over the cover of the drill bit along the inside, past the drilling segments, to the outside.

For the improvement of the drilling dust transport pipes have also become known, on the outer circumference of which a helix with a small pitch is attached, which is usually screwed in. For such coils, the material thickness must be increased in order to ensure sufficient pipe rigidity. This results in a larger cutting width, which consequently requires a higher drive power when drilling.

All of the above-mentioned embodiments, which differ from the pure cylindrical shape of the drill bit tube, result in a weakening of the axial rigidity of the drill bit tube. Accordingly, a lot of material must be used in the manufacture of such drill bit tubes. The pure cylindrical shape of a drill bit tube has good axial guiding properties, but it causes enormous friction due to the large area of the side walls coming into contact with the drill walls. On the one hand, the heat generated must be absorbed by the drill bit, on the other hand, correspondingly powerful machines are required to drive the drill bit.

DE 42 42 910 discloses a drill bit which has reinforcing ribs in the form of material reinforcements in order to improve the rigidity in the axial direction. The attachment of such material reinforcements represents a significant additional effort in production.

The object of the invention is therefore to propose a tube for a drill bit, in which the friction during Drilling is reduced and at the same time the axial rigidity is improved, the drill bit being able to be produced at the same time with little effort, in particular by shaping processes.

This object is achieved on the basis of a drill bit of the type mentioned in the introduction by the characterizing features of claim 1.

Advantageous designs and developments of the invention are possible through the measures mentioned in the subclaims.

Accordingly, a drill bit tube according to the invention has a structure on at least one lateral surface which stiffens the tube in the axial direction without additional material reinforcement. The structure of such a structure has a large axis-parallel component in order to bring about this stiffening in the axial direction. Due to the structuring of the lateral surface, a closed cylindrical lateral surface no longer comes into contact with the wall of the borehole or the drill core. As a result, in addition to the improved rigidity of the drill bit tube, a reduced friction during drilling is achieved.

The advantages according to the invention are achieved solely by the shape and not by additional material reinforcements. The wall thickness of the drill bit tube remains essentially unchanged due to the structures. Structures of this type can be produced using shaping processes with relatively little effort, for example from flat material or from smooth cylinder tubes.

The lateral surface structure is preferably applied in the form of impressions or indentations in the lateral surface. Such impressions (or indentations) can be stamped into the tube sheet by means of a so-called roll rolling embossing before the sheet is formed into the drill bit tube and welded along the longitudinal seam. However, embossing into continuously drawn cylindrical tubes would also be conceivable.

The impressions can be made in the form of grooves over the entire length of the tube and / or as self-contained impressions. Grooved impressions can take a straight course parallel to the axis or a curved or angular course. The self-contained impressions can be circular, elliptical and polygonal.

For an axial stiffening effect, it is beneficial in any case if the directional component of the embossing is emphasized more in the axial direction than the component parallel to the pipe circumference. It is therefore advisable to keep the deviations from the axis-parallel course as small as possible for groove-shaped impressions.

In the case of self-contained impressions, circular or elliptical impressions, the semi-axis of which in turn deviates only slightly or not at all from the direction parallel to the axis, are advantageous. Accordingly, diamond-shaped impressions are preferred from the angular impressions, the diagonal of which in turn deviates only slightly or not at all from the alignment parallel to the axis.

In a particular embodiment, the structure of the inner and / or outer lateral surface of the drill bit tube can be achieved in that the entire cross-sectional profile of the tube is designed differently from the cylindrical shape. Such a profile tube can be composed of several, for example four, arcuate segments. However, polygonal tube cross sections, for. B. in the form of regular polygons. Cross sections are also available to be considered, in which the tube wall is arranged in a wave shape around a circular line.

The cross-sectional profiles mentioned can be obtained in various ways. You can, for example, by joining individual pipe segments, by shaping or kinking a finished pipe, e.g. B. circular cross-section, or directly in the manufacture of the tube, for. B. be created by extrusion.

In all previously proposed drill bit tube designs, the wall rigidity of the tube is considerably improved. As a result, considerably thinner wall thicknesses can be used for a drill bit tube. In addition, the friction surface on the drill wall or on the outer wall of the drill core is significantly reduced. This results in an effective reduction in friction. The consequence of this is that a significantly lower drive power is required in order to drill with a drill bit according to the invention.

An additional advantage results from a twisting of the embossing or of the entire profile tube in the opposite direction to the direction of rotation, as described above. The helix angle of such a pipe is, in contrast to a previously common spiral of drill bits, rather acute. A typical slope is e.g. B. between 5 cm and 20 cm for a full revolution of the embossing or the cross section along the axial direction with drill bits with a circumference of up to about 60 mm. The pitch or swirl angle should not be greater than 45 degrees. These steep swirl angles still ensure the increased rigidity of the tube, which means that the above-mentioned smaller wall thicknesses are still possible.

In addition, in this version, targeted drilling dust is produced in the channels created by the twisting of the embossing or cross-sectional shape.

Another advantage of a special design of a drill bit, which in particular can have a tube of the type mentioned above, is that instead of commercially available, curved and comparatively long drill segments at the drill end of the drill bit, shorter and straight drill segments can now be used.

The segments are arranged, for example, in the case of a profile tube with a polygonal or with a wave-shaped cross section, at the maximum or minimum deflections of the resulting circumferential lines. This results in a division of cuts between different drill segments. If the sequence between maximum and minimum deflections is suitably short, straight, short drill segments can be used without problems, which are typically only 10 - 15 mm long compared to a length of 20 mm - 30 mm in the case of a conventional drill bit design. The main advantage of using short and straight drill segments is that the same segments can be used for drill bit tubes of different diameters. The larger number of identical components results in a considerable cost advantage. This advantage also arises in the case of drill bit tubes of the type known hitherto.

Two embodiments of the invention are shown in the drawing and are explained in more detail with reference to the following description.

Fig. 1

eine perspektivische Darstellung eines erfindungsgemäß geprägten Bohrkronenrohres,

Fig. 2

eine Seitenansicht eines Rohres gemäß Fig. 1,

Fig. 3

einen Querschnitt gemäß Linie III in Fig. 2,

Fig. 4

eine Ausschnittvergrößerung aus Fig. 3,

Fig. 5

eine Darstellung einer flachen Abwicklung des Rohres gem. Fig. 1,

Fig. 6

eine perspektivische Darstellung eines Profilrohres für eine Bohrkrone,

Fig. 7

eine Seitenansicht einer Ausführung gemäß Fig. 5 und

Fig. 8

eine Stirnansicht eines Bohrkronenrohres gemäß den Fig. 6 und 7,

Fig. 9

eine perspektivische Darstellung eines weiteren Ausführungsbeispiels,

Fig. 10

eine Seitenansicht eines Bohrkronenrohres gemäß Fig. 9 und

Fig. 11

eine Stirnansicht einer Ausführungsform gemäß den Fig. 9 und 10,

Fig. 12 und 13

zwei perspektivische Darstellungen eines weiteren Ausführungsbeispiels und

Fig. 14

eine Stirnansicht einer Ausführungsform gemäß den Fig. 12 und 11.

Show in detail

Fig. 1

2 shows a perspective illustration of a drill bit tube embossed according to the invention,

Fig. 2

2 shows a side view of a tube according to FIG. 1,

Fig. 3

3 shows a cross section along line III in FIG. 2,

Fig. 4

3 an enlarged detail from FIG. 3,

Fig. 5

a representation of a flat development of the pipe acc. Fig. 1

Fig. 6

a perspective view of a profile tube for a drill bit,

Fig. 7

a side view of an embodiment according to FIGS. 5 and

Fig. 8

6 shows an end view of a drill bit tube according to FIGS. 6 and 7,

Fig. 9

2 shows a perspective illustration of a further exemplary embodiment,

Fig. 10

a side view of a drill bit tube according to FIG. 9 and

Fig. 11

9 shows an end view of an embodiment according to FIGS. 9 and 10,

12 and 13

two perspective representations of a further embodiment and

Fig. 14

an end view of an embodiment according to FIGS. 12 and 11.

The drill bit tube 1 according to FIGS. 1 and 2 has an inner 2 and an outer 3 lateral surface. The tube material is shaped so that diamond-shaped indentations 4 are distributed over the entire outer surface 3. Each diamond-shaped bulge 4 is framed by a corresponding diamond-shaped depression 5. The complementary image results on the inner lateral surface 2, i.e. diamond-shaped indentations 4 ', which are framed by corresponding diamond-shaped elevations 5', so that the material thickness remains essentially the same everywhere.

In connection, the diamond-shaped depressions 5 result in continuous intersecting channels, as illustrated by dashed lines 6, 7, for example. These continuous channels 6, 7 run parallel to the side walls of the diamond-shaped indentations 4 in a helical manner with a large slope around the outer circumference of the drill bit tube 1. In the present case, the pitch angle α is 45 °, for example. The diamond-shaped indentations 4 are aligned with their one diagonal parallel to the axis 8 of the drill bit tube 1. On the drilling side of the drill bit tube 1, drilling segments 20 are attached, which are shaped like a segment of a circle.

In particular in FIGS. 3 and 4, the alternating sequence of elevations 9 and depressions 10 along the circumference of the drill bit tube 1 is illustrated. The inner lateral surface 2 is designed to be complementary to the outer lateral surface 3.

The advantages according to the invention, the improved wall rigidity and the reduced friction due to the smaller friction surface with the drilling wall, which in the present case is formed by the surface of the elevations 9, are achieved by the helically surrounding channels 6 and 7 added advantage. These helical channels 6 and 7 improve the removal of the drilling dust when the drill bit is turned.

The illustration of the flat development 1 'of the drill bit tube 1 shows how such a tube 1 can be manufactured from flat material. Roll embossing can be used, for example, to emboss a sheet so that it receives the profile of the development 1 '. The drill bit tube is then e.g. produced by winding and welding.

6 - 7 relate to an embodiment in which the cross-section deviating from the cylindrical shape according to the invention is realized by trough-shaped grooves 11 of round cross-section. The circular cross section 12 of these grooves 11 can be clearly seen on the end face (see FIGS. 6 and 8). It is also clear here that no material reinforcements have been made. The drill bit tube 1 or parts thereof can be produced by molding.

In the present embodiment, four such grooves 11 are formed in the drill bit tube 1. This results in four round wall segments 13 between the grooves 11. The grooves 11 are formed in the wall of the drill bit tube 1 in such a way that they have a slight swirl. In particular in Fig. 7 it can be seen that the pitch angle angle α is kept very sharp. This arrangement of the grooves 11 with an acute angle of inclination angle α reinforces the stiffening of the tube wall in the axial direction.

The grooves 11, which were created by suitable shaping, appear on the outer lateral surface 3 as a depression. In contrast, the grooves 11 in the inner lateral surface 2 represent elevations. In the case of a drill bit which is provided with such a drill bit tube 1, drilling takes place between an inner 14 and an outer 15 circular envelope, as can be seen in the front view of FIG. 8. The wall segments 13 rest only on their outermost elevations 16 on the drilling wall. Likewise, the core in the interior of such a drill bit tube 1 is only touched by the grooves 11. This results in a significantly reduced friction, as already explained several times.

The embodiment according to FIGS. 9-11 is constructed similarly to the embodiment described above. Instead of the grooves 11, however, there are flat connecting edges 17 which are formed by kinking and on which four wall segments 13 in the form of segments of a circle are joined to one another. The course of the circumference of a drill bit tube designed in this way has four points of maximum diameter in the region of the center of the wall segments 13 and four positions of minimum diameter in the region of the connecting edges 17. The described embodiment of the drill bit tube 1 can also consist of a different number of wall segments 13. Three wall segments as well as five or an even larger number would be conceivable.

As in the exemplary embodiment described above, the grooves 11 have a slight swirl in the present example in the opposite direction to the direction of rotation of the drill bit. The angle of inclination angle α is again kept very acute. This in turn results in increased wall rigidity of the drill bit tube 1, as in the previous exemplary embodiments.

As can be seen in particular in FIG. 11 and already mentioned, the central regions of the wall segments 13 form the regions which are at the greatest distance from the axis of rotation of the drill bit tube and thus rub against the drilling wall during drilling. During drilling, these outermost elevations move along an outer envelope curve 15 which is shown in FIG Fig. 10 is visible as an outer contour due to the existing swirl within the drill bit tube 1. The inner envelope curve 14 is traversed by the edges 17 during drilling. In the region of the edges 17, channels are formed between the outer lateral surface 3 and the wall of the borehole, through which the drilling dust can be removed.

In the illustration according to FIGS. 12 to 14, an exemplary embodiment of a drill bit tube 1 according to the invention is shown, in which the outer 3 and the inner 2 lateral surface runs in a wave shape along the circumference of a circular cylinder by a corresponding shaping of the tube wall. Short drill segments 21 are attached at locations of maximum 22 or minimum distance 23 from the central axis of the drill bit tube 1. In contrast to the curved drilling segments 20 of the aforementioned exemplary embodiments, the short drilling segments 21 are no longer curved, but straight. The periods of the wave structure are so short that a sufficiently large number of the short and straight drilling segments 21 can be attached at a minimum distance 23 or maximum distance 22 in order to achieve a sufficient drilling result.

The wave-shaped configuration of the drill bit tube 1 results in an axial stiffening, as in all previous embodiments. Likewise, the friction of the drill bit tube 1 in the borehole is reduced, since this can only bear against the wall of the borehole or the drill core at the points with a minimum 23 or maximum 22 distance from the axis of the drill bit tube.

In spite of their different design, all of the above-described exemplary embodiments are distinguished according to the invention in that a stiffening structure is molded into at least one of the lateral surfaces of the drill bit tube 1. These stiffening structures can either be completely aligned in the axial direction or so deflected from the axial direction that the stiffening effect is retained in the axial direction.

These deviations from the axial alignment of the molded structures make it possible, for example, to incorporate a slight swirl with an acute angle of inclination angle α into the drill bit tube in various configurations in order to achieve the additional advantage of facilitating the transport of drilling dust. It is important, however, that the increased stiffening and the associated savings in material and the reduced wall friction, as a result of which lower drive powers are necessary during drilling, are retained.

Claims (14)

Drill bit tube (1) with an inner (2) and an outer (3) outer surface, characterized in that at least one outer surface (2, 3) has a structure (4, 5, 6, 7, 9, 10, 11, 16, 17) which stiffens the tube (1) at least in the axial direction without additional material reinforcements. Drill bit tube according to claim 1, characterized in that the structure is in the form of embossed elevations (9) and / or depressions (10) in a lateral surface (2, 3). Drill bit tube according to one of the preceding claims, characterized in that the embossed elevations and / or depressions (9, 10) are formed in the shape of a groove over the entire length of the tube. Drill bit tube according to one of the preceding claims, characterized in that the embossed elevations (9) and / or depressions (10) are self-contained. Drill bit tube according to one of the preceding claims, characterized in that the structure comprises the complete cross-sectional profile of the tube. Drill bit tube according to one of the preceding claims, characterized in that the cross-sectional profile is composed of arcuate wall segments (13). Drill bit tube according to one of the preceding claims, characterized in that the cross section of the tube (1) is polygonal. Drill bit tube according to one of the preceding claims, characterized in that the cross section of the tube (1) has an undulating course along a circular circumference. Drill bit tube according to one of the preceding claims, characterized in that the structure is formed both by the entire tube cross section and additional depressions and / or elevations are embossed in at least one of the lateral surfaces. Drill bit tube according to one of the preceding claims, characterized in that the structure has a twist with an acute twist angle α. Drill bit tube according to one of the preceding claims, characterized in that the drill bit tube has a friction-reducing coating. Drill bit with a drill bit tube according to one of the preceding claims, characterized in that short drill segments are present. Drill bit according to claim 12, characterized in that the drill segment length is between 10 mm and 15 mm. Drill bit according to claim 12 or 13, characterized in that the drill segments (21) are not curved.

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