US3432236A - Photoprinting apparatus - Google Patents

Description

March 1 1, 1969 J. c. A. VERCOULEN 3,432,236

PHOTOPRINTING APPARATUS Filed July 21, 1966 INVENTOR Jaw/mm (mm/s Awwr/M/J Vmcoamv BY W.

- ATTORNEY United States Patent 3,432,236 PHOTOPRINTING APPARATUS Johannes Cornelis Augustinus Vercoulen, Blerick, Netherlands, assignor to 'Chemische Fabriek L. van der Grinten N.V., Venlo, Netherlands, a corporation of Dutch law Filed July 21, 1966, Ser. No. 566,801 Claims priority, application Netherlands, July 23, 1965,

6509596 U.S. Cl. 355-109 Claims Int. Cl. G03b 27/12 ABSTRACT OF THE DISCLOSURE The invention relates to photoprinting by the use of apparatus of the type which comprises a rotatably driven exposure cylinder which is provided With a clamping device for holding the leading edge of an original to be copied and a driven belt system for pressing the nonheld part of the original together with a sheet of light-sensitive material against the wall of the cylinder during exposure. Apparatuses of this type generally function in a satisfactory manner when the original is copied once or only a few times. Usually the exposure cylinder is driven through contact With the belt system, if necessary via the original and the light-sensitive material situated in between, and thus with the same circumferential velocity as the belt system.

If in such an apparatus an original is rotated many times by the clamping device in order to make a larger number of copies, it is often found that the original is not taken along properly by the clamping device and that it becomes detached from the clamping device, in consequence of which the transport of the original naturally is seriously upset and the original is often damaged.

Naturally the detachment of the original can be obviated by increasing the force with which the clamping device holds the original. In practice, however, it is dilficult to realize this; as a rule the construction of a clamping device capable of supplying the desired forces occupies an impractically large space, with all the disadvantages involved, while there is a great risk that the cylinder may be damaged by the forces set up.

It has been found that the nature of the original to be copied largely determines the occurrence of the difiiculties described. Folded or somewhat wrinkled originals will become detached sooner from the clamping device than smooth, flat originals, whilst originals made of thin material (writing paper and the like) are not detached as readily as originals made of thicker material (photographic film and the like).

It is not quite clear to what factor the detachment of the original has to be imputed. However, the striking fact has been observed that the phenomenon can be prevented by providing that the velocity with which the belt system is driven is somewhat higher than the velocity with which the cylinder is driven. Preferably the velocity of movement of the belt system is 0.5-3% higher than the velocity of movement of the cylinder.

It is remarked that it is known to apply a much higher difference in speed between a glass cylinder without a clamping device and a driven belt system in photoprinting apparatus, in which the sheets are transported by friction between these parts, in order to smooth out dilferences in transparency and faults in the glass cylinder as appears from British patent specification 631,916. In this known apparatus the sheets move with the belt system and slide over the smooth glass cylinder.

The invention will now be described further with reference to the accompanying drawing, in which a photoprinting apparatus according to the invention is schematically illustrated in cross-section.

In this figure, 1 is the glass exposure cylinder of the apparatus, which is supported at its ends in a conventional manner in end plates so as to be freely rotatable. A tubular copying lamp 2, as well as a screen 3, which prevents undesirable radiation of light towards the operating side of the apparatus, are stationarily mounted inside the cylinder.

Stretched around the cylinder is a system of juxtaposed belts 4, which are also guided over a driving roller 8 and over rollers 5, 6, 7, which serve to guide and stretch the belts. At least one of these rollers, e.g., roller 7, is provided with disks 9, which extend between the belts 4 and which serve to guide the belts and to form slit-shaped interspaces between the belts.

The parts 2 and 3 and the rollers 5 to 8 are also supported in the said end plates in a usual manner.

A clamping device, known per se, which serves to hold the leading edge of an original to be copied, is attached to the cylinder 1. This clamping device comprises a shaft 10, which is rotatatbly supported in bearings (not shown) which are carried by the cylinder and to which are attached a number of mutually spaced clamps 11 and ejecting pins 12, which extend through openings in the cylinder wall. The members 11 and 12 respectively are at the same time situated in the region of the slit-shaped spaces between the belts 4, and they are dimensioned in such a way that they are able to extend through these spaces.

In a conventional manner the clamping device is normally kept closed with the aid of springs (not shown), which tend to press the clamps 11 against the wall of the cylinder 1. With other conventional means, e.g., by means of a cam and a plunger or by means of an electromagnet, the clamping device can be opened at the desired moments by turning the shaft 10 contrary to the action of the said springs.

The apparatus is further provided with a device, known per se, for feeding originals, which consists of guide plates 13 and 14 respectively, a rotatably supported shaft 15, to which stops 16 and a continuously rotating transport roller 17 are connected. An original to be copied O is placed between the plates 13 and 14 in such a way that its leading edge rests against the stops. When the shaft 15 is turned, the stops 16 swing away, while at the same time the rotating transport roller 17 seizes the original and sets it in motion. The apparatus is now controlled in such clamping device of cylinder 1, which at that moment, in the opened position, moves past the original-feeding mechanism, and that afterwards the clamping device is closed and the original starts rotating along with the cylinder.

Furthermore the apparatus comprises a conventional device for feeding sheets of light-sensitive material, which device consists of guide plates 18 and 19 respectively, a rotatably supported shaft 20, stops 21, and a rotating transport roller 22. This device is controlled in the same way as mentioned hereinbefore with regard to the original-feeding mechanism, so that with each revolution of cylinder 1 a light-sensitive copy sheet K is put on the original 0 between cylinder 1 and belts 4, with a view to making a copy.

After the exposure the copy sheet is sucked against the belts 4 by means of a suction 'box 23, so that it is detached from the cylinder and via a guiding plate 24 is guided away, e.g., to the developing unit of the apparatus.

When the desired number of copies of an original has thus been made, the clamping device is opened. The clamps 11 release the edge of the original, while the ejecting pins 12 separate the edge of the original from the cylinder wall and guide it over a guiding plate 25, along which the original is afterwards guided away, e.g., to a receiving trough.

All the parts such as guide plates, shafts 15 and and box 23 are mounted between the said end plates.

The belts 4 are driven by the driving roller 8, which is a way that the leading edge of the original gets into the coupled to the driving motor (not shown) of the apparatus. This motor is positioned at the outside of the apparatus, i.e., outside one of the end plates.

Outside one of the end plates, cylinder 1 is provided with a pulley unit, over which a belt 26 is guided, which is tensioned over a tension roller 27 and extends over a driving roller 28. Mounted on the roller 28 is a gear wheel 29, which co-operates with a .gear wheel mounted on the roller 8, and via these gear wheels, the roller 28, and the belt 2-6, the cylinder 1 is also coupled to the driving motor of the apparatus.

The diameters of therollers 8 and 28 respectively and the number of teeth of the gear wheels 29 and 30 respectively are so chosen that the required difference between the velocities with which the cylinder 1 and the belts 4 are driven is set up. The desired difference can of course be obtained in various ways. The driving rollers 8 and 28 respectively may have the same diameter and the gear wheels 29 and 30 respectively may have different numbers of teeth, the gear wheel 30 having slightly fewer teeth than the gear wheel 29. For example, gear wheel 30 may have fifty-nine teeth and gear wheel 29 sixty. The two gear wheels may also be equally large and the diameter of roller 8 be somewhat larger than that of roller 28. Preferably the diameter of the roller 8 is 0.5-3% larger than that of the roller 28 if the gear wheels 29 and 30 have the same number of teeth, and anyhow the diameters of rollers 8 and 28 and the numbers of teeth of gear wheels 29 and 30 are chosen so that the linear speed of the belt-s 4 is 0.5 to 3% higher than the peripheral speed of glass cylinder 1.

A very convenient form of the apparatus is obtained when a conventional rope pulley with a variable diameter is used for the roller 28. In such an embodiment it is very easy to realize the desired difference in velocity.

It will be clear, that in the cross-section shown in the drawing the gear wheels 29 and 30 and the belt 26 will in reality not be visible as they are positioned behind 4 i an end plate. For sake of simplicity, however, these parts are shown in full lines.

What I claim is:

1. Photoprinting apparatus comprising a rotatably driven exposure cylinder, which is provided with a clamping device for holding the leading edge of a sheet original to be copied and a driven belt system for pressing the nonheld part of the original together with sheet lightsensitive material against the wall of the cylinder during exposure, and means for driving the belt system at a speed slightly higher than the speed of the cylinder.

2. Apparatus according to claim 1, wherein the said means provide that the velocity of movement of the belt system is 0.5-3% higher than the velocity of movement of the cylinder.

3. Apparatus according to claim 1, said cylinder being driven by a nonslipping belt drive comprising a driven rotary pulley, said driving means comprising a rotary member engaging the belts of said belt system and means coupling said member with said pulley for rotation therewith at a relative speed advancing said belts slightly faster than said cylinder surface.

4. In a process of exposing photoprint materials by laying a light-sensitive sheet upon an original sheet having its leading edge gripped to a rotating exposure cylinder and carrying said sheets together on the surface of said cylinder through an exposure zone while pressing them against said surface by a system of belts wrapped against and moving in the same direction as said surface, the improvement which comprises driving said cylinder at a speed desired for exposure of said sheets in said zone and driving said belts at a speed slightly higher than the speed of movement of said surface, to avoid detachment of the original sheet from the cylinder.

5. A process according to claim 4, the speed of said belts being 0.5 to 3% higher than the speed of said surface.

References Cited UNITED STATES PATENTS 2,048,754 7/1936 Putnam 226-171 2,297,573 9/1942 MacDonald et a1. 77.5 3,033,095 5/1962 Limberger 95--77.5 3,199,864 8/1965 Irvine 27151 NORTON ANSHER, Primary Examiner.

CHARLES B. FUNK, Assistant Examiner.

US. Cl. X.R. 27l5l; 355-

Images