GB2224136A

GB2224136A - Auxiliary sheet for use with film holder of step-and-repeat machine

Info

Publication number: GB2224136A
Application number: GB8824509A
Authority: GB
Inventors: William Denison Wright
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1988-10-19
Filing date: 1988-10-19
Publication date: 1990-04-25
Anticipated expiration: 2008-10-19
Also published as: JP2694289B2; JPH02110465A; GB2224136B; GB8824509D0

Abstract

A transparent auxiliary sheet (1) for use with a film holder (20) of a step-and-repeat machine in supporting an original film, which auxiliary sheet includes at least a first layer (1a) defining a plurality of suction bores (2) at the peripheral regions of the original film with a matt surface M outside this region, and a second layer (1b) defining a plurality of radial communicating channels (3) for placing the said suction bores in communication with exhaust grooves (25) of the film holder, whereby the original film (8) is suction-supported by the auxiliary sheet. Sheet (1) is vacuum held on film holder (20) by suction grooves (24). <IMAGE>

Description

Description of Invention "Auxiliary sheet for use with film holder of step-andrepeat machine" THIS INVENTION concerns step-and-repeat machines,which are one type of photoengraving machines, and more particularly relates to auxiliary sheets for allowing original films to be supported by a film holder of the step-and-repeat machine.

Step-and-repeat machines are apparatus for transferring an image or images from an original film to a plurality of positions on a photosensitive material such as a PS plate, and are classified broadly into the flat or horizontal type and the vertical type. Figure 10 of the accompanying drawings is a perspective view of one example of the flat type step-and-repeat machines.

This machine comprises a sensitive material holder 10 for supporting a photosensitive material 11 by suction, an original film holder 20 controllable to set in position in X-Y directions over the sensitive material holder 10, a printing light source 30 mounted above the film holder 20, and a film feeder 40 and a film discharge 50 disposed, one on top of the other, under the film holder 20 to be movable in and out in the directions of arrow A. The film holder 20 supporting an original film 8 by suction under a bottom surface thereof is lowered at X-Y coordinate positions to place the original film 8 into tight contact with the photosensitive material 11, and the light source 30 is turned on, to print an image or images successively.The original film 8 whose image or images have been printed is placed on the film discharge 50, and another original film is picked up from the film feeder 40 for the next printing operation.

Generally, there are a plurality of standardized sizes for the original film 8. Figure 11 shows a known device (hereinafter called Known Example 1) for supporting different size original films 8, and Figures 14 and 15 show another known device (hereinafter called Known Example 2) available for the same purpose.

As shown in Figure 11, Known Example 1 comprises a plurality of interchangeable film holders 20a and 20b corresponding to the different size original films 8, the film holders 20a and 20b being manually replaceable as necessary. Thus, a plurality of original films, as long as they are the same size, may be placed in a batch on the film feeder 40 (Figure 10) to allow a series of printing operations to be carried out automatically, including automatic changing of the original films 8. Each original film 8 defines pinholes 4a and 4b for accurate position setting through register pins provided on the film feeder 40.

Referring to Figure 15, Known Example 2 comprises auxiliary transparent sheets 9 which are large enough to accommodate the different sizes of original films 8 affixed thereto. As shown in Figure 14, an original film 8 is supported by the film holder 20 through the auxiliary sheet 9 (Figure 1 of Japanese Patent Publication Kokai No. 63-73229).

In the latter case, the original films 8 are bonded to the auxiliary sheets 9 of a fixed size in advance, and are then placed in a batch on the film feeder 40 (Figure 10). A series of printing operations may thus be carried out automatically without necessitating manual changing on the film holder 20. In Figure 14, reference number 21 indicates a transparent plate, number 22 indicates an edge frame, and number 24 indicates suction grooves for drawing the auxiliary sheet 9.

In Known Example 1 (Figure 11), a plurality of film holders are provided according to the standard sizes of original film 8, which holders are changed manually when necessary. This approach has the following disadvantages: (A) Manual changing of the film holders 20a and 20b is troublesome, and is laborious since the film holders 20a and 20b are heavy.

(B) Each film holder 20 defines a light transmitting window 23a having fixed dimensions just for printing the image of a particular size original film 8.

Even when printing an image from a small size original film 8, areas surrounding the image are shielded against light by the window frame 23. This construction is not suited for a special exposure operation described hereunder.

On the other hand, Known Example 2 (Figures 14 and 15) involves no change of film holder 20 and is suited for the special exposure operation. However, the necessity to bond the original films 8 to precise positions of the large auxiliary sheets 9 in advance has the following disadvantages: C) Many large auxiliary sheets 9 are required, which results in high cost.

(D) Used original films 8 are often stored as bonded to the auxiliary sheets 9 since the preparatory work of bonding the original films 8 to the auxiliary sheets 9 takes time and trouble. This practice requires a large space.

The object of this invention is to eliminate the above disadvantages (A) - (D).

The special exposure operation mentioned above is an operation for exposing areas of the photosensitive plate other than image areas, which is effected where a positive type photosensitive plate is used to obtain a printing plate as shown in Figure 12, for example. If the areas surrounding the image areas 1-4 were left unexposed, ink would adhere also to these marginal areas during printout. The special exposure operation is necessary to avoid such a situation.

To carry out this exposure operation, as shown in phantom lines in Figure 14, positionally controllable shields 26 are provided on the upper surface of the transparent plate 21 and are moved over the transparent plate 21 in the sequence shown in Figure 13 to print an image or images at a plurality of positions.

In other words, when printing images 1-4, selected areas are shielded against light by the shields 26 as shown in Figures 13 (A) to (D), thereby printing the images 1-4 and exposing the marginal areas at the same time.

This invention provides, as means to eliminate the disadvantages noted above, a device having the functions of both an interchangeable film holder and an auxiliary sheet.

More particularly, this invention provides a transparent auxiliary sheet for use with a film holder of a step-and-repeat machine in supporting an original film, which auxiliary sheet includes at least a first layer defining a plurality of suction bores for drawing peripheral regions of the original film, and a second layer defining a plurality of radial communicating channels for placing the said suction bores in communication with exhaust grooves of the film holder, whereby the original film is suction-supported by the auxiliary sheet.

A transparent auxiliary sheet embodying this invention is sufficiently large and is constructed as above. This auxiliary sheet supports an original film as follows: First, as shown in Figure 2, the auxiliary sheet 1 is supported by the film holder 20 by suction through auxiliary sheet suction grooves 24 defined in the film holder 20. Next, exhaust grooves 25 of the film holder 20 are evacuated to establish negative pressure in suction bores 2 of the first layer 1a communicating with the exhaust grooves 25 through communicating slots 3 of the second layer 1b. Consequently, the original film 8 is supported by the auxiliary sheet 1 by suction through the suction bores 2.

According to this invention, a plurality of such auxiliary sheets 1 may just be made available for different standard size original films 8. These auxiliary sheets 8 are automatically attachable and detachable as are the known auxiliary sheets 9. The auxiliary sheets of this invention allow the special exposure operation noted hereinbefore as well.

Further, it is not necessary for the original film 8 to be bonded to an auxiliary sheet larger than the original film.

In order that the invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an auxiliary sheet for use with a film holder according to a first embodiment of this invention; Figure 2 is a sectional view of the auxiliary sheet in use; Figures 3 and 4 are sectional views corresponding to a portion marked I in Figure 2 and showing a second embodiment and a third embodiment, respective; Figures 5 (A)-(C) are plan views of three layers constituting the auxiliary sheet of the third embodiment; Figure 6 is a bottom view of the film holder; Figure 7 is a side view of a film feeder; Figures 8 and 9 are fragmentary sectional views showing how an original film is suction-supported; Figure 10 is a perspective view of a flat type step-and-repeat machine;; Figure 11 is a perspective view of known interchangeable film holders; Figure 12 is a diagram showing an arrangement of images printed in a step-and-repeat mode; Figure 13 is an explanatory view illustrating the sequence of the step-and-repeat printing involving a "printaway" operation; Figure 14 is a sectional view of a known auxiliary sheet in use; and Figure 15 is a plan view showing how known auxiliary sheets are used.

Figure 1 is a perspective view of an auxiliary sheet 1 according to a first embodiment and Figure 2 is a sectional view of the auxiliary sheet 1 in use.

Reference number 1 in these figures indicates the entire auxiliary sheet which consists of two layers la and 1b bonded together.

The first layer la defines a plurality of suction bores 2 arranged in a rectangle for drawing a standard size original film 8. The second layer 1b defines communicating channels in the form of slots 3 arranged radially and providing communication between the suction bores 2 and exhaust grooves 25 defined in a film holder 20. Thus, as shown in figure 2, the suction bores 2 communicate with the exhaust grooves 25 of the film holder 20 through the slots 3 to draw and support the original film 8.

The two layers 1a and ib may be bonded together throughout their entire area, or may be bonded only at peripheral positions and at positions adjacent pinholes 4a and 4b. The required purpose will be served if sufficient airtightness is achieved to support the original film 8.

The first layer la preferably is diffusiontreated, as shown at reference M, outside an image region J marked in the dotted line.

The diffusion treatment is effected by ruffling the adhesion surface into a matt surface for diffusing printing light. This treatment produces the effect of preventing shadows of edges of the suction bores 2 and communicating slots 3 defined in the respective layers from being printed on the photosensitive material. The diffusion treatment is limited to the areas outside the image region J in order to avoid fading of image lines and halftone images of the original film 8 as printed on the photosensitive material.

Figure 3 is a sectional view of a second embodiment, which corresponds to the portion referenced I in Figure 2.

The second layer 1b in this embodiment is formed of a thick sheet material and defines communicating grooves 3a instead of the communicating slots 3. In this case, the second layer Ib is diffusion-treated over selected areas of the upper surface S (namely the surface for contacting -the transparent plate 21). The suction grooves 24 defined inwardly in the film holder 20 act as the grooves for drawing the auxiliary sheet 1, with the exhaust grooves 25 defined outwardly acting as the grooves for drawing the original film 8.

Figure 4 corresponds to Figure 3 and shows a third embodiment.

The auxiliary sheet 1 in this embodiment comprises three layers la, 1b, ic as shown in Figures 5 (A), (B) and (C). The third layer Ic is diffusion-treated over selected areas shown in shading, and defines bores 5 for placing the communicating slots 3 of the second layer 1b with the exhaust grooves 25 of the film holder 20.

Reference number 6 in Figure 5 indicates bores for receiving locating pins (referenced 42 in Figure 7) to be described later.

How a printing operation is carried out with the described auxiliary sheet 1 will now be described.

(1) First, as shown in Figure 7, the auxiliary sheet 1 is placed in position on the film feeder 40 using a pair of locating pins 41. The locating pins 42 for positioning the original film 42 are retractably arranged to present no obstruction to mounting of the auxiliary sheet 1.

(2) The film feeder 40 is advanced to the position under the film holder 20, then the film holder 20 is lowered and air is exhausted through the suction grooves 24 to draw the auxiliary sheet 1. Figure 6 shows the film holder 20 from underneath. As seen, the bottom of edge frame 22 defines bores 27 for receiving the auxiliary sheet locating pins 41. These locating pins 41 thus do not obstruct the film holder 20 lowering and supporting the auxiliary sheet 1 by suction. Thereafter the film holder 20 is raised once, and then the film feeder 40 is withdrawn.

(3) A required number of standard size original films 8 are stacked in position on the film feeder 40 using the pair of locating pins 42.

(4) The film feeder 40 is advanced to the position under the film holder 20 again, the film holder 20 is lowered and the uppermost one of the stacked original films 8 is picked up by means of the suction bores 2 defined in the bottom of the auxiliary sheet 1. Figures 8 and 9 are sectional views illustrating how the original film 8 is drawn and supported at this time. Figure 8 shows the case where the auxiliary sheet 1 includes the bores 6 shown in Figure 5 for receiving the locating pins 42, whereas Figure 9 shows the case where the auxiliary sheet 1 does not include the bores 6. As seen, each of the locating pins 42 for positioning the original film 8 is urged to a projecting position by a spring 43, and is depressed through contact with the transparent plate 21 of film holder 20 or with the auxiliary sheet 1.

(5) The film holder 20 is moved under control to a selected X-Y position on the sensitive material holder 10, and is lowered at that position to place the original film 8 in tight contact with the photosensitive material 11. Then the light source 30 is turned on to effect printing. In this way, the image or images of the film 8 is/are printed in a plurality of positions on the photosensitive material 11.

(6) The original film 8 is discharged after use to the film discharge 50 by advancing the film discharge 50 to the position under the film holder 20 and stopping the suction through the exhaust groove 25 (with a small amount of air blown out of the exhaust groove 25 as necessary). Thereafter the film discharge 50 is replaced with the film feeder 40 and the next original film 8 is drawn and supported. Then the step (5) above is repeated to effect further printing.

(7) For printing from different size original films 8, the auxiliary sheet 1 to be replaced is discharged to the film discharge 50, and the steps (1) to (5) above are repeated.

The foregoing examples have been described assuming that a plurality of different size auxiliary sheets 1, such as 8x10" (20.3x25.4cm), 10x12" (25.4x30.Scm), 14x17" (35.6x43.2cm), 16x18,, (40.6x45.7cm), 20x24" (50.8x61.Ocm) etc are made available for the standard sizes of original films 8. However, certain intermediate or small size auxiliary sheets may be dispensed with, in which case each original film is applied to an additional sheet one size larger than the film to be suction-supported by the auxiliary sheet of this invention.

In other words, the auxiliary sheets according to this invention may be used as combined with Known Example 2 as regards less frequently used sizes. This arrangement allows for low cost as a whole.

While the examples have been described in relation to a flat or horizontal type step-and-repeat machine, the invention is not limited to such application. This invention may be practised likewise with an inclined type or vertical type step-and-repeat machine.

As is clear from the foregoing description, this invention provides a transparent auxiliary sheet including at least two layers, the first layer defining suction bores for communicating with the exhaust grooves of the film holder through communicating slots defined in the second layer. The auxiliary sheet supports the original film by suction through these bores. The construction according to this invention produces the following effects: (A) The auxiliary sheet may just be placed on the feeder of a step-and-repeat machine for automatic changing. Thus, replacement is easier and simpler than in Known Example 1 which requires the heavy film holders to be replaced.

(B) The auxiliary sheet is transparent and, therefore, is suited for the special exposure operation noted hereinbefore.

(C) The auxiliary sheet is used to support the original film by suction, which dispenses with the necessity, as in Known Example 2, to bond the original film to a large size auxiliary sheet. This feature helps towards low cost.

(D) Only a series of auxiliary sheets may be provided for standard sizes of the original films. It is unnecessary to provide an auxiliary sheet for each original film as in Known Example 2, and the preparatory operation of bonding the original films to the auxiliary sheets may be dispensed with. Further, the auxiliary sheets may be used repeatedly without separating the original films therefrom or cleaning the auxiliary sheets.

Claims

CLAIMS:

1. A transparent auxiliary sheet for use with a film holder of a step-and-repeat machine in supporting an original film, which auxiliary sheet includes at least a first layer defining a plurality of suction bores for drawing peripheral regions of the original film, and a second layer defining a plurality of radial communicating channels for placing the said suction bores in communication with exhaust grooves of the film holder, whereby the original film is suction-supported by the auxiliary sheet.

2. An auxiliary sheet according to claim 1, wherein the communicating channels are slots formed in the said second layer.

3. An auxiliary sheet according to claim 1, wherein the communicating channels are grooves formed in the said second layer.

4. An auxiliary sheet according to claim 2, comprising a third layer defining communicating bores for placing the communicating slots of the second layer in communication with the exhaust grooves of the film holder.

5. An auxiliary sheet according to any preceding claim, wherein the first or third layer is diffusiontreated over selected areas thereof.

6. A transparent auxiliary sheet for use with a film holder of a step-and-repeat machine in supporting an original film, substantially as hereinbefore described with reference to Figures 1 to 9 of the accompanying drawings.

7. Any novel feature or combination of features described herein.