GB2070261A

GB2070261A - Contact printer

Info

Publication number: GB2070261A
Application number: GB8101386A
Authority: GB
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1980-02-06
Filing date: 1981-01-16
Publication date: 1981-09-03
Also published as: FR2476335A1; FR2476335B1; GB2070261B; DE3103739A1; JPS6012107Y2; JPS56115151U

Abstract

A contact printer having a printer body 1, a rectangular glass plate 5 provided on the upper surface of said printer body and adapted to support a photographic negative and a photosensitive material thereon, and a holding sheet 9 which can be extended over and pressed towards said glass plate 5, as it is unwound from a holding sheet winding roller 10 reciprocable over the glass plate, the glass plate being supported at those opposite edge portions thereof which are parallel to the axes of said roller, so that deflections in the glass plate due to its weight are uniform between said edges. Optionally, a press roller 11 may be provided, and air may be sucked out through a nozzle 12. <IMAGE>

Description

SPECIFICATION Contact printer The present invention relates to a contact printer for use in conducting contact printing on a photosensitive material, such as a film or a printing plate.

A conventional contact printer consists of a printer body, a rectangular glass plate provided at the upper side of the printer body, a movable box straddling the glass plate and adapted to be reciprocated over the glass plate by an endless chain, and a holding sheet winding roller and a press roller disposed parallel to each other and rotatably supported in the movable box.

In order to carry out exposure with the above contact printer, a photographic negative and a photosensitive material are placed upon one another on the glass plate, and the box is forwardly moved to unwind the holding sheet from the holding sheet winding roller and extend it over the glass plate. The holding sheet is thus extended over the glass plate and is immediately pressed by the press roller to force out the air from the space between the glass plate and holding sheet.

In a conventional contact printer, however, the glass plate is supported around all sides of its periphery in a retainer frame provided on the printer body. so that the glass plate is necessarily slightly bent downwards by its own weight in its central portion. Accordingly, a a press roller which has a central bulge is used to force the air out. However, it is difficult to determine the appropriate size of the bulge in the press roller since the deflection of the glass plate and strain occurring in the printer body affect it and are hard to determine.

Since the glass plate is supported throuyhout its periphery. the deflection of the glass plate also momentarily varies as the press roller advances. Therefore. it is very difficult to design a press roller with an appropriate bulge which strictly matches the glass plate, so thst a perfect contact between the photographic negative and the photosensitive material cannot be relied on which is inconvenient.

IT is an aim of the present invention to reduce these difficulties.

According to the present,invention there is provided a contact printer having a printer bodv, a rectangular glass plate provided on the upper surface of said printer body and adapted to support a photographic negative and a photosensitive material thereon, and a holding sheet which can be extended over and pressed towards said glass plate as it is unwound from a holding sheet winding roller eciprncable over the glass plate, the glass plate being supported at those opposite edge portions thereof which are parallel to the axes of said roller, so that deflections in the glass plate due to its weight are uniform between said edges.

In preferred forms of the invention there is a press roller adjacent and parallel to the holding sheet winding roller to press the holding sheet towards the glass plate as it is unwound.

Whether the holding sheet is used towards the glass plate by its winding roller or a separate press roller, the invention allows a simple cylindrical roller to be used and eliminates the need to have a central bulge in the roller concerned in order to follow the surface of the glass plate.

In order that the invention may be more clearly understood, the following description is given by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view of relevant parts of a contact printer embodying the present invention; Figure 2 is a sectional view taken along the line A-A in Fig. 1; and Figure 3 is a perspective view of a principal portion of the embodiment shown in Fig. 1 In a contact printer of the invention, a retainer frame 2 is fixedly mounted on a body 1 of the printer as shown in Fig. 1. The retainer frame 2 has a stepped portion 3 inwards of its outer edge as shown in Fig 2. A rectangular glass plate 5 Is set in the stepped portion 3 via a spacer 14.The spacer 14 is provided under those opposite edge portions of the glass plate 5 which are parallel to the axes of a holding sheet winding roller 10 and a press roller 11, both of which rollers 10, 1 1 will be described later.

The glass plate 5 used in this embodiment is 600 mm in length, 750 mm in width and 5 mm in thickness. The glass plate 5 is supported at its opposite edge portions 15, 15, which are parallel to the axes of winding roller 10 and press roller 11, via the spacers 14. If as shown in Fig. 3, spacers 14 are of about t mm In height the other two edges 16, 16 which are not supported deflect by t' at their centres due to the weight of the glass, so that the edges 1 6, 16 are arcuate and the glass plate 5 takes the form of part of a cylinder.

The glass plate 5 thus deflected by its own weight may be fastened with a metal member at some point along the edge portions 16, so as to be forced to maintain its cylindrical shape. The gap between the non-supported edges 16, 16 and the retainer frame 2 may be eliminated or filled with spacers of an appropriate thickness as the glass plate is kept deflected. In such a case, the glass plate 5 can be firmly held while the press roller 11 advances as it presses the glass plate 5. This allows a negative and a photosensitive material to be brought into contact with each other uniformly in an improved way.

A movable box 8, which is reciprocable by an endless chain 7, is provided above and straddling the glass plate 5, as shown in Figs.

1 and 2. The box 8 contains the roller 10 around which a holding sheet 9 is wound, and the press roller 11, the rollers 10, 11 being supported on parallel shafts. One end of the holding sheet 9 is fixed to a support member 18 and its other end is attached to the winding roller 10. The four upper edges of the glass plate 5 are covered with a soft, elastic frame 4.

Reference numeral 12 denotes a suction pipe leading to a vacuum pump and used to discharge air from between the holding sheet 9 and glass plate 5 The operation of the contact printer will now be described.

A photographic negative and a photosensitive material are placed one upon the other on the glass plate 5. When the endless chain 7 is then actuated, the movable box 8 advances.

As a result, the holding sheet 9 is gradually extended over the negative, the photosensitive material and the arcuately bent glass plate 5.

The press roller 11 immediately follows the roller 10 and presses the holding sheet 9 against the surface of the arcuately bent glass plate 5. As a result, the air between the negative and photosensitive material placed on the glass plate 5 is forced out ahead of the rollers.

When the box reaches its furthest position, the whole surface of the glass plate 5 is covered by the holding sheet 9, which is held against the glass plate 5 due to the sucking action of the suction pipe 12 so that the negative and photosensitive material are pressed against the glass plate 5. The photosensitive material is then subjected to exposure with light from a light source provided in the printer body 1.

The embodiment described above is provided with a press roller. A similar structure having no such press roller, i.e. a printer according to the present invention wherein a glass plate is pressed by a holder sheet winding roller alone has, of course, almost as good an effect.

With the invention, the holding sheet 9 can be brought into contact with the glass plate 5 more uniformly and with an improved tightness, allowing a negative to be brought into more close and uniform contact with a photosensitive material. The speed at which the holding sheet 9 can be brought into contact with the glass plate 5 can be increased. In a conventional contact printer, it takes four hour #.'.#r unit to adjust the contact condition between the holding sheet and glass plate. In a contact printer according to the present invention, substantially no such adjustment is required Moreover, when a press roller 11 is used, it is unnecessary that the roller be formed such as to have a central bulge.

The invention can be applied not only to a vacuum contact printer but also a contact printer with no vacuum suction means.

Claims

CLAIMS:

1. A contact printer having a printer body, a rectangular glass plate provided on the upper surface of said printer body and adapted to support a photographic negative and a photosensitive material thereon, and a holding sheet which can be extended over and pressed towards said glass plate as it is unwound from a holding sheet winding roller reciprocable over the glass plate, the glass plate being supported at those opposite edge portions thereof which are parallel to the axes of said roller, so that deflections in the glass plate due to its weight are uniform between said edges.

2. A contact printer according to claim 1 including a press roller adjacent and parallel to the holding sheet winding roller to press the holding sheet towards the glass plate as it is unwound.

3. A contact printer according to claim 1 or 2, wherein those opposite end portions of said glass plate which are parallel to said holding sheet winding roller are fixed to a retainer frame via spacers.

4. A contact printer according to any preceding claim including a vacuum connection between the glass plate and holding sheet.

5. A contact printer according to any preceding claim including means adjacent the other edges of the glass plate to prevent deflection thereof beyond deflection due to its own weight.

6. A contact printer substantially as herein before described with reference to and as illustrated in the accompanying drawings.