Abstract:
An eccentric drive for driving cutter mechanisms on mowing attachments for combine harvesters is provided that comprises a gearbox housing ( 16 ), a gearbox chamber ( 12 ) enclosed by the gearbox housing ( 16 ), a first shaft ( 20 ) mounted in the gearbox housing ( 16 ), a cavity ( 88 ) formed in the first shaft ( 20 ) and having its cross-sectional center of gravity eccentric to the axis of rotation ( 18 ), in which cavity a second shaft ( 106 ) is rotatably mounted, having a toothed region ( 124 ), which is engaged with the gearbox housing ( 16 ), and a shaft end region ( 113 ) protruding axially from the cavity ( 88 ) of the first shaft ( 20 ), and a third shaft ( 26 ) wherein a flywheel body ( 152 ) can be connected to the third shaft ( 26 ) via a bushing ( 154 ) that is tapered on its outer surface ( 158 ) and is arranged rotatably fixedly and axially fixably on the third shaft ( 26 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to drives for eccentric drives. 
       BACKGROUND OF THE INVENTION 
       [0002]    Eccentric drives that have gear transmissions arranged at an angle to one another and gear shafts arranged one inside another are known in the prior art. Eccentric drives with gear shafts arranged one inside another provide a compact design and are one possibility for realizing eccentric drives. Eccentric drives are used, for example, in agriculture for driving cutter mechanisms on mowing attachments for combine harvesters. Such eccentric drives can additionally have a flywheel body on their driveshaft, which is mounted on the shaft and rotatably fixed thereon. It is common to secure this flywheel body rotatably fixedly on the driveshaft by means of a conventional feather key/groove connection and to clamp it via a shaft nut against a shaft shoulder on the driveshaft. 
         [0003]    If there is too little clamping torque or during highly stressed operating states, the shaft nut can come loose on the shaft, threatening the loss of the flywheel body, with which irreparable damage to the eccentric drive and its environment and therefore also high repair costs and maintenance effort can arise. In order to counteract this, it was attempted to form the shaft nut and the driveshaft larger for the purpose of being able to apply a larger clamping torque, but this entails material and tool costs as well as increased maintenance effort. Another solution was to lock the flywheel body and the shaft together by a transverse pin, whereby the production and assembly expense became uneconomical. 
         [0004]    The problem addressed by the invention is that of specifying an eccentric drive of the type mentioned above by which one or more or of the above-mentioned problems are overcome. 
         [0005]    The problem is solved according to the invention by the teaching of Claim  1 . Advantageous configurations and refinements of the invention are found in the subordinate claims. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention relates to an eccentric drive, having a gearbox housing, a gearbox chamber enclosed by the gearbox housing, a first shaft mounted in the gearbox housing, a cavity formed in the first shaft and having its cross-sectional center of gravity eccentric to the axis of rotation, a second shaft rotatably mounted in the cavity of the first shaft and having at least one toothed region and one shaft end region protruding axially from the cavity of the first shaft, and a third shaft mounted in the gearbox housing, the axis of rotation of which third shaft includes an angle to the plane lying on the axis of rotation of the first shaft, wherein the third shaft accommodates a flywheel body. 
         [0007]    According to the invention, an eccentric drive of the type mentioned above is constructed in such a manner that the flywheel body can be connected to the third shaft via a conically tapering bushing arranged rotatably fixedly and axially fixably on the third shaft, wherein the flywheel body has a conically tapering hub corresponding to the outer surface of the bushing, with which hub the flywheel body can be pressed on the outer surface of the bushing by means of a shaft nut arranged on the third shaft. Owing to this arrangement, particularly the conical formation of the bushing and the flywheel body, a much larger surface area is created on which a clamping torque can be exerted, whereby greater frictional forces can act at the connection of flywheel body and bushing, with equal or even less clamping torque. The use of a conical bushing also makes it possible to adapt already existing flywheel bodies by slight modifications, so that the eccentric drives assembled according to the conventional method can be modified or converted at low expense. 
         [0008]    A recess for receiving a rotational driver is formed on the outer surface of the bushing and a broached groove is formed on the inner side of the hub. This measure proves to be easy to assemble and inexpensive, and therefore also offers the above-mentioned advantages. 
         [0009]    The recess can be formed as a Woodruff key groove and the rotational driver as a Woodruff key, wherein the Woodruff key can be formed as a semicircular half-disk. This type of design is distinguished by a simple variant that is cost effective in terms of production and assembly effort. 
         [0010]    It is possible in the same manner, however, to design the recess as a feather key groove and the rotational driver as a feather key. This may increase the production expense, but it also increases wear resistance. 
         [0011]    A recess for receiving the rotational driver is likewise formed on the shaft and a broached groove is formed on the inner side of the bushing. The recess on the shaft is advantageously formed as a feather key groove and the rotational driver as a feather key. The above mentioned advantages result equivalently in this way. 
         [0012]    The invention, advantages thereof and advantageous refinements and configurations of the invention will be described in detail below with reference to the drawing, which shows an embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  shows a first partial cross-sectional view of an eccentric drive having a flywheel body on a shaft of the eccentric drive. 
           [0014]      FIG. 2  shows a second partial cross-sectional view of the eccentric drive from  FIG. 1  and an enlarged detail of the arrangement for connecting the flywheel body to the shaft of the eccentric drive. 
           [0015]      FIG. 3  shows a third partial cross-sectional view of the eccentric drive from  FIGS. 1 and 2  and an enlarged detail of the arrangement for connecting the flywheel body to the shaft of the eccentric drive. 
           [0016]      FIG. 4  shows a perspective side view of a bushing from the connection arrangement according to  FIGS. 2 and 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIGS. 1-3  show an eccentric drive  10  having a gearbox housing  16  surrounding a gearbox chamber  12  of a right-angle gear unit  14 . The gearbox housing  16  extends substantially along the axis of rotation  18  of a first shaft  20 , the axis of rotation  18  defining a longitudinal direction of the eccentric drive  10 . The gearbox chamber  12  is subdivided into a first gearbox chamber  22 , which substantially surrounds the first shaft  20 , and a second gearbox chamber  24 , which substantially surrounds a third shaft  26  arranged at an angle (nearly a right angle) to the longitudinal direction. The gearbox chamber regions  22 ,  24  are formed adjoining one another in the longitudinal direction and have a common cylindrical transition region  28 , which is arranged approximately centrally in relation to the longitudinal extent of the gearbox housing  16  and coaxially with the axis of rotation  18 , and by which a connection of the gearbox chamber regions  22 ,  24  is defined. 
         [0018]    In the first gearbox chamber region  22 , the gearbox housing  16  has a first cylindrical opening  30 , which is oriented coaxially with the axis of rotation  18  and opens the first gearbox chamber region  22  axially outward. The gearbox housing  16  further comprises a second, third and fourth cylindrical opening  32 ,  34 ,  36  in the second gearbox chamber region  24 . The second opening  32  is oriented coaxially with the axis of rotation  18  and opens the second gearbox chamber  24  axially outward. The third and fourth openings  34 ,  36  are arranged on both sides of the axis of rotation  18  and coaxially with an axis of rotation  38  of the third shaft  26 , which is arranged at an angle (nearly a right angle) to the axis of rotation  18 . 
         [0019]    A first bearing  40  is arranged in the common transition region  28 , and a second bearing  42 , for the first shaft  20 , is arranged in the first opening  30  in the first gearbox chamber region  22 . A shoulder  44 , which fixes the bearing  40  axially in the direction of the first opening  30 , is formed at the common transition region  28 . A shoulder  46  formed at the first opening  30  fixes the bearing  42  in the direction of the common transition region  28 . The bearings  40 ,  42  are preferably constructed as rolling contact bearings and are shown for the sake of example as ball bearings in  FIG. 1 . The first shaft is received by the bearings  40 ,  42  and is rotatably mounted in the gearbox housing  16  or in the first gearbox chamber region  22 . A first shaft seal ring  47  such as an oil seal, which seals the movement gap between the first opening  30  and the first shaft  20 , is also arranged facing outward at the first opening  30 , adjacent to the second bearing  42 . 
         [0020]    In the second gearbox chamber region  24 , a housing cover  48 , which delimits the second gearbox chamber  24  axially toward the surroundings, is arranged at the second opening  32 . 
         [0021]    A first bearing  49  in the third opening  34  and a second bearing  50  for the third shaft  26  in the fourth opening  36  are arranged in the second gearbox region  24 . A shoulder  52 , which fixes the bearing  49  axially in the direction of the fourth opening  36 , is formed at the third opening  34 . An annular groove  56  provided with a locking ring  54 , whereby the bearing  49  is axially fixed in the opposite direction as well, is also formed at the third opening  34 . The bearing  50  is arranged floating in the fourth opening  36 . The bearings  49 ,  50  are preferably formed as rolling contact bearings. The third shaft  26  is received by the bearings  49 ,  50  and is rotatably mounted in the gearbox housing  16  or in the first gearbox chamber region  24 . A second shaft seal ring  57 , such as an oil seal, which seals the movement gap between the fourth opening  36  and the first shaft  26 , is also arranged at the fourth opening  36 . A bearing cover  58  provided at the third opening  34  seals the third opening  34  toward the outside. 
         [0022]    An additional shoulder  59 , on which a ring gear  60  is mounted, is also formed in the first gearbox chamber region  22  between the bearings  40 ,  42 . The ring gear  60  is bolted to the gearbox housing  16  by means of bolts  62  distributed on the periphery of the shoulder  59  (see  FIG. 3 ). 
         [0023]    The first shaft  20  extends through the entire first gearbox region  22  and has a shaft end region  64 , protruding from the first opening  30  and covering substantially the entire diameter of the first opening  30 . Starting from the shaft end region  64 , a first shaft shoulder  65  is formed, which is adjoined by a shaft seal ring region  65 ′ for the shaft seal ring  47 . Starting from the shaft end region  64 , a second shaft shoulder  66  is formed, which is adjoined by a bearing region  68  for the second bearing  42 . A third shaft shoulder  70 , which is adjoined by a central shaft region  72 , is formed adjoining the bearing region  68 . The central shaft region  72  ends at a fourth shaft shoulder  74 . The fourth shaft shoulder  74  is followed by fifth shaft shoulder  76 , which is adjoined by a shaft stub  78 , the shaft stub  78  extending through the entire transition region  28  into the second gearbox housing region  24 . A first bevel gear  80 , which is connected non-rotatably via a key-and-groove connection  82  to the first shaft  20  or the shaft stub  78 , is mounted on the shaft stub  78 . The shaft stub  78  is provided with a shaft nut  84 . A bearing region  86 , by which the first shaft  20  is received in the first bearing  40 , is formed on the first bevel gear  80 . 
         [0024]    The first shaft  20  is provided with a cavity  88 . The cavity  88  is formed substantially cylindrically about an axis of rotation  90 , the axis of rotation  90  being arranged parallel to the axis of rotation  18  and eccentrically to the first shaft  20 . The cavity  88  has a cylindrical opening  92 , which opens the cavity  88  toward the shaft end  64  of the first shaft  20  axially relative to the axis of rotation  90 . Starting from the opening  92 , the cavity  88  has a first and a second shoulder  94 ,  96  and ends at a cavity bottom  98 . Between the first and the second shoulders  94 ,  96 , the cavity  88  is provided at the height of the ring gear  60  with an opening  100 , which extends radially and axially relative to the axis of rotation  90  along the cavity wall and opens a portion of the cavity wall toward the ring gear  60 . 
         [0025]    A first bearing seat  102  for receiving a first bearing  104  for a second shaft  106  is formed between the second shoulder  96  of the cavity  88  and the cavity bottom  98 . A second bearing seat  108  for receiving a second bearing  110  for the second shaft  106  is formed between the opening  92  of the cavity  88  and the first shoulder  94 . The second bearing  110  is axially secured by pressing the outer bearing ring of the second bearing  110  against the first shoulder  94  by means of a plate bolted  112  onto the end face  111  of the shaft end region  64 . 
         [0026]    The first and second bearings  104 ,  110  for the second shaft  106  are constructed as rolling contact bearings, wherein a roller bearing in the form of a needle bearing is provided for the first bearing  104  and a ball bearing is provided for the second bearing  110 , as illustrated in  FIG. 1 . 
         [0027]    The second shaft  106  extends through the entire cavity  88  of the first shaft  20  and has a shaft end region  113  protruding from first opening  92  of the first shaft  20 . 
         [0028]    Starting from the shaft end region  113 , the second shaft  106  is provided with a first shaft shoulder  114 , which is adjoined by a bearing region  116  for the second bearing  110 . An annular groove  118  that receives a locking ring  120  (shown in  FIG. 1 ) adjoins the bearing region  116 . A second shaft shoulder  122 , which ends in a toothed region  124  of the second shaft  106 , adjoins the annular groove  118 . The toothed region  124  of the second shaft  106  extends axially between the shoulders  94 ,  96  of the cavity  88  and ends in a third shaft shoulder  126 . The third shaft shoulder  126  is adjoined by a shaft stub  128 , on which a bearing region  130  for the first bearing  104  is formed. 
         [0029]    The third shaft  26  extends through the entire second gearbox chamber region  24  and has a toothed shaft end region  132  protruding from the fourth opening  36  (see  FIGS. 2 and 3 ). Starting from the shaft end region  132 , the third shaft  26  has a shaft region  134  which is adjoined by a shoulder  136 , wherein a part of the shaft region  134 , on which a shaft nut  138  is arranged, protrudes from the fourth opening  36 . A shaft region  140 , adjoined by a shaft stub  142 , extends between the shoulder  136  and the third opening  34 . A bearing region  144 , which is received by the first bearing  49  of the second gearbox chamber region  24 , is formed on the shaft stub  142 . The bearing region  144  is adjoined by a thread having a shaft nut  145  for axially securing the third shaft  26 . A second bevel gear  146 , which is connected non-rotatably to the third shaft  26  via a rotational driver  148  in the form of a feather key of a key-and-groove connection, is mounted on the shaft end region  134 . A bearing region  150 , by which the third shaft  26  is received in the second bearing  50 , is formed on the second bevel gear  146 . In addition, a flywheel body  152 , which is mounted on a bushing  154  and axially secured thereon by means of the shaft nut  138 , is arranged on the part of the shaft region  134  protruding from the fourth opening  36 . The flywheel body  152  is connected non-rotatably to the third shaft  26  via a further rotational driver  156  in the form of a Woodruff key of a Woodruff key/Woodruff groove connection arranged between bushing  154  and flywheel body  152 . As illustrated in  FIGS. 2 ,  3  and  4 , the bushing  154  has a cylindrically shaped inner surface  157  and an outer surface  158  that tapers conically in the direction of the shaft end region  132 . The flywheel body  152  has a hub  160  with a conically tapering inner surface  162  matching the outer surface  158  of the bushing  154 . In addition, a key groove  164 , which is engaged with the rotational driver  148  constructed as a key, is formed on the inner surface  157  of the bushing  154 . A recess  166  in the form of a Woodruff key groove, which engages with the rotational driver  156  constructed as a Woodruff key, is also formed on the outer surface  158  of the bushing  154 , wherein a groove  168  engaging with the rotational driver  156  is formed in the hub  160 , so that a rotatably fixed connection between bushing  154  and hub  160  is produced via the rotational driver  156 . 
         [0030]    The assembly and the relevant advantages of the illustrated eccentric drive  10  will now be briefly discussed. 
         [0031]    Starting from the gearbox housing  16 , the housing is equipped with the ring gear  60  and with the second bearing  42  for the first shaft  20 , as well as with the first shaft seal ring  47 . This is followed by the insertion of the first shaft  20  into the first gearbox chamber region  22  through the first opening  30 . The first bevel gear  80 , preassembled with the second bearing  40 , is guided via the shaft stub  78  through the second opening  32  of the second gearbox region  24 . The bevel gear  80  and the bearing  40  are axially clamped by the shaft nut  84  and the shaft shoulder  76 , and the first shaft  20  is axially secured. 
         [0032]    The second shaft  106  is preassembled with the first bearing  104  and the second bearing  110 , the second bearing  110  being secured with the locking ring  120  in the annular groove  118 . The preassembled second shaft  106  is guided into the cavity  88  of the first shaft  20  and axially fixed by means of the plate  112 . 
         [0033]    The third shaft  26  is preassembled in such a way that the shaft region  134  is preassembled with the second bevel gear  146  and the second bearing  50 . The opening  34  is equipped with the first bearing  49 . The third shaft  26 , together with bevel gear  146  and second bearing  50 , can then be guided with the shaft stub  144  at the front through the first opening  36  into the second gearbox chamber region  24 , and can be pushed into the first bearing  49  and secured via the shaft nut  145  on the first bearing  49 , already fixed in the first opening  34 . 
         [0034]    After insertion of the third shaft  26 , the shaft is sealed by the shaft seal ring  57 , which is fitted between second bevel gear  146  and second opening  36 . This is followed by the mounting of the flywheel body  152 . The bushing  154  is first pushed onto the shaft region  134 , with the key groove  164  oriented flush with the rotational driver  148  (feather key). Then the rotational driver  156  (Woodruff key) is placed in the recess  166  formed as a Woodruff key groove, before the flywheel body  152 , along with its hub  160  and the groove  168  formed therein, is pushed, aligned with the rotational driver  148  (Woodruff key), onto the outer surface  158  of the bushing  154 . The conically formed outer surface  158  of the bushing and the conically formed inner surface  162  of the hub  160  are then pushed or pressed onto one another or clamped to one another by screwing the shaft nut  138  onto the shaft region  134 . The flywheel body  152  is thus clamped, together with the bushing  154 , between one end of the second bevel gear  146 , which forms a shoulder  170 , and the shaft nut  138 . 
         [0035]    The conical formations of the hub  162  and the bushing  154  achieve, with a relatively low axial clamping force, both a high level of axial clamping between second bevel gear  146  and shaft nut  138  and a fixation of the flywheel body in the circumferential direction of the second shaft  26  with a high-level of frictional engagement in the circumferential direction between bushing  154  and flywheel body  152 . A detachment of the flywheel body even under the highest stresses during operation is prevented by the increased frictional engagement between bushing  154  and flywheel body  152 , and by the high level of axial clamping. Due to the increased frictional engagement between the bushing  154  and the flywheel body  152  and the high level of axial clamping of both parts of the bushing to the flywheel body, loosening even under extreme stress during operation can be prevented. The high level of frictional engagement between bushing  154  and flywheel body  152 , which is created by the conical arrangement, makes it possible for a Woodruff key with a Woodruff key-woodruff key groove connection to suffice as the rotational driver  156 , which requires a substantially lower production expense compared to a conventional key-and-groove connection. Nevertheless, a key-and-groove connection can alternatively be used here. 
         [0036]    Even though the invention was described with reference to only one embodiment, various alternatives, modifications and variants that fall under the present invention will be evident to a person skilled in the art in light of the foregoing description.