US2136024A - Process and apparatus for producing metallic coatings on various articles - Google Patents

Description

H. SCHNEIDER Nov. 8, 1938.

PROCESS AND APPARATUS FOR PRODUCING METALLIC COATINGS ON VARICUS ARTICLES Filed May 3, 1955 INVENTOR. t'a/ns Schneider BY amuwzg w ATTORNEY.

Patented Nov. 8, 1938 PATENT OFFICE PROCESS AND APPARATUS FOR PRODUC- ING METALLIC COATINGS narrows 0N vanrous Hans Schneider, rm Cheater, N. Y., assignor to Metal Forming a Coating, Inc.,'a corporation of New York Application May 3, 1935, Serial No. 19,564 5 Claims. (01. 91-122) My invention relates to a process and apparatus for producing a metallic coating, particularly a silver coating on various articles, metallic or non-metallic.

In the prior art where the solutions were blown in separate mists from the nozzle and mixed in midair, considerable portions of the solutions never came into contact for their chemical reaction before they reached the article to be coated.

Further in the prior art, where the solutions were subjected to an air jet whether mixed before leaving the nozzle or not, they reached the article in the form of a mist. This interfered with good results, particularly in coating the molds used in electrotyping, where there are many fine cracks and crevices. I have found that better results are obtained wherethe mixed solutions are blown at the article in as nearly an unbroken stream as possible or in large fragments of the stream as opposed to a mist. The impact against the article is far greater where the liquid is thrown at it by the air jet in comparatively large masses than where blown as a fine spray or mist. The large impact obtained in my invention is very effective in producing a good coating. It removes air bubbles and enters fine cracks and deep crevices.

It is an object of my invention to mix the solu tions in substantially unbroken stream form after leaving the nozzle. It is a further object to blow a stream of mixedsolutions with as little breakingup as possible with considerable force against thearticle to be coated. I

My process and apparatus are economical in the use of the reagents as large fragments of liquid are thrown directly at the work instead of the reagents being scattered in. a mist, only a part of which settles upon the work.

Some of the matter disclosed herein formed part of my abandoned application Serial No. 592,092, filed February 10,- 1932.

Other objects and advantages will become apparent upon a further study of the description and drawing, in which:-

Fig. 1 is a diagrammatic view of an apparatus for carrying out my invention, the nozzle being shown in section, and

Fig. 2 is an end elevation of the nozzle shown by itself.

The apparatus and process will first be de-,

scribed as used in coating an article with silver.

A container 3 is used to hold a solution of silver nitrate. The container 4 is used to hold a'formaldehyde solution. Leading from container 3 is a tube 5 which is connected to passage 6 in the nozzle or supporting member 1. Leading out from the forward end of passage 6 is a bent pipe ii having a reduced front orifice. From container 4, another tube 8 leads to passage 9 of nozzle 1. Leading out from the forward end ofpassage 9 is a bent pipe I!) having a reduced front orifice. Pipes l0 and II incline forwardly beyond nozzle 1 and converge toward each other with their front orifices so aimed that streams the front of nozzle 1 and so aimed that the issu--' ing air jet 30 strikes the meeting place from behind the streams caused to issue from pipes l0 and II. The front of nipple I l is some distance to the rear of the orifices of pipes l0 and H. Nipple l4 and pipes l0 and H are preferably so aimed with respect to one another, that the streams issuing from said pipes have equal inclinations to air jet 30.

A passage i5 leads from air-passage i3 and extends to the rear of nozzle 1 where it joins with tube It. The lower end of tube I 6 is provided with two branches, one branch I1 leading to container 3 and the other branch l8 leading to container 4. A short tube [9 leads from branch l1 through stopper 20 into the inside of container 3, while a short tube 2| leads from branch l8 through stopper 22 into the inside of container 4. A tube 23, leading from the bottom of tube 5, extends through stopper 2!! to a point near the bottom of container 3, while a tube 24, leading from the bottom of tube 8, extends through stopper 22 to a point near the bottom of container 4. Valves 25 and 21 may be provided to regulate the .flow of solutions through tubes 5 and 8. A valve 26 is provided to regulate the flow of air from air ,line l2. Valves 25 and 21 may be placed on to nipple I, also branches oil into passage I5 passing through tube l6, through branches l1 and I8, and tubes I 8 and 2| into containers 3 and 4, causing pressure on the top of the liquids held in said containers. Said pressure forces the silver nitrate solution up tube 23, through tube 5, passage 6 and out the orifice of pipe I I. Similarly, the formaldehyde solution is forced up through tube 24, through tube 8, passage 9 and out the orifice of pipe ll). Pipes I0 and H are aimed to have their issuing streams of solutions meet at a place along the longitudinal axis of air jet 30, the inclinations of said streams to said axis being equal. The apparatus is so proportioned that the streams issuing from pipes l0 and H may be equal in velocity and in the quantity of liquid delivered per second. Adjustment of valves 25 and 21 are helpful in maintaining these conditions, although said valves may be omitted if the parts are carefully proportioned. It is desirable to use as few valves as possible on the solution lines as the former tend to clog and thereby interfere with the operation.

The conditions for maximum efficiency of my process are to have the two streams issue from pipes l0 and l I at equal velocities, in equal quantitles at equal inclinations to the longitudinal axis of air jet 30 and to meet at a place along said axis. With these conditions fulfilled, the streams will coalesce and produce a resultant stream 28 having a longitudinal axis coincident with the longitudinal axis of said jet for a substantial distance beyond the place of meeting. Actually, a certain amount of variation will occur and a certain amount of splashing will take place at the meeting of the streams.

Coming from behind the place of meeting of the streams, which place is the origin 29 ofv resultant stream 28, and blowing in the same direction as the resultant stream, air jet 3!! blows said resultant stream forward substantially en masse or, at the worst, in large fragments thereof instead of breaking it up into a mist. Air jet 30 causes the place of meeting 29 of the issuing streams to be on the longitudinal axis of said jet forward of where it would occur were there no air jet.

The air jet 30 is regulated in intensity to have suflicient strength to blow the resultant stream at the work with substantial force, but yet with insufficient strength to convert the issuing streams into a mist and with insufficient strength to prevent their meeting. The spacing of the forward end of nipple H a substantial distance to the rear of the forward orifices of pipes l0 and I I softens the effect of air jet 30 upon the issuing streams, helping to prevent the formation of a mist and to allow the issuing streams to meet.

When air line I2 is closed off by valve 26, the pressure is relieved in containers 3 and 4 by the escape of the air from said containers through tube I6, passages l5 and I3 and out nipple 14, allowing the liquids in tubes 5 and 8 and passages 6 and 9 to return to their respective containers by gravity and siphoning, preventing thereby loss of these liquids when nozzle I is handled, and the apparatus is not in use.

Means for heating the solutions are not shown as this can be readily provided for by those skilled in the art.

If desired, another container, not shown, for a third solution may be used, said container bein connected to air tube It and having a tube, similar to tube 8,"lea ding therefrom to another passage to be provided'in nozzle 1, and Having another bent pipe similar to pipes l0 and H and aimed to have its issuing stream strike the place of meeting of the other two.

In carrying out my invention for producing a silver coating, I prefer to use a silver nitrate solution consisting of 16 grams of silver nitrate per 1 gallon of' water, and a formaldehyde solution consisting of 2'76 cc. of formaldehyde per 1 gallon of water. However, I have found that the percentage of silver nitrate per gallon of water may be varied from 10 to 30 grams, and still produce good results. I have also found that I may successfully use to 510 cc. of formaldehyde per gallon of water. As noted above, I apply these solutions in equal parts. As is well known in with tin chloride. Instead of using formaldehyde as a reducing agent, as is well known in the art, Rochelle salts may be used instead. Ammonium silver nitrate solution may also be substituted for the silver nitrate solution.

Deposits of other metals besides silver may be done according to my invention. For making copper deposits, I prefer to use a solution of 20%- 50% hydrazene hydroxide and a solution of dilute copper sulphate. For making lead deposits, I

prefer to use a solution of dilute thiocarbamide mixed with 2% of lead acetate and a 5% solution of ammonium hydroxide. For depositing gold, I prefer to use a l solution of gold chloride and a solution consisting of a mixture of 50% glycerin and 5% sodium hydroxide with traces of mannite as an accelerator.

Generically speaking, the pipes l0 and II, and the passages 6, I, '9 and IS, with their enclosing walls, are conduits supported by the nozzle or member I.

The terms liquid form or liquid are used the art, the article to be coated may first be coated I in the claims in the sense as opposed to mist or the mixed streams to strikethe object to be coated, the general direction of the mixed streams and the jet being the same, the solutions containing metallic and reducing compounds capable of reacting chemically 'upon the mixing of the solutions, to deposit the metal of the metallic compound as a coating on the object, the air jet impinging upon the streams with force restricted to hinder the formation of mist but suilicient to throw the mixture of the streams with considerable force in relatively large liquid masses upon the object.

2. In the art of coating objects with silver, the process which consists in forming two streams in liquid form, one a solution of a silver compound and the other a solution of a reducing agent therefor, mixing the streams by causing them to meet in liquid form in midair, and directing a jet of air against the mixed streams causing the mixture to be thrown against the object to be coated, whereby a silver coating is deposited upon said object, the air jet impinging upon the mixture with force restricted to keep down the formation. of mist but suflicient to throw the mixture with considerable force in comparatively large liquid masses upon the object.

3. Apparatus for coating objects with metal comprising a pair of conduits, a member for supporting said conduits, said conduits extending beyond the front of the supporting member, means connected to said conduits for sending without substantial formation of mist a solution of a metallic compound through one conduit and a reducing solution therefor through the other, said conduits discharging their solutions in liquid form in streams directed to meet and mix in midair, and means upon said member for directing a current of air at the mixed streams from the rear of the meeting place of the streams with the force of the current restricted to keep down the formation of mist, for throwing the mixture in liquid form upon the object to be coated for depositing a metallic coating thereon.

4. Apparatus for coating objects with silver comprising a nozzle having two passages therethrough, means connected to said passages for sending a solution of a silver compound through one passage, and a solution of a reducing compound therefor through the other, a pipe-leading out from the front of each of said passages directing the streams of the solutions issuing therefrom to meet in midair, said nozzle having a third passage therethrough, means for sending air under pressure through said third passage to discharge at its forward end, and means at the forward end of the third passage, but at a substantil distance to the rear of the meeting place of the streams, for directing the issuing air at said meeting place for throwing the mixed streams upon the object to be coated for depositing a silver coating thereon.

5. In the art of coating objects with metal, the process which includes forming two unsupported liquid streams of different solutions, directing them to meet in midair at an angle less than 180 degrees and mix in liquid form, and directing a jet of air against the meeting place of the streams from substantially within said angle and along a plane intersecting both streams, each stream making the same angle with the jet, said jet impinging upon the streams with force restricted to keep down the formation of mist and to permit the meeting of the streams, but suflicient to throw the mixture of the streams with considerable force in comparatively large liquid masses upon the object, one of said solutions containing a metallic compound and the other containing material capable of reacting chemically with the metallic compound to form a coating of the metal on the object.

HANS SCHNEDER.

Images