Patent Publication Number: US-6655278-B2

Title: Apparatus for fine positional adjustment of a plate cylinder for multicolor image registration

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to printing presses in general and, in particular, to a multicolor, rotary printing press comprising a plurality of plate cylinders for printing as many different color images on a continuous web of paper. More particularly, the invention pertains to means in such a printing press for fine positional readjustment of each plate cylinder in both lateral (axial) and circumferential directions thereof for exact registration of the images with a reference image printed by one of the plate cylinders. 
     A variety of approaches have been made for printing in exact registration of multicolor images by a rotary printing press. Of such conventional efforts, one that is most pertinent to the instant invention is that disclosed in Japanese Unexamined Patent Publication No. 53-134507. The plate cylinder according to this prior art device is split into two halves along a plane at right angles with the cylinder axis, one of the cylinder halves being movable both laterally (axially) and circumferentially relative to the other. The split plate cylinder is provided, at each of its opposite ends, with a lateral adjustment and a circumferential adjustment whereby each cylinder half is positionally adjustable independently, even during printing. 
     Each lateral adjustment of the noted unexamined patent publication includes a screw-threaded rod which is coaxially and rotatably coupled to each lateral end of the plate cylinder while being restrained from lateral displacement relative to the same. The threaded rod is matingly engaged with an internally threaded sleeve which is rotatably mounted to the frame while being locked against lateral displacement relative to the same. Thus, as the threaded sleeve is driven bidirectionally, the threaded rod travels back and forth with one of the plate cylinder halves for readjustment of its lateral position. 
     Each circumferential adjustment, on the other hand, of the same prior art device includes another sleeve which is fitted over one end portion of the plate cylinder shaft for relative displacement in its lateral direction only. One end of the sleeve is coaxially joined to a helical gear which is in mesh with another such gear on the neighboring blanket cylinder. Also coupled to the sleeve is a spur gear which is rotatable relative to the sleeve but which is locked against lateral displacement relative to the same. This spur gear is coaxially provided with an externally threaded boss which is engaged with an internally threaded member mounted fast to the frame. 
     Therefore, on being driven angularly bidirectionally, the spur gear laterally travels back and forth with the sleeve on the plate cylinder shaft because of the mating engagement of its threaded boss with the fixed, internally threaded member. Traveling laterally, moreover, the sleeve is forced to make angular displacement with the plate cylinder shaft as the helical gear thereon slides in mating engagement with the similar gear on the blanket cylinder. The plate cylinder half is thus readjusted in its circumferential position. 
     Another similar register control device is found in Japanese Unexamined Patent Publication No. 63-91248. This second prior art device also has a sleeve which is formed in one piece with a helical gear for driving the plate cylinder and which is rotatably coupled to the plate cylinder shaft while being restrained from lateral displacement relative to the same. The sleeve is externally threaded for mating engagement with an internally threaded member affixed to the frame and carries on its end away from the helical gear a pinion in engagement with a rack for lateral adjustment. 
     The circumferential adjustment of this second prior art device has a second sleeve fitted over the first mentioned sleeve and screw-threadedly engaged therewith. The second sleeve has one end thereof rotatably coupled to the helical gear and restrained from lateral displacement relative to the same. The other end of the second sleeve is shaped into a pinion engaging with another rack for circumferential adjustment. 
     Both prior art devices are alike in having gears or toothed wheels driven by rotary or linear actuators. Mechanically farthest away from the plate cylinder shaft to be driven, these drive wheels are threadedly engaged with sleeves or the like in order to enable translation from rotary to linear motion. The linear motion is imparted more or less directly to the plate cylinder for its lateral displacement and, for circumferential displacement, reconverted into rotary motion by the relative sliding motion of the intermeshing helical gears through which the plate cylinder is driven during printing. 
     Typically, in offset rotary printing presses for newspaper production, the maximum allowable lateral displacement of the drive wheels for lateral adjustment is set in a range of four to six millimeters, and that of the drive wheels for circumferential adjustment in a range of twelve to eighteen millimeters. In practice, however, the drive wheels have often been driven in excess of these limits as the rotary or linear actuators are left in operation for prolonged periods of time due to some errors in control or in manual operation. 
     One frequent result of such overdriving has been the riding of the drive wheels onto the incomplete threads of the rods or the sleeves, with the consequent jamming of the adjustments. Some movable parts of the adjustments have also been easy to run into some other parts with which they should be totally out of contact, again resulting in jamming and, in the worst case, in the irreparable damage of these parts. 
     It has often been impossible to recover, for instance, the drive wheels back from the incomplete threads merely by reversing the actuators. Prolonged periods of time have thus had to be expended for recovery from such troubles, adding very substantially to the downtime, as well as the maintenance costs, of the multicolor printing press. Obviously, moreover, the useful life of the press must also have been considerably curtailed. 
     SUMMARY OF THE INVENTION 
     The present invention seeks totally to preclude the overrunning of both lateral and circumferential adjustments incorporated in a multicolor printing press for image registration purposes, thereby enhancing reliability in the operation of the adjustments, reducing the downtime of the machine, and extending its useful life. 
     Briefly, the invention may be summarized as an apparatus for fine positional adjustment of a plate cylinder in both lateral and circumferential directions thereof for image registration of a multicolor rotary printing press. Included is a plate cylinder supported by frame means for both lateral and circumferential displacement. Lateral adjustment means act between the plate cylinder and the frame means for positional adjustment of the plate cylinder in a lateral direction thereof relative to the frame means. Circumferential adjustment means also act between the plate cylinder and the frame means for positional adjustment of the plate cylinder in a circumferential direction thereof relative to the frame means. 
     The invention particularly features lateral overrun prevention means for limiting the bidirectional rotation of a first rotary member of the lateral adjustment means relative to the frame means in order to prevent the plate cylinder from being driven laterally beyond limits, and circumferential overrun prevention means for limiting the bidirectional rotation of a second rotary member of the circumferential adjustment means relative to the frame means in order to prevent the plate cylinder from being driven circumferentially beyond limits. 
     In a preferred embodiment both first and second rotary members take the form of driven gears, which are in mesh with drive pinions on the output shafts of lateral and circumferential drive motors, respectively. Locking the driven gears against rotation in the event of an emergency, rather than other rotary or movable parts of the lateral and the circumferential adjustment means, is preferred because the driven gears can be easily made large enough to be arrested lightly. 
     Adapted for this embodiment, the lateral overrun prevention means comprises a limit stop formed on the frame means, and a projection formed eccentrically on the driven gear of the lateral adjustment means for movement into abutment against the limit stop with the prolonged rotation of the driven gear. Preferably, normally positioned at an angular distance of approximately 180 degrees from the limit stop, the projection is to travel, with the bidirectional rotation of the driven gear, into possible abutment against the opposite sides of the limit stop. 
     The circumferential adjustment means likewise comprises limit stop means on the frame means, and projection means formed eccentrically on the driven gear of the circumferential adjustment means for movement into abutment against the limit stop with the prolonged rotation of the driven gear. Since the driven gear not only rotates but travels laterally for circumferential positioning of the plate cylinder, the limit stop means may have a pair of limit stops spaced from each other laterally of the driven gear. The projection means may have a pair of projections formed on opposite sides of the driven gear for movement, with the combined bidirectional rotary and lateral motion of the driven gear, into abutment against the respective limit stops. 
     Thus, with the driven gears of both lateral and circumferential adjustment means positively restrained from rotation beyond limits, no undue displacement of the plate cylinder is to take place in either its lateral or circumferential direction. Moreover, when either or both of the driven gears are locked against rotation by the overrun prevention means, no damaging force will be exerted on any parts of the adjustment means or on any associated parts of the press. 
     It is also preferred that both lateral and circumferential adjustment means include drive means such as rotary or linear actuators having their output forces optimally preadjusted in order to avoid damage upon functioning of the overrun prevention means. Stepper motors are particularly recommendable as they suffer no damage at all, mechanically or electrically, when forced to stop. 
     Altogether, the multicolor printing press built on the novel concepts of the invention will drastically reduce both downtime and operating hours per unit volume of production. These results will be of particular advantage in newspaper production which is hard pressed for time. 
     The above and other objects, features and advantages of the invention and the manner of realizing them will become more apparent, and the invention itself will best be understood, from the following description taken together with the attached drawings showing some preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an axial sectional view showing how one end of a plate cylinder of a rotary offset printing press, which cylinder has its plate-carrying surface split into a pair of halves along a plane normal to its axis, is supported and coupled to lateral and circumferential adjustments according to the invention; 
     FIG. 2 is a view similar to FIG. 1 but showing how the other end of the plate cylinder is supported and coupled to its own lateral and circumferential adjustments according to the invention; 
     FIG. 3 is a fragmentary elevation, with a part shown broken away to reveal another part, of the split plate cylinder of FIGS. 1 and 2; 
     FIG. 4 is an enlarged end elevation, with a part shown broken away to reveal other parts, of the showing of FIG. 1, as seen in the direction of the arrow IV therein; 
     FIGS. 5A and 5B are a series of still more enlarged, fragmentary, sectional views explanatory of the operation of the lateral overrun prevention means of FIG. 1; and 
     FIGS. 6A,  6 B and  6 C are a series of views similar to FIGS. 5A and 5B but explanatory of the operation of the circumferential overrun prevention means of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     General 
     The present invention will now be described in detail as applied to a multicolor offset rotary printing press having a plurality of printing units, each conventionally comprising a plate cylinder, a blanket cylinder, an impression cylinder and so forth, for printing multicolor images on a continuous web of paper traveling therethrough. The invention concerns how to support each such plate cylinder so as to permit fine positional adjustment thereof in both lateral and circumferential directions so that the multicolor images may be printed in exact register with each other. 
     FIGS. 1 and 2 depict one such plate cylinder  1 , as well as one associated blanket cylinder  2 , both supported between a pair of confronting frame walls  22  and  22 ′ for both lateral and circumferential displacement. The two cylinders  1  and  2  are coupled together via two intermeshing helical gears  10  and  11 , FIG. 1, and another two similar gears  10 ′ and  11 ′, FIG. 2, for joint rotation during printing, although these helical gears are additionally utilized for circumferential positional adjustment of the plate cylinder. 
     As shown fragmentarily in FIG. 3, the plate cylinder  1  has its plate-carrying surface-split into a pair of halves  5  and  5 ′ in this particular embodiment of the invention. The plate cylinder half  5 ′ is slidably fitted over the reduced diameter portion  1   a  of the plate cylinder which is in one piece with the other cylinder half  5 . Separately carrying printing plates, not shown, both plate cylinder halves  5  and  5 ′ are to be independently positionally adjusted in both lateral and circumferential directions thereof. 
     Thus, referring back to FIG. 1, the plate cylinder  1  is provided at its right hand end, as seen in this figure, with image registration means  4  for lateral and circumferential positional adjustment of the right hand plate cylinder half  5 . At the left hand end of the plate cylinder  1 , on the other hand, there are provided image registration means  4 ′, FIG. 2, for lateral and circumferential positional adjustment of the left hand plate cylinder half  5 ′. Both image registration means  4  and  4 ′ are alike in construction and operation. 
     The right hand image registration means  4  comprise a lateral adjustment  14  for lateral positional adjustment of the right hand plate cylinder half  5 , and a circumferential adjustment  15  for circumferential positional adjustment of the same. The lateral adjustment  14  is provided with lateral overrun prevention means  16 , and the circumferential adjustment  15  with circumferential overrun prevention means  17 , in order to keep the respective adjustments  14  and  15  from jamming through accidental or inadvertent overdriving. 
     The left hand image registration means  4 ′ likewise comprise a lateral adjustment  14 ′ and a circumferential adjustment  15 ′ for lateral and circumferential positional adjustment, respectively, of the left hand plate cylinder half  5 ′. The lateral adjustment  14 ′ is provided with lateral overrun prevention means  16 ′, and the circumferential adjustment  15 ′ with circumferential overrun prevention means  17 ′. 
     Hereinafter in this specification the above noted lateral adjustment  14 , lateral overrun prevention means  16 , circumferential adjustment  15 , and circumferential overrun prevention means  17  for the right hand plate cylinder half  5  will be discussed in more detail, under separate headings and in that order. The lateral adjustment  14 ′, lateral overrun prevention means  16 ′, circumferential adjustment  15 ′, and circumferential overrun prevention means  17 ′ for the left hand plate cylinder half  5 ′ are substantially identical in construction with their right hand counterparts to be detailed, so that their description will be omitted, and their constituent parts will be identified in FIG. 2 merely by priming the reference numerals used to denote their corresponding parts in the right hand image registration means  4 . Operational description of the complete apparatus will follow the discussion of the listed components. 
     Lateral Adjustment 
     With reference to FIG. 1 the lateral adjustment  14  as a whole is coupled to a reduced diameter extension  3  of the plate cylinder shaft which is journaled in the frame wall  22  for both angular and lateral displacement relative to the same. The lateral adjustment  14  includes an inner sleeve  23  fitted over the plate cylinder shaft extension  3  and restrained from both lateral and angular displacement relative to the same in a manner to be made apparent presently. A spur gear  34  is formed externally on part of the inner sleeve  23  for use as a part of the circumferential adjustment  15  yet to be detailed. 
     Having an antifriction bearing  24  mounted therein, a bearing housing  70  is coaxially mounted fast to the plate cylinder shaft extension  3  and fastened to the inner sleeve  23 , locking the same against lateral and rotary motion relative to the plate cylinder shaft extension. A screw-threaded rod  25  is coaxially coupled to the plate cylinder shaft extension  3  by having its left hand end, as viewed in FIG. 1, journaled in the bearing  24  and is thereby constrained to lateral displacement with the plate cylinder shaft extension. There is no torque transmission, however, between plate cylinder shaft extension  3  and threaded rod  25 . 
     The threaded rod  25  is screw-threadedly extended through a subframe wall  26  via a hollow, internally threaded member  27  mounted fast thereto, so that the threaded rod  25  will travel linearly back and forth relative to the subframe wall on being rotated bidirectionally. Preferably, the threaded rod  25  should be engaged with the internally threaded member  27  via antifriction balls, not shown, confined between their external and internal threads. Such balls will serve materially to reduce the frictional resistance to the required bidirectional rotation of the threaded rod  25 . 
     On the right hand end, as seen in FIG. 1, of the threaded rod  25 , projecting from the subframe wall  26 , there is fixedly mounted a rotary member  28  which serves both for bidirectional torque transmission to the threaded rod and as a part of the lateral overrun prevention means  16 . The rotary member  28  is herein shown as a driven gear, having a set of spur gear teeth  72  on its periphery. The driven gear  28  not only rotates with the threaded rod  25  but travels laterally therewith. 
     For the bidirectional rotation of the threaded rod  25  a lateral drive motor or actuator  31  is bracketed at  29  to the subframe wall  26 . A preferred example of lateral drive motor  31  is a bidirectional stepper motor of prior art construction that rotates incrementally, rather than continuously, in response to electric stepping pulses. The stepper motor  31  has mounted on its output shaft a drive pinion  30  in mesh with the driven gear  28  on the threaded rod  25 . 
     Lateral Overrun Prevention Means 
     The lateral overrun prevention means  16  appearing in both FIGS. 1 and 4 and are shown on an enlarged scale in FIGS. 5A and 5B. Included is a pin or like projection  32  formed eccentrically on the driven gear  28  of the lateral adjustment  14  and extending toward the subframe wall  26 . A limit stop  33  is fastened to the subframe wall  26 , in a position to be hit by the pin  32  upon rotation of the driven gear  28  in excess of predetermined limits. 
     The plate cylinder  1 , or its right hand half  5  to be more exact, is to be laterally displaced bidirectionally from its normal position. When the plate cylinder half  5  is in its normal lateral position, so is the driven gear  28  of the lateral adjustment  14  in its normal angular position, from which the driven gear is to be normally driven up to the same angle, which is less than 180 degrees, in either direction. When the driven gear  28  is in this normal angular position, the pin  32  is angularly spaced approximately 180 degrees from the limit stop  33 , as indicated at  32   a  in FIG.  4 . 
     Driven in either direction from this normal angular position  32   a  in excess of a predetermined limit, the pin  32  will come into abutment against either side of the limit stop  33  on the subframe wall  26 . The pin  32  is shown engaging one side of the limit stop  33  in FIG.  5 A and the other side of the limit stop in FIG.  5 B. It will also be noted that the driven gear  28  differs in its lateral position between these two figures, since the driven gear travels laterally on angular displacement because of its mating engagement with the internally threaded member  27 . The relative dimensions of the pin  32  and the limit stop  33  in a direction parallel to the driven gear axis must therefore be determined in consideration of the amount of lateral displacement made by the driven gear  28  upon 360 degrees rotation thereof. 
     Circumferential Adjustment 
     As shown also in FIG. 1, the circumferential adjustment  15  includes an outer sleeve  36  fitted over the inner sleeve  23  of the lateral adjustment  14  for lateral sliding motion relative to the inner sleeve. The outer sleeve  36  is formed in one piece with an internal spur gear  35  which is in mesh with the spur gear  34  in one piece with the inner sleeve  23 . The outer sleeve  36  is therefore movable laterally relative to the inner sleeve  23  but is constrained to joint rotation therewith. 
     Also formed in one piece with the outer sleeve  36  is the aforesaid helical gear  10  in mesh with the other helical gear  11  on the blanket cylinder shaft  8 . By virtue of these intermeshing helical gears  10  and  11  the outer sleeve  36  on bidirectional lateral displacement is to be angularly displaced in both directions with the inner sleeve  23 , hence with the plate cylinder shaft extension  3 , and hence with the right hand plate cylinder half  5 . 
     The outer sleeve  36  has an antifriction bearing  38  mounted to its end away from the plate cylinder  1  via a bearing housing  37 . Rotatably supported by this bearing is a rotary member  40  herein shown as a driven gear, carrying a set of spur gear teeth  73  on its periphery, to be driven bidirectionally from a circumferential drive motor or actuator  43  via a drive pinion  42 . The driven gear  40  is coaxially mounted on the threaded rod  25 , set forth in conjunction with the lateral adjustment  14 , via a hollow, internally threaded member  39 . This internally threaded member  39  is secured to the driven gear  40 , substantially constituting an integral part of the gear. Thus the driven gear  40  not only rotates but travels laterally relative to the threaded rod  25 . Because of the interposition of the bearing  38 , however, it is only the lateral motion of the driven gear  40  that is transmitted to the outer sleeve  36  for circumferential positioning of the plate cylinder half  5 . 
     The circumferential drive motor  43  is bracketed at  41  to the subframe wall  26 . A preferred example of circumferential drive motor  43  is, again, a bidirectional stepper motor. 
     The stepper motors  31  and  43 , both FIG. 1, of the right hand lateral and the circumferential adjustments  14  and  15 , as well as the stepper motors  31 ′ and  43 ′, FIG. 2, of the left hand lateral and the circumferential adjustments  14 ′ and  15 ′ should all be of the known type that operate with a predetermined output torque and that stall without suffering any electrical or mechanical damage, when overloaded. Stepper motors of this type are available from various manufactures. 
     Other types of drive means could be employed, however, as long as they meet the foregoing requirements. Examples include hydraulic cylinders or hydraulic motors that operate with a hydraulic fluid under preset pressure, motors with a clutch such as a torque limiter that permits adjustment of a disconnection torque, and torque motors capable of electrical output torque control. 
     Circumferential Overrun Prevention Means 
     The circumferential overrun prevention means  17  are shown in FIGS. 1 and 2 and on an enlarged scale in FIGS. 6A-6C. A double ended pin  44  extends eccentrically through the driven gear  40  of the circumferential adjustment  15 , providing a pair of projections on both sides of the driven gear. For engaging with the double ended pin  44  a limit stop member  45  is fastened to the subframe wall  26 . U-shaped as seen in FIGS. 6A-6C, the limit stop member  45  provides a pair of limit stops  45   a  and  45   b  which are spaced from each other in a direction parallel to the axis of the driven gear  40 . 
     The driven gear  40  laterally travels back and forth on being driven bidirectionally by the circumferential drive motor  43 . One end of the pin  44  on the driven gear  40  is to come into abutment against one limit stop  45   a , as in FIG. 6A, when the driven gear is driven in one direction in excess of a prescribed limit. The other end of the pin  44  is to come into abutment against the other limit stop  45   b , as in FIG. 6C, when the driven gear is driven in the other direction in excess of a prescribed limit. 
     Operation 
     The operation of the right hand image registration means  4  will be described in regard first to the lateral adjustment  14 , together with the lateral overrun prevention means  16 , and then to the circumferential adjustment  15  together with the circumferential overrun prevention means  17 . The operation of the left hand image registration means  4 ′ is considered self evident from the operational description of the right hand image registration means  4 . 
     For purposes of explanation, it will be assumed that the lateral drive motor  31  rotates counterclockwise, as viewed in FIG. 4, in response to stepping pulses and a stepping direction signal from the unshown control electronics. Driven by the drive pinion  30 , the gear  28  will rotate clockwise with the threaded rod  25 . It is understood that the screw thread on this rod  25  is right handed. Consequently, turned clockwise, the rod  25  will travel to the left, as viewed in FIG. 1, because of its engagement with the internally threaded member  27  on the subframe wall  26 . 
     Since the threaded rod  25  has its left hand end, as seen in FIG. 1, coupled to the plate cylinder shaft extension  3  via the bearing  24 , only the lateral motion of the threaded rod will be transmitted to the shaft extension. The result will be the leftward lateral travel of the right hand plate cylinder half  5 . 
     In the practice of the instant invention the maximum allowable lateral displacement of the plate cylinder half  5  may be from about four to about six millimeters for proper registration of all the multicolor images. The pitch of the threaded rod  25 , and of course that of the internally threaded member  27 , should be so determined that the plate cylinder half  5  is laterally displaced a preselected distance within this range in response to the rotation of the driven gear  28  through a preselected angle not exceeding 360 degrees. 
     With that normally allowed angle of rotation of the driven gear  28  in mind, let us proceed now to the operational description of the lateral overrun prevention means  16 . The pin  32  on the driven gear  28  is normally angularly spaced as aforesaid 180 degrees from the limit stop  33  on the subframe wall  26 . As long as the lateral drive motor  31  is operating normally, the pin  32  will not engage the limit stop  33  even when turned the maximum allowable angle in either direction from its normal position  32   a.    
     If the lateral drive motor  31  remains in counterclockwise rotation too long because of some control trouble or motor malfunctioning, the driven gear  28  will rotate clockwise in excess of its normally allowed angle until, after about 180 degrees of rotation, the pin  32  on the driven gear comes into abutment against one side of the limit stop  33 , as pictured in FIG.  5 A. The lateral drive motor  31  will then come to a standstill. Neither this motor nor any other parts or components of the press are to be ruined by such forced stop of the motor. 
     In the event of prolonged clockwise rotation of the lateral drive motor  31 , on the other hand, the driven gear  28  will rotate counterclockwise until the pin  32  thereon comes into abutment against the other side of the limit stop  33 , as in FIG.  5 B. Although the driven gear  28  will travel laterally away from the subframe wall  26  in this case, the pin  32  will nevertheless engage the limit stop  33  because the dimensions of the pin and the abutment in a direction parallel to the driven gear axis are determined in relation to each other in consideration of the lateral displacement of the driven gear. 
     The circumferential drive motor  43  may be set in rotation in a required direction for circumferential positioning of the right hand plate cylinder half  5 . Driven through the drive pinion  42 , the driven gear  40  will rotate with the internally threaded member  39  coaxially secured thereto and so travel laterally of the threaded rod  25 . The bearing  38  will convey only the lateral travel of the driven gear  40  to the bearing housing  37  and thence to the outer sleeve  36 . The outer sleeve  36  will then travel laterally with the helical gear  10  thereon in sliding engagement with the helical gear  11  on the blanket cylinder shaft  8 , thereby undergoing angular displacement. Although, here again, the outer sleeve moves both laterally and circumferentially, it is only the circumferential motion that will be transmitted via the intermeshing spur gears  34  and  35  to the plate cylinder shaft extension  3  and thence to the right hand plate cylinder half  5 . 
     The amount of lateral displacement of the driven gear  40  for a desired amount of circumferential displacement of the right hand plate cylinder half  5  may be from about twelve to about eighteen millimeters. The amount of angular displacement of the driven gear  40  for such desired lateral displacement may be more than two, and less than three, complete revolutions. The circumferential overrun prevention means  17  function to prevent the rotation of the driven gear  40  in excess of the preset limits. 
     FIG. 6B shows the driven gear  40  in its normal lateral position, in which the gear is equidistantly spaced from the pair of limit stops  45   a  and  45   b . The double-ended pin  44  on the driven gear  40  is also shown in this figure in its normal angular position, in which the pin is angularly spaced about 540 degrees, one and a half revolutions, from both limit stops  45   a  and  45   b . The pin  44  will contact neither limit stops as long as the circumferential drive motor  43  is operating normally. 
     If the circumferential drive motor  43  continues rotation in a counterclockwise direction, as viewed in FIG. 4, beyond a limit of angular displacement of the right hand plate cylinder half  5  for some trouble or other, then the driven gear  40  will turn clockwise and travel laterally toward the plate cylinder. The rotation of the driven gear  40  will be arrested after one and a half revolutions from its normal position, as then one end of the pin  44  comes into abutment against the limit stop  45   a  as in FIG.  6 A. 
     In the event of continued clockwise rotation of the circumferential drive motor  43 , on the other hand, the driven gear  40  will turn counterclockwise and travel laterally toward the subframe wall  26 . In this case, too, the driven gear  40  will stop after one and a half revolutions from its normal position, when the other end of the pin  44  comes into abutment against the other limit stop  45   b  as in FIG.  6 C. 
     Although the image register control device according to the present invention has been shown and described hereinbefore in terms of one specific embodiment thereof, it is not desired that the invention be limited by the exact details of this embodiment. It is also understood that the invention is applicable to plate cylinders that are not split into halves. A combination of one lateral, and one circumferential, adjustment may be provided only at one end of such an unsplit plate cylinder. A variety of other modifications, alterations, and adaptations of the invention will suggest themselves to one skilled in the art without departing from the scope of the claims attached hereto.