Abstract:
A crank mechanism for use in a rotary printing press is capable of varying the crank stroke length while the rotary printing press is operating. A rotatable eccentric journal and an eccentric bushing are shiftable with respect to each other. A helical groove and a cooperating pin are used to shift the eccentricities of the journal and the bushing to vary the effective stroke length of the crank mechanism.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a crank mechanism with a length-adjustable crank. Adjustment of the crank length or stroke is accomplished using two concentric, relatively rotatable eccentrics. 
     DESCRIPTION OF THE PRIOR ART 
     DE-OS 17 61 389 discloses a device for adjusting a friction cylinder stroke in an ink system of a rotary printing press. Here, a crank of the crank mechanism essentially consists of an eccentric pin and an eccentric bushing seated thereon. The eccentric bushing can be pivoted in relation to the pin by means of a planetary wheel gear. 
     DE 27 10 135 B2 describes a device for setting the angle of a distribution insert. Here, a phase position between a drive shaft with a helix-shaped groove, and a drive shaft is adjusted by means of a sliding bushing. 
     DE-PS 687 918 discloses a gear for converting a back-and-forth movement into a rotary movement. 
     DE-AS 11 51 238 discloses a fine feeding adjustment device. Here, a change in the length of the crank takes place directly via two non-twistable pins, which are supported on an obliquely extending, axially displaceable control surface. 
     Neither the pins nor the control surfaces can be displaced in the axial direction in respect to each other. 
     No adjustment by means of eccentric bushings and pins, which can be pivoted in respect to each other, is provided here. 
     EP 0 480 879 A1 discloses a device for the continuous adjustment of the axial distributing movement of a distribution roller. By this, an eccentric bolt is displaced by means of an axially displaceable gear wheel. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is directed to providing a crank mechanism with a length-adjustable crank. 
     In accordance with the present invention, this object is attained by structuring the crank as two concentric, relatively rotatable eccentrics. A drive mechanism is used to shift the outer eccentric with respect to the inner eccentric on which it is supported. The inner eccentric is a journal that is eccentrically supported on a drive gear wheel. The outer eccentric is an eccentric sleeve. Relative rotation between the two varies the stroke length of the crank mechanism which they define. 
     The advantages which can be obtained by the present invention reside in particular, in that a crank mechanism with few, and easily produced components is created by the arrangement of an axially displaceable driving mechanism, for example a pin, with which a pivotable driving mechanism, for example a helix-shaped groove, works together. An effective length of the crank of the crank mechanism can be easily adjusted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention are represented in the drawings and will be described in greater detail in what follows. 
     Shown are in: 
     FIG. 1, a schematic representation of a crank mechanism in accordance with a first preferred embodiment, 
     FIG. 2, a schematic section through a crank of the crank mechanism in accordance with FIG. 1, 
     FIG. 3, a schematic representation of a crank mechanism in accordance with a second preferred embodiment, and in 
     FIG. 4, a schematic section through a crank of the crank mechanism in accordance with FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A crank mechanism for converting a rotary movement into a linear movement is used, for example, in a rotary printing press for driving oscillating distribution cylinders or doctor blade arrangements. In the preferred embodiments which follow, the crank mechanism is used for generating a stroke, in an axial direction of a distribution cylinder  3  for an inking system, or for a dampening system of a rotary printing press. The size of the stroke of the distribution cylinder  3  can be changed during the operation of the machine. 
     A journal  2  of a distribution cylinder  3  is seated in a lateral frame  1  of a rotary printing press and is supported for rotation by roller bearings  4  and is movable in the axial direction, as seen in FIG. 1. A gear driven wheel  6  is fastened, in a torsion-proof manner, on this journal  2 . This driven gear wheel  6  meshes with a first intermediate gear wheel  7 , which is seated in the lateral frame  1  and is supported for rotation by a roller bearing  8 . A second intermediate gear wheel  9  is fixedly connected with this first intermediate gear wheel  7 . A drive gear wheel  11 , which is seated in the lateral frame, is supported for rotation by a journal  12  and a roller bearing  13  and is fixedly seated in the axial direction of the journal  12 . The drive gear wheel  11  engages this second intermediate gear wheel  9 . 
     A journal  16  is eccentrically arranged on a front face  14  of the gear wheel  11 , which faces away from the lateral frame  1 . A center axis  17  of the journal  16  is eccentrically arranged, offset by an eccentricity e 16 , in respect to an axis of rotation  18  of the drive gear wheel  11 , or respectively of the journal  12 . An eccentric bushing  19  is pivotably seated on this journal  16 . A center axis  21  of a surface  22  of eccentric bushing  19  is offset by an eccentricity e 19  in respect to a center axis  23  of a bore  24  in the eccentric bushing  19 . The center axis  23  of the bore  24  of the eccentric bushing  19  lies on the center axis  17  of the journal  16 . 
     On its front face facing away from the lateral frame  1 , the eccentric bushing  19  is provided with a sleeve  26 , which extends axially away from the eccentric bushing  19  and which is centered with respect to the journal  16 , as may be seen in FIGS. 1 and 2. This sleeve  26  has two grooves  27 ,  28 , which are offset by 180° in respect to each other and which both extend in a helical manner along the axial length of sleeve  26 . 
     An axially extending bore  29  is arranged in the journal  16 ,and extends concentrically in respect to the axis of rotation  18  of the drive gear wheel  11 . A bolt  31 , which is axially movable in relation to its longitudinal axis, is seated in this bore  29 . This bolt  31  is connected with an actuating device  32  for the purpose of accomplishing movement of bolt  31  in the axial direction. In the first preferred embodiment, the actuating device  32  essentially consists of a work cylinder  33 , arranged fixed in place on the frame, whose piston is connected with the bolt  31  by means of a first coupling  34 . This first coupling  34  is rigid in the axial direction, and its two coupling halves are rotatable in respect to each other in the circumferential direction. For example, the actuating device  32  can also be designed as a positioning drive, so that the bolt  31  can be selectively positioned in a multitude of positions, for example by means of an electric motor. 
     A pin  36 , which extends past the bolt  31  on both sides and which engages the bushing grooves  27 ,  28  on both sides of the bushing sleeve  26 , is fastened in the bolt  31  in the radial direction and acts as a drive mechanism The journal  16  has two grooves  35 , which extend parallel with the bolt  31  and which are used to prevent twisting between the journal  16  and the pin  36 . The grooves  27 ,  28  and the pin  36  are matched to each other, so that the pin  36  is arranged movable in the axial direction along the grooves  27 ,  28  and has little play in the circumferential direction. 
     A spherical roller bearing  37  is fastened on the surface of the eccentric bushing  19 . This spherical roller bearing  37  is arranged in a first coupler  38 , which translates the rotary movement of the eccentric bushing  19 , acting as a crank, into an oscillating linear movement. A free end of the first coupler  38  is hingedly connected with a first lever arm  39  of a two-armed lever  41 . This lever  41  is pivotably seated in respect to the lateral frame  1 . A second lever arm  42  of this two arm lever  41  is hingedly connected with a first end of a second coupler  43 . A second end of this second coupler  43  is connected by means of a second coupling  44  with the journal  2  of the distribution cylinder. This second coupling  44  is rigid in the axial direction, and its coupling halves are rotatable in the circumferential direction. 
     The eccentric bushing  19 , acting as part of a crank  46 , drives the first coupler  38 , so that the rotary movement of the journal  12  is converted, via the journal  16  and the eccentric bushing  19 , which act as a coupler, into an oscillating linear movement of the first coupler  38 . This oscillating movement is transferred to the distribution cylinder  3  by means of the two arm lever  41 , the second coupler  43  and the coupling  44 , so that the distribution cylinder  3  performs an oscillating movement in the axial direction. 
     In a first position of the eccentric bushing  19 , in respect to the eccentrically arranged journal  16 , their eccentricities e 16  and e 19  are superimposed on each other to form a first effective eccentricity e 46  of the crank  46  constituted by the eccentric bushing  19  and by the journal  16 . 
     To adjust the stroke of the distribution cylinder  2 , the work cylinder  33  is actuated and the bolt  31  is axially moved from a first into a second position. In the course of this, movement of bolt  31 , the pin  36  slides in an axial direction along the helical grooves  27 ,  28  and turns the bushing sleeve  26 , and thus also the eccentric bushing  19  in accordance with a gradient of the grooves  27 ,  28  around an angle alpha, for example alpha=90° in the circumferential direction. The position of the eccentricity e 19 , for example e 19 −11.5 mm, of the eccentric bushing  19  in respect to the eccentricity e 16 , for example e 16 =5.4 mm, of the journal  16  is thus changed. From this change there results a second effective eccentricity e 46 ′ of the crank  46 . In accordance with a ratio between the first effective eccentricity e 46 , for example e 46 =7.5 mm, and the second effective eccentricity e 46 ′, for example e 46 ′=15 mm, the stroke h of the cylinder  3 , for example h=15 mm, is increased to h′=30 mm 
     The eccentricity e 46 , or respectively e 46 ′, corresponds to a length of the crank  46 , i.e. the effective length of the crank  46  is therefore adjustable. 
     If a positioning drive is used in place of the work cylinder  33 , a continuous stroke adjustment of the distribution cylinder  3  is also possible during the operation of the rotary printing press. 
     In a second preferred embodiment, as may be seen in FIGS. 3 and 4, a gear wheel  47 , with helical exterior gearing, is provided as the driving mechanism, and a gear wheel  48  with helical interior gearing is provided as the power take-off mechanism. The gear wheel  47  with helical exterior gearing is seated, fixed against relative twisting, on the journal  16  by means of a square bolt, and is axially movable by means of the work cylinder  33 . This gear wheel  47  with helical exterior gearing meshes with the gear wheel  48  with helical interior gearing, which is arranged at the eccentric bushing  19 . 
     If the gear wheel  47  with helical exterior gearing is axially displaced, the gear wheel  48  with helical interior gearing is rotated, so that the position of the eccentric bushing  19 , in relation to the journal  16 , is changed. 
     The eccentric journal  16  and the eccentric bushing  19  of the crank mechanism  46  can be pivoted in respect to each other using either of the first and second embodiments. The driving mechanism  36  of the first embodiment or  47  of the second embodiment, which is movable in the axial direction of the axis of rotation  18  of the crank mechanism  46  and which is fixed in the circumferential direction in relation to the axis of rotation  18  of the crank mechanism  46 , is arranged for adjusting the relative positions of the journal  16  and the eccentric bushing  19 . This driving mechanism  36  of the first embodiment or  47  of the second embodiment is arranged so it works together with a driving mechanism  27  and  28  of the first embodiment or  48  of the second embodiment, which is fixed in the axial direction of the axis of rotation  18  of the crank mechanism  46 , and is pivotable in relation to the circumferential direction of the axis of rotation  18  of the crank mechanism. 
     The eccentricities e 16 , e 19  of the journal  16  and of the eccentric bushing  19  are adjusted to each other by the driving mechanism  36  of the first embodiment or  47  of the second embodiment being moved in the axial direction. The driving mechanism  27  and  28  of the first embodiment or  48  of the second embodiment, and therefore the eccentric bushing  19 , are pivoted by this axial movement of the driving mechanism  36  of the first embodiment or  47  of the second embodiment. The size of the effective eccentric e 46  of the crank  46  is changed by this. 
     It is also possible, in the first preferred embodiment, to arrange the helix-like grooves  27 ,  28  in the bolt  31 , and the pin, or first embodiment driving mechanism  36  in the eccentric bushing  19 . In this case, the prevention of twisting of the bolt  31  must not take place in accordance with the first preferred embodiment by means of the pin  36  or first embodiment driving mechanism, but instead, for example, by means of a square bolt  49  of the second preferred embodiment as seen in FIG.  2 . 
     While preferred embodiments of a crank mechanism for use with a rotary printing press, in accordance with the present invention, have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes in, for example, the drive for the gears, the specific type of press, and the like could be made without departing from the true spirit and scope of the present invention which is accordingly to be limited only by the following claims.