Abstract:
A method and device for suppressing vibrations in a printing press includes placing, on at least one element of the press, a mass that vibrates freely with one degree of freedom, determining the rotational speed of the press and feeding the speed to a control device, and, in the control device, utilizing the rotational speed, determining an actuating variable and feeding the actuating variable to at least one actuator, at least one vibration parameter of the mass being changed in accordance with the rotational speed by the actuator.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method and a device for suppressing vibrations in a printing press, in which a freely vibrating mass is used on a vibrating element. 
     In the drive of printing presses, such as sheet-fed presses, use is made inter alia of belt and gear mechanisms. In the gear train of a cyclically printing sheet-fed press, undesired excitation of vibrations occurs at various points, the vibrations not being of integer orders, that is to say, they do not repeat once, twice, or n times per printed sheet. Such excitation leads to vibrations of the same order that, in printing terms, manifest themselves as faults whose position changes from sheet to sheet. Such printing faults, which show themselves, for example, as stripes in the printed image, are more striking than faults whose position does not change from sheet to sheet. Typical causes of such faults in sheet-fed presses are belt drives and drives for distributor rolls, which do not exhibit any integer revolution orders. 
     Printing presses are generally driven by electric motors. The drive torque from an electric motor is fed through a belt drive into a gear train, from which the cylinders, drums, and rolls in the printing units are driven. Existing in the prior art is the determination of disruptive vibrations, for example, on a cylinder, by using a sensor and driving one or more electric motors such that the vibrations are reduced. In addition, active absorbers can be provided, which are likewise driven in a vibration-compensating manner. The drawback is the high outlay for determining the disruptive vibrations. In order to register the vibrations at all points at which they are produced, a large number of active absorbers would have to be used in addition to a large number of sensors. 
     Printing presses can be configured such that odd-numbered excited vibrations are avoided to the greatest possible extent. If a belt drive is used in the gear train, it is, in principle, not possible, because of the slip that is naturally present, to implement this over the entire speed range. In the case of sheet-fed presses, there are generally revolving elements in the area of the inking units that, as compared with the sheet-carrying cylinders, revolve with non-integer orders. Construction measures to keep the vibration excitation small by predefining appropriate tolerances are subject to fabrication limits. For example, the faults originating from a belt or the round running properties of distributor rolls can be reduced or improved only with increased design effort. 
     A printing press, as a structure capable of vibrating, exhibits natural resonances. One way of reducing undesired vibrations is to move resonances with odd-numbered orders into a non-critical speed range. In the case of sheet-fed presses, for example, the belt length in belt drives can be dimensioned suitably. The variation in the belt length has its limits in the overall space that is available and in the effect on the machine dynamics resulting from a longer and therefore softer belt. A further way lies in the use of an absorber matched to the natural frequency of a machine, as described in German Published, Non-Prosecuted Patent Application DE 199 14 613 A1. 
     East German Patent No. DD 130 321 A1 describes a device for absorbing torsional vibrations in the drive of presses, in which a pendulum is rotatably connected to one or more axes of rotation of a drive. The pendulum is matched to a specific excitation order of the rotational frequency range of the drive. The mass of rotation and stiffness of the pendulum are not changed. 
     German Published, Non-Prosecuted Patent Application DE 40 33 278 A1, corresponding to U.S. Pat. No. 5,235,909 to Gerstenberger et al., shows a device for damping flexural vibrations of printing-unit cylinders in which, in the printing-unit cylinder, one or more broadband-tuned dampers are provided, whose natural frequencies correspond to those of the respective printing-unit cylinder and that are deflected by centrifugal force in antiphase with the printing-unit cylinder. The mass of rotation and stiffness of the dampers remains constant. 
     Such systems, used in horizontally mounted cylinders, operate optimally only in a rotational speed range in which the force of gravity that acts can be neglected as compared with the centrifugal forces. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a method and device for suppressing vibrations in a printing press that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that develop their action over the entire rotational speed range with little outlay. 
     With the foregoing and other objects in view, there is provided, in accordance with the invention, a method of suppressing vibrations in a printing press, including the steps of providing a mass vibrating freely with one degree of freedom on at least one element of the press, determining a rotational speed of the press and supplying the determined rotational speed to a control device, determining an actuating variable dependent upon the rotational speed with the control device and supplying the actuating variable to at least one actuator with the control device, and changing at least one vibration parameter of the mass with the actuator dependent upon the determined rotational speed. 
     The nub of the invention is that, on at least one element excited to vibrate in a printing press, a freely vibrating mass is used, at least one vibration parameter of the mass being changed continuously as a function of rotational speed by an actuator. At least one vibration parameter of the mass is set such that the frequency of the critically exciting vibration of the element of the press corresponds to the natural frequency of the freely vibrating mass. 
     The invention is suitable both for absorbing torsional and flexural vibrations. The system including actuator and vibration absorbing mass is used as far as possible on the element excited to vibrate or on an element in its immediate vicinity. 
     In accordance with another mode of the invention, a stiffness of the mass is changed with the actuator. 
     In accordance with a further mode of the invention, inertia of the mass is changed with the actuator. 
     With the objects of the invention in view, there is also provided a method of suppressing vibrations in a printing press, including the steps of providing a mass vibrating freely with one degree of freedom on at least one element of the press, determining a rotational speed of the press and supplying the determined rotational speed to a control device, and determining an actuating variable in the control device utilizing the rotational speed and supplying the actuating variable to at least one actuator, at least one vibration parameter of the mass being changed by the actuator dependent upon the rotational speed. 
     With the objects of the invention in view, there is also provided a device for suppressing vibrations in a printing press having at least one element, including a freely vibrating mass vibrating freely with one degree of freedom to be coupled to the at least one element, the mass having at least one vibration parameter, a rotational speed measuring configuration for determining a rotational speed of the press, an actuator connected to the mass for changing the vibration parameter, and a control device connected to the rotational speed measuring configuration and to the actuator. 
     In accordance with an added feature of the invention, the element has an axle, the mass displaceable on the axle, and at least one leaf spring is disposed parallel to the axle and is coupled to the element and the mass. 
     In accordance with an additional feature of the invention, there is provide an axle, the mass being displaceable on the axle, and at least one leaf spring disposed parallel to the axle and coupled to the element and the mass. 
     In accordance with yet another feature of the invention, the element is a revolving element having a radial direction, and the mass is displaceable in the radial direction of the revolving element. 
     In accordance with yet a further feature of the invention, an inhomogeneous, elastic rotating body is coupled to the actuator, rotates about an axis, and is coupled to the element and the mass. 
     In accordance with yet an added feature of the invention, the actuator is at least one electromagnet. 
     In accordance with yet an additional feature of the invention, the actuator is at least one pneumatic element. 
     In accordance with again another feature of the invention, the element is a revolving element and the actuator revolves with the revolving element. 
     In accordance with again a further feature of the invention, the press has a frame and the actuator is to be fixed to the frame. 
     In accordance with again an added feature of the invention, the actuator is disposed at the mass. 
     In accordance with again an additional feature of the invention, the actuator is disposed on the mass. 
     With the objects of the invention in view, in a printing press having at least one element, there is also provided a device for suppressing vibrations, including a freely vibrating mass vibrating freely with one degree of freedom coupled to the element, the mass having at least one vibration parameter, a rotational speed measuring configuration for determining a rotational speed of the press, an actuator connected to the mass for changing the vibration parameter, and a control device connected to the rotational speed measuring configuration and to the actuator. 
     Other features that are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a method and device for suppressing vibrations in a printing press, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic side view of a press having two absorbers according to the invention; 
     FIG. 2 is a diagrammatic side view of an embodiment of an absorber of FIG. 1, 
     FIG. 3A is a plan view of a first embodiment of an absorber according to the invention with an axially displaceable mass; 
     FIG. 3B is a fragmentary, cross-sectional view of the absorber of FIG. 3A; 
     FIG. 4A is a plan view of a second embodiment of an absorber according to the invention with a radially displaceable mass; 
     FIG. 4B is a fragmentary, cross-sectional view of the absorber of FIG. 4A; 
     FIG. 5A is a plan view of a third embodiment of an absorber according to the invention with a rotatable elastomer body; 
     FIG. 5B is a fragmentary, cross-sectional view of the absorber of FIG. 5A; 
     FIG. 6A is a plan view of a fourth embodiment of an absorber according to the invention with an electromagnetic actuator; 
     FIG. 6B is a fragmentary, cross-sectional view of the absorber of FIG. 6A; 
     FIG. 7A is a plan view of a fourth embodiment of an absorber according to the invention with a pneumatic actuator; and 
     FIG. 7B is a fragmentary, cross-sectional view of the absorber of FIG.  7 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a press having four printing units  2 - 5 . The press contains a gear train including gears  6 - 16 , which engage in one another. To drive the press  1 , a motor  17  is provided, which is connected to a belt mechanism  18  that includes a small belt pulley  19 , a large belt pulley  20 , and a belt  21 . Seated on the shaft of the large belt pulley  20  is pinion  22  that is engaged with the gear  11 . The gear  16  is connected to gears  23 - 26 , which serve to drive distributor rolls. The printing units  2 ,  3 ,  5  are constructed in an analogous way to the printing unit  4 . A rotary encoder  27  coupled to the gear  13  is connected to a control device  28 . 
     As FIG. 2 illustrates, an absorber  30 , which is connected to the control device  28  (see FIG.  1 ), is provided coaxially with the shaft  29  of the pinion  22  and the belt pulley  20 . A further absorber  31  is situated on the gear  16  for the distributor drive. The absorber  31  is, likewise, connected to the control device  28 . 
     The rotational speed of the press  1  is determined by the rotary encoder  27  and fed to the control device  28 . The rotational speeds of all the elements revolving through the gear train  6 - 16  and  23 - 26  are proportional to the rotational speed of the gear  13 . The measured values relating to the rotational speed of the press  1  are present in the control device  28  and are processed there to form actuating variables for actuators that are constituent parts of the absorbers  30 ,  31 . The actuating variables are transmitted to the actuators through the connection to the absorbers  30 ,  31 . The actuating variables in each case have the effect on the actuators of changing, as a function of the rotational speed, a vibration parameter of a mass that is, likewise, a constituent part of the respective absorber  30 ,  31 . The absorber  30  compensates for undesired vibrations that originate from the belt drive  18 . The absorber  31  suppresses undesired vibrations that are caused by reciprocating distributor rolls. 
     Exemplary embodiments of absorbers  30 ,  31  will be described in the following text. 
     FIGS. 3A and 3B show a revolving element  32  in a press  1 , such as the belt pulley  20  or the gear  16  (FIG.  1 ). The mounting and drive of the element  32  are not further illustrated. The element  32  is excited by undesired rotational vibrations and, to absorb such vibrations, an absorber mass  33  in the shape of a cylindrical disk is provided. The absorber mass  33  is mounted in a bearing  34  such that it can rotate freely about an axis  35 , which coincides with the axis of rotation of the element  32 . The bearing  34  is seated on a guide piece  36 , which can be displaced in the direction of the axis  35  on a journal  37  that is disposed on the element  32 . To displace the guide piece  36  and, therefore, the absorber mass  33 , a linear actuator  38  is provided, such as an operating cylinder. The absorber mass  33  has three apertures  39 ,  40 ,  41  that are disposed to be offset by 120 degrees and through which trapezoidal leaf springs  42 ,  43 ,  44  project, which are fixed to the front side  45  of the element  32  in the direction parallel to the axis  35 . The leaf springs  42 ,  43 ,  44  are respectively guided on both sides without play in the apertures  39 ,  40 ,  41  by rollers  46 ,  47 ,  48 ,  49 ,  50 ,  51 . 
     Depending on the rotational speed of the press  1 , the distance x of the front side  52  of the absorber mass  33  in relation to the front side  45  of the element  32  is set by the actuator  38 . The stiffness k B  of a leaf spring  42 ,  43 ,  44  depends on the distance x. The natural frequency ω T  of the absorber mass  33  is given by:          ω   T     =         3        k   B         J   T                                
     where J T  designates the moment of inertia of the absorber mass  33 . The natural frequency ω T  can, therefore, be set suitably by setting the distance x such that disruptive excitation frequencies on the element  32  are suppressed. 
     FIGS. 4A and 4B show a further exemplary embodiment of an absorber  30 ,  31 . There is a journal  54  disposed at a revolving element  53 . The element  53  is subject to disruptive rotational vibrations. To suppress such vibrations, a nonvariable absorber mass  55  and a variable-radius absorber mass  56  are provided. The absorber mass  55  is retained on the journal  54  by a bearing  57  such that it can rotate. Front sides  58 ,  59  of the element  53  and of the disk-like absorber mass  55  are connected by an elastomer spring  60  having a torsional stiffness of k E . The absorber mass  55  has a hub  61 , to which a guide rod  62  is fixed. The guide rod  62  is located in the radial direction  63  at right angles to the axis of rotation  64  of the element  53  and of the absorber mass  55 ,  56 . The absorber mass  56  is retained such that it can be displaced on the guide rod  62 . To displace the absorber mass  56  in the radial direction  63 , an actuator  65  is provided that, for example, is configured as an operating cylinder, the piston of the operating cylinder being coupled to the absorber mass  56 . 
     In the case of the absorber configuration according to FIGS. 4A and 4B, the moment of inertia J T  is given by: 
       J   T   =J   1   +J   2,A   +m·x   2   
     where: 
     J 1  is the moment of inertia of the absorber mass  55 ; 
     J 2  is the moment of inertia of the absorber mass  56  and of the actuator  65 ; 
     m is the variable-radius mass of the absorber mass  56  and of the actuator  65 ; and 
     x is the distance of the absorber mass  56  from the axis of rotation  64 . 
     The distance x of the absorber mass  56 , and, therefore, the natural frequency of the absorber configuration, is set by the actuator  65  in accordance with the rotational speed of the press  1  such that the disruptive rotational vibrations on the element  53  are suppressed. For the absorber configuration, the result is a natural frequency ω T  according to the following relationship:          ω   T     =         k   E       J   T                                
     In a variant according to FIGS. 5A and 5B, an absorber mass  66  is freely rotatably mounted in a bearing  69  on a journal  67  of a revolving element  68 . The absorber mass  66  is secured by securing rings  70 ,  71  against displacement in the direction of the axis of rotation  72  of the element  68  or the absorber mass  66 . To absorb rotational vibrations on the element  68 , the absorber mass  66  is provided with an aperture  73 . In the aperture  73 , a cylindrical elastomeric body  74  is mounted such that it can rotate about an axis  75 . The elastomeric body  73  rests without play on side faces  76 ,  77  running radially on the aperture  73 . The elastomeric body  74  has in the interior cavities  78 ,  79 , whose cross-section increases and decreases in the circumferential direction around the axis  75 . The elastomeric body  74  is coupled to a rotational actuator  80 , with which the elastomeric body  74  can be rotated about the axis  75 . Because of the cavities  78 ,  79 , the torsional stiffness k E  of the elastomeric body  74  with respect to the rotation about the axis of rotation  72  changes with the rotational angle φ of the elastomeric body  74  in the aperture  73 . 
     Depending on the rotational speed of the press  1 , the rotational position φ of the elastomeric body  74  in the aperture  73  is changed by the actuator  80 . The natural frequency ω T  of the absorber configuration that is established is given by          ω   T     =         k   E       J   T                                
     where J T  is the moment of inertia of the absorber mass  66  and of the elastomeric body  74 . 
     FIGS. 6A and 6B show an exemplary embodiment having an electromagnetic order absorber. To absorb rotational vibrations on a revolving element  81 , an absorber mass  82  made of a ferrous material is provided, which is rotatably mounted on a journal  84  of the element  81  by a bearing  83  and which is secured by securing rings  85 ,  86  against displacement on the journal  84 . The absorber mass  82  has rectangular apertures  87 ,  88 , only two being shown in FIG.  6 A. Situated in the apertures  87 ,  88  are electromagnets  89 ,  90 , which are connected to an adjustable current source  91 . The current in the electromagnets  89 ,  90  produces a magnetic field, which exerts a force such that, in each case, there is an air gap between the electromagnets  89 ,  90  and the side faces  92 ,  93 ,  94 ,  95 , which is also maintained while the element  81  is rotating. The system including the absorber mass  82 , the electromagnets  89 ,  90  fixed to a front face  96 , and the air gaps forms a torsion spring, whose stiffness k L  depends directly on the coil current in the electromagnets  89 ,  90 . The current source  91  constitutes an actuator with which, depending on the rotational speed of the press  1 , the current and, therefore, the stiffness k L  is changed. The result for such an absorber configuration is a natural frequency that counteracts disruptive excitation frequencies on the element  81  in a compensatory manner. 
     According to FIGS. 7A and 7B, to absorb rotational vibrations on a revolving element  96 , use is made of an absorber mass  97  that is mounted such that it can rotate on a journal  99  of the element  96  by a bearing  98  and that is secured by securing rings  100 ,  101  against displacement in the direction of the axis of rotation  102 . As viewed in the circumferential direction, the disk-like absorber mass  97  has apertures  103 ,  104 , of which only two are shown in FIG.  7 A. Supporting plates  105 ,  106 , which are fixed to a front face  107  of the element  96  project into the apertures  103 ,  104 . Air bags  110 ,  111  are respectively provided between a side face  108 ,  109 , located in the circumferential direction, of an aperture  103 ,  104  and a supporting plate  105 ,  106 , the internal pressure of the air bags  110 ,  111  being adjustable by a pressure control system  112  that is accommodated in the element  96 . By setting the pressure in the air bags  110 ,  111  as a function of the rotational speed, the natural frequency of the absorber configuration can be set to suppress disruptive excitation vibrations. Together with the supporting plates  105 ,  106  and the absorber mass  97 , the air bags  110 ,  111  form a spring system whose stiffness k L  depends on the pressure in the air bags  110 ,  111 .