Milling tool and process for underreaming drilling holes

The invention relates to a substantially circular cylindrical milling cutter, in particular for hand drills and hammer drills, with an appropriate for inclusion in a chuck shaft, a milling head and with a pivotable radially cutting tool, wherein the cutting head is axially slidably connected to the shaft at least having an opening extending axially recess and from an automatically assumed relaxation position into a clamping position can be pushed, and the cutting tool is lowered into the relaxation position of the milling head completely in the recess, while the in the clamping position of the milling head in the radial direction beyond the outer surface milling head protrudes.

The invention further relates to a method for milling cylindrical holes to form conical extensions or undercuts for receiving expansion cone-anchors.

For security reasons, heavy duty anchors, as they are for example used for fastening of facade panels to concrete walls or masonry, not only used in cylindrical holes, but in conically undercut bore holes, wherein the undercut is adapted to a conical bolt the anchor in order to by driving the anchor sleeve the conical bolt not only to achieve a spreading of the anchor sleeve in the radial direction, but also jamming the cone bolt in conical undercut portion of the milled hole and thus higher separation values ​​in the axial direction.

It is already known to undercut cylindrical drill holes using a conical drill or mill, and using a form suitable for inclusion in the chuck of a hand drill or a rotary hammer pivot shaft, the interposition of a spring and a pressure sleeve a centering is fitted, the a milling head which carries the actual milling, receives. The pivot shaft and the centering can be combined with a Bohrsauger for extraction of the drilling dust. The desired conical undercut of the cylindrical bore hole is then generated by circular swinging the hand drill and the hammer drill with simultaneous axial compression.

This known method has a number of serious disadvantages: The location and the geometric shape of the undercut depends on the user of the milling tool manual skill. A dimensionally accurate, the anchor used exactly matched undercutting is not amortized, but only by chance possible because change location and geometric shape of the undercut, depending on how big is the manually applied to the tool axial pressure and in which radius as evenly how many times the drill or rotary hammer are pivoted circular.

A particularly serious disadvantage of the known method is that the user can not see from the outside whether the undercut produced by it is sufficient or not, ie whether fits the cone of the anchor bolt into the conical undercut or whether the undercut nor too small or already is large.

Finally, the centering of the known milling tool can clamp not only worn drill with too small Schneideneckmaß but also in mint drills downhole. They must then be dissolved by vigorous, jerky axial withdrawal of the switched off machine, which can lead to damage easily when the jerky withdrawal does not take place exactly axially.

From DE-U-69 17 790 a milling tool of the type mentioned is known. In this known milling tool, the milling head is slotted from its front end side to side within the cavity formed by the slot about an axis radially pivotable cutting tool and a resetting of the cutting tool to be able to accommodate serving compression spring. The cutting tool comprises a cam that is moved in an axial displacement between the shaft and cutting head from the front end wall of the shaft against the action of the mentioned compression spring in the direction towards the front end of the milling head. In this way, the cutting tool rotates about its mounting axis, and the cutting edge is pivoted radially outwardly so protrudes in the radial direction beyond the outer surface of the milling head beyond. With axial discharge, for example, during withdrawal of the tool from the wellbore, the cutting tool under the action of the mounted inside the milling head pressure spring is pivoted back to its original position in which the cutting tool is completely sunk in the slot of the milling head.

A similar milling tool is also known from DE-A-3024656.

Although this known milling tool enables a the influence of individual, manual user independent, geographically and spatially precisely defined, conical undercut activity, but the tool has not been successful in practice. The mechanically most heavily loaded part, namely the milling head, so much mechanically weakened by the necessary slot, which must accommodate the entire cutting tool and the required for its retrieval spring, that the required wear resistance and durability is not achieved. But above all, is the cavity formed by the slot in the milling head which merges open into the cylindrical guide for the shaft within the cutter head, very quickly with debris, so that no longer allow the moving parts within the shortest time move unless not before and cleaned thoroughly after milling. The penetrating into the cylindrical guide for the shaft in the interior of the milling head debris also acts like an abrasive and can cause excessive wear on the most sensitive for the operability of the cutting tool bodies.

The invention is therefore based on the object to provide an improved cutting tool with which it is possible to produce the one hand of the user from the influence of individual, manual activity independent, geographically and spatially precisely defined, conical undercut, but then in the risk of jamming of the tool borehole and the jamming of moving parts within the tool to exclude by penetrating debris or at least greatly reduce, while increasing the maintenance and ease of operation and the tool life.

The invention further has for its object to provide a method for molding cylindrical holes to form conical extensions or undercuts can be achieved with the location and geometric shape of the undercuts reliably than before in a predeterminable manner in the absence of individual, manual influence in any time repeatable manner can.

This object is achieved with a milling tool of the type mentioned in the present invention that the milling head as a recess at least one extending in the axial direction of the longitudinal groove and the shaft a extending at least in the axial direction, engages in the longitudinal groove and having her fitted guide member that the cutting tool is articulated to the guide member and that the cutting tool is supported slidingly movably on a surface rising to the jacket of the milling head from the bottom surface of the longitudinal groove.

According to the invention therefore dispenses with the use of a pivot shaft, whereby individual, manual influence user abilities on location and geometric shape of the forming undercut be completely ruled out. Since the cutting tool in the defined relaxation position of the milling head of the milling tool according to the invention does not protrude radially over the periphery of the milling head, occurs during the insertion of the cutter into a predrilled cylindrical drill hole a no milling action. Only when the front end of the cutting head abut against the cone-shaped "front wall" of the cylindrical drill hole and the shaft under axial pressure is displaced axially in the direction towards the cutter head enters the cutting tool, which slides along on the rising supporting surface, from the envelope surface of the milling head radially in always increasingly apparent until the milling head relative to the shank, its defined clamping position has been reached, beyond which a further axial displacement is no longer possible and which simultaneously defines the maximum deflection of the cutting tool in the radial direction. The axial thrust applied by the user will neither cause a local displacement of the undercut nor a change in the geometric shape of the undercut; it can possibly affect the speed with which the undercut is formed at the predetermined position by design and with the predetermined geometric shape.

The milling head of the milling tool according to the invention does not comprise a through slot and not the mechanical stability impairing cavity, but only a relatively small longitudinal groove depth. The cutting head also has no internal bore was needed for guiding the stem. For these reasons, no debris can penetrate into the interior of the milling head. Since all sensitive moving parts are inside the stem and remain in milling a conical undercut outside the cylindrical bore hole, it is entirely excluded from the milling tool according to the invention that constitute the moving parts by penetration of the drilling dust or jammed or the abrasive action of the drilling dust be damaged or worn. Another advantage of the milling tool according to the invention is finally the fact that the dimensions of the cutting tool are adapted to the dimensions of the longitudinal groove in the milling head, which not only enables a particularly simple and inexpensive manufacture but also easy accessibility and maintenance of the cutting tool. Finally, in the design according to the invention can be dispensed in its rest position for the purpose of collection of the swung-cutting tool on any kind of additional spring inside the milling head.

It is apparent to those skilled readily apparent that the milling tool according to the invention each commercial heavy duty anchor can be adjusted by appropriate dimensioning of the cutting tool, the longitudinal groove in the milling head and the rising surface for supporting the cutting tool of the size and shape of the cone. can for each anchor type and each anchor size thus committed a suitable milling tool to be kept, whereby the allocation of milling and anchor can be facilitated by appropriate color or other markings.

Preferably, the milling head of the milling tool according to the invention against the action of a compression spring from the expansion position to the clamping position is axially movable, so that the milling head, seen relative to the shaft, always returns automatically under the action of the spring force of the compression spring in the relaxation position when not on the milling tool axial external pressure is applied, at the same time the cutting tool through the guide member with the shaft connected to the rising surface slidably movable supported also automatically under the action of the spring force of the compression spring returns to the milling head in its initial or rest position in which it completely is recessed in the longitudinal groove of the milling head, that is does not project beyond the outer surface of the milling head.

The shaft preferably has a bore whose longitudinal axis coincides with the longitudinal axis of the milling tool and in which the compression spring is arranged. However, embodiments are also conceivable in which a plurality of annularly arranged longitudinal bores are provided in the shaft instead of or in addition to such central bore into each of which a coil spring is used. The decisive factor is that the milling head and shaft are axially relative to each other and that said two parts automatically return to their initial position as soon as the milling tool no axial pressure is exerted. In an advantageous embodiment of the invention it is further provided that the milling head carries a guide bolt located in its longitudinal axis, which is guided in the central longitudinal bore of the shaft and is acted upon by the compression spring. This embodiment not only ensures a secure axial displacement of the milling head and the shaft against each other and also provides a wear-resistant and maintenance-friendly design is because the milling head by means of the guide pin, as well as the compression spring, can be particularly easily replaced.

Preferably, the shaft has a extending in the axial direction, for its part, through the bore leading slot and guided in the bore guide bolts at least one bore, whose longitudinal axis runs transversely to the longitudinal axis of the guide bolt and in the plane of symmetry of the elongated hole, wherein in the in the guide pin located hole a pin is used, which is guided in the slot and forms a stop and thus defines the relaxation position of the milling head. The slot in this case represents nothing more than a guide for the pin and simultaneously contributes to the twist-free guidance of the milling head and shaft in their relative movement in the axial direction.

The at least one hole in the guide pin of the milling head advantageously has an internal thread, while the pin is a threaded pin, so that the through the slot of the shaft always freely accessible grub screw only needs to be unscrewed to separate the cutting head from the shaft, if a new mounted milling head or the pressure spring is to be renewed.

If provided in the guide pin of the milling head several holes, the distance to the milling head and shaft relative to one another can be moved in the axial direction can be changed depending on which of these holes in the abutment-forming pin or threaded pin inserted or screwed becomes. Since this route or the amount of axial displacement with the movement of the cutting tool connected to the rising surface of the milling head, can be achieved by changing the amount of the axial displacement and the degree of deflection of the cutting tool in the radial direction and thus the depth of the forming undercut change.

A further advantageous embodiment of the milling tool according to the invention is characterized in that the free end of the guide member and the cutting tool each have about half the width of the longitudinal groove. In this way, the free end of the guide member and the cutting tool can be side by side to accommodate within the longitudinal groove, the free end of the guide member is simultaneously a stable lateral support for the cutting tool even and especially when the cutting tool in the clamping position of the milling head its maximum deflection learns in the radial direction.

Preferably, the cutting tool is articulated by means of a pivot axis-forming pin to the free end of the guide member or to a side wall of the longitudinal groove of the milling head, depending on whether the rising to the envelope surface of the milling head from the base of the longitudinal groove surface on which the cutting tool is supported slidingly movably , seen from the shaft end, increases toward the front end of the milling head up to the surface area or seen reversed from the front end of the milling head fro rises toward the shank end to the outer surface of the milling head. In the former case arises an undercut, whose largest diameter is the maximum possible depth of the cylindrical bore hole, while in the second case an undercut arises shifted the maximum diameter of lying inside the masonry of the cylindrical hole backwards, to the entrance of the borehole toward is.

In a further advantageous embodiment of the milling tool according to the invention, the shaft has an end face facing the milling head and the cutting head on an end face facing the shank, which form together a stop and define the tensioned position of the milling head. The handling of the milling tool is particularly simple and safe: The milling tool needs in this design to be simply inserted into the predrilled cylindrical drill hole until the front end of the milling head abuts the end of the hole, and under the pressure exerted by the user axial pressure of the shaft in the axial direction so long moved against the milling head, until the end face of the shaft abuts the end face of the milling head. This position of two relatively axially movable parts defines the clamping position of the milling head and at the same time, the maximum deflection of the cutting tool in the radial direction. Once the two faces meet, the desired undercut is by design on predetermined location and completed in the predetermined geometric shape, without the need for constituting any kind of control. As a further axial displacement over the formed by the two end faces stop position is not possible, the user relieves the instrument through which the milling head automatically under the action of the compression spring returns to its relaxation position while returning the cutting tool to the bottom of the longitudinal groove in the milling head, so that the milling tool can be pulled out from the borehole without the risk of jamming is.

According to a further advantageous embodiment, the milling head a self-centering, tapered front end, preferably in the form of a lens head on. This achieves that the undercut to be formed is formed coaxially with the predrilled cylindrical borehole.

Preferably, the cutting tool of the milling tool according to the invention is a hard metal plate, whose one narrow side is bevelled in such a manner that its inner longitudinal edge is longer than the outer longitudinal edge. The chamfer causes the hard metal plate easily fall back even when returning the milling head in the relaxation position or the removal of the tool from the borehole to the bottom of the longitudinal groove in the milling head, if the rotation of the hard metal plate affected by the rotational axis forming bolt through debris is.

The shaft preferably has a tapered rear end for insertion into a chuck or a drill chuck of a drilling machine, to ensure universal applicability in connection with all common on the market drills and rotary hammers.

The rear end of the shaft may have in known manner at least one drive groove and at least one extending in the axial direction groove for a locking body of a quick-action chuck.

When the end face of the tapered end of the shank rückwartigen has a deformable under axial force survey, can be easily found in a used milling whether it wrong, say for example was with activated hammer a hammer drill, operated. Thus, the survey serves as a guarantee marker. Upon actuation of the hammer mill a hammer drill, the survey is deformed. The deformable survey can pointy or round expire; they may for example be conical or frustoconical. The survey may be soldered or attached in some other way or palmed and may consist of metal or plastic. The survey may also be formed by the protruding end of a pin inserted into the stem end.

Furthermore, the cutter head may have in its lateral surface a thread-like extending groove for feeding out of debris from the wellbore.

Finally milling tool according to the invention can with an additional, known debris-suction device, eg a Bohrsauger with suction hose, be combined.

The inventive method for milling cylindrical holes to form conical extensions or undercuts for receiving expansion cone-anchors is finally characterized by the use of the milling tool according to the invention.

The invention will be explained with reference to the drawing. <dl id="dl0001"><dt>Fig. 1</dt><dd>is a plan view of an embodiment of a milling tool is in its relaxation position according to the invention;</dd><dt>FIG. 2</dt><dd>is a plan view of the clockwise rotated (from the milling head seen from) 90 ° milling cutter in accordance with FIG. 1;</dd><dt>Fig. 3</dt><dd>is a plan view of a section along line AB in Figure 1 in the 90 ° rotated position of Fig. 2.</dd><dt>Fig. 4</dt><dd>is a plan view of a portion of a second embodiment of the milling tool according to the invention, also in the expansion position, which differs from the first embodiment shown in Figs 1 to 3 in the arrangement of the cutting tool. </dd><dt>Fig. 5</dt><dd>is a plan view of a section along line CD in Figure 4, wherein the cutting tool is, however, rotated clockwise (seen from the milling head in) by 90 °.</dd><dt>Fig. 6</dt><dd>is a plan view of the section according to Figure 5, but in the clamping position of the milling head.</dd><dt>Fig. 7</dt><dd>shows schematically, partly as a plan view, partly in section, of the first embodiment of the milling tool according to the invention according to FIG 1 in the expansion position, the tool clamped in the chuck of a drill and the milling head is inserted into a predrilled cylindrical drill hole. and</dd><dt>Fig. 8</dt><dd>is a partial plan view of the milling tool according to Fig. 7, but rotated clockwise (seen from the milling head in) by 90 ° and directly before reaching the clamping position of the milling head.</dd></dl>

In the first embodiment of the milling tool according to the invention according to the figures 1 to 3 which consists of wear-resistant tool steel produced, substantially circular cylindrical milling cutter 1 from the shaft 2 and the milling head 3 than the two main parts 11 are relative to each other in the direction of the longitudinal axis.

The shaft 2 has a tapered end 2a, which is suitable for inclusion in the chuck of a conventional hand drill or a hammer drill. In the drawn embodiment according to Figures 1 to 3 the rear tapered end 2a of the shaft 2 is designed to receive in a keyless chuck of such a machine; For this purpose, the tapered shaft end 2a of at least one rotary driving groove extending in the axial direction 28 (Fig. 2 and 3) and at least one extending in the axial direction of the receiving groove 29 for accommodating a locking body of a quick-action chuck. The end face of the tapered rear end 2a of the shaft 2 has a soldered or be turned elevation 13, which serves in particular under axial force, is deformable and as a guarantee marker.

The shaft 2 has a central bore 24 (Fig. 3) whose longitudinal axis coincides with the longitudinal axis 11 of the milling tool. 1 In the bore 24 a formed as a spiral spring compression spring 23 is inserted. The bore 24 serves as a guide for a guide pin 35, integral with the milling head 3, optionally releasably connected, wherein the guide pin 35 is located in the longitudinal axis of the milling head. 3

In the shank 2 is also the longitudinal axis is a the shank completely into a 11 plane containing penetrating elongated hole 25, which extends in the axial direction and also through the central bore 24 passes (Fig. 1 and 3) and a guide for a pin 37 (Fig. 3) is inserted into a bore 36 of the guide pin 35th The pin 37 provides an abutment for the under the influence of the compression spring 23 is in the absence of automatically taking place externally applied axial pressure axial displacement of the cutting head 3 and defined as simultaneously relaxing position illustrated in Figures 1 to 3 the milling head 3 and thus the entire tool. 1

Under the influence of an external, tapered at the end 2a of the shaft 2 applied axial pressure can be overcoming the spring force of the compression spring 23, provided that the milling head 3 is held stationary, for example, in a well in the axial direction, move the shaft 2 as long in the axial direction until the flat end face 27 abuts the shank 2 to the planar end face 38 of the cutting head 3 (see FIG. FIG. 8). In this axial displacement of the guide pin 35 enters the bore 24 a further and presses the spiral spring 23 together, the pin 37 is shifted in the oblong hole 25 in the direction of the tapered rear end 2a of the shank second

In the guide pin 35 can more consecutive, parallel bores 36, which can carry an internal thread, can be provided so that the pin 37 may be formed as a threaded pin with screw head forms an adjustable stop, depending on which of the bores 36, the pin 37 is inserted. In this manner, firstly the bias of the compression spring 23 and, secondly, the distance between the two end faces 27 and 38 to adjust different in the relaxation pose depending on the needs.

The cutting head 3 has at least one longitudinal groove extending in the axial direction 31, which is preferably cut in the lateral surface 33 of the substantially circular-cylindrical milling head 3rd The shaft 2 has at least one extending in the axial direction, 31 engaging in the longitudinal groove, and their matched guide member 21 to which a cutting tool 22 is pivoted, the rising to a from the base 32 of the longitudinal groove 31 to the outer surface 33 of the cutting head 3, preferably curved , surface 34 (Fig. 3) is supported slidingly movably.

In the above described axial displacement of the shaft 2 in the direction of the cutting head 3, also the guide member 21 moves, which is part of the shaft 2 and which projects like a finger or a push rod on the end face 27, whereby the cutting tool 22, preferably as a formed carbide tip and articulated by means of an axis of rotation forming bolt 26 to the free end 21a of the guide member 21, slides within the longitudinal groove 31 toward the front end 39 of the milling head. 3

The free end 21a of the guide member 21 and the cutting tool 22 each about half the width of the longitudinal groove have 31 (Fig. 1), so that the cutter 22 is always supported as extensively as possible on the side wall of the tapered free end 21a of the guide member 21.

Since the cutter 22 is supported on the base 32 of the longitudinal groove 31 to the outer surface 33 of the milling head 3 rising surface 34, the cutter 22 26 moved to the acting as a pivot pin in the radial direction, ie transverse to the longitudinal axis 11 of the milling tool 1 once of the shaft 2 and the milling head 3 are moved towards each other in the axial direction. The stop formed by the end faces 27 and 38 thus defines both the clamping position of the cutting head 3 as well as the maximum deflection of the cutting tool 22, wherein this radially beyond the outer surface 33 of the milling head 3 protrudes (Fig. 8).

Preferably one narrow side 22a of the hard metal plate used as a cutting tool 22 is tapered such that its inner longitudinal edge 22b 22c is longer than the outer longitudinal edge. The incised, truncated free end 21a of the guide member 21 is preferably of the chamfer of the hard metal plate 22 are changed accordingly (Fig. 3), so that the transition from the clamping position (Fig. 8) in the relaxation position (Fig. 1 to 3), the cutting tool 22 also then easily and smoothly to its original position, when it is completely submerged in the longitudinal groove 31, returns when debris is in the groove 31st

Finally, in the lateral surface 33 of the milling head 3 is preferably a thread-like extending groove 40 for feeding out of debris cut from the borehole (FIGS. 2 and 8).

In a second embodiment of the milling tool according to the invention according to figures 4 to 6 the same parts are provided with the same reference numerals. The second embodiment differs from the first only in that the base 32 of the longitudinal groove 31 to the outer surface 33 of the milling head 3 rises, preferably curved, surface 34 does not rise toward the front end 39 of the milling head 3, but reversed from the front end 39 in toward the shaft 2 increases. In order to achieve the radial outward movement of the cutting tool 22 during the axial displacement of the shaft 2 in the direction of the cutting head 3, the cutting tool 22 in this second embodiment in the side wall of the groove 31 of the cutting head 3 by means of the bolt 26 and not on the guide member hinged 21 or its tapered end 21a.

In both embodiments, the leading end 39 of the cutting head 3 is preferably self-centering and a tapered form, for example in the form of a lens head.

In the application of the milling tool according to the invention or the inventive method is a procedure in which a cylindrical bore 4 in concrete or masonry 5 (Fig. 6 and 7) will be created in advance in the usual way. The clamped into the keyless chuck 12 a hand drill or a hammer drill milling tool according to the invention (Fig. 7) is inserted into the cylindrical bore 4 and added with simultaneous axial pressure in rotation. Here the stem 2 moves, as described above, for as long as the cutter head 3 in the axial direction until the end faces 27 and 38 meet. During the axial displacement of the cutting tool 22 is simultaneously moved radially outwards, whereby the conical widening or undercut 10 (FIG. 6 and 8) is formed. formed that it reaches the stop 27 and 38 formed by the end faces, ie reaching the clamping position, simultaneously means that the maximum radial displacement of the cutting tool 22 is reached and thus also the undercut 10 in the construction of conditionally predetermined geometric shape and on which by design predetermined location has been such that the certain for the undercut hole cone anchor can be introduced without problems after switching off the drill and the removal of the tool and absolutely precise fit sitting, so that the maximum possible separation value of the anchor will actually be achieved. The resulting when milling dust is conveyed out of hand by the groove 40 of the bore and which may be mounted on the other by an addition to the mill, commercial Bohrsauger away. Preferably, the hole 4 slightly shorter (less deep) is created when the length of the milling head 3 from the tip to the end face 38 corresponds to (see Figure 6 - 8..); the produced during milling debris can then dissipate easily.

A significant for practical use advantage of the milling tool according to the invention is that the milling head 3 and the cutting tool 22 in the event of damage or the transition to larger or smaller bore diameter or other forms of desired undercuts can be easily replaced, with no special tools, but only a screwdriver is required. It must in fact only the pin 37, which is freely accessible through the slot 25 in the shaft 2, to be removed to remove the milling head 3 or to pull out the guide pin 35 from the hole 24th Here, the guiding member 21 is simultaneously pulled out of the groove 31 so that the bolt 26 with which the cutting tool 22 is mounted, also is exposed and can optionally be withdrawn or unscrewed, if the hard metal plate is to be renewed. When the cutting head 3 has been removed, the compression spring 23 is freely accessible and can be, if desired, also exchanged. Then optionally exchanged milling head 3 with its guide pin 35 again inserted into the bore 24 and the extent pressed against the spring 23 until the hole 36 is visible in the slot 25 so that the pin 37 is inserted through the slot 25 in the bore 36 and can be attached or screwed.

Further modifications and equivalent embodiments of the invention are possible within the framework and scope of the claims.