US2760929A - Electroplating apparatus - Google Patents

Description

Aug 28, 1956 G. A. sHx-:PARD ET AL ELECTROPLATING APPARATUS 2 Sheets-Sheet l Filed Oct. 6, 1952 INVENTORS @Me- 5h@ Aug. 28, 1956 G. A, SHEPARD ET AL 2,760,929

` ELECTROPLATING APPARATUS Filed oct. e, 1952 2 sheets-sheet 2 1N V EN TORS v I.. MQ@

United States Paten-t Oice 2,760,929 Patented Aug. 28, 1956 ELECTROPLATING APPARATUS George A. Shepard, Parma, and Richard C. Avellone, Mayiield Heights, Ohio, assignors to Republic Steel `glorporation, Cleveland, Ohio, a corporation of New ersey Application October 6, 1952, Serial No. 313,264

8 Claims. (Cl. 204-242) This invention deals with electroplating apparatus. Specifically, the invention is concerned with an improved rack to be used for electroplating hollow articles, e. g. pipe couplings.

The electroplating rack of this invention is superior to prior types in numerous respects among which is the arrangement of the anodes which are readily removable for replacement, and which are simple in construction. A special feature is the `adaptability of the apparatus to full utilization of the anodes, in that the metal of each may be essentially completely consumed while maintain ing good efficiency of electroplating operation vat all times. The rack structure is also characterized by advantageous means for receiving the work, such as tubular or other objects to be plated internally. The articles can merely be set in place without special connection or adjustment of any part, yet they are fully supported in proper relation to their internal anodes, and have eifective electrical connection in the plating circuit. In addition, the design of the rack permits free circulation of the electrolyte when the assembly is immersed, and is such as to promote maximum drainage upon its being lifted from the bath. Furthermore, the apparatus is provided with superior brackets or the like upon which the rack is supported, which brackets act to give good electrical contact, and, at the same time, prevent any side sway of the rack which might be caused by vertical or translatory motion of the assembly in the various operations of a mechanically operated plating system, or which might be caused by uneven loading or by the effects of removing or placing upon the rack heavy articles to be plated.

An object `of this invention is to provide an electroplating rack having a superior anode arrangement, wherein the anodes are simple rand yet make good electrical contact for carrying the plating current. The construction of these anodes for example, as more explicitly described below, allows easy replacement or removal of each one since they merely rest upon or over .centrally located pins which have flanges to bear the weight lof the anodes [and make good electrical Icontact therewith. By use of this lrack and anode supporting structure, the

anodes may Ibe very simple in their configuration, i. e.

they can be merely cylindnical in shape having an -axially located recess `or hole in one end. With this construction, and because the anodes tit onto their supporting pins with a slide or even 'loose tit, no careful machining of the anodes is necessary in making them up, but they may be entirely Iformed by casting or by other inexpensive methods.

Another object of the arrangement of the anodes and their support is that the anodes may be used until completely consumed or very nearly so since they merely rest upon their own base and obtain electrical contact thereby.

'A further object of this invention is the provision of superior brackets for `suspending the electroplating rack. This improved structure enables a better electrical contact to/be Vhad between the hooks on the ar-ms `of the rack and the brackets themselves. Moreover, in addition to such superior electrical contact, the construction `of these brackets in cooperation with the hooks on the arms of the rack, provides a mechanical stiiness such that no objectionable -swaying horizontally in either direction will be felt during the various movements -of the r-ack in the plating equipment or even when very uneven loads are suddenly applied as when heavy articles to be plated are placed on `or removed from the rack, e. g. iron or steel pipe couplings.

Yet another object is the provision of an electroplating rack having improved cath-ode contacts such that no clips are necessary which would entail more complex handling. The cathode contacts of this invention enable negative electrical contact to be made with the articles to be plated, by merely resting the articles `on these contacts.

Another object .of this invention lies in the provision, of a superior combination lof anode and cathode elements, making -it possible to plate articles of various sizes and to consume the complete anode by plating smaller articles at various stages 4of the operation as the Ianodes are consumed and become smaller in size, i. e. shorter and smaller in diameter. The construction further provides an insulating collar between the anode and the cathode supports of each unit whereby the articles to .be plated are kept trom making contact with the anode,

should any horizontalsliding of these articles occur. This insulating collar further provides a shielding eiect which results in a more uniform corrosion of the base of the anode, and it prevents direct treeing of metal from the negative contact tips to the anode during plating.

To these and other ends, one embodiment of the invention is described below and shown in the drawings by 'way of example of illustrating the ffeatures and principles of improvement. Referring to the drawings:

' Fig l1 is a perspective view showing an electroplating rack being supported in position at one end of an electroplating tank;

Fig. 2 is an enlarged crosssection 'view of 'one of the anode-cathode units of 1an electroplating rack;

Fig. v3 is an elevation partly in cross-section showing the details of the positive electrical connection Afrom the base lof an anode unit to the positive bus bar; and

Figs. 4 land 5 illustrate the details of the .construction of the brackets as used .in this invention.

Fig. l illustrates the embodiment yof one style of electroplating rack ias contemplated by this invention. 'Ihe electroplating operation in which such a rack may be used may involve the ordina-ry steps as used in a normal electroplating process. This type of rack would ordinarily be used in a mechanized electroplating process lin which some convenient type of conveyor support would be used to carry the rack-with articles to be plated in place thereon-from one tank to the next for the various steps involved in such a process. It is contemplated that the apparatus of this invention may be used on a commercial type of endless conveyor which is laid out in a long oval coniiguration and fwhich has -conveyor larms extending 4outwardly to reach iover a set of tanks. The tanks may be arranged `around the conveyor in a horseshoe-shaped configuration. The arms of such a conveyor are movable vertically as well as horizontally in order to lift the racks Iout of one .tank and lower them into the next of the series. -Elect-rical contact to each plating rack from the endless conveyor may be made in any convenient manner, such that -current may be caused to lilow during those operations of the process where suc-h current is necessary.

In Fig. 1, a rack 11'is shown in place at one end of a tank 13 where it Ais being supported by means of a support member which is carried` by the conveyor mechanism (not shown) by means of a rod l17. Rod 1,7 is movable vertically as indicated by the arrows, 'in order to raise or lower the rack 11 out of or into the tank 13. Also by means of the conveyor mechanism, this rod 17 is movable horizontally in order to cause the rack 1.1Y to travel along within tank y1'35 during the electroplating step of the process. When the rod `17 is in itslowest position, rack 4111, with the articles to be. plated, will be totally immersed in the solution contained in tank "113, and at this time, an electrical circuit will be completed by conventional contact mechanism (not shown) on the conveyor (noty shown). `Such contact mechanism is joined electrically to a pair of bus bars 19 and 21, which are carried by the conveyor and extend parallel to and underneath the rrod 17.

Beginning at the positive bus bar 21, an electrical circuit is carried via an insulated cable y23 to a positive bracket 25 which may be constructed of any satisfactory conductive material. This bracket Z5 is securely fastened to one end of support member115 by means of bolts Z7, and is insulated from the support member by means of an insulating material block 29. The electrical circuit is .continued from bracket 25 to a hook 31 which is the upper end of arm 33 of the two-layered rack 11. The hook 31 is insulated from the lower portion of arm 33 byv means of a T-shaped block ofy 4insulating material 35 which joins hook '3.1 to the arm 33 by being fastened securely to each of the hook 31 and the arm 33, by any convenient means, such as bolts 37 illustrated. The electrical circuit is continued from hook 31 by means -of a contacting metallic Iblock "39 which is secured to the hook 31 and which has fastened to it -a pair of positive bus bars 41. These bus bars 41 extend down the outside of rack 11 parallel to but spaced from arm 33 thereof; one bar 411 is shown broken away to reveal the block 65 more clearly. At each `level of rack 1f1 the bus bars have horizontal lateral extensions 43 which join longitudinal connecting portions 45. These connecting. portions 45 are electrically connected to the base of each anodeV unit 47 and- Inake good electrical connection therewith, as will be pointed out in greater detail in connection with Fig. 3.

The rack 11 may be constructed with any desired number of anode-cathode units depending upon the size of the articles to be plated and the size of the plating rack to be used. A rack may, o f course, be madewith any desired number of layers oftrays; for instance, for very large articles the rack may haveV only one tray or frame and only aV small -number of large anodesv (e. g. two) carried on it, or alternatively the rack may have a plurality of layers with many small anodes on each. In the rack illustrated, which has two layers, there is a plurality of these units y47 on each layer of the rack. The electrical `circuit continues from the base. ofy each anode unit 47 to the anodes 49 by means lof the construction which will be explained in detail :in connection with Fig. 2. From anodes 49, the circuit continues through the electroplating solution to the articles `51 and 53 being plated, which articles may be various sizes depending upon the size of anodes 49. The anodes 49 will be eaten away in use, and so become gradually shorter in height as well as somewhat smaller in diameter; and by using smaller size articles t-o be plated, such Vas articles l53 shown on the llower level ofrack 1'1, use may be made of the anodes without loss in eiciency in plating until the anodes are entirely consumed or very nearly so. In this way, use may be made of the entire anode material without appreciable waste.

The electrical circuit then continues from articles 51 and 53 to cathode contact bars 55 which are supported on the top of a grid-like arrangement of cross members 57 which, in turn, support the anode units 47 at the intersections of the cross members. The cathode bars are shown in Fig. 1 spaced considerably from the anode units 47 for the sake of clarity. Actually the amount of spacing may be varied, depending upon the size of articles to be platedwhich are being handled by the rack. This article size is largely determined by the size of the anode units `47, It will be observed that the spacing used in the illustrated size of anode units `is quite small (see Fig. 2). The remaining electrical circuit consists of the whole framework of rack 11 which may be made of any suitable conductive material, e. g. steel, and is made up of outer frames 59 and a central cross member 61. These frameworks 59`and 61 are securely fastened to a pair of spaced, upright arms 33 and 63 in any appropriate manner as by welding. Arm 63 completes the negative side of the electr-ical circuit by means of a hook `65 at the top which rests for. support in a bracket 67 which, in turn, is securely fastened to the other end of support member 115. In this instance, bracket 67 need not be insulated from support member 15 since the negative side of the electrical system is grounded. However, to insure proper low resistance for the electrical path, a cable 69 is connected to bracket 67 and carried to negative .bus bar 19 in any convenient manner such as that shown in Fig. l, i. e. through a hole 71 in support member 15. lFrom bus bar 119, the electrical circuit yis completed by conventional contact means (not shown) as previously described.

It will be noted that the bracket 67 is located down `from the top edge of the support member '15 an appreciable distance, while the bracket 25 is located up 'flush with the top of the support member 15. The reason for this is to polarize the rack, so to speak, or in other words to avoid the possibility of hanging a rack on the support with its hooks reversed giving the reverse `electrical connection from lthe proper one. In order to carry out this polarization of the rack 11, hook 31 is made correspondingly longer in its vertical extension above the rack than is hook 65, so that, when the rack :is in place on the support member 15, it will hang level with the arms 33 and 63 vertical. If an attempt should be made to hangthe rack 1'1 on reversed, one of the hooks 31 or 65 would not mate properly with the conre- - sponding bracket 67 or 25.

In Fig. 2, the details of an anode unit 47 are shown, as well as the details of cathode contact bars 55 and the mechanical joinder of cross members 5'7 and their relationship to Aanode unit 47. There is illustrated both a large article 51 to be plated and a small article 53, which in this instance are shown as being internally threaded pipe couplings. The articles 51 and 53 are shown in dashed lines since only one of them would be in place on the plating rack 11 at a time. The illustration of both sizes shows the practical extremes for which the plating rack 11, illustrated in the drawings, is designed.

All exposed metallic elements of the rack 11 except anodes 49 and cathode bars 55 (and a very small part of the anode-supporting structure) are coated with a protective material 73, which may be rubber or any similar inert, non-conducting material. At the intersection of cross members 57, they are joined securely to a circular washer-shaped element 75. This leaves a hole at the center in which is mounted a pin 77 which has a ilanged section 79 near the middle thereof and which also has a threaded lower section 81. There is a conductive material cap 83 which has an internally threaded recess 85 adapted to receive the threaded lower section 81 of pin 77 and into which lower section 81 is screwed, in order to secure pin 77 and the other elements of anode unit 47 in place. Pin 77 may be constructed of steel or a similarly rugged material, and carries on its external surface a coating 87 of lead which facilitates the effecting of good electrical contact with anode 49 andis relatively inert to the electrolytic and other chemical operations involved in use ofthe rack.

The anodes 49 will be composed of whatever metal is being used in theplatiug process, e. g. zinc, and these anodes are constructed in a conveniently simple shape, i. e. a plain cylindrical form with a hole 89 axially located in the bottom of each. A special benet of the rack conavecinan struction shown is that these anodes need no machining but may be cast to shape since hole 89 slides over pin 77 in an easy sliding fit, or even a loose fit. The electrical contact surface which is necessary is largely that on the bottom of each anode where it rests on ange 79 of the anode pin 77. The pin 77 in each case is secured in place in a manner which keeps it insulated from cathode contact bars 55 and from the framework of the rack 11. There is a washer 91 of insulating material which iits under, the lower side of ilange 79, and a cup-shaped insulating device or collar 93 upon which washer 91 rests, and which, in turn, rests on the top of another washer 94 to provide space between the bottom of the cup-shaped insulating device 93 and the top surface of the circular washershaped element 75 which is covered by protective layer 73. The space thus provided allows the free operation of a number of drain holes 95 so that the cup may be drained of the uids ofeach bath when the rack is lifted out. There is an additional insulating material washer 96 located below the circular element '75, which serves to insulate the cap 83 from the frame of the rack 11 as Well as to maintain the lower section 81 of pin 77 centrally located in the hole in circular element 75. These elements are all securely held and maintained in their relative position by the action of the flange 79 and the lower threaded section 81 of the pin '77 which is screwed into threaded recess 85' of cap 83. The electrical circuit for the negative side is carried from cross members 57 to cathode contact bars 55 by means of machine screws 97. The` positive electrical circuit is carried via the cap 83 or" each unit 47 tothe bus bar 45. The caps 83 are preferably made of brass and may be secured to the bus bar 45 in any convenient manner which will give a secure fastening with good low electrical resistance, e. g. by being brazed as at 99. The bus bars 45 may be constructed of any good electrical conductor, such as copper.

The cathode contact bars 55 are preferably shaped as illustrated in Fig. 2, having the top surface 100 upon which the pipe couplings or other articles being plated are to rest, sloped downward somewhat toward the anode for a self-centering er'ect on the article being plated. This same upper surface 100 is knurled to provide better electrical contact to the article as well as to prevent sliding. These contact bars 55 are preferably made of Monel metal or nickel plated brass but may be other satisfactory conductive materials.

Fig. 3 illustrates the anode electrical circuit connection from each bus bar 45 to the cap 83 from one of the vertical bus bars 41. As mentioned in connection with the framework of rack 11, exposed metallic portions of the anode electrical circuit also will be coated with some protective material 73 which may be rubber or a similar protective coating. This protective coating 73 will be built around the base of each anode unit 47, e. g. by covering the cap 83 and the brazing fillet 99 in order to seal the anode connection to the pin 77 as well as its connection with positive bus bar 45. Such protective coating will preferably in every case be made to be continuous for all metallic parts which are to be immersed in the electroplating solution, with the exception, of course, of the anodes 49 and the cathode bars 55.

Figs. 4 and 5 illustrate the details of the advantageous construction of brackets and 67. Since these two brackets are alike, only one will be described. In each case, the body of the bracket has a ange section 101 which has holes 103 drilled therethrough for attaching each bracket to support member 15. The body section 104 is rectangular in shape and contains a recess 105 extending all the way through from top to bottom which receives the straight extremity (i. e. the downwardly turned end portion) of either hook 31 or 65 of the rack 11. j Recess 105 is shaped so as to correspond to the crosssectional configuration of the straight vertical extremity of each hook 31 and 65 which in this case is rectangular. By these means, no appreciable horizontal motion of the rack 11 laterally or longitudinally will be possible. There is a wide angle knife edge portion 107 on each bracket which supports the hook 31 or 65 as the case may be and which serves to provide improved electrical contact with each hook since only a relatively small area comes in contact with the hook in each case. It is the mechanical pressure that is increased by this small area contact which, in turn, provides good electrical contact. As shown, the knife edge portion extends along the top of one of the long walls of the recess 105, so that the hook seats essentially immovably on the knife edge, which thus bears the entire weight supported by the hook.

While we have described one specific embodiment in detail in accordance with applicable statutes, our invention should not be limited by such disclosure which is merely illustrative of the invention.

We claim:

l. Electroplating apparatus, comprising a rack to be immersed in an electroplating solution for carrying hollow cathodic articles to be plated during such immersion and cooperating consumable anodes, a plurality of anode supports on said rack, each anode support comprising a vertically upwardly projecting pin having a laterally projecting flange, a plurality of replaceable anodes, one on each said supp-ort, each said anode having an annular bottom surface adapted to rest on said flange in electrical contact therewith and a recess in its bottom surface dimensioned to receive said pin with an easily slidable tit, so that each anode projects freely upwardly from its associated ange and each anode remains on its support and in electrical contact therewith only by the cooperation of said pin and recess and by gravity and as long as the rack is horizontal and is replaceable by lifting it o' the support and lowering another in its place, a plurality of supports for hollow articles on said rack, each concentric with one of said anode supports and electrically insulated therefrom, each said hollow article support comprising a plurality of contact bars extending radially with respect to the associated anode support and having upper surfaces cooperating to support in a vertically extending position a hollow cathodic article resting on said upper surfaces by gravity and encircling the anode on the associated anode support, so that the article is laterally unrestrained and is held on its support and in electrical contact therewith solely by gravity and as long as the rack is horizontal, and is replaceable by lifting it off the article support and lowering another in its place, means to connect the contact bars electrically with the negative terminal of a source of direct electrical energy, means to connect the anode supports electrically with the posit-ive terminal of said source, and means to mount said rack on a carrier including means to insure that said rack is horizontal when so mounted.

2. Electroplating apparatus, comprising a rack to be immersed in an electroplating solution for carrying hollow cathodic articles to be plated during such immersion and cooperating consumable anodes, said rack comprising a horizontally extending framework including a grid of cross members extending along lines traversing said framework and intersecting at a plurality of locations, and a plurality of annular members, one encircling each of said locations and attached to the cross members extending along the lines -intersecting there, each said annular member providing an aperture at its intersection, said cross members and annular members being in electrical contact, a plurality of cathode contact bars, one on top of and in electrical contact with each said cross member adjacent each said intersection, the contact bars at each intersection cooperating to support' in a vertically extending position a hollow cathodic article placed on its end thereon, a plurality of anode supports, one extending Vertically through the aperture at each intersection, means electrically insulating each anode support from the grid, each anode support comprising a vertically upwardly projecting pin having a laterally projecting flange,l a plurality of replaceable anodes, one on each said support, each said anode having an annular bottom surface adapted to rest on said angc and a recess in said bottom surface adapted to receive said pin slidably, sothatsaid anode remains on said anode support and in electrical contact therewith solely by gravity and as long as said rack is horizontal, and may be replaced by lifting it ott the support and lowering another in its place, and means for supporting said rack and conveyingV electrical current thereto comprisinga pair of upwardly extending posts, one mechanically and electrically attached to one end of said framework, means mechanically connecting the other post to and electrically insulating it from the other end of the framework, means electrically connecting the other post to the lower ends ef the anode supports. a support member, means to mount said rack on said support member including means to insure that said rack is horizontal when so mounted, and means to connect said posts electrically to the opposite terminals of a source of direct electrical energy.

3. Electroplating apparatus as dened in claim 2, in which said rack mounting means includes a pair of brackets on said support member at different elevations, means electrically insulating at least one of said brackets from said support member, means to connect said brackets electrically to the opposite terminals of a source of electrical energy, and a pair of hooks on the upper ends ot said posts and adapted. to engage said brackets, one ot said posts being longer than the other by an amount equal to the difference in elevation of said hooks so that said rack is supported horizontally only when the longer of said posts is hooked to the higher bracket, and said rack is thereby connectable to said source with only one predetermined polarity.

4. Electroplating apparatus, comprising a rack to be immersed in an electroplating solution for carrying at least one hollow cathodic article to be plated during such immersion and a cooperating consumable anode, said rack comprising a horizontally extending grid of cross members extending along intersecting lines, but terminating short of the intersection thereof, and an annular member encircling the intersection of said lines and attached to all of the cross members extending along said intersecting lines, said annular member providing an aperture at the intersection, means to connect said cross members electrically to the negative terminal of a source or direct electrical energy, a plurality of cathode contact bars, one on top of and in electrical contact with each said cross member adjacent each said intersection, the contact bars at each intersection cooperating to support iny a vertically extending position a hollow cathodic article resting thereon by gravity, so that the article is held on said bars and in electrical contact therewith solely by gravity and is replaceable by lifting it oit the contact bars and lowering another in its place, an anode support extending vertically through the aperture at the intersection, means electrically insulating cach anode support from the grid and the annular member, said anode support comprising a vertically upwardly projecting pin having a laterally projecting flange, a replaceable anode on said support, said anode having an annular bottom surface adapted to rest on said flange and a recess in said bottom surface adapted to receive said pin slidably, so that said anode remains on said anode support and in electrical contact thereby solely by gravity, and may be replaced by lifting it off the support and lowering another in its place, and means to connect said anode support to the positive terminal of said source,

5. Electroplating apparatus as defined in claim 3, including an electrically insulating collar on said pin below said `ilange and projecting laterally beyond said ange, said collar being effective to prevent lateral movement of the article into electrical contact with the anode or its support.

6. Electroplatng apparatus, comprising a rack to be immersed in an electroplating' solution forcarrying hollow cathodic articles to be platedduring such immersion and cooperating anodes, anode supports mounted on and electrically insulated from said rack, article supports mounted on and electrically connected to said rack, means for supporting said rack comprising a pair of posts extending upwardly from said rack, means mechanically and electrically connecting one of the posts to the rack, means mechanically connectingthe other post to and electrically insulating it from the rack, means electrically connecting the other post to the anode supports, a support member, a pair of brackets on said support member at different elevations, means electrically insulating at least one of said brackets from said support member, means to connect brackets electrically to the opposite terminals of a source of direct electrical energy, and a pair of hooks on the upper ends of said posts and adapted to engage said brackets, one of said posts being longer than the other by an amount equal to the difference in elevation of said lorackets so that said rack is supported horizontally only when the longer of said posts is hooked to the higher bracket, and said rack is thereby connectable to said source with only one predetermined polarity.

7. Electroplating apparatus, comprising a rack to be immersed in an electroplating solution for carrying a hollow cathodic article to be plated during such immersion, said rack comprising a horizontally extending grid f intersecting cross members, means defining an aperture in said grid at said intersection, an anode support extending vertically through said aperture, means electrically insulating the anode support from the grid, a replaceable anode mounted on and projecting vertically upward from the anode support, means to connect said cross members electrically to the negative terminal of a source of direct electrical energy, a plurality of cathode contact bars, one on top of and in electrical contact with each said cross member adjacent each said intersection, the contact bars at each intersection cooperating to support in a vertically extending position a hollow cathodic article resting thereon by gravity, so that the article is held on said bars and in electrical contact therewith solely by gravity and is replaceable by lifting it oil the contact bars and lowering another in its place, the said contact bars having upper surfaces sloping generally downward toward the intersection and tending to center with respect to the anode a hollow article placed thereon.

8. Electroplating apparatus as dened in claim 7, in which each contact bar extends radially a substantial distance with respect to its associated intersection, so that the contact bars of each intersection may receive for electroplating articles having diameters anywhere within a range of substantial extent.

References Cited in the tile of this patent UNITED STATES PATENTS 349,535 Sohner Sept. 2l, 1886 628,686 Boissier luly 11, 1899 644,029 Cowper-Coles Feb. 20, 1900 742,131 Pratt Oct. 20, 1903 825,591 Engelhard July 10, 1906 1,438,722 Price Dec. 12, 1922 1,715,411 DiCesare June 4, 1929 1,872,290 Hitner Aug. 16, 1932 2,116,929 Harshaw May 10, 1938 2,323,952 Wick July 13, 1943 2,363,005 Kalista Nov. 21, 1944 2,620,296 Wilsdon Dec. 2, 1952 OTHER REFERENCES Belke Plating Rack Manual, lune 18, 1947, pages 45, 47, 51, Belke Mfg. Co. 947 N. Cicero Ave., Chicago, Illinois.

Claims (1)

1. ELECTROPLATING APPARATUS, COMPRISING A RACK TO BE IMMERSED IN AN ELECTROPLATING SOLUTION FOR CARRYING HOLLOW CATHODIC ARTICLES TO BE PLATED DURING SUCH IMMERSION AND COOPERATING CONSUMABLE ANODES, A PLURALITY OF ANODE SUPPORTS ON SAID RACK, EACH ANODE SUPPORT COMPRISING A VERTICALLY UPWARDLY PROJECTING PIN HAVING A LATERALLY PROJECTING FLANGE, A PLURALITY OF REPLACEABLE ANODES, ONE ON EACH SAID SUPPORT, EACH SAID ANODE HAVING AN ANNULAR BOTTOM SURFACE ADAPTED TO REST ON SAID FLANGE IN ELECTRICAL CONTACT THEREWITH AND A RECESS IN ITS BOTTOM SURFACE DIMENSIONED TO RECEIVE SAID PIN WITH AN EASILY SLIDABLE FIT, SO THAT EACH ANODE PROJECTS FREELY UPWARDLY FROM ITS ASSOCIATED FLANGE AND EACH ANODE REMAINS ON ITS SUPPORT AND IN ELECTRICAL CONTACT THEREWITH ONLY BY THE COOPERATION OF SAID PIN AND RECESS AND BY GRAVITY AND AS LONG AS THE RACK IS HORIZONTAL AND IS REPLACEABLE BY LIFTING IT OFF THE SUPPORT AND LOWERING ANOTHER IN ITS PLACE, A PLURALITY OF SUPPORTS FOR HOLLOW ARTICLES ON SAID RACK, EACH CONCENTRIC WITH ONE OF SAID ANODE SUPPORTS AND ELEC-

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