US2349662A - Electroplating cell - Google Patents

Description

May 23, 1944. T. J. KEA'IY'ING 2,349,662

. vELECTROPLATING CELL Filed Jan. 8, 1941 2 Sheets-Sheet 1 flrsulal/'orz WITNEssEs; 2

May 23, i944. T. J. KEATING yELEC'1.R(`)PI.|A'1ING CELL Filed Jan. s, 19'41 2 Sheets-Sheet 2 INVENTOR i d gy. w a, A z 5 4 fn .a 4 4 U4 J. @u vf q wmf Il a Y lllll E f A m f 4 0. my. f,

Patented May 23, 1944 ELECTROPLATING CELL Thomas J. Keating, Bloomfield, N. J., assigner to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application. January 8, 1941, Serial No. 373,545 s claims (o1. .2M- 252) This invention relates to electroplating baths, and more particularly, to sludge retainers for use in connection with anodes.

In order to provide for bright and clean electroplating work, it is required that the bath be `free from colloidal suspensions and other mestruction of the fabric lbags and necessitated their frequent replacement.

The object of this invention is to provide for a durable metallic sludge retainer for anodes.

Other objects of the invention will be obvious and will, in part, appear hereinafter as disclosed by the specification and drawings.

Reference should be made to the accompany ing drawings, in which:

Figure 1 is a top plan view of the general assembly of an electroplating bath;

Fig. 2 is a section on lines Il-II of Fig. 1;

Fig. 3 is a section on lines III-III of Fig. l;

Fig. 4 is a section taken along lines IV--IV of Fig. 3;

Fig. 5 is a section taken along lines V--V of Fig. 3; and

Fig. 6 is a partial section taken along lines VI-VI of Fig. 5.

It has been found that by localizing any sludges and solids present in the electrolyte about anodes which are prone to sludge during operation of an electroplating bath, the detrimental eiect of the sludge is substantially elimlnated. In particular, the placing about the anodes of a screen having a sufficiently fine mesh will ensure that all of the sludge deposited by the anodes will be retained and prevented from contaminating the work being electroplated.

It has been found that sludge retainers made of fine metal screen or fabric have qualities which make them especially desirable for localizing the sludge about the anode. The necessary fundamental properties of the metal ernbodied in the screens are that the metal be inert in the electrolyte used for the electroplating bath. Furthermore, due to the fact that the surface of the electrolyte is in contact with oxygen and other gases of the atmosphere, which may cause increased chemical activity, the metal inthe sludge retainer therefore should have characteristics which render it also inert to the more active surface portions of the bath.

It is well known that anode covers of ordinary cellulcsic materials frequently fail at a point a short distance above the surface of the electrolyte by reason of the evaporation of the electrolyte carried above the surface on the material by capillary action. Highly corrosive crystals of chemicals result from this evaporation. Accordingly it is a further required qualification for the metal used in the retainer that it be unharmed by crystals of chemicals resulting from evaporation of the electrolyte.

From the operating standpoint of an electroplating bath. it is desirable that sludge retainers be both easily applied to the electroplating bath about the anodes and be readily removable. In many instances, it is particularly desirable that the sludge retainer not interfere with the removal and addition of anodes as the anodes are plated out or changed, The prior art sludge bags had to be tied and untied by hand about each anode.

A commercially satisfactory sludge retainer should be so constructed that it can be easily cleaned of the sludge deposit present therein without the use of any special tools or equipment.

A further requirement is that the retainer should not waste any current or interfere with the plating operation.

The sludge retainer described herein and shown in the several gures of the drawings meets the various requirements listed hereinabove.

yThe metal which is suitable for use in any plating bath depends on the chemicals present by Various electrolytes is well known in the art and no extensive list of the metals suitable for results.

the various electrolytes is given other than those above.

Referring to Figure 1 of the drawings, an electroplating tank Il] including eight sludge retainers is shown. The electroplating tank consists of a large receptacle I2 composed of a treated wood body with an internal lining of lead or other resisting metal. Anode conductor bars I4 are disposed on either side of the cathode conductor bar I6 on which the articles to be plated are hung. The anode bars I4 support, a plurality of anode hangers I8 which carry the anodes 20. The eight sludge retainers 22 hang from the anode bars by means of hooked supports 24. Insulating pads 25 prevent current flow into the sludge retainers 22 from conductor bars I4.

Referring to Figs. 2 and 3 of the drawings, there are shown the front and back views, respectively, of a sludge retainer 22. The sludge retainer consists of a bottom sludge pan 26 which is substantially imperforate. Attached to the upper edges of the pan 26 is a main front screen 30 which extends about both ends and the side of the retainer which is directed toward the object being plated. A second back screen 36 is attached to the side of the pan remote from the cathode. As shown inthe drawings, the screens do not extend up to the` surface of the electrolyte but terminate a short distance below the surface. A substantially imperforate rim member is attached to the upward extremities of the two screens and extends above the surface of the electrolyte. It is believed that an imperforate rim memberv 42 having considerable thickness would be somewhat more resistant to the intensified strength -of the electrolyte at the surface than would a 'ne wire mesh screen. The hooked suspension members 24 for the retainer are preferably attached to the pan 26 and the upper rim member 42.

Referring to Fig. of the drawings, a more detailed view of the construction and related parts of the sludge retainer 22 is shown. The pan member 26 includes a double thickness rim 28 produced by folding over its edges. This double thickness rim is provided with tapped holes 29 for the purpose of supporting the wire mesh screens.

Ihe wire mesh screens 30 and 36 have been made of 180 mesh 18-8 stainless steel for use in'zinc cyanide plating solutions with satisfactory Screens woven to this fine mesh have been found to be suflicient to function by themselves to substantially prevent passage of sludge.

VThe screen 36 is placed within a framework 32 which consists of a formed U-shaped member clamped about theedges of the screen. Retaining machine screws 34 passing through the frame member 32 engage in the tapped holes 29 in the .rim 28 of the pan. The rear screen member 36 is also supported by means of a rectangular U- shaped frame 38. Machine screws 40 provide for the attachment of screen 36 to the pan.

A suitable construction for the upper rim member which is partly within the electrolyte and partly exposed to the atmosphere, is best shown in Fig. 5. The rim member consists of a continuous strip of metal 42, the lower edge of which is doubled over in order to provide a rim 44 with tapped holes 45 for receiving screen retaining machine screws 34 and 40. A channel 46 is welded or otherwise attached to the upper edgev of the rim member 42 for reenforcement. In addition, as shown in Fig. 6, the front corners of the rim member 42 are reenforced with round bars 48,

while the rear corners of the rim member are reenforced with square bars 50.

The suspension members 24 are attached by means of welding to the upper rim member 42 and the pan member 26. Other means of attaching the suspension members 24 to the sludge retainer body may be employed. The insulating pads 25 prevent :How of current through the retainer. 'I'he operating efficiency of the plating unit will be decreased if current is permitted to pass through the body of the retainer 22. The insulating pads 25 may be of rubber, phenolic resins or other suitable dielectric materials. While the insulators 25 are shown as attached to anode bars I4, they may be attached to, or made part of, the support 24, thus requiring no care in suspending the sludge retainer on the anode conductor bar. All or part of the support 24 may be made of a dielectric material. It would be feasible, in some instances, to provide insulated supports separate from the anode conductor for suspension of the sludge retainer 22, thus rendering the insulator pads 25 unnecessary.

The rear screen 36, with its reenforcing frame 38, is readily removable from the retainer by removing the several machine screws 46. Only a few machine screws 40 are necessary for properly supporting the screen 36 and its removal is a simple operation. Due t0 thefact that the sludge retainer is a deep and narrow basket, the problem of removing sludge therefrom is greatly simplified by providing the removable back screen 36.

The sludge retainer 22 may be taken out of the electroplating bath at any time that the sludge accumulation therein has reached the extent that the bottom pan 26 is nearly full. The anode bars 20 are removed rst from the bath, then the workman simply grasps the suspension members 24 and lifts out the retainer slowly from the electrolyte to permit the electrolyte to flow out. It is advisable to tilt the retainer slightly in order to ensure that most of the electrolyte runs out of the pan. After the retainer has been removed from the bath, the back screen 36 is taken 01T by removing the machine screws 40. A small shovel or any other convenient implement may be readily inserted into the pan and the sludge deposit taken out. Thereafter a water hose or other fluid line may be employed to clean out the screen and wash out the pan. By replacing the back screen 36, the sludge retainer is vready for use again.

It will be appreciated that the sludge retainer disclosed by the instantl invention will last indefinitely in electrolytes which do not react with the metal employed for making the retainer. By using the same metal for both screen, pan and upper rim member, no local electrolytic corrosion can take place. The retainer should last vindefinitely as compared to the customary cotton or other fabric sludge retainers. The pan is of a rigid and strong construction which will support fallen anodes, a great accumulation of sludge, and anode fragments. The relatively large amount of open area for the passage of the metallic ions fa;- cilitates electroplating. It is a simple and convenient matter to suspend the container from the,

anode bars on the anode hangers.

The retainer is more convenient than the conventional sludge retainer inasmuch as the conventional sludge retainers generally enclose a single anode. The present retainer is designed for cooperation with a plurality of anode bars. Therefore, less work is necessary to clean the sludge retainers in the present case than would be required with the greater number of sludge retainers required heretofore with the same number of anodes.

Although one form of the invention is shown and described herein, it will be understood that other changes may be made without departing from the spirit of the invention or the scope of the following claims.

I claim as my invention:

1. In an electrolytic cell including an electrolyte, anode supports, and an anode suspended in the electrolyte, the anode depositing a sludge during operation of the cell, a metallic retainer surrounding the anode for catching the sludge comprising, in combination, a pan below the anode, a rim member about the anode extending through the surface of the electrolyte, suspension means electrically insulated from the anode supports for supporting the pan and rim from the anode supports, and a ne metallic screen attached to the edges of the pan and extending upwardly and attached to the portion of the rim member below the surface of the electrolyte, the metallic screen being of a nneness suillcient to function by itself to substantially prevent the passage of sludge therethrough, the pan, rim member, suspension means, and the screen being composed of metal inert to the electrolyte.

2. In an electrolytic plating cell including an electrolyte, anode supports, and an anode suspended from the anode supports in the electrolyte, the anode depositing a sludge during operation of the cell, a metallic retainer surrounding the anode for catching the sludge comprising, in combination, a pan below the anode, a, rim member about the anode extending through the surface of the electrolyte, suspension means electrically insulated from the anode supports attached to the pan and rim member for supporting the retainer from the anode supports, and a metallic screen attached to the edges of the pan and extending upwardly and attached to the portion of the rim member below the surface of the electrolyte, the metallic screen including a panel portion removably attached to the pan to provide for removal of sludge deposited in the pan, the metallic screen being of a ineness sufficient to function by itself to substantially prevent passage therethrough of the sludge, the pan, the rim member, suspension means, and the screen being composed of a metal insert to the electrolyte.

3. In an electroplating apparatus comprising an electrolytic bath, a cathode and an anode for making deposits on the cathode, the dissolution of the anode causing a sludge about the anode, a metallic sludge retainer associated with the anode for collecting the sludge, the retainer comprising a metallic screen of suicient flneness to function by itself to substantially prevent the passage of sludge therethrough, the screen having essentially vertical walls, an imperforate metallic pan for collecting sludge disposed below the anode in cooperative relation with the screen and the sides of the pan being fitted to the screen to form an extension thereof to provide an enclosure to prevent sludge from escaping into the electrolyte outside the retainer and supporting means for the pan and screen for suspending them in the electrolyte, the supporting means including electrically insulating portions to prevent electrical current from passing to the retainer, the metallic retainer being composed of a metal substantially inert to the electrolyte.

THOMAS J. KEATING.

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