US1540196A - Press for producing multicolored prints from copper cylinders - Google Patents

Description

n June 2,

F. O. V. TRAITTEUR PRESS FORPRODUCING MULTICOLORED PRINTS FROM COPPER CYLINDERS Filed March 12. 1925 Patented .lune 2, 1925A.

UNITED STATES 1,540,196 PATENT caricia.I

FRIEDRICH O. V. il*Iii-AIWDE'U'R, 0F FRANKENTHAL, GERMANY.

PRESS QEOR PRODUCING MULTICOLORED PRINTS FROM COPPER CYLINDERS.

Application filed March 12, @25. Serial No. 15,154.

ders of copper or steel drums covered with layers of copper are employed as form cylinders, which layer is connected at the edges. The characters or the image to be printed are etched in the copper-drum. The etched image must be entirely rubbed away before a new etching can be produced on the said drum. By this repeated rubbing of the drum the diameter thereof is somewhat reduced at each operation. Besides this, rubbing is not uniformly done for each copper drum, but in different degree according to the depth of the etching. Therefore, the

' copper-drums will develop slight differences Ain their diameters, which necessitate in consequence of the dillerent lengths of their peripheries a non-uniform travel of the endless web of paper in cases where several colors are to be printed successively on an endless strip or web of paper, the result being an imperfect imposition of the several colors and oftentimes a tearing of the web.

The same result will be produced when copper sheets are stretched on the form-cylinders, even if supporting layers for the copper sheets are employed.

In case the form-cylinders for multi-color printing are arranged around a common printing drum and the latter serves as an impression cylinder for each form-cylinder, all form-cylinders must have the same length of periphery, because the circumferential s eed for every form-cylinder is prescribed Iby the impression cylinder.

On the other hand it is very difficult or Learl impossible to give each form-cylin-v der tie same diameter on account of the above mentioned rubbing of the copper layer.

Besides, the drying of each printed color `.occasions great difliculties, as the form-cyli-I'iders nearly touch each other, and the rubber covering of the printing cylinder orof the intermediate cylinderssuffers very much from the heat introduced for drying purA poses.

curate work cannot be obtained, or

If on the other hand the form-cylinders are arranged at greater distances from each other,'it is difficult to obtain a satisfactory registration of the imprints as the paper strip is stretched between the individual form-cylinders. The reasons therefor are of different natures. If, between the formcylinders, drying devices are provided, the

paper is altered in its structure by the iniiuence of the heat. The paper is also differently infiuenced -by the heat at various speeds of the printing press so that the paper is more or less altered.. A non-uniform heating or a variable degree of humidity will also unfavorably influence the regable to fully equalize the alterations produced by theA heat. Under some circumstances moisture may be condensed or deposited on the paper strip, which results in a quite uneven stretching yof the paper.

-Rolls lof paper which are stood up on end in a. storage room may easily become moist at their lower ends while their upper ends remain dry, so that the length of one edge thus becomes less than the other, due to istration, even a subsequent cooling is not y shrinkage, Wherefrom lateral displacement of the paper results, so that the registeringl isbadly influenced. It is therefore, obvious, that in multi-color printing on a Web, which is cut into several sheets after printing, alcon y with great difficulty.

The last mentioned disadvantages are of no importance'whatever, so far' as simple printing in one color comes into question; but the situation is immediately changed, if a print in multiple colors is to be produced, because the different individual colors demand accurate imposition if they are successively printed on the paper.

,Besides, the slight differences in the diameters of the form-cylinders will cause further inconveniences.

For the purpose of obviating all these difficulties the paper fed from, the paper roller is cut into sheets before printin and carried from one form-cylinder to anot ier by transfer elements, seizing and holding the paper sheet by means of grippers or by equivalent devices. The sheets may be carried several times around such transfer elements before;

they are delivered to the next form-cylinder and may serve therefore, at ..theSarriesusv iio

view of a press for printing in three colors is represented by way of example in which: Figure 1 shows a machine for printing on one side only and Figure@ a machine for printing on both sides.

The paper Z2 drawn oit from the roller a is passed through a cutting-'device c and divided into sheets d of a predetermined size. The sheet is delivered to the first impression cylinder 7L by a sheet-transfer device of any suitable kind. A. gripping device g arranged in the impression cylinder grasps the sheet of paper and carries it between the impression cylinder it and the form-cylinder z' for the iirst impression. Thereafter the sheet is grasped by one of the gripping devices Z, man, 0 and p in 'the transfer-cylinder g and delivered to the next following impression cylinder h1, where the sheet receives the second impression. Thereupon the sheet is grasped by a gripping device in the next transfer cylinder g and delivered to the next impression cylinder h2, where it receives the third impression. From the impression cylinder h2 the sheet is delivered to the transfer cylinder g2l and thence to a cylinder g3 which deposits the iinished sheet upon the delivery-table s or delivers it to any other suitable device, for instance to a folding or slip sheeting device. The cylinders serving -for the transfer of the sheet from one impression cylinder to the next one may be arranged for the reception of one or more sheets and likewise for any convenient number of sheets. In cases where the sheet is to be conveyed several times around the transfer-cylinder, before it is delivered to the next impression cylinder, the dimensions of the transfencylinder must be calculated in such a manner that the transfer cylinder is able toreceive a sheet more or less than a multiple of the number of sheets covering the surface of the impression cylinder. f course each sheet may, according to the dimensions of the impression cylinder, remain for a shorter or longer period of time as necessary for one revolution on the transfer-cylinder.

In the press shown in the drawing, the several 'transfer cylinders are each designed to receive live sheets, and the diameter of each is slightly greater than twice ,that of the associated impression cylinder, so that the length of the sheet of greatest size corresponds to slightly more than half the circumference of the impression cylinder. Each transfer cylinder is therefore provided witli five grippers or the like of suitable character, `which are spaced apart a distance corresponding to the greatest length of the sheet plus the space necessary for the grippers and their operating appliances.

In operation, and referring, for example, to the lirst impression cylinder 7L and its associated transfer cylinder g in Fig. l, the

essere@ grippers p, n and Z in the latter cylinder will each receive one sheet from the gripper g of the impression cylinder during the first revolution of the transfer cylinder. The intermediate grippers 0 land m in the transfer cylinder, hoiwever, will not pick up sheets from the impression cylinder during that revolution because of the fact that the sheets on the said impression cylinder will not be in position for engagement by those grippers when the latter pass them. But dnring the second revolution of the transfer cylinder, the grippers 0 and m will each remove a sheet from the impression cylinder, while the sheets previously removed by the grippers p, Z and n ill be transferred to the second impressio cylinder it, and so on. Consequently, it is possible in this way to obtain a longer period for drying the individual sheets, or the colors printed thereon, between the individual impression cylinders, as the sheets travel around with the impression cylinders for more than a complete revolution, instead of being immediately transferred from one impression cylinder to the next. The drying operation may be assisted and carried out to a further extent, moreover, by providing the transfer cylinders with hot air blowers or other devices yfor eecting artilicial drying, illustration thereof being omitted as unnecessary. Any suitable number of impression cylinders may be em ployed, and the relative dimensions of those cylinders and of the form cylinders may be varied as desired; and in case a smaller number of colors is to be printed7 the form cylinders may be held against rotation or may be removed from their bearings.

rlhe press illustratedin Fig. 2 is for the purpose of printing on both sides of the sheets, and is generally similar to the one represented in Fig. l which prints on one side only. In the Fig. 2 construction, however, twoVIV transfer devices t and u are provided which conjointly act to feed the sheets to the impression cylinder ha in reversed or inverted position, as will be understood. This cylinder h3 is the rst of three cylinders which effect the printing on that U5 side of the sheets which was unprinted during their `travel through the lirst part of the machine, the other two impression cylinders being designated it and 71,5. .Transfer cylinders g4, g5 and q are associated with these impression cylinders, and the finished sheets are delivered to the tables 8 or elsewhere by the depositing cylinder g3 which, in consequence, is removed from its Fig. l

position, where it coacts with transfer cyl- 12' inder Q2 to a inder Q0.

That I claim, is: In a multi-color printing press, the combination of a pair of successive impression position for coaction with cylcylinders, a device for feeding sheets of paper to the first impression cy1inder a transfer cylinder for feeding the sheets from said impression cylinder to the other one and disposed between the two, a gripping device carried by'each impression 'cylinder, and a plurality of gripping devices carried by the transfer cylinder; the successive gripping devices carried by the transfer cylinder being spaced apart. a distance slightly greater than half the circumference of the impression cylinder, so that during each revolution of the transfer cylinder cerremaining gripping devices, the gripping devices excluded during each revolution removing sheets from the said Afirst impression cylinder during the next revolution of the transfer cylinder.

In testimony whereof Inaliix' my signature.,

FRIEDRICH O. v. TRAITTEUR.

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