Abstract:
Disclosed is an oscillatingly driven machine tool including a tool spindle that is mounted pivotably about its longitudinal axis, further including a drive motor that is coupled to a hydraulic generator for generating an oscillating fluid flow which drives a hydraulic motor being configured as a rotor blade motor. The rotor blade motor drives the tool spindle in such a way that the tool spindle rotates oscillatingly about its longitudinal axis. The rotor blade motor includes symmetrically arranged rotor blades that are disposed at regular angular distances with respect to each other.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an oscillatingly driven machine tool comprising a drive motor and a tool spindle mounted pivotably about its longitudinal axis and driven rotatingly oscillatingly about its longitudinal axis. 
       BACKGROUND OF THE INVENTION 
       [0002]    Such oscillatingly driven machine tools are known in various designs. They are driven by means of a mechanical oscillatory gear transforming the rotating drive motion of a drive motor into a rotary oscillatory drive motion of the tool spindle about its longitudinal axis. 
         [0003]    According to EP 1 428 625 A1 to this end an eccentric is provided which works together with an eccentric fork for oscillatingly driving the tool spindle. The eccentric is driven rotatingly by an eccentric shaft which is mounted in parallel to the tool spindle. 
         [0004]    According to EP 2 283 979 A1 an oscillatingly driven machine tool comprises a drive motor with a motor shaft as well as a tool spindle which is rotatingly oscillatingly driven about its longitudinal axis, wherein a coupling element rotatingly driven by the motor shaft and comprising a closed guide surface circulating about a guide axis, wherein the guide surface is coupled by means of transfer means to at least one entrainer for driving the latter, wherein the at least one entrainer is held movably with respect to the work spindle and engaging within a circumferential region of the work spindle for driving the latter rotatingly oscillatingly. 
         [0005]    Such mechanical oscillatory gears are known in various embodiments, for transferring the rotating drive motion of a motor shaft into the rotatingly oscillatingly movement of the tool spindle. 
         [0006]    Due to the constantly increasing demands for the performance of oscillatory tools herein high demands are present with respect to the mechanical oscillatory gears. These are subject to a high mechanical load due to the oscillatory load and therefore may be subject to wear in long-time operation. In case of high load also the noise generation increases. Finally the oscillatory gears lead to more or less vibrations depending on the load which partially is sensed disadvantageously by the user. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of this it is one object of the invention to disclose an oscillatingly driven machine tool that allows for a high mechanical load. 
         [0008]    It is a further object of the invention to disclose an oscillatingly driven machine tool that is simple and reliable in the long-run. 
         [0009]    It is another object of the invention to disclose an oscillatingly driven machine tool having little wear. 
         [0010]    It is another object of the invention to disclose an oscillatingly driven machine tool having little vibrations. 
         [0011]    According to one aspect of the invention an oscillatingly driven machine tool is disclosed comprising a tool spindle mounted pivotably about its longitudinal axis, further comprising a drive motor being coupled with a hydraulic generator for generating an oscillating fluid flow for driving a hydraulic motor configured as a rotor blade motor for rotatingly oscillating driving said tool spindle about a longitudinal axis thereof. 
         [0012]    The object of the invention is solved in this way. 
         [0013]    By using a hydraulic device for the rotary oscillatory drive of the tool spindle higher drive powers than with mechanical oscillatory gears are made possible, wherein partially simultaneously the wear can be reduced and the smooth running can be improved. The rotor blade motor makes possible a direct conversion of the pulsating fluid energy into an oscillatory motion of the tool spindle without requiring a mechanical gear to this end. 
         [0014]    A particular advantage of the above design rests in the fact that by a suitable dimensioning of the hydraulic device the essential parameters of the oscillatory drive can be adjusted, namely in particular the oscillation angle, the angular velocity, the angular acceleration and the generated rotary moment. In particular high rotary moments can be generated with relative little wear and vibrations. 
         [0015]    According to another aspect of the invention the rotor blade motor comprises symmetrically arranged rotor blades arranged in defined angular distances with respect to each other. 
         [0016]    In this way one-sided bearing loads (in lateral direction) are avoided. An overall more even bearing load and thereby a reduced wear are obtained. 
         [0017]    According to another aspect of the invention the rotor blades are configured as rotor blade fingers on the tool spindle. 
         [0018]    In this way a particularly simple design is obtained. 
         [0019]    According to another aspect of the invention the tool spindle runs within a bushing configured suitably as a counterpart. 
         [0020]    In this way a low-wear connection can be obtained. 
         [0021]    Preferably on both sides of the rotor blade fingers fluid chambers are formed together with the bushing that are coupled with connections of the hydraulic generator pressure-pulsating oppositely. 
         [0022]    By these measures a simple design and a simple sealing of the fluid chambers are obtained. 
         [0023]    According to another aspect of the invention the bushing is made of a bronze alloy, and the tool spindle preferably is made of steel. 
         [0024]    By such a material pairing the sliding friction is minimized, a reduced wear and a permanently low inner leakage at the rotor blade fingers are obtained. 
         [0025]    According to another aspect of the invention the rotor blade motor comprises four rotor blade fingers which are offset angularly each by 90° with respect to each other. 
         [0026]    Thereby a good compromise between a small installation space and a low idle pressure of the hydraulic system is reached. 
         [0027]    According to another aspect of the invention the hydraulic generator is configured as a displacement pump comprising a linear piston which is driven by the motor shaft of the drive motor by means of an eccentric. 
         [0028]    Thereby a particularly simple and reliable design of the hydraulic generator is reached. 
         [0029]    According to another aspect of the invention on both ends of the linear piston pressure chambers are formed, wherein the oppositely pulsating fluid energy is generated. 
         [0030]    Herein preferably each of the two pressure chambers is coupled via a manifold to assigned bores at the bushing for supplying the fluid chambers on both sides of the rotor blade fingers with oppositely pulsating fluid. 
         [0031]    In this way a simple and reliable design is reached. 
         [0032]    According to another aspect of the invention a hydraulic fluid reservoir subjected to pressure is provided, which is coupled to the hydraulic generator by means of check valves. 
         [0033]    Herein the hydraulic fluid reservoir may for instance be configured as a chamber of a cylinder. The respective pressure supply is generated by a spring acting onto the piston being displaceable within the cylinder. 
         [0034]    In this way a compensation for leakage losses is ensured. 
         [0035]    It will be understood that the afore-mentioned features of the invention and the features to be explained hereinafter cannot only be used in the given combination, but also in different combinations or independently, without leaving the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    Further features and advantages of the invention can be taken from the subsequent description of preferred embodiments with reference to the drawings. In the drawings show: 
           [0037]      FIG. 1  is a partial section of an oscillatingly driven tool machine according to the invention; 
           [0038]      FIG. 2  is a principle representation of a rotor blade motor according to the invention which according to  FIG. 1  is used for directly transforming oscillatory fluid energy into an oscillatory drive motion of the tool spindle; 
           [0039]      FIG. 3  is a longitudinal section through the multiple chamber rotor piston according to  FIG. 2 ; 
           [0040]      FIG. 4  is a perspective view of the multiple chamber rotor pistons according to  FIG. 3 ; 
           [0041]      FIG. 5  is a simplified section through the hydraulic generator according to  FIG. 1 ; and 
           [0042]      FIG. 6  is a principle representation of the total hydraulic system of the machine tool according to  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    In  FIG. 1  an oscillatingly driven machine tool is shown and depicted in total with numeral  10 . 
         [0044]    The tool machine  10  comprises a tool spindle  34  which is mounted by means of two roller bearings  26 ,  28  pivotably about its longitudinal axis  35 . 
         [0045]    The tool spindle  34  is configured as a hollow spindle including a plunger  25  received therein and biased against the force of a spring (not shown) and a holding element  27  held thereon. The plunger  25  can be displaced by means of a clamping lever  23  via an eccentric  24  acting axially onto the plunger  25  against the bias of the spring, to which end the clamping lever  23  is pivoted from the clamping position shown in  FIG. 1  to the front into a release position. Thereby a clamping element  37  held within the holding element  27  and engaging by means of a toothing  39  into the holding element  27  is released so that the clamping element  37  can be removed to allow a removal of a tool held between the outer front face of the tool spindle  34  and a head  33  of the clamping element  37 . 
         [0046]    For clamping, the clamping element  37  again is introduced through an assigned opening of the tool into the tool spindle  34 , until the toothing  39  engages the holding element  37 , and the clamping lever  23  is again moved into the clamping position according to  FIG. 1 . 
         [0047]    The tool spindle  34  can be driven about its longitudinal axis  35  at high frequency and in the range of about 5,000 to 30,000 oscillations per minute and at a pivot angle in the range of about ±1° to ±5° (from reversal point to reversal point). Preferably the frequency corresponds to the rotational speed of the drive motor  14  that is used and is about 20,000 oscillations per minute or about 333 Hz. The pivot angle from reversal point to reversal point preferably is about ±2.5°. 
         [0048]    For transferring a high power onto the tool spindle  34  now a hydraulic gear is used by contrast to the mechanical coupling by means of an oscillatory gear as known in the prior art. 
         [0049]    To this end a hydraulic generator is driven by motor  14  which in  FIG. 1  is simply depicted with numeral  22 . The oscillating fluid energy from the hydraulic generator  22  is transferred by means of a hydraulic motor  30  being coupled with the tool spindle  34  into a rotary oscillatory drive motion of the tool spindle  34  about the longitudinal axis  35  thereof. 
         [0050]    In  FIG. 2  the hydraulic motor  30  according to  FIG. 1  is shown schematically. It is configured as a symmetrically designed rotor blade/pivot blade motor (in short rotor blade motor)  30  comprising four rotor blades  38  which are each angularly offset by 90° with respect to each other and which are formed on the outer side of the tool spindle  34 . To each rotor blade finger  38  two adjacent fluid chambers  40 ,  41  are assigned which are formed between the tool spindle  34  and the surrounding bushing  32  within which the tool spindle  34  runs in this region. 
         [0051]    Thus on both sides of each rotor blade finger  38  adjacent fluid chambers  40 ,  41  are formed. Thus in total along the circumference of the tool spindle  34  eight fluid chambers  40 ,  41  are formed in defined angular distances to each other. From these the fluid chambers  40  on the one rotary side are coupled with each other by means of an assigned manifold  43  and are connected to the hydraulic generator  22 . The other fluid chambers  41  on the other rotary side are coupled with each other by means of an assigned manifold  42  and are connected to the other output of the hydraulic generator  22 . By means of the hydraulic generator  22  a pulsating fluid pressure is generated, whereby the pressure pulses alternatingly between the two outputs to which the manifolds  42  and  43 , respectively, are connected. Thus alternatingly an excess pressure results in the fluid chambers  40  and in den fluid chambers  41 . In this way the pulsating hydraulic energy is directly transformed into an oscillatory rotary motion of the tool spindle  34 . 
         [0052]    The hydraulic generator  22  used to this end can be seen in more detail from  FIG. 5 . 
         [0053]    The motor shaft  15  of the drive motor  14  is mounted as its end at which the blower  17  is held as mounted on the housing  12  by means of a roller bearing  16 . At the end of the motor shaft  15  an eccentric  18  is supported whereon an eccentric bearing  20  is provided. The eccentric bearing  20  engages into a linear piston  46  so that the latter is moved oscillatingly back and forth in longitudinal direction upon rotation of the motor shaft  15 , as shown by the double arrow  48 . The linear piston  46  at each of its two ends, respectively, acts together with a fluid chamber  50  and  52 , respectively, so that the hydraulic fluid present within the fluid chambers  50  and  52 , respectively is alternatingly compressed by the movement of the linear piston  46  within one pressure room pressure chamber  50  and the other pressure chamber  52 . 
         [0054]    The pulsating hydraulic energy thus generated is coupled directly via the manifolds  42 ,  43  into the assigned fluid chambers  40  and  41 , respectively of the hydraulic motor  30 , so that the rotary oscillatory drive motion of the tool spindle  34  results. 
         [0055]    According to  FIG. 5  the linear piston  46  is connected centrally with the eccentric bearing  20  so as to avoid an unsymmetric bearing load. To this end the eccentric bearing  20  is configured as a parted bearing consisting of two individual bearings which engage on the linear piston  46  symmetrically. 
         [0056]    From  FIG. 4  it can be seen how the fluid chambers  40 ,  41  that are formed between the tool spindle  34  and the bushing  32  can be coupled from the outside with the two hydraulic lines via bores  44 ,  45  within the bushing  32 . The hydraulic lines (not shown) can be screw-connected with the bores  44 ,  45 . In a preferred embodiment the hydraulic lines are incorporated into the upper housing  12  and each contact directly the respectively assigned bores  44  and  45 , respectively. 
         [0057]    While the tool spindle  34  preferably consists of steel, the bushing  32  preferably consists of a bronze alloy. 
         [0058]    In this way a particularly low sliding friction and thus a wear minimization results. 
         [0059]    From  FIG. 3  it can be seen that a disk-shaped sealing ring  31  is arranged on both sides of the bushing  32  at the tool spindle  34 . 
         [0060]    The hydraulic schema of the tool machine  10  according to  FIG. 1  is shown schematically in  FIG. 6 . 
         [0061]    In the upper half of  FIG. 6  the hydraulic generator  22  is depicted which is driven by means of the drive motor  14  via the motor shaft  15  and the eccentric  18  driven thereby. The eccentric  18  moves the linear piston  46  within a fluid cylinder  54 . Thus, in the pressure chambers  50 ,  52  at both ends of the linear piston  46  respective pressure pulsations with opposite signs result. The two pressure chambers  50 ,  52  of the hydraulic generator  22  are connected with the rotor blade motor  30  by means of fluid lines  42 ,  43 . The rotor blade motor  30  in the configuration shown here comprises two rotor blade fingers  56  opposite each other which are formed directly on the tool spindle  34 . The counterpart to the rotor blade fingers  56  at the tool spindle  34  is formed by a suitably shaped bushing  32  which preferably consists of bronze. 
         [0062]    On both sides of each rotor blade finger  56  between the tool spindle  34  and the bushing  32  a respective fluid chamber  57 ,  58  or  71 ,  72 , respectively, is formed. Fluid chambers  57 ,  72  and  56 ,  71 , respectively arranged opposite each other and acting in the same rotary direction are each commonly coupled with the respective fluid line  42  and  43 , respectively. 
         [0063]    In this way the alternating pressure pulsations within the lines  42 ,  43  result in a rotary pivot motion of the tool spindle  34  about its longitudinal axis  35 . In  FIG. 6  exemplarily only two rotor blade fingers  56  are indicated which are arranged opposite each other. It will be understood that preferably a higher number of rotor blade fingers can be used so that it is configured as a multiple-chamber rotor blade motor as explained above with reference to  FIG. 2 . 
         [0064]    To avoid an excess pressure, both fluid lines  42 ,  43  may be connected with an overpressure valve  64  or  63 , respectively. The overpressure valves  63 ,  64  are merely optional. If they are dispensed with, then this can be reached by a sufficient dimensioning. At the limit the drive motor  14  runs slowlier and thus avoids a further pressure rise. An omission of the overpressure valves  63 ,  64  counteracts a drifting of the tool spindle  34  from the center position. 
         [0065]    In addition to both lines  42 ,  43  a pressurized fluid reservoir  66 ,  67  is connected via assigned check valves  62  and  61 , respectively, using a common line  70 . 
         [0066]    Fluid losses that are unavoidable in practical operation can be compensated in this way. A suitable amount of hydraulic fluid is received to this end in a fluid cylinder  66 . The latter is biased by means of a piston  67  which is pressurized by a suitably dimensioned spring  68 . 
         [0067]    Thus within the line  70  a specific fluid pressure is set which may for instance be in the range of 2.9 to 5.2 bars. If the pressure in one of the two lines  42 ,  43  falls below this value, then hydraulic fluid from the fluid cylinder  66  is conveyed. To this end the check valves preferably have an opening pressure of 0.2 bars. 
         [0068]    Between the two lines  42 ,  43  which are connected to the pressure chambers  50 ,  52  of the fluid cylinder  54 , in addition, a bypass throttle  60  is arranged. 
         [0069]    By means of the bypass throttle  60  the amplitude of the oscillatory motion of the tool spindle  34  can be adjusted continuously, and the tool spindle can be manually adjusted into the central position when the bypass throttle  60  is open.