The invention relates to a bit holder for an earth working machine, in particular a surface miner, a road milling machine, or the like, having a holding projection that comprises a bit receptacle and/or carries a cutting element.
The invention further relates to a carrier for a bit holder, and to a mining machine or similar earth working machine.
DE 43 224 01 A1 discloses a bit holder changing system having a base part and a bit holder. The base part comprises a support foot with which it can be welded onto the outer periphery of a milling drum. An insertion receptacle is recessed into the base part. A bit holder can be installed with its insertion projection into this receptacle. A compression screw, which pulls the insertion projection into the insertion receptacle and clamps it therein, is used to secure the bit holder in the base part. The bit holder possesses, as a bit receptacle, an orifice in which a bit, in particular a round shank bit, can be replaceably installed.
DE 10 2009 059 189 A1 discloses a further bit holder changing system that is based on a similar basic construction principle, having a base part and a bit holder. The solid embodiment shown here is usually used in surface miners. The base parts are again installed on a tubular milling drum and arranged with respect to one another so that they form helical clearing and loading screws on the milling drum surface. During processing engagement, the bits cut into the material to be removed, for example a coal seam. The bit continuously wears away as a result of the abrasive attack, with the result that its axial head length decreases. As soon as the bit has reached its wear limit, it must be replaced in order to avoid damage to the bit holder and/or to the base part. It can happen, however, that the milling machine unexpectedly encounters a hard mineral layer, whereupon a bit occasionally breaks. The bit holder is then exposed without protection to wear attack, and after only a short time is incapable of receiving a replacement bit. The bit holder must then be cost-intensively replaced. If the base part is also worn out, it too must be detached from the tubular milling drum and replaced, the expenditure of cost and time then being considerably greater.
If the wear state of the bit is not detected in timely fashion, or if a bit breakage occurs, high tool costs as well as machine down times then result. Such machine down times are, however, very cost-intensive and therefore need to be minimized.
The object of the invention is to improve the operating reliability of an earth working machine.
This object is achieved in that the holding projection of the bit holder comprises or carries, behind the cutting element or behind a receiving region of the bit receptacle in the tool advance direction, a wear protection element having a hard-material element in order to provide an emergency-mode property.
If, during operational use, the wear state of the bit is not detected in timely fashion or if a bit breaks, the wear protection element with its hard-material element takes over the emergency-mode property and prevents severe damage to the bit holder due to abrasive attack. The functionality of the bit holder is thus retained and the machine operator can quickly replace the defective bit with no need for long machine down times due to replacement of the bit holder or even of the base part.
According to a preferred inventive variant, provision can be made that the hard-material element butts against the radially externally located body region of the holding projection comprising the bit receptacle or projects radially beyond it; or that the hard-material element is arranged set back in a radial direction with respect to the cutting element. The bit holders are usually arranged on a tubular milling drum and thus proceed in a circle. During tool engagement as intended, the bit or the cutting element cuts into the material to be removed and the wear protection element with its hard-material element runs along passively with no cutting engagement. Only when the bit or cutting element has reached its wear state or when a tool break occurs does the hard-material element come into working engagement, as intended, with the substrate to be removed.
If provision is furthermore made that the hard-material element has a cutting edge, material removal can then also be accomplished with the wear protection element during emergency engagement, and furthermore the penetration resistance of the wear protection element is reduced. Excessive stress on the bit holder is thereby prevented.
An effective cutting-edge geometry results when provision is made that the cutting edge is arranged between a front side facing in the tool advance direction and a top side; and in particular that the angle enclosed between the front side and the top side for formation of the cutting edge is selected to be between 60° and 130°. An angle range between 90° and 120° is particularly preferred, since a good compromise is arrived at here for a cutting-edge geometry that is sufficiently stable and free-cutting. According to an inventive embodiment, provision can be made that the longitudinal center axis of the bit receptacle and the front side facing in the tool advance direction enclose an angle β in the angle range between 40° and 130°, particularly preferably an angle in the angle range between 60° and 110°. This yields a front-side incidence that can reliably dissipate even load peaks occurring in pulsed fashion, in order to maintain the emergency-mode function.
Provision is made particularly preferably that two or more hard-material elements juxtaposed in particular in substantially gap-free fashion are used. The use of multiple hard-material elements instead of one large continuous hard-material element decreases the risk of breakage for the hard-material element. The gap-free juxtaposition prevents erosion of the interstices between the individual hard-material elements, so that the fastening of the hard-material elements is reliably maintained.
Stable securing of the hard-material elements is achieved in simple fashion if provision is made that the hard-material element is fastened in a receptacle of the bit holder or of a carrier connectable or connected to the bit holder, and is braced positively, oppositely to the tool advance direction, against a supporting surface; and/or that the hard-material element is braced positively, in the tool advance direction, against a step.
The hard-material elements can be secured by means of a solder connection or the like. The load on this connection is relieved by the back-side bracing and/or front-side step.
Carbide, ceramic material, or another material that acts functionally identically can be used as a hard material for the hard-material element.
An inventive alternative can be such that a carrier that receives the hard-material element is replaceably connected, in particular is welded, to the bit holder. The variability of the tool system is thereby further simplified. In particular, existing bit holders can be retrofitted with a carrier of this kind. For example, if in the event of damage a bit breakage is not detected in timely fashion, the wear protection element then wears away. The complete bit holder with the carrier is then replaced and a new, unworn bit holder is inserted, so that only short machine down times result. The carrier can then be separated from the bit holder and a new, unworn carrier can be connected again to the same bit holder in order to produce a completely ready-to-use bit holder.
A particularly rigid geometry that can absorb even severe load impacts results from the fact that the carrier comprises a base part that receives the hard-material element; and that one or two supporting parts are attached, oppositely to the tool advance direction, to the base part. On the one hand large connecting surfaces can be created using the supporting parts, or alternatively the connecting geometry with the supporting parts can be designed so that large torques can be transferred.
One conceivable inventive variant is such that the carrier comprises, in the attachment region to the bit holder, a concave hollow that comprises a placement surface for attachment to a corresponding, in particular convex, enveloping surface of the bit holder. Thanks to these surface pairings, on the one hand a correctly positioned correlation of the carrier with the bit holder can be simply and quickly achieved. On the other hand, the hollowed embodiment of the carrier makes possible the creation of a positive connection in the transverse direction of the hollow.
Rapid and reliable securing of the carrier to the bit holder is enabled by the fact that the carrier is equipped on its edge regions, at least locally, with a chamfer serving as a weld bead preparation.
Also a subject of the invention is a carrier for a bit holder having a wear protection element comprising a hard-material element, the carrier comprising a placement surface by way of which it is replaceably connectable to the bit holder. To avoid repetition, reference is made to the statements above and in particular to the emergency-mode property achievable with the carrier.
A further subject of the invention is an earth working machine, in particular a mining machine or the like, that is equipped with multiple bit holders as described above. In an earth working machine of this kind, provision can be made in particular that the radially outer boundary of the hard-material element is arranged on a first reference circle having a first radius, and the radially outer boundary of the cutting element is arranged on a third reference circle having a third radius; and that the first radius of the first reference circle is smaller than the third radius of the third reference circle. This configuration ensures that the hard-material element comes into working engagement only in the event of wear or of damage to the cutting element, as has already been explained previously.
The invention will be further explained below with reference to an exemplifying embodiment depicted in the drawings, in which:
As
As
Holding projection 25 is equipped with a bit receptacle 26 in the form of a cylindrical orifice. Longitudinal center axis M of bit receptacle 26 and longitudinal axis L of insertion projection 21 ideally enclose an angle in the range between 100° and 160°, preferably 130°. Bit receptacle 26 transitions via an introduction enlargement 27 into an abutting surface 25.3. Abutting surface 25.3 extends radially with respect to bit receptacle 26. The abutting surface 25.3 may also be referred to as a forward end face 25.3 of the holding projection 25. Facing away from bit receptacle 26, abutting surface 25.3 transitions into a cross-sectional constriction 25.1. Cross-sectional constriction 25.1 is embodied in the shape of a truncated cone and transitions an enveloping surface 25.2 of the bit holder into abutting surface 25.3. Holding projection 25 comprises, in the region below bit receptacle 26, two supporting surfaces 29 that are incident to one another at a V-shaped angle. As may be gathered from
As
Hard-material elements 40 possess a top side 41 that adjoins a front side 42 in an angle range α between 60° and 150° (see
Hard-material element 40 is made of carbide, of a ceramic material, or of an equivalent hard material.
As
Attached to base part 35 oppositely to tool advance direction V are two limb-shaped supporting parts 36. The correlation with respect to base part 35 here is such that continuous lateral surfaces 39 proceeding in the direction of tool advance direction V are produced. Supporting parts 36 are bounded toward the upper side by an inclined oblique surface 36.1. In the region of the underside, carrier 30 is equipped with a concave hollow, as may be gathered from
With placement surface 37.1, carrier 30 can be placed onto a convex enveloping surface 25.2 of holding projection 25, as shown in
In the installed state, cutting edges 46 are arranged transversely to tool advance direction V. Cutting edges 46 furthermore protrude in a radial direction beyond the front-side receiving region of bit receptacle 26, as may be gathered from
The configuration of base part 10 will be further explained below with reference to
Base part 10 comprises an insertion receptacle 15 that is embodied in terms of its cross section in a manner adapted to the outer contour of insertion projection 21 of bit holder 20. Insertion receptacle 21 is bounded at the front side by means of a supporting projection 12.
A screw receptacle 13, constituting a thread, is recessed into supporting projection 12. Screw receptacle 13 opens into insertion receptacle 15. Facing away from insertion receptacle 15, screw receptacle 13 transitions into an orifice enlargement 13.1. Supporting projection 12 comprises in its upper, radially externally located region a support mount 18 that is constituted by two supporting surfaces 18.1. The two supporting surfaces 18.1 are set at an angle to one another. The angular alignment of supporting surfaces 18.1 is adapted to the alignment of supporting surfaces 29 of bit holder 20, so that supporting surfaces 29 of bit holder 20 can abut in plane-parallel fashion onto supporting surfaces 18.1 of base part 10. For purposes of defined contact of bit holder 20, supporting surfaces 18.1 are interconnected via a set-back step 18.4. Insertion receptacle 15 is bounded at the back by a countermember 16. Countermember 16 is part of a rearward projection 17 that protrudes beyond insertion receptacle 15 oppositely to the tool advance direction (V). Countermember 16 is constituted by two further supporting surfaces 16.1 that are at an angle to one another. These further supporting surfaces 16.1 are again embodied, in terms of their conformation and spatial arrangement, in a manner adapted to bearing surfaces 21.5 of bit holder 20, so that plane-parallel contact of the further bearing surfaces 21.5 against supporting surfaces 16.1 is possible. Oppositely to supporting surfaces 18.1, insertion receptacle 15 is bounded by an open surface 18.2. In the tool advance direction (V), insertion receptacle 15 is bounded by two lateral connecting segments 19. The inner surfaces that are formed by connecting segments 19 and face toward insertion receptacle 15 transition via open surfaces 18.5 into walls 18.6 that again are oriented in the tool advance direction (V). Walls 18.6 in turn transition into open surface 18.2. As is clearly evident from
Installation of bit holder 20 on base part 10 is performed as follows.
Firstly bit holder 20 is inserted with its insertion projection 21 into insertion receptacle 15 of base part 10. As may be gathered from
It may further be gathered from
Both base part 10 and bit holder 20 are embodied substantially mirror-symmetrically with respect to the transverse center plane, extending in the tool advance direction (V), of these respective components. This promotes homogeneous load dissipation.
During operational use, a round shank bit of usual design inserted into bit receptacle 26 engages into the material to be removed, for example a coal seam. It is predominantly the bracing system, made up of support mount 18 and supporting surfaces 29, that is stressed in the context of this engagement. During tool engagement, bit holder 20 is also pressed into countermember 16 as a result of the tool advance (V). The large-area contact of bit holder 20 there ensures reliable energy dissipation. As may be gathered from
During operational use, removed material is removed by the incorporated round shank bit and slides along bit holder 20 in the region of enveloping surface 25.2. This removed material is directed outward by enlargements 28, thereby providing protection of base part 10 from the abrasive attack of this removed material.
As may be gathered from
The maximum permissible wear state of cutting element 51 and of round shank bit 50 may be gathered from
When a round shank bit is worn out, it can easily be replaced. This becomes possible because cutouts 17.1 in base part 10 form, together with recess 24 in bit holder 20, a tool receptacle. Into this can be inserted a removal tool that acts on the back side of the round shank bit and pushes it out of bit receptacle 26, and also pulls a new round shank bit back in. As may be gathered from
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10 2012 101 719 | Mar 2012 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2013/051426 | 1/25/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2013/127578 | 9/6/2013 | WO | A |
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Number | Date | Country | |
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20150028654 A1 | Jan 2015 | US |