US2330562A - Electropolishing apparatus - Google Patents

Description

S P 2 1943- F. E. DRUMMOND ET AL 2,330,562

ELECTROPOLISHING' APPARATUS Filed Dec. 20, 1940 mMEw F Lson E. DRl/MMOND. B'DAVID E.BENCH,

Patented Sept. 28, 1943 ELECTROPOLISHING APPARATUS Folsom E. Drummond and David E. Bench, Dayton, Ohio, assignors to The Himmel Brothers Company, Hamden, Conn, a corporation of Connecticut Application December 20, 1940, Serial No. 370,972

3 Claims.

This invention relates to improvements in the method and apparatus for manufacturing structural members, and more particularly mouldings conventionally used for ornamental purposes, such as for trimmings on automobiles, refrigerators, stoves, etc. and on buildings as mouldings and store fronts to support and hold plate glass windows and the like.

These mouldings consist of a two-ply metal member wherein the outer ply or covering surface is made of stainless steel, the inner or backing member being formed of ordinary iron or steel.

It is an object of this invention to provide an improved method of fabricating and finishing structural members of the character described.

Another object of this invention is to provide an improved method for polishing stainless steel strip prior to uniting it with the core or backing member to produce a finished structural moulding wherein the outer shell of stainless steel is highly polished.

Another object is to provide a combined electrolytic polishing and forming apparatus for manufacturing two ply structural members whereby the outer ply comprises a highly polished thin metal strip which has been electropolished and then formed over the backing member by simultaneously shaping the polished strip in contact with the backing or core member with roller dies to shape the inner core and outer polished shell member to form a unitary structural article.

Another object is to provide an improved electropolishing unit for treating metal strip material wherein one side of the strip is directly contacted at numerous spaced points over the surface by electrical conductors whereby theelectric currentis uniformly distributed over the entire area of the'strip as it is moved along through the electrolyte.

These and other objects and advantages will be apparent from the following description taken in connection with the drawing, wherein Figure 1 illustrates one embodiment of this invention showing an apparatus in section for electropolishing and fabricating a structural moulding member;

Figure 2 is an enlarged fragmentary portion in section of the electropolishing anode and cathode arrangement between which the strip is drawn-during electropolishing of the strip;

Figure 3 is 'a fragmentary sectional view taken substantially on the line 3-3 of Figure 1;

Figure 4 is a sectional view through the fin ished moulding taken on the line 4-4 of Figure 1 and looking in the direction of the arrows.

In the forming and polishing of stainless steel strip it has been found diiiicult to mechanically polish the stainless steel because of its very low heat conductivity. By reason of this property,-

when stainless steel is polished the heat developed is not readily dissipated and unless the polishing is done very carefully the material will be overheated at places causing discoloration, buckling, or deforming of the strip. This difiiculty has been overcome somewhat by providing the stainless steel strip with a backing member of relatively high heat conductivity so that the heat developed during the polishing operation is conducted away fast enough to prevent scorching or overheating of the strip. The backing strip also forms a, support for the very thin stainless steel covering and provides a strong structural member.

By the improved method of making moulding strips and the like according to this invention, no difliculty is involved due to overheating of the stainless steel strip during polishing since the strip is electropolished and fabricated to form a structural member.

Further, it has been the practice to form structuralv two-ply moulding articles by taking two strips of metal and simultaneously rolling or pressing them to the desired shape in contact with each other and polishing the preformed structural member by the use of burnishing or polishing wheels. By the improved method of this invention, this preforming of the structural member and then polishing the article is avoided with its problems of handling the finished article. To this end, the material is handled and treated while it is in a strip or band form and can be readily drawn'from a reel and passed over guide rolls into and out of a tank and the forming or shaping of the article into the final product is done after the polishing of the surface strip has been performed.

Referring to the drawing in detail, in Figure l a thin strip of stainless steel, designated I 0, is withdrawn from a reel l I and passed into the electropolishing unit, generally designated l2. This unit preferably comprises an electropolish- .ing compartment l4, and rinsing chamber IS. The compartment I4 is suitably lined with a material such as rubber, glass, or lead which is resistant to attack by the electrolyte IS. The stainless steel strip Ill is retained under tension by the brake means t8 and is guided through the electropolishing and rinsing compartments by the rolls 20. In the electropolishing compartment M the strip, which acts as the anode, is passed beneath the cathode member 22 while beme electrically connected to the positive electrode bar member 26 by means of the conductive brush bristle contact members 25.

The strip is maintained flat and uniformly spaced from the cathode 22 by means of the insulating rod members 28 which are spaced 'at intervals longitudinally of the strip beneath the cathode 22. The strip in this manner is made the anode and the electric current is uniformly distributed over the underside area of the strip and the cathode member comprises a sheet which is maintained in close proximity to the surface 30 of the strip so as to efiect an efllcient electropolishing of the same as the strip is moved along. The insulating rod members 28 may bemade of glass, hard rubber, synthetic resin or other electrical insulating material and preferably are of a thickness or diameter to enter the space between the cathode and the strip.

Where desired, suitable means may be provided for maintaining the electrolyte at a temperature which is required for effecting the electropolishing treatment.

Copper or lead may be used as the cathode material and the positively charged members 23 and 26 may be made of stainless steel or other suitable alloy metal which does not become passive in the electrolyte. Copper or brass may also be used for forming the bar 24 and bristle members 28 used for contacting the strip.

The electrolyte bath composition does not form a part of this invention and may consist of any one of the conventionally used electrolytic solutions which have been employed for this purpose.

After the electropolishing treatment of the strip II), it is passed into the rinsing compartmeat 15 which contains water or other appropriate substances and thence from the rinsing tank through a drier 33 and then over the guide roll 35 where it is brought in contact with the backing strip 38. The strip 38 preferably is of milder steel and forms a core member supporting the stainless steel strip I which is of comparatively small gauge thickness. The two-ply strip material is then passed through the set of roller dies 40 and the material pressed into the desired shape of moulding and the outer shell of stainless steel is locked or clinched onto the surface of the backing strip. After this operation, the moulding is passed between the bufiing wheels 42 to remove any scratches or blemishes caused by the roller dies to provide a finished moulding wherein the surface has a bright and mirro-like finish.

Where the roller dies are made of such material so that the surface of the moulding is not marred, the buffing wheels 42 may be omitted.

The backing strip 38 may be of any suitable gauge and is simultaneously unwound from the coil 45. The proper tension is maintained by the brake member 41, similarly as in unwinding the '5' estates conductivity since the grinding and polishing steps have been eliminated and the backing strip is only required to form a support for the more expensive thin shell-like stainless steel covering which forms the ornamental moulding. Ordinarily, however, the supporting strip for the highly polished outer surface ply will be of metal which can be cold worked into the desired shape of moulding. Where it is desired to have a moulding of very light weight, the backing or supporting strip may be made of aluminum or magnesium alloy steel which is very light and has a high tensile strength.

The finished moulding may have a cross sectional shape, such as indicated in Figure 4, wherein the moulding comprises an outer cover member 50 formed of the core 52. The inner edges of the outer cover portion 60 are clinched over the edges of the inner core member, as shown at 58, in order firmly to lock the two members togather forming a unitary structural member.

The electropolishing treatment, as diagrammatically illustrated in Figure 1, is similar to electroplating except that the flow of current is in reverse direction.

Where the cover strip which is to be electropolished is of suflicient thickness so that it can be readily supported on the bristle friction contact members 26 as it is passed along over the anode member 24, the insulating spacer rods 28 between the cathode 22 and the strip may be omitted. Preferably, the spacer rod disk-like wheel members 54 are shaped as indicated in Figure 3.

These spaced disk-like wheel members 54 provide point contact with the strip and cathode member whereby the strip is maintained at'a uniform distance from the cathode without interfering with the passage of electric current from the surface of the strip to the cathode. In this way, the highest efliciency of electropolishing can be effected over the entire surface area of the strip.

Solid rods in some instances may be substituted for the multiple disk-like construction of the members 28 where the current density and speed of the strip is such that proper polishing can be eifected without interference from the interposed rod members. It will also be understood that the spacer guide members 28 are suitably rotatably supported on the electroplating unit in order properly to guide the strip therealong between the anode and cathode.

In electropolishlng, high current densities may be used and electrolytes consisting of phosphoric acid, sulphuric acid, or mixtures of these with various additions of organic acids. Copper cathodes are preferably used where high current carrying capacity is required. The distance between the anode and the cathode must be carefully controlled and may be approximately onequarter to three inches or more depending upon the electrolyte, current density and particular strip material to be polished. When polishing strip material of varied shape, the cathode should be shaped to conform with the strip being treated so that the surface will coincide with that of the anode.

Some electrolyte baths may be efficiently operated at room temperature, while others should be maintained at a higher temperature, on the order of to 250 degrees F. Steam coils or other suitable means may be installed in the electrolyte tank compartment for raising the temperature of the bath when this is desired.

This invention is adapted for processing various types of structural members wherein a polished bright surface is to be provided by a surface shell-like covering. However, this invention may also be utilized in treating various types of strip material which are to be polished and fabricated into an article. Ordinary heavy scale is removed by a pickling treatment prior to electropolishing. This process may also be utilized in treating wire, band, sheet and spun shapes or castings and the like. Further, the apparatus and method herein described may be employed for electropolishing various types of metals other than stainless steels, such as copper, brass, nickel, Monel, cobalt, zinc, tin, lead, aluminum, iron and their alloys.

. It will be further understood that this invention is not limited to the particular details of the apparatus and method as described and that various modifications may be made by those skilled'in the art without departing from the spirit and scope of this invention.

Having thus fully described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In an electrolytic polishing and forming ap paratus for manufacturing a composite strip having a backing strip and a thin shell-like covering strip of electropolished metal of the class consisting of stainless steels, copper, brass, nickel, Monel, cobalt, zinc, tin, lead, aluminum, iron and the alloys of said metals in a continuous process, comprising the means for feeding a thin, shelllike covering strip through an electropolishing bath, means for supporting said shell-like covering strip comprising a plurality of electrically conductive brush bristle friction contact members, which members are located closely adjacent to each other as it is passed through said electropolishing path, said contact members forming a continuous support therefor and preventing bending or bowing of said strip during the electropolishing step.

2. In an electrolytic polishing and forming apparatus for manufacturing a composite strip having a backing strip and a thin shell-like covering strip of electropolished metal of the class consisting of stainless steels, copper, brass, nickel,

Monel, cobalt, zinc, tin, lead, aluminum, iron and the alloys of said metals in a continuous process, comprising means for feeding a thin shelllike covering strip through an electropolishing bath, means for supporting said shell-like coverin strip comprising a plurality of electrically conductive brush bristle friction contact members, which members are located closely adjacent to each other, as it is passed through said electropolishing path to form a continuous support therefor, and to prevent bending or bowing of said strip during the electropolishing step.

3. In an electrolytic polishing and forming apparatus for the manufacture of a composite strip having a backing strip and a thin shell-like covering strip of electropolished metal of the class consisting of stainless steels, copper, brass, nickel, Monel, cobalt, zinc, tin, lead, aluminum, iron, and the alloys of said metals in a continuous process comprising an electropolishing bath, spaced rollers, means for supporting said shelllike covering strip comprising a plurality of electrically conductive brush bristles friction contact members located between said rollers to support said strip as it is passed through said electropolishing path within said bath, said electrical friction contact members being located closely adjacent to each other and acting to prevent bending or bowing of said strip during the electropolishing step.

FOLSOM E. DRUMMOND.

DAVID E. BENCH.

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