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CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The invention described and claimed hereinbelow is also described in German Patent Applications DE 10 2007 049 889.8 filed on Oct. 18, 2007. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a vibration roller, having a vibration generator that has at least one unbalance shaft. 
         [0003]    Such vibration rollers are used for instance in self-propelled or manually movable trench compactors or in roller trains but are also used as compactor attachments for arms of excavators. To that end, they are moved over the area of soil to be compacted, while the vibration generator generates the vibration necessary for the compaction. 
         [0004]    In most known vibration rollers, the vibration generator is located in the interior of the rollers. This has the disadvantage that in servicing work on the vibration generator, as a rule the removal of the vibration generator from the roller is necessary, which is time-consuming. Moreover, the unbalance shafts become quite hot, which especially with vibration rollers that in their interior contain not only the vibration generator but also a drive unit for their own rotational drive, can lead to problems with temperature-sensitive components, such as electronic components. The hydraulic medium typically used for the drive also heats up severely from a generator unit located on the inside and must be cooled, which is complicated and expensive. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of the present invention is to furnish a vibration roller in which maintenance work can be done on a vibration generator without problems. It should furthermore be low in height, in order to reduce the lateral tilting moment and to assure good hill climbing capability. 
         [0006]    This object is attained with a vibration roller, having a vibration generator that has at least one unbalance shaft, which is characterized in that the vibration generator is located above the vibration roller. 
         [0007]    It has been demonstrated that when the vibration generator is located above the vibration roller, no disadvantages whatever in terms of the compacting performance arise, yet excellent accessibility to the vibration generator for maintenance work is assured. Since as a rule there is more space available above the vibration roller than in the interior of the roller, larger unbalance shafts can be provided than in the known vibration rollers, so that the generation of the complete vibrating mass and hence the compaction power can even be increased, compared to the known rollers with vibration generators located in the interior. 
         [0008]    Heat dissipation is also markedly simpler with vibration generators located above the roller than with vibration generators integrated with the rollers. 
         [0009]    Further advantages can be attained if the axis of the at least one unbalance shaft is oriented transversely to the axial direction of the vibration roller. The unit comprising the vibration roller and the vibration generator can then be manufactured with a lower height than when the axes of the vibration generator and roller are parallel to one another. Besides the lower height, a downward shift in the center of gravity of the unit is also attained, and as a result the risk of lateral tilting of the vibration roller can be reduced. 
         [0010]    Preferably, the vibration generator can have two axially parallel, contrarily rotatable unbalance shafts, so that directional vibration can be generated with the vibration generator. For that purpose, the drive of the two unbalance shafts can expediently be coupled, and as a result, only one of the unbalance shafts has to be actively driven. The coupling of the unbalance shafts can be effected via a gear or in some other way. It is understood that a separate drive, adapted to one another, of the two unbalance shafts is also conceivable. 
         [0011]    In a preferred embodiment, the at least one unbalance shaft can be provided with one eccentric weight mounted in a manner fixed against relative rotation and with one eccentric weight that is pivotable between two radially oriented stops. Depending on the quality of the soil to be compacted, a greater or lesser amplitude of the vibration generated can thus be selected. In one of the pivoted positions, the movable eccentric weight can reinforce the effect of the fixed eccentric weight, while in the other position it can reduce it. It is understood that naturally, the vibration frequency can be adapted to soil or ground conditions in a manner known per se. 
         [0012]    The direction of rotation of the at least one unbalance shaft can also be reversible. Thus the amplitude of the vibration generated by the vibration generator can also be varied by simply reversing the direction of rotation of the unbalance shafts. 
         [0013]    In principle, the invention also pertains to vibration rollers that are moved by hand. Preferably, however, a drive unit, preferably a hydraulic drive unit, for the rotational drive of the roller may be provided in the vibration roller. Such vibration rollers can be used for instance in remote-controlled, self-propelled equipment. 
         [0014]    The drive direction of the drive unit can be reversible, to enable compacting in both directions of travel even in tight spaces, where there is often no room for turning the roller around. 
         [0015]    Particularly with driven vibration rollers, it is advantageous if the vibration generator is located with its center of gravity in the cross-sectional plane of the vibration roller extending through the center of gravity of the vibration roller. In that case, the straight-ahead travel of the roller can be best assured. If the centers of gravity of the vibration generator and the vibration roller are too far apart, then lateral motions of the roller can occur, especially with vibration generators that generate directional vibration. 
         [0016]    The manifold possibilities for using the vibration roller can be enhanced even more markedly if the vibration generator is supported limitedly movably above the vibration roller in such a way that its center of gravity can be shifted to in front of and/or behind the vertical plane that extends through the axis of the vibration roller. 
         [0017]    If the vibration generator is supported limitedly displaceably horizontally, then by shifting the center of gravity of the vibration generator to in front of or behind the axis, the vibration amplitude can be reduced. 
         [0018]    If the vibration generator is supported limitedly pivotably about the axis of the vibration roller, then by the pivoting motion, the center of gravity of the vibration generator can for instance be shifted somewhat behind the axis and at the same time the vibration generator can be inclined, thus enormously improving the forward motion of the vibration roller and hence its hill climbing capability. The vibration roller can then be used even for compacting sloping terrain or very poorly accessible ground. 
         [0019]    A further way to increase the flexibility of use of the vibration roller is to equip it with replaceable bandages. Either smooth bandages, of the kind required more for compacting sandy soil, or profiled bandages for compacting heavy soils, can then be installed. 
         [0020]    The invention moreover relates to a compacting device or compacting vehicle having at least one vibration roller of the invention. 
         [0021]    The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a perspective view of a vibration roller having a vibration generator in accordance with the present invention; and 
           [0023]      FIG. 2  is a view from the front of the vibration roller in accordance with the present invention of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]      FIG. 1  shows a vibration roller  10 , which has a vibration generator  11  that is located above the vibration roller  10 . The vibration generator  11  has two unbalance shafts  12 ,  13 , located in separate housings, and the unbalance shaft  13  is driven by a motor  14 . The contrary drive of the unbalance shaft  12  required for driving the unbalance shaft  13  is accomplished by a gear  15 , located on the face ends of the unbalance shafts  12 ,  13 . As  FIG. 1  shows, the axial direction  16  of the unbalance shafts  12 ,  13  extends transversely to the axial direction  17  of the vibration roller. The vibration generator  11  is furthermore located such that its center of gravity is above the center of gravity of the vibration roller  10 , so that the vibration the vibration generator produces does not impair the straight-ahead travel of the vibration roller  10 . 
         [0025]    The amplitude and frequency of the vibration generated by the vibration generator  11  may be variable. For that purpose, the unbalance shafts  12 ,  13  may, in a manner known per se and not shown in further detail here, each have one eccentric weight located in a manner fixed against relative rotation and one adjustable eccentric weight. The adjustable eccentric weight can be pivoted between two stops, and in one position, it amplifies the effect of the fixed eccentric weight, and in the other direction, it lessens the effect of the fixed eccentric weight. 
         [0026]    The vibration roller  10 , in its interior, has a drive unit  18 , which can preferably be a hydraulic motor. For supplying oil to the hydraulic motor, in a middle region of the vibration roller  10  connections  19  are provided, to which hydraulic lines from a vehicle or device to which the vibration roller  10  can be attached can be connected. Because of the closed construction of the drive unit  18 , impairment of the drive from being contaminated with dirt is precluded. 
         [0027]      FIG. 2 , in the view from the front of the vibration roller  10  and the vibration generator  11 , clearly shows that the vibration roller  10  is provided with two bandages  20 ,  21  of different widths. The hydraulic connections  19  for the drive unit  18  in the interior of the vibration roller  10  are located in the gap  22  between the bandages  20 ,  21 . If a device or vehicle is now equipped with two vibration rollers  10 , and for the second vibration roller the bandage  20  on the left is wider than the bandage  21  on the right, so that the gaps  22  between the bandages  20 ,  21  of the two vibration rollers are offset from one another, then with such a device or vehicle, streak-free compaction of the soil can be done. 
         [0028]    The bandages  20 ,  21  are removable. Thus the profiled bandages  20 ,  21  shown here can also be replaced with smooth bandages, of the kind needed for instance for sandy soils. 
         [0029]    The vibration generator  11  can also be limitedly pivotable about the axis  17  of the vibration roller  10  or limitedly displaceable on the vibration roller  10  in the axial direction  16  of the unbalance shafts  12 ,  13 . By means of a horizontal displacement of the vibration generator  11  out of the middle position, the amplitude of the vibration exerted on the soil by the vibration roller  10  can be reduced. When the vibration generator  11  is pivoted out of the middle position, the vibration generated by the vibration generator acquires a component that reinforces the forward drive of the vibration roller  10 . 
         [0030]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
         [0031]    While the invention has been illustrated and described as embodied in a vibration roller, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
         [0032]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

Summary:
A vibration roller includes a roller with a vibration generator that has at least one unbalance shaft. The vibration generator is located above the vibration roller.