US2774302A - Flexible printing plate - Google Patents

Description

Dec. 18, 1956 R. STRCJMME 2,774,302

FLEXIBLE PRINTING PLATE Filed June 8, 1954 INVENTOR. R's/1& STfib/VME United States Patent 7 2,774,302 7 FLEXIBLE PRINTING PLATE Reidar Striimme, Bestun, Oslo, Norway Application June 8, 1954, Serial No. 435,258

Claims priority, application Sweden June 15, 1953 4 Claims. (Cl. 101-378) The present invention relates to anattaching arrangement for flexible printing plates of the type which are used for instance for aniline printing or fiexographic printing.

The method commonly used in securing such printing plates, for example to a rotatable printing cylinder, consists in attaching the plate to said cylinder in a convenient way, for instance by glue or adhesive tape. To secure the printing plate in the required position, the printing cylinder is usually removed from the printing machine, and after disposing and attaching the printing plate, the cylinder is again mounted for a test run. Such printing cylinders generally are adjustable, but it still happens occasionally that the printing plate is wrongly positioned even if one is very careful in carrying out the said preparatory operation. In this event one has to carry out the whole process anew. This results in a considerable loss of work and time. It also happens occasionally that the printing plates after test printing have to be removed for adjustment. The glue used may itself involve disadvantages. Further, such printing plates often turn soft or are partly dissolved into alcohols or dyestufls so that the attachment is unreliable.

To overcome said drawbacks it has heretofore been proposed to provide the printing bed (the rotatable cylinder) with magnetic devices, the printing plate comprising a magnetic material for instance iron particles or the like. Such magnetically attached printing plates, however, have not had any practical employment, for they have suffered from disadvantages. They do not give a sufiicient adherence either between the magnetic material and the printing plate, or between the plate and the printing bed (the cylinder), to be held securely in position. One will readily understand that loosening of the printing plate when the printing machine is running results not only in destruction of the printing plate but may also damage the machine itself.

It is the object of the present invention to overcome the above-mentioned drawbacks incident to printing plates of the type which are attached to the printing bed by means of magnetic force. According to the invention the printing plate is held securely and conveniently in the required position by providing the back of the printing plate with a layer of magnetizable material in the form of rods, for instance of iron, so located side by side that they, when the printing plate is attached to the printing bed, lie across the magnetic poles of the bed as a continuous layer, so that the magnets grip the printing plates with maximum efiect.

According to a preferred embodiment the layer of iron rods is secured to one side of a textile sheet, to the other side of which the rubber printing plate is attached. The cross section dimensions of the iron rods are adapted so that they form a continuous layer of rods in such a way that when disposed around a printing cylinder they form a polygon having so many sides that it may be considered approximately a circle.

'To have a better understanding of the invention two 2 embodiments are shown in the enclosed drawing." The invention is, however, not limited to these embodiments which are given only as illustrative examples; further embodiments being of course conceivable for one skilled in the art within the scope of the invention.

Fig. 1 is a perspective view of a printing plate according to the invention, one comer being partly cut up.

Fig. 2 shows also in perspective a modified embodiment of the invention.

Fig. 3 shows the printing plate according to Fig. 1 disposed around a rotatable printing cylinder formed by permanent magnet sections.

The printing plate 1 according to Figs. 1 and 3 consists of rubber or similar material attached, for instance by gluing, to a textile sheet 2, preferably book-binding duck. To the opposite side of said sheet is glued a continuous layer of rods arranged side-by-side, such rods being of iron, for example. How the printing plate is built up appears clearly from the cut up corner in Fig. 1.

When a printing plate as shown in Fig. l is placed on a magnetic bed, for example the cylinder 10 in Fig. 3, the rods 4 are located across the poles 11 and 12 for the printing cylinder 10, which is built up from permanent magnet sections, whereby maximum gripping force is obtained for the printing plate I placed around the circumference of the cylinder 10.

Fig. 2 shows a somewhat modified embodiment. The printing plate 5 consists as usual of rubber or similar material. A magnetizable sheet (for instance of iron) is attached, by suitable gluing means, to the back of the plate. Said sheet is relatively thin so that it is flexible, and together with the printing plate constitutes a unit which may easily be attached around a rotatable printing cylinder of the type shown in Fig. 3. If required, the iron sheet 6 may be provided with parallel extending grooves or impressed weakening lines as indicated at 3 to facilitate the bending around the magnet cylinder.

The rubber printing plate itself could with advantage in some cases be glued directly to the layer of iron rods, i. e. without an intermediate sheet of textile material.

I claim:

1. Flexible printing plate means for attachment to a curved printing bed having magnetic means, said printing plate means comprising a flexible, non-magnetic printing plate in combination with a substantially continuous layer of elements of magnetizable material fastened to the rear face of the plate in such an arrangement that the printing plate retains its flexibility for disposal around a printing cylinder.

2. Flexible printing plate means for attachment to a curved printing bed having magnetic means, said printing plate means comprising a flexible, non-magnetic print ing plate and a layer of iron rods placed side by side and secured to the plate, said rods running parallel to the axis of the bed when the plate is disposed thereon and forming a substantially continuous layer of magnetizable material to coact with the magnetic means and yet allowing the plate to retain its flexibility in the dimension of the axis of the bed.

3. Flexible printing plate means according to claim 2 in which there is a sheet of flexible material to one side of which is secured the iron rod layer and to the other side the flexible printing plate, said plate being made of rubber. 1

4. Flexible printing plate means for attachment to a printing cylinder having magnetic means therein, comprising a flexible, non-magnetic printing plate and a layer of iron rods each substantially rectangular in cross section, of a breadth about double the height and placed side by side running parallel to the axis of the cylinder when the plate is disposed thereon, the olt sides of the rods being slightly rounded and the rods forming a substan-

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