The present invention relates to a mixer bar for a stabilizer/recycler, having an attachment side that comprises an attachment surface for mounting on a drum surface, and having a tool holder receptacle.
Stabilizers are construction machines that are used to consolidate a more or less loose substrate. Consolidation serves in this context as preparation for a structure that is to be built, for example a road or a building. Recyclers, on the other hand, are used when the task involves regenerating an existing dilapidated traffic surface. The core element of a stabilizer/recycler is a mixer drum. This is made up of a milling drum rotor on whose drum surface mixer bars are mounted (usually welded) in distributed fashion. The mixer bars carry a tool holder receptacle spaced away from the drum surface. Either a tool holder or a quick change tool holder system having a tool is inserted into said receptacle. During operational use, the tool penetrates into the dirt being processed, and cuts it up. The mixer bar digs into the cut-up dirt and thus contributes to loosening. A binder is introduced into the loosened dirt and serves to consolidate it. This binder is mixed with the cut-up dirt as a result of the mixer bars and their systematic arrangement on the drum surface, in conjunction with the rotation of the milling drum.
The mixer bars are produced as flame-cut parts, the desired contour of the mixer bar being cut out of a metal sheet using a cutting torch.
In order to minimize the necessary machine power output, the mixer bars are embodied to be relatively narrow. They nevertheless present considerable penetration resistance. In addition, the mixer bars become worn as a result of the material flowing past. Once they have reached their wear limit, they must be removed from the drum surface and replaced with a new mixer bar.
It is an object of the invention to create a mixer bar of the kind mentioned above that makes possible an efficiency-optimized design along with ease of manufacture.
This object of the invention is achieved in that the mixer bar is embodied as a forged part and has a cross-sectional profile that varies at least locally transversely to the tool feed direction. By way of the varying cross-sectional profile, it is possible to generate a shape that achieves low levels of penetration resistance into the dirt. The shape of the mixer bar can, in this context, be designed in a manner adapted to the flow of the material being detached, thereby decreasing wear and at the same time improving the mixing result. In addition, by way of the varying cross-sectional profiles it is possible to embody protective zones that, for example, protect a tool holder or a quick-change tool holder system from the abrasive attack of the detached material. Simple production of the mixer part is furthermore achieved, since it is embodied as a forged part. The varying cross-sectional profiles can be achieved here without additional mechanical processing. In addition, forged parts offer the possibility of using material having excellent strength and toughness properties, and are therefore ideally suited for the present application.
According to a preferred variant embodiment of the invention, provision is made that the attachment side comprises a divided or continuous mounting surface that transitions at least locally, via a recess or bevel serving as a weld-bead preparation, into lateral surfaces that are at an angle to the mounting surface. The weld-bead preparations can already be shaped upon production of the forged part, so that no additional mechanical processing is necessary here. Upon installation of the mixer bar on the drum surface, the weld-bead preparation can be filled with additional weld material.
A mixer bar according to the present invention can be such that the mounting surface comprises, on the oppositely located mixer bar sides, mounting edges that each extend in the tool feed direction and each taper, at their front and/or rear ends, into end segments extending at an angle to the tool feed direction. These mounting edges can once again easily be implemented on the forged part. They have the advantage that energy transfer from the mixer bar into the drum surface is optimized, since large discontinuities in stiffness are avoided and the weld beads do not extend parallel to the grain of the milling drum rotor. The risk of damage to the milling drum rotor in a context of severe stress on the mixer bar is thereby minimized. This effect can be achieved in particularly simple fashion if provision is made that the end segments of the mounting edges form arrow-shaped tapers. In particular, the mounting edges can be incident so that a symmetry is produced and so that symmetrical loading values can thus also be achieved.
According to a further variant of the invention, provision can be made that there is arranged on the front side of the bar a mixer segment that is delimited laterally by two flank surfaces arranged at an angle to one another, the flank surfaces being incident to each other in an arrow shape. This kind of configuration of the mixer segment can likewise be implemented in simple fashion on the forged part.
With the laterally incident flank surfaces, the penetration resistance of the mixer bar into the substrate being processed is greatly reduced. This results in a decrease in the required motor drive power output of the stabilizer/recycler, and thus in greater efficiency. If the flank surfaces are embodied asymmetrically, the mixing result can moreover be improved.
A mixer bar according to the present invention can be characterized in that a protrusion is arranged in front of the tool holder receptacle in the tool feed direction. This protrusion protects the quick-change tool holder system or tool holder located behind it from the abrasive attack of the detached material. In particular, the protrusion can also be adapted, in terms of its width extending transversely to the tool feed direction, to the shape of the tool holder or quick-change tool holder system located behind it. The protrusion can likewise be delimited by two flank surfaces that decrease the penetration resistance of the mixer bar. In particular, the flank surfaces of the protrusion can also be constituted by the flank surfaces of the mixer segment, thus producing a continuous geometry that promotes the flow of material.
If provision is made that the tool holder receptacle is delimited, oppositely to the tool feed direction, by a supporting projection, this then results in a stable positive support, rigid oppositely to the tool feed direction, for the tool holder or quick-change tool holder system arranged in the holder receptacle.
In order to achieve a high level of dimensional stability in the tool holder receptacle, provision can be made that the protrusion and the supporting projection are connected to one another by means of a connecting segment. The connecting segment ensures positional association of the protrusion with respect to the supporting projection, in particular as the forged part cools during production.
Weight optimization of the mixer bar can be achieved in simple fashion by the fact that the connecting segment is constricted in its cross-sectional geometry with recesses and/or that an aperture or at least one hollow-shaped depression is introduced into the mixer bar in the region between the tool holder receptacle and the mounting surface. These reductions in material serve to decrease inertia and thus to reduce the required drive power output of the drive unit.
If provision is made that two shaped surfaces extend on the oppositely located mixer bar sides from the tool holder receptacle toward the front side of the mixer bar and at an angle to the tool feed direction, a geometry promoting the flow of material is then created. The shaped surfaces, in particular, prevent eroded areas from forming.
Another subject of the invention is a mixer bar having a tool holder that comprises a tool receptacle and is connected to the mixer bar. Provision can be made in particular, in this context, that the tool holder is made up of a lower part and an upper part, the lower part being connected to the mixer bar, and the upper part being connected replaceably to the lower part. The lower part can, in particular, be welded to the mixer bar. The upper part and lower part can be held with respect to one another by way of a screw connection. Positively and/or frictionally engaged connections are also conceivable. The upper part comprises a tool receptacle for replaceable reception of a tool, for example a shank bit, in particular a round shank bit. It is nevertheless apparent to one skilled in the art that the invention is not limited to the use of specific tool holders and tools. All imaginable tool holder and tools can instead be utilized. A wear system is thereby created. In this context, the tool has the shortest lifetime and can easily be replaced once the wear limit is reached. The upper part has a service life corresponding to several times that of a tool. It, too, can easily be changed once its wear limit is reached.
The upper part serves, in combination with the mixer bar, to protect the lower part, which is relatively costly to produce and therefore has the longest lifetime of the quick-change tool holder system. Optimally, the lifetime of the lower part is adapted to the lifetime of the mixer bar, so that this component unit can be replaced together once the wear limit is reached.
The invention will be further explained below with reference to an exemplifying embodiment depicted in the drawings, in which:
As may be seen clearly especially from
When reference is made herein to a cross-sectional profile transverse to the tool feed direction, that is a reference to the width or thickness of the mixer bar across its narrower dimension. For example, referring to
Mixer segment 15 comprises a protrusion 16 that is arranged in front of a tool holder receptacle 22 in tool feed direction V. Flank surfaces 15.1 extend continuously over protrusion 16 so that a continuous cutting edge 15.2 and continuous flank surfaces 15.1 are obtained. Protrusion 16 may be referred to as a cutting protrusion. Shaped surface 16.1 transitions in the lower region of mixer segment 15, by means of transition segments 16.2, into lateral surfaces 13.1, 17.1 of mixer bar 10. In the region of protrusion 16, shaped surfaces 16.1 are transitioned into tool receptacle 22.
The rear-side protrusion 17 transitions via a radius transition 18 into a rearward supporting protection 19. Supporting projection 19 delimits tool receptacle 22 at the rear side. Supporting projection 19 is delimited laterally be two mutually parallel cheekpieces 19.1. Tool receptacle 22 is thus embodied between protrusion 16 and supporting projection 19.
Tool receptacle 22 is delimited toward the bottom by means of a connecting segment 21. Connecting segment 21 connects supporting projection 19 to mixer segment 15 and/or to protrusion 16. Connecting segment 21 forms a seating surface 21.3 that extends substantially in tool feed direction V. Hollow-shaped recesses 21.2 are recessed into said seating surface 21.3. In addition, recesses 21.1 are also cut out of the lateral surfaces of connecting segment 21 that perpendicularly adjoin seating surface 21.3. These recesses 21.1. and 21.2 serve for weight reduction. Connecting segment 21 stiffens supporting projection 19 with respect to protrusion 16 so that the dimensional stability of these two components with respect to one another is guaranteed with no need for mechanical post-processing.
An aperture 20 that serves for weight reduction is introduced below connecting segment 21 and above mounting surface 11, in the intermediate region of mixer bar 10. Instead of aperture 20, it is also possible to provide recesses on both sides of the forged part, a thin wall of mixer bar 10 then remaining instead of aperture 20. A configuration of this kind prevents detached fragments, for example larger stones, from becoming wedged into aperture 20 and possibly limiting functionality.
A monolithic tool holder having a tool holder 43 for replaceable reception of a tool, in particular a round shank bit, can be welded into tool holder receptacle 22. What is used in the present exemplifying embodiment as a tool holder is not a monolithic but instead a two-part quick-change tool holder system. This tool holder is made up of a lower part 30 and an upper part 40. Lower part 30 can be inserted into tool holder receptacle 22 in such a way that front- and rear-side attachment surfaces 38 are associated with protrusion 16 and with rear-side supporting projection 19, respectively. At the same time, lower part 30 sits with a bottom surface 35 on seating surface 21.3 of connecting segment 21. The association between lower part 30 and mixer bar 10 is more clearly evident from
Lower part 30 comprises a contact surface 31 that transitions in angular fashion into a setback 32. Lower part 30 is prepared for reception of upper part 40. It comprises an insertion receptacle into which an insertion extension of upper part 40 can be inserted. This insertion extension can be secured with a clamping screw threaded into lower part 30, upper part 40 being pulled with a mating surface onto contact surface 31 and immobilized there. In the installed state, setback 32 is at a distance from an oppositely located surface of upper part 40 so that a resetting space 33 is formed. This resetting space 33 is spanned by a seal 34 made of elastic material. Seal 34 prevents penetration of detached material into the region between upper part 40 and lower part 30. Upper part 40 is equipped with a tool receptacle 43 embodied as an orifice, as is clearly evident from
As may be gathered from
Number | Date | Country | Kind |
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10 2010 038 016.4 | Oct 2010 | DE | national |