US3001925A

US3001925A - Anode structure

Info

Publication number: US3001925A
Application number: US697931A
Authority: US
Inventors: Ernest V Berry
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-02-23
Filing date: 1957-11-21
Publication date: 1961-09-26
Anticipated expiration: 1978-09-26

Description

Sept. 26, 1961 E. v. BERRY ANoDE STRUCTURE 3 Sheets-Sheet 1 Original Filed Feb. 23, 1955 Eqs/EST V' .35,92%

INVENTOR.

rroP/vey.

J ,4 5 www.. c.

s 'll- Sept. 26, 1961 E. v. BERRY ANoDE STRUCTURE 'original Filed Feb. 25, 1955 5 Sheets-Sheet 2 1N VEN TOR.

rmmvsq.

sept. 26, 1961 E. v. BERRY 3,001,925

ANODE STRUCTURE Original Filed Feb. 25, 1955 y 3 Sheets-Sheet 3 E//Q/S/Esr yeeey,

1N VENTOR.

rrae/VE United States Patent 697,931 4 Claims. (Cl. 204-224) The present invention relates generally to the field of electroplating or electrodepositing, and more specifically to an anode structure which is particularly well adapted for plating journals of large diesel engine crankshafts with hard chromium, nickel or otherAwear-resistant metals or alloys thereof.

, A'Ihis application is a division of my co-pending applica tion Serial No. 489,968, liled Febru-ary 23, 1955, now abandoned.

The primary object in devising the present invention is to provide an anode structure that rotatably engages or partially encircles the journal of a longitudinally disposed crankshaft as it is turned axially in an electroplating bath, with the anode being so designed that as the journal rotates it is subjected to a number of circumferentially spaced zones of predetermined maximum electrical current density. l Another object of the invention is to provide an anode structure adaptable for use in electroplating journals of varying widths, and one that permits the rapid deposition of hard chromium or nickel thereon at a relatively rapid rate without cracks or fractures developing thereon caused by internal stresses in the deposited metal.

-A further object of the invention is to furnish an anode structure by means of which the cylindrical surface being plated is subjected to a sequence of circumferentially spaced zones of maximum and minimum current density, which zones at all times are retained at a predetermined position with respect to the surface of the plated metal whereby a metallic layer of uniform texture and physical characteristics is obtained.

Another object of the invention is toprovide an anode structure that permits electroplating at a relatively high rate of deposition and high current density, with a minimum of trivalent chromium formation when the conventional chromic acid bath is employed.

A further object of the invention is to provide an anode structure of such design that during plating ofthe journal it is subjected to an undulating electrical current in which the surface being plated is sequentially subjected to zones of maximum and minimum intensity, with the anode at all times being held in a tixed position relative to the journal on which metal is being electrodeposited.

A still further object of the invention is to provide an anode structure so designed that minute cracks or ssure imperfections which may exist in the journal surface, or that develop in the electrodeposited metal are immediately lled by the electrically deposited metal, which metal in turn so bonds to the side walls of the crack or fissure as to provide a solid integral layer of electrodeposited metal of uniform physical characteristics.

Yet another object of the invention is to provide anode structures that are interchangeable one with the other whereby a used anode can be replaced with a new one having a fresh clean surface free of oxide or other foreign, 'electrical insulating materials, and thus obtain full utilization of the electrical energy for plating purposes, rather than dissipating a portion of this electrical energy in overcoming the resistance thereto built up by deposited oxide or foreign materials on the exterior surface of the anode structure.

Still a further object of the invention is to supply lan anode structure in which the circumferential spacing of the zones of maximum electrical current density can be varied, as well as the total anode area exposed to the plating bath, in order, that the ratio between the anode and cathode areas is maintained suiciently high to prevent appreciable formation ofv trivalent chromium during the plating operation.

Yet a further object of the invention is to provide an anode structure that is so rotatably supported on the journal being plated that electrical insulating shields forming a part of the structure are disposed adjacent the interior surfaces of webs or arms supporting the crank pins, which construction prevents plating of fillets provided at the junction of the pin and webs being plated without the necessity of masking the lillets.

Still another object of the invention is to provide an alternate anode structure of such design that oxygen evolved from the anode during plating passes upwardly over the cathode, with this upward flow of oxygen serving to remove hydrogen from the cathode and minimize embrittlement of both the steel journal as well as ,the chromium layer deposited thereon.

Yet still another object of the invention is to provide an anode structure on which insulating shields may be mounted to prevent plating of any one of the forms of illets normally associated with crankshafts, without danger of the webs supporting the crankshaft pins inadvertently engaging the insulating side shields and displacing them from the anode structure.

These and other objects and advantages of the invention will become apparent from the following description of the preferred and alternate forms of the structure, together with the method of fabrication thereof and manner ofuse in electroplating'of crankshaft journals, particularly when chromium is the metal being deposited thereon. Y l l,

FIGURE l is a side elevational View of a crankshaft horizontally and rotatably disposed in a plating bath, showing the journals thereof rotatably supporting the an# ode structure of the present invention;

FIGURE 2 is an exploded perspective View of one form of the anode structure that envelopes substantially the upper end portion of the Vjournal on which it is ro-` tatably supported;

FIGURE 3 is a side elevational View of one of the anode structures shown in FIGURE 1, taken on line 3-3 thereof;

FIGURE 4 `is an end elevational view of the anode structure shown in FIGURE 3; Y

FIGURE 5 is a vertical, cross-sectional view of the anode structure shown in FIGURE 3, taken on line 5 5 thereof;

FIGURES 6a, 6b, and 6c are fragmentary Vertical, cross-sectional views of the lower portion of one of the anode shields showing the manner in which the three types of fillets normally associated with crankshafts are shielded from the plating bath;

FIGURE 7 is a diagrammatic view illustrating'th method by which the electrical conducting portion of the anode structure is fabricated and may be adjusted to the particular width of the journal to be plated;

FIGURE 8 is a vertical, cross-sectional View of the second form of the invention in which the conducting portion thereof encircles substantially the lower portion of the journal being plated, with the journal being concur.- rentlysubjected to the wiping action of both hydrogen and oxygen bubbles as discharged from the plating solution; i

FIGURE 9 is aperspective view of the rotatable support shown in FIGURE 8 which rotatably supports the electrical conducting portion of the anode structure from the journal being plated; and v FIGURE 10 is a diagrammatic view showing'the man2 ner in which the surface being plated is subjected to an undulating electrical current of maximum and minimum current density.

Referring now to FIGURE l, for the general arrangement of the invention, it will be seen that a crankshaft C .iS horizontal in an electroplating or electrodepositing bath B, and rotatably supported between two vertically disposed iianges F and F. The journals of crankshaft C rotatably support a number of anodes A that will hereinater be described in detail. Flange F is aflixed to a Shaft that is rotatably supported from a suitable framework (not shown) which forms no part of the present invention. Flange F is also supported from said framework. The detailed structure of the framework and the manner by which a sprocket 12 affixed to shaft i0 is driven by an endless chain belt 14 to rotate crankshaft C is shown and claimed in my Patent No. 2,782,159, issued February 19, 1957.

The structural details of anode A may best be seen in FIGURES 2 to 7, inclusive, and includes two laterally separated parallel side pieces 18 and 18', each of which side pieces is generally crescent-shaped. Inasmuch as the structure of the

side pieces

18 and 18 are identical, for convenience herein only one will be described in detail with like parts of the other side piece being identified by the same numerals used relative to side piece 18 but to which a prime is aflixed. Side piece i8 has a central portion 20 from which two legs 22 and 24 extend downwardly below the center of rotation `of the journal I on which the anode A is rotatably supported. The inner edges of legs 22 and 24 below the center of the longitudinal axis 28 of the journal are substantially vertical, the reasons for which will be explained in detail. A plurality of ribs 30 and 30' respectively are provided in side pieces 18 and 18', which ribs extend inwardly to junction points 32 (FIGURE 2') where the free ends of the ribs are joined to one another as by fusing.

In describing the construction and operation of the anode A, it will be assumed that it is being used .in conjunction with a chromic acid ybath in applying a layer of hard chromium to the exterior surface of a journal J of a crankshaft C. As is well known in the practice ,of electroplating, an insoluble anode is employed, and thereforethe side pieces 18 and 18' and ribs 30 and 30' thereof Iare fabricated from a lead-antimony alloy or an alloy of lead and tin.

Side pieces

18 and 18 have two circumferentially spaced

cross pieces

34, 36 and 34', 36' that extend upwardly therefrom, and have free in ner portions which are fused together. Two rigid

electrical conductors

38 and 40 project upwardly from cross ,pieces 34, `36 and 34', 36' to which said conductors 4are aixed as by fusing `or other conventional means, whereby the cross pieces and conductors are electrically connected with a minimum of resistance at the junction points.

The exterior surfaces of

electrical conductors

38 and 40 are encased by tubular electrical insulators 38' and 40' (FIGURE 2). A horizontal rigid bar 42 is longitulinally supported over bath B by means not shown. A number of horizontally disposed U-shaped members 44 are mounted on the sides of bar 42, which members define spaces of such length that

electrical conductors

138 and 40 are slidably mounted in upwardly extending positions within the contines thereof. U-shaped members 44 serve to maintain conductors 3S and 40 in generally upright position, without restricting slidable movement thereof relative thereto when anodes A with which Ythey are associated are pin journals of the crankshaft C. [Ihe structural details of the means by which the rigid bar 42 is supported lengthwise over the bath B are shown in said Patent No. 2,782,159.

To prevent settling of foreign materials from the sur Vface of the bath B onto the `anode ribs 30 and 30', each anode is provided with a shield 48 in the form of.a11 elongate strip of electrically insulated material, such as .one-of the numerous synthetic vplastics that are adapted to withstand an elevated temperature as well as the corrosive action of chromic acid. Two openings 50 are provided in shield 48 through which the

electrical insulators

38 and 40 pass. Shield 48 extends in opposing direc tions from insulators 38', .40' over the open space exist ing between side pieces 1 8, 1 6', and rests on a. number of longitudinally' spaced, transverse, electrically insulated spacers 52, as seen in FIGURE 2. The free ends of shield 48 lap 4over the `lower extremities of side pieces 13, i8', and are rigidly affixed thereto by conventional means. Two elongate cylindrical rollers 6i), 60 fabricated of an electrically insulated material are transversely disposed between the interior surfaces of side pieces '13, 18. These rollers are rotatably supported on two transversely disposed shafts 62, 62'irespectively, the end portions of which are mounted in bores provided therefor in side pieces 18, 18'.

Two horseshoe shaped side shields 72 and `72 are provided for each anode A, and each of these shields i11- cludes two curved downwardly depending legs 68, '7 0 and 68', 70' that cooperate with the central shield portion to deiine two 4inner curved

circular recesses

74, 74 which encompass more than 180 of the journal I when movably mounted thereon. Horseshoe

spacer members

76, 76 are bonded to the exterior surfaces of shields 72, 7,2' respectively, uthe 4inner edges of which spacer members also serve to define the circular recesses 74, 74'. It will be noted `that spacer members 76, 76' are of -the same configuration as the side shields but considerably smaller in diameter. The =lowe r extremities of the

side shields

72, 72 and '76, 76 curve inwardly slightly, for reasons that will hereinafter be outlined.

When the shields and spacers are `in slidable androtatable contact rwith a `journal I they deline spaces S and S' on `the outer edge portions of the journal that are protectively masked thereby from action of the `plating bath.

vDue tothe fact that Vrecesses 74, 74 in each side shield has a partial circumference of greater than 180, legs 68, 7i) and 68', 78' thereof are momentarily deformed into axially separated, `vertically extending planes at -the time the shields are removably mounted on the journal I. The plastic material forming side shields 72, 72' is suii' ciently resilient to permit stretching ofthe edges defining recesses '74, 74' to substantially a horizontal plane when being mounted on journal J, yet will cause the shields to assume a vertical plane concurrently with the slidable, rotatable mounting thereof in alignment with spacers 76, 76' disposed adjacentwebs 80 that support the journal.

Centrally positioned `hooks 82, 82' project upwardly from the interior faces of side shields '72, 72', which hooks are of such shape and resiliency as to enable `them to grip the interior surfaces of side pieces 18, l18' with suficient force to adhere thereto. To permit proper alignment of side shields 72, 72 on the anode A, the interior shield surfaces are provided with two

guides

84, 86 and 84,86' respectively, as may be seen in FIGURE 2. An anode A as above described may be rotatably mounted on vone o ftthe journals J (FIGURE 1) with the

conductors

38, 40 being held in a movable upwardly extending position '.withiri the contines of one of .the U- shaped members `44.

The crankshaft journal J `is formed with fillets which may assume anyone .offthe `eoinigurations shownin FIG- URES 6a, 6b or 6c. In FIGURE 6a it will be seen that a-recessed llet `is provided in which `the lower interior surface extremity of aside shield 72 extends slightly below the innermost edge of the fillet to define a partial circumferentially extending inaction line 83 that Serves to block the electrodeposited `metal laye: 8 7 therebeyond. The combined thickness of abutting spacer 76 and `side shield 72 must be such that the lower extremity of the latter is V,securely maintained inthe fillet 84 in the `position described above to extend just below the inner edge 84a.

The configuration ,of the fillet shown in FIGURE `6b permits the exterior surface of the journal I to develop into an upwardly extending curve 88, the radius of curvature of which is tangent to the interior face of arm 80. The lower extremity of side shield 72 shown in this tigure also defines the partial circumferentially extending boundary line 86 beyond which no metal will be electrodeposited from the bath B.

Another form of fillet is shown in FIGURE 6c which bows outwardly into thev lower wall portion of arm 80. In this particular instance the lower portion of side shield '72 tapers downwardly and outwardly, and is slightly deformed outwardly to del-ine a partial circumferentially extending junction line 89 on the journal J beyond which no metal will be electrodeposited.

Referring to FIGURE 3, it will be seen that the rollers 60 permit rotation of journal J, with the side pieces i8, 18 and

ribs

30, 30 extending therebetween being held on the journal in such a manner that all of the ribs embraced within the segment Z occupy fixed radial positions relative to the exterior journal surface. The density of the electrical current owing from the anode ribs Sil, 3G' to the journal, and the temperature of the chromic acid bath, have a very distinct bearing on the physical characteristics of the chromium layer `88 to be deposited on the journal. When electricial energy is supplied to one of the anodes A, and the current density between ribs 30, 36' and the exterior surface of journal I is very high, the journal will become polarized whereby metal will not be deposited thereon, yet a large amount of oxygen and hydrogen will be given off at the anode A and the journal I respectively. This excessive evolution of hydrogen is undesirable, as it may result in embrittlement of the journal, as well as of the chromium layer 88 deposited thereon. Furthermore, such heavy dischargevof hydrogen and oxygen is wasteful, for generation thereof serves no useful purpose. To permit escape of hydrogen and oxygen at as rapid a rate as possible, the shield 48 is provided that has a plurality of openings or vents El) formed thereinthrough which these gases may pass upwardly as released from the bath.

The lower end areas 90 of ano'de ribs 30, 30' located within the confines of segment Z (FIGURE 3), are so spaced from the surface of journal I with which they are associated as to establish a number of circumferentially spaced, transverse zones 92. The distance between areas 90`and the journal surface is determined by the magnitude of electrical current employed in the plating operation, with the flow of maximum current in zones 92, whereby journal I receives a maximum metallic deposit thereon with a'mim'rnum of hydrogen expulsion.

Should areas 96 be moved closer to the journal surface `than as above described, the rate of metallic deposition from the plating bath to the journal surface would rapidly decrease. Due to the presence of excessive electrical current, the journal I becomes highly polarized, with the rate of hydrogen evolution increasing as the rate of metallic deposition decreases. It will therefore be seen that the spacing between the lower end areas 90 of the anode ribs is critical in obtaining a maximum metallic deposition from the plating bath with a minimum discharge of hydrogen at the journal surface.

j ri'he exterior surfaces of the anode ribs Sii, 31 are all at the same electrical potential, and as aresult, the facing

sides

98 and 100 of each two adjacent ribs within segment Z, as may be seen in FIGURE l0, establish an elongate zone 102 in the bath that extends downwardly therefrom to the 'surface of the journal -J being-plated.

A s pointed out above, the intermittently spaced zones 9 2 of maximum current density are of utmost importance in chromium plating cylindrical surfaces such as the journal J. It is well established that by means of a conventional chromic acid plating bath the metal is only deposited on the cathode after a cathode film has been cstablished therearound. However, while the existence of such a cathode film is known, the exact composition thereof is not known, but is'believed to be composed of a d dispersoid-containing trivalent and hexavalent chromium?, oxygen and hydrogen. lSuch a film has an iso-electric point of 6 on the pH scale, with the dispersed particles being positively charged and moving toward the cathode so long as the lilm is maintained below said iso-electric point.

When the cathode film is subjected to a high current density for a prolonged period of time, the pH value thereof appears to increase above its iso-electric point, at which time hydrogen is freely evolved from the cathode with but little or no metal being deposited thereon; The circumferentially spaced anode ribs 3d, Sii establish the circumferentially spaced zones 92 in the plating bath that are maintained at the maximum current density for the particular current employed whereby each transverse section of the journal I during rotation thereof is sequentially subjected to these zones, but not for a suiiiciently long period of time to permit the cathode film covering these sections to rise above the iso-electric point at which the plating action ceases.

It will be particularly noted in FiGUlhE 3 that as a metallic layer 88 is deposited on the surface of journal J', fthe rollers 6i) are rotatably supported on the deposited layer, and the end areas 9i) in that portion of the

anode ribs

30, 30 Within segment Z are moved upwardly at a rate in direct ratio to the rate of this metallic deposition. On those occasions when metal is deposited as a layer that will ultimately be one-sixteenth to three-sixteenths of an inch in thickness, this upward movement within segment Z is of importance, for otherwise the spacing between the ends 90 thereof and the exterior surface of the deposited metal could decrease.

In certain plating applications, where the metallic layer deposited is very thin or the metal employed does not have the critical plating characteristics of chromium, a num'- ber of ribs 30 can extend below segment lZ, as shown in FIGURE 3. However, when this rib arrangement is employed on the anode, the distance between the metal and end areas 90 of the anode ribs decreases as a deposited metallic layer builds up on the journal i. By extending the anode ribs below segment Z a high area ratio between the anode surfaces and the cathode surface of the journal is provided. From experience it has been found that formation of trivalent chromium in a chromic acid bath is held to a minimum when a relatively high ratio is maintained between the anode and cathode areas. Thus, the disadvantage resulting from the `downwardly extending ribs above described is olf-set to a large degree by the high anode-cathode ratio provided by this construction.

An increase in trivalent chromium in the chromic acid plating bath is highly undesirable for as it increases, the electrical resistance of the bath is also increased with a resulting increase in the temperature of the bath when an electrical plating current of the same magnitude con-V tinues to pass therethrough. Inasmuch as electrical curf rent density and the bath temperature are both critical factors in obtaining the desired layer of electrodeposited chromium of uniform physical characteristics, the presence of-trivalent chromium in amounts of wide variation during the plating operation is most undesirable, as is any appreciable deviation of the ratio between the chromate ions and sulfate ions in the chromic acid bath.

Ultimately, after prolonged use, all or portions of the electrical conducting surfaces of the anode A, which includes the

side plates

18, 18 and the ribs 30, 3G extending therebetween, are covered with lead oxides and chromates. When these oxide and chromate coatings, which are relatively poor conductors of electrical energy, form on the anode they act as electrical insulation against free iow of electrical energy from the anode to the journal, which resistance causes an undesirable rise in the tempera! ture of the bath. However, the greatest disadvantage of these irregular or uneven oxide and chromate coatings on the faces of

ribs

30, 30 resides in the fact that the anode surfaces are partially shielded by this insulating material 7 effects an irregular Vflow pattern olf eleotroal .energy from the anode to the journal.

'Removal of this oxide-chromate material from the anode exterior is diicult for it is of a hard, ybrittle nature and adheres tightly to the anode surfaces. Inasmuch as the anode is fabricated from a relatively soft lead-anti- Vmony or a ,lead-tin alloy it is a tedious, time-consuming roperation to strip such coatings from `the anode without doing irreparable damage to the anode. Cleaning Aof anode suifaces, and formation of anodes A identical vin .configuration may be accomplished by casting the tv/ o halves and fusing the inner edge portions together as an integral unit, as shown in FIGURE 7. T o cast the anodes a suit able container 1li) is provided which is heated from a source 112, and lead alloy in the form of used anodes is deposited in the container. As the used anodes melt in the container 110, any foreign material such as oxides and chromates as may have been on the .outer ,surfaces thereof will rise to surface of the molten metal 114 as Aa film 115 from where it may be skimmed off. After the ijlm 113 of foreign material has been separated from the molten lead alloy lit-i it is poured into molds (not shown) to provide the anode halves illustrated in step B in FIG- URE 7. Each of the anode halves so cast includes a side plate 18 from the inner face of which ribs 350 project.

Ribs 30, 3d' are suiiiceintly long that were they to be joined at their adjacent ends', the resulting anode would be at least as wide as any of the journals J on which it is normally used. In making up a particular anode, the `width of the journal on which it is to be employed is first determined and the surplus lead is removed from the outer end portions of the ribs 3o, 30' to provide an anode A of the desired width when the ribs are fused together (FIGURE 7). After the ribs are joined,

conductors

38 and 40, .together with the electrical insulating tubular members 3 8' and .46' are fused to the electrical conducting portion of the anode, as previously described in detail.

The shield 4S is then mounted on the electrical conducting portion of the anode A and :the side shields 72 `and 76 mounted thereon after the anode is positioned on the journal I preparatory to the plating operation. It will be apparent that the rollers 60 must be mounted on shafts 62 and 62 (FIGURE 2) before the anode is used for plating. Shafts 62, rollers 60, shields 48, and supporting members 52 are all fabricated from a plastic material, and are removed from the electrical conducting anode portion before a used anode is melted for -recasting After anode A is placed in the plating bath in a supported position on one of the journals J, the anode may be continuously used until the exterior surfaces thereof become suticiently coated with oxides or chromates that ecient dow of electrical energy therefrom to the journal I is adversely affected. The process of casting the anodes A as above described not only assures the fact that the anode surface will be clean and free of all electrical nsulating materials, 4but provides an anode of uniform physical characteristics of identical `structure as that previously used.

Another form of anode structure A is shown in FIG- URE 8, the electrical conducting portion 120 of which is disposed under the journal I to be plated. This form of anode is particularly well adapted for use in chromium plating, as the oxygen evolved from the anode moves upwardly in the form of bubbles over the journal and tends to remove any bubbles o f hydrogen adhering to the surface of the cathode being plated. Normally a heavy hydrogen expulsion occurs from tho journal during plating, but avery large quantity of minute hydrogen bubbles adhere to the journal surface which effectively insulate this surface and prevent even plating thereof. The tendency of these bubbles to adhere to the cathode sur face is so great that normally they cannot be displaced therefrom by even the most violent mechanical agitation means. However, it has been found that if, when the oxygen is evolved from the anode, it is allowed to wash Cii over .the journal surface being plated, Vthe oxygen bubbles tend .to coalesee with the minute hydrogen bubbles clinging thereto and draw same therefrom.

The anode A ,embodies ,a rotatable support, as shown in FIGURE 9, which includes two laterally spaced, parallel, rigid rectangular side members 121 and 121', the end portions of which are connected by two rigid cross pieces 122 and 122'. Two iransverselongitudinally spaced

shafts

124 and 124 extend between side members `121 and 12115, and elongate

cylindrical rollers

126 and 126 respectively are rotatablymounted on these shafts.

Cross pieces

122 and 122 are provided with central, vertically disposed bores 128, 128' respectively, which receive the lower portions of two elongate vertical insulated conductors 136,136'. VShafts 124, 4124' and roller 126, 126' `are fabricated .from electrical insulating material such as one of the commercially available synthetic plastics.

The exposed lower ends of conductors 130, 130' are fused or otherwise atrxed to horizontal end pieces 134, f3.4 extending between two laterally separated side pieces 136, 136' of generally semi-circular configuration. A number of radially disposed ribs 138 extend between side pieces 136, 136', which ribs .are preferably formed integral therewith in the same ,manner as that of ribs 30, 30' and side pieces 18, 1S of the preferred form of the invention. lt Will be noted that ribs 138 are so positioned that oxygen evolved at the anode A during plating will tend to move from the anode `ribs to be discharged onto the journal surface being plated. In common with the preferred anode form previously .described in detail, ribs v138 are also so located as to form zones 140 of maximum current density separated from one another `by zones 142 of minimum current, both of which zones are in the plating bath. Thus the plating elfect obtained by the alternate form of `anode A is the same as that achieved by anode A, except that the zones of maximum and minimum current density are disposed on the lower surface of journal J.

With the anode A', the spacing between the inner end surfaces 13811 of the ribs, and the outer surface of the metallic layer plated on the journal J constantly decreases as the thickness of the layer increases, and for that rea son the electrical conductors 130, 130' are supported for vertical adjustment on cross piece 122. This adjustment may be accomplished by a number of means, as by the collars 143, 145' shown in FIGURE 8. Should it be found desirable, a curved elongate strip shield 146 of electrical insulating material may be removably mounted on the outer edges of the curved side pieces 136 as shown. The material from which shield 146 is fabricated is resilient in nature, and to a degree that when the ends thereof are curved to form inwardly extending portions 148, they grip the cross pieces 134 with sufiicient force to maintain the shield in place on the anode portion 12.0. The

insulated conductors

130, 130 are so spaced that they are maintained in an upwardly extending position when slidably mounted within the contines of the U- shaped member 44 shown in FIGURE 1.

Anode A' has been found to provide advantageous plating results in that it is disposed at a lower elevation in the plating bath than anode A, and because of its greater depth in the plating bath, both the hydrogen and oxygen bubbles evolved during plating are under greater compression and therefore smaller in size. Due to their smaller size, the detrimental insulating elect of the bubbles adhering to the cathode and anode surfaces is minimized for they cover a smaller surface area.

Although the anode structures, the method of fabricating same, as well as the method of using the anodes previously described in detail has been found to provide quite satisfactory results, it is to be understood that these concepts are merely the presently preferred embodiments hereof, and that it is not meant to limit the invention to the details of structure herein shown and described, other than as dened in the appended claims.

I claim:

l. An anode structure for use in chromium electroplating a cylindrical cathode surface in a chromic acid electrolite, which structure includes a plurality of circumferentially spaced, electrical conducting anode ribs capable of being so disposed as to encircle a major portion of said cathode surface when positioned longitudinally relative thereto, said anode structure being characterized by: two crescent-shaped side pieces formed of an electrical conducting material that are disposed on opposite ends of said ribs and bonded thereto, said side pieces serving to hold said ribs in said circumerentially spaced relationship, and cooperating with said ribs to increase the `anode-cathode surface ratio to minimize the formation of t-rivalent chromium during said electroplating operation; two parallel spaced shafts extending between said end pieces; two rollers rotatably mounted on said shafts, said rollers rotatably engaging said cathode surfalce land supporting said anode ribs and side pieces at a fixed distance therefrom; an electrical conductor extending upwardly from said ribs and side pieces and electrically connected to said side pieces; two horseshoe-shaped side shields formed from a non-electrical conducting material that abut against the outer surfaces of said end pieces, the inner edges of which side shields are in rubbing contact with said cathode surface, with said shields limiting the area of said cathode surface to be electroplated; and means on said side shields that engage said side pieces for removably holding said side shields on said side pieces, said side shields being separated from said side pieces by downward movement of said side shields relative thereto.

2. An anode structure as defined in claim 1 which in addition includes two spacer members formed of a nonelectric conducting material -that are rigidly ialixed to the exterior surfaces of said side shields, with the inner edge of said spacer members being in transverse alignment with the inner edges of said side shields.

3. An anode structure as dened in claim 1 which in addition includes two spacer members formed of a nonelectrical conducting material that are rigidly aixed to the exterior surfaces of said side shields, with the inner edges of said spacer members being disposed radially outward a substantial distance from said inner edges of said side shields.

4. An anode structure as defined in claim 3 wherein the inner portions of said side shields are tapered, and Said inner edges of said side shields are narrower than the thickness ofi the balance of said side shields.

References Cited in the tile of this patent UNITED STATES PATENTS 2,473,290 Millard June 14, 1949 2,539,502 Zanetti Jan. 30, 1951 2,710,834 Vrilakas June 14, 1955 2,782,159 Berry Feb. 19, 1957

Claims

1. AN ANODE STRUCTURE FOR USE IN CHROMIUM ELECTROPLATING A CYLINDRICAL CATHODE SURFACE IN A CHROMIC ACID ELECTROLITE, WHICH STRUCTURE INCLUDES A PLURALITY OF CIRCUMFERENTIALLY SPACED, ELECTRICAL CONDUCTING ANODE RIBS CAPABLE OF BEING SO DISPOSED AS TO ENCIRCLE A MAJOR PORTION OF SAID CATHODE SURFACE WHEN POSITIONED LONGITUDINALLY RELATIVE THERETO, SAID ANODE STRUCTURE BEING CHARACTERIZED BY: TWO CRESCENT-SHAPED SDE PIECES FORMED OF AN ELECTRICAL CONDUCTING MATERIAL THAT ARE DISPOSED ON OPPOSITE ENDS OF SAID RIBS AND BONDED THERETO, SAID SIDE PIECES SERVING TO HOLD SAID RIBS IN SAID CIRCUMFERENTIALLY SPACED RELATIONSHIP, AND COOPERATING WITH SAID RIBS TO INCREASE THE ANODE-CATHODE SURFACE RATIO TO MINIMIZE THE FORMATION OF TRIVALENT CHROMIUM DURING SAID ELECTROPLATING OPERATION, TWO PARALLEL SPACED SHAFTS EXTENDING BETWEEN SAID END PIECES, TWO ROLLERS ROTATABLY MOUNTED ON SAID SHAFTS, SAID ROLLERS ROTATABLY ENGAGING SAID CATHODE SURFACE AND SUPPORTING SAID ANODE RIBS AND SIDE PIECES AT A FIXED DISTANCE THEREFROM, AN ELECTRICAL CONDUCTOR EXTENDING UPWARDLY FROM SAID RIBS AND SIDE PIECES AND ELECTRICALLY CONNECTED TO SAID SIDE PIECES, TWO HORSESHOE-SHAPED SIDE SHIELDS FORMED FROM A NON-ELECTRICAL CONDUCTING MATERIAL THAT ABOUT AGAINST THE OUTER SURFACES OF SAID END PIECES, THE INNER EDGES OF WHICH SIDE SHIELDS ARE IN RUBBING CONTACT WITH SAID CATHODE SURFACE, WITH SAID SHIELDS LIMITING THE AREA OF SAID CATHODE SURFACE TO BE ELECTROPLATED, AND MEANS ON SAID SIDE SHIELDS THAT ENGAGE SAID SIDE PIECES FOR REMOVABLY HOLDING SAID SIDE SHIELDS ON SAID SIDE PIECES, SAID SIDE SHIELDS BEING SEPARATED FROM SAID SIDE PIECES BY DOWNWARD MOVEMENT OF SAID SIDE SHIELDS RELATIVE THERETO.