Abstract
The present invention relates to a chisel device for a ground milling machine, comprising a chisel holder having a mounting orifice and a milling chisel, wherein the milling chisel has a basic body of, in particular, a uniform material and has a shaft and a tool region, said shaft being held, under working conditions, in the mounting orifice while the tool region (P) protrudes, under working conditions, from the chisel holder, wherein said milling chisel has a wear protection cap consisting of carbide and having a tip and a protective jacket, wherein the wear protection cap is positioned on the tool region (P) in such a manner that it covers at least 70% of the external surface of the tool region (P). The present invention also relates to a milling chisel for such a chisel device.
Claims
1. A chisel device for a ground milling machine, comprising: a chisel holder having a mounting orifice; and a milling chisel having a basic body of a uniform material and including a shaft and a tool region (P), which shaft is under working conditions held in said mounting orifice while said tool region (P) protrudes under working conditions from said chisel holder, wherein said milling chisel has a wear protection cap comprising carbide, said wear protection cap comprising a single piece and having a tip forming a foremost point of said milling chisel and a protective jacket, said wear protection cap being formed in such a manner that said wear protection cap covers at least 70% of the external surface of said tool region (P) of said basic body, wherein said wear protection cap has a profile on its outer surface comprising a plurality of slots which extend in an at least partially spiral pattern from said tip of said wear protection cap to a peripheral region of said protective jacket facing away from said tip, each of said plurality of slots extending entirely through a thickness of said wear protection cap, and wherein an elevated region is arranged in direct adjacency of each of said slots.
2. The chisel device according to claim 1, wherein said wear protection cap of said milling chisel is positioned on said tool region (P) of said basic body in such a manner that said wear protection cap covers the external surface of said tool region (P) of said basic body to an extent of at least 80%.
3. The chisel device according to claim 1, wherein said milling chisel includes a contact ledge for the purpose of said milling chisel making contact with said chisel holder, and said wear protection cap of said milling chisel terminates by way of a collar in a direction of advance (b) of the tool in advance of said contact ledge or flush therewith.
4. The chisel device according to claim 1, wherein said wear protection cap of said milling chisel is provided with a greater wall thickness (h) in regions exposed to stronger stress under working conditions than in regions that are exposed to weaker stress under working conditions.
5. The chisel device according to claim 1, wherein said wear protection cap of said milling chisel includes the tip having a greater wall thickness (h) than said protective jacket.
6. The chisel device according to claim 1, wherein said wear protection cap of said milling chisel comprises a plurality of jacket layers.
7. A milling chisel for a chisel device according to claim 1.
8. The chisel device according to claim 1, wherein said wear protection cap of said milling chisel is positioned on said tool region (P) of said basic body in such a manner that said wear protection cap covers the external surface of said tool region (P) of said basic body to an extent of at least 90%.
9. The chisel device according to claim 1, wherein said wear protection cap of said milling chisel is positioned on said tool region (P) of said basic body in such a manner that said wear protection cap covers the external surface of said tool region (P) of said basic body to an extent of substantially completely.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is a side view of a generic ground milling machine,
(2) FIG. 2 is a side view of a generic chisel device,
(3) FIG. 3 is a side view of a generic milling chisel,
(4) FIG. 4 shows two cross-sectional views of milling chisels according to a first embodiment,
(5) FIG. 5 shows two cross-sectional views of milling chisels according to a second embodiment,
(6) FIG. 6 shows two cross-sectional views of milling chisels according to a third embodiment,
(7) FIG. 7 is a cross-sectional view of a wear protection cap shown in FIG. 5,
(8) FIG. 8 is a side view of a milling chisel according to a closed embodiment,
(9) FIG. 9 is a side view of a milling chisel according to an embodiment comprising webs,
(10) FIG. 10 is a side view of a milling chisel according to a multi-piece embodiment,
(11) FIG. 11 is a side view of a milling chisel according to a multi-piece overlap-type embodiment,
(12) FIG. 12 shows a side view and a front view of a wear protection cap comprising linear profiling,
(13) FIG. 13 shows a side view and a front view of a wear protection cap comprising wavy profiling,
(14) FIG. 14 shows a side view and a front view of a wear protection cap comprising jagged profiling,
(15) FIG. 15 shows a side view and a front view of a wear protection cap comprising spiral profiling,
(16) FIG. 16 shows a side view and a front view of a wear protection cap comprising profiling formed by slots and elevated regions, and
(17) FIG. 17 shows a cross-sectional detailed view of the protective jacket of the wear protection cap with profiling formed by slots and elevated regions shown in FIG. 16.
(18) Like or functionally identical components are identified in the figures by the same reference numerals. Repeated components are not individually denoted in every figure.
DETAILED DESCRIPTION OF THE INVENTION
(19) FIG. 1 illustrates a generic ground milling machine 1, in this case a road miller or, more particularly, a cold miller of the central drum type in which the chisel devices described in more detail below are used. Said ground milling machine comprises an operator's platform 2, a machine frame 3, a driving engine 4, and crawler tracks 6. During operation of the ground milling machine 1 the ground 8 is depleted in the direction of advance a by means of a milling drum 9 rotatably mounted about the axis of rotation 10 within the milling drum box 7. The milled material is dispatched via the discharge conveyor 5.
(20) A plurality of chisel devices 37 is mounted on the hollow cylindrical supporting tube of the milling drum 9, one of which is shown by way of example in FIG. 2. The chisel devices 37 comprise a chisel holder 38 and a milling chisel 11 held in the mounting orifice 39 by means of its shaft 16 (FIG. 3; indicated by dashed lines in FIG. 2). The tool region P protrudes from the chisel holder 38. The tool region is driven into the ground 8, for the sake of simplicity in the direction of advance b of the tool, by way of rotation of the milling drum 9 about the axis of rotation 10 during operation of the ground milling machine 1 for the purpose of milling the ground. The chisel holder 38 is, in the present example, composed of a quick-change tool holder 34 and a basic holder 35, the quick-change tool holder 34, being attached to the basic holder 35, which is in turn fixed to the milling drum 9.
(21) FIG. 3 shows in detail a milling chisel 11 of the prior art. The milling chisel 11 is divided into a tool region P disposed at the front as regarded in the direction of advance b of the tool, and into a holder region Q disposed at the rear as regarded in the direction of advance b of the tool. During operation of the ground milling machine 1, the tool region P makes direct contact with the milled material whilst the holder region Q is in the mounted condition exclusively disposed within the mounting orifice 39 and hence concealed from external view by the chisel holder 38. The milling chisel 11 furthermore comprises a carbide tip 12 soldered to the basic body 17 of the milling chisel 11. The carbide tip 12 is connected to a sleeve 13 surrounding the basic body 17 of the milling chisel 11. An indentation 14 and a wear plate 15 enabling contact between the milling chisel 11 and the chisel holder 38 connect further towards the rear as regarded in the direction of advance b of the tool. In the case of this prior art embodiment, so-called “erosion” of the sleeve and subsequently of the basic body 17 in the tool region P frequently occurs. A consequence of this is a break-off of the carbide tip 12 prior to the end of its lifespan, and an exchange of the milling chisel 11 and, thus, wastage of the remaining lifespan of the carbide tip 12 are inevitable.
(22) FIGS. 4, 5, and 6 show cross-sectional views of milling chisels 11 according to one embodiment of the present invention comprising wear protection caps 19. In each case the cross-sectional view runs along the longitudinal axis 20. The wear protection caps 19 are attached to the head 18 of the milling chisel 11 in the tool region P and are fixed thereto, for example, by braze welding, clipping, gluing, or welding. The milling chisels 11, in particular, inclusive of the wear protection caps 19, can be arranged rotationally symmetrically about the symmetry axis 20. In the case of a non-rotationally symmetrical design, the reference numeral 20 defines the longitudinal axis of the milling chisel 11.
(23) The wear protection caps 19 are uniformly made of carbide and comprise a tip 31 and a protective jacket 32 extending radially about the symmetry axis 20 contrary to the tool direction b. The tip 31 of the milling chisel 11 can be either tapered or rounded. The wear protection cap 19 comprises, and ends at, a collar 33 and extends across the major part of the tool region P up to a point situated just before the contact ledge 15 and, thus, protects the basic body 17, in particular, the head 18, of the milling chisel 11 from wear caused by the milling operation. It is essential in this case that the wear protection cap is basically formed such that it conceals only the area of the tool region P and does thus not extend beyond the shaft or the holder region Q.
(24) The exemplary embodiments shown in FIG. 4 show wear protection caps 19 having a uniform wall thickness h. FIG. 7 illustrates the manner in which the wall thickness h is determined. The wall thickness h describes the shortest distance between the outer surface of the wear protection cap 19 and the inner surface of the wear protection cap 19 at a respective measuring point. The wear protection cap 19 shown in FIG. 7 thus has a wall thickness h at the tip 31 and a wall thickness h′ at the protective jacket 32. In this respect the wall thickness h is always typically determined at right angles to the outer surface of the wear protection cap 19. The wear protection caps 19 in FIG. 4 are therefore consistently of the same thickness. Differences in the two exemplary embodiments shown in FIG. 4 thus reside in the individual geometrical designs of the tool region P. On the left-hand side, this is in the form of a pointed cone having straight sides and on the right-hand side in the form of a rounded cone having elliptically curved sides. The two design variants are, however, equivalent to each other in their basic construction, so that the reference numerals referring to the right-hand exemplary embodiment also apply to the left-hand embodiment.
(25) FIG. 5 shows two alternative embodiments. The essential difference from the exemplary embodiments of FIG. 4 lies in the fact that the tip 31 of the wear protection cap 19 has a greater wall thickness h than the protective jacket 32. Such thickening of the wear protection cap 19 refers to a region of the tip 31 that extends contrary to the direction of advance b of the tool from the foremost point of the milling chisel 11 as regarded in the direction of advance b of the tool. The wall thickness h of the wear protection cap 19 increases in this region in the direction of advance b of the tool up to the point of intersection of the longitudinal axis 20. The sleeve region 32, however, has a consistent wall thickness. In general, there is obtained a solid tip 31 made of carbide that withstands maximum stress during milling and that shows greater resistance to said stress due to its increased wall thickness h. Said tip thus contributes to extension of the lifetime of the milling chisel 11. At the same time, the core 17 is effectively protected at its sides in the tool region P against the flow of milled material by means of the protective jacket 32. For the purpose of accommodating for said thickened region of the wear protection cap 19, the core 17 has a plateau-like flattened tip region. The reference numerals used for the left-hand embodiment also apply to the right-hand embodiment.
(26) FIG. 6 shows two exemplary embodiments of the milling chisel 11 of the present invention having wear protection caps 19 consisting of multiple jacket layers 21, 22. The jacket layers 21, 22 may each consist of the same material, for example, a carbide, or of two different carbides. It is, however, also possible, for example, to form the outer jacket layer 21 of carbide and the secondary jacket layer 22 of a softer, preferably flexible, material for the purpose of combining their positive material properties. The jacket layers 21, 22 can also be joined together by means of clips or by soldering, welding, or gluing. Again, the differences between the two embodiments reside in the pointed-cone shape (on the left) and the rounded-cone shape (on the right) of the tip region of the milling chisel 11. Here again, the reference numerals of the right-hand exemplary embodiment equally apply to the left-hand exemplary embodiment.
(27) The FIGS. 8, 9, 10, and 11 illustrate further details of the embodiment of the wear protection cap 19.
(28) The embodiment in FIG. 8 features a wear protection cap 19 of an uninterrupted single-piece of solid design including a thickened tip 31. Its protective jacket 32 extends to the collar 33 to a point just anterior of the contact ledge 15. The tool region P is concealed almost entirely by the wear protection cap 19 and protected from wear. That part of the head 18 of the basic body 17 of the milling chisel 11 that forms the contact ledge 15 is radially inwardly offset as regarded from the direction of the symmetry axis 20. The contact ledge 15 and that part of the head 18 that forms it lie in the slipstream of the wear protection cap 19 as regarded in the direction of advance b of the tool, said contact ledge being therefore also protected from excessive wear caused by the milled material.
(29) The embodiment of the wear protection cap 19 shown in FIG. 9 embodies a number of finger-shaped or tongue-shaped webs 29 extending in the direction of advance b of the tool and protruding from the wear protection cap 19 contrary to the direction of advance b of the tool. An amount of material of the wear protection cap 19 is missing between the webs 29, such that the webs 29 are separated from each other by means of recesses 30. Nonetheless, the webs 29 also provide protection for the regions of the head 18 of the milling chisel 11 lying beneath the recesses 30 during operation. The milled material is guided along the head 18 of the milling chisel 11 by means of the uninterrupted part of the wear protection cap 19 situated toward the front as regarded in the direction of advance b of the tool and the webs 29 in such a manner that the wear on the head 18 progresses only marginally faster in the regions of the recesses 30 than in the regions lying beneath the webs 29. In return, material is saved due to the recesses 30, which on the whole reduces the production costs of the wear protection cap 19.
(30) The embodiment shown in FIG. 10 also requires less material and can thus be produced in an inexpensive manner. In this case the wear protection cap 19 is of a multi-piece design and comprises three wear protection rings 23, 24, and 25 set at a distance from one another. A greater or smaller number of wear protection rings may of course be used if desired. The wear protection ring 23 is attached to the milling chisel 11 as described above in the case of the single-piece wear protection caps 19. The wear protection rings 24 and 25 positioned further towards the rear of the tool region P as regarded in the direction of advance b of the tool can either be fixed thereto or lie loosely thereon. In the latter case they are made in such a manner that slippage thereof from the milling chisel 11 in the direction of advance b of the tool is impossible. This is ensured, for example, by the fact that the inner diameter of the wear protection ring 24, 25 positioned further towards the rear in the direction of advance b of the tool is smaller than the outside diameter of the wear protection ring 23, 24 respectively positioned further towards the front as regarded in the direction of advance b of the tool. Additionally, the production of the wear protection cap 19 in FIG. 10 can be simplified by being manufactured as a single-piece component despite its multi-piece design. In this case, the wear protection rings 23, 24, 25 are attached to each other at the time of production. Predetermined breaking points 28 are provided between them, allowing for precise separation of the wear protection rings 23, 24, 25 either during production or, particularly, in the case of the wear protection rings 24, 25 lying loosely on the milling chisel 11, during operation due to the stresses caused by the milled material. As described above with respect to the webs 29, the wear protection rings 23, 24, 25 also protect the regions of the head 18 of the milling chisel 11 lying therebetween and not covered thereby, by means of advantageous guidance of the milled material.
(31) The method of manufacture in the form of a single-piece component having predetermined breaking points can also be applied in the case of the multi-piece embodiment of the wear protection cap 19 shown in FIG. 11. In this case the wear protection cap 19 consists of four wear protection rings 23, 24, 25, 26 although this number can again be lower or higher. Unlike the embodiment shown in FIG. 10, the wear protection rings 23, 24, 25, 26 are, however, not set at such a distance from one another that regions of the head 18 of the milling chisel 11 are formed therebetween that are not concealed from the outside by the wear protection cap 19. Instead, virtually the entire tool region P is again concealed by the wear protection cap 19, similar to the single-piece embodiment of FIG. 8. The wear protection rings 24, 25, 26 are made such that they have an overlap edge 27 overlapped by the wear protection ring 23, 24, 25 respectively situated further towards the front as regarded in the direction of advance b of the tool. In other words, the overlap edge 27 of a wear protection ring 24, 25, 26 always lies below a wear protection ring 23, 24, 25 situated further towards the front as regarded in the direction of advance b of the tool. Such overlapping ensures that during operation the head 18 of the milling chisel 11 is always superficially concealed from the environment by the wear protection cap 19 across the entire extent thereof. For the purpose of reinforcing this effect, the wear protection rings 23, 24, 25, 26 interlock, for example, positively. As described above in relation to the embodiment shown in FIG. 10, the wear protection ring 23 is fixed to the head 18 of the milling chisel 11 whilst the wear protection rings 24, 25, 26 can be either attached or laid loosely on top.
(32) FIGS. 12, 13, 14, 15 and 16 show wear protection caps 19 provided with profiling 36. In the examples shown, the profiling 36 is in the form of slotted recesses, the example shown in FIG. 16 comprising a profiling formed by slots 40 and elevated regions 41. The patterns 36 can be linear (FIG. 12), wavy (FIG. 13), zig-zag (FIG. 14), or spiral (FIG. 15, at least partially also in FIG. 16). Such patterns serve to guide the milled material along the wear protection cap 19 and help maintain a relief structure, by means of which, for example, a flexible conduct of the wear protection cap can be preserved to the desired extent. Due to the passage of the milled material thereover, the patterns can further serve to convey a drive torque to the milling chisel 11 to cause it to rotate about its symmetry axis 20 during operation. Such rotation can result in the milling chisel 11 being worn evenly on all sides such that its maximum lifespan can be fully exploited. This effect is particularly strong in the exemplary embodiment shown in FIG. 16. The profiling 36 shown in FIG. 16 is further illustrated by the cross-sectional view in FIG. 17. The elevated region 41 provides for particularly efficient guidance of the milled material along the protective jacket 32 in a predetermined direction. Due to the elevated region 41, the milled material is dispatched in the direction of arrow c essentially transversely to the direction of advance b of the tool. As a result of the slightly spiral-shaped progression of the profiling 36 comprising slots 40 and elevated regions 41, the rotation of the milling chisel is supported in a particularly efficient manner. The slots 40 are located behind the elevated regions 41 as regarded in the direction of arrow c. The slots 40 and the elevated regions 41 run parallel to each other and are of essentially equal length. In particular, an elevated region 41 will be adjoining the slots 40 over their entire length. The milled material is guided along the elevated regions 41 away from the wear protection cap 19, and, in particular, the slots 40, which also results in reduced wear of the slots 40.
(33) The wear protection caps 19 can be fixed to the head of the basic body, for example, by way of braze welding, welding, or gluing.
(34) While the present invention has been illustrated by description of various embodiments and while those embodiments have been described in considerable detail, it is not the intention of Applicants to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will readily appear to those skilled in the art. The present invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicants' invention.
