US2820757A - Plating racks and methods of racking articles for electroplating - Google Patents

Description

Jan. 21, 1958 w. E. BELKE 2,820,757

PLATING RACKS AND METHODS OF RACKING ARTICLES FOR ELECTROPLATING Filed May 26, 1955 5 Sheets-Sheet l INVENTOR.

Jan. 21, 1958 w. E. BELKE 2,320,757

PLATING RACKS AND METHODS OF RACKING ARTICLES FOR ELECTROPLATING Filed May 26, 1955 5 Sheets-Sheet 2 Jan. 21, 1958 w. E. BELKE 2,320,757

PLATING RACKS AND METHODS OF RACKING ARTICLES FOR ELECTROPLATING Filed May 26, 1955 5 SheetsSheet 3 434i: M lililil'lll'b 84 INVENTOR.

Jan. 21, 1958 w. E. BELKE 2,320,757

PLATING RACKS AND METHODS OF RACKING ARTICLES FOR ELECTROPLATING Filed May 26, 1955 5 Sheets-Sheet 4 o o -'//f o 0 y 0 96 o o V Jan. 21, 1958 w. E. BELKE 2,820,757

PLATING RACKS AND METHODS OF RACKING ARTICLES FOR ELECTROPLATING Filed May 26, 1955 5 Sheets-Sheet 5 IN V EN TOR.

United rates Patent @fice 2,820,757 Patented Jan. 21, 1958 PLATING RACKS AND METHODS OF RACKING ARTICLES FOR ELECTROPLATING William E. Beike, Chicago, 111., assignor to Bclke Manufacturing (10., Qhicago, 11]., a corporation of Illinois The present invention relates to plating racks and methods of racking articles for electroplating, and is'particularly concerned with the provision of improved structures and methods for meeting the electroplating requirements of an infinite number of diiferent articles, while preserving useful rack parts in classified arrangement for use in meeting future requirements.

One of the objects of the invention is the provision of an improved method of assembling rack parts of the type which can be disassembled and reused, in such manner that a low resistance electrical connection is assured between the rack parts by cutting into the metal of one part with the other and exposing a new bright surface for effecting the electrical connection each time the parts are assembled.

Another object of the invention is the provision of an improved method of assembly which includes the cutting of a new bright surface for engagement between rack parts, in which provision is automatically made for covering and sealing these clean connecting surfaces against the ingress of electrolyte for maintaining good electrical connection and preventing erosion of the conducting metal. t 1

Another object of the invention is the provision of improved rack structures including rack sections and rack tips which are adapted to beso assembled that a new bright conductingsurface is cut for engagement between them whenever they are assembled to provide the low electrical resistance connection between the parts everyv time the parts are reassembled. 7

Another object of the invention is the provision of improved rack and tip structures whichare protected against the action of acid throughout, except at the point where the rack hangs and the tip supports articles tobe electroplated and at the connection between the rack and tip, the latter connection being automatically sealedby assembly of the parts after cutting and assuring new bright engaging surfaces between the tip and rack.

Another object of 'the invention is the elimination of the methods and structures of the prior art in which racks have been provided for an infinite number of types of articles to be electroplated and the racks have been dis-. carded after useor stored: in such manner that they are not likely to befound, even if thesame articles areto be electroplated again, and the racks have represented a loss because of the lack of system in their assembly and storage.

Another object of the invention is the provision of improved electroplating .racks' and methods in which the racks can be assembled after coating, and disassembled without injury to the parts orinsulation, and having the following advantages:

(1) Damaged tips can be replaced quickly and economically, and the present racks can be kept'at full production.

(2) Tips are easily replaced with plating ditferent articles.

different tip designs for (3) Spacing of tips can be changed. X

(4) Spacing of rack members can be changed.

(5) When no longer needed, racks can be disassembled and the parts reused in racks of similar or different des1gn.

(6) Rack parts can be stored systematically in a small fraction of the space required for assembled racks.

(7) Systematic storage makes any part or tip instantly available and easy to use.

Another object of the invention is the provision of improved rack assemblies including vertical splines and cross headers in which the headers and end portions extending at right angles and provided with a plurality of bolt assemblies for the purpose of holding the rackassemblies rigidiy rectangular without the necessity for using other braces that would interfere with the tips attached to the rack splines which extend vertically between the end splines. I I

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the drawings accompanying the specification, of which there are four sheets,

Fig. l is a view in perspective of an electroplating-rack assembly with various exemplary plating tips;

Fig. 2 is a sectional view taken on the plane of the line 2-2 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a sectional view taken on the plane of the line 3-3 of Fig. 1, looking in the direction of the arrows;

Fig. 4 is an exploded view showing the parts of a rack and 'tip for the purpose of explaining their assembly;

Fig. 5 is a sectional view taken on the plane of the line 55 of Fig. 1, looking in the direction of the arrows;

Fig. 6 is a view in perspective of one of the tip parts; Fig. 7 is a View in perspective of another tip part; Fig. 8 is another view in perspective of a third tip part 7 of the type employed in Fig. 5;

A members of Fig. 9;

Fig. 12 is a side elevational view in partial section of the other threaded member of Fig. 5;

Fig. 13 is a view in perspective of a rack assembly employing twin hooks and twin spines;

Fig. 14 is a similar view of a multipie spine assembly;

Fig. 15 is a sectional View taken on the plane of the line 1515 of Fig. 13, looking in the direction of the arrows;

Fig. 16 is a view in perspective of a modified form of rack;

Fig. 17 is a similar view of another modification.

Referring to Fig. 1, this is a view in perspective which is exemplary of an infinite number of rack assemblies,

, which may be made up out of one or more spine memhers 20, and one or a multiplicity of tip members 21, 22, 23 or 24.

The tip members selected are merely exemplary of a few types, of which there are an infinite number of forms for meeting an equal number of electroplating requireand tips, which is immersed in the electrolyte or subjected to its fumes, excepting the upper V-shaped hook 26 of the rack 20, which hook is electrically connected to the conducting rod on which it is supported, and excepting the extreme end surfaces 27 of the tips on that side where the tips engage the electroplated articles.

Thus the tips 21 may have the insulation ground ofi at 27 on the bottom and top of the extreme ends of these tips, because they are intended to engage an article by spreading action, being inserted into an apertureorcavity in the article to'eflect an electrical conducting'connection between the rack and article.

In some embodiments of the invention the hook 26 may also be coated, except its lower surface 28, which actually engages the rod, serving as a bus bar.

The rack member 21), which is sometimes called a spine, comprises an elongated metal bar of substantial thickness and width of conducting metal, such as copper, provided with the hook at one end'and with the insulating coating 25, and a plurality of cylindrical 'apertures"ex-' tending through the coating and copper for attachment of the various types of tips. n

For example, the tip 21is a round wire spring contact tip employing a threaded copperbolt 29, with a pairlof wire members 30 and 31, which have a pair of converging portions 32, arranged on opposite sides of .the shank of the bolt 29, adjacent the head 33. j

' A sheet metal clip 34 has an aperture 35 for passing the shank of the bolt, and has a pair of inwardly extending flanges 36', each of which has a groove 37 for embracing the wires 30 and 31 at their converging portions 32.

A threaded bushing 38may be threaded on'the threaded shank 39, clamping the wires 30, 31 against the head ,33, and against the clip 34 and effectively securing themto the bolt. The wires are bent outwardly at 40 on each side of the bolt to bring their parallel body portions 41 into a spread condition, and are bent inwardly again'at 42 to provide shoulders that may engage the body to jb e' electro-plated just outside an aperture, limiting the move: ment of. the body toward the spine 20. V I The tip is provided with extreme end portions 43 which may be straight and parallel for insertion into the aperture of thesubject, and the adjacent wires 30, 31 are in, each case given an'initial tension away from each other, so that they may be forced together and inserted in the' aper ture in the subject, spreading resiliently to bring the bare surfaces 27 into engagement with the subject inside said aperture. Y

The bent formations 40, 41, 42 increase the resiliency of this wire tip. The wire tip so far described is ,completely covered with a thick layer of plastic insulation, leaving the bolt shank 39 bare, and leaving the surfaces 27 bare. l ,ii

Bushing 38 is surrounded with a sealing sleeve 44, which has an outwardly extending resilient circular'ffiang'e 45, tapering to a thin edge and adapted to engage the insulating'coating 25 on the spine 20, to effect a liquid and gastight seal, entirely enclosing this side of the spineagainst the acid. f

The threaded shank 39 also supports a tapered cut ting bushing 46, further to be described, which has a tapered surface 47, provided with a multiplicity of sharp V-shaped ridges 48, of the type better shown in Figs. 11 and 12, separated by V-shaped grooves 49.

These ridges hear such a size relation with respect to the aperture'50. in the rack or spine 20, that the ridges cut grooves in the walls of the aperture 50, forming a new, bright electrical conducting surface on both the bushings 46 and the aperture 50 every time the two parts are as: sembled and the bushing is drawn into the aperture.

The assembly also includes a threaded member or nut 51, having a complementary threaded bore 52 for engagement with the shank 39, and having an external noucircular surface 53 for engagement with a wrench.

The engaging end of the nut 51 has a tapered frustoconical surface 54 which engages in theaperture' 50, and is adapted to rotate therein while centering the shank39 in the aperture and drawing the cutting bushing 46 and the aperture 50 to secure the tip on the rack. r

The cutting bushing 46 does not rotate as its V-shaped cutting edges 45'engage in the metal in the aperture 50,,

preventing rotation; but the frusto-conical surface 54 on the nut 51 rotates and engages both the metal around vvaperture 50 and the insulating coating 25 around the of acid.

Securement of the tip,2 1 on the rack 20, by means of the nut 51, automatically secures it against rotation and draws the resilient tip flange 45 of insulating material or resilient composition against the insulation 25, automatically sealing this side of the assembly at the same time the cutting bushing 46 is producing new bright cut surfaces for engagement between the tips.

This occurs every time the parts are reassembled, as they are intended to be taken apart when their use has been finished, s'othat the'parts may be stored with other similar parts and used over again by reassembly with the same or a different rack for new sub ects.

Thus there is'always a clearance at 59 about the shank 39'between the cutting bushing 46 and the nut 51, throughout the-life of the tip, so that-there is room to take up any wear 'onthe tip or wear in the aperture of the spine, so that the parts may be drawn into tight engagement with each. other; I 1 3 i Referring to Fig. l, the tip 22 has its partsof exactly I similar' construction, except that the tip has a pair of forwardly extending wire pairs 60, held by the same clip 34, bent forwardly-from" the middle portions 32,, and clamped beneath the nut33a. This is'exemplary'of a tip having a multiplicity of wires for supporting a multi-v plicity-of subjects.

Referring to tip 23-of Fig. 1, this is exemplary of one type of rugged flat spring tip, the structure of which is shown in-Fig.- 5. '-In this case the tip includes a pair of relatively fiat copper springs 61, 62, the central bodies of which are provided with registering apertures 63. -The;bodies of springs '61, 62 are riveted together at 64,--64,- and-formed with the outwardly turned obtuse angles at 65, so -that "their end portions 66 diverge. These end portions may be completely covered with the plastic'insul'atiomrwhich may be ground 05 wherever the tips araimenaed t'o'have conducting engagement with a subject to be electroplated. I I

The samec'u'tting bushing 46 may be employed, but itis provided with a non-circular head 67 for engagement with two of the flanges 68 of a metal clip 69, which has an aperture 70 for the screw bolt71.

The clip 69 has oppositelyextending flanges 72, 72 engaging the edges of the flat springs 61 and 62, and preventing the hat springs from rotating relative to the cuttingbushing, which is to be fixed on the spine 20, as previously described.. a H

The screw .bolt'71' extendsinto the threaded bore 73, but it leaves suflicient room in the threaded bore 73 for the shank 74 of another screw bolt without a head but having a kerf 75 in its end. The tapered nut 51 is threaded on the shank 74, drawing the parts into tight electrical conducting relation with the spine 20, as previously described, and the nut 51 is covered by a similar insulatingcapm56,sealing this end of the assembly.

The flat sprin'g'tip 23 is again covered over all with insulationn76, terminating in the tapered ,circularlseal ing jflang'e77j, whichjengages and seals against the insulating coveringes. Referring-to the rugged flat spring tip 24 of Fig; 1, the structure of this member is shownin Figs, '9 to 1 2, and this spring tip being adapted to smartheavier subjects, it is provided with a twin mountingi clamps the cutting bushing to thecruciform i For this purpose a p'air' of flat springnieniber'sfis and "7 9 have their central fiat body portions secured with a 'pairof rivets 80 to acrucifo'rm supporting member 81, having rivet apertures'82. The cruciforrn'member 81 has its upwardly and downwardly'e'xtending portions 83 "provided with 'apertur'es8 4, large enough to receive the each case at a spacing suitable :for causing 91 in the bushing to register with 'the apertures '90, spine20. H I V The spring tip 24, is again bent outwardly at an obtuse angle at 92, '92, providing the spreading ends 93. All

parts of the ,tip assembly on the right side of Fig. 9, except they cutting edges 48 of the cutting bushings 86 are covered with the insulating compound 94, .which terminates about thecutting bushings 'in the circular, tapered thin sealing flanges 95 for engaging the insulation 25. J

On the left side of Fig. 9, the construction about its shank may be identical with that shown in the previous figures. v A

Referring to Fig. 13, this is exemplary of a rack with twin spines and twin hooks, and the rack includes a pair of the members 20, previously described, and provided with a multiplicity of apertures 96. These spine members are numbered 97 and 98, and they are joined together at the bottom by a cross bar 99, and at the top by a header bar 100.

The header bar 100 has downwardly .turned end portions providing support for a pair of pole assemblies passing through the spines and holding the rack rigidly rectangular. I

The cross bar 99 may have a single point of securement 101 at each of its ends of the construction shown in Fig. 15, while theheader bar 100 may have a pair of these connections 102 at each of its ends, as shown in Fig. 15. The twin spine rack of Fig. 13 also represents an assembly which may be assembledvto meet the requirements of a particular electroplating subject, and it may be taken apart and its parts stored with other similar parts for reuse.

For this purpose the cross bar 99 is provided with a cutting bushing 103, similar to that illustrated in Fig. 9, but having its reduced threaded end portion 104 threaded into a threaded bore 105 in the cross bar 99.

The threaded bushing 103 has the same tapered surface 46 with sharp V-shaped cutting edges 48 for engag ing in an aperture 106 in the spines 97 or 98, and. the

cross bar 99 with its cutting bushing 103 is covered over all with the same layer of plastic insulation 25, surrounding a pair of cutting bushings 103 on the cross head 100, and terminating in the thin tapered resilient circular flange 107, which efiects a sealing engagement with the insulation 25 on spine 98.

The other side of the assembly with the cutting bushing 103 is substantially the same except that the threaded shank 108 is driven home to the end 109 of the threaded bore 110 in cutting bushing 103 by using a screw driver in the kerf 111.

The shank 103 and cutting bushing 103 represent a rigid unit in each case to be drawn into the aperture 106 by means of the same tapered nut 51, which is covered by a cap 56 of insulating material.

Any desired type of tip assembly may be secured in any of the apertures 96 in the twin spines 97 and 98 for any particular subject. When the work is completed the parts may be disassembled and stored in bins for each part with similar parts to be selected at will and reassembled for new subjects.

Fig. 14 is exemplary of a multiple spine installation, having a longer cross head 112 and a longer cross bar 113, provided with multiple apertures for receiving the securing members of Fig. 15. This assembly includes plicity of apertures 1 18; and for the purpose of SuPp Iting the articles to be electroplated in a different position,

the central bodiesof the spines 114-117 have'been given a degree twist at 119, near the top, and near the bottom.

r This causes all of the fingers of the tips which are attached to extend transversely to the header 112 and the cross bar 113, permitting the rack assembly to support articles which are longer in the transverse direction, but which are located close together on the rack.

The structure of the tips and of the racks which support the tips may vary infinitely to meet the requirements ofan equal number of articles to be electroplated; but the method of using these structures includes the following steps: I 1

The rack member is provided with a body covering over all with a layer of plastic insulation, but having one or more through apertures. The tip is in every case secured to a tapered cutting bushing which is insertable into oneof said apertures and which has sharp V-shaped cutting edges that cut into the metal of the aperture and expose new V -shaped surfaces for engagement with the bushing supporting the tip.

The metal of the aperture may be said to flow as the tapered bushing progresses into it with its sharp edges, and the tapered bushing becomes fixed against rotation, while producing this new bright, bare copper conducting surface engaging the bushing.

The rack of Fig. 14 has its cross head 112 provided with downwardly turned ends for supporting a pair of bolt assemblies passing through the splines; and this structure also holds the rack rigidly rectangular without other bracing.

The bushing includes a threaded bore for receiving a threaded shank on which there is mounted a threaded nut having a tapered portion engaging in the aperture, centering the threaded shank and drawing the cutting bushing into cutting engagement with the aperture.

A tapered nut leaves a threaded portion of the shank protruding for engagement with an insulating cap, threaded thereon and covering the nut while engaging the insulating covering on the rack to seal that side of the assembly against ingress of acid.

The tip structure on the other side is covered with the same thick plastic insulation, excepting the sharp tapered V-shaped cutting edges which are surrounded with an outwardly extending circular, thin flexible resilient flange that resiliently engages the insulation on that side and seals the assembly on that side against ingress of acid.

Thus a connection of high electrical conductivity and rigidity is provided although the parts may be disassembled, stored and reused over and over again. An ample clearance is provided between the end of the tapered nut and the end of the cutting bushing, so that there is always room for them to be drawn into tight engagement in the same or other aperture in a supporting rack.

It will thus be observed that I have invented an improved electroplating rack structure and improved methods of assembly, whereby an acid-tight seal is automatically provided, surrounding and enclosing newly cut and bri ht engaging surfaces between the parts of the tip and the parts of the supporting spine.

My method has the advantage that damaged tips can be replaced quickly and economically, and the racks can be kept at full production.

Fig. 16 is a view in perspective of another form of rack having a spine 125, as previously described, with a hook 130. Spine has a plurality of T bars 127, 12,8, 129; and each T bar may comprise a flat bar of metal having a bracket plate 126 integrally welded thereto and provided with upper and lower apertures for bolts 1.3 1, 132, which pass through the spine 125 and secure the bars 127 rigidly in place.

The T bars 127 and brackets 126 are covered over ent articles.

among? a Referring to- FigI 17; this is another form of 'l' bar .rack in which the Tbars:135,,135, an dl13f7 areattached to centralbrackets 138 by]weld in g, and;covered=with insulation overall. The T bars are again providedwith the bolt assemblies 13 1, 132 passingtthrgugh the spine :and resembling 'in structure the details of Fig. 115,

The bars. 135 137 have -a rightangulartwist adjacent the bracket 138 in each: case; and this causes the tips 133 to extend horizontally, 'thesetips being similar in all respects to the assembly shown in Fig. The right angular twist places the tips inhorizontalpositiongand the provision of twoboltson the bracketsecurestheT bars rigidly; at right angles to the spine.

The spacing of the tips can be changed a n drthe 'spacing of the rack members can; be changed, andthe tips are easily replaced with dififerenttiptdesigns forplating difi'er- When no longer neededthe: raeksfpa i be disassembled and the parts 'Ieusedin tracksi of similar or different design. The parts may be storedsystematically in bins with similar parts in a small fraction ofi the space, required for assembled racks, thus making any'rack or tip put instantly available andIready-to be used. 7

' All the fore'going advantagesare also realized while automatically cutting a new brightlconducting surface between the tip and rack-when ltheLparts are assembled, and also effecting automatically. a 'liquid-tight seal about the conducting parts of the rack-fand tip connection.-

While I have illustratedapreferredembodiment'of my invention, many modifications may be: made without departing from the spirit ,of the invention, and l do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is: 7

1. An electroplating rack, comprising a pair of vertically extending metal spines of flat bar shape, each formed with a downwardly opened V-shaped hook at its upper end, and the under surface ofsaid hooks being bare on the inside to engage a bus baron the inside, each spine having a multiplicity of through bores for attachment of rack tips, and each spine having a pair of apertures at its upper end below its hook and another aperture at its lower end, a cross bar carried by the lower ends of the spines and having registering apertures, a U-shaped upper cross barcarried by the upper ends of said spines and having apertures registering with the upper pair of apertures in each spine, all the said cross bar apertures being threaded, a threaded bushing in each threaded cross bar aperture, said bushing having antannular shoulder engaging the cross bar in each case and having an enlarged cylindrical body with a tapered grooved end portion having converging sharp edges bordering its grooves, a threaded shank in said bushing, the bushing having a threaded bore for said shank, said shank passing through an aperture in a spine and having a tapered threaded member on the shank engaging the 8 other side of; the spine; a thick insulation covering over -t azs ws aossab svs csp iathe aas rmrqsraps sa d-pres baninsifl t s nh uas. an ns a collar rounding each bushing; and having a thin radial flange s o ar1sea in ?a ai tt ai rsai e' nsulat s a d an insulating pap ,nutf-having a boretor grotatably enclosingrsaidfthreaded member,-;and having a similar bore threadedflito receive said shankv end,-.to]hold the .cap in sealing engagement with the spineinsulation; the threaded member drawinglthetsharptedgespf the bushing into,cutting contact with theemetalgin the spine apertures and also effecting a tight seal between the thin radial, flange and the spine insulation. ,1

2 ,An, electroplating rack,;.comprisinga ,pair of -verticallyextending'metal, spinesof flat bar shape, each formed with a downwardly-openedV-shaped. hook .atiits upper end, and: the under surface of said hooks being bare on the inside to engage;atbus bar on the inside,,each

spinel having a multiplicity of through V bores for. attachment of rack tips, and eachspine havinga pair of apertures atits upper end below its;hook and anotheraperture at itslower end, a crossbar carried by the lower ends of the spines and having registering apertures, a U-shaped upper cross .bar, carried bythe upper endsof said spines "and having apertures registering withthe upper pair of apertures in each'fspine, all the said cross bar apertures being threaded, a threaded bushing in each threaded cross 'bar' aperture, said bushing having an annular shoulder engagingthe cross bar in each caseand having an enlarged cylindrical body with atapered grooved end portion having converging sharp edges bordering its grooves', a threaded shank in said bushing, the bushing having a threadedbore or said,shank,said shank passing through an aperture "in a spine and having a taperedthreaded member onthe, shank engaging the other side of the spine, a thick insplation covering over the spines andcross bars except in'theapertuies, and said cross barinsulation-having an insulating collar surrounding each bushing and having a. thin radial flange on each collar sealing against said spine insulation, and an insulatingcap nut having a bore for rotatably enclosing said threaded member, and having a similar bore threaded to receive said shank end, to hold the cap in sealing eugagementwith the spine insulation, the threaded member drawing the sharp edges of the bushing into cutting contact with the metal in the spine apertures and also efiecting a tight seal between the thin radial flange and the spine insulation, said cross bars also supporting a

Claims (1)

1. AN ELECTROPLATING RACK, COMPRISING A PAIR OF VERTICALLY EXTENDING METAL SPINES OF FLAT BAR SHAPE, EACH FORMED WITH A DOWNWARDLY OPENED V-SHPED HOOK AT ITS UPPER END, AND THE UNDER SURFACE OF SAID HOOKS BEING BARE ON THE INSIDE TO ENGAGE A BUS BAR ON THE INSIDE, EACH SPINE HAVING A MULTIPLICITY OF THROUGH BORES FOR ATTACHMENT OF RACK TIPS, AND EACH SPINE HAVING A PAIR OF APERTURES AT ITS UPPER END BELOW ITS HOOK AND ANOTHER APERATURE AT ITS LOWER END, A CROSS BAR CARRIED BY THE LOWER ENDS OF THE SPINES AND HAVING REGISTERING APERTURES, A U-SHAPED UPPER CROSS BAR CARRIED BY THE UPPER ENDS OF SAID SPINES AND HAVING APERTURES REGISTERING WITH THE UPPER PAIR OF APERTURES IN EACH SPINE, ALL THE SAID CROSS BAR APERTURES BEING THREADED, A THREADED BUSHING IN EACH THREADED CROSS BAR APERTURE, SAID BUSHING HAVING AN ANNULAR SHOULDER ENGAGING THE CROSS BAR IN EACH CASE AND HAVING AN ENLARGED CYLINDRICAL BODY WITH A TAPERED GROOVED QEND PORTION HAVING CONVERGING SHARP EDGES BORDERING ITS GROOVES, A THREADED SHANK IN SAID BUSHING, THE BUSING HAVING A THREADED BORE FOR SAID SHANK, SAID SHANK PASSING THROUGH AN APERTURE IN A SPINE AND HAVING A TAPERED THREADED MEMBER ON THE SHANK ENGAGING THE OTHER SIDE OF THE SPINE, A THICK INSULATION COVERING OVER THE SPINES AND CROSS BARS EXCEPT IN THE APERTURES, AND SAID CROSS BAR INSULATION HAVING AN INSULATING COLLAR SURROUNDING EACH BUSHING AND HAVING A THIN RADIAL FLANGE ON EACH COLLAR SEALING AGAINST SAID SPINE INSULATION, AND AN INSLUATING CAP NUT HAVING A BOR EFOR ROTATABLY ENCLOSING SAID THREADED MEMBER, AND HAVING A SIMILAR BORE THREADED TO RECEIVE SAID SHANK END, TO HOLD THE CAP IN SEALING ENGAGEMENT WITH THE SPINE INSULATION, THE THREADED MEMBER DRAWING THE SHARP EDGES OF THE BUSHING INTO CUT TING CONTACT WITH THE METAL IN THE SPINE APERTURES AND ALSO EFFECTING A TIGHT SEAL BETWEEN THE THIN RADIAL FLANGE AND THE SPINE INSULATION.

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