WO1991011630A1 - Self-drilling fastening - Google Patents

Abstract

In a flat drilling bit (1) for insertion by interlocking or friction engagement in the shank (8) of a self-drilling fastening, there is a recess (14) in the cutting section projecting freely beyond the shank (8) in the fitting position. This recess (14) is used accurately to hold the cutter (1) by means of one or more grips having projections corresponding to the recesses. This permits accurate fitting of the flat bit (1) and the shank (8) in precise axial alignment.

Description

 Self-drilling fastening element

The invention relates to a self-drilling fastening element with a shaft and a cutting plate which is prefabricated separately from drilling steel or hard metal and is mounted at one end of the shaft and which, in the assembled state, has a fastening section received in the shaft and a cutting section projecting freely over the end of the shaft.

Such a self-drilling fastener is known from DE 28 01 962 C2, which will be discussed in more detail below.

In general, more and more cutting tips are being used in self-drilling fasteners, since with such cutting tips optimal materials can be selected for a drilling process and the drilling performance can thus be increased.

These cutting tips are inserted in the shaft of a fastening element in a form-fitting and / or non-positive manner, the correct position of these cutting tips being essential. It is based on an exact axis alignment, i.e. pay attention to an exact alignment to the longitudinal axis of the shaft of the fastening element, in order to thereby eliminate vibrations during subsequent use. For example, in a self-drilling fastener, the cutting tip may pull out if the cutting tip and the shank of the fastener are not precisely aligned.

When pinching or grinding on drill bits formed on the shaft of self-drilling fastening elements, the exact center axis alignment of the actual drill bit is not a problem in itself, since the self-drilling fastening elements are clamped in the jaws during their processing and the tools which are to produce the drilling section are exact can be matched to the clamping jaws. When using cutting plates, however, the problem is essentially different. Whether the cutting plates on the shank of the fastening element are held purely by positive or frictional connection or whether additional processing is carried out by means of casting, soldering or welding, it is always necessary to have an exact, precise mounting of the cutting plate beforehand, especially for a proper drilling process in the cutting tip, the tip of its cutting edge must be exactly aligned with the central axis of the • shaft of the fastening element. This requires the cutting plate to be grasped in the correct position even while the cutting plate is being mounted on the shaft of the fastening element, but this has hitherto caused problems in the prior art.

In the case of the self-drilling fastening element in the form of a screw, which is known from DE 28 01 962 C2 already mentioned at the outset, there is at least one groove, a hole or at the side edges or on the broad sides of the fastening section of the cutting insert which engages in the longitudinal slot of the screw shank a survey is provided which is used to form a positive and non-positive fixed connection between the cutting tip and the screw shank. When it is inserted, the elevation is pressed into the base of the slot in the shaft, so that a secure centering of the cutting tip is ensured. Likewise, part of the shaft is pressed into the hole or the recess in the fastening section of the cutting tip in order to produce a form-fitting holder. Finally, it is possible, for mounting and additional centering, to connect a thickening on both sides to the fastening section of the cutting tip that can be inserted into the slot on the screw, the thickening of which forms stop edges for the slotted ends of the shaft of the screw. This mounting and centering, which is then available in the assembled state, presupposes that the cutting tip has already been centered in another way during the assembly process in order to align its axial direction and the central axis of the shaft with one another. If this were not the case, the cutting tip would not be centered on the shaft in the finally assembled state. The grooves, holes or elevations provided on or in the fastening section of the cutting tip cannot serve for centering during the assembly process, because the fastening section has to be inserted into the slot in the shaft of the fastening element, cannot be recorded for centering purposes. Thickenings, which are provided on the cutting tip in order to achieve better heat dissipation in the cutting edge area, are also unsuitable for centering during the assembly process.

From VDI guideline 3370, pages 6 - 8, it is known to use perforations for centering. Then, for example, a hole present in the fastening section of the cutting tip of the screw according to DE 28 01 962 C2 could be brought into engagement with a mounting plate shown in Figure 22 of the VDI guideline in order to center the cutting tip during its processing. However, that would be a centering process which could only take place during the manufacture of the cutting tip and would be carried out with a hole which is later not available for centering purposes during the assembly process of the cutting tip because the cutting tip, as explained above, during of mounting cannot be grasped on the fastening section to be inserted into the shaft. The VDI directive never specifies that if there is no perforation, blind perforation can be provided for centering. Such blind perforation would, however, in turn not be available for the centering process during assembly, since it would also be provided in the fastening section in order to be able to center the cutting tip when machining it.

The object of the invention is to design the cutting tip in the case of a self-drilling fastening element of the type mentioned at the outset in such a way that it can be gripped in a precise position during the mounting of corresponding grippers and inserted in the shaft of the fastening element in exact alignment.

This object is achieved according to the invention in the case of a fastening element of the type mentioned at the outset in that in the region of the freely projecting cutting section for precise registration when it is mounted on the shaft on at least one side at least one recess is designed as an assembly aid, the number, position and / or shape is in a fixed preselected relationship to the axial direction of the cutting tip. These measures according to the invention make it possible to grasp the cutting section of the cutting tip in a precise position by means of one or more grippers during the assembly process, since these grippers have projections corresponding to the recesses, which have the cutting tip in its cutting section, which after assembly is free over the end of the Shaft protrudes, can grasp. It is therefore possible to produce self-drilling fasteners in accordance with the regulations, ie fully automatically. Even if an additional positive and / or non-positive connection of the cutting tip to the shaft of the fastening element takes place, a provisional fixation is already ensured by the friction given when the cutting tip is inserted, this fixing then being guaranteed in the exact axis direction. Gen in the present invention provided Ausnehmun¬ serve only as an assembly aid, so have after insertion and fixing of the cutting tip no function to fulfill ^', * therefore not load-bearing after the process of assembling more somehow to Zen¬ tration or set of mutual proper Position between the two parts plugged together. By arranging the recesses provided as an assembly aid in the cutting section, the cutting tip can be gripped in an exact position and kept aligned until it is finally fixed to the shaft.

Advantageous embodiments of the invention form the subject of the subclaims.

In the embodiment of the invention according to claim 2, practically two grippers with the same design can be used when mounting the cutting tip for feeding it. In addition, with such a configuration, there is the possibility that the cutting tips have the same surface design on both broad sides, with which e? it is irrelevant whether the Montaqe has one or the other broad ^* * --- above.

For special purposes, the embodiment of the invention can be advantageous, in which a different number of recesses is provided on the two broad or narrow sides of the cutting tip. This then means two different rent grippers, which can grip the cutting tip. This is Ausge¬ staltung especially if it daily on ei ^p exact Mon¬ arrives a cutting tip advantageous in which always the same page of the same Breit¬ up or should face down.

It is expedient if the recess (s) in the embodiment of the invention is or are cylindrical, spherical, conical, truncated, pyramid or truncated pyramid-shaped. Depending on the thickness of the cutting tip, it is possible to choose a different shape of the recesses without the cutting tip being weakened, for example.

In the case of openings which pass through the cutting tip, in the embodiment of the invention according to claim 5 these are circular or elliptical or polygonal in cross section. If, in the embodiment of the invention according to claim 7, these openings are rectangular, trapezoidal or elliptical in cross-section, then only one opening is sufficient, since even then, the gripping plate can be precisely aligned by appropriate design of the grippers.

However, it is also possible, in accordance with the embodiment of the invention according to claim 6, to arrange two or more than two continuous openings in the axial direction or successively to the axial direction of the cutting tip, such an embodiment being particularly advantageous if the Openings are made circular in cross section.

Embodiments of the invention are described below with reference to the drawings. Show it:

1 shows a front view of an embodiment of a cutting tip;

FIGS. 2 to 4 each show a section along the line II in FIG. 1 with different recess variants; 5 shows a front view of a further embodiment of a cutting tip;

6 to 8 each show a section along the line II-II in Fig. 5 with other recess variants;

9 and 10 show two embodiments of grippers for holding the cutting tip during the assembly process with inserted cutting tip;

11 and 12 a self-drilling screw in front and side view;

FIGS. 13 to 17 show various further embodiments of cutting tips, partially shown in the use position in a shaft;

18 and 19 in front and side view of a self-drilling rivet with inserted cutting tip;

20 and 21 are a front view and a partially cut-away side view of the cutting tip used in the self-drilling rivet according to FIGS. 18 and 19.

The cutting tip 1 according to FIGS. 1 to 4 has a fastening section 15 with an extension 2 and a cutting section 16 with a cutting edge 3 on the opposite side. The extension 2 serves to insert the cutting tip 1 into an opening on a self-drilling fastening element. With this cutting tip 1, recesses in the form of recesses 4 on one or both sides or in the form of a continuous opening 14 are formed on the cutting section 16 which projects freely above the end of the shaft 8 in the assembled state. In the embodiment according to FIG. 2, corresponding depressions 4 are provided on both broad sides of the cutting tip 1 and in the embodiment according to FIG. 4 only on one broad side. A continuous opening 14 is formed in the embodiment according to FIG. 3. In the embodiment according to FIG. 2, the recesses 4 formed on both sides are arranged qleichachsiq qeqen lying one above the other. In the embodiment according to FIGS. 5 to 8, the cutting tip 1 has a wedge-shaped edge region at its mounting end, this design serving for special mounting in a slot of a self-drilling fastening element.

In this embodiment, circular recesses 4 or a continuous opening 14 are provided in cross-section, two recesses 4 or openings 14 being arranged in succession transversely to the axial direction 17 of the cutting tip 1. With such an arrangement, centering mounting of the cutting tip 1 by means of grippers is also possible.

In the embodiments shown, recesses of the same design in the form of depressions 4 or openings 14 are provided on the two broad sides of the cutting tip 1. It would also be conceivable to provide a different number of recesses on the two broad sides of the cutting tip 1, or else a different arrangement of the same, so that they do not lie opposite one another on the same axis.

In the embodiment according to FIG. 8, the depression 4 is, for example, spherical. However, the depressions can also be cylindrical, truncated, truncated, pyramid or truncated pyramid-shaped. The through openings 14 can also be designed in cross-section in a wide variety of ways, it being expedient to choose a circular or elliptical or polygonal cross-section. In the case of a single continuous opening 14, as is shown, for example, in FIG. 3, the cross section of the opening 14 is expediently rectangular, trapezoidal or elliptical in shape, in order to achieve a centering possibility by appropriately designing the grippers.

9 and 10 a schematic representation of such grippers 6 can be seen. These grippers 6 have elevations 7 corresponding to the recesses 4 or openings 14 to be corresponding, so that the cutting tips 1 can be held in a form-fitting and precisely aligned manner when they are installed between two grippers. 11 and 12, a cutting tip 1 is shown in the assembled state on a self-drilling screw. The cutting tip 1 is inserted into a corresponding slot at the free end of the shaft 8. In this embodiment of the cutting tip 1, a trapezoidal recess 4 or a corresponding continuous opening 14 is provided in order to be able to mount the cutting tip 1 in an exact axial alignment with the shaft 8. During assembly, the cutting tip 1 is inserted into the slot on the shaft 8 by a snug fit or press fit, so that a correct alignment of the cutting tip 1 with respect to the shaft 8 is already ensured after this assembly. Whether this type of fastening is sufficient or whether the cutting plate 1 is finally fixed by additional deformations on the shaft 8 or by soldering, welding or gluing, the exact alignment of the two parts with respect to one another is always ensured.

13, an additional opening 10 is provided in its fastening section 15, into which the end region of the shaft 8 is pressed for the positive mutual connection between the cutting plate 1 and the shaft 8. It can be seen from this that this additional opening 10 cannot serve as an assembly aid, since this opening 10 comes to rest in the end region of the shaft 8 and does not lie in the cutting section 16 of the cutting tip 1 which projects freely over the end of the shaft in the assembled state. Two continuous openings 14 or corresponding depressions 4 are again provided as assembly aids. Two openings 14 are provided here, which are arranged in succession in the axial direction 17 of the cutting tip 1.

14 shows an embodiment of a cutting tip 1 which is inserted into a shaft 8, the opening 14 provided here or a corresponding recess 4 being trapezoidal in cross section.

In the embodiment according to FIGS. 15 and 16, an opening 14 with a rectangular cross section is again provided on the broad side of the cutting tip 1, recesses 11 being provided in the fastening section 15 of the cutting tip 1 opposite the cutting edge 3. can be seen which are used for subsequent positive and non-positive connection with the shaft 8. A partial region of the shaft 8 is then pressed into these depressions 11. Only the continuous opening 14 shown is relevant as an assembly aid. The same applies to the opening 14 shown in the exemplary embodiment according to FIG. 17. Here, similar to the embodiment according to FIG. 13, a cutting-like projection 9 is provided, which is in the bottom of the slot provided in the shaft 8 penetrates for additional fixation of the cutting tip 1.

18 and 19 is a self-drilling rivet 12 in which a cutting tip 1 is used as the drilling element. At the free end of this self-drilling rivet 12, a corresponding slot is provided, in which the cutting tip 1 is inserted in a positive and / or non-positive manner. There may also be an additional central opening into which an extension 2 provided on the cutting tip 1, as shown in FIGS. 20 and 21, can penetrate. There are two depressions 4 which follow one another in the axial direction 17 of the cutting tip 1 and which are designed in the form of spherical sections.

In the foregoing description and in the drawings are exemplary ^'shown üh- approximately examples and described in which the Breitsei¬ the cutting tip th 1 corresponding recesses 4 are provided or respective through openings 14. It would also be possible, on the two narrow sides, and only on one or both narrow sides to provide corresponding depressions, so that corresponding notches, indentations or the like would be provided on the side edges of the cutting tip 1. Such depressions on the narrow sides can also be provided in addition to depressions or openings on the broad sides of the cutting tip 1. It would also be possible to provide corresponding elevations instead of the depressions on the broad sides of the cutting tip 1, but this will probably be out of the question for manufacturing reasons, especially since these cutting tips are expediently manufactured as stamped parts from sheets, so that it is easier to produce depressions together with the punching process instead of corresponding elevations. In the drawings, only one self-drilling screw and one self-drilling rivet are shown as possible uses of the cutting tip 1. However, such cutting tips can be used wherever a drilling, milling or cutting process is to be carried out in any way. With all such cutting tips, for which an exact position in the assembled state is important, this exact position is achieved by the assembly aid measures described here.

Claims

Claims 1. Self-drilling fastening element with a shaft (8) and a cutting plate (1), which is prefabricated separately from drilling steel or hard metal and is mounted at one end of the shaft (8) and which, in the assembled state, has a fastening section (8) received in the shaft (8) 15) and has a cutting section (16) protruding freely over the end of the shaft (8), characterized in that in the area of the freely projecting cutting section (16) for accurate registration when it is mounted on the shaft (8) on at least At least one recess (4, 14) on one side is designed as an assembly aid, the number, position and / or shape of which is in a fixed, preselected relationship to the axial direction (17) of the cutting tip (1). 2. Fastening element according to claim 1, characterized in that recesses formed on both sides in the form of depressions (4) lie opposite one another coaxially. 3. Fastening element according to claim 1, characterized in that a different number of recesses in the form of depressions (4) is provided on the two broad or narrow sides of the cutting tip (1). 4. Fastening element according to one of claims 1 to 3, characterized in that the recess (s) (4) as a cylinder, spherical section, cone, truncated cone, pyramid or truncated pyramid-shaped recesses) is or are. 5. Fastening element according to claim 1, characterized in that the recess (s) is or are designed as a continuous, cross-sectionally circular or elliptical or polygonal opening (s) (14). 6. Fastening element according to claims 1 and 5, characterized gekennzeich¬ net that at least two through openings (14) in the Achs¬ direction (17) or transverse to the axial direction (17) of the cutting plate (1) are arranged in succession. Fastening element according to claims 1 and 5, characterized in that, in the case of a single continuous opening (14), its cross section is rectangular, trapezoidal or elliptical.