PH25974A

PH25974A - Device for fitting of stencil end rings on screen printing cylinders

Info

Publication number: PH25974A
Application number: PH33631A
Authority: PH
Inventors: Heinz Keller
Original assignee: Heinz Keller
Priority date: 1986-04-09
Filing date: 1986-04-09
Publication date: 1992-01-13

Description

DEVICE FOR FITTING OF STENCIL END RINGS ON SCREEN

FRINTING CYLINDERS

The invention relates to a device with which stencil end rings are inserted parallel at a pre- determined interval and in axial alignment into a cylinder jacket consisting of a nickel-plated chrome-steel cloth.

When using cylindricsl screen stencils for rotary screen printing, said screen stencils consisting of a metallization-stiffened cloth, the correct fitting of the stencil end ripgs into the cylinder jacket is of particular importance for the usability of a screen printing cylinder in high-speed rotary prin - ting presses, since not only does the rosition of the stencil end rings determine the length of the cylinder, but their axial alignment and parallelism also gua- i rantee the correct mounting of the cylinder and thus the rotationsl accuracy of the cylinder, which has only a limited inherent stiffness due to the metal- ligation of a steal-wire cloth, Attempts have there-~ fore been made to eliminate the disadvantages of the hand-fitting of stencil end rings and the limited - 3 a yar 25974 inherent stiffness and to prevent the associated warping of the cylinder jacket during printing by means of a fixed squeegee inside the cylinder such that the cylinders are held in ball joints that

Y catch the natural movements of the cylinder jacket in the mounting. Although these measures make it possible to perform large-area rotary screen printing, e.g. wallpapers, register accuracy cannot be achieved in this way. Furthermore, such mountings are elabo- rated and uneconomic, Known from DE-09 23 32 129 is a device for fitting stencil end rings into tube- shaped scresn stencils, with which the stencil end rings are inserted into an axial clamping device whersupon the enda of the tube-shaped screen stencil are secured on the stencil end rings with tube clamps and the thus formed screen printing cylinder is pre- clamped by means of the axial clamping device. To mount the screen printing cylinder, the latter ia installed in the screen printing unit with the axial clamping device and the axial clamping device is removed from the screen printing cylinder once the latter has been mounted in the printing unit. This device has the disadvantage thay, prior to each removal and each re-use, the screen printing cylinder must be ' oh.

- - yf § : . preclamped with the axial clamping device both for removal from the printing unit and prior to re-use. Firstly, this process is elaborate and, ~ secondly, it does not permit any absolute repeat- ability as regards register accuracy.

The object of the Snvention is to overcome the known disadvantages by meams of the absolutely ’ precise mounting of the end disks or stencil rings in terms of spacing, parallelism and axial align- ment, thus guaranteeing a method of mounting that permits torsion-free rotation of the screen prin- © ting cylinder, the latter being stiff only to a "limited extent. : The object of the invention is achieved by a device by means of which the atencil end rings “of screen printing cylinders made of metallized steel-wire cloth are semi-automatically inserted with abgolute repeatability into the cylinder jacket, are aligned and are inserted with a hot- setting adhesive into the cylinder Hacket in such ‘a way that, after the cooling and the associated shrinking of the screen printing cylinder, the co »

<7 25974 stencil end rings precisely determine the end disks of the cylinders as regard their parallel spacing, their parallelism and their axial alignment.

The device according to the invention consists of a heatable drying cabinet with closable doors, the floor of said drying cabinet accomodating a self-centering chuck for holding and aligning the lower stencil end ring, the back wall of said 106 drying cabinet accomodating, absolutely at right angles to the plane of the self-centering chuck, two guide rods, extending outside the cylinder, for holding, a fitting sled for the upper stencil end ring, said fitting mled being vertically sli- dable on the guide rods.

The fitting sled consists of a vacuum mounting for the upper stencil end ring which is absolutely parallel and axially aligned in relation to the plane of the self-centering chuck, said vacoum mounting being swivellable in relation to the axis of the screen printing cylinder.

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Further provided are means for automatic heating, ventilation and for the releasing of the vacuun mounting after the end of the drying stage of the stencil end ring gluing procesa, For the insertion, alignment and gluing of a screen printing oylinder jacket, the lower, glued stencil end ring is first of all clamped onto the self-centering chuck and the upper, glued stencil end ring is inserted into the vacuum mounting of the fitting sled, which serves merely to guide the stencil,

The reupon, the cylinder jacket is mounted onto : the lower stencil end ring, and, with the vacuum mount ing pivotted slightly out of the cylinder axis, the fitting sled is lowered onto the cylinder jac- ket in such a way that, with simultaneous pivotting into the cylinder, axis, the stencil and ring with its circomBerence is inserted conically into the cylinder jacket, The stencil end ring is lowered into the cylinder jacket merely by a distance corres- ponding to the residual height of the cylinder jacket prior to heating. Subsequently, the cabinet is closed and is heated at a predetermined temperature and for a prederternmined time,

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During heating, the cylinder jacket rises ahout the gacket of the stencil end ring due to the precalculated therral expansion until the cylinder jacket finishes with the upper edge of the stencil end ring. After the end of the precalculated setting time, the cabinet is ventilated and is cooled to room temperature. During this process, not only does the cylinder jackets shrink onto the stencil end rings, but the cylinder length also again decreases to the original length. Therdbre, simultaneously with the switching-off of the heating, the vacuum mounting of the upper stencil ring is ’ released, so that the occurrence of stresses or cracks in the cylinder jacket is preventad and the now ready screen printing cylinder can adjust at room temperature to the precalculated cylinder length.

With regard to the further explanation of the invention, reference in made to the specimen ambo- diment shown in the appended drawing.

Pig. 1 shows a diagrammatic representation of the device in an open side view,

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The device consists of a cabinet 1, which is provided at the front with closable doors and which is provided with a hot-air supply 2 and a ¢losable exhaust-air opening 3.

Disposed in the hot-air supply 2 is a thermostat (not shown), via which the temparature of the hot air, which, out of consideration for the light- sensitive coating of the cylinder Backet, must not exceed 60°C, is regulated at the hot-air source.

Disposed in the floor and in the back wall of the cabinet 1 is an absolutely rectangular mounting 4, ” made of a haavy-sheet-steel welied structure, for holding the self-centering chuck 5 and the guide rods 6 for guiding the fitting sled 7. The fitting sled 7 consists of a rod mounting 8 that is slidable and lockable on the guide rods 6 and of an upper mounting 10 that is slightly swivellable by means of a lever 11 in relation to the cylinder longitu- dinal axia 9, said upper rounting 10 being slightly swindable in alignment with the cylinder longitudinal axis (9) by means of lever (11) and housing a self- centering chuck (12), said gelf-centering chuck (12) being provided with a vacuum extractor (13), the axis of which aligns with the axis of the lowver-

159 7Y nelf-centering chuck 5. The cylinder jacket 16 with the end disks 14, 15 is held by the self- cent ering chuck S.

The device permits the fitting of the end disks in cylinder jackets of different lengths and of different diameters.

Claims

oo va Tf 25974 WHAT Is CLAIMED Is: 1 Device for fitting stencil end rings into a metallization-stiffened cylinder jacket, said cylinder Jacket consisting of a steel-wire cloth and the surface of said cylinder jacket being coated with a photosen- Ss sitive emulsion or solut ion, said device having two mountings to hold the stencil end rings in alignment with the cylinder axis, at least one of said stencil end rings being slidably and lockably guided, charac- terized by a drying cabinet tn, said drying cabinet (1) being closable with doors and having a temperature- controllable hot-air supply (3) and a controllable exhaust-air opaning (3) as well as a lower mounting (4), said lower mounting (4) being disposed in the floor and on the back wall of the drying cabinet (1), being absolutely rectangular, consisting of a sheet- steel welded structure and comprising a self-centering chuck (5), natd drying cabinet (1) further having a fitting sled (7), said fitting sled (7) being slidably and lockably guided on rectangular guide rods (6) extending to the floor outside the cylinder, said fitting sled (7) consisting of a rod mounting (8) and an upper mounting (10), said upper mounting (10) being slighly swivellable in alignment with the

¢ 25474 cylinder longitudinal axis (9) by means f a lever (11) and housing a self-centering chuck (12), said self-centering chuck (12) being provided with a vacuum extractor (13) and the axis of paid self- centering chuck (12) alighing with the axis of the lower nelf-centering chuck (5). Heinz Keller Inventor