Burn-out frame for a copy print machine

Abstract: Burn-out frame for a copy print machine, comprising a support table on which a film or a printing plate is intended to be mounted, and a copy print frame having exposure light for providing a print of one and the same original film or a series of different original films onto said film or printing plate, and in which the print frame comprises a frame having a transparent glass plate (11), which at the bottom surface thereof is formed with at least one downwardly opening groove (12, 14) for vacuum connecting an original film (13) and eventually a masking film (15), and one or more bores and/or channels (16, 17) opening in said groove (12) for connecting the vacuum groove (12) or grooves to a source of sub-pressure, and in which the glass (11) of the print frame is larger than the largest original film (13) of a predetermined standard size intended to be copied, and in which the part (19) of the print frame glass corresponding to the largest image area of the original film (13) is clear, whereas the parts (18) of the print frame glass located outside said largest image area are made diffusing on a surface between the surface of the print frame glass (11) formed with the vacuum grooves (12) and the exposure light, so as to allow an exposure to a composite film or a composite printing plate (21) outside the outer edges of the image area.

Description: The present invention generally relates to an improvement in a step and repeat (copying) machine and the invention is more particularly directed to a contact copy print system according to claim 1. By step and repeat machine is meant a copying machine having a support table on which a composite film or a printing plate is intended to be mounted and a printing frame, which is movable over said support table and which has an exposure light means, and which printing frame can be moved to different positions over the composite film or the printing plate and provide a printing at said several different positions of one and the same film original or a series of different film originals. (By original is meant the negative or positive film having text and pictures and intended to be printed onto a composite film, a printing plate etc.) In such a copying machine composite films or printing plates are prepared, for instance a film or plate for printing of a predetermined number of pages of a book, a newspaper, a catalogue etc. Thereby it is important that the positioning of the pages is correct, so that the pages take the correct position on the composite film or the printing plate, and that all parts of the film or plate round the entire double page which do not exhibit an image are eliminated. The invention is mainly, but not exclusively, useful for a contact printing system providing so called positiv printing (copying), and having a burn-our frame, by the use of which the exposure light is intended to "burn out" those parts of the composite film or the printing plate which wear no images, whereas the image parts are remained after the exposure and the development of the film or the plate. The invention also may be utilized, however, for negative printing and for other purposes. When copy printing original films by means of a step and repeat print machine it has been usual to use a printing frame having a glass plate which is, at the bottom surface thereof, formed with vacuum channels intended to vacuum (suction) connect an original film, which in connection to the printing thereof onto a composite film or a printing plate is put into intimate contact therewith, whereupon the exposure light is lit on and the original film is printed on the composite film or the printing plate. In order to avoid illumination and light damaging of the parts of the composite film or the printing plate located outside the original film, and on which parts other original films are to be printed in the succeeding printing steps it has been usual to use a masking frame (or several masking frames) consisting of a non-transparent material, generally metal, and generally having a central opening the form and size of which corresponds to the intended area of exposure, which area varies depending on the size of the image presenting part of the original film. Such a masking frame is for example described in DE-A-29 12 548. DD-A-150 372 discloses another device for reproducing photographic images to provide them with a frame surrounding the image area. This reproduction device comprises a copy print frame carrying a transparent plate with a lower surface portion and placed above a film or a printing material, an upper surface portion oriented towards the light source having a transparent, clear area and a surrounding outer area which is made light diffusing, so as to allow an exposure of the recording film outside the outer edges of the image area. However, this known reproducing system does not have any vacuum grooves for holding an original film, and the printing of the original film onto the receiving film is effected by a lens and not by direct contact of the copying partners as in the claimed invention. The image free parts between the printing pages can easily be exposed off in that the original film is made slightly "bleeding" or larger than the image presenting surface, however not of such large size as to influence the image presenting parts of the adjacent pages. According to this method it is, however, not possible to expose off (or burn out) the parts of the composite film or the printing plate corresponding to the free areas outside the corner pages or edge pages. This has to be done in a separate operation, whereby the previously exposed areas are masked over and the outer, still non-exposed, areas (the edges) of the composite film or the plate are exposed. The object of the invention is to suggest a contact print system, which makes it possible to execute any necessary exposures in one and the same operation, which means both to expose the original film and to "burn-out" (remove) the parts of the composite film or the printing plate facing outwardly towards the edges of the composite film or the printing plate. According to the invention this is achieved by the features of claim 1. The channels or grooves at the bottom surface of the glass are arranged to suction contact both an original film and a masking film which, for the pages which are to be printed at the outermost areas of the composite film or the printing plate, cover only the inwardly facing parts, whereas said masking film leaves the outwardly facing edge or edges free for illumination, whereby consequently said outer areas of the positive composite film or plate are exposed or "burnt out" at the same time as the orignial film is exposed. The advantages of said printing method is that the composite film or plate can be prepared in one single process step. It may happen, however, that the vaccum channels for vacuum connecting the original film and the masking film and provided at the bottom surface of the printing machine glass give shadows of the generally sharp exposure light and present lines or other formations on the composite film or the printing plate. For eliminating this problem it has been found necessary to arrange for such a diffusing or other modification of this part of the light passing the glass plate that shadow phenomenas are avoided at the same time as the light passing the glass plate for printing the original film onto the composite film is left uninfluenced and strong and sharp. Therefore, according to a preferred embodiment of the invention, the parts of the glass plate located outside the image carrying area of the original film are made frosted for diffusing purposes, preferably in that the upper surface of the glass of the print machine is blasted. It may happen that the blasted or otherwise frosted surface becomes worn by time, or that the blasting surface becomes wet at some place, so that the light passes un-diffused also through said worn or wet part, whereby the vacuum channels at the bottom surface of the glass may still give shadows. For protecting the frosted surface a cover plate of a clear, transparent material can be glued or otherwise attached on top of the printing glass. This is in particular advantageous in that the connection bores or grooves for the vacuum channels at the bottom surface of the printing glass can be cut in the form of open grooves at the upper surface of the printing glass, which grooves are sealed by the cover glass. Preferably the frosting is made at the bottom surface of the cover glass in order to completely cover the frosting of the surfaces which have no images and whereby said frosting is protected against any action. As an alternative to frosting of the glass surface a frosting-foil can be mounted on the upper surface of the print glass or between the cover glass and the print glass. It may also be advantageous to provide the frosting foil in the form of a double-sticking tape foil which serves, at the same time, also to join the print glass and the cover glass. It is obvious that there should be a special print frame having a glass clear print opening of special form and size for each format of the image supporting surface, and that the vacuum channels provided at the bottom surface of the print glass should be adapted to the actual format of the original film and of the masking film. Now the invention is to be described more closely with reference to the accompanying drawings. It is, however, to be understood that the embodiments of the invention described and illustrated in the following are only illustrating examples, and that many variations and modifications may be presented within the scope of the appended claims. In the drawings figure 1 diagrammatically shows a cross section of a copy print frame of a step and repeat copying machine of known type. Figure 2 correspondingly shows a print frame according to the invention. Figure 3 is a perspective view seen obliquely from above of a print frame according to the invention. Figure 4 shows a cross section through a modified print frame according to the invention. In previously known step and repeat copying machines of the above mentioned type the print frame, which is shown in figure 1, generally comprises a vertically up and down movable metal frame 1 carrying a glass plate 2 and having vacuum grooves 3a, 3b at the bottom surface of the metal frame 1, which grooves are connected to a source of sub-pressure over connection channels 4. The vacuum grooves 3a, 3b vacuum connect a masking film 5a and an original film 5b to the bottom surface of the metal frame 1. On the top surface of the metal frame 1 there is a cover plate 6 of a material like a PVC-resin, which plate covers and seals the connection channels 4 and which has a recess 7 the form and size of which corresponds to the intended size of the page to be printed to a composite film 8 - or to the intended image area of the of the original film 5b. When the print frame together with the original film 5b which is vacuum connected thereto has been brought into contact with the composite film 8 or the printing plate mounted on the support table a light source (not illustrated) is illuminated and the light source projects a light beam to the print frame. The light passing through the recess 7 of the print frame makes the text and/or images of the original film 5b printed onto the composite film 8. The light falling outside the recess 7 is stopped by the cover plate 6 which prevents the light from exposing or burning out the corresponding photosensitive material of the composite film. Such material located outside the recess 7, which has to be removed before the composite film or the printing plate can be used, must be exposed or burnt out in a succeeding operation by a new exposing, whereby the previously exposed parts have to be correspondingly masked off. The print frame diagrammatically shown in figure 2 is intended for exposing according to the so called positive method, whereby a light beam exposes or burns out the parts of the composite film or the printing plate which have no images. The print frame comprises a transparent plate 11, for instance af an acrylate material like PLEXI-glass, which glass preferably is of a type which is not UV protective. The bottom surface of the print glass 11 is formed with at least two sets of vacuum grooves, an outer groove 12 for vacuum connecting an original film 13 and an inner groove 14 for vacuum connecting a masking film 15. In the case of positive printing there is normally no need for a masking film since the exposure has to be made as far as to edges of the composite film or the printing plate. For making it possible to use the same printing frame also for negative printing the frame preferably, in spite thereof, formed with means for vacuum connecting a masking film. The two sets of grooves 12 and 14 are connected to a source of sub-pressure (not shown) over channels 16 and 17. As shown in figure 2 the grooves 12 for the original film must be located outside the outer edges of the masking film 15. For practical reasons the grooves 12 and 14 are provided rather close to each other. The upper surface of the print glass 11 is formed light diffusing, for instance frosted or blasted over a surface 18 outside the glass clear surface 19 of the original film. The object of frosting the surface 18 is to provide a light-diffused light beam passing the glass for eliminating the risk of appearance of shadows and following lines on the composite film depending on light refraction phenomenas from the vacuum grooves 12 and 14 and from the connection channelse 16 and 17. By using the print frame shown in figure 2 the original film 13 is printed on the composite film 21 or the printing plate at the same time as the parts thereof located outside the original film, except for possible parts which are masked by means of the masking film 15, are exposed or burnt out. Therefore, in this case there is no need for an additional illumination step for burning out the parts located outside the original film. It should be noted that the light opening of the copy print frame has to be at least large enough to allow the light to reach as far as to the edges of the composite film or the printing plate, so that no unexposed areas are left adjacent the said edges. The apparatus shown on figure 2 has been described with reference to printing of one single image (page) on the composite film, but normally several images are printed on the composite film and in such cases a further mask must be used for protecting the adjacent areas of the composite film, onto which said further images are to be printed. Such an apparatus is diagrammatically shown in figure 3. A composite film 21 is mounted on a support table 20, and over said film 21 there is provided a printing unit comprising a printing frame 22 including a not illustrated lighting means, and an original magazine and an original exchanging device etc., which means are movable in two mutually perpendicular directions (the X- and the Y-direction) for exact positioning of the print frame in four illustrated positions 23, 24, 25 and 26 resp. corresponding to four different print pages. In figure 3 the print frame is shown ready to print page 23 at the lower right corner of the composite film 21. The print frame glass 11 is of the same type as shown in figure 2, and on top or the frosted print frame glass 11 there is a mask or a curtain 27 which allows an illumination and exposure of the image 23 and the right edge 28 and the lower edge 29 outside the image area or the page 23 resp. All other parts of the composite film are left unexposed. The original film in the print frame 22 for page 23 is now exchanged by the original film for page 24, and the print frame is moved in the Y-direction to an exact position over the page area 24 of the composite film corresponding to the intended position for said print page, and the mask or the curtain 27 is moved so that an exposure can be made both of the print page 24 and also of the edge above and the edge aside of said page 24, whereas the remaining parts of the composite film are screened from illumination by the mask (and curtains and similar means outside the print frame). As described above page by page can be printed whereby both the page image is printed and the parts outside the page image which do not, or should not, have an image are burnt out (exposed). Figure 4 fragmentarily shows a practical embodiment of a print frame according to the invention. The print frame comprises a base plate 11a of a transparent material, for instance glass, acrylic resin (without UV protection) or a similar plate, and a cover plate 11b of the same or a similar transparent material. At the bottom surface of the base plate 11a there are outer vacuum grooves 12 for holding an original film 13 and inner vacuum grooves 14 for holding a mask film 15. Bores are drilled from the grooves 12 and 14 up to the upper surface of the base plate, from which points channel forming grooves 16′ and 17′ resp. extend to the edges of the plate. It is intended that the cover plate 11b should cover and seal the top of the channel grooves 16′ and 17′. Thereby said vacuum channels can be made simply. The cover plate 11b is blasted or otherwise frosted over the areas 18 outside the glass clear area 19 adapted for exposure of the original film, and the cover plate 11b is, by means of a glue joint, a double sticking tape or a similar means secured on top of the base plate 11a with the frosted part 18 of the cover plate facing the base plate 11a. Thereby the frosted part is protected against such handling that might cause shadows of the vacuum grooves and/or the vacuum channels on the composite film. Instead of frosting, for instance blasting or etching, the bottom surface of the cover plate it is possible to place a frosted or opal coloured tape between the base plate and the cover plate, or alternatively on top of the cover plate. Alternatively it is also possible to use a frosted or opal coloured double sticking tape for joining the base plate and the cover plate.

Claims: A contact copy print system for printing original films each of said one or more original films having an original image area and an original non-image area outside of said original image area, comprising a support table (20) for carrying a composite film or a composite printing plate (21), a copy print frame frame having a transparent glass plate (11; 11a, 11b), an exposure light source for providing a print of one and the same original film or a series of different original films (13) onto said film or printing plate (21) positioned on the support table (20); wherein said transparent glass plate (11; 11a, 11b) is at the bottom surface thereof formed with at least one downwardly opening groove (12) for vacuum connecting an original film (13) and one or more bores and/or channels (16, 17) coupled to said vacuum groove(s) (12), extending through said copy print glass (11; 11a, 11b) and connecting said vacuum groove (12) or grooves to a source of sub-pressure, the transparent glass plate (11; 11a, 11b) comprises both a transparent, clear area (19) of a predetermined size, preferably corresponding to the largest image area of an original film (13) intended to be copied by means of the contact printing system, and an outer area (18) extending outside said light transparent area (19) and which outer area (18) is made light-diffusing on the surface facing the exposure light source and covers the part of the transparent glass plate (11; 11a) outside the clear area (19), which is formed with said vacuum grooves (12), so as to allow an exposure to the composite film or the composite printing plate (21) outside the outer edges of the image area. A contact print system according to claim 1, wherein the light-diffusing surface of the transparent glass plate (11; 11a) is opalized or frosted, by having been blasted or etched, for eliminating any shadows which might appear on the copy film or the printing plate (21) depending on the presence of the vacuum groove (12) and/or the vacuum channels (16, 17). A contact print system according to claim 2, wherein the light-diffusing area of the transparent glass plate (11; 11b) is formed in that a lustreless foil or tape is applied to said area (18). A contact print system according to any of the preceding claims, wherein the transparent glass plate comprises a base plate (11a) and on top thereof a tightly connected cover plate (11b), and in that the light-diffusing area is formed on the side of the cover plate (11b) facing the base plate (11a). A contact print system according to claim 4, wherein the vacuum bores and/or channels (16', 17') are provided in the form of grooves on top of the base plate (11a) which grooves are covered by means of the cover plate (11b) to form longitudinal bores. A contact print system according to any of the preceding claims, wherein the system is intended for stepwise printing of several original films (13) onto one and the same composite film (21) or printing plate, and in which the print frame (22) is movable in at least two directions perpendicular to each other and up and down in relation to the collection film (21) or printing plate, and wherein the print frame is formed at the upper surface thereof with means (27) for masking off the parts of the original film which are not to be illuminated during the printing of the original film and the illumination of at least some areas (28, 29) outside said original film. A contact print system according to claim 6, wherein the means for masking the film is formed as movable masking plates or curtains (27) which can be adjusted for masking any desired area outside the area corresponding to the maximum image area of the original film (13).

Inventors: LUNDAHL LEIF, WIKSTROEM CHRISTER, LUNDAHL, LEIF, WIKSTROEM, CHRISTER, Wikström, Christer
Applicants: MISOMEX AB
Application year: 1988
Main classification: G03B27
IPC codes: G03F7, G03B27