US3429763A - Etching grill for one-step etching machines - Google Patents

Description

Feb. 25, 1969 w. HERTENSTEIN 3,429,763

I BTCHING GRILL FOR ONE-STEP ETC-HING MACHINES Filed Jan 27, 1965 FIG; 2

FIG.3 FIG.5

17 y 11' A INVENTOR.

{ i Miter Herzewsfez'n lll BY ATTO E) United States Patent US. Cl. 156345 1 Claim Int. Cl. B41f 27/00 ABSTRACT OF THE DISCLOSURE This invention relates to a device for supporting a plate in a one-step etching machine having a plate support which comprises a base frame adapted to be connected to the plate support, an etching grill adapted to be connected to the base frame, the grill having a plurality of grid bars, and means for attaching to the grill at least one plate to be etched.

In the reproduction art, it is known to prepare relief printing plates by applying a reproduction coating to an etchable metal plate, e.g. a zinc, brass or copper plate, and exposing the coated side of the plate under a master. In a subsequent developing process, the reproduction coating is fixed in the image areas, while in the non-image areas the light decomposition product is removed and the surface of the etchable metal is bared. In the etching process which follows, the metal areas in the non-image areas are deepened, whereas the fixed image areas are not attacked. After the etching process, a positive image of the master is obtained in the form of a relief in which the image areas are elevated over the non-image areas. From a block prepared in this manner, prints may be obtained in a printing apparatus, if desired, after a manual after-treatment.

As is known, etching of the bared metal surfaces is performed by means of aqueous solution of strong acids capable of dissolving the metal in question, generally nitric acid. The aqueous solution of the acid contains so-called side-wall protectors, e.g. mixtures of fatty substances, wetting agents and complex formers, which are added in order to protect the bared side walls of the image areas as much as possible against the attack of the acid.

It is known to use one-step etching machines for the etching process. They consist usually of an acid-resistant trough provided with a swivelling lid on the inside of which the metal plate to be etched-in the following called plateis fastened. The trough contains the aqueous acid and the water insoluble protective agent for the side-walls. The part of the trough which contains these liquids is provided with elements, such as rotors or jets, which are capable of intimately emulsifying these liquids, which are not miscible with each other, and spraying them against the plate mounted on the plate support by means of a supporting system consisting of grooves, clamps and screws, so that the back of the plate is in contact with the plate support. This device has the following disadvantage: After each separate etching process, the attachment screws have to be unlocked by hand in order to remove the plate. Then the plate support, the grooves, the clamps and the attachment screws must be carefully cleaned, also by hand, because any traces of the etching solution which are not removed may damage the next plate, which in most cases is taken from an aqueous pre-treating bath, and make it useless. After ice placing the next plate in position, the attachment screws have to be fastened again. It is only after the lid has been again closed, that the next etching step can be performed. Very skilled operators are necessary for performing all these working steps. In particular, it is necessary to perform the different working steps in very rapid succession, in order to prevent the emulsion contained in the trough from decomposing. Moreover, great care must be taken when cleaning the plate support and the supporting system. Any traces of rags or sponges used for cleaning, which are taken up by the emulsion, may impair its quality. Even skilled operators are not always capable of meeting the combined requirements for high speed and simultaneous great care, which are necessary if flawless blocks are to be obtained. A further drawback of the known systems of supporting the plate is that only one plate at a time may be fastened to the plate support, irrespective of the size of the plate.

The present invention provides a removable supporting system which may be used as an accessory device for the known one-step etching machines. The supporting system according to the invention consists of a base frame to be mounted to the plate support, a removable etching grill to be mounted on the base frame, which etching grill is provided with a frame of the size and shape of the base frame, and several grid bars provided with elements for mounting the plates.

The rigid base frame is made of high-quality steel or another material resistant to the etching solution, e.g. light metal. It is provided with fitting means for attachment to the clamping jaws on the plate support and is attached to the clamping jaws by means of the attachment screws of the plate support in the same manner as the plates to be etched were hitherto fastened. The base frame remains in the etching machine. The base frame consists in most cases of tubes which are connected to each other and which generally have a diameter from about 1.2 to about 1.5 cm., but may also be narrower or Wider.

The etching grill likewise consists of a material resistant to the etching solution. The grill frame corre sponds to the base frame. Advantageously, the grill frame, which generally consists of band-shaped material bent in the manner of hollow-profiled material, surrounds the base frame. Preferably, both frames are of rectangular shape, so that as many rectangular plates as possible of a smaller size can be arranged within the etching frame. In principle, however, the frames may be of any other geometrical shape, e.g. take the form of a trapezoid, a square or a circle. Two opposite sides of the grill frame are connected to each other by several thinner bars which are advantageously arranged parallel to each other. To fix their position, the thin bars may be connected by one or more longitudinal bars so that a grid-like rigid structure is formed. The upper side of the etching grill, i.e. the side pointing upwardly when the grill is placed in position in the opened, vertical or almost vertical lid of the trough, is provided in the middle with a loop which is hooked over an adjusting pin in the corresponding position on the base frame. The lower side of the etching grill has in its middle a closing mechanism by means of which it can be securely fastened to the base frame, e.g. by moving a lever. Elements of known type, e.g. small plate clamps, are provided for fastening one or more plates to the grid bars. Two plate clamps for each plate are sufficient.

It is advantageous and saves time to use two etching grills with one base frame, so that the grills can be alternated, one being in the etching machine, while the other is prepared for the next etching step, i.e. is provided with the plates to be etched during the next step. This facilitates a particularly speedy performance of an etching program and avoids decomposition of the emulsion, which is likely to occur when no plates are treated.

An etching process in a high-speed etching machine in which the supporting system according to the present invention is used may be performed, e.g., as follows:

The base frame is positioned in the lid of the machine in operation while the etching solution is emulsified. After removing all traces of fog, i.e. remnants of layer from the areas to be etched, the plate is taken from a cleaning hath, e.g. 3 percent nitric acid, and is fastened to the first etching grill by means of plate clamps. During this time, the plate is constantly sprayed with water in order to avoid, as far as possible, the access of atmospheric oxygen to the bared metal surface. As soon as the etching solution is sufiiciently emulsified, the mixing device of the machine, e.g. rotors moved by a drive, is switched off and the lid of the machine is opened. The etching grill having the plate fastened thereto is fitted into the base frame of the machine and its lower side is secured to the base frame by turning a locking lever, whereupon the lid of the trough is closed. The time elapsing between opening and closingof the lid is generally very short and amounts, e.g., to to seconds, so that no perceptible decomposition of the emulsion takes place. The emulsifying device is then started again and the etching process begins. While etching is performed, using the first etching grill, one or more further plates are advantageously mounted onto the second etching grill in the manner described above. After the etching process has proceeded for the desired time, the mechanical motion of the etching solution is interrupted and the lid of the trough is opened, the first etching grill is removed from the machine, and the prepared second etching grill is immediately fastened to the base frame, whereupon the lid is closed and the rotor started again. Now, etching of the plate fastened to the second etching grill begins. Etching of a series of plates by alternating the two etching grills can be continued until the etching solution requires regeneration. During regeneration, the machine is operated for a short period of time with the etching grill removed, so that a complete and dependable emulsification of aqueous and organic phases is guaranteed.

By using the etching grill according to the present invention as an accessory device to known one-step etching machines, considerable savings in time are achieved in the insertion and removal of the plates to be etched. The more rapid succession of the individual etching steps causes an improved stability and better yield of the etching solution. Insertion of the plates is facilitated, because the plates no longer come in contact with moistened machine parts. It is no longer necessary to clean the plate support and the means for attachment between the single etching steps. Thus the causes of trouble mentioned above, eg fouling of the etching solution by foreign matter, are avoided. Since the etching process is simplified, the one-step etching machine may be operated by less skilled personnel. Finally, the application of the etching grill according to the present invention for the first time offers the possibility to etch several copies of smaller shapes in one etching process.

Preferably, the device according to the invention is used for relief printing. It may, however, be applied in certain cases also to intaglio printing processes, provided that the metal surface to be etched is plane.

The invention will be further illustrated by reference to the accompanying schematic drawings in which:

FIGURE 1 is a plan view of the interior of the lid of a one-step etching machine,

FIGURE 2 shows the interior of the lid of FIGURE 1 with a base frame attached thereto,

FIGURE 3 shows the lid and base frame of FIGURE 2 with an etching grill attached thereto,

FIGURE 4 is a view in detail of one of the clamps used to secure a plate to the etching grill, and

FIGURE 5 is a view of the base frame and etching grill as shown in FIGURE 3 with two printing plates secured to the grill in the position they occupy while being etched.

Referring to the drawings, there is shown the interior of a lid 1 of a one-step etching machine having a pivotable plate support 2 thereon. The latter" has a plurality of guide grooves 3 therein and clamping jaws 4' slideable in the grooves, which jaws are provided with clamping bolts and nuts. The parts illustrated in FIGURE 1 are present in every one-step etching machine presently being marketed.

Referring to FIGURE 2, the interior of the lid 1 of the one-step etching machine, having the plate support 2 thereon, also has a base frame 5 secured to the latter, the base frame having the braces 6 and fitting means 7 as well as an adjusting pin 8 and a notch 9 for mounting an etching grill, not shown in FIGURE 2, in an exact desired position thereon.

FIGURE 3 shows the base frame of FIGURE 2 having a rectangular etching grill 10, including the grid 11, secured thereto. The grill includes the transverse bars 12, the longitudinal bar 13, the loop 14, which is hooked over the adjusting pin, not shown in FIGURE 3, of the base frame when the etching grill is placed in position, and the locking lever 15 which, when turned into a notch, not shown in FIGURE 3, of the base frame connects the latter to the grid 11.

Referring to FIGURE 5, there is shown the lid 1 on which the plate support 2 is pivotably mounted, the latter containing three guide grooves 3 in which the clamping jaws 4 slide and which latter are secured in position by means of clamping bolts and nuts. The rectangular base frame 5 is shown in position on the plate support 2 and it is placed in position by slipping the fitting means 7-under the clamping jaws 4 and it is then bolted on in this position. The loop 14 of the etching grill 10 is hooked over the adjusting pin 8 and the locking lever 15 is engaged in the notch 9 while two plates 71 to be etched are secured to the transverse bars 12 by means of plate clamps 16, which latter are shown in detail in FIGURE 4.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A device for supporting a plate in a one-step etching machine having a plate support which comprises, a base frame adapted to be connected to the plate support, said base frame including a pin and a notch for mounting an etching grill, an etching grill for connection with said base frame, the grill including a plurality of spaced grid bars, the grill having a loop fitting over said pin, the grill also including a locking lever for reception in said notch whereby the etching grill can be quickly attached and released with respect to the base frame, and plate clamps for securing at least one plate to said grill bars.

References Cited UNITED STATES PATENTS 708,052 9/1902 Kitsee 156-14 x 3,136,671 6/1964 Martz et al 15614 924,934 6/1909 Reverdys 134-143 JACOB H. STEINBERG, Primary Examiner.

US. Cl. X.R.

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