US3825873A

US3825873A - Contact wheel assembly for strand annealing tubing

Info

Publication number: US3825873A
Application number: US00236759A
Authority: US
Inventors: J Herren; E Habdas
Original assignee: Universal Oil Products Co
Current assignee: Bank of Nova Scotia; Wolverine Tube Inc; Universal Oil Products Co
Priority date: 1970-03-12
Filing date: 1972-03-21
Publication date: 1974-07-23
Anticipated expiration: 1991-07-23

Abstract

A contact wheel assembly for use in conducting current to or from copper tubing engaged with the wheel. The wheel is peripherally grooved to receive advancing tubing and sparking is substantially eliminated by forming the tube contacting portion thereof of electrographitic material.

Description

nite States Herren et a1.

atent 1191 1 CONTACT WHEEL ASSEMBLY FOR STRAND ANNEALING TUBING Inventors: James L. Herren, Decatur, Ala.;

Edward P. Habdas, Dearborn, Mich.

Universal Oil Products Company, Des Plaines, 111.

Filed: Mar. 21, 1972 Appl. No.: 236,759

Related US. Application Data Continuation-in-part of Ser. No. 18,882, March 12, 1970, abandoned, which is a division of Ser. No. 706,589, Feb. 19, 1968, Pat. No. 3,518,405.

Assignee:

.U.S. Cl 339/8 R, 339/111, 339/278 D Int. Cl H01r 39/46 Field of Search "339/5, 6, 8, 9, 111, 278, 339/2; 191/45; 310/219-222, 232; 219/155,

References Cited UNITED STATES PATENTS 2,064,589 12/1936 Convers 339/6 A X July 23, 1974 11/1946 Lewis et a1 l9l/45 R 1111954 Darner 339/14 L X FOREIGN PATENTS OR APPLICATIONS 868,723 10 1941 France 339/278 D 105,930 4 1943 Sweden 504,328 8/1930 Germany 339/278 D Primary Examiner-Richard E. Moore Delknap [5 7 ABSTRACT A contact wheel assembly for use in conducting current to or from copper tubing engaged with the wheel. The wheel is peripherally grooved toreceive advancing tubing and sparking is substantially eliminated by forming the tube contacting portion thereof of electrographitic material.

10 Claims, 2 Drawing Figures FIGz INVENTORS JAMES L. HERREN ATTORNEYS CONTACT WHEEL ASSEMBLY FOR STRAND ANNEALING TUBING CROSS-REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of prior copending application Ser. No. 18,882, filed Mar. 12, 1970, now abandoned, which in turn is a division of prior application Ser. No. 706,589, filed Feb. 19, 1968, now US. Pat. No. 3,518,405.

BRIEF SUMMARY. OF THE INVENTION In accordance with the present invention, electrically conducting metal tubing, preferably of relatively small size as for example between A and 1 inch outside diameter, is continuously advanced between a pair of peripherally grooved electrical contact wheels separated by a distance selected in accordance with the density of current flow so as to bring the intermediate length of tubing to the required annealing temperature during transit between the wheels. Associated with the electrical contact wheels are guide wheels positioned to cause the tubing to bebent as it passes around a portion of the periphery of the contacting wheels. It has been found that harmful sparking occurs most significantly at the exit contact wheel, and accordingly, at least this wheel, and if desired, both electrical contact wheels, are provided with grooved peripheral portions of spark or arc suppressing material. Best results have been encounteredwhen the peripheral grooved portion of the contact wheels is formed of electrographitic material.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic elecational view showing the annealing equipment.

FIG. 2 is an enlarged fragmentary sectional view on the line 2-2, FIG. 1.

DETAILED DESCRIPTION While equipment has long been available for the purpose of strand annealing of straight material such as wire or rod, or strip, this equipment has proved unsatisfactory for annealing relatively thin-walled metal tubing. In accordance with the present invention the annealing equipment is provided in an arrangement illustrated more or less diagrammatically in FIG. 1. In this Figure there are provided a plurality of peripherally grooved guide and contact wheels, the guide wheel being provided at the tube entering end of the equipment, and the guide wheel 12 being provided at the tube exiting end of the equipment. Electrical contact wheels 14 and 16 are provided to engage an intermediate portion of the tube T. All of the wheels are mounted in relatively thin sealed

housings

18, 20, 22 and 24, and connecting

tubes

26, 28 and 30 are provided intermediate the housings to protect the tubing from oxidation. Preferably, a gas is introduced into the housing 24 in which the wheel 12 is located, and this gas may be deoxidizing natural gas or cracked gas. The gas is caused to flow successively through the housing 24, tube 30, housing 22, tube 28, housing 20, tube 26 into the housing 18 from which it exhausts. In addition, it is desirable to purge the inside of the tubing prior to bringing it to annealing temperature and this may be accomplished in any suitable manner by introducing a purging gas to one end of the tubing and blowing it through the tubing to expel all of the air from the interior.

The problem in annealing the tubing is of course to bring the tubing as it is continuously advanced, to the proper annealing temperature, after which the tubing is cooled or quenched as required, such for example as by passing it through a water bath or water spray. This is most conveniently accomplished during continuous advance of the tubing by causing the tubing to advance between a pair of electrical contact wheels 14 and 16 suitablly connected into an electric circuit so that the portion of the tubing which is intermediate the wheels 14 and 16 forms a part of the circuit. Thus, the portion of the tubing intermediate the contact wheels is heated by electrical resistance heating as it advances so that as it leaves the exit contact wheel 16 it is at the required temperature for further processing. I It is desirable to provide the

guide wheels

10 and 12 in such relationship to the contact wheels 14 and 16 so as to cause the tubing to be bent as it passes around the contact wheels so as to, have extended electrical contact therewith. This not only reduces the current desnity to safe values, but also tends to eliminate to some extent the undesirable flutter, vibration or bouncing which might otherwise occur as the tubing engages the contact wheels.

However, even with the most advantageous arrangement of contact wheels and guide wheels, it has been found very difficult to avoid harmful sparking between the tubing as it moves into and out of contact with the electrical contact wheels. This has been particularly harmful at the exit contact wheel 16. In the past contact wheels formed of copper have been used. Where the exit wheel is copper, the tube is at annealing temperature, for example, 1,400F., and at the temperature has its hardness substantially reduced, and is accordingly substantially softer than the contact wheel. When a spark occurred a sharp edged pit or crater was formed in the wheel or tube, and in some cases this had ridges or projections above the smooth surface in which the crater was formed. The crater formed by the spark in the tube was a defect which required that the cratered portion be discarded. More important however, the crater, or the projection adjacent the crater, on'the wheel made an impression on the tube every time rotation of the wheel brought the crater into contact with the advancing heat softened tube. This occurred repeatedly and caused an entire run of tubing to be defective. Since the relatively cool metal of the wheel was harder than the heat softened metal of the tube, this irregularity in the wheel remained indefinitely, and produced a corresponding irregularity in the tube at each revolution of the wheel. This required that the operation be stopped and the wheel stoned or otherwise machined to remove the crater and any adjacent projections on the wheel.

' In accordance with the present invention, this harmful sparking, which previously produced burned areas on the tubing and also produced pitting of the tube and wheel, has been largely eliminated and substantially reduced in severity by forming at least the exit wheel 16 in an arrangement best seen in FIG. 2. More important, the repeated blemishing of the tube by repeated engagement between a spark deformed portion of the wheel and the heat softened tube is eliminated as will subsequently be described.

As seen in this Figure, the wheel 16 is carried by a shaft 32 which extends through an opening 34 in the housing 22. The opening is sealed by a suitable seal indicated generally at 36 which prevents escape of the deoxidizing gas circulated through the housing 22. The wheel assembly 16 comprises the wheel 38, which may be formed of copper or aluminum, and is attached to a flange 40 on the shaft 32 by suitable means such as screws 42. At the periphery of the metal wheel 38'is an annular electrical contact ring 44 provided with a peripheral groove 46. The contact ring 44 is secured to a mounting ring 48 by screws 50, the mounting ring 48 in turn being attached to the wheel 38 by mounting screws 52.

The groove 46 in the contact ring is preferably provided with straight side walls having an included angle of approximately 60 and terminating in a circular fillet at the bottom having a radius somewhat less than 0.200

inch. The material of the contact ring 44 is a spark suppressing material and excellent results have been obtained when the material is an electrographitic material of the type commonly used for electrical contact brushes. A suitable material for this ring is furnished by the General Electric Company under their grade designation of ME18 brush material and is described by the supplier as an electrographitic material of moderate hardness, the final product being of a fairly highly graphitic nature. The material is described as having the following physical properties:

Density 1.65 Hardness (Shore Schleroscope) 50 Compressive Strength 6.500 PSI Transverse Strength 3,800 PSI Modulus of Elasticity PSlXlO 1.2 Temperature Limit:

Neutral Atmosphere 5000F.

Oxidizing Atmosphere 750F. Coefficient of Thermal Expansion 3.0 in./in./CXlO Permeability p. Darcys 35,000 Max. Grain Size 0.003"

One of the problems which is involved is relative slippage between the tubing and the peripheral portion of the electrical contact wheels due to the expansion of the tubing as it is brought to annealing temperature. Preferably, all of the

wheels

10, 12, 14 and 16 are driven at uniform peripheral speed. The electrographitic peripheral portion of the electrical contact wheels apparently facilitates this slippage without particular wear on the groove 46. Tests indicate that a contact ring 44 formed on the electrographitic material described will have a useful life of over one year, operated two shifts a day, or a life expectancy of 2 years if operated only a single shift a day.

Another benefit of the electrographitic material is its low frictional coefficient with copper. Because of the tensile weakness of a light walled copper tube at l,200-1,400F. it cannot tolerate any mismatch in peripheral speed of the wheels. It will readily be pulled apart should this occur with metallic wheels or wheels of high coefficients of friction. With the graphite wheels disclosed herein this tendency is largely eliminated.

Obviously, some wear occurs on the graphitic wheel and the depth of groove increases and the nature of contact varies. Initially, the contact between the sides of the wheel and the outer surface of the tubing is theoretically two-line contact extending along spaced portions of the tubing.

As the groove in the contact ring wears, the area of contact increases until eventually, the tubing has a sigle relatively large area of contact. However, the wheel operates efficiently without producing serious sparking problems even during initial wear or break-in, and as indicated above, continues to operate with an extremely long life expectancy.

The fact that the graphitic material wears is an added advantage since spark caused local imperfections in the wheel are eliminated as material of the wheel wears away.

The electrographitic material forming the contact wheel is substantially softer than the copper contact wheel previously used and this tends to prevent marking of the tube by sharp edges of pits or craters and the ridges or projections surrounding them, as occurred when using copper contact wheels.

While the electrographitic material of the ring 44 has desirable wearing properties in contact with the advancing tubing, the material is relatively brittle and it is preferred to additionally support the ring by a clamping or support ring 54 which engages most of the outer area of the contact ring 44 and is retained in position by a multiplicity of mounting screws 56.

In order to dissipate heat from the structure, it is desirableto provide a water spray directed against the outer surface of the wheel 38 and a suitable nozzle for this purpose is indicated diagrammatically at 58. In order to prevent the water from this spray from reaching the groove 46 in the contact ring 44, the mounting screws 56 which attach the ring 54 to the wheel 38 also mount a dished guide plate 60 in the relationship illustrated in FIG. 2, which serves as a deflector for preventing water from flowing around the underside of the wheel into the contact groove 46.

While the electric current may be supplied to the contact ring 46 through the shaft 32 and the wheel 38, it is preferable to provide a shorter flow path by mounting brushes 62 within the housing 22 in contact with the mounting ring 48 and in close proximity to the contact ring 44. As illustrated in the Figure, the brushes 62 are maintained in contact with the mounting ring 48 by compression springs 64 located in hollow mounting brackets 66. The electrical wiring 68 extends through an opening in the housing provided with a gas-tight seal 70.

The location of the brushes 62 is indicated in FIG. 1, and in order to balance the slight thrust of the brushes imparted by the compression spring 64, rollers 72 are provided to engage the surfaces of the mounting ring 48 diametrically opposite to the portions thereof engaged by the brushes 62.

What we claim as our invention is:

1. An electrical contact wheel assembly for use in tube annealing equipment comprising an inner wheel, a contact ring surrounding and carried by said inner wheel, a mounting ring having its inner peripheral portion secured to a side of the inner wheel adjacent its periphery and extending radially therebeyond and engaging one side of the contact ring, said contact ring being formed of spark suppressing material.

2. A wheel assembly as defined in claim 1 in which said contact ring is formed of electrographitic material.

3. An assembly ring as defined in claim 1 comprising a clamping ring having an inner peripheral portion secured to the opposite side of the inner wheel adjacent its periphery and extending radially therebeyond into engagement with the other side of the electrical contact ring.

4. An assembly as defined in claim 3 comprising an annular dished water deflector carried by said clamping ring.

5. An electrical contact wheel assembly for use in tube annealing equipment comprising a circular metal wheel, an annular electrical contact ring carried by the periphery of said wheel, said ring being formed of spark suppressing material, a contact brush engageable with a side of said wheel adjacent the periphery thereof to provide a short path for electric current flowing between the brush and said electrical contact ring, and a roller engageable with the peripheral portion of said wheel at the same side as and at a point substantially 6 equipment for annealing copper tube comprising a wheel having a peripheral grooved tube contacting portion formed of electrographitic material having spark suppressing qualities.

7. An assembly as defined in claim 6 in which said electrographitic material is brush material of moderate hardness.

8. An assembly as defined in claim 6 in which said electrographitic material has a hardness of about 50 on the Shore Schleroscope.

9. An electrical contact wheel assembly for use in equipment for annealing copper tube comprising a wheel having a peripheral grooved tube contacting portion formed of electrographitic material in which said electrographitic material is characterized by low friction properties to provide for slippage between a tube being annealed and the wheel, and spark suppressing diametrically opposite to the area of engagement of said contact brush with the wheel.

6. An electrical contact wheel assembly for use in properties. g

10. An assembly as defined in claim 9 in which said electrographitic material has a hardness of about 50 on the Shore Schleroscope.

Claims

5. An electrical contact wheel assembly for use in tube annealing equipment comprising a circular metal wheel, an annular electrical contact ring carried by the periphery of said wheel, said ring being formed of spark suppressing material, a contact brush engageable with a side of said wheel adjacent the periphery thereof to provide a short path for electric current flowing between the brush and said electrical contact ring, and a roller engageable with the peripheral portion of said wheel at the same side as and at a point substantially diametrically opposite to the area of engagement of said contact brush with the wheel.

6. An electrical contact wheel assembly for use in equipment for annealing copper tube comprising a wheel having a peripheral grooved tube contacting portion formed of electrographitic material having spark suppressing qualities.

9. An electrical contact wheel assembly for use in equipment for annealing copper tube comprising a wheel having a peripheral grooved tube contacting portion formed of electrographitic material in which said electrographitic material is characterized by low friction properties to provide for slippage bEtween a tube being annealed and the wheel, and spark suppressing properties.