Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Applicants claim priority under 35 U.S.C. §119 of German Patent Application No. 10 2010 003 085.6 filed Mar. 19, 2010. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates to a device for feeding and attaching corrective elements for unbalance correction to rotors having a rotor axis, in particular to propeller shafts, preferably in a balancing machine, with at least one attachment device adapted to be positioned longitudinally to the rotor axis and suitable for attaching a corrective element to the outer circumference of the rotor, with a stationary supply unit supplying corrective elements measured for the individual unbalance correction, and with a feeding device adapted to feed supplied corrective elements to the attachment device, said feeding device including a transfer shuttle having a receptacle for receiving a corrective element and being capable of performing reciprocating movements between the supply unit and the attachment device by means of a controllable motion drive mechanism. The present invention relates furthermore to a method of attaching corrective weights to rotors, in particular to propeller shafts, by means of such a device. 
       DESCRIPTION OF PRIOR ART 
       [0003]    Methods and devices for unbalance correction find employment in volume production in order to balance rotors, for instance, propeller shafts, economically. For this purpose, existing unbalanced conditions of the rotors are detected by means of balancing machines and then corrected by removing or applying balance weights. On some workpieces, for example, on shafts or propeller shafts, it is suitable or even necessary to perform the unbalance correction by the attachment of balance weights, using welding devices for attaching the balance weights and applying a welding process in which a corrective element forming the balance weight is welded to the workpiece. To perform such an unbalance correaction speedily and automatically, it is necessary to feed suitable corrective elements to the welding device. 
         [0004]    A balancing machine with a device of the type initially referred to is known from U.S. Pat. No. 7,441,456 B1. This known balancing machine serves to balance propeller shafts and includes a welding device which is adapted to be positioned in the axial direction of the propeller shaft in order to affix by welding metal elements to the propeller shaft to correct the determined out-of-balance condition. To accomplish this, the metal elements are severed from a metal ribbon in a forming station where they are cut to a length computed by a computer on the basis of measurement results and then shaped to an appropriate form by forming dies. The metal element thus formed is then held available by a gripper at the discharge end of the forming station. A shuttle movable on guide rails longitudinally along the balancing machine and having a vertically movable receptacle is advanced to a position beneath the gripper and picks up the metal element using an upward movement of the receptacle. The shuttle loaded with the metal element is then moved to the other end of the guide rails close to the balancing spindle. There the welding device picks up the metal element, in which process the welding electrode of the welding device is positioned to a location above the shuttle and is lowered down onto the metal element, and a pneumatic source then applies suction to disengage and hold the metal element in the electrode by vacuum while the welding device is moved to its welding position on the propeller shaft. 
         [0005]    The known device is complicated and expensive to manufacture because of the need to provide pneumatic devices on the shuttle and the welding device which have to be controllably activated for transferring and holding the metal element. Another disadvantage is that the shuttle cannot be moved into the working area of the welding device so that it is necessary for the welding device to leave its working area to pick up the metal element for welding. 
         [0006]    From U.S. Pat. No. 6,694,812 B2 a balancing machine for propeller shafts is known in which metal elements likewise severed from a ribbon for unbalance correction are welded to the propeller shaft by means of a welding device. In this disclosure, the device for cutting the metal element to length and forming it is arranged on a carriage which is movable longitudinally along the propeller shaft and also supports the welding device. As a result, the carriage is relatively heavy and requires complex feeding devices so that the traversing speed has to be kept at a low level. 
         [0007]    WO 2004/005878 A1 discloses a device for attaching corrective weights to propeller shafts or Cardan shafts in a balancing machine which includes a pliers-type device adapted to be positioned longitudinally to the rotor axis and constructed to receive several corrective weights. The pliers-type device is operable to place the corrective weights on the outer circumference of the rotor to be secured there by welding. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a device of the type initially referred to and a method which enable the corrective elements to be fed from the supply unit to the attachment device with particular ease, speed and reliability. 
         [0009]    According to the present invention, the device for feeding and attaching corrective elements for unbalance correction to rotors having a rotor axis, in particular to propeller shafts, preferably in a balancing machine comprises at least one attachment device adapted to be positioned longitudinally to the rotor axis and suitable for attaching a corrective element to the outer circumference of the rotor, and a feeding device adapted to feed corrective elements to be measured for the individual unbalance correction from a supply unit to the attachment device, said feeding device including a transfer shuttle having a receptacle for a corrective element and being capable of performing reciprocating movements between the supply unit and the attachment device on a guideway parallel to the rotor axis by means of a controllable motion drive mechanism, wherein the transfer shuttle includes a loading device configured for performing an active loading operation by extracting the corrective element from its receptacle and inserting it into the receptacle of the attachment device, and the loading device is driven to perform an active loading operation by means of the controllable motion drive mechanism of the transfer shuttle. 
         [0010]    The device of the present invention distinguishes itself by a simple and economical configuration of the feeding device. The transfer shuttle has no further driving devices apart from the motion drive mechanism nor does it need any further energy supply. Also the receptacle for accommodating the corrective element on the attachment device is a simple construction requiring no additional devices for loading the corrective element because the loading operation is performed by means of the transfer shuttle. The transfer shuttle may be of comparatively small and light-weight construction enabling it to perform rapid movements with low energy demands. 
         [0011]    According to another proposal of the invention, the guideway extends along the entire range of movement of the attachment device. Therefore, the corrective element to be attached can be moved by the transfer shuttle to any operating position of the attachment device. The movements of the attachment device may therefore be restricted to selecting the respective attachment location, thereby avoiding unnecessary movements of the attachment device which is substantially heavier and connected to power and control cables. 
         [0012]    According to still another proposal of the invention, the receptacles arranged on the transfer shuttle and on the attachment device for accommodating a corrective element are so configured and arranged that the corrective element is displaceable by the loading device in a direction parallel to the guideway from the receptacle of the transfer shuttle into the receptacle of the attachment device. In this fashion, the approaching movement of the transfer shuttle to the attachment device and the loading operation of the corrective elements can be performed in a single pass using a continuous motion process. Loading therefore requires very little time, and the risk of malfunction is extremely low in view of the simple displacement process. 
         [0013]    In a preferred embodiment, the receptacle arranged on the transfer shuttle and/or on the attachment device for receiving a corrective element includes guide bars substantially parallel to the guideway, between which bars the corrective element is adapted to be clamped in place by frictional engagement. This ensures secure holding of the corrective element on the transfer shuttle and on the attachment device, in addition to providing a guiding and secure holding function for the corrective element during the loading operation. An unsafe intermediate state in which the corrective element is temporarily released is thereby avoided. 
         [0014]    In a simple and advantageous embodiment of the device of the invention, the receptacle for accommodating a corrective element is arranged on an auxiliary slide which is mounted on the transfer shuttle for movement in a positive-engagement straight-line guide parallel to the guideway and is urged against a stop of the transfer shuttle by the force of a spring, the stop acting to limit a movement of the auxiliary slide relative to the transfer shuttle, which movement is directed toward the attachment device, and said transfer shuttle mounting a loading pushrod which extends parallel to the straight-line guide in the direction of the receptacle and is movable into the interior of the receptacle when the auxiliary slide is moved away from the stop of the transfer shuttle against the force of the spring. This construction enables in a simple manner a loading operation to be performed by means of the motion drive mechanism of the transfer shuttle, with the auxiliary slide being held fast against the attachment device during the loading operation. 
         [0015]    A particularly simple and low-cost configuration of the transfer shuttle may furthermore be accomplished by securing the loading pushrod to an upright arranged on the transfer shuttle at a distance from the auxiliary slide and by using as spring a compression spring which takes support on the upright. 
         [0016]    To enable precise and interference-free insertion of the corrective elements into the attachment device, care must be taken to ensure that the attachment device and the transfer shuttle are accurately aligned to each other. To accomplish this, it is possible according to another proposal of the invention to arrange on the auxiliary slide on the one side and on the attachment device on the other side part of a positioning device which effects an alignment of the attachment device relative to the auxiliary slide necessary for the active loading operation. The positioning device may additionally include a sensor for monitoring the positioning necessary for the loading operation. The sensor signal may be evaluated by a control device for controlling the loading operation before the loading operation is activated. 
         [0017]    To simplify the loading of the receptacle of the transfer shuttle in the supply unit, it is possible according to another proposal of the invention to arrange the receptacle of the transfer shuttle on a mounting body which is connected with the auxiliary slide in a displaceable or releasable manner and is displaceable relative to the auxiliary slide by the supply unit in such a way that a corrective element is insertable into the receptacle on the side of the mounting body facing away from the attachment device without any interference by the loading pushrod. This configuration allows an advantageous construction of the supply unit and easy loading of the transfer shuttle. An alternative embodiment may provide that the loading pushrod is movable by the supply unit into a position releasing access to the receptacle. 
         [0018]    A preferred embodiment of the invention provides that the mounting body is carried on the auxiliary slide by means of a positive-engagement cross guide and is displaceable relative to the auxiliary slide in a direction transverse to the slide&#39;s direction of movement, and that the mounting body is locked against displacement relative to the auxiliary slide by a locking device arranged on the auxiliary slide. Moreover, the locking device may be unlockable by the supply unit when the transfer shuttle reaches the loading position on the supply unit. In the loading position of the transfer shuttle on the supply unit it is also possible for the mounting body to be removable from the auxiliary slide by the supply unit and movable into a loading compartment in which a corrective element is insertable into the receptacle of the mounting body. 
         [0019]    The object initially referred to is furthermore solved by a method for feeding and attaching corrective elements for unbalance correction to rotors, in particular to propeller shafts, said method comprising the following steps: 
         [0020]    arranging at least one attachment device adapted to be positioned longitudinally to the rotor axis, with a receptacle for accommodating a corrective element attachable to the outer circumference of the rotor; 
         [0021]    arranging a stationary supply unit holding available corrective elements measured for the respective unbalance correction; 
         [0022]    arranging a feeding device with a transfer shuttle which includes a receptacle for a corrective element, and with a guideway parallel to the rotor axis on which the transfer shuttle is capable of performing reciprocating movements between the supply unit and the attachment device by means of a controllable motion drive mechanism, and forming a loading device arranged on the transfer shuttle and actuatable by the motion drive mechanism; 
         [0023]    loading the transfer shuttle arranged on the supply unit in a loading position by inserting a corrective element into the receptacle of the transfer shuttle; 
         [0024]    moving the attachment device into an attachment position on the rotor; 
         [0025]    moving the transfer shuttle by means of the motion drive mechanism until its abutment with the attachment device; 
         [0026]    performing a loading operation by driving the loading device by means of the motion drive mechanism of the transfer shuttle and extracting the corrective element from the receptacle of the transfer shuttle and inserting it into the receptacle of the attachment device; and 
         [0027]    returning the transfer shuttle to the supply unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The present invention will be explained in more detail in the following with reference to embodiments illustrated in the accompanying drawings. In the drawings, 
           [0029]      FIG. 1  is a view of a balancing machine for balancing propeller shafts; 
           [0030]      FIGS. 2 to 4  are various views of a transfer shuttle; 
           [0031]      FIG. 5  is a fragmentary view of the balancing machine of  FIG. 1 ; and 
           [0032]      FIG. 6  is a view of the supply unit of the balancing machine of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0033]      FIG. 1  shows a balancing machine  1  for balancing propeller shafts. The balancing machine includes a machine bed  2  on which two pedestals  3 ,  4  are arranged at opposite ends. Each of the pedestals  3 ,  4  has a base  31 ,  41  which is carried in a straight-line guide extending in the longitudinal direction of the machine bed  2  and is movable relative to the machine bed  2  by means of a traversing drive in order to enable the relative distance of the pedestals  3 ,  4  to be adjusted to the length of the propeller shaft to be balanced. Extending upwardly from the bases  31 ,  41  are, respectively, leaf springs  32 ,  42  arranged in pairs. Secured to the upper ends of each pair of leaf springs  32 ,  42  is a respective spindle housing  33 ,  43  each receiving a spindle mounted therein for rotation. The spindles of the spindle housings  33 ,  43  are coaxially arranged and have at their ends facing each other a respective clamping fixture  34 ,  44  for clamping a fastening end, for example, the end flange of a propeller shaft W, with precise locating accuracy. The spindle housing  33  mounts a drive motor  35  enabling the spindle and the clamping fixture  34  connected to it to be driven rotatably. The spindle in the spindle housing  43  is freely rotatable, though it may be equally equipped with a drive. Also arranged on the spindle housings  33 ,  43  are vibration sensors, not shown, which sense the vibrations generated by an unbalanced condition during a measuring run, transmitting them in the form of electrical signals to an electronic computing unit which computes therefrom location and amount of the unbalance to be corrected. 
         [0034]    Further arranged on the machine bed  2  is a support beam  6  which extends parallel to the machine bed  2  and includes a support rail  7  parallel to the axis of the spindles. The ends of the support beam  6  are secured to uprights  8  or holders which are fixedly connected with the machine bed  2 . An attachment device  9  in the form of a welding device  10  is slidably mounted on the support rail  7 . A drive mechanism  11  is operable to move the welding device  10  along the support rail  7  and to locate it in any desired position. The welding device  10  has a pair of welding tongs  12  with two arms  13 ,  14  which are movable into a position embracing the propeller shaft W and can be pressed against the propeller shaft W for welding a corrective element serving as balance weight in the form of a bent piece of sheet metal. The welding device  10  operates according to the resistance welding technique, with the arms  13 ,  14  of the welding tongs  12  forming electrodes connected to a power source during the welding operation. 
         [0035]    To present the corrective elements for unbalance correction, the balancing machine  1  has associated with it a supply unit  15  which is fixedly arranged at one end of and adjacent to the balancing machine  1 . The supply unit  15  is connected to the electronic control unit of the balancing machine  1  and configured to produce corrective elements of various sizes. To this effect, sections of different lengths predetermined by the control of the balancing machine  1  are severed from a metal ribbon and bent to a shape suitable for attachment to the propeller shaft W. 
         [0036]    To transfer the corrective elements held available by the supply unit  15  to the welding device  10 , a feeding device  16  is provided which includes a guideway  17  extending longitudinally to the balancing machine  1  and up to the supply unit  15 , and a transfer shuttle  18  movable along the guideway  17 . The guideway  17  is aligned parallel to the support rail  7  and secured to the machine bed  2  and the supply unit  15 . It includes guide rails supporting the transfer shuttle  18 , and a motion drive mechanism which is controlled by the control of the balancing machine  1  and enables a controlled linear movement of the transfer shuttle  18  along the entire guideway  17 . The motion drive mechanism may include an endless toothed belt which extends longitudinally to the guideway and is routed around idler pulleys at the ends of the guideway, with one of the idler pulleys being adapted to be driven by a position-controllable electric motor. Alternatively, the motion drive mechanism may be constructed as a linear electric motor. 
         [0037]    The transfer shuttle  18  is shown in  FIGS. 2 to 4  in various positions. The transfer shuttle  18  has a rectangular base plate  20  having secured to its underside a slide body mounted on the guideway  17 . Fitted to the upper side of the base plate  20  is a guide rail  21  parallel to the guideway  17 , which forms a positive-engagement straight-line guide for an auxiliary slide  22 . The base plate  20  has at one end thereof a fixed stop  23  to limit the movement of the auxiliary slide  22  to the end of the base plate  20 . Secured to the opposite end of the base plate  20  is an upright  24  carrying at its upper end two loading pushrods  25  spaced in a parallel relationship to each other. The lower boundary surfaces of the loading pushrods  25  facing the base plate  20  lie in a plane parallel to the base plate  20 . The auxiliary slide  22  has on its upper side facing away from the base plate  20  two mounting bodies  26  in parallel arrangement. Each mounting body defines with its upper side a receptacle  27  for a corrective element  28 . The receptacles  27  are shaped in the manner of a shallow groove which extends in the direction of movement of the auxiliary slide  22  and is defined by a middle boundary surface parallel to the base plate  20  and two lateral boundary surfaces inclined toward the middle boundary surface. The middle boundary surfaces of the receptacles  27  are spaced from the base plate  20  by a distance slightly smaller than the distance between the loading pushrods  25  and the base plate  20 . In the conveying state of the transfer shuttle  18  shown in  FIG. 2 , the middle boundary surfaces of the receptacles  27  are in a region extending the loading pushrods  25  in a straight line, so that a displacement of the auxiliary slide  22  in the direction of the upright  24  causes the loading pushrods  25  to be displaced over the middle boundary surfaces of the receptacles  27 , thereby pushing the corrective elements  28  arranged in the receptacles  27  out of the receptacles. 
         [0038]    Arranged on both longitudinal sides of the receptacles  27  are guide bars  29  having on their sides facing the receptacles  27  guide grooves  30  for engagement by the longitudinal edges of the corrective elements  28 . Moreover, the guide bars  29  are biased by means of springs, not shown, in the direction of the receptacles  27  whereby they are clamped against the corrective elements  28  to retain these in the receptacles  27  by frictional engagement. 
         [0039]    Seated between the auxiliary slide  22  and the upright  24  is a compression spring  37  surrounded in part by a sleeve  38 . The compression spring  37  is biased and serves the function of urging the auxiliary slide  22  against the stop  23 . 
         [0040]      FIG. 4  shows the transfer shuttle  18  with an auxiliary slide  22  moved up against the upright  24  in opposition to the force of the compression spring  37 . In this position of the auxiliary slide  22  which corresponds to the end of a loading operation for loading the attachment device  9 , the loading pushrods  25  extend up to, or even beyond, the end of the receptacles  27  adjacent to the stop  23 . The corrective elements  28  previously held in the receptacles  27  were therefore completely pushed out of the receptacles  27 . 
         [0041]    The mounting bodies  26  are supported on the auxiliary slide  22  by means of a positive-engagement cross guide  39  for displacement in a direction parallel to the base plate  20  and vertical to the direction of movement of the auxiliary slide  22 . As a result of this support, the mounting bodies  26  are displaceable relative to the auxiliary slide  22  from their initial position toward the side as shown in  FIG. 3 , and removable from the auxiliary slide  22  as will be explained in the following, in order to enable new corrective elements  28  to be loaded in the supply unit  15 . Arranged in the middle between the mounting bodies  26  is a spring-loaded locking device  40  causing the mounting bodies  26  to be locked against lateral displacement when they are in the initial position moved toward the middle on the auxiliary slide  22 . The locking device  40  includes an actuating rod  45  which projects beyond the upright  24 , acting in cooperation with the supply unit  15  and unlocking the locking device  40  when the transfer shuttle  18  is moved into the loading position on the supply unit  15 . 
         [0042]    As becomes apparent from  FIG. 5 , the welding tongs  12  of the welding device  10  has on its lower arm  14  two adjacent receptacles  47  for accommodating corrective elements. The receptacles  47  are constructed in the same manner as the receptacles  27  on the transfer shuttle  18  and are spaced by the same distance as these. The welding tongs  12  is movable in conventional manner by means of drives horizontally and vertically in the longitudinal direction of the rotor axis and transversely to the rotor axis. In addition, the distance between the arms  13 ,  14  is variable. For loading corrective elements, these drives operate to position the arm  14  of the welding tongs  12  in such a way that the receptacles  47  are in alignment with the receptacles  27  of the transfer shuttle  18  moved up against the arm  14  on its guideway  17 . For a precise alignment a mechanical positioning device  48  is furthermore provided, which is comprised of a conical cam arranged on the stop side of the auxiliary slide  22  and a cooperating centering opening on the arm  14 . 
         [0043]    The loading operation is started as soon as the transfer shuttle  18  with its auxiliary slide  22  abuts the arm  14  and is aligned by the positioning device  48 . In this process, the motion drive mechanism operates to move the transfer shuttle  18  further in the direction of the arm  14 . Because the arm  14  prevents the auxiliary slide  22  from following this movement, it is displaced on the transfer shuttle  18  in the direction of the upright  24 . As this occurs, the loading pushrods  25  enter the receptacles  27  on the auxiliary slide  22 , thereby urging the corrective elements  28  held in the receptacles  27  into the receptacles  47  of the arm  14 . The loading operation is terminated when the auxiliary slide  22  occupies the position shown, for example, in  FIG. 4  and the loading pushrods  25  have pushed the corrective elements  28  completely into the receptacles  47 . The end position of the loading pushrods  25  relative to the receptacles  47  of the arm  14  is determined by the controllable position of the transfer shuttle  18  and the equally controllable position of the welding tongs  12 . Accordingly, it may be controlled by means of the drive mechanism of the transfer shuttle  18  in such a way that the loaded corrective element  28  occupies a defined position in the direction of the rotor axis, for example, a center position, in the receptacle  47  of the arm  14 . 
         [0044]    Following termination of the loading operation, the transfer shuttle  18  is returned to the supply unit to be loaded there with new corrective elements. In this process, the compression spring  37  urges the auxiliary slide  22  on the transfer shuttle  18  back into the initial position in which the auxiliary slide  22  is in abutment with the stop  23 . 
         [0045]      FIG. 6  is a view of the supply unit  15  orthogonal to the direction of movement of the transfer shuttle  18 . The transfer shuttle  18  has been moved along the guideway  17  into the end position on the supply unit  15 . In this process, the locking device  40  has been moved into the unlocking position. The supply unit  15  includes symmetrically on both sides of the transfer shuttle  18  loading compartments  50 ,  51  in which loading devices  52  for the insertion of corrective elements into the receptacles  27  of the transfer shuttle  18  are arranged. For a loading operation, a gripper  53 ,  54  arranged laterally adjacent to the loading compartment  50 ,  51  and movable by a lifting cylinder in a direction transverse to the guideway  17  operates to pull the mounting body  26  along the cross guide  39  down from the auxiliary slide  22  and onto a guide rail  55  of the supply unit  15  aligned with the cross guide. To accomplish this, the gripper  53  engages a groove  56  (see also  FIG. 2 ) on the outside of the mounting body  26  while the transfer shuttle  18  is moved up against the supply unit  15 . 
         [0046]    In  FIG. 6 , the gripper  53  has pulled the left-hand mounting body  26  into the loading compartment  50 . According to the view shown in the drawing, in this position it is then possible for a corrective element cut to its proper length to be pushed from behind into the receptacle  27  of the mounting body  26 , with the mounting body  26  being held by the guide rail  55  and the gripper  53 . Upon loading, the gripper  53  returns the mounting body  26  along the guide rail  55  and the cross guide  39  to the initial position on the auxiliary slide  22 . 
         [0047]    In the operating situation shown in  FIG. 6 , the right-hand gripper  54  was not extended while the transfer shuttle  18  pulled in so that it was not in engagement with the groove  56  of the adjacent mounting body  26 . In this case, the transfer shuttle should be loaded with only one corrective element. In the loading device  52  shown in the loading compartment  51 , a corrective element  28  held available is to be seen. 
         [0048]    When the transfer shuttle  18  leaves the supply unit  15  to perform a new loading operation, the locking device  40  is automatically returned to the locking position by the force of a spring  37 , whereby the mounting bodies  26  are securely held on the auxiliary slide  22  in their initial position close to the center of the shuttle. 
         [0049]    The device described and the method to be implemented with it effect a very speedy transport of the corrective elements from the supply unit to the attachment device in addition to ensuring simple and reliable transfer of the corrective elements. The device distinguishes itself by its straightforward construction. This makes it a low-cost and easy-to-maintain item. The transfer shuttle requires no power supply, and unnecessary movements of the attachment device are avoided. The configuration of the feeding device and the supply unit is largely independent of the configuration of the balancing machine and is therefore also suitable for retrofitting existing machines. The arrangement of two receptacles lying side-by-side for receiving corrective elements enables two different corrective elements to be fed at a time, for example, for attachment to different segments of the propeller shaft which differ in diameter. 
         [0050]    It should be noted that the present invention is not limited to the embodiments described but may be implemented by numerous modifications within the scope of the claimed invention. For instance, in lieu of the mounting bodies of the auxiliary slide, the loading pushrods may be arranged for movement on the transfer shuttle in such a way as to be movable out of their position, for example, laterally, for loading the receptacles on the transfer shuttle, in order to enable access to the receptacles for the corrective elements. Furthermore, it is also possible to provide a rotary fastening of the loading bodies on the auxiliary slide instead of a cross guide. Equally, it is possible for the corrective elements to be fed from the side of the receptacles opposite the loading pushrods if the supply unit is correspondingly constructed.

Technology Category: g