US3451903A - Conductor roll and method of making the same - Google Patents

Description

n 1969 SHURO MATSUOKA 3,451,903

CONDUCTOR ROLL AND METHOD OF MAKING THE] SAME Filed March 29, I966 INVENTOR. SHURO MHTSUOKPI BY M mm, W

United States Patent US. Cl. 204-25 5 Claims ABSTRACT OF THE DISCLOSURE An electrically conductive roller includes a pair of axially spaced shafts each having a widened portion or bos which is arranged at respective ends of an electroformed copper roller cylinder or shell. The bosses are fixed to the shell by a shrinkage fit and the outer surface of the shell is plated with an abrasion and corrosion-proof metal. The conductive roll is manufactured by the electrodeposition of pure copper over a cylindrical conductor in order to form a layer of relatively great thickness. The conductor is then removed from the deposited copper to provide the outer copper shell. The inner and outer surfaces of the copper shell are then finished to the desired dimensions by machining and shaft elements having bosses are secured into the respective ends of the shell by means of a shrinkage fit preferably with the temperature maintained not higher than 200 C. Thereafter, the outer surface of at least the shell is electro-plated with an abrasion and corrosion resistant metal.

This invention relates in general to the construction of electrically conductive rollers or rolls and to a method of making such rollers and in particular to a new and useful electrically conductive roller made with separate end shafts having bosses thereon upon which a cylindrical shell of pure copper is fitted and including a plating over the shell and the sides of the end bosses of an abrasion and corrosion proof metal.

This invention has particular application in respect to the formation of conductor rolls for supplying an electric current to a metal piece during the continuous electrochemical treatment thereof, for example, to effect the cleaning, pickling or electroplating of metal such as steel strips.

In a continuous operation for plating metal strips, for example, a large amount of current ranging from about 5,000 to 20,000 amperes is applied to a conductor roll of this type. Therefore, the electric resistance of the roll and the conditions of roll surface in contact with the metal piece largely influence the processing capacity of the roll in the treatment of metal and the quality of the metal product. If the conductor roll has a large electric resistance, power loss is of course increased and the supply voltage must be elevated. This may cause sparking between the roll and the metal piece during operation, and the development of heat in the roll accompanied by a temperature rise of the metal piece and, thereby, of a plating bath, with consequent deterioration of the plating effect. Also, minute pinholes and other defects on the roll surface, if any, invite localized arcing which produces defects, so called arc spots on the plated articles. The roll itself is damaged by the arcing and its life is shortened considerably. It is important for this reason that a conductor roll of this type should have as little an electric resistance as possible and the heat developed by the electric resistance of the roll itself and the contact resistance between the surfaces of the roll and the metal piece during operation should be efficiently led into a cooling zone inside the roll in order to improve the cooling of the roll surface.

Conductor rolls heretofore in use have a roll shell which is made of a metal having high electric and thermal conductivities such as copper. The material should be of high purity and also as hard as possible in order to extend the roll life and in particular to increase the pressure resistance of the roll surface.

To meet these requirements, many of conventional conductor rolls comprise each a shell of seamless copper pipe of large size manufactured, for example, by the Mannessman rolling process. Usually the shell is supported by bosses of copper alloy or of steel press-fitted or welded to the both ends of the shell, and main shafts are fitted in the center of the shell, the shell being plated with chrome or nickel on the circumferential surface. However, the large size copper pipes have low hardness and low yield point because they are formed at elevated temperatures, and moreover, the shell becomes softer when it is welded to the bosses. Roll shells formed of such copper pipes therefore fail to have a sufficient durability. Especially the low pressure resistance of shells tends to cause dents 0r deformations. Furthermore, numerous pinholes on the surface of such rolled copper pipes exist for the pipes have minute pinholes inside. Shells of this kind are not satisfactory either in respect to the purity of the copper material or in respect to their surface conditions.

Other methods of fabricating roll shells include welding of two arcuately curved copper plates toegther into. a cylindrical form and the centrifugal casting of largesize copper pipes for use as shells. In the former method, high-purity copper cannot be used because of the difficulty which is encountered in welding the two plates. Moreover, each of the weld joints of copper alloy which are inevitably formed along the length of the roll shell has a particularly high electric resistance, which in turn causes localized current fluctuation against the metal piece during operation. Other disadvantages include the poor electrode-position property of the joints in chrome plating of the shell surface, which makes it impossible to have a satisfactory roll finish.

In the casting process for the manufacture of copper pipes, a larger number of blowholes are formed inside than in the case of the abovementioned rolled pipes, and cast-copper pipes are extremely soft, and therefore the resulting shell surface are very unsatisfactory and the pressure resistance of the roll surface is low. In addition such cast-copper pipes have low purity and poor electric conductivity which are accentuated by the presence of blowholes.

Still another method of making conductor rolls has been proposed which consists of fixing a steel drum to a steel shaft with end supporters, enclosing the shaft, supporters, and drum in a casing of cast copper which has a relatively great wall thickness, and then plating the casing surface with copper and chrome to form a plurality of thin plated layers. Rolls produced in this way have a relatively great structural strength. However, because they are composed essentially of cast copper, they are practically as defective as the above-described cast-copper pipes in respect to pressure resistance of the roll surface and electric conductivity. Further, because the roll shell has an internal layer of steel, heat transfer to the inner cooling zone is not adequate and the cooling efiect attained on the roll surface is insufficient.

In accordance with the present invention the defects of the prior art structures are avoided and there are provided conductor rolls having a roll shell formed of hard, dense and pure copper with a very limited amount of impurities, and having very good electric conductivity with adequate cooling means. In addition, a roll shell is provided with great pressure resistance, Which is free from pinholes, blowholes and other defects in the surface and sub-surface layer of the roll. The invention includes a conductor roll which comprises a shell, a pair of main shafts, and a pair of bosses fixed to the main shaft for supporting the shell concentrically to the shafts. The shell consists of an electro-formed cylinder of pure copper. The shell alone or both the shell and bosses are covered by an abrasionand corrosion-proof metal such as hard chrome or nickel.

Accordingly, it is an object of the invention to provide a conductor roll having a roll shell formed of copper having good surface characteristics and uniformly good electrical conductivity and with great pressure resistance.

A further object of the invention is to provide a conductor roll including a shell of an electro-formed cylinder of pure copper fitted over bosses carried by axially spaced shaft elements and with a plated coating of an abrasion and corrosion resistant metal over at least the shell.

A further object of the invention i to provide a method of manufacturing a conductor roll comprising electrodepositing pure copper to form a cylinder, finishing the inner and outer surfaces of the cylinder, fitting the cylinder over end bosses of main shafts and plating at least the cylinder with an abrasion and corrosion resistant metal.

A further object is to provide a conductor roll which is simple in design, rugged in construction and economical to manufacture.

The invention will be described in more detail with reference to typical embodiments thereof shown in the accompanying drawings, in which FIG. 1 is a longitudinal sectional view of a conductor roll embodying the invention;

FIGS. 2 and 3 are respective longitudinal sectional views of two other embodiments of the invention; and

FIG. 4 is a perspective view illustrating a method of manufacturing a conductor roll in accordance with the invention.

Referring to the drawings in particular the invention embodied therein in FIG. 1 includes a conductor roll 50 formed of axially spaced main shafts 1 and 1a provided with respective central passages 2, 2a for cooling water. A boss or drum support 3 of copper alloy castings are secured to the respective main shafts 1 and 1a. The bosses 3, 3 include axial hub portions 4, 4 having outer ends which are soldered as shown at 5, 5 so as to be water-tight. Copper disks or plates 6, 6 are soldered or welded to the inner ends of the main shafts 1 and 1a, respectively. The disks 6, 6 are each provided with a plurality of holes or through passages 7, 7 for circulating cooling water in the vicinity of the outer periphery of each plate.

A roll shell 8 which is electro-formed from pure copper by the method described hereafter is fitted over the spaced bosses 3, 3 and secured thereon by shrinkage fit. The outer surface of the shell 8 and those of the bosse 3, 3 are further plated with hard chrome or nickel 9.

The main shaft 1 is provided with a cross passage 10 which receives water from the inlet passage 2 and delivers it into the drum space as needed for cooling. An outlet pipe 10a for discharging cooling water is fixed to the opposite shaft 1a and communicates with the outlet passage 2a.

Other embodiments of the invention will be described hereunder with reference to FIGS. 2 and 3 of the accompanying drawings with reference to modified conductor rolls 50' and 50" which have parts similar to the roll 50 and which are similarly designated.

In fitting the bosses 3, 3 to respective ends of the shell, even if the said shrinkage fit is adopted, there is a possibility that a sufficient coherence between the bosses and shell will not be obtained because of manufacturing errors.

Accordingly, in these embodiments, watertight rings 11, 11 held by respective retainer plates 12, 12 which are bolted on the end surface of the bosses 3, 3 as shown in FIG. 2, or solderings or low temperature brazings 13, 13 are provided on the circumferential juncture of the end surface of the shell 8 and the bosses 3, 3 as shown in FIG. 3, so that more assurance of water tightness inthe roll is obtained.

The method of manufacturing the conductor roll of the invention will be described hereunder especially with reference to FIG. 4. First, a cylindrical conductor is made by winding a copper plate 15 about 0.5 millimeter in thickness around the circumference of a cylindrical core 14 e.g. of wood, as shown in FIG. 4, and fixing the copper plate 15 to the cylindrical core 14 with nails 16, 16. The exposed nail heads and the overlapped portion of the copper plate are covered with solder. Secondly the cylindrical conductor is dipped in a plating bath and is revolved therein for thick electro-deposition with pure copper. When the deposit has obtained a predetermined thickness, the cylindrical conductor is taken out of the bath, and the core 14 with the end plates 17, 17 are removed leaving the copper plate 15 behind, and then copper plate 15 is removed by mechanical cutting. The cylindrical core 14 may comprise any of certain materials which can be relatively readily broken and removed, for example, synthetic resin, wood etc. and carbon black powder or the like may be applied thereon as an electrode extending over the circumferential surface of said cylindrical core 14 instead of the metallic plate 15 as above mentioned.

Further, in case of electro-depositing of pure copper, in order to make the electro-deposited pure copper base as hard and dense as possible, it is preferred to use an alkaline plating bath prepared from an aqueous solution of sodium cyanide or potassium cyanide and cuprous cyanide with the addition of a suitable brightening and reveling agent such as potassium thiocyanate and potassium tartrate. For effecting the electro-deposition, high-purity copper electrodes are placed in the plating bath, and the cylindrical core 14 around which the plate conductor 15 is wound is dipped in the bath between the electrodes. Period reverse current plating, or other type of current change is applied between the copper electrodes and the core surface to provide a smooth electrode-deposit while the core is in revolution.

After an electro-formed pipe of pure copper thus formed is finished on both inner and outer surfaces by machining to predetermined dimensions, bosses 3, 3 and disks 6, 6 fixed to main shafts 1 are tightly shrinkage-fitted into the shell 8 as shown in FIGS. 1 to 3. Finally the periphery of the shell and bosses are plated with hard chrome or nickel.

To fix the bosses 3, 3 to both ends of shell 8, both welding and low temperature brazing are not desirable because the former causes softening of the shell and the latter does not permit firm fixing.

Although press fitting is possible in fixing the bosses 3, 3 to both ends of the shell 8, it is realized that the tightness between the shell and bosses may break down due to different thermal expansion coefficients and that slipping between the shell and bosses and leakage of cooling water in the roll may occur while the conductor roll is under operation.

Therefore, it is advisable to fix the parts in place by shrinkage fit as in the embodiments illustrated or by cold shrink fit. In effecting shrinkage fit, it is important to heat the shell 8 to a temperature not higher than 200 C., in order to avoid Softening of the shell.

3,451,903 '5 6 The mechanical properties, electrical properties, purity necessary for ordinary rolls of rolled or cast copper pipe and content of foreign elements of the copper base of and hence the repair work can be accomplished within conductor roll according to the invention which have so a short period of time. In brief, it is possible according far been described with reference to three embodiments to the invention to obtain a conductor roll much superior thereof are compared in the following Table l and Table to any conventional one, by the use of a cylinder of elec- 2 with those of conventional conductor rolls. tro-formed pure copper as the shell of the conductor roll.

TABLE 1.COMPARISON OF MECHANICAL AND ELECTRICAL PROPERTY AND PURITY Hardness Yield Tensile Purit Electric (Vickers) point strength (percent conduc- (kg. (kg/mm?) tivity (IACS mm!) percent) Copper base of conventional conductor roll (reduced copper, grade 2) 30-75 5-8 18-25 97. 0-99. 95 30-85 Copper base of conductor roll of the invention (electro-formed pure copper) 120-170 -30 -45 99. 96-99. 98 100-103 TABLE 2.COMPARISON OF CONTENT OF FOREIGN ELEMENTS (PERCENT) As Si P S Fe Pb Copper base of conventional conductor roll (reduced copper,

grade 2) 0. 0013-0. 0018 0. 0012-0. 0014 0. 035-0. 045 0. 003-0. 006 0. 0l-0. 03 0. 01-0. 03 Copper base of conductor roll of the invention (electro-formed pure copper) 0. 001-0. 002 0. 0005-0. 001 0.000 0. 002-0. 005 0. 001-0. 008 0. 003-0. 002

As will be clear from the above Table 1, in terms Thus, the invention is very useful from the industrial of mechanical properties, especially in hardness and yield standpoint. point which have a close relation to deformation of the 25 While specific embodiments of the invention have been roll surface, the copper base of the roll shell of the inshown and described in detail to illustrate the application vention has a hardness 1.6 to 3 times greater than that of of the inventive principles, it will be understood that the conventional copper plate a d r ll d copper pipe, nd invention may be embodied otherwise without departing is 3 to 6 times greater in yield point. With these prop- 30 from Such P p erties, the pressure resistance of the roll surface and What is claimed is:

durability of the roll as a whole are considerably in- 1- A conductor roll comprising a shell, a pair of main creased resulting in a very long service life of the roll, f and a S fi to e of Said Shafts a forming and the maintenance cost can be considerably reduced bea Supporting Surface for Supporting Said Shell concencause repairing times of chrome plated surface are rely to said Shafts, d shell comprising an electrocreased at least one third of those of conventional rolls. 3 formed ylinder of pure copper, the outer surface of said Also the conductor roll made in accordance with the Shell h g Plated With an ahYasioll-ahd'cormsiolhpmof present inve tio us a h ll having a v hi h copper metal, said bosses being fixed to said shell by a shrinkage base purity of 99.6-99.98 percent. The copper base confittains only traces of such other elements as phosphorus, 4 A Conductor r011, according to claim including a silicon, arsenic, and iron which affect the conductivity of waterjtight g located at the Circumftirential j t copper seriously when each of them is present in an of Sald Shell With a h f said bosses. amount of only 0.02 percent or more as foreign matter. A cohdllctof F011, achordltlg f f lnchldlhg Especially, in content f phosphOrus Whl-ch has the most solder applied along the circumferential uncture of said remarkable effect to the conductivity, the copper base of shell Wlth each of Sand bossesthe conductor roll according to the invention has a value A method of manufacturmg a Conductor roll formed f a shell a pair of main shafts and a pair of bosses 1 0 a gg ii g f g f i fgizg g i g g g lg i zg fixed to said main shafts for supporting said shell concenc b y H e n d P u trically to said shafts, comprising electro-depositing copas compared Wlth or nary asesence a uctor r0 per over a cylindrical conductor to form a layer of relacomprising Such a copper base minimizes Power loss on tively great thickness comprising a shell, removing the that during Operation with a great economical a conductor from the shell, finishing the outer and inner Vahtage- A130, the current p y to 111165 can be surfaces of the copper shell by machining to predeter- Creased and the Voltage can be lowered for the Opera mined dimensions, fixing the bosses securely into both tion, 80 that a p t h y 0f p g t h the F011 and ends of the shell by a shrinkage fit, and electro-plating the a work can be ellmrnated in processing lines such as outer surface of at least the shell with an abrasion and corchrome plating lines where a large current density is rerosion resistant metal. quired. Furthermore, thanks to the highly conductive 5. A method, according to claim 4, wherein the shrinkcopper base, the conductor roll according to the inveng fit is carried out at a temperature of not higher than tion develops little heat, the shell has a high thermal conductivity, and the cooling effect of the roll surface is very References Cited good.

In the conductor rolls of the invention, the copper UNITED ST ATES PATENTS base of shell consisting of electro-formed pure copper has 2,754,485 7/1956 Wlck et a1 204 279 a very dense structure and is free from any blowholes 2958742 11/1960 Palmer 204 279 which are usually found in cast copper. Hence, the roll 2975110 3/1961 h 204 9 surface has neither pinhole, blowhole nor other hollow 3374165 3/1968 OBnen et a1 204*279 defects, permitting very satisfactory finishing by hard FOREIGN PATENTS chrome plating or nickel p 453,644 12/1948 Canada.

Thus, according to the present invention not merely ideal roll surface conditions are obtained but the main- JOHN H. MACK, Primary Examiner.

tenance cost for the roll surface can be saved consider- T TUF ably because, when the chrome plated surface is damaged ARIELLO Assistant Examme" due to prolonged use of the roll and has to be repaired, US. Cl. X.R.

there is no need for filling pinholes on the surface as is 204-9, 279

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