Adjusting device for the lateral ink distribution on printing presses
United States Patent 3916791
A printing press having a plate cylinder, drive train and form roller, with a set of rollers for feeding a film of ink to the form roller, at least one of which is axially vibrated, or reciprocated, endwise, the reciprocating mechanism being driven by the drive train. A phase changer is interposed between the drive train and the reciprocating mechanism, the phase changer having an input shaft and an output shaft with means for angularly offsetting the shafts with respect to one another to adjust the phase position. The adjusting means is in two parts, a rotary portion which rotates with the shafts of the phase changer and a setting portion which is stationary so that the relative phase of the shafts may be varied while the shafts rotate.
US Patent References:
Printer and slotter
Langston et al. - March 1932 - 1850800
Printer and slotter
Langston et al. - March 1932 - 1850802
Rotary printing machine
Gangler - September 1934 - 1973058
Ink roller vibrator
Crafts et al. - May 1950 - 2506778
Variable stroke reciprocating mechanism
Ward et al. - February 1963 - 3077159
Printer and slotter
Langston et al. - March 1932 - 1850800
Printer and slotter
Langston et al. - March 1932 - 1850802
Rotary printing machine
Gangler - September 1934 - 1973058
Ink roller vibrator
Crafts et al. - May 1950 - 2506778
Variable stroke reciprocating mechanism
Ward et al. - February 1963 - 3077159
Application Number:
05/370054
Publication Date:
11/04/1975
Filing Date:
06/14/1973
View Patent Images:
Export Citation:
Assignee:
Roland Offsetmaschinenfabrik Faber & Schleicher AG
Primary Class:
Other Classes:
101/DIG.038, 101/350.300
International Classes:
B41F7/40; B41F31/15; B41F7/00; B41F31/00; B41L27/08
Field of Search:
101/348,349,350,248,247,DIG.14,141
US Patent References:
Primary Examiner:
Burr, Edgar S.
Assistant Examiner:
Hirsch, Paul J.
Attorney, Agent or Firm:
Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.
Claims:
What is claimed is
1. In a lithographic printing press the combination comprising a plate cylinder having an associated blanket cylinder, a drive train therefor, a form roller on the plate cylinder, an ink fountain, a set of rollers defining an ink path from the fountain to the form roller, at least one roller in the set being mounted for endwise vibration, a reciprocating mechanism coupled to the vibrated roller for converting the rotary motion of the drive train to endwise movement of the vibrated roller, the reciprocating mechanism being coupled to the drive train for reciprocating the vibrated roller with a particular amplitude of throw and in a particular phase relation with the drive train and hence with the plate cylinder, a phase changer interposed between the drive train and reciprocating mechanism, the phase changer having an input shaft and an output shaft driven by said drive train arranged coaxially end to end with respect to the input shaft, said output shaft driving said reciprocating mechanism, said phase changer including, coupling means for coupling together said ends, the coupling means including means for angularly offsetting the shafts with respect to one another with an infinitely variable angle, and adjusting means for the offsetting means to vary the degree of offset, said adjusting means having a rotary portion which rotates with the input and output shafts and a setting portion which is stationary with respect to the printing press, said setting portion having means to move said rotary portion relative to said ends while said printing press is in operation so that the relative phase of the input and output shafts may be varied while the shafts rotate thereby to enable immediate observation in the printed result of a change in the phase of the vibration of the vibrated roller with respect to the rotary phase of the plate cylinder, the phase changer being independent from the reciprocating mechanism to the extent that movement of the setting portion of the adjusting means produces a change in the phase of said at least one roller relative to the plate cylinder, without producing any change in the amplitude of throw imparted to said at least one roller by the reciprocating mechanism.
1. In a lithographic printing press the combination comprising a plate cylinder having an associated blanket cylinder, a drive train therefor, a form roller on the plate cylinder, an ink fountain, a set of rollers defining an ink path from the fountain to the form roller, at least one roller in the set being mounted for endwise vibration, a reciprocating mechanism coupled to the vibrated roller for converting the rotary motion of the drive train to endwise movement of the vibrated roller, the reciprocating mechanism being coupled to the drive train for reciprocating the vibrated roller with a particular amplitude of throw and in a particular phase relation with the drive train and hence with the plate cylinder, a phase changer interposed between the drive train and reciprocating mechanism, the phase changer having an input shaft and an output shaft driven by said drive train arranged coaxially end to end with respect to the input shaft, said output shaft driving said reciprocating mechanism, said phase changer including, coupling means for coupling together said ends, the coupling means including means for angularly offsetting the shafts with respect to one another with an infinitely variable angle, and adjusting means for the offsetting means to vary the degree of offset, said adjusting means having a rotary portion which rotates with the input and output shafts and a setting portion which is stationary with respect to the printing press, said setting portion having means to move said rotary portion relative to said ends while said printing press is in operation so that the relative phase of the input and output shafts may be varied while the shafts rotate thereby to enable immediate observation in the printed result of a change in the phase of the vibration of the vibrated roller with respect to the rotary phase of the plate cylinder, the phase changer being independent from the reciprocating mechanism to the extent that movement of the setting portion of the adjusting means produces a change in the phase of said at least one roller relative to the plate cylinder, without producing any change in the amplitude of throw imparted to said at least one roller by the reciprocating mechanism.
Description:
In the operation of printing presses, and in particular multi-color lithograph presses, adjustment is as much an art as a science. My studies show that one of the little-appreciated variable factors which affects the quality of the printing is the phasing of the vibration of a vibrating roller with respect to the angular position of the plate cylinder. Provision has been made in the past for changing such phasing, but this has required stopping the press and making an increment of a change in one direction or the other. The direction and amount of change has been a matter of pure speculation and it has been impractical to optimize this adjustment or to determine the effect of an interplay between the phase adjustments in the inking systems for the various colors of a colored reproduction.
It is, accordingly, an object of the present invention to provide an improved means for imparting an infinitely variable phase adjustment to the vibration of the vibrating rollers while the press is in operation so that the result of making a change can be immediately noted and so that with immediate corrective action the phase adjustment may be optimized.
It is another object of the present invention to provide means for changing the phase adjustment which permits extremely fine and accurate gradations and in which the phase, once set, is positively locked without any possibility of occurrence of creep even during a long press run.
It is more specifically an object of the present invention to provide a phase adjuster which may be interposed either between the plate cylinder and the reciprocating mechanism or between the main drive shaft and the reciprocating mechanism, making the improvement applicable not only to new designs of presses but to existing presses already in the field.
It is yet another object of the invention to provide a printing press which permits running adjustment of phase position of all or a portion of the vibrated rollers at extremely low cost and without in any way affecting the integrity and reliability of the press drive.
Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:
FIG. 1 is a diagram showing a typical plate and blanket cylinder with associated form roller and set of rollers defining an ink path from the ink fountain.
FIG. 2 is a diagram in the form of a plan view corresponding to a portion of FIG. 1 and showing the present invention with the phase changer of the invention being driven by the plate cylinder and showing an alternate form of drive.
FIG. 3 is a diagram showing a preferred form of phase changer using differential gearing.
FIG. 4 is a diagram showing a phase changer employing planetary gearing.
FIG. 5 is a diagram showing a phase changer employing adjustable sleeves.
FIGS. 6 and 7 are diagrams in the form of sections looking along the line 6,7--6,7 in FIG. 5 and showing two different slot arrangements.
Whle the invention has been described in connection with certain preferred embodiments, it will be understood that I do not intend to be limited to the particular embodiments shown but intend, on the contrary, to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.
Turning now to FIG. 1 of the drawings there is disclosed an outline form, by way of example, elements of a typical lithograph press including a plate cylinder P and blanket cylinder B (the impression cylinder not being shown). In rolling engagement with the plates on the plate cylinder is a form roller F which is, conventionally, rubber covered. Riding on the surface of the form roller is a vibrated roller V 1 . The roller V 1 receives ink from a rubber roller R which has, riding upon its surface, a second vibrated roller V 2 . The rubber roller R rolls in contact with an ink drum D. The latter, either directly, or more usually through a series of additional rollers, is fed from fountain F. The plate and blanket cylinders are driven by a drive shaft DS and a drive connection may be made in the conventional way to the set of rollers which transmit the ink except that in the usual case the form roller runs free, being driven by friction rather than by positive drive connection. It will be understood that the rollers shown in FIG. 1 are for illustrative purposes only and that the number and arrangement of rollers in this figure may vary over wide limits independently of the invention to be described.
For the purpose of smoothly distributing the ink film along the length of the rollers in the ink feed path, the vibrated rollers V 1 and V 2 , in addition to being rotated, are coupled to a reciprocating mechanism. Such reciprocating mechanism, indicated at 10, has an input shaft 11 and an output crank 12. Conventionally, the input shaft may be powered either from the shaft of the adjacent plate cylinder P or from the main press drive shaft or, indeed, from elsewhere in the drive train. In any event, rotation of the shaft 11 causes reciprocation of the crank 12 so that the vibrated roller V 1 is reciprocated, or "vibrated" endwise through a desired length of stroke. For the purpose of vibrating the associated roller V 2 , the vibrated rollers may be interconnected by means of a rocker 13 which is centrally pivoted at 14 on the press frame.
In accordance with the present invention a phase changer is interposed between the drive train and the reciprocating mechanism 10, the phase changer having an input shaft and an output shaft arranged coaxially end to end. For coupling the ends of the shafts together a coupling means is used which permits the shafts to be angularly offset with respect to one another. Adjusting means is provided having a rotary portion which rotates with the shafts and a setting portion which is stationary so that the relative phase position of the input and output shafts may be varied while the shafts rotate, thereby to change the phase of the vibration with respect to the associated plate cylinder. A typical phase changer which may be employed in carrying out the invention is shown, in diagrammatic form, at 20 in FIG. 3. It will be noted, first of all, that the device has an input shaft 21 and an output shaft 22. The input shaft is journaled, with respect to a stationary housing 23, by means of bearings 24 while the output, or driven, shaft is journaled in bearings 25. The shafts are arranged coaxially end to end and preferably have a third bearing 26 between them.
Keyed to the input shaft 21 is an input bevel gear 27. Keyed to the output shaft is an oppositely faced bevel gear of the same pitch diameter, 28. Running in mesh between them is a stationary equalizing bevel gear 29 which is mounted for free rotation upon a stub shaft 30. It will be understood that during operation the stub shaft 30 is stationary with respect to the housing but, in carrying out the invention, provision is made for mounting the stub shaft so that it is swingable to a selected radial position about the common axis of the input and output shafts. This is brought about in the present instance by mounting the stub shaft upon a toothed segment 31 having a bearing 32 to keep the same centered with respect to the input shaft. The position of the segment is determined by an adjustable spindle indicated at 33. In a practical case the toothed segment may be the segment of a worm wheel and the spindle 33 may be formed with a worm and journaled stationarily in the housing.
It will be apparent that rotating the worm 33 brings about a fine and precise change in the relative phasing of the output shaft with respect to the input shaft. Such change may be visualized by considering the input shaft as a reference, that is, held stationary while the worm 33 is turned. This will produce swinging movement of the stub shaft 30 and a "walking" of the idler gear 29 upon the teeth of the input bevel gear 27. As a result of the combined bodily shift of the idler gear, and its rotation, the output bevel gear 28 will be rotated to a new phase position. The same change in phase position occurs with the input and output shafts rotating. It will be noted that a portion of the phase adjusting means, namely, the worm and worm wheel segment, remains relatively stationary with respect to the housing during normal rotation of the shafts. As a result, it is possible, and, indeed, highly desired to rotate the worm 33 to bring about a change in phase position of the output shaft while the press is in operation. Stated in other words, it is possible, while the press is running, to rotate the worm 33 to change the phase of the stroke of vibration of the vibrated rollers with respect to the angular phase of the plate cylinder. Thus, with a change made on an infinitely variable basis with the press running, the effect of the change can be monitored on the printed product which is being produced and the adjustment may be varied in direction and amount until the printed product is of optimum quality. As far as is known, this is the first time that this monitoring plus corrective adjustment may be done under actual printing conditions and with immediately observeable result. Moreover, when printing in full color, the phase of the vibrating rollers in the units of different color may be changed in a coordinated fashion, again with continuous monitoring to optimize the interplay between the adjustments.
While the invention has been described in connection with a phase changer of the differential type, it will be understood by one skilled in the art that the invention is not limited to this and that other equivalent gearing arrangements may be employed. Thus referring to FIG. 4 a unit is shown which employs planetary gearing and the same numbers have been used to indicate corresponding elements, with addition of subscript a. Accordingly, the device 20a has an input shaft 21a and an output shaft 22a arranged coaxially end to end in a housing 23a, the shafts being journaled in bearings 24a, 25a, respectively, and with a bearing 26a interposed between them. Secured to the input shaft is a ring gear 27a. Centered within the latter is an output gear 28a. Interposed between the two is a stationary equalizing idler gear 29a mounted upon a stub shaft 30a. The stub shaft is supported upon a segment 31a which is maintained coaxially on the output shaft by a bearing 32a. The segment preferably comprises a portion of worm wheel engaged by a spindle in the form of a worm 33a stationarily journaled in the housing.
The operation is analogous to the device set forth in FIG. 3. That is, rocking the segment 31a with respect to the housing by means of worm 33a shifts the relative phase position between the input shaft 21a and output shaft 22a.
In accordance with one of the aspects of the invention it is not necessary to employ gearing to achieve a shift in phase position and the same may be accomplished by relatively shiftable sleeves as disclosed in FIGS. 5-7 where corresponding elements are indicated by corresponding numerals with addition of subscript b. Thus the phase shifter, generally indicated at 20b, includes input and output shafts 21b, 22b, respectively mounted, in coaxial relation, in bearings 24b, 25b in housing 23b. Formed in the input shaft is a first slot 27b. A cooperating slot 28b is formed in a sleeve 26b which is keyed to the output shaft. The slots are arranged at an angle to one another, with at least one of them being helically disposed, as set forth in FIGS. 6 and 7. The slots are engaged, in common, by a pin 29b, the pin serving to define the crossing point of the slots and hence the relative phase position of the shafts.
For the purpose of mounting the pin for endwise adjustment, thereby to change the slot coordinants, an axially slideable adjusting sleeve 30b is provided having a collar 31b. Embracing the collar, and stationarily, but adjustably, mounted in the housing is an adjusting head 32b which is threadedly engaged by a threaded adjusting spindle 33b which, while rotatable, is held captive against endwise movement. Consequently, by turning the presented outer end of the spindle 33b the head 32b is axially moved in one direction or the other to vary the axial position of the pin 29b thereby to bring about relative changes in rotational phase between the input and output shafts, just as in the embodiments earlier described. It will be noted that a portion of the adjusting means, namely the collar 30b, is rotatable with the shafts while a second portion, namely the head 32b, is relatively stationary so that it can be acted upon while the shafts are in normal rotation making it possible to monitor and optimize the phasing of the vibration of the vibrating rollers.
While the above description has assumed that the input shaft of the phase changer is directly driven from the printing cylinder P (FIG. 2), it will be understood that the connection to the shaft of the plate cylinder may, if desired, be broken and a connection, diagrammatically illustrated at 40, to the main drive shaft substituted therefor. Since the plate cylinder P is driven by, and has a fixed phase relation to, the main drive shaft of the press, coupling the phase changer to the main drive shaft will not result in any operational change. And since, in a color press, all of the color units are driven by, and accurately phased to, the main drive shaft, the vibrated rollers for the respective colors will remain in adjusted phase position, not only with respect to their individual plate cylinders, but with respect to each other.
It is, accordingly, an object of the present invention to provide an improved means for imparting an infinitely variable phase adjustment to the vibration of the vibrating rollers while the press is in operation so that the result of making a change can be immediately noted and so that with immediate corrective action the phase adjustment may be optimized.
It is another object of the present invention to provide means for changing the phase adjustment which permits extremely fine and accurate gradations and in which the phase, once set, is positively locked without any possibility of occurrence of creep even during a long press run.
It is more specifically an object of the present invention to provide a phase adjuster which may be interposed either between the plate cylinder and the reciprocating mechanism or between the main drive shaft and the reciprocating mechanism, making the improvement applicable not only to new designs of presses but to existing presses already in the field.
It is yet another object of the invention to provide a printing press which permits running adjustment of phase position of all or a portion of the vibrated rollers at extremely low cost and without in any way affecting the integrity and reliability of the press drive.
Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:
FIG. 1 is a diagram showing a typical plate and blanket cylinder with associated form roller and set of rollers defining an ink path from the ink fountain.
FIG. 2 is a diagram in the form of a plan view corresponding to a portion of FIG. 1 and showing the present invention with the phase changer of the invention being driven by the plate cylinder and showing an alternate form of drive.
FIG. 3 is a diagram showing a preferred form of phase changer using differential gearing.
FIG. 4 is a diagram showing a phase changer employing planetary gearing.
FIG. 5 is a diagram showing a phase changer employing adjustable sleeves.
FIGS. 6 and 7 are diagrams in the form of sections looking along the line 6,7--6,7 in FIG. 5 and showing two different slot arrangements.
Whle the invention has been described in connection with certain preferred embodiments, it will be understood that I do not intend to be limited to the particular embodiments shown but intend, on the contrary, to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.
Turning now to FIG. 1 of the drawings there is disclosed an outline form, by way of example, elements of a typical lithograph press including a plate cylinder P and blanket cylinder B (the impression cylinder not being shown). In rolling engagement with the plates on the plate cylinder is a form roller F which is, conventionally, rubber covered. Riding on the surface of the form roller is a vibrated roller V 1 . The roller V 1 receives ink from a rubber roller R which has, riding upon its surface, a second vibrated roller V 2 . The rubber roller R rolls in contact with an ink drum D. The latter, either directly, or more usually through a series of additional rollers, is fed from fountain F. The plate and blanket cylinders are driven by a drive shaft DS and a drive connection may be made in the conventional way to the set of rollers which transmit the ink except that in the usual case the form roller runs free, being driven by friction rather than by positive drive connection. It will be understood that the rollers shown in FIG. 1 are for illustrative purposes only and that the number and arrangement of rollers in this figure may vary over wide limits independently of the invention to be described.
For the purpose of smoothly distributing the ink film along the length of the rollers in the ink feed path, the vibrated rollers V 1 and V 2 , in addition to being rotated, are coupled to a reciprocating mechanism. Such reciprocating mechanism, indicated at 10, has an input shaft 11 and an output crank 12. Conventionally, the input shaft may be powered either from the shaft of the adjacent plate cylinder P or from the main press drive shaft or, indeed, from elsewhere in the drive train. In any event, rotation of the shaft 11 causes reciprocation of the crank 12 so that the vibrated roller V 1 is reciprocated, or "vibrated" endwise through a desired length of stroke. For the purpose of vibrating the associated roller V 2 , the vibrated rollers may be interconnected by means of a rocker 13 which is centrally pivoted at 14 on the press frame.
In accordance with the present invention a phase changer is interposed between the drive train and the reciprocating mechanism 10, the phase changer having an input shaft and an output shaft arranged coaxially end to end. For coupling the ends of the shafts together a coupling means is used which permits the shafts to be angularly offset with respect to one another. Adjusting means is provided having a rotary portion which rotates with the shafts and a setting portion which is stationary so that the relative phase position of the input and output shafts may be varied while the shafts rotate, thereby to change the phase of the vibration with respect to the associated plate cylinder. A typical phase changer which may be employed in carrying out the invention is shown, in diagrammatic form, at 20 in FIG. 3. It will be noted, first of all, that the device has an input shaft 21 and an output shaft 22. The input shaft is journaled, with respect to a stationary housing 23, by means of bearings 24 while the output, or driven, shaft is journaled in bearings 25. The shafts are arranged coaxially end to end and preferably have a third bearing 26 between them.
Keyed to the input shaft 21 is an input bevel gear 27. Keyed to the output shaft is an oppositely faced bevel gear of the same pitch diameter, 28. Running in mesh between them is a stationary equalizing bevel gear 29 which is mounted for free rotation upon a stub shaft 30. It will be understood that during operation the stub shaft 30 is stationary with respect to the housing but, in carrying out the invention, provision is made for mounting the stub shaft so that it is swingable to a selected radial position about the common axis of the input and output shafts. This is brought about in the present instance by mounting the stub shaft upon a toothed segment 31 having a bearing 32 to keep the same centered with respect to the input shaft. The position of the segment is determined by an adjustable spindle indicated at 33. In a practical case the toothed segment may be the segment of a worm wheel and the spindle 33 may be formed with a worm and journaled stationarily in the housing.
It will be apparent that rotating the worm 33 brings about a fine and precise change in the relative phasing of the output shaft with respect to the input shaft. Such change may be visualized by considering the input shaft as a reference, that is, held stationary while the worm 33 is turned. This will produce swinging movement of the stub shaft 30 and a "walking" of the idler gear 29 upon the teeth of the input bevel gear 27. As a result of the combined bodily shift of the idler gear, and its rotation, the output bevel gear 28 will be rotated to a new phase position. The same change in phase position occurs with the input and output shafts rotating. It will be noted that a portion of the phase adjusting means, namely, the worm and worm wheel segment, remains relatively stationary with respect to the housing during normal rotation of the shafts. As a result, it is possible, and, indeed, highly desired to rotate the worm 33 to bring about a change in phase position of the output shaft while the press is in operation. Stated in other words, it is possible, while the press is running, to rotate the worm 33 to change the phase of the stroke of vibration of the vibrated rollers with respect to the angular phase of the plate cylinder. Thus, with a change made on an infinitely variable basis with the press running, the effect of the change can be monitored on the printed product which is being produced and the adjustment may be varied in direction and amount until the printed product is of optimum quality. As far as is known, this is the first time that this monitoring plus corrective adjustment may be done under actual printing conditions and with immediately observeable result. Moreover, when printing in full color, the phase of the vibrating rollers in the units of different color may be changed in a coordinated fashion, again with continuous monitoring to optimize the interplay between the adjustments.
While the invention has been described in connection with a phase changer of the differential type, it will be understood by one skilled in the art that the invention is not limited to this and that other equivalent gearing arrangements may be employed. Thus referring to FIG. 4 a unit is shown which employs planetary gearing and the same numbers have been used to indicate corresponding elements, with addition of subscript a. Accordingly, the device 20a has an input shaft 21a and an output shaft 22a arranged coaxially end to end in a housing 23a, the shafts being journaled in bearings 24a, 25a, respectively, and with a bearing 26a interposed between them. Secured to the input shaft is a ring gear 27a. Centered within the latter is an output gear 28a. Interposed between the two is a stationary equalizing idler gear 29a mounted upon a stub shaft 30a. The stub shaft is supported upon a segment 31a which is maintained coaxially on the output shaft by a bearing 32a. The segment preferably comprises a portion of worm wheel engaged by a spindle in the form of a worm 33a stationarily journaled in the housing.
The operation is analogous to the device set forth in FIG. 3. That is, rocking the segment 31a with respect to the housing by means of worm 33a shifts the relative phase position between the input shaft 21a and output shaft 22a.
In accordance with one of the aspects of the invention it is not necessary to employ gearing to achieve a shift in phase position and the same may be accomplished by relatively shiftable sleeves as disclosed in FIGS. 5-7 where corresponding elements are indicated by corresponding numerals with addition of subscript b. Thus the phase shifter, generally indicated at 20b, includes input and output shafts 21b, 22b, respectively mounted, in coaxial relation, in bearings 24b, 25b in housing 23b. Formed in the input shaft is a first slot 27b. A cooperating slot 28b is formed in a sleeve 26b which is keyed to the output shaft. The slots are arranged at an angle to one another, with at least one of them being helically disposed, as set forth in FIGS. 6 and 7. The slots are engaged, in common, by a pin 29b, the pin serving to define the crossing point of the slots and hence the relative phase position of the shafts.
For the purpose of mounting the pin for endwise adjustment, thereby to change the slot coordinants, an axially slideable adjusting sleeve 30b is provided having a collar 31b. Embracing the collar, and stationarily, but adjustably, mounted in the housing is an adjusting head 32b which is threadedly engaged by a threaded adjusting spindle 33b which, while rotatable, is held captive against endwise movement. Consequently, by turning the presented outer end of the spindle 33b the head 32b is axially moved in one direction or the other to vary the axial position of the pin 29b thereby to bring about relative changes in rotational phase between the input and output shafts, just as in the embodiments earlier described. It will be noted that a portion of the adjusting means, namely the collar 30b, is rotatable with the shafts while a second portion, namely the head 32b, is relatively stationary so that it can be acted upon while the shafts are in normal rotation making it possible to monitor and optimize the phasing of the vibration of the vibrating rollers.
While the above description has assumed that the input shaft of the phase changer is directly driven from the printing cylinder P (FIG. 2), it will be understood that the connection to the shaft of the plate cylinder may, if desired, be broken and a connection, diagrammatically illustrated at 40, to the main drive shaft substituted therefor. Since the plate cylinder P is driven by, and has a fixed phase relation to, the main drive shaft of the press, coupling the phase changer to the main drive shaft will not result in any operational change. And since, in a color press, all of the color units are driven by, and accurately phased to, the main drive shaft, the vibrated rollers for the respective colors will remain in adjusted phase position, not only with respect to their individual plate cylinders, but with respect to each other.