Device for Coupling a Tool to a Hand-Held Tool-Driving Device

The invention proceeds from a device on hand-held tool-driving machines for coupling pounding and/or drilling tools as well as from a tool and tool holder used with that device.

Such a device is known from EP-433 876 A1 for a tool shank. Drilling tools are designed to rotate clockwise. They are driven by the tool holder of hand-held tool-driving machines accordingly so as to rotate in a right-handed manner, i.e., in the clockwise direction. Since FIG. 5 of EP 0 433 876 A1 shows a cross section (per II--II from FIG. 1) towards the shank end, the drive direction of rotation in that case is counter-clockwise. Thus in that case the narrower of the two coupling grooves that are opposite one another is positioned in front of the locking depression in the direction of rotation. These configurations of couplings, however, bring about a non-uniform torque loading on the tool shank and on the tool holder, since first of all the axial locking feature does not transmit any significant torques and since secondly the following wider coupling has a coupling flank that is located on the side of this coupling that faces away from the axial locking feature. The three coupling flanks in that case lie within a circumferential range of less than 180.degree.0.

The invention's configuration of couplings according to the characterizing feature of the invention has the advantage that torque loading is significantly more uniform over the circumference of the tool shank and the tool holder, since the torque-transmitting flank of the coupling positioned in front of the axial locking feature has now been moved substantially closer to the less loaded axial locking feature. Another advantage can be considered the fact that the more uniform torque loading also improves centering in the holder, counteracts one-sided wear, and reduces tool endangerment from shank breakage between the couplings.

As a result of the further measures, advantageous developments and improvements of the characteristics given in the main claims are obtained. For example, it is advantageous for long tool-shank life if the coupling that is at least partially opposite the axial locking feature corresponds in cross section approximately to that of the narrower of the two couplings that are opposite one another. However, in order to increase the wear allowance, particularly for the coupling gibs of the tool holder, it is advantageous if the coupling opposite the axial locking feature corresponds approximately to the cross section of the wider of the two couplings that are opposite one another. In this case wear can also be influenced by the use of appropriate materials for tool and tool holder.

A particular development of the device according to the invention consists in the fact that the tool shank of the tool designed in accordance with the invention is also designed to be compatible with known work holders in which the coupling and the axial locking feature are formed by two diametrically opposite, cylindrical locking bodies (e.g. Hilti drilling hammer TE10). For this purpose it is provided that the coupling groove on the tool shank that is at least partially opposite the axially closed locking depression be combined with an additional locking depression so that, on the one hand, when such a tool shank is inserted into a tool holder according to the invention the middle coupling groove receives a coupling gib of the tool holder, whereas, on the other hand, when the tool shank is inserted in the aforementioned known tool holder the second locking body engages with a locking effect in the second additional locking depression that is only partially closed on the axial ends.

Three embodiments of the invention are shown in the drawing and explained in greater detail in the following description.

FIG. 1 shows a cross section through a device according to the invention for torque transmission on a drilling hammer, having a tool holder and a shank inserted in it.

FIG. 2 shows a longitudinal section through the front section of the tool holder.

FIG. 3 shows as an additional embodiment the cross section through the shank of a tool, and

FIG. 4 shows the shank end of the tool.

FIG. 5 shows as a third embodiment a cross section through a tool shank with a combined coupling groove and locking depression,

FIG. 6 shows this tool shank in a known work holder, and

FIG. 7 shows the tool shank in a work holder according to the invention.

The device on tool-driving machines for coupling pounding and/or drilling tools in accordance with the invention, in particular on impact drilling machines and drilling hammers or pounding devices, comprises essentially a tool holder 10 acting as tool carrier and a tool shank 11 inserted in it of a tool 12 used for drilling and/or pounding. In the first embodiment shown in FIGS. 1 and 2, the work holder 10 is seated torsionally secure and in a manner known from WO 88/09245 at the end of a driven hollow-cylindrical tool spindle 13 of a drilling hammer that is not shown. In the tool spindle's rear area, not shown, a riveting set is guided such that it is axially movable, and said set is struck in a known manner by a pounding mechanism on the end of the tool shank 11. The work holder 10 has a seating hole 14 for the tool shank 11 and also an opening 15 for a locking body 16 inserted in said shank, which body can be moved radially to the outside in a known manner when the tool shank 11 is inserted in the seating hole 14 and is locked in the rest position shown in the figure by a locking bushing, not shown, in a known manner by means of elastic force.

The tool 12 is provided on the tool shank 11 with two coupling grooves 17 and 18 that are open towards the shank end, are opposite one another, and run axially, into which grooves two coupling gibs 19, 20 engage, which project inward into the seating hole 14 and run axially. The coupling grooves 17 and 18 and also their coupling gibs 19 and 20, respectively, are of different widths and have flanks running approximately radially on both longitudinal sides. Between the couplings formed as described is located an axially running locking depression 21 that is offset by 90.degree. in the tool shank, in which the cylindrical locking body 16 engages. The locking body is spherically rounded on the front and back ends, and the locking depression 21 shaped as a groove is curved spherically in a corresponding way and closed off, at least toward the shank end, so that the locking body 16 and locking depression 21 form an axial locking feature, for the purpose of preventing the tool from falling out or being pulled out of the tool holder 10 inadvertently. In the area of the tool shank 11 and the tool holder 10 opposite the axial locking feature there is an additional coupling, which is also formed by a coupling groove 22 running axially and open toward the shank end and by a coupling gib 23 in the seating hole 14 of the tool holder 10 that runs axially and engages into said coupling groove.

To achieve the most uniform possible loading of the tool holder 10 and the tool shank 11 of the device driven in the direction indicated by the arrow, it is provided that the wider of the two couplings opposite one another 17/19 and 18/20 be located in front of the axial locking feature 16/21 when viewed in the direction proceeding circumferentially from the other couplings. Although the torque-transmitting flank 18a of the wider coupling groove 18 is therefore a smaller distance away from the locking depression 21, this is balanced out, however, with respect to the uniform torque loading of the tool shank 11 by the fact that the locking body 16 transmits only a small torque to the tool shank. In this way, moreover, the centering and guidance of the tool shank is improved and the wear caused particularly in the case of couplings that have already deflected is reduced by better centering.

Whereas in the first embodiment as shown in FIGS. 1 and 2 the third coupling opposite the axial locking feature, comprising the coupling groove 22 and the coupling gib 23, has approximately the same cross section as the narrower of the two couplings that are opposite one another, comprising the coupling groove 17 and the coupling gib 19, in the second embodiment as shown in FIGS. 3 and 4 the third coupling opposite the locking depression 21, comprising the coupling groove 22a and the coupling gib 23a engaging into it, is shaped in cross section in correspondence to the wider coupling formed by coupling groove 18 and coupling gib 20. This design is advantageous, particularly with respect to a high wear allowance on the coupling gibs 20 and 23a of the tool shank 11a, whereas in the first embodiment the wear allowance on the tool shank 11 formed by the distance between the grooves 17, 18 and 22 is more favorable because of the two narrower couplings.

As indicated in FIG. 1 by the broken line, the groove root of at least one of the coupling grooves can run in chord-shaped fashion to the shank circumference in place of the rear flanks, in order, for example, to thereby increase the wear allowance of the tool holder, since the coupling gib interacting with it likewise runs on the rear side in chord-shaped fashion to the circumference of the seating hole. Essential to the invention, however, is the fact that on the three couplings 17, 19 and 22, 23 and 18, 20 located one behind the other on the shank circumference and hole circumference, respectively, starting from the axial locking feature 16, 21, the coupling flanks lie on a circumferential angle greater than 180.degree. and smaller than 240.degree., as a result of which a distribution of the torque-transmitting flanks is achieved that is favorable with respect to concentric running and wear.

In FIG. 5 the cross section through a tool shank 11b is shown in highly enlarged form as an additional embodiment, said shank being designed to be compatible for a known tool holder as shown in FIG. 6 as well as for a tool holder according to the invention as shown in FIG. 7. The locking depression 21 located in the upper area of the tool shank 11b is shaped to be closed axially on both sides, as shown in FIG. 4, so that in this way a completely sufficient axial locking action already occurs when a locking body 16 drops into place. The middle coupling groove 22b is located in the opposite lower area of the tool shank 11b and is overlapped by an additional locking depression 21a such that the two axial ends of said locking depression 21a are only partially closed, namely only as far as the end area 21b of said locking depression 21a protrudes beyond the cross section of the coupling groove 22b.

In order to retain a completely effective coupling flank 25 for the middle coupling groove 22b in the case of this compatible shank design, the additional, only partially closed-off locking depression 21a is located exactly diametrically opposite the axially closed locking depression 21, and the middle coupling groove 22b is arranged asymmetrically with respect to this additional locking depression 21a such that its coupling flank 25 is aligned with the flank 26 of this additional locking depression 21a that is located and runs in the direction of rotation.

If a tool with a tool shank 11b shaped as shown in FIG. 5 is inserted in a known tool holder 27 as shown in FIG. 6, then the coupling grooves 17 and 18 that are opposite one another remain free and the two locking bodies 16 diametrically opposite one another in the two openings 15 of a spindle 28 (shown in cross section) of the tool holder 27 drop into the locking depressions 21 and 21a with locking action. The second locking depression 21a is in this case weakened with respect to axial locking action by the cross section of the middle coupling groove 22b, indicated by a broken line, but this is immaterial, however, since the upper locking depression 21 that is completely closed axially already guarantees sufficient axial locking action. However, in this case as well, the coupling is secured by the coupling flank 25 of the middle coupling groove 22b.

FIG. 7 shows the cross section through a coupling device on tool-driving machines in accordance with the invention, said device having the compatible tool shank 11b shown in FIG. 5. In contrast to the tool holder 10 shown in FIG. 1, the middle coupling gib 23a in FIG. 7 that is partially opposite the locking body 16 is offset in the drive direction such that its coupling flank 29 is now diametrically opposite the flank 30 of the locking body 16 that is in front when viewed in the drive direction. This measure guarantees that even in the area of the additional, partially open locking depression 21a of the compatible tool shank 21b, the flank 25 of the middle coupling groove 22b is also fully loaded.

To prevent damage to the lower locking body 16 of the known tool holder shown in FIG. 6 resulting from the radially running coupling flank .25 of the middle coupling groove 22b, it can be advisable, in place of a radial coupling flank 25, if said flank and also the flank 29 interacting with it on the coupling gib 23a of the tool holder 10a shown in FIG. 7 be designed so as to be curved, following the course of the locking depression 21a, as indicated in FIG. 7 by the broken line. As an alternative, however, the additional locking depression 21a can also be combined with a middle coupling groove 22, as shown in FIG. 1, or 22a, as shown in FIG. 3, that is diametrically opposite the upper locking depression 21. Since in any case the upper locking depression 21 is sufficient for axial locking action, the middle coupling groove 22 located opposite to it and the middle coupling gib 23 engaging into it can also have in cross section the curved shape of the upper locking depression 21 in order to guarantee compatibility of the tool shank 11 with a tool holder 27 as shown in FIG. 6.