US1712284A - Method and apparatus for electrodeposition - Google Patents

Description

May?, 1929. 1 c. TuRNocK METHOD AND. APPARATUS FOR ELECTRODEPOSITION Filed Dec. 17, 19,25

DWZ OFGOLD.

INVENTOR M C, w

Patented Nlay 7,- 1929.

UNITED STATES;

PATENT OFFICE;

LAWRENCE C. TURNOC'K, OF EDGEWQOD, PENNSYLVANI.

METHOD AND APPARATUS FOR ELECTODEPOSITION.

appncationm'ea December 17, 1925.V 'serial 1"N0.75,e57.

utility as applied'to the art'of electroplating comparatively large objects, such as band and orchestra instruments and the like, which have Aa relatively large surface area as compared with small articles of jewelry and objects of similar nature. The word band 'j will hereinafter be used generically as delimtive both of band and orchestra instruments,

the distinction between such instrumentsy quite frequently being in the manner of their Y ultimate use4 and not inI any features of construction. y, i When plating articles such -as band instruments and the like, and especially with' the metals goldand silver, the problem of obtaining and linsuring. vaccuracy in the weight andthickness of the deposit of metal is of extreme importance owing to the monef tary value represented in v the deposited metals. Not only is it desirableto deposit on such articles the minimum weight and thickness of metal coating consistent with obtain.- ing a plated article that will be, guaranteed a serviceable life of reasonable length before the metal coating becomes impaired, but it is likewise particularly desirable andim ortant. that there be uniformity in the Weig it and thickness of metal deposited per unit of exposed surfacearea on all such articles ir?- respective of their total surface area. v

Untilcomparatively recently, the only method of controlling orascertaining the amount of metal deposited in a plating bath has been to utilize an ammeter and estimate, the average current ilovvV during .the given period'of plating. The product of the estimated average current in amperes and the elapsed time in hours gives the approximate number of amperehours of electricity v passed, and enables the weight of the deposit of metal to be rough calculated. N

y prior United "51,527,13 5, granted February 17', 1925, there are disclosed certain improvements in the art of electroplating and more particularlywith l respect to 'a method of obtaining great vac'- curacy with respect-to the coating on each individual article. The present invention is adapt-able invfaccordance with the disclosure tates Patent No.-^

special problems have heretofore presented themselves due to the fact that the plating loperation has usually comprised, in` reality,

a ashing of the metal onto the articles. The currentflow as well as the duration of the plating period insuch cases are both so small that difficulty has been encountered in attempting to actually measure the equivalent quantity of electricity passed, from which the weight of metal 'deposited is in turn calculated. With some of thesmallerarticles,such as jewelry and the like, it has heretofore been proposed to utilize meters, but due to the diiiculty referred to, where meters have actu- Ially been used with gold plating, it has been customary to provide two meters connected 1n series for each bath. One of these meters has recorded both the auxiliary load and the quantity` of electricity passing to the plating bath, while the other has recorded'only the auxiliary load, The difference in reading between the meters has then been used 'to (letermine the amperehours of Pelectricity passed, and from this value ythe amount of metal deposited. .This operation, however, lis not entirely satisfactory as itV involves the -possibility of error both in meter readings and comparisons, as well as the possibility of a difference in accuracy as between' the meters.

In vieri7 of these objections and difficulties I are necessarily comparativelyl articles is necessarily expensive, and particuj larly so when plating with gold froma cy anide bath from which the rate of'deposit ofgold at the same current flow is substantially three tunes as rapid as when plated with gold from a gold chloride bath. In

order, however, to maintain and insure a given standard of excellence of metal coating, it is obvious that any error, where approximation is the basis of operations, must be on the side of too heavy a deposit.

The present invention has for one of its objects to provide an improved method of plating comparatively large articles, and particularly band instrnn'ients and the like, with gold or silver` Another object of the invention is to `provide an .improved meter adapted for use with gold cyanide baths, and particularly such baths asaidapted for the application of protective or ornamental metal coatings to articles ofthe character referred to, or to other large articles of the general nature hereinafter referred to.

Still a'lnother object of the invention is to provide means of' keeping an exact record of all metal going onto the plated articles. I-Ieretofore, the manufacturers of band instruments for example, have been obliged to ascertainyihe amount of metah'and especially gold or silver, plated on their product by noting the loss in weight of their anodes from one day to the next. This method not only' involves considerable error, but requires the removal of the anodes from the tanks, together with the loss of considerable time.

In the drawings, there are shown for purposes of illustration only, certain preferred embodiments of the present invention, it being understood that the drawings do not deline the limits of my invention,I as changes in the construction and operation disclosed therein maybe made without departing either from the Spirit of the invention or the scope of my "broader claims.

In the drawings:

Figure l is a diagrammatic view illustrating a plating bath and the circuit connections therefor; i

Figure 2 isa front elevational view, largely-diagramrnatic,illustrating a meter constructed in accordanee with the present invention and having its dial reading directly in units of gold deposited from a cyanide bath; and f Figure 3 is a view similar to Figure 2 illustrating ameter having its dial calibrated to read directly inunits of silver.

I have found thatwhen working with gold cyanide baths the theoretical amount of gold deposited per aniperehonr outhc article being plated is 4.7528 dwt. lurking on this basis I have had meters constructed in which the dials read directly in unit weights of metal deposited, the desired readings being obtained by construction, sub'dividing and lnarkmg the dials on the basis that each amperehour of electricity passing through the bath is equivalent to approximately 4.728 pennyweights of gold. It will be understood that the value or constant 4.728 is based on a theoretical plating etliciency of 100%, this constant varying as the percentage of elliciency varies. It will be understood, however, that the present invention contemplates the use of this constant,-or certain multiples` thereof on the basis of the etiiciency referred to, together with any changes that m'ay be required by reason of this etliciency or character of the bath.

In Figure 2 of the drawings` there is illustrated a meter M having a dial 2 witli graduations 3 reading directly in pcnnyweights of gold in accordance with the present invention. It will be obvious that on thebasis of the constant 4.728, other readings directly in grains or grams may be readily calculated. Such a dial enables the meter to beread directly in weights of gold and a predetermined weight having been calculated for a given article or series of articles, a glance at the lneter will instantly show when the desired amount of metal has been deposited. 'lhe use of such a meter makes it possible to obtain great accuracy in the desired weights of deposited metal as well as great accuracy inthe uniformity of plate on ditl'ercnt articles such as band instruments or thev like, thereby insuring the manufacturer against any great loss of metal by reason of deposits which are too heavy. Furthermore, the use of such a meter makes possible the adoption of standards of weight and thickness of gold or silver or other metal plate to differentsize instruments or similar articles, and likewise greatly facilitates the execution of such established standards. Heretofore similar articles have shown a lack of uniformity due to the absence of an effective means of executing any given standards, accurate control having been cxtremely difficult with respect to time and eurrent factors in view of the personal equation and judgment of the operators.

wWhere silver is the metal being deposited, the constant is 2.588 dwt. of metal per amperehour, and the meters in such cases are similarly graduated to read directly in unit weights of silver. Such a meter is indicated at M' in Figure 3 in which the dial 2 has graduations 3 reading directly in penny- Weights ot silver, such meter being adapted for the silver plating of large objects of the character herein set forth.

The present invention also enables the weight and accordingly the thickness of the plating to be automatically controlled and the plating period definitely terminated wilhout the intervention of the operator. In Figure 1 ofthe d 'awings there is illustrated more or less diagrammatically one form of circuit involving the present invention. In this tigure there is indicated a source of direct current Gr having its positive terminal connected to a line L. This'line may have any desired number of branches such as lindicated at 4.. and each of which may lead to one or more anodes A in a plating tank or tanks T. The cathode or cathodes C in each of these tanks are in turn connected to one side of a meter M of the character illustrated for example in Figure 2 of the drawings. By' reason of the location of the meter on the cathode side of the circuit, they are only effective for measuring the actual How of electricity which has been effective on the cathodes. I have found such a positioning of the meter to be highly desirable as compared with the positioning on the anode side of the circuit, inasmuchl as the total flow through the anodes may not be effective for plating purposes due to leakage or other losses. The opposite side of each of the meters is connected to a common wire 6 leading to one terminal of a totalizing meter TM, the connection of each meter to the comnion wire 6 preferably including a circuit breaker 7 for the purposes hereinafter referred to. The opposite side` of the totalizing meter'is in turn connected to the negative terminal of the source of current.

lEach of the meters may have a pointer 8 adapted to cooperate with the calibrations 3 and a hand 9 adapted to be manually moved to any desired position. Having determined the desired amount of metal to he deposited, the hand 9 of each of the meters 3 will be set at the-desired point. Upon establishing a flowof electricity, the pointei 8 of eachof the meters will commence its travel in a clockwise direction in accordance With the actual* flow of electricity. .The hand 9 of each of the meters M has a connection 10 to one side of an auxiliary line fw, `while the` pointer 8 of each meter has a similar connection 11 to the opposite side of an auxiliary line w', this last mentioned 'connection' including a 'magnetic coil 12 cooperating with the circuit .breaker 7. By reason of this construction), when the pointer 8 coincides with the position'of the hand 9, the circuit will be closed through the` coil 12 thereby operating the circuit breaker to open the circuit to the particular' bath controlled by that meter. It will thus be seen that the plating operation can be automatically terminated atwill. 'y

|llhe totalizing meter TM may be of any desired construction adapted to read directly inA unit Weights of metal, whereby it is possible to determine the actual amount of metal deposited by merely glancing at the totalizing meter. This obviates the necessity of bodily removing the anodes from the bath and weighing the same as has heretofore been necessary.

So far las I am aware, it has heretofore never been proposed to utilize a meter integratingt-he current and time factors on an electroplating bath for comparatively large objects as herein. contemplated, and it has,

-been proposed to utilize meters for use in plating large objects, it is likely that such practice would have followed the practice as applicable to smaller objects, and would have required the use of two meters for each bath as herein set forth. By my invention the use 0f meters is not only extended to a new field, but the manner of utilizing the same is radically changed so as to require only ay single meter in place of the plurality of meters heretofore required.

It will be apparent to those skilled in the art that the present invention is applicable to other large objects and-to the plating of such objects with other metals. In this connection reference may be made tothe adaptability of the invention to use with automobile radiator shells, bumpers, lamps and the like with protective or ornamental coatings of metals such as nickel, chromium, and cadmium, thereby aording the desired thickness of deposit per unit area of the plated article.

Certain advantages of the invention arise from the utilization of meters in the art as applicable to comparatively large objects, and more particularly to band instruments and the like, and especially meters havingv dials calibrated to read directly V,in unit weights of the metal deposited.

Other advantages of the invention arise from the revision-of means in a plating operation o the character herein contemplated whereby the actual amount of gold or other.

metal utilized during any period, or over any time interval, may be quickly and accurately determined without the necessity of actually weighing the anodes.

Still other advantages of the invention arise from the provision of a meter for use with gold cyanide baths having its dial graduated to read directly in unit Weights of gold.

Still further advantages arise from the method of determining dial readings for a meter as referred to by arranging the usual graduations as used for amperehours on the basis of vone amperehour being equivalent to substantially 4.728 of ennyweights of gold with a 100% plating e ciency.

I claim:

1. In an electro-plating system, the combination of an electro-plating bath, an anode and a cathode therein, a source of electromotive force connected to the anode, and a meter for indicating the amount of metal deposited at the cathode in accordance with the current traversing the cathode, of electrically operated means for interrupting the electrical circuit including the bath after a predetermined amount of metal has been deposited, the circuit interrupting means being so connected to tuating the interrupting means.

2. In an electro platlng system, a plurality of plating baths each containing at least one comparatively large object to 'be plated and constituting' a cathode, at least one anode in 'each bath, a. circuitincluding said anodes, means efl'ective while the anodes are in position in their respective baths 'for indicating,r the amount of metal deposited on the articles, and means controlled by the indicating means for separately interrupting the plating current ol" any bath when a predetermined amount ot' metal has been deposited therein.

3. In anelectro plating system, a plurality of plating baths each containing an object to be plated and constituting a cathode, at least one anode in each bath, a circuit includingr said anodes` means effective while the :modes are in position in their respective baths for indicatingr the amountI of metal deposited on said objects, and electrically controlled means l'or separately interrupting the plating eurrent of any bath when a predetermined amount ot` metal has been deposited'thereon.

In testimony whereof I have hereunto' set my hand.

LAWRENCE C. TURNOCK.

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