Abstract
The invention relates to a tool device for a ground milling machine, particularly a road milling machine, a recycler, a stabilizer or a surface miner. The tool device comprises a milling chisel with a highly wear-resistant chisel tip, particularly comprising PCD material, and a chisel shaft extending along a longitudinal axis, and a chisel holder with a shaft receptacle, the chisel shaft of the milling chisel having at least one tapering section narrowing in a direction away from the chisel tip. Furthermore, a fastening device is provided, which is designed in such a way that it pulls the milling chisel along its longitudinal axis and in the direction away from the chisel tip into the shaft receptacle, the shaft receptacle of the chisel holder being designed complementary to the chisel shaft of the milling chisel in such a way that the tapering section, when braced by the fastening device, bears against the chisel holder in the shaft receptacle in a frictionally locking manner shaft receptacle. The chisel holder also comprises a base holder and a quick-change chisel holder, the base holder comprising a holder receptacle for receiving the quick-change chisel holder, and the quick-change chisel holder comprising the shaft receptacle, and the fastening device being designed in such a way that it pulls both the milling chisel along its longitudinal axis and in the direction away from the chisel tip into the shaft receptacle as well as the quick-change chisel holder into the holder receptacle in the base holder. The invention also relates to a milling chisel and a quick-change chisel holder for such a tool device and a ground milling machine with such a tool device.
Claims
1. A tool device for a ground milling machine, particularly a road milling machine, a recycler, a stabilizer or a surface miner, comprising: a milling chisel having a highly wear-resistant chisel tip, particularly comprising PCD material, and a chisel shaft extending along a longitudinal axis; and a chisel holder with a shaft receptacle, wherein the milling chisel has a wear protection cap made of tungsten carbide, the chisel tip being attached to the wear protection cap by means of hard-soldering, and the wear protection cap being attached to the milling chisel by means of hard-soldering, the chisel shaft of the milling chisel has at least one tapering section narrowing in a direction away from the chisel tip; a fastening device is provided, which is designed in such a way that it pulls the milling chisel along its longitudinal axis and in the direction away from the chisel tip into the shaft receptacle; the shaft receptacle of the chisel holder is designed complementary to the chisel shaft of the milling chisel in such a way that the tapering section, when braced by the fastening device, at least partly bears against the chisel holder in the shaft receptacle in a frictionally locking manner; the chisel holder comprises a base holder and a quick-change chisel holder, the base holder comprising a holder receptacle for receiving the quick-change chisel holder, and the quick-change chisel holder comprising the shaft receptacle; and the fastening device is designed in such a way that it pulls both the milling chisel along its longitudinal axis and in the direction away from the chisel tip into the shaft receptacle and the quick-change chisel holder into the holder receptacle in the base holder.
2. The tool device according to claim 1, wherein the chisel tip comprises a material with a Vickers hardness according to DIN EN ISO 6507-1:2006 03 of at least HV 2400, preferably at least HV 4000, more preferably at least HV 6000, more preferably at least HV 8000, and most preferably at least HV 10000.
3. The tool device according to claim 1, wherein the tapering section of the chisel shaft extends over at least 25%, preferably over at least 50%, more preferably over at least 75%, and most preferably over at least 90% of the shaft length, for example, essentially over the entire shaft length.
4. The tool device according to claim 1, wherein the milling chisel has a chisel head, and that the tapering section of the chisel shaft directly adjoins the chisel head.
5. The tool device according to claim 1, wherein the quick-change chisel holder bears against the base holder in a frictionally locking manner and the milling chisel bears against the quick-change chisel holder in a frictionally locking manner and/or the milling chisel and the quick-change chisel holder each have at least one tapering section, the tapering section of the milling chisel bearing against the quick-change chisel holder, and the tapering section (36) of the quick-change chisel holder bearing against the base holder, the tapering sections of the milling chisel and the quick-change chisel holder narrowing in particular in the direction away from the chisel tip, and/or the tapering sections of the milling chisel and the quick-change chisel holder are shaped as truncated cones and the surface lines of the truncated cones each have an angle (α, β) relative to the longitudinal axis of the milling chisel, and that the angle (α) of the tapering section of the milling chisel is as large as or larger than the angle (β) of the tapering section of quick-change chisel holder, the angle (α) of the tapering section of the milling chisel relative to the longitudinal axis in particular being greater than the angle (β) of the tapering section of the quick-change chisel holder relative to the longitudinal axis by least 0.2°, preferably by up to 2°, and more preferably by 0.8°.
6. The tool device according to claim 1, wherein the shaft receptacle and the holder receptacle each have an opening on their face sides opposite the chisel tip, the openings being positioned one behind the other, and that the milling chisel is guided through both the opening of the quick-change chisel holder as well as through the opening of the base holder, the milling chisel, with its shaft end opposite the chisel tip, in particular projecting out of the opening of the base holder and beyond the latter.
7. The tool device according to claim 1, wherein it has an expulsion recess, which is made in such a way that, when the tool device is assembled, there is a clearance between the chisel head and a face side of the chisel holder opposite the backside of the chisel head, the expulsion recess in particular being formed as a slant on the backside of the chisel head, particularly as a slant having an angle (γ) relative to a vertical to the longitudinal axis of the milling chisel in the range of from 15° to 25°, preferably in the range of from 18° to 22°, and more preferably of 20°, or as a notch.
8. The tool device according to claim 1, wherein the milling chisel, on the shaft end opposite the chisel tip, has a fastening section with an external thread, and that the fastening device is a nut, particularly a self-locking nut, which is screwed onto the fastening section against the chisel holder, a sealing disk being provided in particular, which is braced between the nut and the chisel holder and which seals the shaft receptacle of the chisel holder to the outside.
9. (canceled)
10. The tool device according to claim 1, wherein the milling chisel and the chisel holder are made in such a way that a form locking device is provided between the milling chisel and the chisel holder for securing against rotation, which is designed in such a way that the milling chisel is prevented from rotating about its longitudinal axis in the chisel holder.
11. The tool device according to claim 10, wherein the form locking device comprises a recess on the chisel holder and a projection on the milling chisel, or vice versa, the recess and the projection being designed complementary to each other in such way that, when the tool device is assembled, they engage each other in the circumferential direction to the longitudinal axis of the milling chisel in a form locking manner and prevent the milling chisel from rotating about its longitudinal axis in the chisel holder, the recess in particular being formed on the face side opposite the backside of the chisel head and the projection in particular being formed on the backside of the chisel head, in particular integrally with a wear protection cap.
12. The tool device according to claim 11, wherein multiple projections, or recesses, and expulsion recesses are provided, and that the projections, or recesses, are arranged so as to alternate with the expulsion recesses in the circumferential direction of the chisel shaft, the projections, or recesses, and the expulsion recesses being in particular arranged symmetrically in such a way that the milling chisel can be installed after rotation by 90°, more preferably by 180°, without changing the configuration of the projections, or recesses, and the expulsion recesses in the tool device.
13. The milling chisel or the quick-change chisel holder for the tool device according to claim 1.
14. The ground milling machine with the tool device according to claim 1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The invention will be explained in further detail below with reference to the exemplary embodiments illustrated in the figures. In the schematic figures:
[0038] FIG. 1 is a side view of a ground milling machine;
[0039] FIG. 2 is a perspective view of a tool device from the diagonal front right;
[0040] FIG. 3 is an exploded view of a tool device;
[0041] FIG. 4 shows a longitudinal cross-section through a tool device;
[0042] FIG. 5 shows a longitudinal cross-section through another tool device;
[0043] FIG. 6 shows a longitudinal cross-section through a tool device as the milling chisel is being detached;
[0044] FIG. 7 is a perspective view of a milling chisel from the diagonal back;
[0045] FIG. 8 is a perspective view of a tool device with a partially detached milling chisel from the diagonal front right; and
[0046] FIG. 9 is a perspective view of a tool device with a partially detached milling chisel from the diagonal left back.
DETAILED DESCRIPTION
[0047] Like components are designated by like reference signs. Recurring components are not separately designated in all figures.
[0048] FIG. 1 shows a ground milling machine 1, in this case, a road-milling machine of the center rotor cold milling machine type. The ground milling machine 1 comprises an operator's platform 2 with a driver's seat and a control panel, a machine frame 3, and a drive engine 4. The drive engine 4, for example, a diesel engine, powers inter alia the running gears 6, the milling drum 9, and the discharge conveyor 5. The milling drum 9 is mounted in the milling drum box 7 such that it can rotate about a rotation axis 10 extending horizontally and transversely to the working direction a. During work operation of the ground milling machine 1, the milling drum 9 mills the ground 8 in the working direction a. Loose milled material is transferred via the discharge conveyor 5 to a transport vehicle not depicted and hauled away by it.
[0049] To mill the ground 8, the milling drum 9 is equipped with tool devices 11, one of which is depicted in the perspective view of FIG. 2. The tool device 11 comprises a milling chisel 14 and a chisel holder 29. In the exemplary embodiment shown, the chisel holder 29 has a two-piece design and comprises a base holder 12 connected to the milling tube of the milling drum and a quick-change chisel holder 13. The base holder 12 is welded to the milling tube of the milling drum 9 via its bottom side 15. It is also possible to attach the base holder 12 with its bottom side 15 to a platform not depicted or to a segment of another support structure, which platform or support structure may in turn be attached, for example, welded on the milling tube. What is essential is that the base holder 12 is connected directly or indirectly to the milling tube via its bottom side 15. The quick-change chisel holder 13 attached on the base holder 12 has a projection designed as a chip breaker 16, which is used in work operation to crush blocks of milled material and to direct milled material past the chisel holder 29. Furthermore, the quick-change chisel holder 13 engages an undercut of the base holder 12 in the area of chip breaker 16 in a form locking manner and thus contributes to a positive force transfer, particularly of forces that are directed vertically to the longitudinal axis of the milling chisel 14. The milling chisel 14 is partially accommodated by the chisel holder 29 and is retained therein by the fastening device 19, which in this case is a self-locking nut, so that the milling chisel 14 is fastened to the milling drum 9 by the chisel holder 29.
[0050] FIGS. 3 and 4 further illustrate the design of milling chisel 14. FIG. 3 shows the milling chisel 14 in a side view, while FIG. 4 is a longitudinal cross-sectional side view through the milling chisel 14 installed in the chisel holder 29 along the longitudinal axis 35 of the milling chisel of FIG. 3. The milling chisel 14 comprises a chisel head 40 and a chisel shaft 20. The chisel head 40 in turn comprises a chisel tip 17 with PCD material and a wear protection cap 18 consisting of hard metal, in this case tungsten carbide. In the area in which the chisel head 40 covers the chisel holder 29 or the quick-change chisel holder 13, the milling chisel 14 may either rest directly on the ring surface 27 surrounding the shaft receptacle 26 or be minimally spaced from it without there being direct contact between the ring face 27 and the tool head 40, as is shown in FIGS. 4 and 5. In this area, there is then a clearance 33, which will be described in further detail below.
[0051] As illustrated in particular in the sectional view of FIG. 4, the wear protection cap 18 surrounds a base body 31 of the milling chisel 14 in the area of the tool head 40. Due to the design of the wear protection cap 18 as a cap, on the one hand, the chisel achieves a high resistance to wear and, on the other hand, hard metal material is saved. The chisel tip 17 is attached to the wear protection cap 18 by means of hard-soldering at a soldering spot 28. The wear protection cap 18 in turn is attached to the base body 31 of the milling chisel 14 by means of hard-soldering at another soldering spot 28. Overall, the milling chisel 14 extends along the longitudinal axis 35. In the illustrated exemplary embodiment, the milling chisel 14 is designed rotationally symmetric about the longitudinal axis 35. In the present context, the chisel shaft 20 is that part of the milling chisel 14 which directly adjoins the chisel head 40 opposite the chisel tip 17. The chisel shaft 20 is designed integral with the base body 31 of the milling chisel 14 and consists, for example, of heat-treated steel, particularly 42CrMo4. Overall, the chisel shaft 20 therefore forms a tie rod with a tensile strength of at least 800 N/mm.sup.2.
[0052] The chisel shaft 20 serves to fasten the milling chisel 14 to the chisel holder 29, while the chisel head 40 serves to cut and crush the ground material. For this purpose, the chisel shaft 20 has a shaft length 34 along the longitudinal axis 35 of the milling chisel 14, which comprises multiple sections of the chisel shaft 20. That is, the chisel shaft 20 has a tapering section 23, a cylindrical section 22, and a fastening section 21. The tapering section 23 directly adjoins the chisel head 40 on the backside 47 of the chisel head 40 opposite the chisel tip 17. It is characterized by the fact that it narrows from the side directed towards the chisel head 40 in the direction towards the shaft end 43 with respect to its cross-section transversely to the longitudinal axis. Thus, in the tapering section 23, the diameter or the cross-sectional area of the chisel shaft 20 decreases along the longitudinal axis 35 in the direction towards the shaft end 43. In the illustrated exemplary embodiment, the tapering section 23 is shaped as a truncated cone and does not extend along the entire shaft length 34, but connects to another cylindrical section 22 having a constant diameter or cross-sectional area along the longitudinal axis 35. On the shaft end 43, there is provided a fastening section 21, which is likewise cylindrical, having an external thread, which is used for fastening the milling chisel 14 in the chisel holder 29, as will be described in further detail below.
[0053] The fastening of the milling chisel 14 in the chisel holder 29 can be seen in particular in an overview of FIGS. 3 and 4. The chisel holder 29 has a shaft receptacle 26, which is designed complementary to the shape of the chisel shaft 20. In the illustrated exemplary embodiment, this means that the shaft receptacle 26 also has a tapering section 39 and a cylindrical section 38. The tapering section 39 of the shaft receptacle 26 is designed particularly in such a way that the lateral surface of the truncated cone-shaped tapering section 23 of the chisel shaft 20 fully bears against the inner wall of the shaft receptacle 26 in the tapering section 39 when the milling chisel 14 is installed in the chisel holder 29. The shaft receptacle 26 extends through the entire chisel holder 29, including the quick-change chisel holder 13 and the base holder 12. The shaft end 43 and, at least partly, also the fastening section 21 of the chisel shaft 20 protrude out of the chisel holder 29 on its end opposite the chisel tip 17. For this purpose, the chisel shaft 20 is guided through an opening 32 in the quick-change chisel holder 13 and an opening 41 in the base holder 12. A fastening device 19, in this case, a self-locking nut, is screwed onto the external thread of the fastening section 21, which is screwed on with a sealing disk 25 against the chisel holder 29. A pulling force is exerted on the milling chisel 14 by firmly tightening the fastening device 19, which pulls the milling chisel 14 into the shaft receptacle 26 of the chisel holder 29. In doing so, the pulling force of the fastening device 19 is so strong that the milling chisel 14, with the tapering section 23 of the chisel shaft 20, bears against the tapering section 39 of the shaft receptacle 26 in a frictionally locking manner and is firmly fixed in particular during work operation, i.e., does not rotate and is secured against rotation during milling operation.
[0054] FIG. 4 illustrates that, according to the present invention, the fastening device 19 for the milling chisel 14, in the case of a two-part chisel holder 29, is used to fasten the milling chisel 14 to the quick-change chisel holder 13 as well as the quick-change chisel holder 13 to the base holder 12. For this purpose, the base holder 13 has a holder receptacle 37, which is designed complementary to a tapering section 36 of the quick-change chisel holder 13. The tapering section 36 of the quick-change chisel holder 13 also narrows in the pulling direction of the fastening device 19 analogously to the tapering section 23 of the chisel shaft 20. In the illustrated example, the tapering section 36 of the quick-change chisel holder 13 is likewise designed as a truncated cone. Through the pulling force exerted by the fastening device 19, the quick-change chisel holder 13 is pulled into the holder receptacle 37, the tapering section 36 of the quick-change chisel holder 13 bearing against the inner wall of the holder receptacle 37 in a frictionally locking manner. The quick-change chisel holder 13 is further secured against rotation relative to the base holder 12 by the quick-change chisel holder 13 engaging an undercut of the base holder 12 in the area of the chip breaker 16.
[0055] Overall, therefore, for installing the tool device 11 according to FIGS. 2, 3, and 4, the base holder 12 is welded onto the milling drum 9. The quick-change chisel holder 13 is then inserted into the holder receptacle 37, and the milling chisel 14 is inserted into the shaft receptacle 26 until the fastening section 21 of the chisel shaft 20 protrudes from the backside opening 41 of the base holder 12. Thereafter, the fastening device 19 and the sealing disk 25 are screwed onto the fastening section 21, i.e., its external thread. By screwing the fastening device 19 against the chisel holder 29, all components of the tool device 11 are fastened to each other. To remove a worn milling chisel 14, the fastening device 19 must be released. After that, the milling chisel 14 can be driven out from the chisel holder 29 by effecting strokes onto the protruding fastening section 21 on the shaft end 43 with a conventional hammer. To ensure that the milling chisel 14 is driven out of the shaft receptacle 26 without the quick-change chisel holder 13 likewise being released from the holder receptacle 37, the angle α of a surface line of the truncated cone-shaped tapering section 23 of the chisel shaft 20 relative to the longitudinal axis 35 of the milling chisel 14 is greater than the angle β of a surface line of the truncated cone-shaped tapering section 36 of the quick-change chisel holder 13 relative to the longitudinal axis 35. As a result, the expulsion force of the milling chisel 14 in the quick-change chisel holder 13 is less than the expulsion force of the quick-change chisel holder 13 in the base holder 12. The auxiliary line provided in FIG. 5 for depicting the angle α is parallel to the longitudinal axis 35 of the milling chisel 14. Due to the fact that the angle α of the milling chisel is greater than the angle β of the quick-change chisel holder 13, only the milling chisel 14 is released from the shaft receptacle 26 upon an impact on shaft end 43, whereas the quick-change chisel holder 13 remains in the holder receptacle 37. If the quick-change chisel holder 13 is also to be replaced, the expulsion opening 30 in the base holder 12 can be used for this, through which, for example, a suitable tool may be inserted in the base holder 12, with which the quick-change chisel holder 13 can be driven out of the holder receptacle 37.
[0056] FIG. 5 shows a tool device 11 with a one-piece chisel holder 29. In this case too the chisel holder 29 receives the milling chisel 14 and is welded directly onto the milling drum 9 or welded to the milling drum tube via a platform or a segment of a support structure. Thus, apart from the structural division into quick-change chisel holder 13 and base holder 12, all previous explanations also apply for the tool device 11 according to FIG. 5. In particular, the shaft receptacle 26 of the chisel holder 29 according to FIG. 5 corresponds to the shaft receptacle 26 of the quick-change chisel holder 13. Also, the one-piece chisel holder 29 according to FIG. 5 likewise has an opening 42, from which the milling chisel 14 projects on the end opposite the chisel tip 17.
[0057] An alternative option for removing the milling chisel 14 from the chisel holder 29 can be taken in particular from FIGS. 6 and 7. FIG. 7 shows an embodiment of a milling chisel 14, in which two expulsion recesses 24 are provided on the backside 47 of the chisel head 40, i.e., that side of the chisel head 40 which is located opposite the chisel tip 17. The expulsion recesses 24 are designed as inclined surfaces or chamfers, which, in the illustrated example, have an angle γ (FIG. 6) of 20° relative to a vertical to the longitudinal axis 35 of the milling chisel 14. As can be seen in particular in FIG. 6, the expulsion recesses 24 form a clearance 33 between the chisel head 40 and the ring surface 27 of the chisel holder 29. If the fastening device 19 is released, as shown in FIG. 6, an installer can insert a tool, for example, a flat chisel 44, into the clearance 33 and use it as a lever to remove the milling chisel 14 from the chisel holder 29, i.e., the quick-change chisel holder 13. The arrangement of multiple expulsion recesses 24 in the circumferential direction of the chisel shaft 20 or the chisel head 40 has the advantage that the milling chisel 14 can be installed in any rotational position (with respect to a rotation about its longitudinal axis 35) in the chisel holder 29, and an installer will still always have easy access to at least one expulsion recess 24.
[0058] Another embodiment is shown in FIGS. 8 and 9, where the tool device 11 has an anti-rotation device, which prevents the milling chisel 14 from rotating about the longitudinal axis 35. Specifically, the milling chisel 14 has two opposite projections 46 on the backside 47 of the chisel head 40, which are designed complementary to two recesses 45 provided on the ring surface 27 of the chisel holder 29 or the quick-change chisel holder 13. The two projections 46 and the recesses 45 are formed opposite each other. They are in particular arranged symmetrically with respect to the longitudinal axis 35. When the milling chisel 14 is inserted into the chisel holder 29, the projections 46 engage the recesses 45 in a form locking manner. The milling chisel 14 is therefore prevented from rotating about its longitudinal axis 35.
[0059] Moreover, the milling chisels 14 of the embodiment shown in FIGS. 8 and 9 likewise have expulsion recesses 24 in the form of slants. The expulsion recesses 24 are also designed opposite each other on the backside 47 of the chisel head 40 and are in particular arranged symmetrically with respect to the longitudinal axis 35. With regard to the circumferential direction of the backside 47 of the chisel head 40, the expulsion recesses 24 and the projections 46 alternate. In this case, the tool device 11 is designed in such a way that the milling chisel 14 can be installed in two different positions on the chisel holder 29. Specifically, the milling chisel 14 can be rotated by 180° and be installed in this position on the chisel holder 29. Due to the symmetrical design of the projections 46 and the recesses 45, as well as the expulsion recesses 24, the same installation situation is created as prior to the rotation of the milling chisel 14. This means that the anti-rotation device engages in a form locking manner, and at least one expulsion recess 24 is readily accessible and easy to reach for an installer. In this manner, the milling chisel 14 can be removed after a certain period of use and be reinstalled after rotation by 180° in order to obtain more homogenous and therefore slower wear.
[0060] Overall, the tool device 11 according to the invention provides for an extended service life of the milling chisel 14, and the milling chisel 14 and the quick-change chisel holder 13 can be installed on the base holder 12 particularly easily and quickly, so that work breaks for replacing worn milling chisels 14 or quick-change chisel holders 13 can be minimized. Also, the total number of components of the tool device 11 can be reduced, and therefore costs saved, through the use of the common fastening device 19 for fastening the milling chisel 14 and the quick-change chisel holder 13.
