US2143984A

US2143984A - Method of and means for engraving a printing surface

Info

Publication number: US2143984A
Application number: US134864A
Authority: US
Inventors: Owen R Huggins
Original assignee: PHOTO CYLINDER CORP
Current assignee: PHOTO CYLINDER CORP; PHOTO-CYLINDER Corp
Priority date: 1937-04-03
Filing date: 1937-04-03
Publication date: 1939-01-17
Anticipated expiration: 1956-01-17
Also published as: GB513175A

Description

Jan. 17, 1939. o, R HUGGINS 2,143,984

METHOD OF AND MEANS FOR ENGRAVING A PRINTING SURFACE Filed April 3, 1937 4 Sheets-Sheet l 11v VENTOR g BY lfj A TTORNEY Jan. 17, 1939. o. R HUGGINS IETHOD OF AND MEANS FOR ENGRAVING A PRINTING SURFACE Filed April 3, 1937 4 Sheets-Sheet 2 E M g m 1mm n Km Ewim: m

mm h mm H W n u 3 i n m A N NE INVENTOR A TTORNEY Jan. 17, 1939. o R. HUGGINS 2,143,934

METHOD OF AND MEANS FOR ENGRAVING A PRINTING SURFACE Filed April 3, 1937 4 Sheets-Sheet 3 a L L4 3. IN VE N TOR BY JMJM A TTORNE Y Jan. 17, 1939. o. R. HUGGINS METHOD OF AND MEANS FOR ENGRAVING A PRINTING SURFACE I Filed April 3, 1937 4 Sheets-Shoot 4 INVENTOR A TTORNEY Patented Jan. 17, 1939 UNITED STATES METHOD OF AND MEANS FOR momma A PRINTING SURFACE Owen R. Huggins, South Norwalk, Conn, assignor to Photo-Cylinder Corporation, a corporation of New York Application April 3, 1937, Serial No. 184,864

Claims.

This invention relates to methods of engraving a printing surface, and especially one of cylindrical form.

It is the present practice in engraving a cylindrical printing surface with an irregularly shaped design, to employ the so-cailed pantograph method, but there are certain objections to this method in that it is slow, costly, and incapable of properly reproducing half tones. For these and other rea- 0 sons, variousmethods have been suggested for engraving cylinders photomechanically, but thus far the methods suggested have been attended with but little success, as evidenced by the fact that none are at the present time being used commercially to any great extent.

The purpose of the present invention is to engrave irregularly shaped designs upon the printing surface of cylinders photomechanicaiiy by a method and means which are commercially practical and capable of reproducing the true tonal effects of the original design. According to the invention, an image of the irregularly shaped design that is to be engraved upon the printing surface of the cylinder is so reproduced upon a fiexible film, and the image area or that portion of the film upon which the image is reproduced is made equal in length to an aliquot part of the circum-' ference of the cylinder and in width to a fraction of the length 01 the printing surface of the cylinder. The cylinder is coated with a light sensitive substance and the film is positioned thereon with the image area over a portion of its sensitized surface. The image area is then brought undistorted into intimate contact with the underlying sensitized surface after which it is subjected to the action of light to create a reproduction of the design upon the sensitized surface of the cylinder. The position of the film is then changed longitudinally and circumferentially predetermined distances to successively bring the image area over the remainder of the sensitized surface of the cylinder. Each time the position 01' the film is so changed the image area is brought undistorted into intimate contact with the underlying sensitized surface after which it is subjected to the action of light to create a reproduction of the image upon the sensitized surface, and the distance the position of the film is so changed each time is such that the reproductions thus formed merge to form a continuous design.

After the continuous design has been thus formed thereon the sensitized surface is developed and otherwise treated, as is well understood in the art, to form an acid resist after which the cylinder is rotated in a corrosive bath to etch out the cylinder exposed by the affected areas of the sensitized surface. Then the cylinder is cleaned to remove the unaffected portions of the light sensitive substance after which it is ready for 5 printing purposes.

For a clearer understanding of the invention reference may be made to the accompanying drawings in which,

Fig. 1 is an elevational view of the machine employed in the present embodiment of the invention for transferring an image from a film onto a coating of light sensitive substance with which a cylinder is provided;

Fig. 2 is an end view in section, the view being taken along the line 2-2 of Fig. 1;

Fig. 3 is an end view in section, the view being taken along the line 3-8 of Fig. 1;

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 3

Fig. 5 is an enlarged sectional view showing the light source, the light hood and the film tensioning device employed in the machine shown in Fig.

Fig. 6 is an enlarged end view of the tensioning device shown in Fig. 5;

Fig. 7 is a plan view in section of the traveling carriage employed in changing the position of the image area of the film longitudinally with respect to the position 01 the cylinder, the view a being taken along the line 'I1 of Fig. 6;

Fig. 8 is an elevational view showing the relative positions of the cylinder, the film, and the light shields, which are employed to protect the regions of the sensitized surface of the cylinder 35 outside the area beneath the image area of the film at the time the initial reproduction is made on the sensitized surface of the cylinder;

Figs, 9, 10, and 11, are elevational views partially in section showing the relative positions of 40 the elements mentioned in connection with Fig.

9, but at the time the second, third, and fourth reproductions are being made along the length of the cylinder;

Fig. 12 is an end view in section of a fixing bath;

Fig. 13 is an end view in section of a cylinder after being removed from the fixing bath;

Fig. 14 is an end view in section of a cylinder after being treated after its removal from the fix ing bath; and

Fig. 15 is a plan view of the film from which an image is to be transferred to a cylinder.

In operation, the design to be engraved upon the printing surface of a cylinder III is photoraphically reproduced upon the central portion 2| of a flexible film 22, which portion is hereinafter referred to as the image area of the film. The length of the image area throughout its width is made equal to an aliquot part of the circumference of the cylinder and the width of the image area throughout its length is made any desired dimension although for economic reasons it is made small as compared to the length of the printing surface of the cylinder. In the present embodiment of the invention the length of the image area throughout its width is made equal to one half the circumference of the cylinder and the width of the image area throughout its length is made equal to approximately one quarter the length of the printing surface of the cylinder. It is to be noted, however, that due to the irregularities of the edges of the design the over all length of the image area is greater than one half 'the circumference of the cylinder and the overall width of the image area is greater than one quarter the length of the printing surface of the cylinder.

The image thus reproduced upon the image area 2| is transferred onto the surface of the cylinder 26 the number of times necessary to cover with an endless design that portion from which it is desired to print, and to this end the cylinder 26 is keyed to a mandrel 23 and it is provided with a coating of light sensitive substance 24. The mandrel'23 is journaled at its opposite ends in

split bearings

25 and 26 carried by

bearing assemblies

21 and 28 respectively that are supported by oppositely disposed frame members 29 and 36- which are maintained in spaced parallel relationship by a plurality of supporting legs 3|, and to prevent lateral displacement of the mandrel 23 it is provided with an annular groove 32 into which is positioned a key 33 carried by the cap portion of the split bearing 25. The film 22 is placed over the cylinder 26 with the image area 2| positioned adjacent one end thereof. The image area 2| is then brought undistorted into intimate contact with the underlying sensitized surface of the cylinder, and here it is to be noted that inasmuch as the over all length of the image area is greater than half the circumference of the cylinder the film must be brought into contact with more than half the circumferential surface of the cylinder. In the present embodiment of the invention wherein the width of the image area is small as compared to the length of the cylinder this intimate contact is brought about by bending the ends of the film backwardly and clamping the doubled ends thus formed between a bar 36 and a vertically movable block 31 by means of studs 38. The studs 38 are provided with a shoulder 39 which is positioned adjacent the outer face of the clamping bar 36, a shank portion 46 which extends through a hole in the clamping bar 36, and a threaded end portion 4| which is threaded into an aligned tapped hole in the block 31, and to automatically separate the clamping bar 36 from the block 31 to aid in removing the film when the studs 38 are backed off a compression spring 42 is positioned about the shank portion 46 of the end studs in a recess formed in the clamping bar 36. The block 31 is positioned between

gibs

43 and 44 carried by upstanding plates 45 and 46 respectively which form the end walls of a movable carriage 41. The side walls of the movable carriage 41 comprise spaced beams 48 and 49, and the end of each beam is provided with a journal box 56 having a shaft upon which a grooved roller 52 is mounted. The two rollers on the front beam 48 are positioned on a carriage guiding gib 53 which extends longitudinally along the top face of the front frame member 29 and the two rollers on the rear beam t9 are positioned on a similar gib 54 which extends longitudinally along the top face of the rear frame member 36.

The vertically movable block 31 is maintained in its normal raised position by means of springs 55 that are positioned in recesses in the lower face thereof and which rest on a cross plate 56 that is connected at its opposite ends to the end plates 45 and 46 of the movable carriage 41. To bring the image area 2| into intimate contact with the underlying portion of the sensitized surface of the cylinder 26 the block 31 is pulled downwardly from its normal raised position against the action of the springs 55, and to this end the upper end of a resilient strap 51 is secured by screws 58 between. the block 31 and a clamping bar 59. The lower end of the strap 51 is secured by a clamp 66 to a shaft 6| that is journaled at its opposite ends in the upstanding side plates 45 and 46 of the movable carriage 41. One end of the shaft 6| extends outwardly and it is provided with a hand wheel 62 and a ratchet wheel 63. A pawl 64 that is adapted and arranged to engage the teeth of the ratchet wheel 63 is pivotally secured to the upstanding side plate 46, and a spring 65 having one of its ends fastened to the free end of the pawl 64 and its other end fastened to the side plate 46 is provided to maintain the pawl 64 in engagement with the teeth of the ratchet wheel 63. To bring the image area 2| of the film 22 into intimate contact with the underlying portion of the sensitized surface of the cylinder 26, the shaft 6| is rotated by the hand wheel 62. As the shaft 68 rotates the strap 51 stretches and in stretching it pulls the block 31 and the blanket 34 down wardly and so carries the image area 2| without distortion into intimate contact with the underlying sensitized surface of the cylinder 26.

Since it is important that the image area 2| of the film 20 throughout its length be brought into intimate contact with the underlying sensitized surface of the cylinder 26 and since the normal raised position of the block 31 is fixed, the

split bearings

25 and 26 in which the opposite ends of the mandrel 23 on which the cylinder 26 is mounted are rendered adjustable to accord with cylinders of different sizes, and to this end the left hand bearing assembly 21 comprises a cross beam 66 having downwardly extending legs 61 which are secured in fixed position by pins 68 to the upper faces of the

frame members

29 and 36. The right hand bearing assembly 28 comprises a pair of superimposed plates 69 and 16 slidably mounted on the upper faces of the

frame members

29 and 36, and to guide the right hand assembly as it is moved along the

frame members

29 and 36 the lower plate 16 is recessed to accord with the guiding

gibs

43 and 44 on the upper faces thereof. To lock the right hand bearing assembly 28 in a desired position 'a stud 1| is positioned in aligned apertures in the superimposed plates 69 and 16. The lower end of the stud 1| is threaded through a clamping plate 12 positioned beneath shelves 13 on the

frame members

29 and 36 and the upper end of the stud is provided with a handle 14 which, when turned in one direction, rotates the stud to draw the clamping plate 12 into frictional engagement with the shelves 13 and which, when turned in 75 the opposite direction, rotates the stud to free the clamping plate from its friction engagement with the shelves. The central portion of the cross beam 66 of the left hand bearing assembly 21 is provided with a boss I5 through which the lower end of an adjusting screw 16 is threaded, and the central portions of the superimposed plates 69 and I of the right hand bearing assembly 28 are provided with aligned apertures through which the lower end of a similar adjusting screw 11 is threaded. The upper ends of the adjusting screws I6 and Il are provided with annular heads I8 which are maintained by means of apertured plates I9 in recesses in the lower faces of the

bearings

25 and 26. Turning the adjusting screws I8 and I1 acts to raise or lower the

bearings

25 and 26, and to aid in the turning of the screws they are provided with annular nuts 00 fixed thereto by set screws BI and having holes 82 adapted to receive the end of a turning tool. To guide the

bearings

25 and 25 as they are raised or lowered each assembly is provided with a pair of vertically disposed gibs 03 and 84 positioned in recesses formed in the outer side faces of the

bearings

25 and 26, and to lock the bearings after they have been adjusted to a desired position the adjusting screws I6 and I1 are provided with lock nuts 85 having holes 86 adapted to receive the end of a turning tool, the lock nut on the adjusting screw I6 of the left hand bearing assembly 21 serving, when brought into engagement with the upper face of the cross beam 66, to lock the left hand bearing 25 and the lock nut on the adjusting screw I1 of the right hand bearing assembly 28 serving, when brought into engagement with the upper face of the cross plate 69, to lock the right hand bearing 26 in position.

The image area 2| of the film 22 having thus been brought undistorted into intimate contact with the underlying sensitized surface of the cylinder 20, means are provided to prevent light from striking the sensitized surface of the cylinder except through the image area, and to this end as shown more clearly in Fig. 8, a pair of opaque sleeves 81 and 88 are positioned about the cylinder 20 adjacent the sides of the image area 2| and a semi-circular frame 89 having flaps 90 is positioned over the film 22 with the sides of the frame 89 adjacent the sides, of the image area 2| and with the flaps 90 extending downwardly in overlapping relationship with respect to the ends of the sleeves 81 and 88. The sleeves 81 and 88 are flexible and they may be made of strips of dark closely woven cloth re-enforced along oppositely disposed ends to support the male and female portions of snaps 0| by means of which these ends are brought together to form sleeves. The flaps 90 are made of like material and they are secured to the horizontally disposed ends of the semi-circular frame 89.

The sensitized surface of the cylinder outside the regions of the overlying image area 2| being protected, the image area is subjected to the action of light to create a reproduction of the image upon the underlying sensitized surface of the cylinder 20, and to this end a traveling carriage 92 is mounted on oppositely disposed

rails

93 and 94 which are supported above the

frame members

29 and 30 by posts 95. The carriage 92 comprises a plate 96 having upturned flanges 91 that are provided with rollers 96 which rest on the

rails

93 and 94, and to limit the travel of the carriage 92 to the right to which position it is moved between reproducing operations a stop member 93 is connected across the lower faces of the

rails

98 and 94. A pair of lamp supporting members I 00 and MI that are secured at their upper ends by brackets I02 to the lower face of the outer edge of the plate 98 extend downwardly and outwardly. The downwardly extending portions of thelamp supporting members are connected by plates I03 and the outwardly extending portions are provided with a plate I04 having a hub portion I05 in which the lower end of a shaft I06 is fixed by a set screw IN. The upper end of the shaft I06 is provided with a plate I01 upon which an arc lamp assembly I08 is mounted. In like manner, a pair of similar lamp supporting members I09 that are secured by similar brackets III to the lower face of the inner edge of the plate 96 extend downwardly and outwardly. The downwardly extending portions of these lamp supporting members are also connected by plates H2 and the outwardly extending portions are provided with a plate I I3 having a hub portion H4 in which the lower end of a shaft H5 is likewise fixed by a set screw H6. The upper end of the shaft 5 is also provided with a plate IIl upon which a similar arc lamp assembly H0 is mounted.

The are lamp assemblies I08 and H8 are of standard construction and a detailed description thereof is not deemed necessary. It is to be noted, however, that they are capable of adjustment and that each lamp is provided, as usual, with a reflector II9. Each reflector opens into a light tunnel I20 that is fixedly mounted by brackets I2I to the arms I22 upon which the reflectors II9 are secured. A vertically movable light hood I23 is positioned between the light tunnels I20 and it is adapted and arranged to fit over the cylinder 20 beyond the ends of the image area 2I when it is in its down position. The ends of the light hood I23 are open and they are so shaped that the hood forms a continuation of the light tunnels I20 so as to direct the rays of light emitted by the lamps I08 and H8 against the image area 2| of the film 22. To raise and lower the light hood I 23 the upper face thereof is provided with a clamp I24 to which one end of a rop I25 is secured. The rope I25 is trained over a pulley I26 secured to the lower face of the plate 96 and its other end is provided with a handle I21, and to guide the hood I23 in a fixed path as it is raised and lowered it is provided with a bracket I28 having a vertical groove I29 in which is positioned a gib I30 secured to the downwardly extending portion of the left front lamp supporting member I00. The light hood I23 is maintained in its normal raised position by means of a latch I3I which is pivotally mounted on the downwardly extending portion of the left front lamp supporting member I00 and which is adapted and arranged to engage a shoulder I32 formed on the lower face of the bracket I28, and to arrest the downward movement of the light hood I23 at a desired position a pin I33 is secured to the gib I30 in the path of the shoulder I32.

In operation the movable carriage 92 is positioned to the right while the image area 2| is being brought into intimate contact with the underlying portion of the sensitized surface of the cylinder 20 and while the remaining portion of the sensitized surface of the cylinder is being protected against the action of light. Thereafter the carriage 92 is moved to the left to carry the light hood I23 and the lamps I08 and H8 over the image area 2| of the film 22 after which the hood is lowered and the lights adjusted and rendered active. The light thus directed against the image area 2! of the film 22 creates a reproduction of the image onto the sensitized surface of the cylinder 20.

After the image has been thus reproduced upon the sensitized surface of the cylinder 20, the lights are rendered inactive, the hood I23 is raised and the carriage 92 is moved to the right. The tension on the strap 51 is then released and as it is released the springs 55 operate to move the block 3'! upwardly to its normal raised position to break the intimate contact between the film 23 and the sensitized surface of the cylinder 20.

The position of the film 22 is then changed longitudinally with respect to the cylinder by moving the carriage 41 to the left until the right hand end of the image on the film lies in exact register with the left hand end of the reproduction on the cylinder as shown more clearly in 20 Fig. 9. The cycle of operations is repeated to create a second reproduction of the image onto the sensitized surface, after which the position of the film 22 is again changed longitudinally with respect to the cylinder 20 by moving the carriage 41 to the left until the right hand end of the image on the film lies in exact register with the left hand end of the second reproduction on the cylinder as shown more clearly in Fig. 10. Again the cycle of operations is repeated to create a third reproduction of the image onto the sensitized surface. And since in the present embodiment of the invention the width of the image area is equal to a quarter the length of the printing surface of the cylinder the position of the film is once more changed longitudinally with respect to the cylinder by moving the carriage 41 to the left until the right hand edge of the image lies in exact register with the left hand edge of the third reproduction. Again the cycle of operations are repeated to create a fourth reproduction of the image onto the sensitized surface of the cylinder.

To aid inthus moving the carriage 41 t0 the left to bring the right hand edge of the image into exact register with the left hand edge of the reproduction the front frame member 29 is provided with a beveled carriage positioning rail I upon which a plurality of stop members I36 are slidably 4 mounted and the carriage 41 is provided with an overhanging bracket I31 through which is threaded a positioning screw I38 having a pointed lower end. The lower faces of the stop members I35 are provided with set screws I39 which when brought into engagement with the lower face of the positioning rail I35 locks the stop members to the rail. and the upper faces of the stop members I36 are provided with recesses I which exactly conform with the size and shape of the pointed lower end of the positioning screw I38. When the image area 2I on the film 22 has been positioned adjacent the right hand end of the cylinder 20 and brought into intimate contact with the underlying sensitized surface of the cylinder during the first reproducing operation a number of the stop members I36 (in the present case four) which correspond with the number of times the position of the image area is to be changed longitudinally with respect to the cylinder are moved along the guide rail I35 from their usual place of storage at the right until they are positioned in front of the cylinder. The last or terminal stop of the group thus moved is positioned beneath the pointed lower end of the positioning screw I38 after which the screw is threaded downwardly to force the pointed lower end into the recess I40 in the top face of the stop, and as the pointed lower end of the screw I38 enters the recess I40 it operates to move the stop to its final position after which it is locked to the rail I35. The remaining stops in the group are then spaced until the distance between the centers of the recesses I40 is exactly equal to the width of the image area of the film. In consequence when changing the position of the image area longitudinally with respect to the cylinder prior to the second, third, and fourth'reproduction operation it is only necessary to successively locate the pointed lower end of the adjusting screw I38 in the recess I40 in the top surface of the successive stops I36 to bring the right hand edge of the image on the film into exact register with the left hand edge of the re production on the cylinder.

After the reproductions are thus created throughout the length of the cylinder the carriage 41 is moved back to the position it occupied during the first reproducing operation and the position of the image area 2I is changed circumferentially with respect to the cylinder to bring the image area above an unexposed aliquot portion of the cylinder sensitized surface. To aid in this operation one end of the mandrel 23 upon which the cylinder 20 is mounted is provided with an indexing device. As shown more clearly in Figs. 3 and 4, the indexing device I 4| comprises a disc I42 which is secured to one end of the mandrel 23 by a set screw I43. The disc I42 is provided with a. plurality of holes I44 and normally it and the mandrel 23 are locked in fixed position by means of a pin I45 which extends through one of the holes and into an aligned hole I46 in the left hand bearing 25. In the present embodiment of the invention the holes I44 in the disc I42 are divided into two sets: flute set being identified by the numerals 2.4 and comprising four holes spaced 90 degrees apart. The other set is identified by the numerals 3.6 and comprises six holes spaced 60 degrees apart. The set of four holes is provided to take care of cases where the length of the image area M is made equal to a quarter or a half the circumference of the cylinder 20 and it is necessary to rotate the cylinder either a quarter or a half revolution to bring one end of the image area 2| into exact register with an opposite end of a reproduction, and the set of six holes is pro vided to take care of cases where the length of the image area on the film is made equal to a sixth, a third, or a half, the circumference of the cylinder and it is necessary to rotate the cylinder a sixth, a third, or a half, a revolution to carry one end of the image area into exact registration with the opposite end of a reproduction.

In the present case where the length of the image area throughout its width is made equal to half the circumference of the cylinder, the mandrel 23 is initially locked in fixed position by inserting the pin I45 through one of the holes I44 in the disc I42 and into the aligned hole I45 in the left hand bearing 25. The mandrel 23 is maintained locked in this fixed position until after the reproductions are created along the length of the cylinder 20. Then when the position of the image area 2I is changed circumferentially with respect to the cylinder 20 the pin I45 is removed and the disc I 42 is turned to rotate the mandrel 23 beneath the film 22 and the overlying blanket 34. In the event the pin I45 was initially inserted through one of the holes marked 2.4 the disc I42 is rotated until the second one thereafter so marked is brought into alignment with the hole I46 in the bearing 25 or in the event the pin was initially inserted through one of the holes marked 3.6 the plate is rotated until the third one thereafter so marked is brought into alignment with the hole I46 in the bearing 26. In either case the mandrel 26 is rotated through 180 degrees and the ends of the image on the film lie in register with the ends of the reproduction on the cylinder. After theposition of the image area has been so changed with respect to the cylinder the cycle of operations are continued four more times to create four more reproductions along the cylinder. In this manner the surface of the cylinder 20 from which it is desired to print is covered with eight reproductions which merge to form a continuous design.

After the continuous design has been thus reproduced upon the sensitized surface of the cylinder the mandrel 23 carrying the cylinder 20 is removed from the

bearings

25 and 26. The sensitive coating on the surface of the cylinder is developed in a manner well understood in the art to form an acid resist after which the cylinder is rotated in a corrosive bath I49 to etch out the affected areas I50 as is shown more clearly in Fig. 13. Then the cylinder is cleaned in any suitable manner. to remove the unaffected portions |l as shown in Fig. 14, after which it is ready for printing purposes.

In the present embodiment of the invention the ends of the film 22 are shown and described as being connected between the bar 36 and the vertically movable block 31 to enable the image area 2| to be drawn downwardly without distortion into intimate contact with the underlying surface of the cylinder 20. It is to be noted, however, that this arrangement is satisfactory because in the present embodiment of the invention the width of the image area is an aliquot part of the length of the cylinder in which case the entire image area is brought into intimate contact with the underlying surface of the cylinder. In the event, however, that the width of the image area is an aliquant part of the length of the cylinder a portion of the image area necessarily extends beyond one end of the cylinder while reproductions of the image on the remaining portion are being created on this end of the cylinder to complete the endless design. In consequence, if such an arrangement is employed when the width of the image area is an aliquant part of the length of the cylinder that portion of the film which extends beyond the end of the cylinder is quite likely to be drawn downwardly beyond the end of the cylinder while the remaining portion would be arrested as it was brought into intimate contact with the cylinder and so cause distortion of the image area. Then if the distorted image area was thereafter positioned over an unexposed portion of the cylinders sensitized surface and subjected to a pull it would not be brought into intimate contact with the cylinder and in consequence the light after it passed through the film would diffuse and so cause an unsatisfactory reproduction. To avoid this possibility of distortion when the width of the image area is an aliquant part of the length of the cylinder a transparent blanket is positioned over the film and the ends of the blanket, rather than the ends of the film, are clamped between the bar 36 and the vertically movable block 31. When a blanket is employed it is secured to the film so that the two move as a unit, this being accomplished by making the blanket slightly narrower than the film and by pasting the two together by adhesive strips which must be positioned outside the image area of the film.

Also, it is to be understood that while the image area is moved successively from one end of the cylinder to the other in the present embodiment of the invention, other arrangements may be employed to expose to light the entire printing the printing surface of the cylinder, bringing thev image bearing portion of the film into contact with a light unaffected area of said sensitized surface, subjecting the image bearing portion of the film to the action of light to create a reproduction of the image upon said sensitized surface, repeatedly changing the position of the film longitudinally and circumferentially with respect to the position of the cylinder to bring the image bearing portion of the film over other light unaffected areas of said sensitized surface, bringing said image bearing portion of the film into contact with the underlying light unaffected area each time the position of the film is so changed, and subjecting said image bearing portion of the film to the action of light each time it is brought into contact with the sensitized surface of the cylinder to create other reproductions of said image on said sensitized surface, the distances that the position of the film is so changed with respect to the position of the cylinder being such that the reproductions of the image on the sensitized surface of the cylinder interfit to form a continuous design.

2. In the method of photo-mechanically engraving the printing surface of a cylinder, the steps which comprise rendering said surface sensitive to the action of light, creating upon a flexible film an image of a design element having an irregular border, the overall width of said image being less than the length of the printing surface of the cylinder and the length of the image throughout its width being equal to one-half the circumference of the cylinder, bringing the image bearing portion of the film into intimate contact with a light unaffected area of said sen sitized surface, subjecting the image bearing portion of the film to the action of light to create a reproduction of the image upon said sensitized surface, repeatedly changing the position of the film longitudinally and circumferentially with respect to the position of the cylinder to bring the image bearing portion of the film above other light unafiected areas of said sensitized surface, and subjecting the image bearing portion of the film to the action of light each time it is brought into contact with said surface to create upon said surface a reproduction of the image, the distance that the position of the film is so changed with respect to the position of the cylinder being such that the reproductions of the image on the sensitized surface interfit to form a continuous design.

3. In combination, a light sensitive cylinder, a film having an irregularly shaped design element whose overall length is such that two design elements interfitted along their widths equal the circumference of the cylinder and whose overall width is less than the length of the printing surface of the cylinder, means for positioning that portion of the film carrying the design element above a light unaflected area of said cylinder, means for repeatedly changing the relative positions of the film and cylinder longitudinally and circumferentially to bring that portion of the film carrying the design element above other light unaflected areas of said cylinder, means for bringing that portion of the film carrying the design element into intimate contact with said cylinder each time it is positioned above a light unaffected portion of the film carrying the design element above a light unafl'ected area of said cylinder, means for repeatedly changing the relative posi tions of the film and cylinder longitudinally and circumferentially to bring that portion of the film carrying the design element above other light unaflected areas of saidcylinder, means for bringing that portion of the film carrying the design element into intimate contact with said cylinder each time it is positioned above alight unaflectedarea, means for subjecting said cylinder to the action of light through that portion of the film carrying the design element each time said portion is brought into contact therewith to create a reproduction of the design element on said sensitized surface, means for shielding the remaining portion of said cylinder against the action of light, and means for so limiting the distances that the relative positions of the film and cylinder are changed that the reproductions of the design elements on the sensitized 20 surface interfit to form a continuous design.

ownn a. HUGGINS.