US2357476A - Means for manufacturing printing forms - Google Patents

Description

Sept. 5, 1944. R KAULEN 2,357,476

MEANS FOR MANUFACTURING PRINTING FORMS Original Filed June 3. 1937 Patented Sept. 5, 1944 UNITED. STATES PATENT oFFlcs assure P Robert Kaulen, Loevenich-Cologne, Germany, as-

signor to the firm Switzerland of Eden A. G., Zing-Zurich,

4 Claims.

This invention is a division from U. S. application Serial No. 146,228 flied June 3, 1937, and relates to a device for coating bodies of substantially cylindrical shape, and is more particularly concerned with means for uniformly coating printing cylinders with a light-sensitive colloidal coating.

In order to obtain faultless prints, it is important that a thin sensitive coating be uniformly and evenly spread over the face of the printing roller around its entire circumference.

'It is a diflicult task to apply such an "endless coating upon the surface of a cylinder, and it is an object of the invention to provide a device which enables the operator to fulfill this task without failure. It is a further object of the invention to provide for this purpose a device of relatively simple structure.

Further objects of the invention will be apparent from the detailed description of the invention. Devices of the kind in question usually comprise a container which holds the coating fluid, and supporting means for the cylinder which is to be provided with the coating. Ac-

cording to the invention, the container is provided at the top with a narrow opening through which only a narrow area of the cylinder contacts at a time with the coating fluid. Spreading of the fluid over the whole circumference of the cylinder is then achieved by rotating the cylinder. The supporting means therefore cooperate with means for rotating the cylinder around its axis, the cylinder being supported with its axis extending in horizontal direction while the coating takes place. The rotating means may be adjusted so asto effect 'slow rotation of the cylinder. Preferably the container has the shape of a channel, i. e. the container is a narrow box the upper side of which is open.

In order to avoid creeping of the fluid, it is advisable to provide the side walls of the container with inclined upper faces, 1. e. the upper faces bordering the opening of the container may slope downwardly and outwardly.

The container with the liquid bath and the supporting means are so arranged relative to each other that the cylinder only just touches th surface of the bath while the coating takes place. Contact of the cylinder face with the surface of the liquid may be established by any suitable means. Preferably, means are provided for raising and lowering the bath into and out of contact with the cylinder. Such means may consist of a device of any well-known suitable structure for lifting and lowering the container,

' within the container.

In order to ensure proper contact of thliquid with the roller, it is advisable to provide for a compensating reservoir which communicates 'with the container in such a manner that the latter is always kept fllled.

The formation of the coating on the cylinder may be improved by holding the cylinder and the fluid at about the same elevated temperature while the coating takes place. The device according to the invention may therefore be equipped with suitable means for heating or preheating the cylinder as ell as the fluid, and with temperature-contro iing apparatus. Heating means and controlling apparatus of any well-known suitable structure ay be used for this purpose.

As already stated, the rotating means should cause very slow rotation of the cylinder, this being of particular importance for attaining a perfectly uniform coating. The speed of rotation should be so chosen that a single rotation requires several minutes, preferably about five minutes.

The enclosed drawings illustrate by way of example one embodiment of the invention which, however, is not limited to the details shown in that embodiment.

Fig. 1 shows schematically a vertical section through a coating device according to the invention.

Fig. 2 is a plan view, with parts in section, and parts broken away, of the coating bath container and associated means.

Fig. 3 is a fragmentary sectional elevational view showing the apparatus in coating position.

The device schematically illustrated in Figs. 1 and 2, enables to provide printing cylinders with a substantially uniform coating, with th only exception, if any, of a narrow border line where the coating may perhaps become a little thicker than on the other area. At the same time, this device makesit possible to keep the coating free from dust, without requiring encumbering space. For attaining this purpose, the cylinder is not dipped to any substantial extent into the fluid, but it is rotated only along the top opening of the container filled with the fluid in such a way that its surface is just touching the surface of the coating fluid and the fluid is preferably drawn out of a channel-shaped or groove-like container by way of adhesion of the fluid to the revolving cylindenor by the action' of the surface tension of the fluid. Separation of the cylinder and the bulk of the coating fluid can be effected very uneven streak whatever will be formed on -the cylinder. In order to still further restrict formation of an uneven streak of separation on the cylinder, the opening at the top of the fluid container may be rather narrow, while its length should at least correspond to the length of the cylinder which is to be coated.

Since only a rather narrow part of the surface of the coating fluid is left free, and since furthermore this part is still to some extent protected by the cylinder arranged above it, there is very little danger of dust getting on to the surface of the coating liquid. Additional protective means may be provided such as wipers arranged in front of the coating channel or groove, which glide on the cylinder surface, thoroughly removing any dust from the surface as the cylinder revolves, whilst behind the coating channel a protecting plate may be fixed which prevents access of dust to the freshly coated area of the cylinder.

As shown in Fig. 1, the cylinder I to be coated has its axial trunnions la adapted to be mounted on bearings, preferably in the form of rollers lb, carried by a suitable supporting structure lc. Means such as the motor driven belt and pulley mechanism Id, le are provided for rotating cylinder l. Vertically beneath the cylinder l to be coated, a groove or channel 2 is arranged which is open at the top and extends over the entire length of the cylinder I. If desired, a cover 2 may be provided for closing the top opening when the device is at rest. The bottom part oi. the channel 2 is connected to a compensating reservoir of conveniently the same horizontal length as the channel 2 (see Fig. 2), communicating tubes 4 connecting reservoir 5 and container 2. Tubes 8 (Fig. 2) feed the colloidal fluid to the compensating reservoir I from a tank not shown. The interior of the compensating reservoir 5 which may be closed by a detachable cover "I,'is provided with a number of overflow tubings I, the tops ofwhich are exactly on the same level with the upper opening or brim of the channel 2. Thus channel 2 will remain permanently filled up to the brim as long as suflicient fluid is fed from the tank to reservoir 5.

As may be seen from Fig. 1, the top border of the channel 2 is bevelled on either side, as shown at 9. This willprevent any liquid from collecting on these edges, which liquid otherwise might come into contact with the cylinder and might cause unevenness of the coating. The said bevels need, however, not reach the inner edges of the channel.

Suitable means for bringing the cylinder in and out of contact with the surface of the liquid bath filling container 2, may be provided,

a as well as means for regulating the temperature of the bath and of the cylinder respectively. According to the embodiment shown in the drawings, the apparatus consisting of the coat-' 1 paratus supported'by it may be raised or lowered towardor swayfrom cylinder l bymean'sof ther'ackandpinionmeans llb, lie.

stat not shown. The liquid drains of! through is In front of the groove 2, leather-wipers II, II are arranged which extend over the whole length of the cylinder. In the embodiment shown in Figa. 1 and 2; these wipers II, II are fitted to rods l'l, ILfixed to a joint or hinge II, which is connected to a counter-weight 20. Instead of the counter-weight, obviously also springs may be employed.

At the opposite side of the channel 2 and adiacent casing ll, a wall 2| is arranged which suitably extends up to cylinder I, as shown in Fig. 1, thus closing off the space between the cylinder and easing II and acting as a dustguard. Wall 2| may be hinged at 23, and may be detachably fixed to casing II by means of thumb screws 22. 1

If desired, the wipers It, I. may be replaced by a second corresponding wall protecting against dust, or such a wall may be arranged alongside the wipers l5, I.

For using this device, the casing I0 is first filled with water or with any other suitable liquid having the desired uniform temperature, and also the compensating reservoir 5 is filled with the coating fluid. The latter passes from reservoir 5 through the tubes 4 to the coating channel 2 and fills it up to the brim, the level of which corresponds to the top of the overflow tubes -8. Till this moment the cover 3 of the coating channel 2 may be kept closed. When the cover is removed, either the cylinder l, which, if desired, may be preheated by suitable means, including a thermostatically controlled current of warm water fed through the cylinder from warm water pipe lia, is lowered down towards the brim of channel 2, or the latter is raised towards the cylinder together with casing l0, e. g. by means of the adjusting screws l2, until the surface of the fluid in channel 2 comes into contact with the cylinder as indicated in Fig. 3. The slowly revolving cylinder l takes up the coating fluid from the groove 2 in consequence of the adhesion or surface tension of said fluid, and the cylinder is thus evenly coated, whilst from the not shown reservoir a corresponding quantity of coating fluid flows into the com-. pensating reservoir 5.

In most cases coating is completed after one complete revolution of the cylinder in contact with the bath of liquid has taken place. Separating means (not shown) of any convenient structure then cause separation of the cylinder surface and the surface of the bath, for instance by lowering channel 2.

Usually the bath consists of a photosensitive solution such as a solution of bichromated gelatine. However, other coatings such as a varnish or lacquer, may be applied by means of the same device.

I claim:

1. A device for uniformly coating bodies of substantially cylindrical shape with a sensitive layer for the manufacture of printing forms, comprising a container provided at the top with an elongated narrow opening and adapted to be filled with liquid for forming a sensitive layer, the upper faces of the side walls of the container bordering the narrow opening sloping downwardly and outwardly, means for rotatably S pporting the body to be coated above said container and in vertical alignment with said stationary means for rotatably supporting the body to be coated above said container and in vertical alignment with said narrow opening, means for raising and lowering said container whereby to bring a linear portion of the peripheral surface of said body into liquid-contacting relationship with respect to said narrow opening without dipping into the liquid to any substantial amount, and means for rotating said body.

3. A device for uniformly coating cylinders with a light-sensitive layer for the manufacture of printing forms, comprising a container containing a bath of a light-sensitive colloidal fluid,

said container having the shape of a narrow.

channel and the upper faces of the side walls of the channel being inclined in downward and" outward direction; means for rotatably supporting the cylinder to be coated above said channel, the axis of the cylinder extending in horizontal direction and the said supporting means being arranged in such a manner that the said cylinder during the coating step only just touches the surface of the said bath; means for rotating said cylinder while the coating takes place, wipers cooperating with the face of the cylinder for removing dust therefrom, said wipers being arranged to resiliently lcontact said face along substantially its whole length and shortly before the respective portion of the face touches the surface of the fluid bath, and means for separating said cylinder face from said surface of the bath after the coating has taken place.

4. A device for uniformly coating printing cylinders with a photo sensitive layer, comprising a narrow, open container filled up to the brim with a bath of a solution of bichromated gelatine, means for rotatably supporting the cylinder to be coated above said container, means for heating said cylinder, means for heating said bath, means for lowering and raising said container and the bath, whereby a narrow area of the face of the cylinder can contact the surface of the bath, and means for rotating said cylinder.

ROBERT KAULEN.

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