US2422242A - Electroplating fixture - Google Patents

Description

June 17,1947. M, KAUF AN 2,422,242

ELECTROPLAT ING FIXTURE Filed July 16, 1945 5 Sheets-Sheet 1 2 INVENTOR ""1 l E Monro/v KAUFMAN ATTORN EY June 17, 1947. KAUFMAN 2,422,242

ELECTROPLAT ING FIXTURE Filed Jul 16, 1945 5 Sheets-Sheet 2 INVENTOR MORTON KAUFMAN BY W I ATTOR EY June 17, 1947. I KAUFMAN 2,422,242

ELECTROPLATING FIXTURE Filed July 16, 1943 3 Sheets-Sheet 5' INVENTOR Monro/v kAuFMA/v BY V ATTORNEY Patented June 17, 1947 ELECTROPLATING FIXTURE Morton Kaufman, Brooklyn, N. Y., assignor to Wright Aeronautical Corporation, a corporation of New York Application July 16, 1943, Serial No. 495,604

8' Claims.

This invention relates to apparatus for electroplating and is particularly directed to an electroplating fixture adapted to facilitate the electroplating of a limited portion of an article.

In aircraft engines it is common practice to chromium plate the crankshaft bearing surfaces. In order to prepare the crankshaft for the electroplating operation it has been the general practice to cover that portion of the surface of the crankshaft, which is not to be plated, with alternate coats of paint and tinfoil. Because of the irregular nature of the crankshaft surface this procedure takes considerable time. It is an object of this invention to provide an electroplating fixture which makes it unnecessary to so cover that portion of the surface of the crankshaft Or other object which is not to be plated. It is a further object of this invention to provide an electroplating fixture which may be readily attached to the object to be plated and which fixture, when in position on the object, effectively shields all of the surface of the object from the anode except that portion of the surface to be plated. That is, the invention comprises an electroplating fixture in which the anode is shielded and so disposed that only the surface to be plated is exposed to current flow from the anode.

Other objects of this invention will become apparent from reading the annexed detailed description in connection with the drawing in which:

Figs. 1 and 2 are perspective views of the front and rear sections, respectively, of a conventional aircraft engine crankshaft;

Fig. 3 is a vertical sectional view illustrating an electroplating fixture in position for plating the rear external bearing of the crankshaft;

Fig. 4 is a vertical view partly in section of a modified fixture for plating the front crankshaft section bearing;

Fig. 5 is a perspective view of the anode used in the fixture of Fig. 3;

Fig. 6 is a section on line l56 of Fig. 5; and

Fig. 7 is a vertical sectional view through an electroplating fixture in position for plating the internal bearing of the rear crankshaft section.

Referring to Figs. 1 and 2, these figures illustrate a conventional two-part single throw crankshaft of an aircraft engine. The rear crankshaft portion In is provided with a clamp bolt construction [2 which is adapted to clamp surface 20, both of which are to be plated with chromium. The remainder of the surface of the rear crankshaft section If] is to remain unplated and, in accordance with the present practice, this portion of the crankshaft surface is covered with alternate layers of paint and tinfoil. Similarly, the front crankshaft section has the front bearing surface or band-like area 22 which is to be plated while the remainder of the surface of this front crankshaft section is to remain unplated. As is readily apparent from the irregular nature of the crankshaft, as illustrated in Figs. 1 and 2,

' the operation of covering that portion of the about the crankpin M integral with the front crankshaft surface which is not to be plated, with layers of paint and tinfoil is quite tedius and time consuming. In fact, in practice it has been found that the preparation of the front crankshaft section for electroplating consumes approximately 195 minutes while with the use of the fixture hereinafter described this time is cut to approximately 5 minutes. Similar proportionate savings in time have been obtained from use of the electroplating fixture herein disclosed with'the rear crankshaft section. In addition, the saving of tin resulting from the use of this fixture is also an important factor particularly because of the present day importance of tin.

Now referring to Fig. 3, an electroplating tank 24 is provided with positive and negative electric terminal rods 26 and 28 and this tank is provided with an electrolytic solution of chromic acid. The objectto be plated is suspended from a beam 3!] of wood or other suitable insulating material and this beam is supported across the terminal rods 26 and 28. In order to plate the outer bearing surface 18 of the rear crankshaft section If! a fixture 3| is supported from the beam Si] by a bracket 32. The fixture 3] comprises a cathode steel sleeve 34 supported from the bracket 32 and threadedly secured to the external threads on th rear crankshaft section ID. The exposed surface of the cathode sleeve preferably is covered with any suitable insulating material 35; for example, a plastic insulating tape known as Rap-Bax is quite satisfactory. The bracket 32 is secured to the beam 3!] over a copper strip 33 which is secured to the under side of the beam and runs to one end of this beam. Thus, when'the beam 30 is disposed across the terminal rods 26 and 28 the negative terminal 28 is connected to the crankshaft section lc through the copper strip .33, bracket 32, and cathode sleeve 34. Cemented to the steel sleeve 34 is an insulating collar 38 which may be made of any suitable insulating or plastic material such as unichrome which is not affected by the particular electrolyte used.

Slidably mounted on the insulatin collar 38 is a steel sleeve 40 to which upwardly extending fingers 42 of the anode 44 are secured by soldering or in any other suitable manner. These fingers 42 are covered with a suitable insulating material 43, for example; withthe aforementioned Rap- Rax tape, and a plurality of flexible wire leads 45 are soldered or otherwise secured to these fingers and to the steel sleeve 40. The other end of the flexible wires 45 are connected-together, to the underside of the beam 30 and in contact with a second copper strip 4! which extendsto-thatend of the beam disposed over the electric terminar rod 26. The anode 44 is a cylindrical member preferably made of lead which is adapted tq-be concentrically disposed about the bearing surface In practice I8 and in spaced relation thereto. it has been found necessary to provide an inturned flange 43" at the bottom of the anode in orderto obtain an evenplate. Also, the anode 44 is tightly fitted within the cylind-rical: shield 46 havinga tapered inturned flange 48. This shield 46' ismade of suitable insulating material andmay also be made of the above-mentioned plastic through the electrolyte is substantially confined:

to the solution directly between the anode and cathode the body to be plated formingthe oathode. That -is; the linesof electric currentflow through the electrolyte are substantially straight lines between the anode andthe surface to be- Therefore; with; the shield 46 fitted' plated; I around.- the outer; and bottom surfaces: of the anode the current flow through the electrolyte from theanode isli'mited tothe radial space between thean'odeazidicathode; Accordingly, the presence of the shield 46 prevents radially outward and downward current flow throughthe electrolyte thereby making it unnecessary to cover any'portion ofthe surface of the crankshaft section l'fl xcept that immediately to the rear or.

above the surface I8 to be plated; The cathode sleeve 34'. is threaded down on the-crankshaft threads 3B to the bearing surface f8} thereby coV: eriri'g and shieldihgthe surface of the crankshaft immediately above the surface ill to be plated as viewed inFi'g. 3. The anode 4'4 and its shield 46 are secured together and'to the slidably mounted sleeve- 4'0; therefore, the flange 48' of the shield 46 maybe tightly paced against the crankshaft adjacent to the lower edge of the surface l8.

Bearing surface 22- of the front crankshaft sectibfi l may be plated with the aid of a fixture similar to that just describd ahd this fixture maybe secured toti-i threads 50611 thisci'arlkshaft section. However, inaddition, a sleeve must be placed over the crankshaft t'o cover that portion' of the crankshaftimmediately in front ofthe bearing surface 22. Nosuch sleeve is; necessaryinplating the bearing surface l8 of therear crankshaft section because of the location of the threads 35 immediately adjacent thebearing' sur face I 8 whereby the cathode sleeve 34 itself effectively shields that portion of the rear crankshaft section immediately above the bearing surface I 8.

In Fig. 4 a modified fixture 52 is illustrated for chromium plating the bearing surface 22 of the front crankshaft section I6. In this fixture the lead anode 54 and insulating sleeve 56 are similar to that illustrated in Fig. 3 and the anode is supported by fingers 58 secured to the insulating sleeve 60. This insulating sleeve, instead of being mounted on a cathode sleeve as in Fig. 3 is sup- 7 ported directly on the crankshaft over the splines 62. In assembly, the fixture is slipped down over the shaft'untilthe inturned flange 51 of the sleeve bearing surface 22. The fingers 58 like the fingers 42' are covered with suitable insulatin material. The sleeves 5i} and 69 thereby are operative to completely shield'all of the surface of the crankshaft except the bearing surface'22. as in previous modification. Instead of. an insulating sleeve 60; it is obvious that a metallic sleeve may'be-sub'- stitutedtherefor with the fingers 58 suitably insulated and supported therefrom. V

The crankshaft section and its fixture are supported by a beam 66 mounted upon electric terminal rods 68 and Ill, as in Fig. 3. A copper strip i2 is secured under one end ofthis beam for contact with the positive terminal rod 68 and spin rality of electric leads (4 are secured at one end to'the beam 66 in contact with this copper strip and are soldered at their other'endsto the anode fingers 5s. The beam fifiisprovided aibore i6:for the reception of the front end of the crank shaft. The crankshaft and it fixture are sup ported from the beam by a rod 18 secured to asupporting plate 'mounte'd upo-ntheupper'side of .thebeam. This rod is provided with a pair of centering collars 82 having adiameter cor-responding to the internal diameter of the crank shaft. These centering: collars are'each secured: to the supporting rod by a pai 0f segmental shaped washers 84. The. lower collar 82 isprovide'd with a radial hole 85-andis mounted upon:

the rod 18'so as. to-lineup-with a drilling 88'foun'dz.

in the crankshaft. With this construction theme 18 and its centering collars.82.may" be inserted within the crankshaft and a pin 95.! placed throughthe alined holes 86 and 88 to support the crank shaft from thebeam 65. A-copper strip'92 is's'e cured'tothe beam and extendsfromengagementf at one end with the negativet'erminal" rod 101 to engagement with the crankshaft andsupport-i'ng somewhat: different construction isrequired as illustrated; in Fig. 7;. This fixture. 9 consists of a cathode sleeve 96: threadedlysecured to: the

A cross strap 98 v is crankshaft, threads 36; secured across the top of the: sleeve 96 and. a

bracket- 98 is securedtothe sleeve'andito a beam.

Hill for supporting; the fixture and attached;

crankshaft section. Thesupport'ing beam; I118? is made of wood or other suitable'material: andi is mountedacr'oss the, tank r02. upon the posi" vs and negative terminal: rods 1 04 and I 05! A sop perstrip I98 securedto the under side ofthe i beam- I00 connects the negative terminal rod I06 with the crankshaft section I0 through the bracketw98 and the'cathode sleeve 96. The anode I I0 is preferablymade of lead and is supported by a steel rod IIZ secured to the beam I00 and to the cross strap 98 to help supportthe fixture and. to-concentrically dispose the anode within the internal bearing v20. A copper strip H4 is disposed along the under side of the beam I 00 and electrically connects the positive terminal I04 with the anode III] through the steel rod H2. Suitable insulatin washer are disposed between the rod H2 and the cross strip 98 to insulate these members from each other.

Before the fixture 94 is secured to the rear crankshaft section In a suitable stop-01f collar H6 is disposed about the upper portion of the bore through the crankshaft section I0. This stop-01f collar H6 is made of suitable insulating material and is provided with a steel backing I I8. Also, this stop-off collar is supported on the shoulder I20 formed at the upper end of the bearing surface 20 and because of the generally conical shape of this shoulder, the stop-off collar is self centering. The manner in which the stop-off collar H8 is supported obviously depends on the structure of the crankshaft adjacent the surface to be plated.

When the fixture. 94 is secured to the beam I00 the anode I I0 is concentrically disposed within the bearing 2!]. from the anode through the electrolyte will be radially outward to the bearing surface 20. The lines of flow of the current from the anode will extend slightly around the corner I22 but this is not serious since this portion of the crankshaft is subsequently polished.

From the above description it is apparent that the fixtures 3| and 52 both provide a convenient apparatus for electroplating a portion of an external surface of a body and which apparatus eliminates the necessity of providing a protective coating over the remainder of the surface of the body. The fixtures 31 and 52 both are particularly suited for plating external bearing surfaces or other similarly shaped surfaces of a body. The fixture 94 is particularly suited for plating an internal bearing surface or other similarly shaped surfaces, and this fixture also eliminates the necessity of providing the protective coating over the remainder of the surface of the body.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. An electroplating fixture for plating a circumscribing band-like area on the surface of an object disposed in a suitable electrolyte, said fixture comprising tubular shield means adapted to embrace said object adjacent to one edge of said band-like area, a tubular anode member supported from said shield means and arranged to be disposed in said electrolyte so as to surround said band-like area in spaced relation thereto, shield means embracing the surface of said anode member remote from said band-like area, said shield means having a portion extending inwardly from one edge of said anode member and terminating adjacent to the other edge of said band-like area.

Accordingly, the current flow 2. An electroplating fixture for plating a circumscribing band-like area on the'surface of an object disposed in a suitable electrolyte, said fixture comprising tubular shield means adapted to embrace said object adjacent to one edge of said band-like area, a tubular anode member having a plurality of finger-like extensions for supporting said member from said shield means and arranged to be disposed in said electrolyte so as to surround said band-like area in spaced relation thereto, shield means embracing the surfaceof said anode member remote from said band-like area, said shield means having a portion extending inwardly from one edge of said anode member and terminating adjacent to the other edge of said band-like area.

3. An electroplating fixture for plating a cir cumsoribing band-like area on the surface of an object disposed in a suitable electrolyte, said fixture comprising a first tubular shield means adapted to snugly embrace said object, a tubular anode member supported from said shield means and adapted to be disposed in said electrolyte about and in spaced relation to said band-like area, and a second tubular shield means embracing the surface of said anode member remote from said band-like area and having an inwardly extending portion, said fixture when in position on said object having an edge of said first shield means disposed adjacent to one edge of said I band-like area and having the inwardly extending portion of said second shield means termihating adjacent to the other edge of said bandlike area.

4. Apparatus for electroplating a circumscribin band-like area about an object disposed in a suitable electrolyte, said apparatus comprising a tubular anode member to be disposed in said electrolyte about said band-like area in spaced relation thereto, and shield means disposed about the surface of said anode member remote from said band-like area, said shield means having a portion extending inwardly from one edge of said anode member and terminating adjacent an 7 edge of said band-like area.

5. Apparatus for electroplating a circumscribing band-like area about an object disposed in a suitable electrolyte, said apparatus comprising a tubular anode member to be disposed in said electrolyte about. said band-like area in spaced relation thereto, said anode member having a portion extending inwardly from its lower edge toward, but terminating short of, the lower edge of said band-like area as said object is positioned in said electrolyte, tubular shield means embracing said object above said band-like area, said shield means terminating adjacent the upper edge of said band-like area, and second shield means embracing the surface of said anode member remote from said band-like area, said second shield means having a portion extending inwardly from the lower edge of said anode member below the inwardly extending portion of said anode member and terminating adjacent the lower edge of said band-like area.

6. Apparatus for electroplating a circumscribing band-like area about an object disposed in a suitable electrolyte, said apparatus comprising a tubular anode member to be disposed in said electrolyte about said band-like area in spaced relation thereto, tubular shield means embracing said object above said band-like area as said object is positioned in said electrolyte, said shield means terminating adjacent the upper edge of said band-like area, second shield means em-

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