Patent Application
20050160928
The present invention relates generally to offset printing presses, and more particularly to an offset printing press unit having removable plate and blanket cylinders.
Offset printing presses are well known in the art. Typically, water and ink are supplied to a printing plate cylinder, and are then transferred to a blanket cylinder for printing onto sheets or web, fed between the blanket cylinder and an impression cylinder. The water supply to the plate cylinder usually comprises a dampening unit having a dampening form roller which contacts the plate cylinder and is fed water from a water pan through intermediate water transferring rollers. Similarly, an inking unit transfers ink from an ink supply to the plate cylinder through an ink transfer and application rollers.
While such presses have fixed lateral dimensions, and as such printed products wider than the length of the cylinders cannot be produced, the circumference of the rotating cylinders determines the length of each repeated pattern being printed onto the web or sheets passing therethrough. Accordingly, the larger the circumference of the plate and blanket cylinders being used, the longer the printed pattern that can be produced. Therefore, in order to permit a press to be modified to permit printing of difference sized “repeats”, or each repeated pattern that is printed onto the web for each revolution of the cylinders, it is desirable to be able to use plate and blanket cylinders of different circumferences in order to be able to vary the repeat size provided by the press.
To achieve this desired press convertibility, it has been know to provide an offset press with a removable cylinder cartridge, having at least the plate and blanket cylinders mounted therein. For such a cartridge to be removed from the rest of the printing press, the cylinders must be disengaged from one another, and the entire cartridge is slid out as a single unit from the frame of the press. A replacement cartridge having therein plate and blanket cylinders of a smaller or larger circumference, is then inserted into the press in place of the original cartridge. This therefore permits the press to be converted to change the size of the repeat produced with each rotation of the press cylinders. While this solution provides the press with repeat size flexibility, each cartridge is large and costly, and therefore the practical range of flexibility is generally limited by the cost and space considerations of keeping many different cartridges having cylinders of various sizes.
Various printing presses having removable cylinders are also known. However, to permit the removal of the cylinders requires them to be disengageable from one another. The precisely set contact stripe between the cylinders is therefore often lost. Further, this typically also requires that the intermeshed gears driving the cylinders can be completely disengaged from each other every time a cylinder is to be removed, and easily re-engaged once a new replacement cylinder is introduced into the press. A known way to avoid this problem is to completely replace the gear train by drive motors used to drive the cylinders at the necessary speeds. Particularly, some presses employ a drive motor for each cylinder, thereby circumventing the requirement of gear trains completely. However, printing presses which are completely driven by servo drive systems are more expensive and more complex than those which use traditional gear train drives. Further, if any of the drive motors are incorrectly set or malfunction, the resultant mismatch in cylinder speeds can cause defective printed product or damage to the press.
It is an object of the present invention to provide an offset printing press with independently removable plate and blanket cylinders.
It is also an object of the present invention to provide an offset printing press having plate and blanket cylinders with replaceable outer sleeves.
It is an object of the present invention to provide an offset printing press having a cylinder drive linkage mechanism which maintains gear mesh when cylinders are disengaged from one another.
It is another object of the present invention to provide a variable form roller throw-off and strip adjustment mechanism for an offset printing press.
Therefore in accordance with the present invention, there is provided an offset printing press comprising: a plate cylinder, a blanket cylinder and an impression cylinder each mounted in a frame structure for rotation about parallel individual axes of rotation, the plate cylinder and the blanket cylinder having a common outer circumference defining a print repeat size produced by the plate and blanket cylinders; plate and blanket cylinder retention mechanisms respectively engaging the plate cylinder and the blanket cylinder, each retention mechanism comprising first and second trunnions rotatable within the frame structure and respectively engageable to a corresponding cylinder end, at least one of said first and second trunnions being axially displaceable by an actuating member between an operative position and a disengaged position, said at least one trunnion being fastenable in mating engagement with said corresponding cylinder end in the operative position and freely disconnected from said corresponding cylinder end in the disengaged position, such that the plate cylinder and the blanket cylinder are removable from the printing press from between the frame structure; and wherein at least one of the plate and blanket cylinder retention mechanisms is selectively displaceable relative to the frame structure such that a distance between the axes of rotation is variable, said at least one cylinder retention mechanism being fastenable in a desired position to maintain the distance at a predetermined value; whereby the plate and blanket cylinders are removable from the printing press and substitutable with replacement cylinders having a different outer circumference, thereby providing a correspondingly different sized print repeat when the replacement cylinders are installed into the printing press.
There is also provided, in accordance with the present invention, a cylinder drive system for an offset printing press having a plate cylinder and a blanket cylinder mounted in a frame structure such that a distance between axes of rotation thereof is selectively variable, the cylinder drive system comprising: a drive motor operatively connected to one of the plate cylinder and the blanket cylinder to provide driven rotation thereto; a gear drive linkage mechanism operably inter-engaging the plate cylinder and the blanket cylinder such that the drive motor drives both the plate and blanket cylinders; and wherein the gear drive linkage mechanism remains in gear meshed engagement with both the plate cylinder and the blanket cylinder regardless of the variable relative positions thereof.
There may also be provided, in accordance with the present invention, an offset printing press including a plate cylinder, a blanket cylinder and an impression cylinder mounted in a frame structure in serial contactable engagement, the printing press comprising a cylinder adjustment mechanism operable to displace at least one of the plate cylinder and the impression cylinder between a predetermined printing position, wherein said at least one of the plate cylinder and the impression cylinder is in contacting engagement with the blanket cylinder, and a disengaged position, wherein said at least one of the plate cylinder and the impression cylinder is removed from contacting engagement with the blanket cylinder, the cylinder adjustment mechanism being selectively actuable and providing controlled variable displacement of said at least one of the plate cylinder and the impression cylinder relative to the blanket cylinder.
Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:
a is a schematic side elevation view of the drive linkage mechanism of
b is a schematic side elevation view of the drive linkage mechanism of
a is a schematic side elevation of the offset printing press of
b is a schematic side elevation of the offset printing press of
Referring to
As mentioned above, the circumference of the rotating cylinders determines the length of each repeated pattern being printed onto the web passing therethrough. The term repeat is generally used herein to define this repeated pattern that is printed on the web for every revolution of the plate and blanket cylinders. In order to allow for a wide range of print repeat sizes at a relatively low cost, the offset printing press 10 of the present invention permits the plate and blanket cylinders 12 and 14 respectively to be independently removed from the printing unit 15 such that they can be replaced with corresponding cylinders having a different circumference. This accordingly permits the size of the repeat to be easily changed. Rather than having to store a large number of pairs of plate and blanket cylinders 12,14 having different circumferences, the interchangeable plate and blanket cylinders 12,14 of the present invention preferably have common central mandrel shafts to which outer sleeves of various circumferences can be selectively engaged.
Particularly, referring to
The blanket cylinder 14 comprises a central mandrel shaft 58 having a central axis 48. In the embodiment of
Actuating members are preferably used to displace at least the trunnions 47a and 49a between inner the operative position, wherein the trunnions are forced into mating engagement with the ends of each cylinder such that the trunnions and the cylinders rotate together, and the disengaged position, where the trunnions are freely disconnected from the ends of the cylinders such that removal of the cylinders is possible. The actuating members can be any suitable mechanism for axially displacing the trunnions inward and outward relative to the cylinders, such as for example a pneumatically operated cylinder. Preferably, the actuating members are remotely operated, such that the trunnions can be engaged and disengaged from the cylinders by a press operator from a control station. However, a manual override for such a pneumatically operated actuating member can also provided.
Thus, both the plate cylinder 12 and blanket cylinder 14 can be independently removed from the press. Once removed, the outer sleeves 54 and 60 can be disengaged from the central mandrel shafts 52 and 58 of the plate cylinder 12 and the blanket cylinder 14 respectively. This therefore permits the outer sleeves to be replaced by alternately sized sleeves, such that the overall outer circumference of the cylinders can be varied. Preferably, only the outer sleeves on the common central mandrel shafts need be replaced in order to change the size of the repeat produced. However, it is also possible to use solid or one-piece cylinders without sleeves, in which case the entire cylinder is replaced. Although, this may be more expensive and necessitate greater storage requirements, one-piece cylinders are nonetheless useful for certain printing applications.
The bearing mounting assembly 53 of the plate cylinder 12 are preferably not translatable within the frame structure 18, regardless of the size of the plate cylinder 12, however the mounting assemblies 53 are rotatable therewithin. Referring to
The inking unit 20 and dampening unit 22 are displaceable as required to accommodate the particular size of plate cylinder employed, while remaining in contact therewith. Although the plate cylinder 12 is eccentrically mounted, and therefore can be slightly displaced such that it is disengaged from contact with the blanket cylinder 14, the central axis 46 of the plate cylinder 12 otherwise remains secured in place within the frame structure 18. This, therefore, requires that the blanket cylinder 14 is selectively displaceable using the translatable bearing-blocks 63 as described above, such that cylinders of various diameters can be accommodated and a desired contact stripe is maintained between the adjacent cylinders, irrespective of the size of the cylinder (or the outer sleeve thereof) being used.
As shown in
As seen in
Referring now to FIGS. 2 to 4, a single drive motor 71, which directly drives the plate cylinder 12 of the printing unit 15, and the plate cylinder 12 is linked with the blanket cylinder 14 by a drive linkage mechanism 70. The drive motor 71 can either be coaxially arranged with the plate cylinder (as shown in
Accordingly, the drive linkage mechanism 70 ensures that the distance between the central axes of the plate cylinder gear 72 and the first idler gear 74 remains constant, as does the distance between the blanket cylinder gear 76 and the second idler gear 75. The two idler gears remain intermeshed regardless of the positions of the first and second linkage arms 78 and 80. Accordingly, the drive linkage mechanism 70 permits the distance between the central axes 46 and 48 of the plate cylinder 12 and the blanket cylinder 14 to be varied, without disengaging the gear train linkage therebetween. This enables the gear mesh through the gear train to be maintained, even as the cylinders are moved relative to each other. The blanket cylinder 14 can accordingly be translated along the blanket cylinder displacement line 43, the translating bearing-blocks 63, within which the trunnions 49a,b of the blanket cylinder are mounted, sliding in the correspondingly shaped slot 84 defined in the frame structure 18, without having to disengage to the gear train. This therefore permits sleeves of various diameters to be used, thereby requiring various positions of the cylinders, without having to disengage or reset the mechanical gear linkage between the plate and blanket cylinders. This represents a significant time savings and makes modifying the printing press to vary the repeat length of the printed product much easier. In some prior art systems which permit for interchangeable cylinders or cylinder sleeves, the gear ring for each cylinder must also be changed at the same time as the sleeve thereon. This is not true of the present drive train and linkage mechanism, as the gears remain intermeshed regardless of the position of the cylinders, and the drive motor can be driven at a selected angular speed required to accommodate the chosen sleeve diameters.
The impression cylinder 16 is preferably driven by a smaller transfer gear 64, located at the pivot point 41 of the impression cylinder 16, which can be driven by an independent drive motor or the press main drive.
a discloses the drive linkage mechanism 70 of the printing unit 15, wherein the plate cylinder 12 and the blanket cylinder 14 have smallest sized cylinder sleeves thereon. Accordingly, the blanket cylinder 14 is located in an uppermost position within the slot 84.
Referring now back to
The plate cylinder 12 is also preferably provided with a lateral adjustment mechanism, driven by an independent motor, which allows the press operator to make slight lateral adjustments in the position of the plate cylinder 12 relative to the blanket cylinder 14. This permits fine lateral relative adjustment of the two cylinders to ensure a precise contact stripe therebetween.
The dampening unit 22 and the inking unit 20 are preferably driven by the same drive used for the impression cylinder 16. A servo motor drive, independent of the main motor 71 used to drive the plate cylinder 12, is preferably provided for the impression cylinder 16. However, this impression cylinder servo drive is preferably only used to make small adjustments to the speed of the impression cylinder (ie: to “trim” the speed) and is therefore used for control rather than power. The main drive power for the impression cylinder 16 is preferably provided by the main press gear linkage.
In order to provide the maximum mechanical rigidity of the blanket cylinder 14, and in order to eliminate issues of imprecise impression setting repeatability, an impression “throw off/on” control is further preferably provided. The impression throw-off feature permits the plate cylinder 12 and the impression cylinder 16 to be displaced by a small preset amount, such that they are disengaged from contact with the blanket cylinder 14. This permits printing to be interrupted, without having to drastically displace the cylinders relative to each other, and permits printing to be easily re-started, without having to precisely reset the contact stripes between the cylinders. As described above, the plate cylinder can be “thrown-off” to stop printing by being eccentrically mounted in the rotatable mounting assembly 53. Thus, the rotatable mounting assembly 53 can be rotated within the frame structure 18, such that the plate cylinder is slightly displaced away from the blanket cylinder. The impression cylinder 16 is also disengageable from the blanket cylinder 14 by an adjustment mechanism 86, described in greater detail below.
Particularly referring to
Accordingly, the first actuator 81 is used for impression adjustment, such that the impression cylinder can be displaced to accommodate the particular size of blanket and plate cylinders being employed, and to control the contact pressure between the impression cylinder 16 and the blanket cylinder 14. By extending or retracting the first translating end 83 of the first actuator 81, the impression cylinder pivot arm 44 is thus pivoted such that the impression cylinder 16 displaced as required. The first actuator 81 preferably has a relatively large travel, such that plate and blanket cylinder of various sizes can be accommodated. However, the first actuator is also preferably precisely controlled, such that a desired contact pressure between the impression cylinder 16 and the blanket cylinder 14 can be set. Once this is set, the first actuator 81 is locked, such that the relative positions of the first and second ends thereof are fixed.
The second actuator 89 of the impression cylinder adjustment mechanism 86 is used to “throw-on” or “throw-off” the impression cylinder 16, such that printing can be started or stopped when required. Displacing the translating end 95 of the second actuator 89 acts to rotate the eccentric rotating assembly 87 within the frame structure 18, thereby slightly displacing the second end 85 of the locked first actuator 81 by a slight distance, which accordingly disengages the impression cylinder 16 from contact with web 11 and the blanket cylinder 14 by said slight distance. This slight distance generally corresponds to the eccentricity of the second end 85 of the first actuator 81 relative to the center of rotation of the rotating assembly 87. Thus, the precise location of the impression cylinder and the contact stripe relative to the blanket cylinder can be preset by the first actuator 81 and then locked in position, and the second actuator 89 can be activated to easily engage and disengaged the impression cylinder 16 with the blanket cylinder 14, without having to reset the position and contact stripe each time.
The embodiments of the invention described above are intended to be exemplary. Those skilled in the art will therefore appreciate that the forgoing description is illustrative only, and that various alternatives and modifications can be devised without departing from the spirit of the present invention. Accordingly, the present is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.
