US2604751A - Composite spinning bucket - Google Patents

Description

July 29, 1952 H. D. HALEY comPosrrs SPINNING BUCKET Filed March 20, 1950 HUI III

INVENTOR. 'HUGH D- HALE) TORNIY.

Patented July 29, 1952 1 COMPOSITE SPINNING'EUCKET Hugh l). Haley, Drexel Hill, Pa., assignor to American Viscose Corporation,

Wilmington,

DeL, a corporation of Delaware Application March 20, 1950, Serial No. 150,741

8 Claims.

This invention relates to spinning buckets of composite construction and particularly to metal buckets which are coated with a corrosion-resistant material. 7

Spinning buckets fabricated from materials such as aluminum, magnesium, titanium, or alloys thereof, or stampings of stainless steel have the obvious advantagesof being lighter in weight, consuming less power, requiring smaller spinning compartments, and producing less windage within a spinning compartment. In general, however, the metals which have the desirable weight and strength properties which make them suitable for being fabricated into buckets are not resistant to attack from the corrosive materials which enter into or accompany the process of obtaining a regenerated cellulose yarn from a viscose solution. Although metal buckets are now commercially used to some extent, their use is limited to carefully controlled conditions of operation under which cloning is accomplished without removing the buckets from their nests; the use of picks or other devices which might'perforate the coating is prohibited; and mechanical or electrical decelerating devices are provided for individual buckets to eliminate the practice of applying a canvas brake or lever drake to the rim to stop the rotating bucket.

Extensive substitution of buckets of composite construction constituted primarily of metal has been substantially hindered by the lack of suitable materials which may be applied to the metal. Such materials, in addition to being chemically resistant, must be able to satisfactorily resist abrasion, sending and erforation to which the outer surface of the bucket is subjected particularly when the buckets are removed from spinning equipment for doffmg. Furthermore, the material applied to the metal should have surface properties such that the cake readily separates from the cake-forming surfaces of the bucket. I

-t is an object of this invention to provide high-strength light-weight spinning buckets having great corrosion resistance, resistance to abrasion and scuffing, and desirable surface characteristics conducive to the facile separation of the cakes from the buckets. Another object is to provide inexpensive buckets of simplified and thin-walled construction. Other objects, fea tures and advantageswill be apparent from the following description of the invention and the drawing relating thereto in which:

l is a section in elevation taken along the axis of. a bucket having a composite construction in accordance with the invention;

2 is a fragmentary sect-ion of a bucket and a cover therefor of modified construction; and

Fig. 3 is a fragmentary section of a bucket and a cover therefor illustrating another construction.

According to the invention, a spinning bucket and a lid or cover therefor, each of which may be of composite construction, comprise body members of which the outer and inner surfaces are in adhesive contact with a layer of protective material having as a principal ingredient a polymeric product of a fiuorinated ethylenic monomeric material. The layer or coating of this invention provides extraordinary protection against corrosion and abrasion in addition to having such surface characteristics as to facilitate the separation of cakes from the bucket and protecting the body members from impacts which normally cause bruising and chipping.

Fig. 1 illustrates the bucket 5 and a cover 6 secured Within the rim of the bucket by a lock ring 8. The bucket comprises a base member ill fabricated from a high strength material; for example, from metals such as aluminum or magnesium, or alloys thereof, stainless steel, or nickcl-molybdenum-chromium-iron alloys such as manufactured under the name Hastelloy by the Haynes Stellite Company, or from phenolformaldehyde regime. The member it is coated with a composition which is essentially a polymerized product of a fluorinated ethylenic compound. The composition in accordance with the invention which apparently gives the best corrosion and abrasion resistance is prepared from the polymer of the ethylenic compound having the maximum substitution of fluorine for hydrogen, i. e., tetrafluoroethylene. Because of the apparent lack of melting point of this polymer and its tendency to pass from the solid stage directly into the vapor stage, it is the most diilicult to apply of the materials under consideration in connection with this invention.

Other fluorinated polymeric materials closely chemically related to polytetrafiuoroethylene are those derived from other ethylenic monomers which are halogenated by fluorine. Of this group, polytrifiuorochloroethylene is a material having desirable properties which make it suitable a coating material for the buckets. Since the polymer of trifiuoroohloroethylene has a well defined melting range, it may be melted and then applied to the metallic bucket members by a dipping procedure, The polymers of difluorodiclrlloroethylene, vinylidene fluoride, and vinyl fluoride are also materials with which to form the outer layer of the buckets. I'nese and the other fiuorinated ethylenic compounds under consideration may also be copolymerizedaccordmodified 'ing to known procedures, and polymers of these compounds may be mixed together, to produce the surface iayer oi buckets constructed as herein described. Because of the difficulty of. finding suitable solvents in which to dissolve 'the'fiuorihated compounds under consideration, a practical method of applying such compounds is to prepare a stable aqueous dispersion of suitable concentration of colloidal particles, such as produced in the original polymerization medium, and to spray the dispersion onto the metallic body members of the bucket and/or cover. The members may also be dipped into th dispersion. A smooth and film-like coating may be thereafter obtained by heating the sprayed or dippedmember to the fusion temperature of the previously dispersed material. A procedur of this type is hereinafter described in greater detail with respect to polytetrafiuoroethylene.

The waxy-feeling surface characteristic of the polymeric products which constitute the surface layer of the buckets constructed according to the invention, and so beneficial in facilitating the separation of cakes from the buckets, is more pronounced in the polymers of greater density particularly polytetrafiuoroethylene. This correlation is-emphasized in other polymers of which the original monomers are of the symmetrical molecular structure such as vinylidene fluoride.

The higher density of such monomers appears to'be due to the closer molecular packing possible when such monomers are polymerized.

The cover 6 of Fig. 1 comprises a stamping or other fabrication I of sheet metal coated with a material of the type herein described. By using a thin-sectioned cover of this type, the distance between the seating surface H. for the cover provided in the rim M of the bucket and the lock ring groove I5, is smaller than is usual in the construction of spinning buckets. the bucket may therefore be constructed with a smaller width and with less weight. With a lighter rim and a light-weight cover, the total weight of the bucket is substantially reduced. However, when desired, a bucket or a cover constructed'in a conventional manner such as from a composition comprising a thermosetting resinous material and a fibrous filler may be used in combination respectively with a cover or bucket constructed accordingly to the invention. For example, a cover of the type extensively used in spinning equipment, formed from a phenol-formaldehyde condensation product and a fibrous filler and known as a Bakelite cover may be used in place of the cover 6 of Fig. 1 with the bucket 5.

To produce a suitable layer of polytetrafiuoroethylene on the metallic members I and [0, a dispersion of polymerized resinous product of tetrafluoroethylene is prepared, preferably by concentrating the original polymerization dispersion to 40 to 70% solids and dispersing it in an aqueous medium containing a surface-active agent such as an octylphenol-polyethylene-oxide condensation product, polyammonium styrenemaleamate, poly-N-vinyl-caprolactam, dicctyl ester of sodium sulphosuccinate or ammonium stearate. The surface of the metal members is preferably roughened to receive the dispersion such as by etching with acid or caustic, sand blasting, or abrading with fine emery stone or cloth. The dispersion is applied readily with an air gun such as used for painting, or by dipping the members into a bath of the dispersion. The thickness of the coating is controlled most readily in the spray method, but in the dipping process, the rate of withdrawal of the members from a bath comprising the dispersion may be varied to obtain a desired thickness.

It, is preferable to build a layer of the polymer The rim of on the metallic member in several thin applications so as to avoid cracks which may result from too great a deposition of the dispersed material between successive heat treatments. After each application the deposited material is permitted to air dry until a period has elapsed which is generally indicated by a color change of the dispersed material. The coated member is thereafter placed in an oven and baked at approximately 700 F. until sintered. It is possible by this procedure to build the layer to a thickness of 0.005 to 0.010 thousandths of an inch. In building the protective layer, the depositions which precede the final one may be heated to such a degree as to only partially coalesce or fuse the polymeric particles so as to provide a somewhat rough surface to which the later-applied deposition will adhere. osition is applied, the coated article may be heated to somewhat higher temperature than during previous baking periods to produce a smooth finish.

Fig. 2 illustrates a bucket 20 and cover 2| therefor of modified design. Both the bucket and the cover are formed from a metal such as aluminum. The bucket is normally produced from a forging and the cover readily formed from a blank of sheet metal by stamping and/or metal-spinning technique. The metallic portions of the bucket cover are coated as hereinbefore described. Due to the tendency because of surface tension of a liquid material, such as a coating material being applied in the form of a dispersion, to thin out over sharp corners, it is desirable to avoid sharp edges or corners in the construction of the base members of the bucket and the cover so that the coating may be applied in substantially uniform thickness over all surfaces.

The cover 2! is provided with a depression 24 which gives its surface a contour which approximately mates the rounded-corner surface of the bucket at 26. The lid being recessed in this manner has greater rigidity. The cover 2| is also shaped to provide a groove 28 for a resilient ring 21 having a maximum diameter such that the cover must be gently pushed to position it within the bucket rim. Formation of the outwardly-facing groove 28 of the cover of the flange produces an inwardly-facing groove 3| which may be utilized, if desired, as a finger grip in removing the cover. The ring 21, of course, firmly holds the bucket rim as the bucket reaches normal spinning speed. The inner surface 29 of the bucket rim may be tapered slightly, if desired, to a greater diameter in a direction toward the seating surface 30 for the cover so that as the ring 2'! extends firmly against the bucket rim as the bucket comes up to spinning speed, the expansion of the ring against the rim surface will tend to thrust the cover in an axial direction toward its seating surface. A plurality of grooves 32 are provided at uniformly spaced points along the rim through which liquid may escape from the interior of the bucket. The groove 32 extends from the top of the bucket rim and along the seating surface to connect with the interior of the bucket as shown in Fig. 2.

Fig. 3 illustrates a modified bucket cover of simplified and inexpensive design which may be used in some of the more modern plants wherein the bucket is not removed from its driving spindle during doffing, and stopping or deceleration of individual buckets is accomplished by a reversing switch, or other mechanical or After the last dep-.

electrical means, without resorting to the common practice of manually applying a piece of canvas or other frictional braking means to the rim of the bucket. As shown in Fig. 3, the bucket 35 is formed without the conventional enlarged rim section. A lid 36 is insertable into the upper portion of the bucket and seats on the upper edge of the bucket when the radially extending flange 38 of the lid engages the edge 31. The metallic base member 39 of the lid 36 may be readily formed by stamping and/or by metal spinning from any suitable sheet metal material. The cover is provided with a groove to accommodate a ring 40 of resilient material which expands against the bucket wall in the manner described for ring 21 of Fig. 2. The portion of the cover which forms the groove defines a groove or pocket 42 analogous to the groove 28 in Fig. 2 wherein an operators fingers may be inserted to remove the ring from the bucket. If desired, small holes 45 may be provided through the fiange of the cover along the groove 42 through which any liquid accidentally deposited on the top surface of the cover may be centrifugally discharged. Such covers may also be removed readily by a tool which has resiliently tipped fingers which expand into spaced points of the recesses 3| and 42. The top edge and inner surface of the bucket 35 is grooved at spaced points 44 to permit the escape of liquid from the interior of the bucket.

By the present invention, spinning buckets are constructed having great durability and light weight. These advantages accrue from the composite construction comprising base members fabricated from a high strength material, usually metallic, and an outer layer covering all exposed surfaces of the members constructed primarily from a polymeric product of fiuorinated ethylenic monomeric material. Buckets, so constructed have great resistance to chemical action, temperature, abrasion and impact. As further important advantages, the surface of the resinous layer is non-wettable by the liquids which are used for the regeneration of cellulose from viscose solutions, and the yarn-receiving surface within the bucket is non-adherent to the cakes principally because of, it is believed, the surface property which imparts to the surface its characteristic waxy feel and appearance. Because of the extraordinary toughness of the protective layer of the spinning buckets herein described, materials which comprise the body or base members of the buckets and bucket covers are protected from chipping, such as when the members are constructed from resinous, or resin-filled laminated materials.

Another advantage is that the spinning boxes may be constructed with an inner surface of less taper without sacrificing facility in doifing and, thus, the capacity of the box may be increased. The requirement for less taper is an advantage which becomes more obvious and beneficial as the depth of the spinning boxes are increased.

While preferred embodiments of the invention have been shown and described, it is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

l. A spinning bucket having an inner yarnreceiving surface against which a yarn is wound into a cake, the bucket comprising a body member of high-strength rigid material and a protective layer therewithin providing said yarnreceiving surfaces, said layer comprising a polymer selected from the group consisting of polytetrafiuoroethylene and polyvinylidene fluoride for imparting a waxy feel to said surface and rendering the surface non-adherent to the peripheral surface of a cake. f

2. A spinning bucket having an inner yarnreceiving surface against which a yarn is wound into a cake, the bucket comprising a metallic body member and a protective layer therewithin providing said yarn-receiving surface, said layer comprising a polymer selected from the group consisting of polytetrafiuoroethylene and polyvinylidene fluoride for imparting a, waxy feel to said surface and rendering the surface non-adherent to the peripheral surface of the cake.

3. A spinning bucket as defined in claim 2 wherein the protective layer extends over the exterior surfaces as well asthe exterior surfaces of the body member.

4. A spinning bucket and a cover therefor having yarn-receiving surfaces against which a yarn is wound into a cake, the bucket and the cover each comprising a metallic member and a protective layer thereover providing respective yarnreceiving surfaces, said layer of each member comprising a polymer selected from the group consisting of polytetrafiuoroethylene and polyvinylidene fluoride for imparting a waxy feel to said yarn-receiving surfaces and rendering such surfaces non-adherent to the exterior surfaces of the cake.

5. A spinning bucket having an inner yarnreceiving surface against which a yarn is wound into a cake, the bucket comprising a body member of high-strength rigid material and a protective layer therewithin providing said yarnreceiving surface, said layer comprising polytetrafluoroethylene for imparting a waxy feel to said surface and rendering the surface non-adherent to the exterior surface of a cake.

6. A spinning bucket as defined in claim 5 wherein the high-strength rigid material comprises aluminum.

7. A spinning bucket having an inner yarnreceiving surface against which a yarn is wound into a cake, the bucket comprising a body member of high-strength rigid material and a protective layer therewithin providing said yarnreceiving surface, said layer comprising polyvinylidene fluoride for imparting a waxy feel to said surface and rendering the surface nonadherent to the exterior surface of a cake.

8. A spinning bucket as defined in claim 7 wherein the high-strength rigid material comprises aluminum.

HUGH D. HALE-Y.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,492,426 Haley Dec. 27, 1949 FOREIGN PATENTS Number Country Date 422,122 Germany Nov. 24, 1925 "426,708 Great Britain (not accepted)

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