US2690106A - Printing lamp and cylinder cooling means - Google Patents

Description

Sept. 28, 1954 F. o. TRUMP 2,690,106 PRINTING LAMP AND CYLINDER COOLING MEANS Filed April 11, 1951 INVENTOR Frederick O. Trump ATTORNEYS Patented Sept. 28, 1954 UNITED STATES ATENT OFFICE PRINTING LAMP AND CYLINDER COOLING Frederick 0. Trump,

MEANS Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Claims.

vapor lamps.

This application is a continuation-in-part of my application Serial No. 13,995, filed March 10, 1948, for Printin Lamp and Cylinder Cooling Means, now abandoned.

The type of contact printing apparatus to which this invention is particularly directed produces rapid photo-contact prints on diazo sensitized material which requires a high intensity mercury vapor, a similar discharge heat generated by the lamp confined in this cylinder is excessive for its safe operation as well as for the temperature of the cylinder wall which printing cylinder must be operated at a much lower temperature than the lamp. The latter, by its necessary physical placement in the cylinder, generates an intense heat and must not be cooled below a certain minimum temperature for efficient light rendition in the required spectrum. This minimum temperature, on the other hand, is far in excess to that which the printing cylinder may have for satisfactory operation.

In order to overcome the above difficulties, it has been the practice to completely enclose the lamp itself in a transparent heat resistant glass tube, thereby isolating the printing cylinder from the lamp. Then, air is circulated within the glass tube and about the lamp, thereby to cool it printing cylinder itself to a temperature which is safe insofar as the sensitized material. is concerned. This construction is cumbersome and costly, and often results in overlengths of light. Therefore, it reduces the illumination, and also isolates the lamp, making it printing speed approximately 25-30%.

The object of this invention is to provide a 2 cooling arrangement for such light assemblies which will distribute the cooling air in such manner as to maintain the printing cylinder at the proper temperature and permit operation of the lamp at higher temperatures for maximum light efiiciency.

A particular feature of the invention is that the efiiciency of the printing apparatus is considerably increased by permitting unobstructed passage of light between the lamp and an active exposure surface of the cylinder, although the cylinder is effectively heat shielded from the lamp.

Other objects and features will be apparent from the following description of the invention, defined in particularity in the appended claims, and taken in connection with the accompanying drawing, in which:

Figure l is a perspective view of the light assembly, certain parts being cut away to show the interior of the construction;

Figure 2 is a transverse section taken through the center of the assembly illustrated in Figure 1.

In accordance with the invention, a heat resistof the cylinder. interior of the The duct maintained under a fairly high vacuum is provided with a series of apertures, some of which draw air from the vicinity of the lamp and its deflector shield, while other aperturesin the duct draw air from the interior surface of the printing cylinder, so that a differential temperature is created between these surfaces, although the lamp itself is not isolated.

use of this printin light assembly,

sible to reduce the temperature of the printing F. more than herelight intensity and accumulation of dust may reduce light output by as much as 30%.

Now referring to the figures, a cylinder 10, generally made of a heat resistant transparent glass, is rotatably mounted at each end on rollers l I or other suitable bearings, schematically shown here. This cylinder is so mounted inthe printing apparatus as to be rotated by a plurality of tapes or belts which serve to guide and direct the sensitized material and the original to be printed about and in contact with the cylinder. The sensitized material is printed by the action of light passing through the cylinder and emitted from a centrally disposed tubular mercury vapor lamp l2.

The lamp l2 may be supported at each end by means not illustrated in detail here, but shown in U. S. Patent 2,308,130.

An elongated air duct l3, having a flat front wall It and a curved rear wall I5, is constructed in such manner that it extends within the printing cylinder i0, being positioned to one side from the center line, .more specifically, at the side of the cylinder opposite to the exposure surface about which the sensitized material is passed. The duct I3 is closed at both ends and extends beyond the cylinder at one end which has an exhaust outlet Hi, to which may be attached a suitable flexible tube connecting the outlet IE to a pump or other device adapted to exhaust air from its interior.

I The duct 13 has a series of air inlet openings ll, centrally located in the front wall [4, and a number of similar openings l8 disposed in the rear wall 15. These openings, or apertures, are spaced along the length of the walls and serve to admit the heated air adjacent thereto, so that it may be drawn out by the suction through the outlet 1.6.

A convex reflector I9 is attached to the front wall M of the duct and serves to reflect radiation from the lamp l2 toward the exposure surface of the printing cylinder ill with which the sensitized material and the original to be printed are in contact. This reflector also has a plurality of apertures 20 in alignment with the series of openings l1, through which heated air from the vicinity of the lamp I2 is drawn into the duct I3.

A shield 2| extending along the length of the lamp I2 is held in position by brackets 22 mounted on the reflector l9, one of which is positioned at either end of the assembly. The shield 2i is semicylindrical and made of heat resistant transparent glass. It surrounds the lamp l2 in an arc of approximately 180, and forms a heat deflector between the lamp and the printing cylinder. The shield 2| passes beneath the lamp l2 and extends to the adjacent face of the reflector l9, so as to completely cover the lower portion of the lamp and thereby prevent overcooling thereof.

It is to be noted that the top of the lamp is not shielded so that an unobstructed passage of light is provided in the space intervening between the top edge of the shield and the reflector l9.

In operation, the vacuum created within the duct l3 causes air to enter at both ends of the printing cylinder I0, and pass through the openings l1, l8 and 20. The curved wall l of the duct I3 is close to the inner wall of the rotating cylinder l0, and a high velocity strong air current is created over this surface. Heat radiation from the lamp l2, by virtue of the shield 2!, is sufficiently restricted and will not affect the cooling of the rotating cylinder [0. The cooling air from both ends of the cylinder finds passage around the lamp to enter the openings 20 in the reflector and from there the openings 11 in the duct. The velocity of the air over this passage is far lower than through openings [8, but suflicient to cool the lamp to the required temperature. The cooling is chiefly over the top portion of the lamp l2 where the open space and the curvature of the shield produces turbulence and a down draft due to the suction.

A small portion of the radiation emitted is absorbed by the shield 2|, however, the appreciable space at the top of the lamp supplemented by the reflector l9 permits relatively efiective use of the total illumination from the lamp.

The entire combination has been found to be very effective, since, by this means, the lamp may be operated at its most efllcient temperature, and, at the same time, it can be enclosed in a relatively small printing cylinder operated at a temperature low enough to permit the printing of all diazocoated materials without damage to the coating thereof. Of course, it is desirable to keep the printing cylinder Ill down to a relatively small diameter since the radiation from the lamp falls off in the usual proportion as the distance to the material to be printed is increased.

In the description, certain angular extents of parts have been referred to by way of example. It is to be understood that reasonable variation in the proportions and in the angular extent to which the shield surrounds the lamp may be made without departing from the inventive concept and without altering the general effectiveness of the combination itself. The actual shape of parts, for example, the curvature of the reflector, the actual design of the suction duct and the number and size of apertures through which the heated air is drawn into the duct may all be altered within limits depending upon the size of the printing cylinder, the actual size and design of the lamp itself, and other pertinent factors. In the event the cylinder and lamp are of extreme length, as in larger machines, the duct may preferably be provided with outlet connections It at both ends and may be designed in such manner as to draw in the heated air more evenly along its entire length, thereby to cool the parts equally at all points and to avoid excessive heat in the cylinder at its localized areas.

I claim:

1. Cooling arrangement for printing light assembly for contact printing apparatus of the type utilizing a transparent open ended rotating printing cylinder about which the sensitized material in contact with the original is passed and exposed including a tubular high intensity lamp axially disposed within said cylinder; comprising, at one side from said lamp, a reflector having a plurality of air intake openings extending adjacent said lamp, an elongated air duct behind said reflector closed at both ends, an exhaust outlet therefor, said duct having in one side a plurality of air intake openings in alignment with said intake openings in said reflector, and in the opposite side intake openings facing the inner wall of said cylinder, and at the other side from said lamp a transparent semicylindrical shield extending along the length of said lamp, said shield forming a heat deflector between said lamp and the cylinder wall and providing distribution of cooling air over said lamp while permitting unobstructed passage of light between said lamp and an active exposure surface of said cylinder.

2. Cooling arrangement for printing light aswithin said cylinder; comprising, at one side from said lamp, a reflector having a plurality of air intake openings extending adjacent said lamp, an elongated air duct behind said reflector closed at both ends, an exhaust outlet therefor, said duct having in one side a plurality of air intake openings in alignment with said intake openings in said reflector, and in the opposite side intake openings facing the inner wall of said cylinder, and at the other side from said lamp a transparent semicylindrical shield extending along the length of said lamp, said shield forming a heat deflector between said lamp and the print exposure wall of said cylinder and proa portion of the active exposure surface of said cylinder.

3. Cooling arrangement for printing light assembly for contact printing apparatus of the type utilizing a transparent open ended rotating printing cylinder about which the sensitized material in contact with the original is passed and exposed including a tubular high intensity lamp axially disposed within said cylinder; comprising, at one side from said lamp, a convex reflector having a plurality of air intake openings extending adjacent said lamp, an elongated air duct behind said reflector and forming a support thereof, said duct being closed at both ends, an exhaust outlet therehaving in one side a plurality of air intake openings in alignment with said intake said reflector, and in the opposite side intake openings facing the inner wall of said cylinder, whereby suction through said openings removes the heated air near said lamp and at the other side from said lamp said cylinder wall, and a transparent semicylindrical shield extending along the length of said lamp, said shield forming a heat deflector between said lamp and the print exposure wall of said cylinder and providing distribution of cooling air over said lamp while permitting unobstructed passage of light between said lamp and a portion of the active exposure surface of said cylinder.

4. Cooling arrangement for printing light assembly for contact printing apparatus of the type utilizing a transparent open ended rotating printing cylinder about which the sensitized material in contact with the original is passed and exposed including a tubular high intensity mercury vapor lamp axially disposed within said cylinder; comprising, at one side from said lamp, a convex reflector having a plurality of air intake openings extending adjacent said lamp, an elongated air duct having a flat wall adjacent said reflector and forming a support thereof, and having a curved wall adjacent the inner wall of said cylinder, said duct being closed at both ends, an exhaust outlet therefor, said flat wall having a plurality of air intake openings in alignment with original is passed and exposed high intensity mercury vapor lamp axially disposed within said cylinder; comprising, at one side from said lamp, a convex reflector having a plurality of air intake openings extending adjacent said lamp, an elongated air duct having a flat wall adjacent said reflector and having intake openings distributed over its surface, and at the other side from said lamp a transparent semicylindrical glass shield partially surrounding said lamp, the bottom edge of said shield engaging said reflector, said shield forming a heat deflector between said lamp and the print exposure wall of said cylinder and providing distribuof said Cylinder.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,279,084 Tillyer Apr. 7, 1942 2,308,130 Von Meister et al. Jan. 12, 1943 2,431,520 Streich Nov. 25, 1947

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