Chisel holder

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. In order to improve the operating reliability of an earth working machine, provision is made according to the present invention that the holding projection has, 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.

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.

FIG. 1shows a base part10that comprises an underside11having concavely curved placement surfaces. By means of these placement surfaces, the base part can be placed onto the cylindrical outer periphery of a milling drum and fixedly welded thereonto. A bit holder20is connected to base part10.

AsFIG. 5shows, base part10comprises an insertion receptacle15that receives an insertion projection21of bit holder20. The configuration of bit holder20will be described in further detail below with reference toFIG. 6throughFIG. 8.

AsFIG. 6shows, bit holder20comprises insertion projection21, which is adjoined in angled fashion by a holding protection25. Ideally, an oblique angle is enclosed between insertion projection21and holding projection25. Insertion projection21forms, in the region of its insertion projection front side22facing in the tool advance direction (V), a front surface21.1. Two cutouts are recessed into this front surface21.1in such a way that they form pressure surfaces21.2. Pressure surfaces21.2are arranged at an angle to the longitudinal axis of insertion projection21. The protrusion of insertion projection21which carries pressure surface21.2transitions via lateral transition segments21.3into lateral surfaces21.4. Lateral surfaces21.4are aligned in the direction of the tool advance direction (V) and face toward the tool sides. As is evident fromFIG. 7, lateral surfaces21.4transition, in the region of insertion projections23, into bearing surfaces21.5. Bearing surfaces21.5are at an angle to one another. Bearing surfaces21.5are in turn connected by means of a transition surface21.6and face oppositely to tool advance direction V.

Holding projection25is equipped with a bit receptacle26in the form of a cylindrical orifice. Longitudinal center axis M of bit receptacle26and longitudinal axis L of insertion projection21ideally enclose an angle in the range between 100° and 160°, preferably 130°. Bit receptacle26transitions via an introduction enlargement27into an abutting surface25.3. Abutting surface25.3extends radially with respect to bit receptacle26. The abutting surface25.3may also be referred to as a forward end face25.3of the holding projection25. Facing away from bit receptacle26, abutting surface25.3transitions into a cross-sectional constriction25.1. Cross-sectional constriction25.1is embodied in the shape of a truncated cone and transitions an enveloping surface25.2of the bit holder into abutting surface25.3. Holding projection25comprises, in the region below bit receptacle26, two supporting surfaces29that are incident to one another at a V-shaped angle. As may be gathered fromFIG. 8, supporting surfaces29, because of their oblique incidence, face toward the free end of the insertion projection and at the same time in the tool advance direction (V), and (as depicted inFIG. 3) extend parallel or substantially parallel to the longitudinal center axis (M) of bit receptacle26. As may be gathered fromFIG. 7, holding projection25possesses lateral enlargements28into which supporting surfaces29transition. Supporting surfaces29and bearing surfaces21.5are oriented to face in mutually opposite directions.

AsFIGS. 1 and 2show, a wear protection element, whose more detailed configuration is apparent fromFIGS. 3 and 4, is connected to holding projection25of bit holder20. As these illustrations show, the wear protection element comprises a carrier30that is fabricated from a steel material. Carrier30comprises a base part35into which a receptacle31in the form of a milled recess is incorporated. The receptacle31may also be referred to as a recess31. Receptacle31is bounded by a back-side supporting surface32and a front-side step34. A placement surface of receptacle31extends between the back-side supporting surface32and step34. Three hard-material elements40are soldered into receptacle31. Hard-material elements40are embodied as plate-shaped components that are placed with their underside44onto the placement surface of receptacle31. The placement surface of receptacle31which is engaged by the underside44of hard-material elements40as seen inFIG. 3, may be referred to as a recess bottom of the receptacle or recess31. As can be seen in bothFIGS. 3 and 4, the recess bottom slopes downwardly and forwardly toward the underside37.1of the carrier30. At the back side, hard-material elements40are braced with a back side45with respect to supporting surface32. At the front side they are braced against step34. Hard-material elements40are juxtaposed in receptacle31in gap-free fashion and are secured in receptacle31by means of an intermaterial connection, for example a solder connection or an adhesive connection.

Hard-material elements40possess a top side41that adjoins a front side42in an angle range α between 60° and 150° (seeFIG. 8). Front side42encloses with longitudinal center axis M of bit receptacle26an angle β in the angle range between 40° and 130° (seeFIG. 8). A cutting edge46is formed in the transition region between front side42and top side41. Cutting edges46of the individual hard-material elements40are flush with one another, as may be gathered fromFIG. 3. A bevel43is applied in the region at which top side41adjoins back side45in order to decrease the risk of breakage of hard-material element40.

Hard-material element40is made of carbide, of a ceramic material, or of an equivalent hard material.

AsFIG. 3further shows, the front-side step34is formed by a projection33that covers the transition region between hard-material element40and the placement surface of receptacle31toward the front side. The intermaterial connection, in particular a solder connection, is thereby protected from erosion.

Attached to base part35oppositely to tool advance direction V are two limb-shaped supporting parts36. The correlation with respect to base part35here is such that continuous lateral surfaces39proceeding in the direction of tool advance direction V are produced. Supporting parts36are bounded toward the upper side by an inclined oblique surface36.1. In the region of the underside, carrier30is equipped with a concave hollow, as may be gathered fromFIG. 4. The hollow forms a placement surface37.1that is surrounded peripherally by bevels that serve as weld bead preparations38.1to38.4.

With placement surface37.1, carrier30can be placed onto a convex enveloping surface25.2of holding projection25, as shown inFIGS. 1 and 2. In order to secure carrier30, a weld bead is introduced in the region of weld bead preparations38.1to38.4.

In the installed state, cutting edges46are arranged transversely to tool advance direction V. Cutting edges46furthermore protrude in a radial direction beyond the front-side receiving region of bit receptacle26, as may be gathered fromFIG. 6. Cutting edge46accordingly protrudes radially beyond the outer boundary of bit holder20, which in the present case is constituted by cross-sectional constriction25.1(FIG. 8).

The configuration of base part10will be further explained below with reference toFIGS. 9 and 10.

Base part10comprises an insertion receptacle15that is embodied in terms of its cross section in a manner adapted to the outer contour of insertion projection21of bit holder20. Insertion receptacle21is bounded at the front side by means of a supporting projection12.

A screw receptacle13, constituting a thread, is recessed into supporting projection12. Screw receptacle13opens into insertion receptacle15. Facing away from insertion receptacle15, screw receptacle13transitions into an orifice enlargement13.1. Supporting projection12comprises in its upper, radially externally located region a support mount18that is constituted by two supporting surfaces18.1. The two supporting surfaces18.1are set at an angle to one another. The angular alignment of supporting surfaces18.1is adapted to the alignment of supporting surfaces29of bit holder20, so that supporting surfaces29of bit holder20can abut in plane-parallel fashion onto supporting surfaces18.1of base part10. For purposes of defined contact of bit holder20, supporting surfaces18.1are interconnected via a set-back step18.4. Insertion receptacle15is bounded at the back by a countermember16. Countermember16is part of a rearward projection17that protrudes beyond insertion receptacle15oppositely to the tool advance direction (V). Countermember16is constituted by two further supporting surfaces16.1that are at an angle to one another. These further supporting surfaces16.1are again embodied, in terms of their conformation and spatial arrangement, in a manner adapted to bearing surfaces21.5of bit holder20, so that plane-parallel contact of the further bearing surfaces21.5against supporting surfaces16.1is possible. Oppositely to supporting surfaces18.1, insertion receptacle15is bounded by an open surface18.2. In the tool advance direction (V), insertion receptacle15is bounded by two lateral connecting segments19. The inner surfaces that are formed by connecting segments19and face toward insertion receptacle15transition via open surfaces18.5into walls18.6that again are oriented in the tool advance direction (V). Walls18.6in turn transition into open surface18.2. As is clearly evident fromFIG. 9, a cutout17.1is countersunk into projection17.

Installation of bit holder20on base part10is performed as follows.

Firstly bit holder20is inserted with its insertion projection21into insertion receptacle15of base part10. As may be gathered fromFIG. 5, a setscrew constituting fastening element14is then screwed into screw receptacle13. Fastening element14comprises a pressure application surface, oriented at right angles to the screw axis, that comes into contact against pressure surface21.2of bit holder20. The pressure application surface does not need to be a planar surface, but can also be a spherical surface. It may be gathered fromFIG. 1that two fastening elements14are used to fasten bit holder20, and therefore two screw receptacles13are also recessed into base part10. Upon tightening of fastening elements14, fastening element14presses onto pressure surface21.2. Because of the angled incidence of pressure surface21.2with respect to longitudinal center axis L of insertion protection21, fastening element14exerts a pull-in force on insertion projection21. Simultaneously, a force component is generated which extends oppositely to the tool advance direction (V) and presses insertion projection21into countermember16. The force component extending in the direction of longitudinal axis L of insertion projection21brings supporting surfaces18.1of support mount18into contact with supporting surfaces29of bit holder20. As is clearly apparent in particular fromFIG. 5, tightening of fastening elements14causes bit holder20to experience bracing on both sides of longitudinal center axis L of insertion projection21. Bracing is performed on the one hand against countermember16on the back side of the longitudinal center axis at the insertion-projection end of bit holder20, and on the other hand against support mount18on the front side of the longitudinal center axis at the holding-projection end of the bit holder. Support surfaces29and bearing surfaces21.5are consequently located diametrically oppositely on bit holder20. Fastening screw14then acts on insertion projection21in such a way that a tightening of bit holder20against support mount18and against countermember16takes place. Secure and lossproof fastening of bit holder20is thereby guaranteed.

It may further be gathered fromFIG. 5that a cover element14.1, which covers the tool receptacle of fastening element14, can be inserted into orifice enlargement13.1of screw receptacle13.

Both base part10and bit holder20are 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 receptacle26engages into the material to be removed, for example a coal seam. It is predominantly the bracing system, made up of support mount18and supporting surfaces29, that is stressed in the context of this engagement. During tool engagement, bit holder20is also pressed into countermember16as a result of the tool advance (V). The large-area contact of bit holder20there ensures reliable energy dissipation. As may be gathered fromFIG. 5, an unequivocal correlation between bit holder20and base part10is guaranteed in particular by the fact that contact takes place only at these two aforementioned central supporting points (support mount18and countermember16). In the region of setback18.4, open surface18.2, walls18.6of open surfaces18.5, and connecting segment19, insertion projection21is clear of insertion receptacle15. When, for example, wear on supporting surfaces18.1takes place in the course of utilization of base part10, setback18.4then forms a resetting space. The spacing of bit holder20away from setback18.4ensures resetting of bit holder20in the event of wear. Wear compensation can take place in particular because supporting surfaces18.1and further supporting surfaces16.1form slide guides along which bit holder20can slip upon re-tensioning. This configuration is advantageous in particular when, as is usually required, base part10has a service life that lasts through several life cycles of bit holders20. Unworn bit holders20can then always be reliably secured and held even on a partly worn base part10.

During operational use, removed material is removed by the incorporated round shank bit and slides along bit holder20in the region of enveloping surface25.2. This removed material is directed outward by enlargements28, thereby providing protection of base part10from the abrasive attack of this removed material.

FIGS. 11 and 12show the installed correlation between bit holder20and base part10. Base part10is placed with its concave underside11onto the convex outer side of a tubular milling drum and welded in place there. A shank bit, namely a round shank bit50, is inserted in known fashion into bit receptacle26of bit holder20. Round shank bit50comprises a bit tip51, made of hard material, that is fastened on a bit head52. Adjoining bit head52is a bit shank that is held in bit receptacle26by means of a clamping sleeve (not shown in the Figures). By means of the clamping sleeve, round shank bit50can be held in bit receptacle26in lossproof fashion in an axial direction, but freely rotatably around its longitudinal center axis M. Bit head52is braced with respect to abutting surface25.3with interposition of a wear protection washer53. FIG.11shows round shank bit50in the unworn state. During operational use, the tool combination shown rotates around the longitudinal center axis of the tubular milling drum, in which context the cutting insert rotates with its radially outer dimensional boundary on a reference circle T3having a third diameter. The radially outer boundary of cutting edges46rotates on a reference circle T2having a second radius. Reference circle T1shown inFIGS. 11 and 12, having a first radius, represents the maximum permissible wear state of hard-material elements40.

As may be gathered fromFIG. 11, cutting edges46are arranged set back in a radial direction with respect to reference circle T3, so that the second radius of reference circle T2is smaller than the third radius of reference circle T3.

The maximum permissible wear state of cutting element51and of round shank bit50may be gathered fromFIG. 12. As this drawing illustrates, the radially outer boundary of cutting element51is now located on reference circle T2, so that cutting elements46are now also coming into engagement with the material to be removed. Hard-material elements40thus constitute an emergency-mode property which prevents the front receiving region of the bit receptacle (abutment25.3) from becoming worn or damaged.

FIGS. 13 and 14further illustrate the operating states shown inFIGS. 11 and 12. AsFIGS. 13 and 14show, a plurality of tool systems, each made up of a base part10, a bit holder20, and a round shank bit50, are fastened on the cylindrical surface61of a tubular milling drum60. For clarity, only some of the tool systems are depicted. It is nevertheless clear to one skilled in the art that a plurality of tool systems are mounted over the entire peripheral surface of tubular milling drum60, distributed in a helical correlation, in order to form clearing and loading screws.FIG. 13shows the unworn state of round shank bits50, illustrating that only cutting elements51and not hard-material elements40are in engagement with that seam F of ground B which is to be processed.

FIG. 14shows the state of round shank bits50when the wear limit is reached. As the drawing shows, hard-material elements40are now coming into engagement with seam F.

When a round shank bit is worn out, it can easily be replaced. This becomes possible because cutouts17.1in base part10form, together with recess24in bit holder20, 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 receptacle26, and also pulls a new round shank bit back in. As may be gathered fromFIG. 5, bit receptacle26is physically connected to recess24.