GB2072097A - Registration control for multicylinder printing press - Google Patents

Abstract

An automatic control system for synchronizing the operation of a line of multiple cylinder presses in which unique circumferential indicators 10a, 10b, 10c on the cylinder 1 identify the different angular positions of the cylinder 1 to allow detection of the indicators and generation of a signal representing a unique multi-bit code word corresponding to each different angular position of the cylinder identified by the respective indicator. The signals representing unique multi-bit code words corresponding to different angular positions of the cylinder allow control circuits to automatically adjust the drive of one or more of the cylinders to maintain accurate synchronization. <IMAGE>

Description

SPECIFICATION Registration control for multicylinder printing press The invention relates to registration control for a printing press comprising a number of transfer cylinders to be driven synchronously.

In a printing press employing multiple transfer cylinders for partial images which are successively transferred and collectively form a total image which may or may not be colored, a problem arises in the maintenance of the respective partial images printed in the correct place in relation to one another. Not merely the angular velocities of the respective cylinders, but also the momentary angular positions must be determined accurately in relation to one another. Mechanical control systems are known by which change in the instantaneous relative angular positions of the different transfer cylinders is monitored by a constant visual checking of the final image for deviations.These systems nevertheless have the disadvantage that there is a slow reaction to deviations and when deviations occur, relatively large amounts of material are lost before restoration of the correct relative cylinder angles can be achieved.

Automatic control systems have been developed for synchronizing the operation of a line of multiple cylinder presses. For example, United States Patent 3,896,377 discloses a method for measuring the relative angular positions of two cylinders by employing a counter registering the passage of alternate black and white lines of a grid count pattern mounted on the periphery of one of the cylinders, in which the leading edge of a white target on the first cylinder unblocks the flow of pulses to the counter from the grid of the second cylinder. U.K. Patent 1,434,875 discloses various means for monitoring a pattern or configuration of marks upon the periphery of a cylinder, for example, photoelectric action. The methods taught in these patents employ a counting technique to indicate the relative relationship between multiple rotating cylinders.

United States Patent 3,675,098 discloses a digital control system in which respective digital signals represent instantaneous angular or phase positions of the several presses in a line and each digital signal is differentially compared against a digital reference signal representative of a reference phase position.

The press control circuit includes a pulse generator, suitably a conventional binary coded decimal disc which is driven at the operating speed of the press such as being coupled directly to the press crank shaft to supply a digital signal which is representative of the existing press phase or angular position.

Consequently, the method disclosed in this patent does not include a device for sensing indicators on the periphery or circumference of the cylinder presses and does not allow the accuracy of measuring the relative position of the circumferential transfer surfaces themselves as provided in the digital control of the present invention.

According to the invention, unique indicators or marks are positioned along the circumference of printing cylinders to identify different angular positions of such cylinders. The marks cooperate with a detector which responds to typical rotating passage of each mark by generating a signal representing a unique multi-bit code word corresponding to respective unique angular position of the cylinder. The signals can be passed to a control circuitforcorrecting deviation in the relative angular angular positions of multiple cylinders by adjusting the drive of one or more of the cylinders.

Suitable indicators can be circumferential surface sections with a characteristic property which can have one of two states and are arranged in circumferential rows axially next to one another. Each row can cooperate with a separate scanner reacting to the relative property, such that each instantaneous scanning of the rows results in a unique pattern of simultaneously occurring scanner pulses from the detector constructed from the scanners, which pulse patterns represent in combination a multi-bit code for accurate determination of the angular position of the cylinder.

The various multi-bit words supplied by the detectors of the respective cylinders are preferably conveyed to a comparactor in which, by comparison of the respective position bit words, relative angular positions can be determined; the comparactor can then provide one or more correction signals, for example, employing the instantaneous angular position of one cylinder as a reference to control adjustment of the drive of the remaining cylinders in sufficient direction and magnitude to correct deviations.

In another embodiment, the multi-bit word signals supplied by the detectors of the respective cylinders are conveyed to a comparator in combination with bit words supplied by an independent originator of signals, and the comparator can provide control signals in response to deviations between the respective position words and reference words to correct the drive of the relevant cylinder(s).

In another aspect of this invention, a thin-walled transfer cylinder to be used in combination with a printing press as described above is provided with the rows of surface sections along its circumference forming unique axial patterns of light reflectivity cooperating with an electro-optical scanner.

In another example, surface sections can form unique patterns of electric charge cooperating with an electrostatic scanner.

Alternatively, the surface sections can form unique patterns of magnetic field interference cooperating with a magnetic scanner; depressed sections of the cylinder surface passing along the magnetic scanner can be employed to change the magnetic field of the scanner. Such a cylinder can be formed by applying pattern of electrically insulating surface sections to a cylinder matrix corresponding to the depressed sections to be formed in the cylinder and that then applying to this matrix by electrolytic means a metal coating forming the cylinder.

FIGURE 1 is a schematic embodiment of a printing press according to the invention; FIGURE 2 shows schematically a cylinder provided with three rows of marks cooperating with scanners; FIGURE 3 is an outline of a surface section of a cylinder provided with five rows of marks; FIGURE 4 is a schematic representation of a sec tion of a cylinder surface according to the invention cooperating with an electro-optical scanner; FIGURE 5 is a schematic representation of a cylinder provided with surface sections cooperating with an electrostatic scanner; FIGURE 6 is a schematic representation of a cylinder provided with a pattern of surface sections cooperating with a magnetic scanner; FIGURE 7 shows another embodiment of an electro-optical scanner; and FIGURE 8a upto and including 8d show the stages in the manufacture of such a cylinder.

Fig. 1 shows schematically three transfer cylinders 1, 2,3 which can, for example, be conventional screen printing cylinders or transfer cylinders as used in electrostatic printing. Each of these cylinders is driven so that it can rotate by means of a drive shown schematically 5, 6 respectively, each being provided with at least one control input 7,8,9 by which the speed of the corresponding cylinder drive can be controlled.

Unique marks schematically designated 10, 11, 12 are located along the circumference of each of the cylinders which will be explained in further detail below, and the marks cooperate with a detector 13, 14, 15 respectively, consisting of several scanners, the outputs of which are connected to a central processing unit 16. In the embodiment shown in Figure 1, the output of a reference detector 17 supplies reference signals, for example generated by marks 18 applied to a reference drum 19 which is driven at a constant speed by the drive 20.

The signals are conveyed to central processing unit 16 by the detectors 13,14, 15 which monitor the instantaneous angular position of the cylinders 1,2, 3 respectively and from which the speed of the relevant cylinders can be derived. By comparing the position signals of cylinder 1, it is directly possible to establish whether the instantaneous angular position of cylinders 2 and 3 coincides with that of cylinder 1 or whether one of these cylinders is in advance of or behind cylinder 1.If the latter is the case, a correction signal is supplied by processing unit 16 which is conveyed to the control inputs 8,9 of the cylinders 2 and 3 by which the drive speed of the relevant cylinder is increased or decreased, correction continuing until the instantaneous angular position of the relevant cylinder is restored to synchronization with that of cylinder 1.

As an alternative to employing a first cylinder as a reference, a standard signal generator can be used to produce position signals coordinated with the position signals produced by the detectors 13, 14, 15 whereby the drives 4,5 and 60f the respective cylin ders 1,2 and 3 are controlled so that the instantane ous angular positions of the cylinders are always coordinating with the reference value representing an angular position of synchronization. For example, reference drum 19 can be provided with reference patterns of marks 18 and can be driven at a constant speed by the drive 20.The reference marks are scan ned by the scanner 17 which supplies its output signals to the processing unit 16, this latter supply ing such control signals to the inputs 7,8 and 9 that the instantaneous angular positions of the drums 2 and 3 are always coordinated with that of the reference drum 19.

Fig. 2 shows schematically one of the cylinders, for example cylinder 1 with the rim marks 10 which in this case consist of three rows 1 0a, 1 0b, 1 0c along the circumference axially next to one another. The marks are in the form of light or dark spots with a minimum length, being indicated in the figure by the letter L. Each of the rows 10a, lOb, 10c is scanned separately by one of three light-sensitive elements combined to form the detector 13 and indicated schematically by the rectangles 13a, 13b, 13c. Each angular position H of the cylinder with respect to the reference position indicated by the vertical line X-X is indicated by a unique combination of three, respectively white or black marks 21 a, 21 b, 21 c.It is clear that in Fig. 2 the dimensions of the marks are exaggerated with respect to the dimensions of the cylinder. It is possible in practice to form marks having a dimension in the circumferential direction of 50 ELm m so that in the case of a cylinder with a total cir- cumference of, for example, 1000 mm an accuracy of 360 x rl 1 minute or an art per 60 10.0000 = ca.1 minute of an arc per 50,am can be achieved. Each selection of an angular position results in the detector 13 producing an output signal representing a bit code-word in which, for example, the dark spots represent a digit 1 and the light spots a digit 0. With an adequate number of rows, result ing in output signals produced by the detector 13 with a sufficient number of bits, it is possible to achieve a very high degree of accuracy.Thus, for example, the above described accuracy of 1 minute of an arc requires 14 bits, and 14 rows.

Fig. 3 shows an example of the so-called gray code in which five rows 22 up to and including 26 are used. If a black area represents a digit 0 and a white area a digit 1, the position indicated by the arrow 27 is identified by the code 1111 0, the position 28 by the code 111 0 0, and the position 29 by the code 11 1 0 1. The so-called gray code, is characterized in that upon a transition from one code-word to the next only one of the binary digit changes so that no nondefined intermediate values are possible. The use of such a code for angular coding is known. With code-words of five bits anular accuracy is normally inadequate since the preferable accuracy described above requires 14 bits.Scanning is carried out, for example along the line 31 with the detector 30 comprising in this case five scanners.

Figs, 4, 5 and 6 show various alternatives for the form of the marks. Fig. shows a cylinder wall 33on which marks are applied in the form of a pattern of particles of lacquer 34, for example obtained by means of a selective photo-etching process. The scanner uses two light conductors 35 and 36 respectively, each having a diameter of about 50 microns.

At the end of the light conductor 35 is a source of light and at the end of the conductor 36 an electro optical element which produces an electric pulse upon the incidence of light. If no lacquer is present, the incident light beam 37 is reflected via the surface of the cylinder 33 as a reflected light beam 38 into the light conductor 36, and the electro-optical ele ment produces an output pulse representing, for example, binary "1". If lacquer is present, the incident beam of light 37 is partly absorbed and partly reflected as a light beam 38' of considerably lower intensity, so that no output pulse occurs representing, for example, binary 0.

Fig. 5 shows an embodiment in which the marks are applied as a pattern of particles 40 of insulating lacquer applied to the cylinder surface 41. The particles of lacquer 40, applied to the surface 41 which moves in the direction of the arrow 42 are charged electrostatically by the corona generator 43 and the metal surface 41 of the cylinder does not hold a charge so that a distinction is made by the electrostatic scanner 44. The output pulse, representing, for example, binary "1" or"0", occurring at the output terminal 45 forms a bit of the multi-bit code-word which represents the angular position of the cylinder.

Fig. 6 shows an embodiment in which the marks are applied in the form of a pattern of hollows 50 which are or are not present in the cylinder surface 51. A magnetic scanner 52 is used in this case. Each scanner consists of a thin rod of ferromagnetic material 53 surrounded by the winding 54 which is connected to the oscillator 55. The passing of a hollow 50 below the rod 53 results in a change in the magnetic field distribution registered by the oscillator 55 producing at the output terminal 56 a pulse representing binary "1" our "0".

In the embodiments described, each row of marks is scanned by a separate scanner; the detector constructed from the scanners supplies the collective scanner pulses to form the distinctive signal representing the bit word corresponding to a single angular position of the cylinder.

Fig. 7 shows an electro-optical scanner which can be used in combination with a cylinder 51' in which the marks are applied as a pattern of hollows 50'.

Use is made here of a source of light 57 which is projected by the optical system 58 and 61 via the semi-transparent mirror 60 on the cylinder. The section 59' of the beam (approximately half the beam 59) is deflected to the left by the mirror 60 and the section 59" let through forms an image on the surface of the cylinder 51 '. If no hollow is present, a part of the reflected image is again reflected by the mirror 60 as a bundle 59"' (depicted in dashed form) and projected by optical system 62 onto the photo-diode 63 which is set in its saturation state and produces a diode current dependent on the size of the surface which is irradiated. The generation of an output signal as a function of the diode current takes place in the processor 64 indicated schematically.If a hollow 50' is present below the lens 61, a larger surface section is irradiated at 65 and this larger surface section projects beam 66 which is reflected by mirror 60 as beam 67 producing a larger spot of light on the photo-diode 63 and larger diode current; thus a clear distinction can be detected between the presence of absence of hollows in the cylinder wall.

Figs. 8a up to and including 8d show a preferred method of manufacturing a thin-walled cylinder provided with a pattern of hollows which can be employed in combination with the detector according to the embodiments shown in Figure 6 or 7 or can be filled with lacquer and then used in combination with a detector according to the embodiments shown in Figure 4 or 5. For example, the edge of a copper matrix 70 can be applied with rows of insulating islets 71 according to the pattern of the hollows to be formed in the final thin-walled cylinder. Then a cylinder, for example, of nickel, can be electrolytically deposited on this matrix in conventional manner. Initially, as indicated in Fig. 8b, no material 72 will be deposited on the insulating islets 71 but, as the deposition is continued, the spaces present will "close" and a cylinder 73 with the hollows 74 near its margin will be formed on the matrix 70. Fig. 8d shows a cross-section through the cylinder wall 75 fabricated by this method. The islets 71 are very thin and the recesses 76' corresponding to them are accordingly shallow.

Claims (14)

1. A printing press assembly comprising a plurality of transfer cylinders to be driven synchronously, wherein (A) at least one of said transfer cylinders includes a plurality of unique indicators located proximately along the circumference of the cylinder in spaced relation such that each indicator identifies a different angular position of the cylinder, and (B) one or more detector means for detecting said indicators and generating a signal representing a unique multi-bit code word corresponding to each said different angular position of the cylinder.

2. The assembly according to claim 1 further comprising a control circuit for automatically adjusting the drive of one or more of said cylinders in response to the signals from the detector means.

3. The assembly according to claim 2 wherein at least two of said cylinders include said indicators, said detector means are provided for the indicators on each respective cylinder, said control circuit includes a comparison means which receives said signals representing the multi-bit code words for comparison of the angular position of said respective cylinders and generates one or more correction signals to adjust the drive of one or more of said cylinders in response to deviation in the instantaneous relative angular positions of said cylinders for reestablishing synchronization of the cylinders.

4. The assembly according to claim 3, further comprising an independent reference means for supplying reference multi-bit word signals to said comparison means which compares said reference signals to the multi-bit word signals supplied by said detector means of said respective cylinders and generates said correction signals in response to said deviation indicated between said detector signals and said reference signals.

5. The assembly according to claim 1 wherein said indicators comprise cylinder surface sections having a characteristic property which can have one of two states and which are positioned in a plurality of rows arranged along said circumference and axially next to one another, each row cooperating with a separate scanner means reacting to the relevant property, said scanner means collectively comprised in said detector means such that each instantaneous scanning of the rows produces a pattern of scanner pulses forming said signal from said detector means.

6. The assembly of claim 5 wherein said surface sections are arranged in approximately 14 said rows in orderto provide 14 bits forming said codewords corresponding to said respective angular positions of said cylinder.

7. The assembly of claim 5 wherein the surface sections which are positioned axially next to one another from each said row form a unique pattern of light reflectivity cooperating with electro-optical scanner means.

8. The assembly of claim 5 wherein the surface sections which are positioned axially next to one another from each said row form a unique pattern of electric charge cooperating with electrostatic scanner means.

9. The assembly of claim 5 wherein the surface sections which are positioned axially next to one another from each said row form a unique pattern of magnetic field interference cooperating with magnetic scanner means.

10. Acylinder for use in a printing press assembly wherein said cylinder includes a plurality of unique indicators comprising deepened sections of the cylinder surface located proximately along the circumference of the cylinder in spaced relation for identifying different angular positions of the cylinder.

11. The cylinder according to claim 10 wherein said deepened sections are positioned in a plurality of rows arranged along said circumference and axially next to one another.

12. A method for fabricating a cylinder according to claim 10 or 11 comprising: A applying to a cylinder matrix a pattern of electrically insulating surface sections coinciding with said deepened sections to be formed in said surface, and B applying a metal coating by electrolytic deposition on said matrix to form said cylinder having said deepened surface sections.

13. A printing press assembly substantially as herein described with reference to and as illustrated in the accompanying drawings.

14. A method for fabricating a cylinder substantially as herein described with reference to and as illustrated in the accompanying drawings.