Continuous gravure printing machine

Abstract

 A gravure printing machine has first and second printing means arranged in a frame and capable of continuous printing without having to terminate the operation. A retractable impression roller, when retracted, from either the first or second machine enables a web to follow a travel path between the image transfer nip of one printing machine and the impression roller, the latter serving as an idler roller. A controller means is used to reposition the retracted impression roller into contact and alignment with a print roller, and for sequentially retracting the retractable impression roller from the other printing machine so as to accommodate printing by the other machine.

Description

[0001] The present invention relates to machines for conveying and processing web roll. More particularly, the invention concerns a continuously operating machine, such as a gravure printer, which conveys and processes web without having to terminate operation to accommodate a hardware changeover.

[0002] In conventional web conveyance operations, such as gravure printing machines, a web is conveyed through a series of operations culminating in an image (for example a label) being transferred to the web. A typical label printing operation in the photographic paper lamination industry uses several single modular printing machines arranged generally in line, each performing a cooperative single task like unwinding, laminating, drying, and so forth. The application of the label to one side of the web is accomplished by first conveying the web from a feed stock roll into a image transfer nip formed by the contacting impression and print rollers. Once the image or label is transferred to the web, the transferred image is then exposed to a lamination step in which the selective label is laminated onto the web.

[0003] With increasing demands for higher operating speeds and volume as well as frequent requirements to interchangeably print one of several products (for instance assorted labels or logos printed on the back of photographic paper or web), current printing operations must be shut down to accomplish a hardware changeover. Inevitably, when the printing machine is shutdown, the extruder process which assist in the lamination step must be taken off line. Upon restart of the lamination process, special warm-up and material break-in procedures are implemented to qualify the process. In all cases the print roller and a cooperating ink supply trough must be washed of residual printing material. It is our experience that this process step consumes considerable amount of product and plastic waste (such as extruder material) as well as take time away from the plant capacity. Moreover, the print machine changeover process includes removing the existing or expired photographic paper stock roll as well as the print roller used for one printing task and then installing a fresh stock roll and different roller to accommodate the new printing task. Of course the aforementioned processes are enormously time consuming, costly and frequently they may present adverse safety risk factors to the operator.

[0004] US-A-5,069,125 discloses a gravure printing machine having two printing bays which relies on a print cylinder trolley to transport a print roller into a contacting position with a fixed impression roller at either of the printing bays to accommodate a certain printing task. While a wide range of printing applications are contemplated by this prior art development, this capability is achieved at the expense of enormous redundancy in components like idler rollers and drives that are very costly and not required for less demanding and less complex printing operations. More importantly, the aforementioned prior art printing machine requires several major redundant components including dual removable printer rollers, dual ink troughs and blades, arranged on separate trolley carts which enables a changeover in print task.

[0005] Therefore, there persists a need for an improved gravure print machine that can interchangeably provide continuous printing of one of two select print tasks that is easy to operate, involves minimum machine components , and does not require shutting down the operation and exposing the operators to unnecessary safety risks to change print tasks.

[0006] It is an object of the invention to provide a web conveying machine that can be used to interchangeably provide continuous conveying and processing without having to shut down the printing operation.

[0007] Another object of the invention is to provide a gravure printing machine that can accomplish one print task, and then, alternately undertake another print task without having to interrupt the machine operation.

[0008] It is a feature of the invention that first and second conveyance assemblages cooperate to provide continuos conveying and processing of a web.

[0009] It is another feature of the invention that a gravure printing machine has first and second printing means capable of cooperatively interchanging components to achieve one of two select print tasks.

[0010] To accomplish one or more of the above objects and advantages of the invention, there is provided, in one aspect of the invention, a machine for continuously conveying and processing web, comprising a frame having first and second conveyance assemblages arranged in different portions thereof. The first conveyance assemblage comprises first and second surfaces mounted for at least partial contact and defining a first nip therebetween. In this embodiment, one of the first and second surfaces is retractable which enables the retracted surface to cooperate with the other assemblage for conveying a web, as described in details below.

[0011] Furthermore, the second assemblage comprise third surface arrange for at least partial contact with a fourth surfaces and thereby defining a second nip therebetween. Also, the machine of the invention includes means for selectively conveying the web between a travel path through the nip of either the first or second conveyance assemblage and one of the retractable third and fourth surfaces, or alternatively, either one of the first and second surfaces, respectively.

[0012] The foregoing as well as other objects, features and advantages of this invention will become more apparent from the appended Figures, wherein like reference numerals denote like elements, and wherein:

Figure 1 is a side elevational view of the printing machine of the invention showing one assemblage in an operating mode and the other in a standby mode; and

Figure 2 is a side elevational view of the printing machine of the invention depicting an alternate operating mode.

Figure 3 is a flow diagram of the controller process for selectively activating one of two printing machines.

[0013] Turning now to the drawings, and particularly to Figs. 1 and 2, the machine in accordance with the principles of the invention is illustrated. Machine 10, for continuously conveying and processing a web 1, comprises a rigid frame 12 configured for supporting thereon first and second conveyance assemblages, or gravure printing means, 14,16. Gravure printing means 14,16 are arranged in a spaced relations on the frame 12 so that certain elements (described below) of first and second printing means 14,16 can alternately cooperate with each other in a manner described below. More particularly, first assemblage or gravure printing means, 14 comprises first and second surfaces 18, 20 mounted for at least partial lengthwise contact with one another to form a nip, or image transfer nip, 26, therebetween. In a preferred embodiment, first surface 18 is a print roller and the second surface 20 is an impression roller. The print roller 18 is generally fixed so as to enable at least a circumferential portion of print roller 18 to remain in continuous contact with a trough 22 containing a printing material, such as ink, 24. This arrangement allows ink to transfer to the print roller 18 and then transfer from the print roller 18 to the web 1 as it travels through the image transfer nip 26. Second surface, or preferably impression roller, 20 is retractably mounted to move transversally in the frame 12 in proximate lengthwise contact with the print roller. Impression roller 20 is preferably a steel tubular shell covered with compliant elastomeric material that easily compresses when contacted by the print roller. Those skilled in the art will appreciate that impression roller may be formed from other materials such as plastics, rubber or other metals, such as copper, nickel, and so forth The footprint between the lengthwise contacting print and impression rollers, 18,20 defines a first image transfer nip 26 for producing both movement of the web 1 as it passes through the nip 26, and more importantly, for transferring a preselected image to the web 1. Print roller 18 is provided with driving means, preferably an independent motor, which supplies the means for effecting the movement of web 1 through the image transfer nip 26.

[0014] In Figs. 1 and 2, the second conveyance assemblage, alternately second printing means, 16 arranged for at least partial cooperation with the first conveyance assemblage, alternately first printing means, 14 is arranged in another portion of the frame 12. Second assemblage 14, according to our invention, can alternately be used to perform a second print task, for example, printing logo X on web 1, while the first assemblage 14 is performing its print task, for example, printing logo Y on web 1. According to Figs. 1 and 2, more particularly, second conveyance assemblage 16 comprises third and fourth surfaces 30, 32 (preferably a print roller and impression roller, as described above) mounted for at least partial lengthwise contact. Similar to the description above, the at least partial lengthwise contact between third and fourth surfaces 30,32 forms an important second image transfer nip 28 which not only provides a means for providing travel of web 1 through the nip to downstream processes, but also imparts the desired image to the web 1 as it passes therethrough. In the preferred embodiment, fourth surface, alternately impression roller, 32 is retractable so that it can be used cooperatively with the first conveyance assemblage 14 forming a downstream web travel path therearound. A servo hydraulic unit made by Rexroth Corp. from Bethlehem, Pennsylvania, is used to retract the fourth roller 32 away from the third roller 30, as shown clearly in Figure 1. In this embodiment, impression roller 32 is depicted as an idler roller and cooperating with the first printing means of machine 10. Printing rollers 20, 30, preferably made of metal, such as steel, have a predetermined image engraved on their radial surface 34 for contact with the compliant, elastomer covered impression roller radial surfaces 16,36. As indicated, the two rollers at there point of contact form a respective image transfer nip 26, 28 therebetween of some width dictated by regulated pressure applied by the servo hydraulic system 40. Hydraulic system 40 further provides precise movement of the impression roller 20, 32 away from its respective print roller 18,30 and image transfer nip 28 transversely along the frame 12 to any desired position. A secure stop is provided to prevent further movement of the impression roller once in its desired retracted position. In the retracted position, impression rollers 20,32 become idler rollers and provide an extended travel path for the web 1 for further downstream processing, such as lamination. When the first print task is completed, the second roller 20 of the first assemblage 14 is retracted away from the first print roller 28 and image transfer nip 26 to form a web travel path therearound, and the fourth roller 32 of the second assemblage is repositioned to contact the third roller 30, thus establishing the start of the next printing task.

[0015] Moreover, according to Figure 1, machine 10 depicts print roller 18, retractable doctor blade 42 and retractable printing media trough 22. The retractable features of the invention enables these important components of machine 10 to be conveniently removed from the machine to accomplish hardware changeover. Indepependent servo units and controllers may be used to retract the doctor blade and trough away from the printing machine; or the units may be manually retracted.

[0016] In Figure 3, a flow diagram describing the control process of the invention for selectively conveying and processing a web, such as in either of the first or second gravure printing machines. As indicated, controller means provides the logic for retracting the impression roller of one printing means away from its corresponding image transfer nip while sequentially repositioning the impression roller of the other printing means in contact and alignment with its corresponding print roller of the other printing means. This sequence enables one print task to be undertaken on the active printing means while preparing to undertake a second print task on the idle printing means. According to Figures 1 and 3, to change print task, such as a label to be printed on the web, inactive gravure printing means 16 preparatory steps specified in 46 - 60 of Fig. 3 must be executed while a current print task is underway on the other gravure printers 14. Then, according to operations 62-76, the impression roller 20, active during the current print task, departs from its active position in contact with print roller 18 and takes the position along frame 12 as an idler roller shown in Fig. 2. Next, impression roller 32 of the printer 16 is moved into position in at least partial lengthwise contact with print roller 30, as described in operating sequences 62-76 of Fig. 3. This completes the cycle in which a print task was first underway on printer 14 and completed; and, then the operator selectively initiated another print task using the same machine 10, but on the alternate printing means 16. Operations 78-86 shown in Figure 3 are necessary for controllably prepare the machine 10 for various maintenance functions, such as to enable print roller washing and replacement (as described above), doctor blade change or replacement, and ink replacement.

[0017] In operation, the gravure printing machine 10 of the invention fulfills the task of quick label change without having to stop for printer roller changeover. One of the gravure printing means, as described above, is in operation with the print roller and impression roller forming a nip at the point of contact. The print roller from the other printing means remains in a stand-by mode and the impression roller provides a web travel path for the web being conveyed through the nip formed by the first and second rollers. In this embodiment, the stand-by impression roller becomes an idler roller for the web conveyed to the first printing means. The stand-by gravure printing machine (Figs. 1 & 2) has the impression roller retracted away from the print roller via a servo hydraulic system that can maintain impression roller alignment to the print roller within allowable tolerance at any position. This position is programmed into the PLC of the servo hydraulic system. The impression roller in its stand-by position serves as an idler, which is also an important feature of this invention. To change print task, such as labels, the operator must simply raise the impression roller of the operating printing machine and lower the corresponding roller of the stand-by printing machine. Thus, the stand-by printing machine, prior to performing a select print task, then becomes the operating or active print machine when the above control process is executed during machine operations. This enables the machine operator to make the necessary changes on the stand-by print machine, like change label roller and/or ink color in cycle, and be ready for the next change in print task. Thus, the label change can be accomplished on-the-fly with little unprinted stock, virtually no waste of plastic and, at no sacrifice to plant capacity.

10

machine or gravure printing machine

12

rigid frame

14, 16

first and second assemblages, or printing means

18

print roller of the first assemblage

20

impression roller of the first assemblage

22

ink trough

24

ink or other media (die, and so forth)

26

nip of first assemblage

28

nip of second assemblage

30

print roller of second assemblage

32

impression roller of second assemblage

34

print roller radial surface

36

impression roller radial surface

40

servo hydraulic system

42

doctor blade assembly

44

protective curtain

46

safety guard switch

48

rheostat for printer speed control

50

logic circuit for safty interlocks

52

gravity return valve for printer 14

54

ink supply valve for printer 14

56

logic circuit for supply valve

58

doctor blade position valve for printer 16

60

logic for doctor blade position valve

62

rheostat for machine speed control

64

PLC (programmable logic controller) impression roller position controller

68

curtain interlock switch for printer 16

70

printer select switch

72

logic circuit for curtain interlock

74

PLC impression roller position controller

76

rheostat for machine speed control

78

ink supply valve for alternate printer 16

80

gravity return valve for printer 16

82

curtain interlock switch for printer 14

84

doctor blade position valve for printer 14

86

maintenance operation

Claims

1. Machine for continuously conveying and processing web, comprising:

a frame;

a first conveyance assemblage arranged in a portion of the frame, the first assemblage comprising first and second surfaces mounted for at least partial contact, the at least partial contact defining a first nip, and wherein the second surface is selectively retractable away from the first nip;

a second conveyance assemblage arranged for at least partial cooperation with the first conveyance assemblage in another portion of the frame, the second conveyance assemblage comprising third and fourth surfaces mounted for at least partial contact, the at least partial contact defining a second nip, and wherein the fourth surface is selectively retractable away from the second nip; and,

means for controllably conveying the web between the first nip of the first conveyance assemblage and the retractable retracted fourth surface of the second conveyance assemblage; the controllably conveying means being alternately capable of coveying and the web between the second nip of the second conveyance assemblage and the retractable retracted second surface.

2. The machine recited in claim 1 wherein the first and second surfaces of the first conveyance assemblage and the third and fourth surfaces of the second conveyance assemblage are generally cylindrical rollers.

3. The machine recited in claim 2, wherein the second surface of the first conveyance assemblage and the fourth surface of the second assemblage comprise a compliant layer on at least a circumferential portion of the generally cylindrical rollers.

4. The machine recited in claim 3, wherein the means for controllably conveying comprises a controller means for selectively, controllably retracting the retractable second or fourth surface away from its corresponding nip while sequentially repositioning either of the fourth or second surface in at least partial contact and alignment with its corresponding first or third surface.

5. The machine recited in Claim 4, wherein the retractable second and fourth surfaces are retracted by a servo hydraulic means operatively connected to the controller means, the second and fourth surfaces being retracted transversely along a portion of the frame.

6. A gravure printing machine, comprising:

a frame;

a first printing means arranged in a portion of the frame, the printing means comprising: a first, retractable impression surface; a first print surface positioned in proximity to the first, retractable impression surface for at least partial contact therewith, the at least partial contact defining a first image transfer nip; and, means for providing travel of the web through the first image transfer nip;

a second printing means arranged for at least partial cooperation with the first printing means in another portion of the frame, the second printing means comprising: a second, retractable impression surface; a second print surface positioned in proximity to the second, retractable impression surface for at least partial contact therewith, the at least partial contact defining a second image transfer nip; and, means for providing travel of the web through the second image transfer nip; and,

means for selectively conveying and processing the web between one of the first or second image transfer nip and one of the second or first impression rollers while the second or first impression roller is retracted from the corresponding second or first image transfer nip.

7. The machine recited in Claim 6, wherein the first and second print surfaces and the first and second impression surfaces are generally cylindrical rollers.

8. The machine recited in Claim 7, wherein the means for selectively conveying and processing comprises a controller means for controllably retracting one of the retractable impression rollers from one printing means away from its corresponding image transfer nip while sequentially repositioning the other retractable impression surface in at least partial contact and alignment with its corresponding print roller of the other printing means.

9. The machine recited in Claim 7, wherein the impression roller is retractable transversely along a portion of the frame by a servo hydraulic means and wherein the portion of the frame includes a guide means for accommodating the retraction of the impression roller along a predetermined path in the frame.

10. The machine recited in Claim 6, further comprising a portable, removable barrier positioned between the retractable retracted impression surface and the corresponding print surface for protecting the web from exposure to contaminants.

Drawing