US627430A - Etching metal plates - Google Patents

Description

No. 627,430. Patented lune 20, I899.

L. a LEVY. ETCHING METAL PLATES.

(Application filed firm as, 1899.)

(No Model.) 2 Sheets-Sheet l.

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ETCHING METAL PLATES.

(Application filed Jan. 28, 1899.)

("0 Model.)

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WITNESSES UNITED STATES PATENT OFEIQE.

LOUIS E. LEVY, OFPHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO MAX LEVY, OF SAME PLACE.

ETCHING'METAL PLATES.

SPECIFICATION forming part of Letters Patent No. 627,430, dated June 20, 1899. Application filed January 23, 1899; Serial No. 703,701. (No model.)

To all whom, it may concern:

Be it known that I, LOUISE. LEVY, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented new and useful Improvements in Processes of and Apparatus for Etching Metal Plates, of which the following is a specification.

This invention relates to a process of and apparatus for producing etched metal plates, more particularly such metal plates as are used in photomechanical engraving or such branches of the art where metal plates are etched by acid or other liquid erodent to form in the plates lines, furrows, indentations, or striations for the production of printing-surfaces.

The object is, by the employment of a mordant, to produce a printing-surface upon metal in which the indentations or lines produced as the result of the process are of a more perfect character than those produced by the means ordinarily used; also, to reduce the cost of production and obviate many of the objections incident to the processes and means heretofore employed.

The present invention includes an essentially new process of applying the mordant to a prepared plate, which mordant is projected and atomized upon the plate to form therein, Where not protected by the resist and after a certain depth is etched out, cupped or con cave indentations or lines. The carrying out of the process embodies the use of compressed air and ejector-nozzles for projecting the mordant in the form of atomized spray upon a prepared metal surface, so that the mordant which is projected thereon will drop therefrom Without flowing, the plate and atomizers being within a chamber or etching-box, so that the compressed air used to project the acid or mordant will be permitted to expand in the chamber to reduce the temperature thereof and absorb the heat which isgiven off by the chemical action of the erodent on the exposed portions of the plate. The chemical combination of the mordant with the metal is accelerated by the dynamic force of the tact.

rated with the metal base instantly upon con- This results in eroding or cutting away the metal in the direction of theimpact faster than the same action proceeds laterally, so

that much or all of the required vertical depth may be etched before the lateral action of the mordant can materially affect the work. Moreover, the forcible impact of the atomized spray, besides accelerating the chemical combination of the mordant and the metallic base, prevents adhesion to the plate of bubbles of hydrogen gas andscum of metallic oXid which are developed by the chemical action and which in ordinary practice. are removed by the workmen with a brush; also, by the use of compressed air for projecting the mordant the heat evolved by the chemical action of the mordant on the plate is absorbed by the expansion of the air in the chamber, thus keeping the chamber and the plate cool, so thata stronger mordant than is usually employed can be used without detriment 'to the resist.

In the accompanying drawings, which show one form of apparatus designed to carry into effect this new process of etching, Figure 1 is a side elevation. Fig. 2 is a plan view. Fig. 3 is a-sectional view on the line 3 3 of Fig. 1. Fig. 4 is a vertical section 011 the lineA: 40f Fig. 1. line 5 5 of Fig. 2, and Fig. 6 is a vertical sectional View showing a preferred form of one of the atomizing-nozzles detached.

In the apparatus illustrated there is placed upon a stand an acid-proof tank A for the mordant,which tank has a valved inlet-pipe a and an outlet-pipe a, the latter being preferably provided with a branch pipe of for the purpose of maintaining a predetermined level of the mordant or etching fluid in the tank. The etching box or chamber 13 rests upon the bottom of the tank A, said tank having openin'gs through its sides below the normal level of the mordant, so that an air-chamber B, positioned at the bottom of the etching-box, will be submerged in the mordant,which will surround the nozzles or atomizersb, which project from the top of the air-chamber. The nozzles or atomizers b each have'a central passage toithe air-chamber and a plurality of Fig. 5 is a longitudinal section on the impact, which causes each atomized particle 1 5c of the mordant to become practically satuducts for the mo lal fi the lower ends of said 100 ducts in use being submerged in the mordant. The openings in the nozzles preferably taper, and above the point of convergence the nozzles are recessed, as shown. A suitable distance above the nozzles or atomizers the etching-box is constructed to support slides O, which receive a board,to which the plates prepared for etching are secured, and attached to the etching-box, adjacent to the openings through which the slides are inserted, are springs c,with which turn-buttons 0, carried by the slides, may be placed in engagement, and the etching-box on the opposite side from the springs has sockets or guides, in which are mounted so as to be reciprocated pins 0 The top and sides of the etching-box are preferably transparent, and to carry away the fumes and provide for a circulation of air there is attached to the etching-box a ventilating-pipe B Adjacent to the etching-box is a washingcompartment D, the sides thereof having grooves or ledges, so that the slides may be moved from similar grooves or ledges in the etching-box into the washing-compartment to be positioned over a series of perforated pipes D,which are connected to awater-snpply, so that water under suitable pressure may be projected upon the plate to remove the mordant therefrom, and to the bottom'of the compartment is secured a waste-pipe d.

To supply compressed air to the air-chamber B and to the nozzles thereof, an air compressor or pump E is mounted on the stand and connected to an air-tank E, from which air under compression is taken by a pipe e through a three-way cock f and pipe e to the air-chamber in the etching-box. The cockf is connected to a pipe g,which extends therefrom to the upper part of a reservoir G, and to the lower part of the same is attached a pipe h,which communicates with a three-way cock 1;, said cock being connected with a water-supply pipe k and to a pipe 7o,which is in communication with perforated pipes D in the bottom of the water-compartment. To the pipe 7: is secured a connection or small pipe g, which leads into the pipe 9 just before it enters the tank for the purpose of preventing the water rising above the upper portion of the pipe 9 and entering the ,pipe g. The several pipes may be provided with checkvalves to prevent any backtlow of air or water therein. The three-way cocks f and t' are provided with handles, which are connected to each other and to a lever M by a rod m, so that the cocks may be turned in unison.

The cocks are so adjusted that while the cockf is open to let the air pass into the pipe 6 the cock 2 is open to let the water pass from the supply-pipe 7: through the pipe h to the reservoir G, and when the lever is pulled back the cock f is closed to pipe 6 and open to pipe 9 and the cock 1' is closed to the pipe 7.: and opened to let the water pass from the reservoir G tolthe pipe 7t" and thence to the perforated pipes D, the force with which the water is discharged being increased by the pressure of air thereon, the compressed air entering the top of the reservoir through the pipe g when the cock f is turned to cut off the pipe e. Near the air-pump E, to engage with a pulley on the pump-shaft,is mounted a friction-wheel L,and on the shaft which carries said friction-wheel is an eccentric disk L, positioned to engage with pins 0 which abut against the slides, and when the disk is turned one of the slides C, which has been placed in engagement with the spring 0, attached to the etching-box, will have imparted thereto a reciprocating movement which changes the position of the plate to be etched with respect to the nozzles of the atomizers, so that the greatest dynamic force and quantity of the atomized mordant will be distributed over the surface of the plate instead of being concentrated immediately above the nozzles.

In carrying the invention into effect with the apparatus shown the plate is prepared in the usual manner,being coated or covered with a resist except where the mordant or etching fluid is to act. The plate or several plates to be etched are attached to a board which is placed in the upper slide, the same being passed into the etching-box, so that the plates will be supported therein face downward. By turning the three-Way cocks compressed air from the air-tank is let into the air-chamber of the etching-box and escaping through the nozzles atomizes and projects the mordant in the form of spray upon the plates carried by the slide, which is actuated in one direction by the springs and in another direction by the pins which engage therewith, the pins being actuated by the disk L, to which a rotary motion is imparted.

After the closer lines have been bitten in the plate to the required depth the plate is removed from the etching-box and washed, and the lines are then protected by a resistor varnish, after which the board and plate attached thereto are placed upon the lower slide and again inserted in the etching-box to have the mordant impacted upon the plate with greater force and quantity to deepen therein the wider depressions.

The etching-box is constructed to provide practically a closed chamber, and the boards which carry the plates when placed therein reduce the size of the chamber, in which the air under compression enters through the nozzles to project the mordant, and the air when separated from the mordant escapes through the ventilating-pipe, which enters the chamber beneath the lower slide, said ventilating-pipe carrying away the fumes created by the chemical action of the mordant on the metal.

\Vhen the slide carrying the plate is moved over or into the washing-compartinent, the three-way cocks are turned by the lever, so that compressed airis let into the upper part of the water-chamber to give the requisite pressure to the water therein, so that it may be projected with force through the perforated pipes and upon the plates, washing the latter free from what-acid may remain thereon.

In some character of work the plate may be etched to a sufficient depth without applying other than the original resist thereto, and in such work the position of the plate in the etching-box with respect to the distance from the atomiZing-nozzles may be varied as the etching proceeds.

In practice the etching fluidis impinged upon the plate in the form of a spray of minute particles, which do not affect that portion of the plate which is covered by the resist; but where the design on the metal is more or less broadly exposed the mordant or etching fluid collects and adheres, depending therefrom in the form of spherical drops, which are constantly being added to by fresh accretions. The mordant which thus adheres to the plate is kept in motion by the impact of new particles of the spray and the particles of metal which are removed by the mordant fall to the lower portion of the depending globules, so that the particles which are removed from the plate fall immediately therefrom. The tendency of a drop of etching fluid or mordant depending from a plate maintained in a horizontal position is to assume a spherical form, and this of itself after the plate has been eroded to such depth as to give elfect to the drops tends to cut a concave or cupped depression, while avoiding lateral erosion or undercutting. Etching by projecting the mordant in the form of spray upon the metal effects a great gain in rapidity of operation over the methods usually practiced, as a much stronger etching fluid may be used. The chemical action of the mordant proceeds faster vertically or in the direction of the impact than otherwise. The impact of the minute particles of the mordant does not disturb the resist which forms the design, and the heat generated by the chemical action of the mordant upon the plate is absorbed by the compressed air as it expands,which keeps the mordant, the resist, and the plate 000]. With the apparatus shown the air which has been previously compressed is allowed to expand and circulate in the etching-box, so that the etching fluid which drops from the plate passes through a body of cooled air into the tank from which it was taken, and the fumes which are given off by the process of etching are carried away by the ventilating-pipe.

In practice the minute particles of the acid or mordant impinging against the plate have their normal force of chemical afflnity enhanced by the force of their impact, which results in each particle of the acid or mordant becoming saturated with the metallic base immediately on contact with the latter, and the mordant thus loses the power of further dissolving the metal; Each succeeding particle impinges in the direction in which the etching is desired to proceed, and the process may be safely continued to a depth beyond which the finer and closer lines of the design would become too frail to stand the strain of printing were the metal undercut.

The rapid decomposition of the metal by the acid develops an amount of heat which would soon warm the plate to a degree where the resinous resist would soften and give way; but this is prevented by the absorption of the heat evolved by the expansion of the compressed air in the chamber, the expansion being sufficient to absorb even more heat than is developed on the plate, so that the plate and etching liquid is kept quite cool. A further advantage resulting from the use of a chamber or etching-box is that the gases and fumes which are so abundantly generated by the rapid chemical decomposition of the metal are carried off by the air which escapes through the ventilating-pipe, which pipe may lead to a chimney, and in this way the workroom is kept free from these deleterious vapors.

The etching liquid or erodent carried by the blast may of course be varied for different requirements. In etching copper by means of iron'chlorid there is a gain of efiiciency as compared with the immersion method, and in etching zinc with nitric acid the half-tone or crayon stipple effects are rendered by my process at least as perfectly as the current methods on copper and there is a great saving of time, apart from the saving in cost of material. IVith a blast of nitric acid a halftone etching on zinc can be produced in two minutes, with a purity of the edges of the lines and stipples fully equal to that obtainable on copper by the immersion method and with a far greater depth of the etching.

In the preparation of a zinc plate for etching the design is produced on the plate in some fatty ink by the usual photographic process. The plate is then further prepared by first melting into combination with the ink image some resinous powder to strengthen the image or design against the action of the acid, the open parts of the design or where the plate is to be etched being left exposed, such steps in the process being such as are usually practiced. My process has to do prin-. cipally with etching such a prepared plate to produce therein indentations, adjacent to which are the printing-surfaces from which an impression similar to the design can be made, and it is obvious that the design which has been produced on the plate may be readily destroyed either by abrasion, which would remove the resist, or by heat, which would soften or melt the resist. When a plate is etched by the usual means, the depression or lines are not only cut into the plate vertically, but also sidewise, which results in undercutting and in-the production of depressions in the plate, the surfaces adjacent there to being serrated, or, as it is technically called, rotten.

The apparatus which I have shown is one which may be used for commercially carrying out the process, and it may be varied in many particulars. Forin'stance, where water under sufiicient pressure can be had the water-tank and connections therefrom may be dispensed with. Other means may be used to supply compressed air to the nozzles of the atomizers, and any suitable form of atomizer may be used for projecting the mordant upon the plate.

1. The process of etching metal plates,within an inclosed space to produce designs thereon, which consists in atomizing or spraying a mordant, by means of compressed air against the face of a plate, having thereon the design through a resist, so that the dynamic force of the impact will accelerate the chemical action of the mordan t, and the compressed air absorb the heat generated by the chemical action of the mordant, for the purposes set forth.

2. The process'of etching metal plates, consisting in projecting a mordant, in atomized form, upon a plate having thereon a design, which plate is maintained within an inclosed space, the surface to be etched being substantially at right angles to the direction of projection of the mordant, substantially as set forth.

3. The process of etching metal plates, consisting in projecting by means of compressed air a mordant in the form of atomized spray upon a plate maintained within an inclosed space, said plate having thereon the design to be etched, the mordant being projected upon the plate at substantially right angles to its surface, so that the dynamic force of the impact will not affect the design, and the heat evolved by the erosive action of the mordant will be absorbed by the air which expands in the inclosed space, substantially as set forth.

4. The process of etching metal plates, which consists in projectinga mordantin the form of spray from a plurality of atomizers upon the plate and moving the plate while under the action of the mordant.

5. The process of etching metal plates by a mordant,which consists in atomizin g or spraying the mordant upon the surface of a prepared plate, moving the plate while it is being etched to change its position with respect to the atomizers, for the purpose set forth.

6. The process of etching metal plates, con sisting in applying to the plate a prepared design, subjecting it in an inclosed space to the action of a mordant which is projected upon the plate by air under compression, the expansion of the air absorbing from the plate and mordant the heat evolved by the erosive action of the mordant in etching, and finally washing the plate, substantially as set forth.

7. The process of etching metal plates having thereon a design in resist, which consists in projecting an atomized erodent against sisting in projectingaliquid erodent or mor-' dant upon a plate maintained in a horizontal position face downward.

10. The process of etching metal plates bya mordant or acid in liquid form, which consists in atomizing the mordant against the under surface of a plate maintained in a horizontal position.

11. The process of etching metal plates, which consists in projecting or spraying a liquid mordant or etching agent upward against a plate supported horizontally in an inclosed space or chamber.

12. The process of etching metal or other plates by a liquid acid solution or equivalent erodent, which consists in projecting the erodent or acid in the shape of spray upward against and at substantially right angles to the face of the plate to be etched, said plate being maintained in a horizontal position.

13. The process of etching metal plates by a mordant or an acid solution in liquid form, which consists in projecting the mordant in comminuted form mechanically upward against the under surface of a plate which is maintained face downward, the mordantso forced against the plate being permitted to fall into the body of the solution whence it was taken.

14. The process of etching metal plates by a mordant or acid solution which consists in maintaining a plate inverted in a horizontal position above a body of the solution, atomizing and projecting the solution in the form of spray upward against and in adirection at substantially right angles to the surface of the plate to be etched and permitting the solution so projected against the surface of the plate to fall by gravity or drop into the body of the solution.

15. A step in the process of etching a surface having thereon a resist which consists in atomizing by the use of compressed air a mordant upon the surface maintained in an inclosed space or chamber the expansion of the air in said chamber absorbing the heat which arises from chemical reaction, for the purpose of preventing deterioration or destruction of the resist.

16. In an apparatus for etching, the combination of a receptacle having means for maintaining thereina plate in a horizontal posi tion, the plate having a design thereon, atomizers and an acid-tank, for the purpose set forth.

17. In an apparatus for etching, the combinationof a receptacle or chamber having means for maintaining therein a plate, a plurality of atomizers projecting from an airsupply toward the plate, an acid-tank adapted to contain acid so as to partially surround the atomizers, and an air-supply in communication with the atomizers, for the purpose set.

forth.

18. In an apparatus for etching, the combination with a chamber or etching-box having means, for maintaining therein a plate, means for moving the plate-support, a plurality of atomizers maintained within an acid-proof tank which contains a liquid erodent so as to project the erodent at right angles to the plate within the chamber, and means as an aircompressor connected with the atomizers for projecting the erodent and reducing the temperature within the chamber so that the heat given off by chemical reaction of the erodent upon the metal will be absorbed.

19. In an apparatus for the production of designs or printing-surfaces by etching, the combination with an etching-box having means for maintaining a plate therein, of atomizers, a chamber for compressed air connected with the atomizers, and a tank for the mordant, for the purpose set forth.

20. In an apparatus for the production of designs in metal plates by etching, the combination with an etching-box having means for sustaining therein a plate, a tank for the mordant, an air-chamber within the etchingboX, and means for projecting the mordant against the plate.

21. In an apparatus for the production of etchings, the combination with an etchingbox having a slide to support a plate, openings for introducing the slide to the etchingbox, and means for reciprocating the slide, of a tank or receptacle for the mordant, a plurality of devices within the etching-box for atomizing or spraying the mordant upward, said devices being arranged at uniform distances apart, and means for conveying air under pressure thereto, substantially as shown.

22. In an apparatus for etching, the combination of an etching-box, a movable platesupport, an acid-proof tank which contains a plurality of atomizers for projecting a mordant from the tank upon the plate and means for moving the plate-support to change its position and the position of the plate or plates carried therebywith respect to the atomizers.

23. In an apparatus for etching, the combination 'with anetching-box and means for projecting a mordant upon a plate positioned therein, of a washing-compartment having means for projecting a fluid, and a plate-carrier which is movable from the etching-box into the washing-compartment, substantially as shown.

24. In an apparatus for etching, the combination of a tank containing compressed air, an etching-box or chamber having at its lower portion an acid-proof tank from which project a plurality of atomizers, means for atomizing a mordant by air under compression,

so that the mordant will be projected upon the plate in the form of comminuted spray and means for reciprocating the plate in the etching-box, for the purpose set forth.

25. In an etching apparatus,an etching-box having an air-chamberwith atomizers, atank adapted to contain a mordant which surrounds the atomizers, means for compressing air and supplying it through the air-chamber to the atomizers, a plate-carrying slide mounted within the etchingrbox and removabletherefrom, a water-tank in communication. with a water-supply and with the air-compressor, a washing-compartment having therein a series of perforated pipes, and cooks for controlling the air and water supply, the parts being organized forcooperation, substantially as shown and for the purpose set forth.

26. In an apparatus for the production of etchings, the combination with a chamber or etching-box having means for sustaining horizontally therein a plate, a receptacle for etching liquid at the lower part of the chamber or etching-box, an air-supply and means connected to the air-supply for projecting the etching liquid upward against the plate.

27. In an apparatus for the product-ion of etchings, the combination with a chamber or etching box having means for sustaining therein a plate in a horizontal position, of a tank containing etching liquid, an air-blast, and a device connected with the air-blast by means of which the etching liquid may be projected upward against the plate.

28. In an apparatus for the production of etchings, the combination with an acid-proof chamber or etching-box having one or more transparent sides, supports to maintain a plate horizontally within the chamber, and a tank or receptacle for holding a supply of etching liquid, of a plurality of atomizers arranged within the tank and connected with an air-blast by means of which the etching liquid may be projected upward against the plate.

29. In an apparatus for the production of etchings, the combination with a chamber or etching-box having openings and supports for maintaining a plate in a horizontal position, of a tank containing etching liquid positioned at the base of the chamber, a plurality of atomizers Within the tank, means for conveying air under pressure to the atomizers and a pipe for conveying gases or fumes from the chamber or etching-box, substantially as shown.

30. In an apparatus for the production of etchings,the combination with a chamber having means for sustaining therein a plate and openings for introducing the plate into the chamber, of a tank containing etching liquid, a plurality of devices Within the tank for producing atomized spray the nozzles of which point upward and are arranged at substantially uniform distances apart and a pipe

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