US3039390A - Printing cylinders - Google Patents

Description

June 19, 1962 w. HOTOP ET AL PRINTING CYLINDERS Filed Dec. 21, 1959 Jnvenfors mg United States Patent F 3,039,390 PRINTING CYLINDERS Werner Hotop, Heinz-Gunter Meese, and Erwin Masjoshusmann, Dortmund-Aplerbeck, Ulrich Biihle, Schwerte (Ruhr), and Giinter Ginzel, Dortmund-Aplerbeck, Germany, assignors to Deutsche Edelstahlwerke Aktiengesellschaft, Krefeld, Germany Filed Dec. 21, 1959, Ser. No. 861,146

Claims priority, application Germany Dec. 27, 1958 6 Claims. (Cl. 101-378) The present invention relates to improvements in printing cylinders as described and claimed in the specification of patent application Serial No. 779,949, dated December 12, 1958.

In the said specification a printing cylinder is described and claimed which comprises a support and an assembly of magnet elements forming the stereo-holding cylinder surface, the said elements comprising soft iron bars with plate-shaped magnets magnetized across their thickness applied, preferably adhesively secured, thereto. The elements are arranged in side-by-side adjacency around the axis of the support so that edges of the bars at the stereoholding surface present poles around the periphery which alternate in their polarity and each of which extends in the direction of the cylinder generatrix.

In order to ensure that the magnetizable stereo shall be securely held, as many poles as possible should be provided in close juxtaposition round the periphery. This brings about a distribution of the magnetic field in which the lines of force remain in the immediate vicinity of the cylinder surface so that they will then all pass through the relatively thin magnetizable layer of the stereo.

To enable such an assembly to be produced around the support, the support may be a cylindrical core shaped with appropriately profiled annular-guides for the correspondingly profiled bars and while magnetic printing cylinders so produced are successful, the cores are somewhat costly to produce in one piece.

According to the present invention, for the purpose of simplifying production and saving material, the support comprises a shaft having separate rings arranged around and secured to it and providing profiled guides adapted to permit the magnet elements, comprising the soft-iron bars and the attached permanent magnets, to be assembled successively around the rings and radially retained. The guides formed by the rings may be of dovetail section and preferably they are annular projections to co-operate with correspondingly contoured notches or grooves in the softiron bars. If then an appropriate gap is provided in the guides, the soft iron bars of the magnet elements appropriately selected for polarity may be successively registered with the guides and displaced round the rings about the axis of the shaft until a cylindrical assembly of the magnet elements with peripherally alternating poles has been produced and can serve as the printing cylinder.

Such a separate ring may be provided at each end and so contrived that rings may be shrunk on to the same which will radially hold the soft iron bars in a very tight grip.

In order to improve the rigidity of the cylinder the cavities between the magnet elements, the profiled rings, and the shaft, may then be spun out with a solidifying casting compound, such as a hardenable plastic or a low-melting alloy. It has been found that a cylinder thus constructed, although perhaps the cavities have not been centrifugally filled, is well capable of sustaining the stresses experienced during the printing process and can be economically and simply produced.

3,039,390 Patented June 19, 1962 A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which FIG. 1 is a longitudinal section, and

FIG. 2 is a section taken on the line AB in FIG. 1.

FIG. 3 is a fragmentary View.

As shown in FIG. 1 three rings 2 are pushed on to a shaft .1 and secured by means of taper keys 3. The two end rings have external extensions 4 which form the end faces of the cylinder. The peripheries of the rings 2 are formed with dovetail guide sections 5 on to which the soft iron bars 6 with permanent magnet plates 7 adhesively aflixed thereto are consecutively pushed after registering them with a suitable gap 5a in the guide sections 5. The soft magnetic bars with the attached permanent magnet plates are assembled together to a cylinder with the rings acting as supports in such a way that a sequence of poles of alternating polarity in the peripheral direction will appear. Rings 8 are shrunk on the extensions 4, the rims 9 of said shrunk rings retaining the soft iron bars 6 radially in a tight grip.

When additional rigidity is required, the cavities between the bars 6, the guide and retaining rings 2 and shaft 1 may be filled with a plastic or a low-melting metal.

The magnet elements shown are constructed as described in the specification of the aforesaid application No. 779,949 and a more detailed description thereof is therefore not given in this specification.

What we claim is:

1. A printing cylinder for supporting a magnetizable flexible stereo, comprising a support and an assembly of magnet elements, said elements comprising soft iron bars and plate-shaped permanent magnets magnetized across their thickness, certain of said magnet elements having the north pole of the magnet at the interface between the magnet and the soft iron bar and the remainder having the south pole at the said interface, said elements being alternately arranged in adjacency around the axis of the support so that the longitudinal edges of the said bars at the said stereo-holding surface present alternating poles in a cylindrical surface, means spacing said poles in said surface, said support comprising a shaft and a plurality of separate rings secured thereto, said rings having peripheral profiled ring guide means and the said elements having profiled sections co-operating with said guide means whereby the magnet elements have been guided round the ring guide means into assembled position and means permitting said elements to be brought into guidable relation to said peripheral ring guide means before movement therearound.

2. A printing cylinder according to claim 1, said separate rings including end rings, said end rings having axial extensions, and retaining rings shrunk onto the said extensions, the said retaining rings having rims which securely radially retain the magnet elements against outward displacement.

3. A printing cylinder according to claim 1, said guide means being formed by annular projections of the rings and of dove-tail cross-section and said magnet elements having co-operating dovetail notches, said projections providing a local gap for registering the magnet elements one by one with the said projections for assembly.

4. A printing cylinder according to claim 1, in which internal cavities are formed between the magnet elements, the said rings and the said shaft and a solidifying casting composition has been spun out in the said cavities and 3 has hardened to give additional rigidity to the assembly of magnet elements.

5. A printing cylinder according to claim 4 in which the said composition is a plastic.

6. A printing cylinder according to claim 4, in which the said composition is a metal alloy.

References Cited in the file of this patent UNITED STATES PATENTS 332,998 Coupland Dec. 22, 1885 4 Baker June 15, 1886 Condon et a1 Dec. 21, 1897 Price June 18, 1901 Trist Ian. 24, 1928 Trist July 4, 1933 Horst May 6, 1958 FOREIGN PATENTS Germany May 16, 1957

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