Patent Abstract:
The invention relates to an actuator ( 10 ) for units comprising a planetary gear ( 14 ), especially a planetary differential gear, whose radially inward region is embodied as a hollow shaft and which is equipped with a drive unit and a driven shaft that cooperates with the unit to be operated. A drive shaft of the planetary gear ( 14 ) is connected to the drive unit and can be driven by the same. Said drive shaft is configured as a first hollow shaft ( 16 ) while the driven shaft is embodied as a second hollow shaft ( 40 ). A planet carrier ( 28 ) is provided that is connected to the first hollow shaft ( 16 ) or is embodied with the radially inward region thereof as a first hollow shaft ( 16 ) in such a way that a rotary movement is also performed by the planet carrier ( 28 ) when the first hollow shaft ( 16 ) rotates while the drive unit as well as the first ( 16 ) and the second hollow shaft ( 40 ) encompass a common axis of rotation. Furthermore, at least the smaller of the two internal diameters of the hollow shafts is adapted to the transversal dimensions of a substantially longitudinally extending drive rod of a unit which can be connected to the driven shaft.

Full Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a §371 National Phase of PCT/EP2006/007134, filed Jul. 20, 2006 and titled Actuator for Units Comprising a Planetary Gear, the entirety of which is hereby incorporated by reference. 
     The invention is relative to an actuator for units with a planetary gear. 
     BACKGROUND 
     It is generally known that, among other things, planetary gears are used for actuators, so that the speed of a drive is reduced with the aid of this planetary gear to a desired slower speed of an actuator. 
     In a generally known actuator a motor drives an eccentrically arranged gear via an intermediate gear. A rotatably supported planet wheel is connected to the eccentrically arranged gear and rolls in an internal toothing of a sun gear. Due to the different number of teeth of the two gears a relative speed is created that is transmitted via coupling pins built on the planet wheel onto a driving disk. The driving disk is positively connected by a serration to a shaft. In this manner a relatively compact transmission is produced that, however, requires a relatively large space, viewed radially to the axis of rotation of the planetary gear, on account of the arrangement of the motor and of other components. In addition, the type of connection to the unit to be driven is sharply limited on account of the selected construction of such an actuator. 
     Furthermore, U.S. Pat. No. 3,391,583 also teaches an actuator with planetary gear for valve control in which a drive is provided that drives a driveshaft of the planetary gear with planet carrier and planet wheels via an appropriate intermediate gear. The driveshaft is almost completely enclosed and encapsulated by a housing element and a formed-on output shaft except for the area of an external toothing that forms a part of the intermediate gear. The rotary motion of the drive is transmitted via the intermediate gear with the appropriate translation onto the driveshaft and the planet wheels that for their part drive the output shaft. Drive, driveshaft and output shaft have no common axis of rotation. The previously cited actuator disadvantageously conditions a spatially extended, areal arrangement of drive and planetary gear. This does not make possible a compact construction of the actuator. 
     SUMMARY 
     Starting from this state of the art, the invention has the problem of indicating an actuator with a planetary gear that is constructed as compactly as possible, has a construction that is robust as possible and in addition makes possible the greatest versatility in the arrangement of the individual elements of the actuator. 
     This problem is solved by the invention with the actuator for units with the features disclosed herein. 
     The actuator for units in accordance with the invention comprises a planetary gear, in particular a planetary differential transmission, whose radially internal area is designed as a hollow shaft and that comprises an output shaft that cooperates with the unit to be operated. The actuator in accordance with the invention is furthermore provided with a drive. The planetary gear comprises a driveshaft that is connected to the drive and can be driven by it, which driveshaft is designed as a first hollow shaft and the output shaft as a second hollow shaft. The actuator in accordance with the invention is characterized in that a planet carrier is provided that is connected to the first hollow shaft in such a manner that or is designed with its radially internal area as a first hollow shaft in such a manner that upon a rotation of the first hollow shaft the rotary motion is also executed by the planet carrier and, that the drive as well as the first and second hollow shafts are arranged in such a manner that that they have a common axis of rotation and at least the smaller of the two inside diameters of the hollow shafts is adapted to the dimensions in the transverse direction of a drive rod of a unit that can be connected to the output shaft, which drive rod is extended substantially in the longitudinal direction. 
     In this manner the actuator of the invention avoids that a drive rod, frequently a drive spindle of an actuator, takes up the same spatial area close to the common axis of rotation as the planetary gear itself. In particular, this results in the possibility that the actuator can be arranged totally in the area close to the unit to be driven without the stroke of an adjusting body of the unit and therewith the stroke of the corresponding drive rod being a feature that would hinder the arrangement. In this manner on the one hand the actuator itself becomes more compact and on the other hand the constructive design possibilities for the arrangement of the actuator with a unit are increased. 
     One advantage of the actuator in accordance with the invention can also be seen in the fact that a penetration of a structural component of the unit through the spatial area of the actuator, namely, through the first and the second hollow shaft, is made possible. 
     In this manner the axes of rotation of the first and of the second hollow shaft as well as of the drive are combined in a common axis of rotation and the advantage furthermore remains that a drive body for a unit can again be established through the inside area of the hollow shafts. In addition, this makes the construction type of the actuator even more compact. The necessary radial space requirement around the common axis of rotation is correspondingly small. 
     In addition, it is now possible that the first hollow shaft is directly driven by a drive or, in a constructive variant of the actuator of the invention, forms a part of the drive, in particular the armature of an electromotor or the turbine or the impeller of a hydraulic- or pneumatic drive or -motor, or that the first and the second hollow shafts are designed as a common hollow shaft, and that even the common hollow shaft can be constructed in a constructive modification as part of the drive, in particular as the armature or rotor of an electromotor or as a turbine, rotor or impeller is designed as an armature or rotor of the electromotor or as a turbine, rotor or impeller of a of a hydraulic- or pneumatic drive. 
     In an alternative embodiment of the actuator of the invention an electromotor, hydraulic- or pneumatic drive is used as drive that comprises another hollow shaft as drive shaft that is connected to the first hollow shaft or is designed as the first hollow shaft and which other hollow shaft is designed as an armature or rotor of the electromotor or as a turbine, rotor or impeller of a hydraulic- or pneumatic drive. 
     The drive shaft designed as the first hollow shaft and the armature or rotor of the electromotor used as drive or of the hydraulic- or pneumatic drive used as drive are designed in one piece in an advantageous embodiment. 
     In this arrangement too the axes of rotation of the first hollow shaft, of the second hollow shaft and of the other hollow shaft of the drive are combined in a common axis of rotation and the advantage furthermore continues to remain that a drive body for a unit can again be realized through the inside area of the hollow shafts. 
     As a result of the above, the number of structural components is further reduced and the actuator rendered more compact. 
     In an advantageous embodiment the actuator comprises a planetary gear, especially a planetary differential transmission, with a planet carrier that comprises at least one planet wheel, with a drive shaft designed as the first hollow shaft, with an output shaft designed as the second hollow shaft and comprises a first internal toothing that is in engagement with a toothing of the at least one planet wheel, and comprises a support gear comprising a second internal toothing that is also in engagement with the toothing of the at least one planet wheel, and with which support gear the occurring forces or torques can be transferred to a housing with an active connection to the latter and the drive forces can be transferred to the at least one planet wheel or the planet carrier with the first hollow shaft, and an imaginary axis of rotation of the at least one planet wheel is always located outside of the inside diameter of the first hollow shaft. 
     Since the driveshaft as well as the output shaft are designed as hollow shafts, a free area is produced in the area of the axis of rotation of the hollow shafts which area is formed by the inside diameter of the hollow shafts. This free area can advantageously be utilized for the actuator since driven units usually require a certain adjusting lift as a rule that is usually made available by a spindle with a drive nut driven by the actuator. The adjusting lift can be comparatively large relative to the dimensions of the actuator itself. 
     A significant advantage of the planetary gear in accordance with the above as well as of the corresponding actuator is that the minimal inside diameter of the first and of the second hollow shaft can be given, namely, in particular for the diameter of a previously described driveshaft of a unit. In this manner such a drive spindle can be readily run through the hollow shaft or the hollow shafts of the planetary gear and/or of the actuator. The construction is correspondingly compact and totally new possibilities result for the arrangement of the planetary gear and/or of the actuator relative to the unit to be driven. 
     In addition, embodiments of a planetary gear and therewith also of an actuator that are especially favorable for oscillations are possible with planet wheels rotating around the first hollow shaft. The rotating masses are relatively small. An optimum of rotating planet wheels is achieved with three of these gears. 
     Also, the free end, namely, the end of the first hollow shaft, which end faces away from the second hollow shaft, can be provided in an advantageous further development of the planetary gear of the invention with a connecting element, especially a coupling, for connection to a drive. 
     An additional advantage results if the inside diameters of the first and of the second hollow shaft and/or of the other hollow shaft of the drive are adapted to each other. 
     It is achieved in this manner that the inside area of the hollow shaft is substantially without steps or offsets with edges and in this manner possible mechanical hindrances for a drive spindle running through the inside areas are avoided in the construction. 
     A further advantageous embodiment of the actuator is achieved in that the support gear of the planetary gear comprises an external toothing that is engaged with a toothing with a measuring shaft, that the forces and torques transmitted onto the measuring shaft are received by a spring arrangement connected to the measuring shaft, and that the deflection of the spring arrangement is a measurement for the magnitude of the transmitted force or of the transmitted moment. 
     In this manner the forces and moments are not simply introduced into the housing and dumped there but rather there is the possibility of directly detecting or indicating the magnitude of the force to be transmitted or of the moment to be transmitted, e.g., via an appropriate display device. Furthermore, this creates an elegant possibility of manually rotating the support gear, e.g., via an appropriate hand wheel. The rotation of the second hollow shaft and takes place directly without the complete reduction of the planetary gear being active. 
     Further advantageous embodiments of the subject matter of the invention can be gathered from the dependent claims concerning the actuator in accordance with the invention. 
     The invention, advantageously designed improvements of the invention as well as special advantages of the invention are explained and described in detail using exemplary embodiments represented in the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a first actuator 
         FIG. 1B  shows the first actuator including a drive spindle of a unit and 
         FIG. 2  shows a second actuator for units with a planetary gear. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1A and 1B  show a first actuator  10  comprising a first servomotor  12  as well as a first planetary gear  14  designed as a planetary differential transmission. These figures only show the essential mechanical parts necessary for explaining the planet transmission in accordance with the invention and the actuator in accordance with the invention. Thus, e.g., no housing is shown. However, it can be supplemented as needed by the knowledge of an expert in the art so that the customary but not shown structural parts for completing an actuator can be readily completed by an expert in the art. 
     The first servomotor  12  comprises a first hollow shaft  16  as drive shaft on whose one end a first shaft bearing  18  with a first shaft seal  20  is arranged, which arrangement comprises a recess  22  in the area of the first hollow shaft  16  which recess does not cover the inside area  24  of the first hollow shaft  16  at any position. The inside area  24  has a uniform diameter in its complete longitudinal extension. 
     The first hollow shaft  16  extends at its other, free end by a certain length over the spatial end of the longitudinal extension of a stator  26  of the first servomotor  12  by a length that ensures that the essential mechanical elements of the first planet transmission  14  can be arranged on this shaft end. Thus, in this arrangement first hollow shaft  16  is designed as the rotor shaft or armature shaft of first servomotor  12  as well as the drive shaft for first planet transmission  14 . 
     The free end of the first hollow shaft comprises the end area of the first hollow shaft facing away from the planet carrier as well as from the second hollow shaft. 
     A shoulder is formed on the outer jacket surface of the just described other shaft end on which shoulder a planet carrier  28  is arranged. The connection between planet carrier  28  and first hollow shaft  16  can be positively established in an especially simple manner, e.g., by a spring connection or non-positively, e.g., by a shrinking connection or also by other connection techniques familiar to an expert in the art. In addition, it is ensured that the drive forces pass-through first hollow shaft  16  into in a planet carrier  28  so that upon a rotation of first hollow shaft  16  the rotary motion is also executed by planet carrier  28 . 
     In the selected example planet carrier  28  carries three planet wheels and in this sectional view of actuator  10  only a first planet wheel  30  is shown. This planet wheel is supported in such a manner that it can rotate about support bolt  32  held in corresponding recesses of planet carrier  28 . According to the invention one planet wheel is sufficient for this. For reasons of oscillation technology a higher number of planet wheels are advantageous. A preferred number is achieved with three planet wheels. 
     The teeth of an external toothing of the planet wheels, that is, even of first planet wheel  30 , engage into the particular internal toothing of a first  34  as well as of a second gear ring  36  and roll over them in accordance with the toothing ratios. The first gear ring  34  is connected by a first connection pin  38  to a second hollow shaft  40  whereas the second gear ring is connected via a second connection pin  42  to a support gear  44 . Connection pins  38 ,  42  establish a secure connection between the particular gear rings  34 ,  36  and their carriers, that is, second hollow shaft  40  and support gear  44 . 
     In addition, support gear  44  also comprises an external toothing  46  that is engaged with a measuring shaft  48 . To this end measuring shaft  48  has a spiral area in its outer jacket surface. Measuring shaft  48  is then supported in a housing that is not shown in this figure so that any occurring forces and moments are reliably conducted away through the measuring shaft into this housing. 
     Such forces can arise as follows. The first hollow shaft  16  is rotated by first servomotor  12  and thus planet carrier  28  too. In an embodiment of the planetary gear that is favorable from an oscillation technology standpoint three planet wheels are provided, as present here, that are obligatorily moved by the rotation of planet carrier  28 . Forces and moments are transferred onto support gear  44  by the rolling of the planet wheels in the internal toothing of second gear ring  36 , which support gear finally transmits them into measuring shaft  48 . In the view of the measuring shaft as a section through the latter selected in  FIG. 1  the just described forces act in its longitudinal direction, so that an appropriate arrangement of springs in its longitudinal direction would be an advantageous possibility for receiving the forces. A possibility is then advantageously achieved for measuring the forces by measuring the deflection of the springs. In addition, the fixing of measuring shaft  48  in the housing brings it about that support gear  44  moves out of its angular position under the influence of the forces and moments only to a minimal extent. The power introduced by the planet wheels into the internal toothing of gear rings  38 ,  36  will accordingly only put the first gear ring  34  into a rotary movement. This gear ring is namely rotatably supported together with second hollow shaft  40  via a second shaft support  50 . In this manner the transmission of forces and moments from the drive shaft, namely, the first hollow shaft  16 , onto the output shaft, namely, the second hollow shaft  40 , is ensured. 
     The difference in the number of teeth of the internal toothing between first gear ring  34  and second gear ring  36  must only be an even multiple of the number of planet wheels present for mechanical reasons. In this manner the reduction ratio of the first planetary gear  14  can be especially readily adjusted in the construction via the number of planet wheels and the design of the internal toothings of the rings  34 ,  36 . 
     Comparable to the situation on first shaft bearing  18 , a second shaft seal  52  is also arranged on second shaft bearing  50  which ensures on the one hand that any dirt particles that may be present in the surroundings of first actuator  10  can not pass in the direction of the planetary gear. Even second shaft bearing  50  is supported in the final analysis in its radially external area on a housing of the planetary gear, which is not, however, shown in this figure. A suitable support of the shaft arrangement of first hollow shaft  16  and second hollow shaft  40  is ensured in that a third shaft support  54  with a third shaft seal  56  is arranged at a suitable location between servomotor  12  and first planetary gear  14  on the first hollow shaft  16 . 
     Second hollow shaft  40  has different inside diameters along its longitudinal axis corresponding to its function, of which, however, an extremely small inside diameter  58  corresponds to the diameter of inside area  24 . These diameters are adapted to each other. It is ensured in this manner that, e.g. a lift spindle of a unit spindle drive to be driven can be readily run through the two hollow shafts  16 ,  40  without there being any mechanical trouble spot. The connection of the first actuating transmission to a unit to be driven or to its lift drive or lift linkage is shown only schematically here. In this embodiment a groove  60  is shown on the side of second hollow shaft  40  facing away from the first servomotor  12  which groove constitutes a positive transfer of force of the forces conducted through second hollow shaft  40 , e.g., onto a drive nut  62  that fits into this groove  60 . In this manner the drive nut is put into a rotary movement but hindered in its spatial progress in the longitudinal direction of the axis of rotation of second hollow shaft  40 . Thus, a drive spindle  64  guided in the drive nut  62  is forced into a movement running in the longitudinal direction of the axis of rotation of second hollow shaft  40 . Thus, in the end the rotary movement of second hollow shaft  40  is converted into a longitudinal movement of a lift spindle  64  of a unit. 
     It is of course also conceivable that such a drive only has to make a slight rotary movement such as is required, e.g., for opening and closing ball valves, namely, a quarter circular turn. The rotary motion of first hollow shaft  16  is ensured solely via first servomotor  12 . Thus, e.g., an appropriate regulation of the speed of first servomotor  12  can be used in the end to change or regulate the opening speed or the closing speed of the activated unit. In this manner even any desired closing- or opening profiles with changing speeds can be performed. However, it is also a customary case that first servomotor  12  is operated at a constant speed. 
     The translation of the drive power of first hollow shaft  16  as regards power and torques is ensured by a suitable selection of the translation ratios in the planetary gear, namely, the suitable selection of the number of teeth of the planet wheels as well as of gear rings  34 ,  36 . In a simple case the number of teeth of internal toothing of the first gear ring  34  as well as of the second gear ring  36  can differ by only a few teeth, e.g., three teeth in a planetary gear with three planet wheels, especially with a total tooth number of gear rings of 72 and 75 teeth. However, even larger differences of tooth numbers are possible. 
     Note that second hollow shaft  40  only rotates when the tooth number between gear ring  34  and  36  is different. 
     The translation ratio of the transmission results from the ratio of the tooth number of the planet wheels and of first gear ring  34  and of second gear ring  36 . First gear ring  34  and second gear ring  36  must have a different number of teeth, as was already explained above. 
     The described embodiment of the actuator in accordance with the invention has the advantage that an especially small construction volume is achieved, in particular when viewed in the radial direction to the axis of rotation of first hollow shaft  16  and second hollow shaft  40 . In addition, the planetary gear used in accordance with the invention ensures an especially high efficiency and is distinguished by the planet wheels rotating about first hollow shaft  16  with an especially good quietness. An optimum of quietness is achieved if three planet wheels are used 
       FIG. 2  shows a second actuator  70  comprising a second servomotor  72  and a second planetary gear  74 . Many essential parts of second planetary gear  74  are designed like the corresponding parts of first planetary gear  14  so that the reference numerals from  FIG. 1  are used for these parts. Therefore, in the following even the differences between the first actuator  10  and the second actuator  70  will be discussed in particular. 
     In distinction to the first actuator  10  in the second actuator  70  a third hollow shaft instead of first hollow shaft  16  is the shaft that carries planet carrier  28  and is connected to the latter. Third hollow shaft  76  has a comparable inside area  24  that for its part has a diameter corresponding to the minimal inside diameter  58 . The third hollow shaft  76  has a externally toothed third gear ring  78  on its end facing away from second hollow shaft  40 . This ring engages into the teeth of a fourth gear ring  80  connected to a shaft end of a drive rotor  82  of the second servomotor  72 . The dimensions of the third gear ring  78  as well as of the fourth gear ring  80  are selected in such a manner that on the one hand the translation ratios corresponding to the tooth number of gear rings  78 ,  80  are suitable for the technical problem of the second actuator  70  to be solved and in addition the second servomotor  72  is located outside of an imaginary area resulting by a prolongation of the longitudinal extent of the inside area of the third hollow shaft  76 . This ensures in any case that a drive spindle run through second hollow shaft  40  and third hollow shaft  76  can not collide with any other part of second actuator  70 . 
     This measure brings it about that second servomotor  72  can be an especially economical standard motor. In addition, an increased flexibility in the designing of the translation ratios between second servomotor  72  and second hollow shaft  40  results from the different possibilities for the selection of the third gear ring  78  and of the fourth gear ring  80 . 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               10  first actuator 
               12  first servomotor 
               14  first planetary gear 
               16  first hollow shaft 
               18  first shaft support 
               20  first shaft seal 
               22  recess 
               24  inside area 
               26  stator 
               28  planet carrier 
               30  first planet wheel 
               32  support bolt 
               34  first gear ring 
               36  second gear ring 
               38  first connection pin 
               40  second hollow shaft 
               42  second connection pin 
               44  support gear 
               46  external toothing 
               48  measuring shaft 
               50  second shaft bearing 
               52  second shaft seal 
               54  third shaft support 
               56  third shaft seal 
               58  minimal inside diameter 
               60  groove 
               62  drive nut 
               64  drive rod or spindle 
               70  second actuator 
               72  second servomotor 
               74  second planetary gear 
               76  third hollow shaft 
               78  third gear ring 
               80  fourth gear ring 
               82  drive rotor

Technology Classification (CPC): 5