Drilling device for making holes with undercuttings.

p0001The invention relates to a drilling device for producing drilled holes with an undercut, with a drilling tool with radial drill shank superior side cutting, the drilling tool is connected via an external thread with a, a clamping shaft having a rotary hammer drill chuck with internal thread, with a spherical collar to form a pivot bearing is provided on a stop plate.

p0002A drilling device according to the preamble is known from the German Offenlegungsschrift 34 23 633rd Another drilling is described in DE-PS 30 27 408th

p0003The principle of this known and the present boring device based on the fact that an undercut is generated by the side cutting edges of the drill head by pivoting the drill with drill bit holder in a swivel bearing.

p0004The known drilling devices comprise a drill shank on a provided at the end of external thread which is screwed into the internal thread of the drill bit holder. This two-piece embodiment is generally necessary because the bit can not be passed with radially outwardly extending side cutting through the existing bore-centering tube and the centering shoulder due to the larger diameter. In addition, the drill is designed as a tool wear, while the complex design of the shaping drill chuck can be used with clamping and spherical collar again.

p0005Such drilling devices are used in rotary hammers with for example a speed of l000 U / min and z. B. 3000 strokes / min. By hammering stress of the tool, the thread between the drill and drill bit holder is subject to substantial change conditions. In order to avoid breaks in the threads, in general, a round thread is used. The pounding stress can easily lead to a loosening of the screw connection between the drill and drill bit holder, so that no rigid connection between these two parts is overturned. Rather, the cutting tool may even run against the drill chuck a certain pivoting movement by the loosened thread, whereby the drilling is particularly adversely affected for producing the undercut.

p0006The invention has for its object to avoid the aforementioned disadvantages and in particular to provide a drilling device, in which a better guidance between drilling tool and drill bit holder is guaranteed even under lockerndem thread. The object of the invention is also, by design measures from the beginning of the thread to a loosening to avoid.

p0007This object is starting solved by a drilling of the initially characteristic type according to the invention that the drilling subsequent to the external thread has an additional guide pin which engages positively in a matched to the guide pin blind hole following the internal thread of the drill chuck.

p0008The invention has the advantage that the connection between the drill and the drill chuck is not confined to the area of ​​the thread with a certain play relative to the known devices. By fomschlüssige connection of additional guide pin in particular bending moments and bending stresses are transmitted via the guide pin and not via the thread between the parts. This causes the thread between the two parts is a total relief, the impact energy from the drill over the guide pin and not via the threads on the drill bit can be transmitted. This largely avoids a loosening up and a load of the thread.

p0009Should solve the thread yet, so the drill remains guided by the guide pins carefully and not stagger by a thread play back and forth.

p0010The measures specified in the dependent claims, advantageous refinements and improvements of the drilling apparatus according to the main claim are possible.

p0011The embodiment of the invention according to dependent claim 2 having bottomed in the blind hole bottom guide pin is alternatively seen. This has - as already mentioned - the advantage that the impact energy can be introduced by the drill chuck directly into the drill over the guide pin and not via the threads. there remains a gap between the extent blind hole bottom and lower end of the guide pin, the energy transfer must take place exclusively through the threads. The thread must then be correspondingly strongly attracted.

p0012According to another embodiment of the invention according to dependent claim 3, the guide pin must have a certain minimum length to exert its guiding function. As shortest length, a ratio between length and diameter of the pin of l be considered. Particularly advantageous is a length / diameter ratio of. 3

p0013The length of the guide pin should roughly correspond to the length of the thread according to the development of the invention according to dependent claim. 4 That provides a reasonable relationship between guide length and thread footprint.

p0014In known manner the further development of the invention, to the extent that the external and internal thread are formed as round threads, in particular in accordance with DIN 405th

p0015The alternative embodiment of the invention according to claims 6 and 7 relates to an additional guide means of the drilling tool in the area above the thread. This second guide face an even better supporting effect of the drilling device is achieved.

p0016Advantageous and expedient embodiments of the invention are shown in the drawing and explained in more detail in the following description. Show it<ul><li>Fig. L is a section through the inventive drilling in masonry,</li><li>FIG. 2 is a view of the drill with an extended guide pin,</li><li>FIGS. 3 and 4, an alternative embodiment of the invention according to Fig. L and 2.</li></ul>

p0017To describe the structure and operation of the drilling apparatus according to the invention is generally referred to the previously mentioned DE-OS 34 23 633 corresponding literature references. From the same applicant as the laid-open specification mentioned above, the principle of the drilling apparatus according to the invention under the designation "ZYKON-drill" is known. For this there are brochures of the company "Fischer anchors".

p0018The drilling device shown in FIG. L (L0) is composed of a drilling tool (II) with the drill shaft (l2) and drill point (L3), with radially outwardly directed cutting side (L4). The drilling tool (ll) has in its region on a round thread (l5) as an external thread, which engages in a correspondingly adapted internal thread (l6) a drill chuck (l7). The drill chuck (l7) comprises a clamping shaft (l8) for inclusion in a hammer drill, not shown.

p0019The drill chuck (l7) has in its upper region a spherical collar (l9), which cooperates with a correspondingly adapted trough (20) a stop plate (2l) to form a pivot bearing. The stop plate made of metal (2l) is extended upwards by a tubular spigot (22).

p0020In the embodiment, the stopper plate (2l) of a plastic housing (23) is surrounded, which is cup-shaped with downward-pointing opening. In this case (23) engages from below aufzusteckendes closure member (24) having a cup-shaped, upwardly directed wall (25). The plastic housing (23) and the closing part (24) are connected by a thread connecting them (26). To the opening of the closing part (24) by the plastic housing (23) of the lower portion (27) of the closing part (24) is designed as a knurled nut (27).

p0021Axial securing of the drill chuck (l7) against the stop plate (2l) by a collar (28) located on the inner wall (29) of the closure member (24) is supported.

p0022The material to be drilled is illustrated by the reference numeral (30). The drilling device according to Fig. L met accordingly in the well bottom position against the wall (3l) to.

p0023The generation of the undercut (34) in the material to be drilled (30) is carried out in a conventional manner by a pivoting movement of the spherical Federal (l9) in the trough (20) of the stop plate (2l), ie through full drawing a tumbling motion of the drill bit (l3 ) with the lateral edges (l4). Reference is made to DE-OS 34 23 633rd

p0024According to the invention, the apparatus following the round thread (l5) an additional guide pin (32) which in a blind hole (33) of the drill adapter (l7) is positively, that engages without play movement. This gives the drilling tool (ll) provide additional guidance in the drill chuck (l7), which is not restricted exclusively to the management of the affected with match thread.

p0025The execution of the drilling tool (II) with an additional guide pin (32) is shown in Fig. 2 in an individual representation.

p0026In FIG. 2, the ratio of the length l₁ of the guide pin (32) to the diameter (D) of the guide pin is also shown. This ratio (l₁) to (D) should ≧ l, preferably. 3

p0027. As shown in Figure 2, the ratio between the length of the guide pin (l₁) and the length of the thread (l₂) is approximately L should: l. This ensures that the thread is supported by a sufficiently long guide pin.

p0028If an external thread diameter of l0 mm example a thread length of l₂ = 20 mm and a length of Zapf l₁ is = 20 mm is selected. The guide pin (32) itself then has a diameter (D) ≈ 6 mm. Of course, these dimensions may vary in accordance with matched orders of magnitude.

p0029In the figures 3 and 4, an alternative embodiment of the invention according to Fig. L and 2 is illustrated. In addition to the guide pin (32) comprises the drilling tool (II) above the thread (l5') a further guide surface (35), formed in the exemplary embodiment as a circular cylindrical surface. This additional upper guide surface (35) is supported on the inner cylinder bore (36) of the bit reception (L7) so that the thread (l5') both below the thread (l5') through the guiding pin (32) and above the thread (l5' ) is supported by the guide cylinder (35). The upper (35) and lower (32) support can possibly be designed as conical support with correspondingly adapted shape in the drill chuck (l7). This is especially true if the drill diameter of the drill shaft (l2) is substantially larger than the diameter of the thread (l5, l5') and the diameter of the associated guide means (32, 35).

p0030In FIG. 4, the drilling tool (LL') is prepared analogous to the illustration in FIG. 2. The additional upper guide surface (35), the thread (l5') be performed shortened in its axial length (l₄). The preferred ratio of the lengths (L₃) of the guide pin (32) to (l₄) of the thread (l5') to (l₅) of the additional guide cylinder (35) is (l₃: l₄: l₅ = 2: l: l).

p0031The arrangement of FIG. 3 and 4 has the advantage that the tolerances of the thread (l5') can be kept very large by the double guide means of the guide pin (32) and the guide cylinder (35), as the thread take no more managerial responsibilities have to be.

p0032. In a drilling tool (LL') with a drill shaft diameter of l0 mm, for example, l₃ ≈ l5 - 20 mm, l₄≈ l0 mm and l₅≈ l0 mm.

p0033Incidentally, the apparatus is according to the representation in Fig. 3 and 4 of the embodiment according to Fig. L and 2.