Abstract:
A vibrating plate comprises an upper mass with a drive, a lower mass with a soil contact plate ( 12 ), and a vibration generator device, which belongs to the lower mass and which acts upon the soil contact plate ( 12 ). The vibration generator device comprises at least two individual exciters ( 13 ) each having an unbalanced shaft ( 2 ). The individual exciters ( 13 ) can be individually controlled with regard to the rotational speed and/or phase position of the respectively assigned unbalanced shaft ( 2 ). A mechanical coupling of the unbalanced shafts ( 2 ) is thus unnecessary. The unbalanced shaft ( 2 ) of an individual exciter ( 3 ) can be rotationally driven by a hydraulic motor ( 4 ). The position of the unbalanced shaft ( 2 ) is determined in at least one position by a position indicator ( 7 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a vibrating plate according to the preamble of patent claim  1 . 
         [0003]    2. Description of the Related Art 
         [0004]    Vibrating plates are known and are made up in principle of a lower mass having a soil contact plate and an upper mass that is flexibly coupled to the lower mass so as to be movable and that has a drive (e.g. an internal combustion engine or an electric motor). The drive drives a vibration exciter device that appertains to the lower mass and that charges the soil contact plate. 
         [0005]    As a vibration exciter device, what is known as a one-shaft exciter or plate compactor is known in which the drive rotationally drives an imbalance shaft that bears an imbalance mass. During its rotation, the imbalance shaft pulls the soil contact plate upward and forward in order to achieve a forward movement. Subsequently, the soil contact plate is pressed downward by the action of the imbalance shaft and strikes the soil that is to be compacted. 
         [0006]    In larger vibrating plates, the vibration exciter device has two or three imbalance shafts that are coupled to one another mechanically, or with a positive fit. In the two-shaft exciter, two imbalance shafts, each bearing an imbalance mass, are positively coupled to one another and are situated so as to be capable of rotation in opposite directions. The phase relation of the imbalance shafts to one another can be adjusted mechanically using a linkage device or a differential gear mechanism. As drives for the adjustment, hydraulic cylinders, Bowden cables, or spindles are known. By adjusting the phase position of the imbalance shafts to one another, the direction of a resultant force vector can be modified, resulting in a modification in the advance behavior. In particular, in this way forward and backward travel of the vibrating plate can be achieved. 
         [0007]    In another development, the imbalance mass on one of the imbalance shafts is divided into two or more partial imbalance masses that can be adjusted relative to one another. If the partial imbalance masses on the imbalance shaft are adjusted asymmetrically to one another, a yaw moment about the vertical axis of the vibration exciter device can be produced, enabling the vibrating plate to be steered. Given a symmetrical adjustment, in particular if partial imbalance masses are fixedly attached to the relevant imbalance shaft and other partial imbalance masses are capable of being moved relative thereto, the resulting imbalance effect can be adjusted, enabling setting of the resultant imbalance forces. 
         [0008]    Due to the strong imbalance effect, the forces on the adjusting drives for adjusting the phase position of the imbalance shafts to one another and the phase position of the various imbalance masses on one imbalance shaft are high. The adjustment mechanism is exposed to high alternating forces, which have an adverse effect on its working life span. 
         [0009]    Standardly, the imbalance shafts in known vibration exciter devices are situated parallel to one another. In modern vibrating plates, this makes it possible to achieve forward and backward travel, as well as rotating the vibrating plate in place or causing it to travel on a curved path. In some applications, however, the user will desire a lateral movement of the vibrating plate, for example in order to be able to drive behind lateral projections. When compacting soil on laterally inclined surfaces, the vibrating plate often drifts obliquely downward, so that the operator has to orient the vibrating plate obliquely in order to compensate this. However, this means that at the upper and lower edge the soil is compacted only by a corner of the soil contact plate, resulting in unsatisfactory compaction. 
         [0010]    In such cases, it would be helpful for the vibrating plate to be, able to execute a lateral movement. In order to achieve such a lateral movement, however, the vibration exciter device would have to achieve a corresponding force effect in the lateral direction, which is possible only using imbalance shafts that are situated obliquely or at an angle. The angled situation of imbalance shafts in known vibration exciter devices, and their mechanical coupling to the overall drive mechanism, would require a significant gearing expense, with correspondingly high costs and weight. 
       OBJECT OF THE INVENTION 
       [0011]    The underlying object of the present invention is to indicate a vibrating plate in which the mechanical outlay for the drive of the imbalance shafts in the vibration exciter device can be reduced. 
         [0012]    According to the present invention, this object is achieved by a vibrating plate according to patent claim  1 . Advantageous further developments of the present invention are indicated in the dependent patent claims. 
         [0013]    A vibrating plate according to the present invention has an upper mass comprising a drive, a lower mass comprising at least one soil contact plate, and a vibration exciter device that charges the soil contact plate. The vibration exciter device has at least two individual exciters, each comprising at least one imbalance shaft that bears an imbalance mass. According to the present invention, the individual exciters can be individually controlled with respect to the rotational speed and/or phase position of the respectively allocated imbalance shaft. 
         [0014]    Thus, according to the present invention small units in the form of individual exciters are provided that in the simplest case have only a single imbalance shaft. The rotational speed and the phase position of this imbalance shaft can be controlled individually, i.e. independent of the rotational speed or the phase position of other imbalance shafts. The overall vibration exciter device, in contrast, has at least two of these individually controllable individual exciters. 
         [0015]    The phase position of the imbalance shaft relates to its position in relation to the other imbalance shaft or shafts that work together with it. If one of the imbalance shafts is defined as a reference system, the other imbalance shaft or shafts can either rotate with the same phase position or can be rotated by a particular phase angle thereto. The phase position of each of the imbalance shafts should be defined with reference to a unified reference system. 
         [0016]    In a particularly advantageous specific embodiment of the present invention, each of the individual exciters has a hydraulic motor or electric motor that rotationally drives the respective imbalance shaft, and has a position sensor that acquires the position of the imbalance shaft in at least one position. In this way, on the one hand each of the imbalance shafts can be individually driven by the hydraulic motor (electric motor) allocated to it, while on the other hand via the position sensor the actual position of the imbalance shaft is regularly or constantly monitored. The position sensor should acquire the position of the imbalance shaft at least in one position, i.e. once during a rotation of the imbalance shaft, from which the rotational speed of the imbalance shaft can be determined and intermediate positions can also be interpolated. Of course, the position sensor can also be constructed in such a way that it permanently acquires the rotational position of the imbalance shaft and thus its rotational speed. The precise recognition of the rotational position is important in order to enable the phase position of the imbalance shaft to be derived therefrom. 
         [0017]    Advantageously, an actuating element, in particular a hydraulic valve, is allocated to the hydraulic motor, the individual exciter having a controller for evaluating a signal from the position sensor and for controlling the actuating element, in such a way that a target rotational speed and/or target phase position that are prespecified to the controller for the relevant imbalance shaft is achieved. 
         [0018]    Instead of the hydraulic motor, another suitable individual drive can be used for the individual imbalance shafts of the individual exciters, e.g. a controllable electric motor. However, at present electric motors are still too susceptible to vibration, and therefore, due to the strong vibrations, will probably not have a sufficient life span. 
         [0019]    Thus, each individual exciter has its own control circuit in which the imbalance shaft forms the control path and the position sensor forms the measurement element. The position of the imbalance shaft, and thus its actual phase position and actual rotational speed, is determined with the aid of the position sensor and is supplied to the controller as a measurement value. Of course, the evaluation of the signal by the position sensor can also first take place in the controller itself, in order for example to determine the actual rotational speed. On the basis of the values specified to the controller for the target rotational speed or the target phase position, the controller controls the actuating element, in particular the hydraulic valve, so that the allocated hydraulic motor drives the imbalance shaft in the desired manner. 
         [0020]    In a particularly advantageous specific embodiment of the present invention, a central control unit is provided in order to coordinate the controller of the individual exciters and in order to specify an individual target rotational speed and/or target phase position for each controller of the individual exciters, in such a way that the soil contact plate behaves in a way that is desired by an operator and/or is specified by an operating or driving program. 
         [0021]    The central control unit, e.g. a process computer, thus has the task of forming the connecting element between the operator and the individual exciters of the vibration exciter device. The operator gives the central control unit a desired driving instruction for the vibrating plate, e.g. forward, backward, rotating, lateral, or curved travel. In the central control unit, corresponding driving programs are allocated to this wish on the part of the operator, from which specifications are derived for the individual target rotational speeds, and in particular target phase positions, of the imbalance shafts in the individual exciters. These target values are individually supplied to the controllers of the individual exciters, and the controllers of the individual exciters ensure a corresponding behavior of the respectively allocated imbalance shafts. 
         [0022]    In another specific embodiment of the present invention, instead of the controllers of the individual exciters and the higher-order central control unit, only a “generally responsible” central controller is provided. The central controller is used to evaluate the signals from the individual position sensors of the individual exciters and for the individual controlling of the actuating elements of the individual exciters in such a way that the behavior of the soil contact plate desired by the operator and/or specified by a driving program is achieved. In contrast to the decentralized design described above, the central controller provides a centralized controlling. The central controller centrally acquires the behavior of each imbalance shaft and takes the measures required for the imbalance shaft to carry out the rotational behavior demanded of it. Here as well, the decisive factor is the operator&#39;s wishes, or a prespecified driving program, according to which e.g. forward travel or backward travel of the soil contact plate is demanded. 
         [0023]    In the controlling of the rotational speed and phase position of the imbalance shafts, it is possible to exploit a particular feature: due to energetic interaction effects, imbalance shafts situated on a common rigid bearer have the tendency to synchronize with one another with respect to their rotational speed. Presupposing corresponding target values in particular for the phase position, the controllers then only have to adjust the changes or differences out of the self-synchronizing position in order to achieve the desired relative position or phase position of the relevant imbalance shaft. 
         [0024]    Preferably, the imbalance shafts of the individual exciters are driven with the same rotational speed. In this way, a behavior of the cooperating individual exciters can be achieved that corresponds to the behavior of known purely mechanically operating vibration exciters, in particular those based on a positive coupling of the participating imbalance shafts. 
         [0025]    However, advantageously, the individual controllability of the individual exciters also makes it possible for the imbalance shaft to be driven by at least one of the individual exciters with a different rotational speed than the imbalance shafts of the other individual exciters. In particular, this different rotational speed can be an odd-numbered multiple, e.g. three times or five times, of the rotational speed of the imbalance shafts of the other individual exciters. In this way, in particular applications a particular vibration behavior of the vibration exciter device can be achieved that would be practically impossible to realize, or realizable only at significant expense, in purely mechanically operating vibration exciters having toothed gear mechanisms. An only temporary deviation of the rotational speed would be almost completely excluded in purely mechanically operating vibration exciters, because for this purpose a manual transmission would be required. 
         [0026]    The different rotational speed of at least one of the imbalance shafts can make it possible to apply particularly hard impacts to the soil for particular cases of application. 
         [0027]    In a particularly advantageous further development of the present invention, at least one of the individual exciters is capable of being controlled in such a way that the imbalance shaft allocated to it intentionally achieves a non-uniform rotational speed. In principle, it must be assumed that the rotational speed of an imbalance shaft fluctuates due to the permanent exchange of energy between the kinetic energy of the imbalance shaft itself and the soil contact plate charged by it. The allocated controller will always attempt to keep the rotational speed of the imbalance shaft at the prespecified target value. However, due to the high speed it must be assumed that the controller will not be able to compensate rotational speed fluctuations for the exchange of energy. Rather, in the normal case it will be sufficient to set the average phase position and rotational speed of the imbalance shaft to the desired target value. 
         [0028]    However, in the specific embodiment named here, the controller has the task of intentionally impressing a non-uniform rotational speed independent of the rotational speed fluctuation that is almost unavoidable in practice. Here it can be useful if, during a rotation, the imbalance shaft intentionally achieves different rotational speeds in order e.g. to enable a longer contact with the soil of the soil contact plate, so that the impact energy can be effectively transmitted into the soil. 
         [0029]    In a particularly advantageous specific embodiment of the present invention, a second vibration exciter device that charges the soil contact plate is provided, having at least two imbalance shafts that are positively coupled to one another and that are driven so as to rotate in opposite directions. A position sensor is allocated to at least one of the imbalance shafts of the second vibration exciter device in order to determine the phase position of this imbalance shaft. A signal from this position sensor is supplied to the central control unit or to the central controller in order to coordinate the rotational speed and/or the phase position of the imbalance shafts of the second vibration exciter device with the individual exciters. 
         [0030]    In this specific embodiment, a “conventional” vibration exciter device that operates purely mechanically through positive coupling (toothed gears) is thus combined with the above-described individual exciters of the vibration exciter device according to the present invention. This makes it possible to continue to use the purely mechanically operating second vibration exciter device, whose principle of operation has proved very successful over many years. For example, the second vibration exciter device can be used to produce vibration forces that are used only for forward or backward travel, while force effects for steering or for lateral travel of the vibrating plate are achieved by the vibration exciter device with individual exciters according to the present invention. In another variant, the purely mechanically operating second vibration exciter device is used exclusively to produce vertical compaction forces, while the forces for advancing and steering the vibrating plate are achieved by the individual exciters of the vibration exciter device according to the present invention. 
         [0031]    The central control unit or central controller coordinate the behavior of the second vibration exciter device with the individual exciters of the vibration exciter device according to the present invention in order to achieve the desired behavior of the soil contact plate. 
         [0032]    Preferably, the position sensor has a device for acquiring the angle of rotation. This makes it possible to precisely acquire the position, and thus also the rotational speed, of an imbalance shaft at all times. 
         [0033]    In another specific embodiment of the present invention, the individual exciters and/or the second vibration exciter device are situated so as to be distributed on a plurality of soil contact plates. Thus, the lower mass has a plurality of soil contact plates to each of which, a purely mechanical second vibration exciter device and/or one or more individual exciters are allocated. Here, almost arbitrary combinations are possible. Of course it is also conceivable to distribute only individual exciters of the vibration exciter device according to the present invention on the soil contact plates, without requiring the presence of a second vibration exciter device. 
         [0034]    In a particularly advantageous specific embodiment of the present invention, at least some of the imbalance shafts of the individual exciters are situated on the soil contact plate in such a way that the force vectors produced by them act in different planes. Through the rotation of the imbalance shafts, the imbalance masses situated thereon each produce a centrifugal force vector that rotates in a plane that is perpendicular to the axis of rotation of the imbalance shaft. If the axes of rotation of the imbalance shafts are situated so as to be differently oriented on the soil contact plate, the force vectors of the imbalance masses correspondingly also act in different planes. Depending on the controlling of the imbalance shafts, force effects in different directions can be produced that bring about a corresponding movement behavior of the soil contact plate. 
         [0035]    Preferably, at least some of the imbalance shafts of the individual exciters are situated on the soil contact plate in a star shape, axially, parallel, or at angles to one another. Of course, any mixed combinations of these types of arrangements are also conceivable in order to achieve a desired travel and directional behavior of the one soil contact plate or the plurality of soil contact plates. 
         [0036]    In a further development of the present invention, at least one of the imbalance shafts bears a larger imbalance mass than do other imbalance shafts. Such a specific embodiment takes into account for example the recognition that in the large majority of cases the vibrating plate is used in forward and backward travel operation, while rotations, as well as curved and oblique travel, represent exceptions or require smaller force effects. Correspondingly, the individual exciters that are used for forward and backward travel should have imbalance shafts having a larger imbalance mass than do the individual exciters that are used only to bring about curved or oblique travel. 
         [0037]    These and additional advantages and features of the present invention are explained in more detail below with the aid of the accompanying Figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]      FIG. 1  shows a schematic section through an individual exciter according to the present invention; 
           [0039]      FIG. 2  shows a vibration exciter device according to the present invention having two individual exciters; 
           [0040]      FIG. 3  shows a variant of a vibration exciter device according to the present invention having two individual exciters; 
           [0041]      FIG. 4  shows a top view of a soil contact plate having a vibration exciter device according to the present invention, according to a first specific embodiment of the present invention; 
           [0042]      FIG. 5  shows a top view of a soil contact plate having a vibration exciter device according to the present invention, according to a second specific embodiment of the present invention; 
           [0043]      FIG. 6  shows a top view of a soil contact plate having a vibration exciter device according to the present invention, according to a third specific embodiment of the present invention; 
           [0044]      FIG. 7  shows examples of arrangements of individual exciters. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0045]    As described above, the present invention relates to a soil compaction device realized as a vibrating plate, whose design is known in principle. An essential component of a vibrating plate is a vibration exciter device that introduces a directed vibration into a soil contact plate. The vibrating soil contact plate acts on the soil in order to compact it. In addition, the resultant overall force produced by the vibration exciter device can bring about travel in the longitudinal or lateral direction and a steering of the vibrating plate. Because this design has long been known, a more detailed description is not necessary here. 
         [0046]    The vibrating plate according to the present invention has a vibration exciter device having at least two individual exciters  13  that act on a soil contact plate  12 . 
         [0047]      FIG. 1  shows a sectional representation of the schematic design of an individual exciter  13  according to the present invention. 
         [0048]    In an e.g. tube-shaped housing  1 , an imbalance shaft  2  is mounted so as to be capable of rotation. Imbalance shaft  2  bears an imbalance mass  3 . 
         [0049]    Imbalance shaft  2  is rotationally driven by a hydraulic motor  4 . Hydraulic fluid is supplied to hydraulic motor  4  via a hydraulic line  5 , by a hydraulic supply system (not shown). The hydraulic supply system can be situated essentially on the upper mass of the vibrating plate. A component of the hydraulic supply system is for example a diesel, gasoline, or electric aggregate that drives a hydraulic pump. 
         [0050]    The hydraulic pump produces a hydraulic pressure in a hydraulic fluid that can be stored in a hydraulic storage device. Furthermore, a hydraulic supply container for collecting and storing the hydraulic fluid must be present. Due to the strong vibrations in the lower mass, it is useful if most of the components of the hydraulic supply system are situated in the upper mass, which is decoupled in terms of vibration from the lower mass. In this way, it is necessary only to create a connection from the hydraulic supply system to the hydraulic motor  4  with the aid of hydraulic line  5 . 
         [0051]    Downstream from hydraulic motor  4  there is situated a hydraulic valve  6  that acts as an actuating element that controls the hydraulic outflow after hydraulic motor  4 , and thus influences the rotational speed of hydraulic motor  4 . Of course, hydraulic valve  6  can also be situated upstream from hydraulic motor  4 . 
         [0052]    At an end of imbalance shaft  2  situated opposite hydraulic motor  4 , there is situated a position sensor  7 . Position sensor  7  (e.g. a device for acquiring the angle of rotation) is able to acquire the position of imbalance shaft  2  in at least one position. This can take place for example optically, magnetically, inductively, or capacitively. From the possibility of acquiring the position of imbalance shaft  2  at least one time during a rotation thereof, the rotational speed and the phase position of imbalance shaft  2  can be determined. In addition, it is straightforwardly possible to determine the position of the imbalance shaft  2  with sufficient precision at any time using interpolation over time. The position of imbalance shaft  2  is important because imbalance mass  3  carried by it produces a strong centrifugal force effect during rotation. The centrifugal force of imbalance mass  3  works together with the centrifugal forces of the other individual exciters  13  that belong to the vibration exciter device, thus producing an overall resultant force effect that determines the movement behavior of soil contact plate  12  charged by individual exciters  13 . Soil contact plate  12  can move in the desired manner only when both the rotational speeds of imbalance shafts  2  and also their phase positions are precisely coordinated to one another. 
         [0053]    The vibration exciter device according to the present invention has at least two of these individual exciters  13  that are situated on soil contact plate  12  in a suitable manner. Possible specific embodiments are described below. 
         [0054]    Individual exciter  13  shown in  FIG. 1  also has a controller  8  that evaluates the signal produced by position sensor  7  and determines at least the rotational speed and/or the position of imbalance mass  3  relative to a particular in time (phase position). 
         [0055]    In addition, controller  8  also receives (as is explained below) a target value signal  9  that specifies the required target rotational speed or target phase position. Controller  8  correspondingly controls hydraulic valve  6  in order to achieve the desired rotational speed and phase position of imbalance shaft  2  or imbalance shaft  3 , with the aid of hydraulic motor  4 . 
         [0056]      FIG. 2  shows the schematic design of the vibration exciter device according to the present invention having two individual exciters  13  according to  FIG. 1 . In  FIG. 2 , individual exciters  13  are situated parallel to one another. 
         [0057]    A central control device  10  is provided that specifies target value signals  9  for each of the controllers  8  of individual exciters  13 . Each controller  8  then ensures in the manner described above, for the individual exciter  13  allocated to it, that imbalance shaft  2  behaves in the desired manner. 
         [0058]    Target value signals  9  specified by central control device  10  can differ for each of individual exciters  13 . Essential distinguishing parameters include target rotational speed, target phase position, and target direction of rotation. The change of the direction of rotation is optional and requires an additional constructive expense in the realization of hydraulic motor  4  or of hydraulic valve  6 . In the normal case, a change in the direction of rotation will not be required. 
         [0059]    As examples,  FIG. 2  shows two individual exciters  13 . Of course, it is straightforwardly possible to provide a vibration exciter device according to the present invention with more than two individually controllable individual exciters  13 . 
         [0060]      FIG. 3  shows another specific embodiment of the present invention, in which the vibration exciter device is also shown with two individual exciters  13 . 
         [0061]    Differing from the individual exciters described in connection with  FIGS. 1 and 2 , the individual exciters in  FIG. 3  do not have individually allocated controllers  8 . Rather, the signals from position sensor  7  are supplied to a central controller  11  that evaluates all the signals from all the individual exciters  13 . Central controller  11  then correspondingly controls each of the hydraulic valves  6  individually, in order to achieve the desired behavior of imbalance shaft  2  individually for each exciter  13 . 
         [0062]    In this specific embodiment, the constructive expense is lower than in the specific embodiment shown in  FIGS. 1 and 2 , due to the fact that only a single controller is required. This in turn offers the advantage that the individually allocated controller  8  makes possible a very fast, small circuit. 
         [0063]    Central control unit  10  or central controller  11  contain suitable operating or driving programs with which the travel and vibration behavior of the vibrating plate desired by the operator and specified via operating elements (remote control, operating lever, buttons) can be converted into control specifications for individual exciters  13 . If, for example, the operator wishes to carry out a transition from standing compaction of the vibrating plate to forward travel, central control unit  10  or central controller  11  brings about an adjustment of the phase position in at least one of the individual exciters  13 , causing a change in the direction of action of the resultant overall force. 
         [0064]    For reliable normal operation, it is desirable for imbalance shafts  2  to rotate with exactly the same rotational speed, as far as possible. Because, however, the position of imbalance shaft  2  is also constantly monitored, deviations in the rotational speed can be corrected at any time in order to maintain the desired phase position between the imbalance shafts. A progressive deviation of the rotational speed is thus excluded. 
         [0065]    Hydraulic valve  6 , which acts as an actuating element for controlling the rotational speed and the phase position of imbalance shaft  2 , should be capable of being switched rapidly. In practice, various solutions are possible in addition to, or also alternatively to, the specific embodiment shown in  FIG. 1 : 
         [0066]    Hydraulic valve  6  can also be situated upstream in the line of supply to hydraulic motor  4 . This valve should be a fast proportional valve. If a multiway valve is used, it is possible to rigidly clamp hydraulic motor  4 , so that for a certain period of time imbalance shaft  2  does not participate in the vibration production. 
         [0067]    In addition, a plurality of hydraulic motors  4  can be supplied with the same quantity of oil via a hydraulic synchronizing block. Alternatively, an individual hydraulic pump can be allocated to each hydraulic motor  4 . The correction of the rotational speed and phase position of the imbalance shaft takes place with the aid of smaller, individually allocated metering or discharge valves that slightly increase or decrease the volume flow of hydraulic fluid to or away from hydraulic motor  4 . 
         [0068]    In addition, a proportional valve can be situated before the hydraulic synchronizing block in order to adapt the rotational speed of the overall system as needed in the particular circumstances. The hydraulic synchronizing block can also be replaced by comparatively slow individually provided metering valves. 
         [0069]    In addition, it is possible to provide rapidly switched open/shut valves, also in combination with one of the variants described above. If a plurality of rapid open/shut valves are connected in parallel, a proportionality can be reproduced in a stepped fashion. 
         [0070]    Hydraulic motor  4  and hydraulic valve  6  can also be replaced by an adjusting hydraulic motor that can be controlled directly by controller  8 . In addition, an individually allocated adjusting hydraulic pump can be provided for each imbalance shaft  2 . 
         [0071]    Due to the high vibration amplitudes at the lower mass, it is not useful to situate electromagnetic valves there. These must always be provided on the upper mass. However, currently valves are being developed that are more resistant to vibration, such as e.g. piezovalves or magnetic fluid valves, which, if they prove successful in practice, could be situated very close to hydraulic motor  4 . In this way, imprecisions due to the compressibility of the hydraulic fluid and the elasticity of the conduits would be excluded. 
         [0072]      FIG. 4  shows a schematic top view of a soil contact plate  12  on which four individual exciters  13  are situated at angles to one another. Through corresponding controlling of individual exciters  13 , an almost arbitrary travel behavior of soil contact plate  12  can be achieved in the forward, backward, and lateral directions, as well as rotation in place and curved travel. 
         [0073]      FIGS. 5 and 6  show additional specific embodiments of the present invention in the form of individual exciters  13  that are differently situated on soil contact plate  12 . Individual exciters  13  are situated in a star-shaped pattern ( FIG. 5 ), axially ( FIG. 5 ), in parallel ( FIGS. 5 and 6 ), or at an angle ( FIGS. 4 to 6 ) to one another on the soil contact plate. 
         [0074]    In choosing the arrangement, almost any possibility is available to someone skilled in the art, because he no longer has to take into account the mechanical coupling of the imbalance shafts of the vibration exciter, as he previously had to do. Rather, he can situate the individual exciters  13 , each representing a complete unit, arbitrarily on soil contact plate  12 . There then remains only the problem of programming the controlling, in the form of central control unit  10  or central controller  11 , in a manner that suitably takes into account the arrangement of individual exciters  13 . 
         [0075]      FIG. 7  shows additional possibilities for the situation of individual exciters  13  on soil contact plate  12 . For simplification, individual exciters  13  are shown only as lines. 
         [0076]      FIG. 7   a  correspondingly shows the imbalance shafts of individual exciters  13  situated partially in parallel, axially displaced, coaxially, and/or partially at an angle to, one another. 
         [0077]    In addition to the “normal” individual exciters  13 ,  FIG. 7   b  shows reinforced individual exciters  14  that have an imbalance shaft having a larger imbalance mass. Correspondingly, reinforced individual exciters  14  are symbolically shown not as lines, but rather as elongated boxes. 
         [0078]    Reinforced individual exciters  14  can be used predominantly to achieve a stronger compaction effect or a faster forward and backward travel. Correspondingly, the “normal” individual exciters  13 , or the individual exciters having smaller imbalance masses, are provided for the steering of the vibrating plate. The imbalance shafts provided in reinforced individual exciters  14 , having enlarged imbalance masses, can however be replaced by “normal” individual exciters  13  if for example a plurality of individual exciters  13  are situated one after the other, parallel to one another. 
         [0079]      FIG. 7   c  symbolically shows a specific embodiment in which instead of one soil contact plate  12 , three partial soil contact plates  12   a ,  12   b ,  12   c  are provided, each bearing individual exciters  13 , that are connected to one another via connecting elements  15 . In this way, a relatively large vibrating plate can be realized that nonetheless travels easily over the ground due to the flexibility that can be achieved by the separate soil contact plates  12   a  to  12   c , which are capable of being moved relative to one another. 
         [0080]    Central control unit  10  or central controller  11  make it possible to execute prespecified programs, and thus to carry out defined travel states. These include travel in a straight line forward and backward, vibration in place, or curved travel. Given more than four individual exciters  13  that can be controlled independently of one another, it is also possible to adjust the movement of the lower mass by modifying the angular positions of the imbalance shafts to one another in such a way that the impact of soil contact plate  12  on the soil takes place in parallel or as an intentional edge impact in which one edge, or even only a corner, first contacts the soil, while the rest of the underside of soil contact plate  12  contacts the soil only after that. For central control unit  10  or central controller  11 , intelligent control devices using fuzzy logic and/or having adaptive characteristics are preferred in order to enable adaptation to the actual soil and terrain conditions.