Abstract:
A device for separating sheet material has an actuator and a sheet material holder coupled thereto. The actuator is designed for moving the sheet material holder. The sheet material holder is designed for receiving an individual sheet material piece from a sheet material stack in which the sheet material pieces are arranged in a layered manner one above another along a vertical direction. The actuator is designed to set the sheet material holder into an oscillating rotational movement about a rotation axis that lies substantially parallel to the vertical direction, in order to receive the individual sheet material piece from the sheet material stack.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
       [0001]    This application is a National Phase Patent Application of International Patent Application Number PCT/EP2015/064081, filed on Jun. 23, 2015, which claims priority of each of the European Patent Application EP114175196.6, filed on Jul. 1, 2014, and of the European Patent Application EP14196274.6, filed on Dec. 4, 2014. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a device for singularizing sheet material. 
         [0003]    A device of the generic type for singularizing sheet material has an actuator and a sheet-material receiver coupled thereto. The actuator is configured for repositioning the sheet-material receiver, for example in such a manner that the sheet-material receiver is set in a translatory motion or in a rotary motion. For example, a previously known sheet-material receiver is designed in the manner of a roller. The sheet-material receiver herein is configured for receiving an individual sheet-material piece from a sheet-material stack, wherein in which sheet-material stack has a multiplicity of sheet-material pieces that is disposed in a layered manner on top of one another along a plumb-line direction. 
         [0004]    The sheet material may be paper sheets, cardboard sheets, for example, or paper securities, for example bank notes, currency notes, checks, or the like. A respective sheet-material stack thus comprises a stack of paper securities, paper sheets, or cardboard sheets, for example. 
         [0005]    A device of the generic type for singularizing sheet material is described in WO 2014/005715 A1, for example. The sheet-material receiver therein is configured in the shape of an oscillating conveyor belt by way of which individual sheet-material pieces may be retrieved from a sheet-material stack. However, the conveyor belt does not engage the topmost sheet-material piece of the sheet-material stack, but the lowermost sheet-material piece of the sheet-material stack. The sheet-material pieces are thus drawn from the lower side of the sheet-material stack by the oscillating conveyor belt. 
         [0006]    It is an object of the present invention to provide a means that permits secure and reliable singularization of sheet material. 
         [0007]    This technical object is achieved by the subject matter described herein. 
       SUMMARY 
       [0008]    According to the invention, it is provided that the actuator is configured for setting the sheet-material receiver in an oscillating rotary motion about a rotation axis that lies substantially parallel with the plumb-line direction, so as to receive the individual sheet-material piece from the sheet-material stack. The individual sheet-material piece is preferably the topmost or lowermost sheet-material piece of the sheet-material stack. 
         [0009]    The sheet material is, for example, paper sheets, cardboard sheets, paper securities such as bank notes, currency notes, checks or similar. The sheet-material stack preferably has a multiplicity of sheet-material pieces of the same type. This facilitates controlling of the actuator. The sheet-material pieces of the sheet-material stack are configured, for example, so as to be of a rectangular box shape, each having one length, one width, and one height, wherein the height of the respective sheet-material piece is a fraction of the length and of the width, as is the case with currency notes, for example. 
         [0010]    The actuator comprises, for example, electromechanical means which are actuatable in order for the sheet-material receiver to be set in said oscillating rotary motion about the rotation axis. The exact design embodiment of the actuator will be discussed in more detail at a later point. 
         [0011]    The oscillating rotary motion about the rotation axis extends along an angular range of less than 10°, for example. The angular range is approximately 1°, for example. Accordingly, the actuator is configured, for example, for rotating the sheet-material receiver about the rotation axis by approximately 1°, and subsequently for causing a rotary motion in the opposite direction. 
         [0012]    The frequency of the oscillating rotary motion is preferably greater than 1 kHz. For example, the frequency of the oscillating rotary motion is approximately 40 kHz. The frequency of the oscillating rotary motion is preferably determined so as to depend on the height of the individual sheet-material piece. For example, the frequency is proportional to a reciprocal value of the height. 
         [0013]    In the case of a further embodiment of the device, the actuator is configured for setting the sheet-material receiver in a translatory motion along the plumb-line direction, so as to press the sheet-material receiver for receiving the individual sheet-material piece onto a surface of the individual sheet-material piece at a specific force. For example, the actuator positions the sheet-material receiver above the sheet-material stack, so as to thereupon press the sheet-material receiver onto a central point, for example onto a centerpoint, of the topmost sheet-material piece. 
         [0014]    The sheet-material receiver, by virtue of the oscillating rotary motion thereof about the rotation axis and by virtue of a force exerted by the actuator for pressing the sheet-material receiver onto the surface of the individual sheet-material piece, is preferably configured for initiating an attractive force between the sheet-material receiver and the individual sheet-material piece, so as to remove the individual sheet-material piece from the sheet-material stack. For example, contact, for example a so-called surface-to-flexible-surface contact, is initiated between the sheet-material piece and the individual sheet-material piece to be received and to be removed, said contact initiating the generating of the attractive force. By way of the initiated attractive force it is possible for the individual sheet-material piece to be removed from the sheet-material stack. For this purpose, the actuator is preferably configured for setting the sheet-material receiver in a translatory motion along a first direction that lies substantially perpendicular to the plumb-line direction, so as to remove the received individual sheet-material piece from the sheet-material stack, wherein the first direction preferably lies substantially perpendicular to a longitudinal side of the individual sheet-material piece. Alternatively or additionally thereto, it is preferable for the actuator to be configured for setting the sheet-material receiver in a translatory motion along a second direction that lies substantially perpendicular to the plumb-line direction, so as to remove the received sheet-material piece from the sheet-material stack, wherein the second direction preferably lies substantially parallel with the longitudinal side of the individual sheet-material piece. 
         [0015]    For example, the actuator is configured for initially positioning the sheet-material receiver above the sheet-material stack, so as to thereupon press the sheet-material receiver onto the surface of the topmost sheet-material piece. Prior, during, or thereafter, the actuator sets the sheet-material receiver in said oscillating rotary motion. On account thereof, the attractive force is initiated between the distal end of the sheet-material receiver that lies on the surface of the sheet-material piece, and the surface of the individual sheet-material piece. The topmost sheet-material piece of the sheet-material stack thus adheres to the distal end of the sheet-material receiver. While maintaining the oscillating rotary motion, a translatory motion along said first direction and/or along the second direction and/or along the plumb-line direction is performed, such that only the topmost sheet-material piece of the sheet-material stack is removed from the sheet-material stack and is fed to a sheet-material collection container or to a sheet-material input device and/or to a sheet-material output device, for example. 
         [0016]    The sheet-material receiver, at the distal end thereof that during positioning of the sheet-material receiver above the sheet-material stack points to the surface of the topmost sheet-material piece, preferably has a receiving head. Furthermore, a coupling element for coupling to the actuator is preferably provided at the proximal end of the sheet-material receiver. The coupling element is preferably designed in such a manner that the actuator is configured for setting the sheet-material receiver in said oscillating rotary motion. 
         [0017]    For example, the sheet-material receiver, in terms of the mass distribution thereof and/or in terms of the dimensions thereof, in relation to the rotation axis is configured so as to be rotationally symmetrical, for example so as to be substantially cylindrical. No or at most a minor imbalance force is created by virtue of the rotationally symmetrical configuration of the sheet-material receiver during the oscillating rotary motion. 
         [0018]    The receiving head that is provided at the distal end of the sheet-material receiver may have a convex, a planar, or a concave circumferential profile. For example, the sheet-material receiver at the distal end thereof is designed so as to be rounded, that is to say convex or concave, for example in such a manner that the receiving head is configured so as to be approximately spherical-symmetrical in relation to a reference point that lies on the rotation axis. The contact face between the surface of the topmost sheet-material piece of the sheet-material stack and the sheet-material receiver, by virtue of the approximately spherical-symmetrical configuration of a convex receiving head of the sheet-material receiver, is comparatively minor. 
         [0019]    In the case of a further preferred embodiment, the sheet-material receiver for contacting the individual sheet-material piece has an elastic material. The elastic material is silicone, for example, or another rubber-type material, for example an elastomer. The elastic material has a hardness of approximately 30 to 95 Shore A, for example, approximately 40 Shore A, for example. 
         [0020]    In the case of an exemplary embodiment, the sheet-material receiver has a main body from a first material, and a coating applied thereto from a second material, wherein the second material contains the elastic material. The coating is provided on the receiving head, for example, and is designed as a surface coating, for example. For example, the main body is designed so as to be substantially cylindrical, having a length of approximately 10 mm and a radius of approximately 5 mm, wherein the thickness of the coating is approximately 0.5 mm, for example. 
         [0021]    The sheet-material receiver is preferably coupled to the actuator by way of a fixed bearing. The actuator has a rotary element and a translatory element, for example. The translatory element is configured for setting the sheet-material receiver in said oscillating rotary motion. Repositioning of the sheet-material receiver along the plumb-line direction is preferably performed by way of the translatory element of the actuator. The coupling element of the sheet-material receiver is preferably coupled to the rotary element of the actuator. The translatory element and the rotary element of the actuator are preferably intercoupled by way of a rotary joint. 
         [0022]    The device has a control unit for controlling the actuator, for example. The control unit is configured, for example, for providing control signals according to a control program and for feeding said control signals to the actuator, said actuator transforming said control signals into mechanical movements and thus setting the sheet-material receiver in said oscillating rotary motion and/or translatory motion. 
         [0023]    Furthermore, the device may have a movably mounted coupling piece which couples the actuator to a base that is installed in a locationally fixed manner. For example, the coupling piece is mounted so as to be movable in said first and/or second direction, the latter two being perpendicular to the plumb-line direction, and is likewise actuated by the control unit. In the case of this example, the positioning of the sheet-material receiver may be performed above the topmost sheet-material piece of the sheet-material stack, by means of the coupling piece, wherein the actuator and the sheet-material receiver herein are not moved in relation to the coupling piece. The actuator and the sheet-material receiver are only moved in relation to the coupling piece for pressing the sheet-material receiver onto the surface of the topmost sheet-material piece, and for setting the sheet-material receiver in said oscillating rotary motion. 
         [0024]    The method according to independent patent claim  16  forms a further aspect of the present invention. The method according to the invention for singularizing sheet material shares the advantages of the device according to the invention for singularizing sheet material, and has preferred embodiments which correspond to the above-described preferred embodiments of the device of the first aspect of the present invention, in particular as said preferred embodiments are defined in the dependent claims. To this extent reference is made to what has been discussed hereabove. 
         [0025]    It is particularly preferable for the method to comprise positioning of the sheet-material receiver above the sheet-material stack, and pressing of the sheet-material receiver onto the surface of the topmost sheet-material piece of the sheet-material stack, and setting of the sheet-material receiver in the oscillating rotary motion about the rotation axis that lies substantially parallel with the plumb-line direction, so as to receive and remove the individual sheet-material piece from the sheet-material stack. In this case, the sheet-material receiver is set in the oscillating rotary motion before pressing, during pressing or after pressing the sheet-material receiver onto the topmost sheet-material piece. 
         [0026]    The subject matter of the present invention is suitable for singularizing sheet material of any type. In particular, the subject matter of the present invention may be employed for singularizing paper securities, such as currency notes or bank notes. 
         [0027]    One advantage of the present invention lies in particular in that the singularization of sheet material may be performed in a secure and reliable manner, using few components. In particular, the singularization of sheet material may be performed without a friction partner having to be provided in the case of the device, which friction partner prevents those sheet-material pieces that lie below the topmost sheet-material piece from being conjointly removed when the topmost sheet-material piece is being received by the sheet-material receiver. 
         [0028]    In the case of the above explanation of the device and of the method for singularizing sheet material, it has always been assumed that the sheet-material receiver engages the topmost sheet-material piece of the sheet-material stack. However, it is also possible for the sheet-material receiver to engage the lowermost sheet-material piece of the sheet-material stack. In the case of this variant, the sheet-material receiver is pressed onto the lower side of the lowermost sheet-material piece and is likewise set in said oscillating rotary motion. This variant thus has preferred embodiments that correspond to the above-described preferred embodiments of the present invention, in particular as said embodiments are defined in the dependent claims. To this extent, reference is made to what has been discussed hereabove. 
         [0029]    The concept underlying the invention is to be explained in more detail hereunder by means of the exemplary embodiments that are illustrated in the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  shows a schematic cross-sectional view of three sheet-material pieces. 
           [0031]      FIG. 2  shows a perspective and schematic view of a device for singularizing sheet material. 
           [0032]      FIG. 3  shows a schematic cross-sectional view of the device shown in  FIG. 2 . 
           [0033]      FIG. 4  shows a further schematic cross-sectional view of the device shown in  FIG. 2 . 
           [0034]      FIGS. 5A-C  show schematic cross-sectional views of a sheet-material receiver in the device shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 2  to  FIG. 4  show schematic views of a device  1  for singularizing sheet material.  FIG. 2  shows the device  1  in a perspective view, and  FIG. 3  and  FIG. 4  show the device in cross-sectional views. 
         [0036]    The device  1  is designed for singularizing sheet material. Specifically, it is intended that individual sheet-material pieces  5 - 1  to  5 - n  that are disposed in a layered manner on top of one another along a plumb-line direction y and thus configure a sheet-material stack  5  are singularized. To this end, the device  1  comprises a sheet-material receiver  12  which is driven by an actuator  11  of the device  1 . The actuator  11  thus sets the sheet-material receiver  12  in specific motions, as will be explained in more detail at a later point. A schematic cross-sectional view of this sheet-material receiver  12  is shown in  FIG. 5 . 
         [0037]    In order for the configuration of the device  1  for singularizing sheet material, and for a method for singularizing sheet material, to be explained, reference is made hereunder to all  FIGS. 2 to 5 . It is to be subsequently explained in an exemplary manner by means of  FIG. 1  how specific control parameters for operating the device  1  may be calculated. 
         [0038]    The actuator  11  has a translatory element  111  and a rotary element  112 . The actuator  11  is actuated by a control unit (not shown in the figures) of the device  1 . 
         [0039]    The translatory element  111  is configured for repositioning the sheet-material receiver  12  along the plumb-line direction y, and the sheet-material receiver is set in an oscillating rotary motion about a rotation axis r that lies parallel with the plumb-line direction y by way of the rotary element  112  of the actuator  11 . 
         [0040]    Moreover, the actuator  11 , having the translatory element  111  and the rotary element  112 , is disposed so as to be movable along a first direction x that lies substantially perpendicular to the plumb-line direction y, and/or a second direction z, such that a received sheet-material piece  5 - 1  may be removed from the sheet-material stack  5  in the x-direction or the z-direction. 
         [0041]    The sheet-material stack  5  is, for example, a stack of paper sheets, cardboard sheets, paper securities (for example bank notes, currency notes, or checks), or similar sheet-shaped media. Said media is disposed in a layered manner on top of one another along the plumb-line direction y, thus configuring the sheet-material stack  5 . Each of the sheet-material pieces  5 - 1  to  5 - n  in the example shown has the same length L, the same width B, and the same height H. However, the subject matter of the present invention does not require that all sheet-material pieces  5 - 1  to  5 - n  have the same dimensions. 
         [0042]    In order for an individual sheet-material piece, specifically the topmost sheet-material piece  5 - 1 , to be received, the actuator  11 , having the sheet-material receiver  12  coupled thereto, is initially positioned above the sheet-material stack  5 . Thereafter, the actuator  11  presses the sheet-material receiver  12  onto a surface  51  of the topmost sheet-material piece  5 - 1 , for example onto a central point of the topmost sheet-material piece  5 - 1 , as is schematically shown in  FIG. 2 . Thereafter, the actuator  11  by means of the translatory element  111  presses the sheet-material receiver  12  onto the surface  51  of the topmost sheet-material piece  5 - 1  at a specific force. Prior, during, or after pressing the sheet-material receiver  12  onto the surface  51 , the actuator  11  by means of the rotary element  112  sets the sheet-material receiver  12  in an oscillating rotary motion about the rotation axis r. 
         [0043]    The oscillating rotary motion about the rotation axis r extends across an angular range of less than 10°. For example, the actuator  11  rotates the sheet-material receiver  12  by an angle           of 1° about the rotation axis r along a rotation direction rr. Thereafter, the actuator  11  sets the sheet-material receiver  12  in a rotation by 1° along the opposite rotation direction rr, repeating this procedure at a specific frequency. This oscillating rotary motion is performed at a frequency of greater than 1 kHz, for example. The frequency is approximately 20 to 40 kHz, for example. The frequency is determined so as to depend on the height H of the individual sheet-material piece  5 - 1 , for example. For example, the frequency is proportional to a reciprocal value of the height H of the individual sheet-material piece  5 - 1 . This will be explained in more detail at a later point with reference to  FIG. 1 . 
         [0044]    With reference to  FIGS. 5A-C , exemplary potential design embodiments of the sheet-material receiver  12  are to be discussed in more detail initially. The sheet-material receiver  12  at the proximal end thereof comprises a coupling element  121  which in  FIG. 5  is illustrated in only a schematic manner. The sheet-material receiver  12  by way of the coupling element  121  is coupled to the rotary element  112  of the actuator  11 . 
         [0045]    The sheet-material receiver  12  is designed so as to be substantially cylindrical, in particular thus so as to be rotationally symmetrical in relation to the rotation axis r. The sheet-material receiver  12  at the distal end thereof has a receiving head  122 . 
         [0046]    In the case of the example shown in  FIG. 5A , the receiving head  122  is designed so as to be spherical-symmetrical and convex in relation to a reference point P that lies on the rotation axis r. In other words, the receiving head  122 , and thus the distal end of the sheet-material receiver  12 , has a convex circumferential profile. The surface of the receiving head  122  may thus be designed in such a manner that each point lying thereon has the same distance R, which consequently corresponds to a spherical radius, with respect to the reference point P. This spherical radius R is established so as to depend on the application or on the type of sheet material, respectively. 
         [0047]    In the case of the example corresponding to  FIG. 5A , the sheet-material receiver  12  has a main body  12 - 1  that is molded from a first material, and a coating  12 - 2  from a second material that differs from the first material. The second material of the coating  12 - 2  comprises an elastic material, for example silicone or another rubber-type material. The first material of the main body  12 - 1  of the sheet-material receiver  12  has an elasticity that is lower than the elasticity of the material of the coating  12 - 2 . The coating  12 - 2  in the case of the example shown is provided only on the receiving head  122 , and has a minor thickness of one millimeter or less than one millimeter, for example 0.5 mm. 
         [0048]    However, the sheet-material receiver  12  at the distal end thereof does not necessarily have to have a convex circumferential profile and/or said coating  12 - 2 . In the case of the variant according to  FIG. 5B , the receiving head  122 , and thus the distal end of the sheet-material receiver  12 , has a substantially planar circumferential profile, and, in the variant according to  FIG. 5C , the receiving head  122 , and thus the distal end of the sheet-material receiver  12 , has a substantially convex circumferential profile. 
         [0049]    Depending on the type of the sheet-material piece  5 - 1 , . . . ,  5 - n  to be received, one specific circumferential profile of the receiving head  122  may be more expedient than another. Notwithstanding the sheet-material receiver  12  in  FIG. 3  and  FIG. 4  being shown having a receiving head  122  having a convex circumferential profile, the exemplary embodiments therein are not limited to such a receiving head  122 . Rather, the receiving head  122  also in the case of the examples according to  FIG. 3  and  FIG. 4  may have a substantially planar or a concave circumferential profile. 
         [0050]    Once the actuator  11  has pressed the sheet-material receiver  12  onto the surface  51  of the topmost sheet-material piece  5 - 1 , and has set the sheet-material receiver  12  in said oscillating rotary motion, the topmost sheet-material piece  5 - 1  is repositioned by a first distance Δ 1  in the x-direction, and a sheet-material piece  5 - 2  lying therebelow is repositioned by a second distance Δ 2 . It can be clearly seen in  FIG. 4  that the first distance Δ 1  is significantly greater than the second distance Δ 2 . 
         [0051]    Ultimately, the contact pressure of the sheet-material receiver  12  and the oscillating rotary motion of the sheet-material receiver  12  enable the removal of the topmost sheet-material piece  5 - 1  from the sheet-material stack  5 . The actuator  11 , while maintaining the oscillating rotary motion of the sheet-material receiver  12 , may draw the topmost sheet-material piece  5 - 1  from the sheet-material stack  5 , and convey said topmost sheet-material piece  5 - 1  to a sheet-material output device (not shown in the figures), for example. Upon delivery of the conveyed sheet-material piece  5 - 1 , the actuator  11  returns to the sheet-material stack  5  and proceeds in the same way with the next sheet-material piece  5 - 2 . 
         [0052]    The sheet-material receiver  12 , by virtue of the oscillating rotary motion thereof about the rotation axis r, and by virtue of the force exerted by the actuator  11  for pressing the sheet-material receiver  12  onto the surface  51  of the topmost sheet-material piece  5 - 1 , is thus configured for initiating an attractive force between the sheet-material receiver  12  and the individual sheet-material piece  5 - 1 , such that the individual sheet-material piece  5 - 1  may be removed from the sheet-material stack  5 . 
         [0053]    In order for the frequency of the oscillating rotary motion of the sheet-material receiver  12  to be determined, the following procedure may be followed, for example: The sheet-material stack  5  is modeled as a monolithic bar having a rectangular cross section. This bar comprises n imaginary elements, wherein n corresponds to the number of individual sheet-material pieces  5 - 1  to  5 - n,  each element corresponding to one sheet-material piece. Of these n elements, the elements i−1, i, and i+1, which thus in an exemplary manner represent three sheet-material pieces  5 - 1 ,  5 - 2 , and  5 - 3 , lying on top of one another, are illustrated in  FIG. 1 . 
         [0054]    By means of the equation 1 
         [0000]        M·{umlaut over (φ)}+K·φ= 0 with  M, K ∈              n*n    (1)
 
         [0000]    eigenmodes of this bar are determined. In the equation (1)
   M refers to a mass matrix,   K refers to a rigidity matrix,   φ refers to a twisting angle of an element (sheet-material piece about the rotation axis r), and   {umlaut over (φ)} refers to the second temporal derivation of φ.   
 
         [0059]    Equations of motion are established in order for the mass matrix M and the rigidity matrix K to be determined. A respective connection between the individual n imaginary elements is modulated as a torsion spring having a rigidity c. This rigidity c results from the following equations 2 for a twisting angle of an element subjected to torsion: 
         [0000]    
       
         
           
             
               
                 
                   ϕ 
                   = 
                   
                     
                       
                         T 
                         · 
                         
                           d 
                           
                             G 
                             · 
                             
                               I 
                               t 
                             
                           
                         
                       
                       → 
                       T 
                     
                     = 
                     
                       
                         
                           
                             
                               G 
                               · 
                               
                                 I 
                                 t 
                               
                             
                             d 
                           
                           · 
                           ϕ 
                         
                         → 
                         c 
                       
                       = 
                       
                         
                           G 
                           · 
                           
                             I 
                             t 
                           
                         
                         d 
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0060]    In the equation (2)
   T refers to the torque of torsion   G refers to the shear modulus   I t  refers to the area moment of inertia   d refers to the length of the bar   
 
         [0065]    The equation of motion  3  results for the i th  element (sheet-material piece): 
         [0000]        J   i ·{umlaut over (φ)} i   +c· (φ i −φ i+1 )+ c· (φ i −φ i−1 )=0 with 1 ≦i&lt;n    (3)
 
         [0000]    wherein J refers to a rotary inertia, and the following equation 4 results for the n th  equation of motion: 
         [0000]        J   i ·{umlaut over (φ)} i   +c· (φ i −φ i−1 )=0   (4)
 
         [0000]    In the case of a sheet-material stack having three sheet-material pieces (n=3), the mass matrix M and the rigidity matrix K result as follows: 
         [0000]    
       
         
           
             M 
             = 
             
               
                 
                   [ 
                   
                     
                       
                         J 
                       
                       
                         0 
                       
                       
                         0 
                       
                     
                     
                       
                         0 
                       
                       
                         J 
                       
                       
                         0 
                       
                     
                     
                       
                         0 
                       
                       
                         0 
                       
                       
                         J 
                       
                     
                   
                   ] 
                 
                  
                 
                     
                 
                  
                 and 
                  
                 
                     
                 
                  
                 K 
               
               = 
               
                 [ 
                 
                   
                     
                       
                         2 
                         · 
                         c 
                       
                     
                     
                       
                         - 
                         c 
                       
                     
                     
                       0 
                     
                   
                   
                     
                       
                         - 
                         c 
                       
                     
                     
                       
                         2 
                         · 
                         c 
                       
                     
                     
                       
                         - 
                         c 
                       
                     
                   
                   
                     
                       0 
                     
                     
                       
                         - 
                         c 
                       
                     
                     
                       c 
                     
                   
                 
                 ] 
               
             
           
         
       
     
         [0066]    By means of the complete description of the bar by way of the two matrices M and K, the natural frequencies together with the respective eigenmodes that are described by the eigenvectors may be determined. For example, a calculation is performed using the following parameters which are reflected in the table: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                 Formula 
                   
                   
                   
               
               
                 indicator 
                 Variable 
                 Value 
                 Unit 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 φ i   
                 Twisting angle of the i th   
                   
                   
               
               
                   
                 element (sheet-material 
                   
                   
               
               
                   
                 piece) 
                   
                   
               
               
                 n 
                 Number of elements lying on 
                 60 
                   
               
               
                   
                 top of one another (sheet- 
                   
                   
               
               
                   
                 material pieces) 
                   
                   
               
               
                 m 
                 Mass of an individual 
                 0.001125 
                 kg 
               
               
                   
                 element (sheet-material 
                   
                   
               
               
                   
                 piece) 
                   
                   
               
               
                   
               
               
                 G 
                 Shear modulus 
                 300000 
                 
                   
                     
                       
                         N 
                         
                           m 
                           2 
                         
                       
                     
                   
                 
               
               
                   
               
               
                 B 
                 Width of an individual 
                 0.075 
                 m 
               
               
                   
                 element (sheet-material 
                   
                   
               
               
                   
                 piece) 
                   
                   
               
               
                 L 
                 Length of an individual 
                 0.15 
                 m 
               
               
                   
                 element (sheet-material 
                   
                   
               
               
                   
                 piece) 
                   
                   
               
               
                 I t   
                 Area moment of inertia to 
                 0.0000144842 
                 m 4   
               
               
                   
                 torsion 
                   
                   
               
               
                 k 
                 Computation coefficient 
                 0.22888542 
                   
               
               
                 H 
                 Height of an individual 
                 0.001 
                 m 
               
               
                   
                 element (sheet-material 
                   
                   
               
               
                   
                 piece) 
                   
                   
               
               
                 J 
                 Rotary inertia 
                 0.00000263672 
                 kg m 2   
               
               
                 C 
                 Rigidity torsion spring 
                 4345.26 
                 Nm 
               
               
                   
               
             
          
         
       
     
         [0067]    By means of this data, for example by means of the equation (2) and the values in the table, it may be determined that the frequency of the oscillating rotary motion is to be 40.595 kHz, for example, in order for the topmost sheet-material piece  5 - 1  to be removed from the sheet-material stack  5 , without the remaining sheet-material pieces  5 - 2  to  5 - n  being removed conjointly from the sheet-material stack  5 . In particular, it is also possible for the frequency of the oscillating rotary motion to be determined independently of the number n of the sheet-material pieces  5 - 1  to  5 - n.  Numerical values and computation methods stated above are to be understood as being merely exemplary, of course. 
         [0068]    In the case of the above explanation of the device and of the method for singularizing sheet material, it has always been assumed that the sheet-material receiver  12  engages the topmost sheet-material piece  5 - 1  of the sheet-material stack  5 . However, it is also possible for the sheet-material receiver  12  to engage the lowermost sheet-material piece  5 - n  of the sheet-material stack  5 . In the case of this variant, the sheet-material receiver  12  is pressed onto the lower side of the lowermost sheet-material piece  5 - n  and is likewise set in said oscillating rotary motion about the rotation axis r. 
       LIST OF REFERENCE SIGNS/ABBREVIATIONS USED 
       [0000]    
       
           1  Device for singularizing sheet material 
           11  Actuator 
           12  Sheet-material receiver 
           12 - 1  Main body 
           12 - 2  Coating 
           121  Coupling element 
           122  Receiving head 
           5  Sheet-material stack 
           5 - 1 , . . . ,  5 - n  Sheet-material pieces 
           51  Surface of the topmost sheet-material piece  5 - 1   
         B Width of an individual sheet-material piece 
         L Length of an individual sheet-material piece 
         H Height of an individual sheet-material piece 
         r Rotation axis 
         rr Direction of the oscillating rotary motion (Rotation direction) 
         R Spherical radius 
         P Reference point on the rotation axis r 
         x x-axis/first direction 
         y y-axis/plumb-line direction 
         z z-axis/second direction 
         Δ 1  First distance 
         Δ 2  Second distance