US2641183A

US2641183A - Image-reproducing plate and cylinder assembly

Info

Publication number: US2641183A
Application number: US40595A
Authority: US
Inventors: Jr John A Boyajean
Original assignee: Fairchild Camera and Instrument Corp
Current assignee: Fairchild Semiconductor Corp
Priority date: 1948-07-24
Filing date: 1948-07-24
Publication date: 1953-06-09
Anticipated expiration: 1970-06-09
Also published as: US2668498A

Description

June 9, 1953 J. A. BOYAJEAN, JR 2,641,183

IMAGE-REPRODUCING Ppgrr; AND CYLINDER ASSEMBLY Filed July 24, 1948 3 Sheets-Sheet 1 INVENTOR- Johnfl ay z 'eaggcfii' ATTORNEY J1me 1953 J. A. BOYAJEAN, JR 2,641,183

IMAGE-REPRODUCING PLATE AND CYLINDEFR ASSEMBLY Filed July 24, 1948 3 Sheets-Sheet 2 1 sa iij 11% INVENTOI? III r John H.130 a ea,Jr..

A E rm I- ATTORNEYS Patented June 9, 1953 IMAGE-'REPRODUCING PLATE AND CYLINDER ASSEMBLY 36min. Boy a eap, Upper miipuaian. J.,

Corporation, a corporation tr Delaware Application July 24, 1948, Serial No. 40,595 2 (llaim's. (c1. 101 4'15i) 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 sub-assembly of a machine for producing screened relief pattern plates of the type described in applicants copending application, Serial No. 40,594, filed concurrently herewith, now Patent 2,575,546. p

In aforesaid copending application there is described a machine designed and intendedto' be used in the placeof 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 pickup system and a plate-deforming tool for re} spectively 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 synchroneusly; and an e1ec= trical screen generator driven synchronously with the cylinders and connected to modulate the output of the pick-up system. I

It an object of the present invention, there'- fore, to provide a new and improved image-reproducing plate and cylinder assembly which, while of general application, is particularly use ful as a sub-assembly in a machine of the type described. t

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

It is another object of theinvention to pro vide 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.

Inaccordance with the invention, there is pro: vided for use in a machine of the type described an image-reproducing plate and cylinder assembly comprising an image-reproducing plate of flexible deformable material having parallel pre formed tensioni-ng flanges at either end thereof and a supporting cylinder mechanism havin previsionssu-pport ing it for rotation. The cylinder' mechanism has a longitudinal slot extendn a, L a

seats-ea; relief 2 mg is its periphery and a cylindrical recess ex tending longitudinally through said cylinder mechanism and inlo'ngitudinal communication with said slot. At last one tensioning member is disposed irithe' slot and is movable transverse- 15 thereof. The cylinder mechanism also ineludes a pai of oppositely inclines slots, at least one or which is in the tensioni ng member disposed to receive the flanges of theplate and lindrical cammin'g means rotatab'ly disposed in said recess endangering said tensioriing member substantially along its entire length for moving the te'nsioning member transversely of the' slot to tension the p ate about the c y'u ider and far locking said tensioniiig member in its tnsio'r'iing ti oni By the term aersrmam material, as used herein and in tneapniidea claims, is meant a material that may be cut, gauged, a ecmfipdseatf otherwise deformed an engraving tool or Sty-'- his to form image-es imati g plate.

For a lotteij understanding of the present in venues, together with other an further objects thereof, refe ric is to the renewing description taken in. connection the accompanying drawings, and its scope will be pointed out in the apperi (1 emails.

Refei'ring' new t ar drawings, Fig. 1 s; a schematic pe spective view or a machine of the type de'sci" 'e'dincluding a plate and cylinder assembly embodying the present invention; Fig. 1A is a fragz fientary view the cylinder supporting shaft oil the machine of 171g. 1; Fig. 2 is en: largd fragmentar elevation, partly in secede, oi the plate and cylinder assembly of the invention; Fig. 3 is a cross-sectional View taken along line 3 3 or Fig. 2 fl is a cross sectional viewtaken along 4 -4 of Fig. 2; Fig. 5 is a perspective view of a blank printing plate 'iii+ bodyirig a feature of the invention; Figs. 6 and 7 areenlargd fragmentary cross-sectional views Oftll plate and eyiineer assembly of Fig, 2 iiiustrating thejplate-tenslciiing member in open and closed positions, respectively.

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

Referring now more pairs-any to l, were s; illustrated schematically a machine for prcidiicing tea t me from an image sheet a H 7 pattern suitable for image reproduction'by p ting processes. This machine include an ele H i drivingmotor 29 which directly motivates; all moving parted: the machine extent the renaissance neared stylus. The' motor cludes a. shaft 2! connected as by a flexible care pling 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 fly wheel 21. The flexible coupling 22 mechanically filters or smooths out any pulsation which the rotation of the motor may possess, while the fly wheel ensures pulsationless rotation of the 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 28 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 alternating-voltage 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 l9, 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 de-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 sup orting 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 dotted-l ne 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 righthand 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 39. A second cylinder, generally ind cated at 4B, is rovided to sup ort the subiect 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 I. It may now be seen that when motor 20 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 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 carriagegenerally 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 43 which supports a scanning head generally indicated at 50. Carriage 41, in turn, includes a bracket 5| having a rearwardly extending plat-- form 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 55 which when energized swings 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 BI], 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 adjust-able 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 which meshes with a worm 66 mounted on shaft 3|. It may now be seen that, as shaft 3| is driven by motor 20, 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 53 along paths parallel to the common axis of

cylinders

40 and 32.

As scanning head 50 scans the subject copy, for example, a photographic print 61 on cylinder 40, it transmits a succession of signals whose amplitudes vary proportionally to the shade or tonal values of the print. At the same time, the generator 29 produces an alternating voltage of screen frequency, for example, 350 cycle/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 5'! 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 50. Stylus 51a, which is heated (by means not shown) to a temperature in excess of l000 F., has a tapered point and burns a pit in an image-reproducing plate 68 mounted in 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 30 of alternatingvoltage generator 29 is mounted on one end of a shaft 69, the other end of which carries a pulley l0. Trained about this pulley is a drive cable II which is supported by guide pulleys l2 and T3, and is trained about a third guide pulley 14. One run of cable H is attached to a post 15 fastened to stylus bracket 5|, while the other end is returned to post I through the intermediary of astilf spring Ha. Thus, as the stylus is driven to the left, it in turn drives cable 1l,. causing pulley l6 and accordingly shaft 69 and ring 39 to rotate very slowly. This rotation of thering 30 relative to the stylus carriage 4'! shifts the phase of alternating voltage developed by generator 29 by one-half cycle for each complete revolution of the cylinder 32, thereby to produce the.

staggered pit relationship referred to.

The above description of the machine shown in Fig. l is included herein toclarify what follows. For a detailed description of the features of construction and operationof this machine, referonce is made to the aforementioned ccpenclina application.

As pointed out above, the image-reproducing plate 68 is formed of a material that will decompose or disintegrate upon the application of suffn cient heat with little or no ashy residue. It is. of course, vital that such thermal decomposition be limited to minute localized areas, that is, to only that portion of the plate engaged by the hot stylus 57a, 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 rotogravure plate. These same plate surfaces must also be preserved with the greatest definition possible Where the plate is used as a rotogravureiprinting plate. It accordsingly 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 as a sub-assembly or compo"- nent part thereof the plate and cylinder assemblynow to be described in greater detail.

This assembly, comprising cylinder mechanism 32 and plate 68, is shown in enlarged detail in Figs. 3, and 4. Referring to Fig. 4, cylinder mechanism 32, which is formed of a metal having good heat conducting. properties, such as steel or aluminum, comprises a hub which is preferably longitudinally coextensive with the cylinder, this hub mounting the cylinder on shaft 33.- The cylinder also includes a rim t6, the outer surface of which forms the supporting surface for the underside of blank plate 68. mm i6 is connected to hub 15 by a web 1'! and a body portion 19 which, with the web, form longitudinally extending openings 80- and 8!. These openings extend longitudinally throughout the cylinder.

As is more. clearly shown in Fig. 6', body portion 19 is longitudinally drilled to prov-idearecess 82 in one side of cylinder body portion 19, specifically a longitudinal slot of circular cross section. Disposed in the recess or slot 82 is a carnrning means in the form of an elongated. cylindrical cam 83 rotatably mounted therein. As shown in bets or levers M and. 85, respectively (see 2.)

for operating the cam. Each. oithese levers,

example, lever 85, includes ashank 86011 the end.

of which is formed a boss 87. This bossis drilled. slidably to receive a pin 88, which is spring-biased as by a spring 89 to force the end of the pin into a hole 90 formed in the cylinder rim, thus to hold the lever in a closed position. Pin 88 includes a knurled head 9! which may be grasped to with draw the pin from hole 90 against the pressure of sprin as, when it is desired to swing'the lever. Lever 84 is similar in all respects to lever 85. Hence, it follows that the levers may be swung in unison to rotate shaft 83, for a purpose to be described.

Also formed in body portion 19 of cylinder!!! is. a longitudinal slot Of T-shapd cross Sc'tloh and including a channel 93 communicating with slot '82 and a channel 94 (forming the stem of the'T) extending to the periphery of the cylin der. Disposed in the

slot comprising channels

93 and 94 is an elongated tensioning member 95, also of T-shaped cross section, and slidable transversely of the

slot comprising channels

98 and 94. The opposite sides of the slot 94 limit the movement of the tensioning member 95.

A plurality of springs 98 are disposed within channel 93 between one side of head 95a of tensioning member 95 and the adjacent side of the channel, and these springs bias member 95 to the left, as viewed in Fig.- 6, that is, toward its open position. It may now be seen that when cam 83 is rotated clockwise, edge 83d thereof engages the left-hand side or head 95a and moves the member 95 transversely of the

slot

93, 94 against the pressure or springs 98, from its open position (Fig. 6) to its closed position (Fig. 7). This movement of the member 95 is accomplished upon rotation of cam 83 through 90", whereby edge 83a of the shaft disengages the member 85 and locks the member 95 against inadvertent re-' turn to its open position. Movement of the meme ber 95 to its open position is effected by springs 88 upon counter-rotation. of cam 83 to the Fig". 6 position.

By reason of the weight of cylinder body 19 and the weight of cam 83 and member 95, cylinder 32 is out of balance. To correct this, the cylinder is preferably drilled at 99, and the hole provided thereby is loaded with a sufiicient amount of lead I60 to restore the balance of the cylinder, thus to avoid undesirable pulsations during the rotation of the cylinder.

The cylinder .32 and tensioning member 95 are individually provided with oppositely incline-d slots disposed to receive tens'ioning' flanges" of plate 68 described in detail hereinafter. Specifically, shank 95b of the tensioning member has a slot 96 cut therein, the general plane of this slot forming with a tangent to the cylinder at point A an acute angle of th order of 30. At entrant end of slot 95, portion 950 of shank 95b is provided with a radius 91, the plane of the surface 95d of the stern of the member 95 being approximately tangent to the cylinder Surface at point A.

A Slot [0| is also cut in portion 19d of the cylinder body and the general plane of this slot forms an acute angle of the order of 30 with 'a tangent tothe surface of cylinder '32 at point B, a radius H32 on the cylinder portion adjacent the entrant end of the slot being provided. Inasmuch as th tangents at points A and B of the cylinder surface makesimilar angles with the surface 25d, the two slots 96 and NH bear similar but oppositely dirccted-ansu a ty .-S h.

face. Slot 96 is deeper than slot IOI for a purpose described below.

In Fig. 5 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 por-- tion I04, the under surface I05 of which is finished to a true and flat surface. The upper or outer surface I06 (Fig. '7) 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. At either end, the plate 68 is provided with parallel preformed reversely bent flanges I01 and I08 (Fig. 5), each of these flanges forming with plate body I04 an acute angle which preferably corresponds approximately to the angle of 30 of slots 96 and NI (Fig. 6). These flanges I01 and I08 are of a substantial rigidity and constitute provisions for tensioning the plate 68 about the cylinder 32, as described hereinafter. The flanges are so formed as to leave radii I01a and I08a of substantially the same value as radii I02 (Fig. 6) on the cylinder and radius 91 on T-bar 95. Furthermore, the distance between planes which are normal to plate 68 (Fig. 5) and which are respectively tangent to radii I01a and I08a is maintained as nearly uniform as practicably possible, so that the edges I09 and I I of the plate are parallel.

When plate 68 is mounted on cylinder 32, plate flange I01 is inserted in slot IOI. The body I04 of the plate is then wrapped around the cylinder 32 with its finished under surface I adjacent the cylinder surface, Plate flange I08 is then inserted in slot 96, whereupon the plate is ready to be tensioned or drawn into proper operative relation against the surface of the cylinder. It should be noted that the depth of slot IOI closely approximates the width of flange I01, while the depth of slot 96 exceeds the width of flange I08, for a purpose that will appear later.

With the plate 68 loosely mounted on the cylinder, and with its flanges I01 and I08 in the positions relative to slots IOI and 96 shown (Fig. 6), cam 83 is rotated clockwise by

levers

84 and 85 to move tensioning member 95 to the right to tension the plate 68 about the cylinder 32 and this tensioning is effected without the use of any accessory tools. As the member 95 so moves, force is exerted on the plate 68 adjacent its end III], with the result that flange I08 is forced into slot 96 until radius 91 of member 95 engages plate radius I08a. Continued movement of the member 95 places plate body I04 under tension, causing the plate body to move circumferentially relative to the cylinder surface until plate radius I01a abuts cylinder radius I02 and the under surface I05 of the plate is drawn into intimate engagement with the cylinder surface. Continuing movement of member 95 to the limit of its closing movement stretches the plate body so that the plate body is actually elongated. The effect of this is to perfect the engagement of all portions of the under surface I05 of the plate body with the surface of the cylinder, thereby establishing therebetween as good a heat transfer relationship as possible. While the plate is tensioned well below its elastic limit, the tension ing 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,

As pointed out hereinbefore, slot 96 is preferably somewhat deeper than slot I01. The reason for this is that, while it is not particularly difficult to hold the width of sheet flange I01 within fairly close tolerances, it is more diflicult so to dimension flange I08. This condition results from the efforts made to maintain the length of plate body I between edges I09 and H0 uniform and close to the required dimension. Hence, in view of the fact that plate flange I98 may occasionally be wider than flange I01, slot 06 is given sufficient depth to accommodate such excess width.

It should also be noted that through the provision of radii 91 and I02 on member and cylinder portion 19a, respectively, and b preforming plate flanges I08 and I01 in such a way as to provide radii I080. and I01a, the complementary plate and cylinder radii advantageously mate so that 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 I09 and H0 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 th 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 or greater is being out.

As noted hereinbefore, the plane of surface 95d of the member 95 is as nearly tangential as possible to the cylinder at point A. Hence, when the member 95 is actuated to tension the plate as described, the pull on the plate is approximately tangential at point A, which results in as low a frictional resistance between the under surface of the plate and the surface of the cylinder at point A as it is possible to attain while maintaining the plates entire under surface in engagement with the cylinder surface at this point.

It has been found that by exerting approximately tangential tension on the plate at point A, substantially all portions of the plate body between radii I01a and I08a are stretched, thus attaining the desired tensioning throughout all portions of plate 68 which assures the intimate engagement between the under surface of the plate and the surface of the cylinder. I 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 insuflicient material mass adjacent the pits formed by the hot stylus to conduct the heat away from the sides of the pits with suflicient 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 features of the cylinder to constitute a highly eflicient andeffective component of the machine.

As noted hereinbefore, shaft 33 (Fig. 1) of cylinder 32 is detachably secured to shafts 3| 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 parallel preformed tensioning flanges at either end thereof; a supporting cylinder mechanism having provisions supporting it for rotation and a longitudinal slot extending to the periphery thereof and a cylindrical recess extending longitudinally through said cylinder mechanism and in longitudinal communication with said slot; at least one tensioning member disposed in said slot and movable transversely thereof; said cylinder mechanism including a pair of oppositely inclined slots, at least one in said tensioning member, disposed to receive said flanges of said plate; and cylindrical camming means rotatably disposed in said recess and engaging said tensioning member substantially along its entire length for moving said tensioning member transversely of said slot to tension said plate about said cylinder, said camming means having a circular cylindrical surface portion engageable with said tensioning member for locking the same in its tensioning position.

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 parallel preformed tensioning flanges at either end thereof; a supporting cylinder mechanism having provisions supporting it for rotation and a longitudinal slot of T-shaped cross section with the stem of the T extending to the periphery of the cylinder and a second longitudinal slot of circular cross section extending longitudinally through said cylinder mechanism and in longitudinal communication with said T-shaped slot; at least one tensioning member of T-shaped cross section disposed in said slot and movable transversely thereof; said cylinder mechanism including a pair of oppositely inclined slots, at least one in said tensioning member, disposed to receive said flanges of said plate; an elongated cylindrical cam rotatably disposed in said second slot and engaging said tensioning member substantially along its entire length for moving said tensioning member transversely of said slot to tension said plate about said cylinder, said camming means having a circular cylindrical surface portion engageable with said tensioning member for looking the same in its tensioning position; and an operating member at at least one end of said cylinder mechanism for actuating said cam.

JOHN A. BOYAJEAN, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 657,358 Perry Sept. 4, 1900 1,550,452 Parker Aug. 18, 1925 2,047,364 Foster et al July 14, 1936 2,105,452 Busk Jan. 11, 1938 2,157,621 Neilson May 9, 1939 2,375,603 Willard May 8, 1945 FOREIGN PATENTS Number Country Date 535,076 Great Britain Mar. 27, 1941 641,173 Germany Jan. 23, 1937