CH304743A - High intensity light source contact printer. - Google Patents

Description

Contact printer with high intensity light source. The object of the present invention is a contact printer with a high intensity light source, in which the source constituted by a tubular lamp is arranged in a rotating, transparent copy cylinder, open at the ends, around which original res to be reproduced are intended to come into contact with sensitive elements.

This type of printer is intended to allow rapid obtaining of a proof by contact with a sensitized diazo element. A high-intensity mercury-vapour lamp or analogous discharge lamp is generally used to obtain a sufficient amount of mercury in a particular spectral range, in the violet and ultraviolet region of about n 3600 angstrom units. The capie cylinder is made of heat resistant glass. ehaleur. If no special cooling device is provided; the heat given off by the lamp enclosed in this cylinder would be excessive, and the wall of the cylinder with which the sensitive paper is intended to come into contact was too hot.

The problem to be solved by the builder of a cooling device for an apparatus of this nature is that the copy cylinder must operate at a temperature much cooler than that of the lamp. This, because of its necessary position in the cylinder, releases a very high quantity of heat and must not be cooled to a temperature lower than a fixed minimum value, to ensure satisfactory light output in the necessary spectrum range. On the other hand, this minimum temperature is much higher than that which the cylinder can reach to operate in satisfactory conditions.

To remedy the above-mentioned difficulties, it has already been proposed to completely enclose the lamp itself in a transparent glass tube resistant to heat and thus isolating the copy cylinder from the lamp. Air is then circulated through the glass tube and around the lamp, thereby cooling it to a safe temperature, while a separate mass of air cools the copy cylinder itself. -even at a satisfactory temperature as far as the sensitive paper is concerned. This form of construction is complicated and expensive and often results in excessive cooling of the lamp. In addition, the additional glass tube constitutes another obstacle to the passage of the light of phis short wavelength. It decreases Bone Pollution and also insulates the Lamp making it more difficult to clean. It has been found in practice that the small heat-resistant glass tubes decrease the radiation to the point of reducing the speed of copying by about 25 to 30%.

The object of the invention is to provide a cooling device which distributes the cooling so as to maintain the copying eye at the appropriate temperature and to allow the lamp to operate. </B> a higher temperature to obtain maximum htrznineu.x yield.

The printer, object of the invention, is characterized by a transparent screen, semi-cylindrical, placed between the Lamp and the copy cylinder and intended to ensure the cooling of the Lamp, this screen and the Lamp. being placed in front of a reflector; behind which is an air suction pipe, said screen being intended to deflect the heat between the lamp and the wall of the said cylinder and to distribute cooling on the lamp, without obstructing it. light thereof in the direction of said cylinder at least dans.ans a seeteur of the latter.

The appended drawing shows, by way of example, the lighting unit and the cooling device of one embodiment of the printer which is the subject of the invention.

fig. 1 in. is a perspective view with some elements cut away to reveal the shape of the interior construction.

fig. 2 is a cross section through the center of the group of FIG. 1.

A cylinder 10, of transparent heat resistant glass, is rotatably mounted at each end on rollers 11 or other suitable bearings shown schematically. This cylinder is mounted in the printer so as to rotate under the effect of several ribbons or belts which serve to guide and direct the sensitive paper and the original to be copied around the cylinder and in and out with it. The paper is impressed by the light emitted by a tubular mercury vapor lamp 12 disposed in the center of the cylinder and which passes through the cylinder.

Lamp 12 is supported at each end by devices not shown.

An elongated air pipe 13 with a flat front wall 14 and a curved back wall 15 is constructed to pass through the copy cylinder 10, to the side of its axis and more especially to the east of the opposite cylinder. to its exposure surface Over which the sensitive paper is passed. The pipe 13 is closed at both ends and extends beyond the cylinder at one end, which includes an exhaust manifold 16, to which a suitable flexible hose can be connected, joining it to a pump or other Fair suction device inside the pipe.

The pipe 13 is pierced, with a series of inlet orifices 17, arranged in the axis of the RTI ID="0002.0275" WI="9" HE="3" LX="1126"LY="588"> wall front wall 14 and a certain number of similar openings 18 arranged in the rear wall 15. These openings or holes are spaced along the length of the walls and serve to allow heat to : suction via the exhaust pipe 16.

A convex reflector 19 is fixed to the front wall 14 of the pipe and serves to reflect the radiation from the camp 12 towards the exposure surface of the copy cylinder 10 with which the sensitive paper and the original to be copied are in contact. This reflector is pierced with several holes 20 in the first extension of the orifices 17 and through which the heated air from the vicinity of the lamp 7.2 is sucked into the tliyali. 13.

A screen 21 extending along the entire length of the lamp 12 is held in place by arms 22 mounted on the reflector 19 at one arm at each end of the device. The screen 21 is semi-cylindrical and is made of transparent heat-resistant glass. 11 surrounds lamp 12 in an area of approximately 180 and deflects heat between the pump and the copy cylinder. Screen 21 passes below wool 12 and extends as far as the face adjacent to reflector 19 so as to completely cover the lower portion E of the lamp and prevent it from being damaged. - excessive cooling.

It will be noted that the upper part of the Lamp is not protected and that, consequently, the light can pass without obstacle in the intermediate space between the upper edge of Feeran 21 and the reflector 19.

While the printer is in operation, the vacuum created in pipe 13 causes air to enter both ends of copy cylinder 10 and air 9 passes through holes 17, 18 and 20. The cylindrical portion 15 of the wall of the pipe 13 is located at a very short distance from the rotating cylinder 10, so that a very violent current of air arises between the external face of this part 15 and the internal face of the cylinder 10. screen 21 absorbs such a quantity of the heat radiation from the lamp 12 that the rest of this radiation no longer exerts any significant influence on the cooling of the cylinder 10. The cooling air from the two ends of the cylinder passes around the lamp to enter through the holes 20 of the reflector and from there pax the holes 17 of the pipe. The air velocity in this circuit is much lower than through the 18 holes, but sufficient to cool the lamp to the necessary temperature. The most intense cooling occurs in the upper portion of the lamp 12, where the open space and the curvature of the screen create turbulence and a current from top to bottom under the effect of suction.

As for the light radiation from the lamp 12, the screen 21 only absorbs a small part of it and this radiation can be used almost entirely, thanks to the reflector 19 and the fact that the screen 21 does not surround there. lamp 12 in its upper part in fig. 2.

It has been found that the whole of the device described is very effective. While being housed in effect in a cylinder 10 of relatively small diameter, the lamp 12 can be brought to a relatively high temperature, so that its performance is the best, without the cylinder 10 overheating, at the point of damaging the elements covered with a diazo layer which pass in contact with the cylinder 10 with a view to making copies.

Of course, the copy cylinder 10 should be made relatively small in diameter, since the radiation from the lamp decreases in the usual proportion as the distance from the element to be copied increases.

When the cylinder and the lamp are very long; as in the case of large machines, the pipe may have exhaust pipes 16 at both ends and be constructed so as to draw in the air more uniformly throughout its length; the elements are thus cooled uniformly at all the points @and the presence of an excessive quantity of heat at the localized points is avoided.

The cooling device described makes it possible to reduce the temperature of the copying cylinder by about 11° C. more than hitherto, without exerting any influence on the luminous intensity and, consequently, on the speed of copy .of the printer. Another advantage of the construction shown lies in the accessibility of the device with a view to cleaning it, since it has been found that the accumulation of dust is likely to cause the light output to suffer a reduction reaching M 1%,.

Claims (4)

CLAIM: Printer by contact with a high intensity light source, in which the source constituted by a tubular lamp is arranged in a copying cylinder, rotating, transparent, open; at the ends, around which the originals to be reproduced are intended to come into contact with sensitive elements, characterized by a transparent, semi-eylindrical screen, arranged between the lamp and the copy cylinder and intended to ensure cooling of the lamp, this screen and the lamp being arranged in front of a reflector, behind which there is an air suction pipe,. said screen being intended to deflect the heat between the lamp and the wall of the said cylinder and to distribute the cooling air over the lamp, without obstructing the light thereof in the direction of the said cylinder at least for years a sector of this last. SUB-CLAIMS 1. Printer according to claim, characterized in that said reflector is convex. 2. Shooter according to sub-claim 1, characterized in that said reflector is carried by said air suction pipe, holes being drilled in the reflector and said suction pipe, as well as in the face of the turned pipe. to said cylinder. 3. Printer according to sub-claim 2, characterized in that the lamp is -a mercury vapor lamp, and in that said suction pipe comprises a flat wall adjacent to the reflector and a curved wall in the vicinity of the inner wall of said cylinder, said holes being drilled in these two walls of said pipe, those of said flat wall being located opposite those drilled in the reflector. 4. Printer according to sub-claim 3, characterized in that said screen is tramparent and in that its lower edge is in contact with the reflector.