Due to different construction site situations and milling works, it is often necessary to adapt the milling tool of a road milling machine to the specific tasks. If, for example, a specific surface roughness shall be achieved, a milling roll with a specific track distance of the milling tools or another tool equipment is required. In another application, only certain roadway widths shall be completed so that a milling roll with a specific working width is required.
Typically, a special milling machine has to be used in such situations or the machine has to be fitted with a milling roll adapted to the task. At present, however, exchanging the milling rolls is very troublesome and requires special auxiliaries for respectively mounting and dismounting the milling roll.
In prior art, it is known to adapt the milling tool to different requirements.
In U.S. Pat. No. 4,704,045, a milling aggregate is described the width of which can be varied by using different roll segments. In this solution, the roll segments are connected with each other via a plug-in connection. Although, in a certain way, this type represents a milling roll quick change system, it has the following disadvantages:
This solution is disadvantageous in that the milling roll drive is effected hydrostatically by arranging hydraulic motors at both sides of the milling roll. Moreover, the connection between the segments is a simple plug-in connection that only permits an insufficient centering of the milling rotor. Because a drive device is provided at both sides, it is not possible to mill near the edges. Moreover, a roll housing of variable width is required the construction of which is very complicated.
U.S. Pat. No. 4,720,207 describes milling tube segments mounted on a roll base body. In this concept, a side ring segment is attached at one side first. Then, the milling tube segments are screwed down thereon, the screw connections being located within the segments. The enormous screwing efforts and the fact that the milling depth is restricted because of the constant diameter of the base body when a planet gear is integrated in the base body are disadvantageous.
U.S. Pat. No. 5,505,598 describes another solution where, above all, the milling depth is not restricted. The reduction gear unit of this milling roll is located on the side opposite to the driven pulley and is driven by a drive shaft led through the milling roll axis.
This gear arrangement with a gear unit the outer diameter of which is only slightly smaller than that of the milling tube is required to permit a flush milling. From the section of the milling roll in which the reduction gear unit is integrated, an axle stub projects on which further segments with milling tools can be mounted.
This solution is disadvantageous in that the milling roll has to be completely dismounted to carry out different milling operations such as standard or fine milling. In an application with maximum working width, i.e., when all segments are mounted, the individual segments have different cutting circle diameters so that the road surface milled therewith is milled in a stepped manner in transverse direction.
The three last-mentioned solutions also have the disadvantage that the segmented milling tubes are subject to different wear since not all milling tube segments are always used.
From the generic WO 01/04422, a road milling machine with a machine chassis is known in which a milling roll is rotatably supported, the milling roll comprising a roll base body driven by a milling roll drive means via a gear unit and alternatively employable coaxial milling tubes adapted to be slid onto the roll base body from one side and being exchangeably mounted and carrying cutting tools on their outer shell surface.
In the known self-propelled road milling machine, the reduction gear unit is provided at the input side if the milling tubes extend over the entire working width. The roll base body is mounted to a radially projecting flange of the gear housing, a screw connection from the difficultly accessible input side being required. The known solution with the arrangement of the reduction gear unit on the input side cannot be employed in a sensible manner for milling tubes of a smaller milling width since the milling depth is limited for the following reasons:
The milling tubes almost have to be flush with the null side to permit a milling near the edge. The gear unit arranged on the input side would limit the realizable milling depth.
In case of milling tubes that do not extend over the entire working width, the reduction gear unit is therefore arranged on the null side of the machine, i.e., on the side where a milling near the edge is possible. This has the disadvantage that a drive shaft extending from the input side to the reduction gear unit on the null side is required, which has to be supported and provided with an additional protection tube as protection against damage. The reduction gear unit forms a stationary bearing, which, because of the arrangement on the null side, inevitably requires that a movable bearing be arranged on the input side. This is disadvantageous in that a pivotable lateral plate for the quick exchange of the milling tubes is arranged on the null side, which is less suitable for receiving the high reaction forces of a stationary bearing in axial direction. In this solution, the movable bearing is further located on the difficultly accessible input side on which, e.g., the torsion protection for the movable bearing must be mountable. Another disadvantage consists in that the long drive shaft acts like a torsional spring system whereby a rigid drive of the milling roll is not possible and the maximally possible cutting forces are reduced.
For supporting the milling tubes on the roll base body, split rings are absolutely necessary, which have to be mounted in a constrained position of the fitter. The mounting of the split rings may require to repeatedly change the rotational position of the roll base body, e.g., by 180, whereby the risks of an accident are increased.