US 2800682 A
Description (OCR text may contain errors)
July 30, 1957 W. P. DOOLEY PIEZOELECTRIC TUBE FOR-APPLYING LIQUID T0 RUNNING STRANDS Filed Feb. 23, 19.54
PIEZOELECTRIC TUBE FOR APPLYING LIQUID T RUNNING STRANDS William P. Dooley, South'Charleston, W. Va., assignor to American Viscose Corporation, Philadelphia, Fa a corporation of Delaware Application February 23, 1954, Serial No. 411,727
6 Claims. (Cl. 18-8) The invention relates to improvements in liquid treatments for running strands and particularly to the afterspinning treatments of strands comprising artificial fibers derived from solutions of fiber-forming materials.
While the invention may 'be practiced with advantage in connection with the manufacture of artificial fibers from solutionsof fiber-forming materials of various types, the description which follows hereinafter is related to, because of outstanding utility of the invention in, the manufacturing of large continuous bundles of filaments, e. g., the tows which comprise regenerated cellulose filaments derived from viscose by the wet-spinning method which may be subsequently reduced to staple fiber.
In accordance with the conventionalpractice, the fibers of such a tow are derived by extruding viscose through one or more spinnerets into an acid coagulating and regenerating bath and continuously withdrawing the fibers formed by the coagulation actionof the bath .away from the spinneret face and to the exterior of the bath for the various after-treatment.
Under usual manufacturing conditions, the filaments are withdrawn from the spinning bath as material comprising partially regenerated cellulose. At this stage, each filament comprises a still-fluid core and dependence is placed upon theacid carried from the baththrough the skin initially set-up on the filaments within the bath to effect complete regeneration of the cellulose. The rate of diffusion of the adhering acid in the material of the fiber, and the uniformity of such difiusion, controls the rate at which the regenerationof the cellulose is .continued. This process of diffusion is characteristic also of the later-occun'ng liquid treatments applied to the filamentary material. Other factors relating to the speed and efiiciency of a liquid treatment are the temperature of the liquid for effecting the treatment,- the movement of such liquid relative to the surface of the filaments and the concentration of dissolved materials of such liquids.
It is an object of this invention to utilize ultrasonic energy in accomplishing liquid treatments of running strands, such as areobtained from filament-forming materials, with greater efiiciency than heretofore obtained.
it is also an object to utilize an ultrasonic energy applicator as a portion :of the container -in-whi-ch a liquid treatment'of a running yarn is effected.
Still another object is to focus or concentrate the ultrasonic energy derived from the aforementioned applicator or transducer along a portion of the path of a runing strand.
Another object is to provide a simple apparatus which is inexpensive to maintain and easy to operate.
A further object is to obtain more efficient use of the ingredients constituting a treating liquid.
Other objects, features, and advantages will become apparent from the following description of the invention and the-drawings relating'thereto in which:
Fig. 1 is a diagrammatic view of one embodiment of the invention;
nited States Patent F c Patented July 30, 1957 Fig. 2 is a diagrammatic view of another embodiment;
Fig. 3 is a diagrammatic view of a third embodiment of the invention; 1
Fig. 4 is a view showing in cross section portions of a transducer and an adjacent wall of a liquid-holding member connected therewith, and diagrammatic illustration of th electrical circuit for connecting the transducer with an ultrasonic frequency alternating-current generator; and
Fig. 5 is a view showing a modified tubular transducer in cross section and the connection thereof with an alternating-current generator.
Briefly stated, the invention resides in passing a running yarn or tow while submerged in liquid through a tubular member capable of transmitting ultrasonic vi brational energy through the liquid disposed within the member, into the strand. In a preferred embodiment, the member or transducer constitutes a portion of a liquid-conducting system whereby the liquid may be passed therethrough in concurrent or countercurrent relation to the direction of movement of the strand. The purpose of such a system is to accelerate the rate of, and to make more efiicient, the liquid treatment of the yarn or tow whereby the length of treatment zones and the amount or concentration of the treatment solution needed to carry out the processing of the strand may be reduced.
Shown diagrammatically in Fig. l is one scheme for applying wet treatment to running yarn in accordance with the present invention. A yarn 4 moves in the direction of the arrows over a guide 5, between feed rolls 6, and over a guide 7 through a liquid-receiving member 8 comprising an interior overflow wall 8a. A tubular transducer 10 comprising a piezoelectric material extends from interiorly of a feed compartment 11 in spaced relation with the liquid receiver 8 into the interior region of the receiver. A guide 14 is positioned with respect to the guide 7 whereby the yarn 4 is aligned to pass longitudinally of the transducer 10 generally along its longitudinal axis. The transducer has a wall that 'is circulm' or annular in cross section whereby that portion of the ultrasonic vibrational energy generated thereby that is directed radially inwardly from the wall is concentrated or focused along the longitudinal axis of the transducer. The strand passes from a compartment .11 around, and upwardly away from, the guide 14. The strand may thereafter 'be advanced horizontally after passing around a guide 15 by a pair of squeeze roll-s 16 which may function to express liquid from the strand as well as to advance the strand.
An ultrasonic generator 18 is connected with the transducer tube ltlby electrical-conductors 19 in a manner hereinafter explained to induce vibration of the transducer..
The vibrations produced in piezoelectric material of the transducers are, in turn, imparted to the liquid passing therethrough and the energy thereof is concentrated as a result of the concavity of the innersurface of the transducer along the axial path followed by the yarn. The transducer is a molded member comprising a piezoelectric material such as a barium titanate ceramic, manufactured and formed into transducers by the Clevite Corporation through its subsidiary, the Brush Electronics Co.
Fig. 2 illustrates another embodiment of the invention involving the use of a tubular transducer in the wet treatment of a strand. According to the diagrammatic illustration of Fig. 2, yarn 21 is spun by extruding a filament-forming liquid from a spinneret 22 disposed within a spinning compartment 23. A liquid coagulant is .fed into the chamber 23 through a duct 24. The spinneret, during normal operation, is submerged in coagulant which is fed into the compartment at such a rate as to maintain the compartment and the transducer filled with liquid. A filament-forming material is supplied to the spinneret through a tube 25. As shown, the tube extends through arclosure or removable wall portion 26 of the compartment in fixed sealed relation with the closure. Extending in coaxial alignment with the face of thespinneret is a tubular transducer 27 connected with'a portion-of the chamber 23 defining an outlet port thereof for coagulant and the strand derived from the spinneret. The coagulant passes from the spinning chamber through the transducer 27 to a drain compartment 28 over 'a liquid and strand separating device 29 comprising a series of parallel elements 30. The used coagulant passes from the compart ment 28 through a drain duct 32. The strand may be advanced through the apparatus just described by a pair of thread-storage thread-advancing rolls 34. The freely rotatable roll 35 holds the strand in light contact with the stripping device 'and allows the strand to be drawn upwardly therefrom onto the thread-advancing rolls 34.
The spinneret 22 is submerged during normal operation in the coagulant fed into the spinning compartment at such a rate as to maintain the spinning compartment and the transducer filled with liquid. The inner diameter of the transducer and the feed rate may be altered as desired to maintain this condition and also to obtain a desired ratio of the rate of flow of the coagulant with the linear speed of the yarn. The transducer 27 extends interiorly of the compartment 28 and is mounted resiliently in a sidewall thereof by means such as a resilient grommet 38. At the other end it is connected with the spinning compartment by a resilient coupling 39. The transducer 27 is electrically connected to the high frequency current generator 18 in a manner similar to that indicated in the discussion of Fig. 1. I
Fig. 3 illustrates the use of a tubular transducer 45 within a simple liquid-treating tank 46 into which liquid is fed through an inlet duct 48 and discharged through an endwall at 49. The transducer is supported below the surface of the liquid within the tank 46. The strand 51 advancing through the tank is aligned along the longitudinal axis of the transducer by guides, such as rollers 52 and 53, whereby the electrical energy transmitted to the transducer from the generator 18 may be converted into vibrational energy and directed in a radial direction toward the strand 51 as it passes through the transducer. When the transducer is submerged as shown in Fig. 3, it is necessary to provide electrical insulation along all submerged portions of the conductors between the generator 18 and the transducer, and also along exposed submerged surfaces of the electrodes of the transducer that might permit a short circuit to develop within an electrolyte-type bath. Thus insulation 55 may be provided as shown.
The essence of the present invention is to promote the action of a treating liquid on the strand material disposed therein within the ultrasonic transducer. The vibrational energy is thus concentrated along the path of the strand whereby it disturbs the normal concentric laminated film relation in the liquid surrounding the strand and greatly increases the contact of the active ingredients of the liquid with the material of the strand. The vibrational energy, furthermore, greatly increases the rate of diffusion of the ingredients carried by the liquid toward the center of the filaments and the discharge of reaction products or impurities formed within the filaments from interiorly thereof into the treatment liquid.
The transducers 10, 27, or 45 may take, for example, the general form of the transducers 60 or 61 of Figs. 4 and 5, respectively. In Fig. 4, the transducer comprises an inner tube 64 of shaped ceramic material having the proper dielectric properties which render it desirable for generation of ultrasonic energy, and an outer metallic sheath, plating, or coating 65 which functions as an electrode in substantially continuous contact .with the surface of the piezoelectric or electro-mechanically sensitive substance constituting the tube 64. The sheath 65 extends substantially over the entire length and circumference of the tube 64 or to any extent to which the length of the transducer is to be utilized for the development of ultrasonic energy. If desired, the sheath 65 may extend around only a portion of the length of the tube 64. The sheath may be fabricated from any efiicient electricallyconducting material which will be serviceable within the chemical environment in which the transducer will be operated. Platings of various metals may be applied to the inner surface or to the outer surface, or to both surfaces, of the ceramic material of the tube by well known techniques. As shown in Fig. 4, the transducer is not provided with an inner electrode since such a transducer is intended to be operated when completely or substantially full of a liquid of aqueous character, or other electrically-conductive liquid.
The power output circuit of the high frequency generator 18 is established by grounding a wall 67 of a metallic receptacle, such as the receiver 8 or the feed compartment 11 of Fig. 1, whereupon the aqueous liquid in contact with the inner side of this Wall functions as a conductor between the wall and the interior surface of the tube 64. The ceramic material is thereby provided with conducting media of opposite polarity along its interior and outer surfaces. Lines 68 and 69 represent the power-supplying circuit for the generator 18. Line 71 represents one side of the output circuit of the generator which connects with the outer metallic coating 65 of the transducer. The other side of the output circuit of the generator is grounded. The transducer 60 is attached to the wall 67 by a support within a grommet 72 which fits the periphery of an aperture through the wall. The grommet comprises a resilient material such as a vulcanizate of elastomeric material so as to permit vibrational movement of the transducer within the grommet relative to the wall.
In Fig. 5 is illustrated a modified transducer which may be disposed in contact with liquid in which the ceramic material for the transducer is chemically unstable. Accordingly, the transducer is provided with an inner electrode 74 as well as an outer electrode 75, both electrodes being similar to the electrically conductive sheath or coating 65 of the transducer 64 (see Fig. 4). The electrodes, for greater efliciency of the transducer, are preferably directly in contact with the ceramic material 73, thus requiring any protective coating for the ceramic material to be disposed exteriorly of the electrodes rather than between either of the electrodes and the adjacent ceramic material. Accordingly, the transducer61 comprises a protective coating 76 which extends over all exterior surfaces of the electrodes and the portions of the tube 73 of ceramic material not covered by the electrodes. When the transducer is to be submerged within a bath of electrolyte, the conductors connecting the generator and the transducer are covered with an electrically insulating material as hereinbefore described with respect to Fig. 3.
The coating may comprise any well known organic plastic resins, e. g., compositions comprising polymers or copolymers of vinyl chloride, vinylidine chloride, styrene, acrylonitrile, tetrafluoro and tn'fluoro ethylenic monomers, ethylene, and/or silicone resins. Ultrasonic vibrational energy of suflicient intensity is capable of disintegrating any of such resinous materials. However, the transducers employed in the present invention are operated at energy dissipation rates which are well below that required for disintegrating the resinous material constituting the partly manufactured strands to be passed therethrough. Thus it is safe to use a protective coating comprising a resinous composition such as indicated above, particularly since the vibrational energy intensity, is much less along the inner surfaces of the transducer than it is along the longitudinal axis thereof.
The electrodes 74 and 75 are connected with opposite sides of the output circuit of the generator 18. A hole packed with a suitable insulating resin provides access of the connector 77 with the inner electrode 74. The transducer 61 is supportedwit-hin the aperture of the wall 78 by a resilientgrommet 79 in the same manner as the transducer 60 of Fig. -4.
A metallic coating constituting an electrode of any one of. the transducers herein described is preferably a material such as silver which has been plated onto a desired surface of the ceramic material; The plating is preferably of minimum thickness as will allow eflicient electrical conduction to all parts of the surface of the ceramic material which is to be subject to the changing polarity provided by the high frequency alternating current obtained from the generator 18. In instances Wherein relatively low power output is desired, it may be feasible to provide the electrodes of the transducer as a coating of foil adhered to the ceramic material by an efiicient adhesive material such as one of the thermosetting organic resins. However, at relatively high power output, a foil of this type may tend to shake loose from the ceramic material. For this reason plating of the metallic material forming the electrodes directly onto the ceramic material is preferred.
The manner in which the output circuit is connected with the transducers in the various embodiments herein described, is such as to generate the energy in a radial direction with respect to the longitudinal axis of the transducers. Thus, that energy which is directed inwardly of the transducer is concentrated substantially along the axis of the transducer, and it is along this axis that the material passing therethrough should be supported.
In accordance with the present state of development of the molded ultrasonic transducers, a preferred material used in fabrication thereof is polycrystalline barium titanate. This material has the electro-mechanical property of expanding in the direction of polarization when the signal voltage applied to the material is of one polarity, and contracting at reversal of the signal voltage. The material is contracted in a direction transversely of the field of polarization when the material is expanded in the direction of the field. The limits have not been definitely established as to what current frequencies to which the material is responsive. It is known that ultrasonic energy is readily derived when employing frequencies in the range of several thousand to more than a billion cycles per second. High frequency generators are readily available for production of power in frequencies of this range and may be readily used with the piezoelectric transducers described herein in the practice of the present invention. In accordance with the findings of the laboratories of the Brush Electronics Company and others, the characteristics of the barium titanate ceramic may be modified by mixing of preponderate portions of the barium titanate with relatively small amounts of other related compounds, e. g., other titanates. For example, a primarily barium titanate ceramic containing about 4% of lead titanate will render the ceramic more electro-mechanically dependable at lower temperatures than a ceramic entirely constituted of barium titanate. Inclusion of around 5% of calcium titanate with barium titanate renders the resulting ceramic able to withstand higher voltages wihout depolarization, than the wholly barium titanate ceramic.
In the present invention, the transducers take on the dual function of applying ultrasonic energy to a yarn in a highly specialized manner, and serve as a part of a conduit system by which liquids may be applied to a yarn while having a desired movement relative to the movement of the yarn. The primary advantages derived from incorporating ultrasonic apparatus of this nature into yarn treating processes are, to greatly accelerate the rate at which liquid treatments may be accomplished, and to obtain more efficient use of the ingredients carried 6 in such liquids. Ancillary advantages are substantial reduction of the magnitude of the apparatus in factory space required for the housing thereof, and decreased labor cost.
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.
1. Apparatus for applying a liquid treatment to a running strand comprising a tubular member of piezoelectric material, means for guiding the strand through the member in spaced relation within the interior surface thereof, means for maintaining the member substantially full of the liquid for treating the strand, and electrical circuit means for applying a current of ultrasonic frequency to the member, the inside surface and the outside surface of the member being electrically conductive but electrically separated, said surfaces being connected to opposing terminals of said circuit.
2. Apparatus as defined in claim 1 wherein the treat:
ing liquid is electrically conductive and constitutes a portion of said circuit which connects with the inner surface of the member.
3. Apparatus for applying a liquid treatment to a running strand comprising a tubular member of piezoelectric material having a wall of arcuate cross section symmetrical with respect to a longitudinal axis of the member, means for guiding the strand generally along said axis, means for maintaining the member substantially full of the liquid for treating the strand, and means for applying a current of ultrasonic frequency to the member, the inside surface and the outside surface of the member being electrically conductive but electrically separated, said surfaces being connected to opposed terminals of a circuit for said current.
4. Apparatus as defined in claim 3 wherein said means for maintaining the liquid in the member comprises a liquid-supplying means surrounding one end of the member, and a liquid-receiving chamber surrounding the other end thereof having overflow means disposed at a level generally above the region within the member traversed by the liquid.
5. Apparatus for applying a liquid treatment to a running strand comprising a tubular member of piezoelectric material having a wall of circular cross section concentric with respect to a longitudinal axis of the member, means for guiding the strand generally along said axis, means for maintaining the member full of the liquid, and means for applying a current of ultrasonic frequency to the member comprising a metallic coating extending sub stantially over the interior surface, and another metallic coating extending over the exterior surface of the member, the exterior coating being electrically separated from the interior coating by the piezoelectric material, said coatings constituting opposed terminals of the circuit, said current acting on the circularly disposed piezoelectric material to generate and discharge ultrasonic energy to- Ward the axis of the member.
6. Apparatus for spinning artificial yarn comprising a spinneret, a spinning chamber for housing said spinneret and supporting it in a desired position, duct means for supplying the filament-forming material to the spinneret extending through a wall of the chamber, conduit means for supplying a liquid coagulant to the chamber, an opening in said chamber in spaced opposed relation with the face of the spinneret, a conduit connected with the chamher to place said opening in alignment with the interior of the conduit, the conduit extending away from the chamber in a direction generally perpendicular with respect to the face of the spinneret and terminating in a liquid receiver, guide means for aligning the yarn generally along the axis of the conduit as it proceeds therethrough and away from the spinneret, said conduit com prising a piezoelectric material, current-conducting means for substantially covering the outer surface of the conduit, current-conducting means in contact with'the liquid coagulant which enters and traverses the conduit, said currcnt-conducting means constituting portions of an alternating current-supplying circuit, means for applying a current of ultrasonic frequency to said circuit, and coagulant supply means connected with saidcoagulant supply duct for maintaining'the conduit full of liquid.
1 References Cited in th e file of this patent UNITED STATES PATENTS Schrey Sept. 26, 1939 Peterson Oct. 11, 1949 Sisson May 30, 1950 4 FOREIGN PATENTS Great Britain Apr. 17, 1947 Belgium Apr. 14, 1951 Switzerland Feb. 16, 1952