CA1195181A

CA1195181A - Step and repeat adaptor for a large size platemaker

Info

Publication number: CA1195181A
Application number: CA000402600A
Authority: CA
Inventors: Juergen G. Lein
Original assignee: Itek Corp
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1981-05-18
Filing date: 1982-05-10
Publication date: 1985-10-15
Also published as: GB2099182B; GB2099182A; JPS57195253A; DE3218812A1

Abstract

ABSTRACT OF THE DISCLOSURE

A step and repeat adaptor for a large size platemaker is provided for enabling the simultaneous printing of several impressions of relatively small objects such as documents by a single large photosensitive sheet and as a result, considerable photosensitive material and preparation time is saved. A first vertically oriented flat rectangular light blocking mask overlaying the plate is translatable in a horizontal direction and a second horizontally oriented flat rectangular mask overlaying the plate is translatable in a vertical direction, thereby to provide for the successive imaging of four relatively small objects upon the four quadrants of the large photosensitive plate. One or both of the masks are removable to provide for the "2-up" imaging, or the imaging of a single large object respectively, upon the entire exposure area of the plate.

Description

~1--5~
1 STEP AND REPE~T ADAPTOR FOR A LARGE SIZE PL~TE~IAKER
_. _ PlatemakerS have been marketed for many years by the assignee of the present invention, which employ a horizontally oriented illuminated copyboard upon which various documents and other images are placed. The images are focussed by an optical system upon a verti-cally oriented light sensitive printing plate positioned at the imaging plane. After the imaging, the images are developed and a press-ready plate i5 produced. Certain of these platemakers produce press-ready plates which are quite large, and the plates are capable of producing up to 10,000 impressions~ Should a user of such a large platemaker desire to print relatively small images, a great deal of the plate material is wasted. For example, in the 218 "Itek Platemaster" positive plate-making system, full utilization of the plate material would project an image area upon the plate of about 18 x 25 in. However, if the operator wishes to print a much smaller image, e.g., 9 x 12.6 inches, the result is that about 3/4 of the plate material is wasted. Further-more, assuming that the user wishes to produce up to 40,000 impressions on the printing press 7 he would normally use four large plates to further compound the waste of photosensitive material.
The present invention provides a step and repeat adaptor for a large size platemaker which would enable the operator to produce up to 40,000 impressions of four rela~
tively small images by using a single plate, rather than four plates as mentioned above. The result is a considerable saving of plate material, which is fairly expensive due to s~
1 the high cost of the silver used in the film emulsion.
One approach to effect a solution to the above mentioned problem is to laterally shift the plate selec-tively in vertical and horizontal directions to sequential]y position the center points of each quadrant at the optical axis. A mask having an aperture e~ual to the size of a particular quadrant could be positioned about the optical axis 50 that one quadrant at a time would be e~posed.
Where a large platemaker is employed, the shifting of the plate support station, both vertically ancl horizontally, would produce a heavy and cumbersome machine which would take up considerable space so that this relatively straight forward approach would result in a poor engineering design.
This approach for use with small film sizes is suggested by U.S. Patent No, 4,089,019 issued to R. Jonker. In accordance with the present invention, and in contrast to this patent, the large photosensitive plates are main-tained stationary during successive imaging and the original document or other graphic indicia are moved upon the copy-board to various positions surrounding the optical axisOU.S. Patent 3,737,227 to H. J. Rosenburgh illustrates slideable flat rectangular mask elements which are used to block light from variable width border areas. The teachings of this patent would be useless in obtaining the objectives of the present invention.
The presen-t invention relates to a platemaker comprising a copyboard and an optical imaging system for focussing images positioned on the copyboard upon a large stationary photosensitive printing plate. In operation, the platemaker maintains the plate stationary during the successive recordation of a plurality of the images focussed 1 onto portions of the plate. Moreover, pursuant to the teachings of the present invention a first liyht blocking mask is positioned closely adjacent to the plate, over-laying about half of the plate, and is movable in a first direction. Also, a second liyht blocking mask is posi-tioned closely adjacent to the plater overlaying about half of the plate, and is movable in a second direction transverse to the first direction~ With this arrangement, variable positioning of the first and second masks enables different or identical images to be successively recorded upon various portions of the platet thereby enabling a single plate to simultaneously print different or identical images.
Pursuant to further details of the present invention, a horizontally oriented thin flat rectangular mask is provided which overlays substantially half of the plate material adjacent the imaging plane and an additional vertically oriented thin flat rectangular mask is also provided adjacent the imaging plane. Each mask is trans-latable in a direction perpendicular to the direction of motion of the other mask to provide for the sequential exposure of four different quadrants of the plate, which in turn enables the production of four separate printings from a single large plate.
Additionally, the removal of -the horizontally oriented mask provides for the simultaneous imaging of the right half of the plate, and after shifting the verti-cally orlented mask, the imaging o~ the left half. In a similar manner, the removal of the vertically oriented plate provides for "two-up'` imaging of the upper and lower half of the plate by shifting the horizontally oriented mask. Removal of both masks enables a single ~ ~a5~8~
1 large image to be projected upon the entire exposure area of the plate.
Figure 1 illustrates components of the prior art platemaker; and Figures 2 and 3 schematically illustrate a simplified emhodiment of the present invention.
In Figure 1, vertically oriented photosensitive plate 1 is illustrated for receiving images focussed thereon by optical system 2. A horizontally oriented illuminated copyboard 3 bears graphic indicia such as documents thereon. The images oE the graphic indicia are directed by mirror 4 to the projection lens system 2 which focusses the images upon plate 1. Due to the "mirror imaging" characteristics of optical system 2 about the optical axis, document A at position 6 of the copyboard will be focussed within -the second plate quadrant area 7, document C will be focussed within the first quadrant area 8, document B will be focussed on the third ~uadrant area ~, and document D will be focussed upon the fourth quadrant area 11 as may be readily observed from the study of Figure 1.
In accordance with one embodiment of the present invention, the step and repeat adaptor comprises a ~irst vertically oriented thin flat rectangular mask or blade 12 which is mounted within a mask support frame 13 which in turn is positioned closely adjacent photosensltive plate 1 as illustrated in Figure 3. The invention could be practiced by providing a very thin transparent plastic sheet 14 forming the backing portion of the plate support frame 13 and such thin transparent sheet 14 is employed to illustra-te the principle of the invention in its most simplified manner in the interests of clarity and brevity.

ca5~8~
1 However, in the actual adaptor marketed by the assignee of the present invention, the -transparent member is not employed and the masks are supported at their edges by means forming no part of the invention.
Underlaying the first vertically oriented mas~.ing member 12 is a second horizontally oriented thin flat rectangular mask member 16 illustrated both in Fiyures

2 and 3. In accordance with the invention, mask 12 may be translated or shifted to the right or left and mask 16 may be shifted or translated upwardly or down-wardly. The translation of these masks could be carried out manually, or may be effected by providing conventional cable-pulley drive and an electrical circuit with conven-tional stop-limit switches which have not been illustrated -in detail since they form no part of the present invention.The latter structure is embodied in the adaptor actually marketed by the assignee of the present invention. "Y"
drive mechanism 17 schematically illustrated in Figure 2 would effect the translation of the second horizontally oriented mas]c member in the vertical or "Y" direction whereas "X" drive mechanism 18 would shift the vertically oriented mask memher in the horizontal "X" direction.
The invention operates as follows:
Let it be assumed that a document the size of the "A" area shown upon the copyboard area 6 ln Figure 1 is to be imaged upon the second quadrant 7 of the plate.
The vertically oriented mask 12 is positioned to the left and horizontally oriented mask 16 is moved to the upward portions as illustrated in Figure 2. The docu~

3 ment positioned upon copyboard portion 6 is therea~ter imaged upon the second quadrant portion 7 of the plate by operation of a conventional shut-ter (not shown).

1 Vertically oriented mask 12 is now shifted to the right in order to expose in like manner "B" quadrant portion 9 of the plate to the document now positioned in the "B"
area of the copyboard. The vertically oriented mask 12 remains at the right hand portion and horizontally oriented mask 16 is now lowered thereby to expose the fourth "D" quaclrant portion 11 of the plate to the image of the document positioned in the "D" portion of the copyboard, and lastly, vertically oriented mask 12 is shifted to the left to expose the "C" plate portion ~ to the document positioned upon the "C" portion of the copyboard. The document positioned at the various quadrants of the copyboard could be an identical docu-ment or could comprise different documents or other indicia depending upon the requirements of the printer.
In any case, the result is ~uadrupling the number of relatively small impressions which can be made by the printing press when the single large plate is mounted therein.
Now iet it be assumed that an even smaller document is to be imaged upon the second quadrant of the plate, such image occupyiny the area A', shown in Figure 2. Vertically oriented mask 12 could be translated to the right until the righthand edge 21 of the mask coin-cides with the vertical boundary 22 of area A'. In like manner, horizontally oriented mask 16 could be lowered unkil the bottom edge 23 coincides with the upper portion 24 of area A'. Preferably, the original "A" documents is now positioned at copyboard area A' shown in Figure 1 rather than adjacent the optical axis. In like manner, smaller documents may be imaged at other corner portions of the large photosensitive plate by repositioning the 8~
1 masks. Preferably, however, small images (less than 9 x 12) are placed any~lhere in the quadrant formed by the blades in any of their extreme "in-out" or up-do~m"
positions. To make smaller images, for instance ~ x 12, the customer could use a narrow roll of plate material and therefore, save material.
Now let it be assumed that it is desirable to image through a single exposure indicia occupyiny the entire lower portion of the plate (portions 7 and 9).
Vertically oriented mask 12 is removed and the horizon'cal mask is positioned to overlay the upward portion of the plate, and the indicia is positioned on copyboard portions A and P~. Thereafter, shifting of the horizontally oriented mask 16 in the "Y" direction to overlay the lower plate portion would enable the imaging of the entire upper half of the plate ("two-up" imaging). Should it be desirable to image the left and right hand halves of the plate, the horiæontally oriented mask 16 would be removed and the remaining vertically oriented mask 12 would be shifted in the "X" direction to occupy the left or right hand portion of the plate to produce imaging of the left and right hand portions in like manner.
Should the opexator desire to expose the entire plate to one large image, both masks are removed.
Another advantage of the present invention is the absence of any image degradation because the blades are in close proximity to the plate material. There is no opportunity for stray light to fog the plate. Methods !
whereby shielding is done directly on the copyboard with 3 matte black or ruby red could still reflect light onto the plate material. With long exposure times, this problem increases~

Claims

WE CLAIM:

1. In a platemaker having a copyboard and an optical imaging system for enabling the focussing of images positioned on said copyboard upon a large stationary photosensitive print-ing plate, said platemaker further including means for maintain-ing said plate stationary during the successive recordation of a plurality of said images focussed upon portions of said plate, the improvement comprising:
a first light blocking mask positioned closely adja-cent said plate at all times while in said platemaker overlay-ing about half of said plate and movable in a first direction;
a second light blocking mask positioned closely adjacent said plate at all times while in said platemaker over-laying about half of said plate and movable in a second direc-tion transverse to said first direction so that the variable positioning of said first and second masks enable different or identical images to be successively recorded upon various portions of said plate, to enable a single plate to simultan-eously print different or identical images.

2. The combination as set forth in claim 1 further including means for permitting the removal of at least one of said masks from positions overlaying said plate.

3. The combination as set forth in claims 1 or 2, wherein said first and second masks comprise thin flat non-apertured blades.

4. In a platemaker having a copyboard and an optical imaging system for enabling the focussing of images positioned on said copyboard upon a large rectangular photosensitive printing plate, said platemaker further including means for maintaining said rectangular plate stationary during the succ-essive recordation of a plurality of said images focussed upon portions of said plate, the improvement comprising:
a first rectangular mask positioned closely adjacent said plate at all times while in said platemaker overlaying about half of said plate and movable in a first direction;
a second rectangular mask positioned closely adjacent said plate at all times while in said platemaker overlaying about half of said plate and movable in a second direction perpendicular to said first direction so that the variable positioning of said first and second masks enable different or identical images to be successively recorded upon various portions of said plate to enable a single plate to simultaneously print different or identical images.

5. The combination as set forth in claim 4, further including means for permitting the removal of said rectangular masks from the vicinity of said plate.

6. The combination as set forth in claim 5, wherein said first and second masks comprise thin non-apertured flat sheets.

7. In a platemaker having a copyboard and an optical imaging system for enabling the focussing of images positioned on said copyboard upon a large vertically oriented photosens-itive printing plate, said platemaker further including means for maintaining said plate stationary during the successive recordation of a plurality of said images focussed upon portions of said plate the improvement comprising:
a first non-apertured rectangular vertically oriented mask positioned closely adjacent said plate at all times while in said platemaker overlaying about half of said plate and movable in a horizontal direction;
a second non-apertured horizontally oriented rectan-gular mask positioned closely adjacent said plate at all times while in said platemaker overlaying about half of said plate and movable in a vertical direction so that the variable posi-tioning of said first and second masks enable four different or identical images to be successively recorded upon various portions of said plate to enable a single plate to simultaneous-ly print different or identical images.

8. The combination as set forth in claim 7, further including means for permitting the removal of said masks from the vicinity of said plate.

9. The combination as set forth in claim 7 or 8, wherein said first and second masks comprise thin flat non-apertured sheets of the same size.