US3252416A

US3252416A - Method and apparatus for removing foreign matter from a planographic printing press plate cylinder

Info

Publication number: US3252416A
Application number: US363150A
Authority: US
Inventors: James O Allen
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-04-28
Filing date: 1964-04-28
Publication date: 1966-05-24
Anticipated expiration: 1983-05-24

Description

6 1 1 MW 4 e 2 m 5 M 2 S 3 e y 1966 J. o. ALLEN METHOD AND APPARATUS FOR REMOVING A PLANOGRAPHIC PRINTING PRESS PLATE CYLINDER Filed April 28, 1964 May 24, 1966 J. o. ALLEN 3,252,416

METHOD AND APPARATUS FOR REMOVING FOREIGN MATTER FROM A PLANOGRAPHIC PRINTING PRESS PLATE CYLINDER Filed April 28, 1964 4 Sheets-Sheet 2 May 24, 1966 J. o. ALLEN 3,252,416

METHOD AND APPARATUS FOR REMOVI 'OREIGN TTER FROM OGRAPHIC PRINTING PR PLATE I R A PLAN Filed April 28, 1964 4 sets-Sheet 5 izverzii Med 0. QZZZW @M/ afu CZWW May 24, 1966 J. o. ALLEN METHOD AND APPARATUS R REMOVING FOREIGN MATTER FROM A PLANOGRAPHIC NTING PRESS PLATE CYLINDER Filed April 28, 1964 4 Sheets-Sheet 4 Ma 9 aw 252 @M W wiw fig United States Patent 3,252,416 METHOD AND APPARATUS FOR REMOVING FOREIGN MATTER FROM A PLANOGRAPH- TC PRINTING PRESS PLATE CYLINDER James 0. Allen, 1600 7th Ave., Peoria, Ill. Filed Apr. 28, 1964, Ser. No. 363,150 8 Claims. (Cl. 101-425) This invention relates to printing presses and, more particularly, to the method and apparatus for removing undesirable foreign matter from the plate segment of the plate cylinder of an offset printing press.

This application is a continuation-in-part of my 00- pending application Serial No. 279,207, now abandoned, filed May 9, 1963. Y

The image portion of a printing plate for an offset press is covered with a grease, or like substance, to which the printing ink will adhere and the surrounding portion or non-printing area is kept damp by the application of water, which repels ink. To complete the printing operation, the image is transferred from the-plate to a rubber covered cylinder known as a blanket cylinder, from which it is printed on paper, or other material to be printed.

If a completely faithful reproduction of the image area is desired, i.e., free of defects, it is essential that the image area be maintained free of foreign matter. To prevent foreign matter from finding its way to the plate cylinder is an impossible task due to the environment in which the printing press is located and the nature of the materials being printed. Two of the various components of the press that tend to deposit foreign matter on the plate cylinder are the rollers and dampeners. In the case of the materials being printed, such as paper or board, there are various particles of fiber, felt hairs and slitter dust that often find their way to the plate cylinder.

If the foreign particles, which are known in the trade as hickeys, are not removed from the image area of the plate cylinder, the image transferred to the blanket cylinder and subsequentially to the paper, -or other surface being printed, will contain defects that will be re peated on every printed page. These defects may take a number of forms, including (1) an unprinted area con forming to the outline of the foreign matter, (2) an irregular shape surrounded by a halo or (3) a weak area, all of which detract from and mar the appearance of the printed material.

The aforementioned defects result from the hickeys on the greased image surfaces absorbing water ad thus repelling ink, which leaves a blank space or transfers a reduced quantity of ink to the blanket cylinder, or by depressing the blanket cylinder, which brings about the halo effect above referred to due to the foreign matter moving the surrounding portion of the blanket cylinder away from the plate image area, thus preventing the transfer of ink thereto.

It is an understatement to say that the hickey problem is a serious one. In recent years, with the arrival on the scene of large, very expensive presses, and the tremendous -increase in labor costs, the hickey problem has become particularly critical. To shut down the presses to remove the hickeys is a very costly proposition, but an unacceptable print job is even more costly, so that a great deal of time and effort has gone into devising means to eliminate hickeys.

Various methods that have been tried to solve this problem include a constant relentless campaign to prevent the existence of foreign matter in the air and elongated rollers for eliminating the hickeys from the printing plate. Due to the very nature of the printing press and the environment in which it is located, it is impossible to prevent the existence of particles in the air that may eventually settle on the plate cylinder.

ice

The efforts to remove the particles from the printing plate have heretofore been at best only partially successful. Devices in use today include leather rollers that extend the full length of the plate cylinder and are mounted inside out, so that the nap, or grain, contacts the plate and is supposed to lift the hickeys from the plate. These rollers soon fill up with hickeys and they must be constantly replaced, or they will shortly begin to lose whatever effectiveness they have. Furthermore, leather rollers are relatively expensive, and the need to constantly replace them requires that the press be periodically shut down, which addes to the overall cost incurred for hickey removal.

Another way of removing hickeys which has been practiced since time immemorial is the thumb method, which consists of the machine operator attempting to flick the hickey off the plate while it is rotating at a high speed. Needless to say, this is a very dangerous and completely impractical method that has resulted in the loss of numerous thumbs.

Thus, it can be appreciated that the printing industry is in sore need of a device which will remove hickeys from the image area of a printing plate, which device will be highly efiicient in operation, relatively low in cost, and eliminate the need to periodically shut the press down to replace costly, relatively inefficient devices currently being used for these purposes.

In accordance with the present invention, there is provided a method and apparatus for effectively and automatically removing hickeys from the plate segment of a plate cylinder to prevent defects from occurring on the printed surface.

The novel method disclosed herein consists of locating a cleaning attachment adjacent to the outer surface of the plate cylinder, which attachment includes a wiping member that is spaced from the metallic surface of the plate segment, but is positioned to contact the outer surface of the grease and water film on the plate segment of the plate cylinder. Once the wiper member is so positioned, it is moved transversely back and forth across the surface of the grease and water film and functions to remove any foreign matter, or hickeys, from the greased surface and transfer them into the 'water portion of the plate, where they will not mar the printed surface. The image surface will thus be completely inked and a completely satisfatcory printed surface will be obtained. The cleaning attachment so provided is positioned to contact the image on the plate cylinder before it is rotated into engagement with the watering and inking rolls. This location of the attachment insures removal of the hickeys, but prevents smearing of the ink surface about to be transferred to the blanket cylinder. The tacky ink rollers subsequently pick up and remove the foreign material from the water areas of the plate segment and deposit them in the ink fountain, or some other suitable place away from the plate segment.

Furthermore, the practicing of this method brings about an even distribution of the water located in the damp portion of the plate cylinder and acts to wipe away the water tending to adhere to the greased surfaces, which could weaken, or reduce the intensity of the printed image.

The apparatus embodying the present invention takes the form of an attachment that is positioned to contact the outer surface of the film of grease and water disposed on the outer surface of the plate segment during the printing operation. The wiper unit is adjustabl'y positioned to contact the aforementioned film at a tangent thereto after which it is retained in said position. The spacing between the outer surface of the metallic portion of the cylinder and the wiper unit is on the order of a couple of thousandths of an inch, which gap is generally set by inserting a thin sheet of paper between the plate cylinder and the wiper pad prior to starting the press. The wiper unit has a width that is a fraction of that of the plate cylinder, and during its cleaning operation it is automatically moved back and forth across the width of the plate segment when the press is running. During this transverse movement, the wiper unit contacts the foreign matter located on the greased areas and transfers it into the surrounding water area. This prevents the printing image from receiving other than the prescribed quantity and distribution of ink, and thus insures that the image being transferred to the blanket cylinder and subsequently to the printed page is as desired. The foreign matter in the water area is picked up by the tacky ink rollers and deposited in the ink fountain.

In the illustrated embodiment, a single wiper unit located on a double screw is used to move the wiper unit back and forth. This device brings about a continuous back and forth movement of the wiper unit across the surface of the plate segment. It has been found that the complete surface of the image portion of the plate cylinder will be cleaned of hickeys within about two or three revolutions of the plate cylinder. However, several wiper units may be located along the width of the plate cylinder, if such is desired.

The method and apparatus referred to above are adaptable to both two-cylinder and three-cylinder offset printing presses, both of which are illustrated in the attached drawings. In the case of a two-cylinder or three-cylinder press of the Davidson variety, the wiper unit is mounted so that it will contact the plate segment portion of the plate cylinder, but will be moved out of engagement with the remaining portion of the plate cylinder during the balance of the 360 rotation of the plate cylinder by a suitably arranged cam and link system. This avoids possible smearing of the balance of the cylinder and also the possibility of the hickey finding its way back to the plate segment. With a conventional three-cylinder offset press, there is no need to move the wiper unit away, since there is a gap between the ends of the plate segment.

It is to be noted that in each instance the wiper unit contacts the plate segment prior to the time it is brought into engagement with the water and inking units. Such an arrangement is preferred to avoid smearing the ink after it has once been applied to the plate segment.

An additional advantage of this invention is that it has been found that it improves the water distribution on the plate segment and prevents the graying out of the ink surface by tending to eliminate any build-up of water on a in which:

FIGURE 1 is a side elevation of a two-cylinder or Davidson typeoffset press having an attachment constructed according to this invention applied thereto, with parts being broken away for clarity;

FIGURE 2 is a fragmentary perspective end view of FIGURE 1, taken from the left-hand end of FIGURE 1;

FIGURE 3 is an enlarged section taken along line 3-3 of FIGURE 2;

FIGURE 4 is an enlarged fragmentary plan view of FIGURE 3, the fragment being rotated 90 in a clockwise direction with respect to its FIGURE 3 position;

FIGURE 5 is a section taken on line 5-5 of FIG- URE 4;

FIGURE 6 is a fragmentary view looking from line 66 of FIGURE 1;

FIGURES 7 and 8 are diagrammatic views illustrating the operation of the attachment on a two-cylinder offset printing press;

FIGURE 9 is a diagrammatic view similar to FIGURE 8 illustrating the operation of the attachment on a threecylinder Davidson type offset press;

FIGURE 10 is a schematic view of a conventional three-cylinder offset printing press embodying the invention wherein there is no provision made for moving the wiper pad away from the plate cylinder; and

FIGURE 11 is a sectional view illustrating the relationship between the wiper pad and the grease and water films located on the surface of the plate segment.

Referring now to the drawings, it will be noted that corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

In FIGURES 1 through 8, there is illustrated a twocylinder Davidson press 1. This press is well known in the printing field, and a detailed discussion is not required. However, it is to be noted that a characteristic of this type of press is that it is convertible from an offset press to a letter press. In this regard, the cylinder surface extends a full 360. The press includes a frame generally designated 3 having side walls 5 and 7. The upper cylinder of the press is generally indicated at 9 and mounted thereon is a plate segment 11 and an impression segment 13 (see FIGURES 7 and 8). The blanket cylinder is indicated at 15.

The drive system for the press which forms no part of the present invention includes a motor 17 that drives a shaft 19 extending between walls 5 and 7. A gear 21 on shaft 19 drives a gear 23 connected to the blanket cylinder 15, which gear 23 is also in mesh with a gear 24 connected to the upper cylinder 9.

The press 1 also includes a conventional water unit 25 and ink unit 27. Each of these units includes a plurality of rollers 25, 27', respectively, that are generally coextensive with the width of the plate segment of the plate cylinder. A blanket cylinder release mechanism is generally indicated at 29 and includes a cam 31 (shown in dotted lines in FIGURE 1) mounted on the shaft of the upper cylinder 9. As will be understood, the cam 31 is adapted through a link 33 to throw the blanket cylinder 15 out of contact with the upper cylinder 9 when a sheet of paper, for example, is not fed into the nip of the upper cylinder 9 and blanket cylinder 15. A tripping mechanism generally designated 35 is provided for detecting whether or not a sheet is fed into the press. All of the above-mentioned elements of the press are conventional.

A wiper attachment constructed according to this invention is generally indicated at 37. The attachment can take several forms, and, as illustrated in FIGURE 3, one such form includes a plate 38 lying on a bar 39 extending between side walls 5 and 7. The plate has a generally L-shaped arm 41 extending around the wall 7. Pins 43 extend up from bar 39 through slots 45 in plate 38 which permit movement of the plate toward and away from the upper cylinder 9 while preventing lateral movement of the plate.

Bearings

47 and 49 attached to plate 38 rotatably support a double screw shaft 51 having a rightand left-hand screw groove therein. A block or carrier 53 is mounted on shaft 51, which block is provided with a lateral hole 55 in which a follower pin 57 is located. The follower 57 is rotatable in hole 55 and thus it is free to shift from the left-hand groove to the right-hand groove and vice versa upon reaching the opposite ends of the shaft 51. The follower is maintained in engagement with the grooves in shaft 51 by a plate 59 secured to the block 53 as by screws 61. A post 63 extends up from the top of the block 53 and has a hole 65 in which a rod 67 is slidably received. The rod serves as a pivot support for the block 57 and the ends thereof are secured in posts 69 and 71 extending up from

bearings

47 and 49.

As illustrated in the embodiment found in FIGURE 5, a piece 73 of rubber fabric, or other material adapted to pick up foreign matter from the image area of the plate segment of upper cylinder 9, is adhered to the top of block 53 and extends beyond the inside edge thereof. The piece 73 may have adhesive on one side for securing it to the block, or it may be removably taped to the block.

It will be understood that rotation of shaft 51 causes the block 53 to traverse back and forth along the shaft between

bearings

47 and 49, and rod 67 prevents tilting of the block.

The plate 38 on which the wiper unit is disposed is spring mounted relative to the frame 3 by means of tension springs 89 extending between the inner edge of plate 38 and adjacent portions of the frame 3. The location of the wiper pad 73 relative to the image area of the plate that is to be cleaned of hickeys is quite critical in that it must be close enough to remove hickeys from the greased image area yet should not contact the metal surface of the plate segment, since to do so would result in substantial wearing of the wiper piece 73. In essence, the wiper unit should bepositioned to engage the grease and water film on the plate segment, but not the plate segment itself. One way to set this gap is to slide a piece of paper between the cylinder and wiper unit prior to starting up the press and lock the unit in that position.

The means for adjusting the position of the wiper pad shown in the drawings consists of adjusting screws 91 that extend through holes 93 in flanges 95 of side Walls and 7. Screws 91 are threaded into posts 97 secured to the plate 38. The holes 93 are larger than the diameter of the screws 91 for a purpose to become apparent hereinafter. Screws 91 have enlarged heads 99 located on the outside of flanges 95. It will be seen that plate 38, and accordingly wiper piece 73, may be moved toward and away from the upper cylinder 9 by rotation of the screws 91 in one direction or the other.

The above is but one example of a wiper unit that could be employed for removing the hickeys from the surface of the image area of the plate segment of the plate cylinder. As will be set forth hereinafter, another arrangement can be employed which consists of a rectangular pad which is tangentially disposed relative to the film of grease and water disposed on the plate segment. The details of this embodiment will be discussed-hereinafter.

In the press shown in FIGURE 1, the wiper attachment is driven off of the motor used for driving both cylinders of the two-cylinder press 1. The wiper unit could, if desired, be driven by an independent motor means provided for that purpose.

The drive means illustrated in the drawing includes a pulley 75 that is secured to one end of shaft 51. Spaced below shaft 51 is a shaft 77 rotatably mounted in the side walls. 5 and 7. A pulley 79 is secured to shaft 77 inside wall 7 and in the same vertical plane as pulley 75. A belt 81 is trained around pulleys 75 and 79. A plurality of pulleys 83 aremounted on shaft 77 outside wall '7, which have varying diameters and maybe individual pulleys, or they may be formed as an integral unit. A pulley 85 is mounted on shaft 19 outside of wall '7 and may be adjusted to be in the same vertical plane as any one of the pulleys 83. A belt 87 is trained around one of the pulleys 83 and pulley 85. It will thus be seen that shaft 19 drives shaft 77 through belt 87, and shaft 77 in turn drives shaft 51 through belt 81.

In the two-cylinder and three-cylinder Davidson presses shown in FIGURES 1 through 9, it is essential that the wiper pad be moved out of contact with the cylinder after the plate segment of the plate cylinder has passed the wiper unit. If the wiper unit is not so displaced, it may tend to contact the smear that portion of the plate cylinder and mar the paper being printed, or it may find its way back to the plate segment. To accomplish this end, there is provided a cam and link system which functions to pivot the wiper unit clockwise about shaft 67 (see FIGURES 79) to increase the spacing between the pad 73 and the outer surface of cylinders 9 and 9a.

The system shown in FIGURES 7 and 8 includes an arm 101 that is secured to and extends upward from the arm 41 of plate 38. A follower roller 103 connected to the outer end of arm 101 rides on a cam 105 secured to the shaft of the upper cylinder 9 adjacentthe blanket cylinder release cam 31. The follower 103 is maintained in engagement with cam by a tension spring 107 extending between arm 101 and side wall 7.

The cam 105 is generally circular, but has a raised portion 109 throughout a portion of its periphery. The angle formed by lines drawn from the ends of the raised portion 109 to the shaft of the upper cylinder 9 is substantially equal to the angle formed by lines drawn from the ends of the plate segment 11 to the center of the shaft of the upper cylinder. When the follower 103 is riding on the unraised portion of cam 105, plate 38 rests in a generally horizontal position on bar 39 and the rubber piece 73 is substantially spaced from the upper cylinder 9 (see FIGURE 5). The location of the raised portion 109 is such that when the follower 103 rides up on the raised portion of cam 105, plate 38, and accordingly block 53, are pivoted very slightly in a counter-clockwise direction as viewed in FIGURES 1 and 5, bringing the inner edge of the piece '73 into contact with the outer surface of the ink and water film disposed on the plate segment 11 of the cylinder 9. As previously mentioned, the wiper unit is spaced from the metallic portion of the cylinder a gap which is on the order of a couple of thousandths of an inch, which is the approximate thickness of the grease and water film on the plate segment. With this arrangement, any -foreign matter located on the greased image portion of the plate segment will be picked up and moved into the adjacent water, or non-image, area' of the plate segment. A schematic showing of the grease and water film located on the outer surface of the plate cylinder is best seen by referring to FIGURE 11. It remains to note that the hickeys moved into the water portions of the plate segment are picked up by the tacky ink rollers and are subsequently deposited in the ink fountain.

When the follower 103 rides ofi the raised portion 109 (FIGURE 7), block 53 is pivoted away from the upper cylinder 9 just as the trailing end of the plate segment travels past the wiper unit, and the wiper unit is prevented from contacting the balance of the cylinder.

Briefly, the method of operation of a two-cylinder press, as shown in FIGURES 7 and 8, is as follows:

When the press is started, the follower 103, as shown in FIGURE 7, rides on the lower portion of the cam 105. Accordingly, plate 38 is maintained in a relatively horizontal position on bar 39 and the inner edge of the piece 73 is spaced a significant distance from the outer surface of the cylinder 9. As the leading edge portion of the plate segment 11 reaches piece 73, follower 103 rides upon the raised portion of cam 105 and pivots the plate 38 counterclockwise on bar 39. This brings the inner edge of piece 73 into contact with the grease and water film of the plate segment 11. As the plate segment 11 passes the piece 73, the block 53 moves transversely across the plate segment. It will be understood that the distance traveled by the block 53 during one pass of the plate segment 11 will be dependent upon the size of

pulleys

85, 83, 79 and 75. The block may thus make one or more complete traversals across the surface of segment 11 as the latter passes the attachment. Any lint or other foreign particles on the greased areas of the plate segment 11 which are in the path of piece 73 will be removed from segment 11 and deposited in the water area. While the piece 73 may have a zig-zag path dur-,

ing one traversal of the printing plate segment 11 past the piece 73, it will be understood that piece 73 will cover the complete surface of the plate segment 11 after a few revolutions of the upper cylinder 9. Thus, any lint, or other foreign matter on the greased areas of the plate segment 11, will be removed within a few revolutions of the cylinder 9 and deposited in the water areas of the plate segment from where it is picked up by the tacky ink rollers and removed from the plate segment.

The attachment is shown in diagrammatic form in FIGURE 9 as applied to a three-cylinder, Davidson type offset press. As will be understood, a three-cylinder offset press conventionally includes a cylinder 9a carrying a plate segment 11a, a blanket cylinder 15a, an impression cylinder 111, a Water unit a, and an inking unit 27a. It will be understood, in accordance with this invention, that a cam a is substituted for cam 105 in a three-cylinder offset press. The raised portion 109a of cam 105a constitutes a substantially longer are than the raised portion 109 of the cam 105, but lines drawn from its ends to the center of the shaft of the upper cylinder 9 form an angle substantially equal to the angle formed by lines drawn from the ends of the plate segment 11a to the center of the shaft. The attachment is operated in the same manner for a three-cylinder offset press as it is for a two-cylinder offset press.

Turning now to the embodiment shown in FIGURES 10 and 11, there is diagrammatically illustrated a threecylinder conventional type offset printing press. In these presses, there is a gap existing between the ends of the plate segment on the plate cylinder and thus there is no need to provide a cam and follower system of the type shown in FIGURES 1 through 9 to move the wiper unit away from the plate cylinder after the plate segment has passed.

The three-cylinder system shown in FIGURE 10 consists of plate cylinder 120, blanket cylinder 121 and impression cylinder 122. The plate cylinder has mounted thereon a plate segment 123 which contains the image to be printed. The plate segment 123 is secured to the plate cylinder 120 by a suitable fastening means.

Disposed about the plate segment and adapted to be contacted thereby are conventional ink and water units 124, 127, respectively. The ink unit includes a plurality of rollers 125 that receive ink from a fountain 126 and provide it to the image area of the plate segment 123. As is clearly understood by one skilled in the art, ink will be deposited on the greased areas of the image area and will be repelled by the water located on the non-image areas of the plate segment. The water unit 127 includes a plurality of rollers 128 that receive water from the reservoir 129 to wet the non-image areas of the plate segment which is made of a composition to absorb water. It remains to note that the blanket cylinder 121 includes a blanket member 130 disposed thereover and secured thereto by suitable fastening means.

As previously stated, the wiper unit functions to remove the hickeys, or foreign matter, from the greased image areas of the plate segment and acts to deposit them into the non-image areas. The wiper unit moves transversely across the width of the plate segment during the rotation of the plate cylinder. When the hickeys are moved into the non-image areas, the tacky ink rollers 125 pick up the hickeys and deposit them in the ink fountain 126.

Referring now to FIGURE 11, there is illustrated in cross-sectional view a portion of the plate segment of the plate cylinder, and associated Wiper unit 140. The wiper unit 140 is moved transversely across the plate segment by a double-screw arrangement 134 which is suitably mounted in bearings 137 secured in supports 136. The supports 136 are mounted to a properly located frame member 135. The double screw is rotated by drive means through any desired driving mechanism.

The wiper unit 140 is similar in construction to that disclosed in FIGURES 3 through 9 and includes a wiper pad 142 that is suitably secured to the main member 141 of the Wiper unit. Extending downwardly from the member 141 and into contact with the double screw 134 is a guide member 143. The wiper unit is guided during its transverse movement by a rod 144 that extends into supports 136 and through an opening in wiper unit 141.

The film of grease and water on the outer surface of .the segment 123, indicated by the numerals 133 and 132,

respectively, is greatly exaggerated in FIGURE 11 to show the relationship between the wiper pad and the film of water and grease located on the exterior surface of the plate segment. The wiper pad is positioned to contact the outer surface of this film, which is on the order of a couple of thousandths of an inch thick. As previously indicated, the wiper unit will probably cover the entire surface of the subject film on the plate segment within about two or three revolutions of the plate cylinder.

It should be noted that the wiper unit is positioned to contact the plate segment along a tangent thereof before it comes into contact with the water and ink units 127, 124, respectively. In this way, the wiper unit is equipped to perform its wiping function and will not contact the image area after it has been inked. Furthermore, it has been found that the wiper unit, in addition to functioning as a means for cleaning the plate segment of hickeys, acts to prevent a reduction in the intensity of the image area by removing any layers of water that tend to adhere to the greases and inked image area.

The operation of the embodiment shown in FIGURES 10 and 11 is as follows:

When the press is started, the rolls are, of course, dampened and the link is supplied to the image area. During a full cycle of the plate cylinder, it first contacts the wiper unit 140 to remove the hickeys from the image area thereof. The transverse back-and-forth movement of the wiper unit resulting from the power driven double screw 134 moves the wiper unit back and forth across the surface of the plate segment to move the hickeys located in the image area into the non-image area. The tacky ink rollers subsequently pick up the hickeys from the nonimage area and deposit them in the ink fountain 126. The hickey-free image is then transferred to the blanket 139 and prints on a sheet of paper directed between the blanket and impression cylinders.

Thus, it can be seen that the invention disclosed herein solves a very acute problem in the printing industry by keeping the image area of the plate segment free of foreign matter so that the printed matter will be free of defects.

Various substitutions and equivalents can be made for various components of the mechanisms set forth above, if such is desired. Also, while .the invention has been directed to several embodiments in which the wiper unit contacts the outer surface of the grease and water film disposed on the plate segment, this is merely exemplary, since it could, if desired, be slightly spaced from said film.

Accordingly, it is intended to cover by the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. In a system of offset printing, a method of preventing embedment of hickeys on a printing plate segment mounted on a rotatable printing plate cylinder to present a surface repeatedly travelling a cylindrical path conjointly with rotation of the cylinder, said surface conventionally having predetermined areas receptive to water interspersed with predetermined areas receptive to ink, said method comprising rotating a Water applying roller in rolling contact with said surface along one region of the cylindrical path to present a water film for selective deposit in accordance with the receptivity of said areas, rotating an ink applying roller in rolling contact with said surface along another region of the cylindrical path to present an ink film for selective deposit in accordance with the receptivity of said areas, locating a wiper edge in close clearance spaced relation to said path in advance of the regions at which the water and ink films are deposited to effect streak free contact with surface regions of the water and ink films sutficient to intercept at least temporarily any filmborn hickey interrupting anyone of such film surface regions encountered by the Wiper edge and, While mantaining such close clearance relation, re-

peatedly transporting the wiper edge in a transversely scanning movement mode that comprises full surfaced sweeping of the wiper edge across the plate segment surface at least once for every several revolutions of said segment thereby shifting any intercepted hickey to other regions of said film surfaces until any hickey escaping from the Wiper edge to a water film region is finally picked up from a water film region by the ink applying roller.

2. A method in accordance with claim 1 and including the steps of retracting the wiper edge from said cylindrical path after the plate segment leaves the wiper edge and returning the wiper edge to close clearance spaced relation to the plate segment surface when the plate segment returns to the wiper edge.

3. In a system of oifset printing, the combination of an oifset press that includes a printing plate segment having a surface provided with predetermined areas receptive to water interspersed with predetermined areas receptive to ink and a cleaning unit for preventing embedment of hickeys on said surface of the plate segment, said press having means for revolving said plate surface about an axis for repeatedly sweeping a cylindrical path, water applying roller means extending transversely to contact said plate surface along one region of the cylindrical path and ink applying roller means extending transversely to contact said plate surface along another region of the cylindrical path, said roller means presenting water and ink films for selective deposit in accordance with the receptivity of said areas, said cleaning unit comprising means providing a support track to span the cylindrical path in uniformly spaced relation along a region thereof in advance of the regions at which the water and ink roller means are located, a wiper movably carried by said support track in a relationship to present a wiper edge leading generally transversely of said path and disposed in close clearance spaced relation to sa-id plate surface to establish streak free contact with surface regions of the water and ink films suificient to intercept a filmborn hickey, and power drive means for shifting said wiper back and forth along said track during rotation of said plate surface to repeatedly sweep the wiper edge completely back and fonth across said path at least once for every several revolutions of the plate surface.

4. In a system of offset printing in accordance with claim 3, and wherein said plate segment spans substantially less than the entire periphery of said cylindrical path and has leading .and trailing edges spaced apant about said periphery and said cleaning unit includes means operable in timed relation to the movement of said plate segment for advancing said wiper towards said path into said close clearance spaced relation to said surface as said leading edge arrives at the cleaning unit and for retracting said wiper from said path as the trailing edge of the plate segment passes said cleaning unit.

5. In a system of offset printing in accordance with claim 4 and wherein the means for advancing and retracting said wiper comprises a cam mounted on the axis of revolution of said plate surface, said cam having a raised portion along its periphery, the angle formed by lines drawn from the ends of said raised portion to said axis being substantially equal to the angle formed by lines drawn from the ends of the plate segment to said axis, an arm connected to said wiper, .a follower connected to said arm and riding on said cam, and a spring biasing said arm and its follower toward said cam, said wiper being pivoted toward said plate segment when said follower rides up on said raised portion and pivoted away from said plate segment when said follower rides down olf said raised portion.

6. In an offset printing system in accordance with claim- 3, wherein said means providing a support track includes a rotatable double-screw shaft, and said wiper includes a carrier mounted on the shaft and having a follower selectively engageable with the double-screw shaft to control the movement of the carrier along the shaft during rotation of the shaft.

7. In an offset printing system in accordance with claim 6, wherein said carrier has a guide hole and said cleaning unit has means mounting a straight rod parallel to said support track and extending through the carrier guide hole to maintain straight line movement of the carrier.

8. In an offset printing system in accordance with claim 3, wherein said wiper edge has a length substantially less than the transverse dimension of the printing plate segment and said power drive means operates continuously and automatically during revolving movement of the printing plate segment.

References Cited by the Examiner UNITED STATES PATENTS 664,965 1/1901 Morriss 101-141 1,138,342 5/1915 Wood 101-169 1,539,202 5/1925 Owen 101-157 2,116,874 5/1938 Barash 101-157 2,142,147 1/1939 Prager 101-157 2,272,461 2/1942 Hamant 101-154 2,644,395 7/1953 Peyrebrune et a1 101-157 2,745,343 5/1956 Davis 101-348 2,832,290 4/1958 Mitchell et a1. 101-425 3,007,404 11/1961 Crawford 101-154 3,144,826 8/1964 Lang et al 101-425 ROBERT E. PULFREY, Primary Examiner.

EUGENE R. CAPOZIO, DAVID KLEIN, Examiners.

REED J. FISHER, Assistant Examiner.

Claims

1. IN A SYSTEM OF OFFSET PRINTING, A METHOD OF PREVENTING EMBEDMENT OF HICKEYS ON A PRINTING PLATE SEGMENT MOUNTED ON A ROTATABLE PRINTING PLATE CYLINDER TO PRESENT A SURFACE REPEATEDLY TRAVELLING A CYLINDRICAL PATH CONJOINTLY WITH ROTATION OF THE CYLINDER, SAID SURFACE CONVENTIONALLY HAVING PREDETERMINED AREAS RECEPTIVE TO WATER INTERSPERSED WITH PREDETERMINED AREAS RECEPTIVE TO WATER METHOD COMPRISING ROTATING A WATER APPLYING ROLLER IN ROLLING CONTACT WITH SAID SURFACE ALONG ONE REGION OF THE CYLINDRICAL PATH TO PRESENT A WATER FILM FOR SELECTIVE DEPOSIT IN ACCORDANCE WITH THE RECEPTIVITY OF SAID AREAS, ROTATING AN INK APPLYING ROLLER IN ROLLING CONTACT WITH SAID SURFACE ALONG ANOTHER REGION OF THE CYLINDRICAL PATH TO PRESENT AN INK FILM FOR SELECTIVE DEPOSIT IN ACCORDANCE WITH THE RECEPTIVITY OF SAID AREAS, LOCATING A WIPER EDGE IN CLOSE CLEARANCE SPACED RELATION TO SAID PATH IN ADVANCE OF THE REGIONS AT WHICH THE WATER AND INK FILMS ARE DEPOSITED TO EFFECT STREAK FREE CONTACT WITH SURFACE REGIONS OF THE WATER AND INK FILMS SUFFICIENT TO INTERCEPT AT LEAST TEMPORARILY ANY FILMBORN HICKEY INTERRUPTING ANYONE OF SUCH FILM SURFACE REGIONS ENCOUNTERED BY THE WIPER EDGE AND, WHILE MAINTAINING SUCH CLOSE CLEARANCE RELATION, REPEATEDLY TRANSPORTAING THE WIPER EDGE IN A TRANSVERSELY SCANNING MOVEMENT MODE THAT COMPRISES FULL SURFACED SWEEPING OF THE WIPER EDGE ACROSS THE PLATE SEGMENT SURFACE AT LEAST ONCE FOR EVERY SEVERAL REVOLUTIONS OF SAID SEGMENT THEREBY SHIFTING ANY INTERCEPTED HICKEY TO OTHER REGIONS OF SAID FILM SURFACES UNTIL ANY HICKEY ESCAPING FROM THE WIPER EDGE TO A WATER FILM REGION IS FINALLY PICKED UP FROM A WATER FILM REGION BY THE INK APPLYING ROLLER.