US2668498A - Image-reproducing plate and cylinder assembly - Google Patents

Description

Feb. 9, 1954 J. A. BOYAJEAN, JR 2,668,498

IMAGE-REPRODUCING PLATE AND CYLINDER ASSEMBLY Original Filed July 24, 1948 2 Sheets-Sheet 1 ATTO R NEY JOHN A. BOYAJEAN Feb. 9, 1954 J. A. BOYAJEAN, JR

IMAGE-REPRODUCING PLATE AND CYLINDER ASSEMBLY Original Filed Jul 24, 1948 2 Sheets-Sheet 2 INVENTOR. JOHN A. BOYAJEAN ATTORNEY Patented Feb. 9, 1954 IMAGE-REPRODUCING, PLATE AND CYLINDER ASSEMBLY John A.,Boyajean, J r., Upper Montclair, N. J assignor to Fairchild Camera and Instrument Corporation, a corporation of Delaware Original application July 24, 1948, Serial No. 40,595. Divided and this application February 9, 1951, Serial No. 210,170

3 Claims. (Cl. 101 --415.1)

This invention relates to image-reproducing plate and cylinder assemblies and, while it is of. general application, it is particularly useful as a component or subassembly of a machine for produeing screened relief pattern plates of the type described in applicants copending application, Serial No. 40,594, now Patent 2,575,546.

This application is a division of applicants copending application, Serial No. 40,595, filed July '24, 1948, entitled Image-Reproducing Plate and Cylinder Assembly, now Patent 2,641,183.

In aforesaid copending application, Serial No. 40,594,v now Patent 2,575,546, there is described a machine designed and intended to be used in the place of well-known photo-chemical processes for making plates from photographic prints, negatives, or other images for reproduction by printing or like processes. In general, that machine comprises a pair of synchronously rotatable cylinders for individually supporting a plate and an image sheet and a pair of reciprocable carriages individually including a pick-up system and a plate-deforming tool for respectively scanning the image sheet cylinder and the plate cylinder. The machine also includes means responsive to the output of the pick-up system for actuating the tool, means for reciprocating the carriages synchronously; and an electrical screen generator driven synchronously with the cylinders and connected to modulate the output of the pick-up system.

It is an object of the present invention, therefore, to provide a new and improved imagereproducing plate and cylinder assembly which, while of general application, is particularly useful as a sub-assembly in a machine of the type described.

It is another object of the invention to provide a new and improved image-reproducing plate and cylinder assembly of maximum simplicity in construction, of maximum facility in assembly and disassembly, and capable of use by an unskilled operator.

It isanother object of the invention to provide a new and improved image-reproducing plate and cylinder assembly in which the plate to be formed is securely fixed to its supporting cylinder and tensioned to provide a smooth surface upon which the image to be reproduced is formed.

In accordance with the invention, there is prnvided for use in a machine of the type described an image-reproducing plate of flexible defprmable' material having notched ends with parallel preformed tensioning flanges at either end thereof and a supporting cylinder mecha! nism having provisions supporting it for rotation. The cylinder mechanism has a longitudinal slot extending to its periphery and notched complementarily to the notched plate and two groups of interleaved tensioning members disposed in the notches of the slot and movable transversely thereof in opposite directions. The groups of tensioning members include two series of slots disposed to receive the flanges of the plate. The cylinder mechanism also includes means for moving the tensioning members transversely of the slot to tension the plate about the cylinder.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointe out in the appended claims.

Referring now to the drawings, Fig. l is a schematic perspective view of a machine of the type described including a plate and cylinder assembly embodying the present invention; Fig. 1A is a fragmentary view of the cylinder supporting shaft of the machine of Fig. 1; Fig. 2 is a perspective view of a blank printing plate embodying a feature of the invention; Fig. 3 is a fragmentary elevation of the plate and cylinder assembly of the invention; Figs. 4 and 5 are enlarged fragmentary cross-sectional views along the line t 4 of Fig. 3, showing the plate-tensioning members of the cylinder in open and closed positions, respectively; while Fig. 6 is an end view of the cylinder of Fig. 3, showing the operating member by which the plate-tensioning members are opened and closed.

Similar reference characters refer to similar parts throughout the views of the drawings.

Referring now more particularly to Fig. 1, there is illustrated schematically a machine for producing on a plate from an image sheet a screened relief pattern suitable for image reproduction by printing processes. This machine includes an electric driving motor 20 which di-- rectly motivates all moving parts of the machine except the reciprocable heated stylus. The motor includes a shaft 2] connected as by a flexible coupling 22 to a shaft 23 on the end of which is mounted a worm 24. Worm 24 meshes with a worm Wheel 25 fastened to a shaft 26, on which is mounted a flywheel 21. The flexible coupling 22 mechanically filters or smoothes out any pulsation which the rotation of the motor may possess, while the flywheel ensures pulsationless rotation of shaft 26, regardless of irregularities that might otherwise be produced through imperfections in the worm and worm wheel.

Shaft 26 has mounted. on its left-hand end a metallic disc 23 having a number of equally spaced teeth 29 formed on its periphery. This disc operates in conjunction with an insulated metallic ring 30 having equally spaced teeth (not shown) formed on its inner periphery, the ring and disc constituting an electrostatic type of alternatingvoltage generator. The disc and ring comprise a half-tone screen generating device which provides an alternating voltage which is used to provide a screen for the subject copy.

On the right-hand end of shaft 26 is an overrunning (one-way drive) clutch |9, the driving element of which is secured to shaft 26, and the driven element of which is secured to a shaft 3|. This clutch allows fly wheel 21 to decelerate when motor 20 is ole-energized, without imposing an undue back load on the speed-reducing worm and worm wheel, and also allows the operator manually to rotate shaft 3|, if desired.

Shaft 3| comprises the drive shaft for the image-reproducing plate and supporting cylinder assembly of the invention including a supporting cylinder mechanism 32, this cylinder having provisions for supporting it for rotation, for example, a shaft 33. The left-hand end of shaft 33 is detachably secured to drive shaft 3| by a separable connection 34, which is shown in greater detail in Fig. 1A. Thus, the right-hand end of shaft 3| and the left-hand end of shaft 33 are milled to half rounds, the end of shaft 3| carrying an attaching pin 35. This pin is adapted to extend into a hole 36 formed in the half-round end of shaft 33, thus to connect the two shaft ends. A slidable collar 31 is movable from its full to its dottedline position over the half-round ends of the shafts detachably to secure these ends together, any suitable means being provided to hold the collar in its locking position. The right-hand end of shaft 33 (Fig. 1) is detachably secured as by another coupling 34 to the left-hand end of a shaft 38, the right-hand end of which carries a clutch disc 38. A second cylinder, generally indicated at 40, is provided to support the subject copy and this cylinder is mounted on a shaft 4|. On the left-hand end of shaft 4| is a clutch disc 42 which is a complement of disc 39, either of these discs, for example, disc 39, being movable relative to the other as by a lever system 43 to engage the discs and thus form a driving connection between shafts 38 and 4|. It may now be seen that when motor 23 is energized, shafts 3|, 33, 38, and 4| are all driven at the same rate of speed so as to effect rotation of plate-supporting cylinder 32, and the copy-supporting cylinder 40.

Underlying cylinders 32 and 43 are a pair of guide rods or ways 44 and 45, which are parallel to the common axis of the two cylinders. These guide rods slidably support a scanning carriage generally indicated at 46, and a deforming tool or stylus carriage generally indicated at 41, these carriages being respectively juxtaposed to copysupporting cylinder 40, and plate-supporting cylinder 32.

Scanning carriage 46 includes a bracket 48, or the like, which is supported by guide rods 44 and 45 and has a rearwardly extending platform 49 which supports a scanning head generally indicated at 50. Carriage 41, in turn, includes a bracket having a rearwardly extending platform 52, on which is mounted the stylus head, generally indicated at 53. Head 53 includes a base 54 which is pivotally attached in any suitable manner to platform 52; a holding magnet (not shown) which when energized swing the cutter-head into proper operating position relative to cylinder 32 against the action of a retracting spring 56, and a stylus and driving motor therefor, generally indicated at 51.

The scanning and stylus carriage brackets 48 and 5| are driven by a belt 58 which is trained about drive and guide pulleys 59 and 60, respectively, the bracket 5| being fixedly attached to the belt 58 and the bracket 48 being releasably attached thereto by an internal clutch (not shown) actuated by an adjustable knob 48a. Drive pulley 59 is fastened to one end of a shaft 6|, whose other end carries a worm wheel 62, meshing with a Worm 63. This worm is mounted on the lower end of a shaft 64, whose upper end carries a worm wheel 65 which meshes with a worm 66 mounted on shaft 3|. It may now be seen that, as shaft 3| is driven by motor 2!], drive pulley 59 is rotated at a low R. P. M. through the reduction afforded by worm 66, Worm wheel 65, worm 63, and worm wheel 62, accordingly to drive belt 58 at a very low rate of speed, thus to move the scanning and stylus heads 50 and 63 along paths parallel to the common axis of cylinders and 32.

As scanning head scans the subject copy, for example, a photographic print 61 on cylinder 43, it transmits a succession of signals whose amplitudes vary proportionally to the shade or tonal values of the print. At the same time, the gen erator 29 produces an alternating voltage of screen frequency, for example, 350 cycles/second. This screen voltage is amplified and varied in amplitude or modulated by the signals developed by the scanning head 50 and fed to the stylus motor 51 which oscillates its stylus 51a at the frequency of the screen voltage and with an amplitude varying with the image signals from the scanning head 58. Stylus 51a, which is heated (by means not shown) to a temperature in excess of 1000 F., has a tapered point and burns a pit in an image-reproducing plate 68 mounted on cylinder 32 at each stroke, the depth and surface area of successive pits accordingly being a function of the amplitude of successive signals transmitted by the scanning head. Accordingly, there are formed in plate 68 a large number of regularly spaced pits of areas varying with the shade values of the subject copy or print 61, leaving islands therebetween forming the printing surface and also of areas varying with the shade values of the print 61.

It is desirable that the pits formed in adjacent lines of plate 68 be in staggered relationship to provide the half-tone screen effect which characterizes the conventional photo-engraving process. To this end, the ring 33 of alternatingvoltage generator 29 is mounted on one end of a shaft 69, the other end of which carries a pulley 10. Trained about this pulley is a drive cable 1| which is supported by guide pulleys 12 and 13, and is trained about a third guide pulley 14. One run of cable 1| is attached to a post 15 fastened to stylus bracket 5|, while the other end is returned to post 15 through the intermediary of a stiff spring 1|a. Thus, as the stylus is driven to the left, it in turn drives cable 1|, causing pulley 10 and accordingly shaft 69 and ring 30 to rotate very slowly. This rotation of the ring 30 relative to the stylus carriage 41 shifts the phase of alternating voltage developed'by generator 23 by one-half cycle for each complete revolution of the cylinder 232; thereby to produce the staggered pit relationship referred to.

The above description of the machine shown in Fig. 1 is included herein to clarify what follows. For a detailed description of the features of construction and operation of this machine, reference is made to the aforementioned copending application, Serial No. 40,594.

the hot stylus 51a, at each stroke thereof. In

other words, the portion of the plate surrounding the pit formed by the stylus must be left intact, as it is the plate surfaces between the dots or pits formed by the stylus that carry the ink where the plate is used as a half-tone or roto- 'gravure plate. These same. plate surfaces must also be preserved with the greatest definition possible where the plate is used as a rotogravure printing plate. It accordingly follows that the plate must not only have certain characteristics, but also must be properly supported during the "engraving operation if the picture to be printed by the completed plate is to have the sharp definition and tone gradation required. Thus, where the blank plate is made of a highly combustible material, such as, for example, nitro-cellulose, it .is necessary that the thermal decomposition. of the material caused by the engagement thereof by the hot stylus be narrowly controlled, not only to attain the aforementioned definition, but also to avoid any danger of a serious fire. To this end, the machine described includes a sub-assembly or component part thereof the plate and cylinder assembly now to be described in greater detail.

In Figs. 3-6, inclusive, there is shown such a plate and supporting cylinder assembly embodying theinvention. The cylinder is generally indicated at III and comprises opposite end hubs H2 and H3, which may be attached to shaft 33 in any suitable manner. The cylinder III and hubs H2 and H3 are formed of a metal having good heat-conducting properties, such as steel or aluminum. Disposed between and secured to these hubs is a cylindrical shell H4, the outer surface of which constitutes the platesupporting surface of the cylinder. Extending through shell I I4 is a slot, generally indicated at I i5, having oppositely extending notched sections H6 and I H, the slot extending throughout the length of the shell.

As is shown in Figs. 3 and 4, two groups of interleaved tensioning arms H8 and H are pivotally mounted on shaft 33 and thus are pivoted about the axis of cylinder IH. Each of these arms includes a hub, such as hub E of arm H8, whereby the arm is supported on shaft 33, a plate-clamping finger I2 I, and a foot I22. Each of arms H9 correspondingly includes a hub I23, a finger I 24., and a foot I25. Thus, the finger and foot of each arm II8 are displacedlaterally by the thickness of their hub I20 from and are opposed to the finger I 24 and foot I25 of the complementary arm IIO. Finger I2I has an inclined slot I26 formed therein, finger I24 having an oppositely inclined slot I21. These slots I25 and I2I- form acute angles of the order of 30 with tangents to the surface of cylinder III at their respectiveentrances. The end of each anfel'l lfl wtFig. 3).;extendsi into anotchxsection H6 of slot II 5, while the end of each finger l-24 extends into a notch section I I! of slot I I5, these two groups of finger ends being movable transversely of the slot I I5 in opposite directions, such movement being limited by the circumferential extent of the notched slot. The groups of arms H8 and H0 are pivotally actuated in opposite directions by an elongated cam 528 (Fig. 4) whose opposite ends are fastened respectively to operating levers 84- and 85. Thus, when these levers are swung from their open position to their closed Fig, 3 position, cam I28 is rocked from its Fig. l position to its Fig. 5 position, this movement of the cam rocking arms H8 clockwise and arms H9 counterclockwise. This, of course, swings fingers I2] and I24 to their closed position shown in Fig. 3.

In Fig. 2 there is shown a blank image-reproducing plate 68 which, as indicated hereinbefore, is formed of a flexible deformable material, specifically, one which, upon ignition, will continue to burn without externally supplied oxygen, provided the material is maintained above the ignition temperature. An example of such a material is one consisting in substantial part of a nitro-cellulose such as cellulose nitrate, although other materials having the aforementioned property may be used. Plate 68 comprises a body portion I04, the under surface I05 of which is finished to a true and flat surface. The upper or outer surface of the plate may or may not be polished, as desired, but it is finished to a surface which is sufficiently flat and true for printing purposes. The opposite ends of the plate 68 .i' are notched, forming groups of fingers I29, I30

on either end thereof, the fingers of the two groups being staggered with respect to each other and proportioned to overlie the fingers I2I, I24, respectively, of the cylinder mechanism. The groups of fingers I 20, I30 are formed with parallel preformed reversely bent flanges I20a, I30a, respectively, forming with the plate body I04 acute angles of approximately 30 corresponding to the angles of the slots I 20, I21 of the fingers I2I, I24, respectively. The flanges I20a,

I30a are of substantial rigidity and constitute provisions for tensioning the plate 08 about the cylinder. The flanges I29a, I30a are so formed as to leave small radii I29!) and I301; of substantially the same value as the corresponding radii of the points of fingers I2I, I24. Furthermore, the distance between planes which are normal to plate 08 and which are respectively tangent to radii I29?) and I301) is maintained as nearly uniform as practicably possible, so that the edges of the plate are parallel.

When the plate 50 is mounted on the cylinder, the flange I29a on each of fingers I20 is inserted into the slot I 26 of arm finger I2I, while each flange I30a of fingers I30 is inserted into the slot I21 of arm finger I24, whereupon the plate takes the position shown in 4. It may then be seen that when cam shaft is rocked, as hereinbefore described, the opposed groups of tensioning arms H0, H9 are moved into the Fig. 5 position, thus tensioning plate 68 tightly about the cylinder surface. This provides nearly tangential movement of the ends of the plate 50 and has a low value of frictional resistance upon tensioning. Final movement of cam shaft 128 to the limit of its closing movement stretchesthe plate body so that the plate body is actually elongated. The effect of this is to perfect theengagement of all portions of the under surface I05of the plate body with. the surface of the; cylinder.

therebysstablishins.there etwecn. as som 1 w transfer relationship as possible. While the plate i tensioned well below its elastic limit, the tensioning has the further effect of smoothing out any ripples or waves in the plate so that the portion of the outer surface of the plate that is to be operated on by the hot stylus is as nearly exactly cylindrical as practicably possible. This condition of the outer surface of the plate assures uniformity of the depth of pits formed by the hot stylus over areas of the same tone value, so that uniform tone is produced by the plate during the printing operation.

By preforming plate flanges I29 and I30 in such a way as to provide radii I291) and I301) complementary to radii of the points of fingers I2 I, I24, undue stress is not localized at the plate edges when the plate is tensioned. Furthermore, by providing the plate radii referred to, it is not necessary to crease sharply the plate at edges thereof, which might weaken the plate.

The perfection of the heat transfer relation between the under surface of the plate and the supporting surface of the cylinder is attained both by reason of the intimate engagement therebetween due to the finished under surface of the plate. This relationship between the plate and cylinder is important because of the nature of the plate material. In other words, the intense heat created in the plate by the engagement thereof with the hot stylus must be conducted away from the plate as rapidly as possible or else the plate would continue to burn. It is equally important rapidly to conduct the heat from the plate in order that the individual pits formed by the hot stylus do not enlarge by continued combustion of the material forming the pit walls, after the withdrawal of the hot stylus. This is particularly true where a screen size of 120 or greater is being out.

It has been found that by exerting approximately tangential tension on the plate at either end substantially all portions of the plate body between radii I29?) and I301) are stretched, thus attaining the desired tensioning throughout all portions of plate 58 which assures the intimate engagement between the under surface of the plate and the surface of the cylinder. It might be noted that the under surface of the plate, in addition to perfecting the heat transfer relation referred to, also facilitates relative movement between the finished plate surface and the cylinder surface which, of course, occurs as the plate is stretched.

The importance of this close, tight engagement between the under surface of the blank plate and the supporting surface of the cylinder and the resultant heat transfer relationship effected thereby is further emphasized when it is pointed out that the thickness of the body of the plate may be of the order of 0.030 inch. With a plate as thin as this, it becomes clear that there is insuiiicient material mass adjacent the pits formed .by the hot stylus to conduct the heat away from the sides of the pits with sufficient rapidity to preclude continuing combustion at the pit walls, as would enlarge the size of the pits, and perhaps cause destruction of the plate. This is particularly true where the stylus penetration is maximum, as it would be where highlight tone values are being reproduced. Thus, the specific characteristics and properties of the blank plate combine in an advantageous manner with the structural and functional characteristics or feaiicient and effective com-ponent'of the machine.

noted-hereinbeforashaf't 33 (Fig. 1) of cylinder 32 is detachably secured to shafts BI and 38 by the separable connections 34. By so mounting the cylinder in the machine, and by providing the user of the machine with two cylinders, it is possible for the operator to set up a cylinder and plate unit at a station remote from the machine while the machine is operating on another cylinder and plate unit mounted in the machine. Inasmuch as the cylinder and plate unit in the machine can be detached therefrom and the second cylinder and plate unit thereafter fastened to shafts 33 and 38 in a very considerably less amount of time than it takes to mount a blank plate on the cylinder, it may be seen that valuable time is saved through the provision of the detachable mounting for the cylinder, and through the provision of a plurality of cylinder and plate units. Further, and perhaps even more important, is the fact that where an extra cylinder is available, the operator does not have to handle the blank plate close to the hot stylus and in the relatively confined space adjacent the cutterhead. This, of course, precludes the danger of the operator being burned by the stylus, or the plate coming in contact therewith and being damaged or spoiled. Of course, it is much easier to mount the plate on the cylinder when the cylinder is out of the machine.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a machine for producing on a plate from an image sheet a screened relief pattern suitable for image reproduction by printing processes, an image-reproducing plate and cylinder assembly comprising: an image-reproducing plate of flexible deformable material having notched ends with parallel preformed tensioning flanges at the ends of the notch-separating portions thereof and with notches on the two ends staggered with respect to each other; a supporting cylinder mechanism having provisions supporting it for rotation and a longitudinal slot extending to the periphery thereof and notched complementarily to said plate; two groups of interleaved tensioning members disposed in the notches of said slot and movable transversely thereof in opposite directions; said groups of tensioning members including a pair of series of slots disposed to receive said flanges of said plate; and means for moving said tensioning members transversely of said slot to tension said plate about said cylinder.

2. In a machine for producing on a plate from an image sheet a screened relief pattern suitable for image reproduction by printing processes, an image-reproducing plate and cylinder assembly comprising: an image-reproducing plate of flexible deformable material having notched ends with parallel preformed tensioning flanges at the ends thereof and with notches on the two ends staggered with respect to each other; a supporting cylinder mechanism having provisions supporting it for rotation and a longitudinal slot extending to the periphery thereof and notched complementarily to said plate; two groups of interleaved tensionmg arms pivotally.mountedabout. the axis of said cylinder and extending into said slot with their ends movable transversely of said slot in opposite directions, said groups of tensioning members including a pair of series of slots disposed to receive said flanges of said plate; and an elongated cam for pivotally actuating said groups of members in opposite directions to tension said plate about said cylinder.

3. In a machine for producing on a plate from an image sheet a screened relief pattern suitable for image reproduction by printing processes, an image-reproducing plate and. cylinder assembly comprising: an image-reproducing plate of flexible deformable material having parallel preformed tensioning flanges at the ends thereof; a supporting cylinder mechanism having provisions supporting it for rotation and a longitudinal slot extending to the periphery thereof; two groups of interleaved tensioning arms pivotally mounted about the axis of said cylinder 10 and extending into said slot with their ends movable transversely of said slot in opposite directions, said groups of tensioning members including a pair of series of slots disposed to re ceive said flanges of said plate; and an elongated cam for pivotally actuating said groups of members in opposite directions to tension said plate about said cylinder.

JOHN A. BOYAJEAN, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 348,736 Goodwin Sept. 7, 1886 657,358 Perry Sept. 4, 1900 2,109,152 Meisel Feb. 22, 1938 2,157,621 Neilson May 9, 1939 2,194,424 Grupe Mar. 19, 1940

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