US 2208897 A
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y 23, 1940- s. M. DOCKERTY ET AL 2,208,897
WIRE COVERING DEVICE Filed Feb. 4, 1958 INVENTOR. $709k? /7 Dorks/QTY 7 W. W/LEY BY 5: a
Patented July 23,1940
UNITED STATES PATENT OFFICE WIRE COVERING DEVICE Application February 4, 1938, Serial No. 188,818
This invention relates to a device for gathering and twisting fibrous material and more particularly to a means and method for depositing a felted layer of fibrous insulating material on the surface of an electrical conductor.
Heretofore various means have been employed in applying fibrous insulating coverings to electrical conductors. Most commonly the fibres have been formed into threads, slivers and woven or felted tapes which have been braided or wrapped helically about the conductors. Some attempts have been made to form a seamless felted covering of fibres about a conductor but these attempts have been directed primarily toward mechanically compressing an interengaged mass of loose fibres about the wire where they are held with the aid of adhesives and impregnants.
While the braided coverings have excellent mechanical characteristics the amount of labor involved in spinning thread, winding it in bobbins and braiding it about the conductor renders the final cost of such a covering relatively high. Simpler coverings where thread, slivers and felted tapes are wound helically about a conductor are somewhat more economical but here again the preparation of the fibres amounts to a considerable portion of the cost of the covering. Furthermore, all helically wound coverings are inherently weak in fiexure tending to open up n along the joints between successive turns producing spots where there is little or no insulation covering the conductor. Felted coverings in which the various fibres are disposed in heterogeneous, interengaged relation have, to a considerable extent, the mechanical advantages in flexure of the braided coverings without the attendant expense of prefabricating the fibres. However, prior to this invention the majority of felted coverings were of rather loose construction, the individual fibres being held in place by adhesives or external wrappings almost as much as by interengagement of the fibres themselves.
The object of this invention is a device by which a mass of air borne fibres may be collected and spun into a twisted body.
A further object of this invention is to provide a means and method by which fibrous material may be applied to the surface of an electrical conductor or other core in the form of a thin, 5 tight, felted and twisted layer having in and of itself good mechanical and dielectrical properties.
This invention is disclosed particularly in conjunction with a device for forming fine filaments of glass such as is disclosed in the British patent to Triggs No. 428,720 but is equally operable with any fibrous material having good dielectric properties so long as the staple length is greater than the circumference of the conductor. These fibres are dispersed in a moving stream of air either by the process of their formation, as in the case of glass fibres, or by means of a suitable fibre separating and blowing mechanism such as is common in textile art. These air borne fibres are collected as a thin felted mass on a moving foraminous body. A small diameter, slightly tapered spindle is positioned closely adjacent the surface of the fibre collector and substantially at right angles to its direction of movement. This small diameter spindle is driven at high speed so that its peripheral speed appreciably 15 exceeds that of the fibre collector. This difference in speed may be positively established by driving both the spindle and the collector at definite speeds, or it may be brought about merely by driving the spindle, the collector being moved by the fibres as they are drawn therefrom.
In operation the air borne fibres are deposited as a tangled felted mass on the surface of the collector from which they are withdrawn and wrapped about the spindle as a coating thruout the major portion of its length. Since the peripheral speed of the spindle is somewhat greater than the surface speed of the collector a certain amount of drawing out and orientation of the fibres takes place between the spindle and the surface of the collector. This is particularly pronounced with respect to those fibres which are so deposited on the collector that they contact with both the collector and the spindle during the take up of the deposited web by the spindle. Thus a body of fibres is built up on the spindle in which a portion of the fibres are wrapped helically about the spindle while the remainder of the fibres extend in various directions interlaced and felted with the circumferentially disposed 40 fibres.
While the device and process here disclosed may be used to form a twisted roving it is primarily intended to apply insulating coverings to electrical conductors and to this endthe spindle is formed with a central bore of a size suitable for the conductor which is to be covered. Such a conductor is drawn thru the spindle from a supply drum to a driven drum on which the insulated conductor is wound. As the conductor passes from the spindle an operator withdraws some of the accumulated layer of fibres on the spindle over the end thereof and wraps them around the conductor. Subsequent movement of u the conductor tends to withdraw the fibres from the spindle and results in a partial orientation of the circumferentially wrapped fibres longitudinally of the spindle but, since the spindle is rotating rapidly with respect to the moving wire they appear in the final coating in a generally helical position, tightly wrapped and interlaced with the remainder of the fibres which are simultaneously drawn from the spindle. The tractive effort exerted on the fibrous mass adjacent the end of the spindle moves the mass as a whole along the surface of the spindle but continuous transfer of fibres from the collector to the spindle replenishes the spindle coating and a condition of equilibrium is attained for the particular rates of speed, rotation and draw then existing. While movement of the fibrous mass along the tapered spindle tends to loosen it, it has been found that this tendency is offset by the orientation of the fibres in the coating and the wrapping action of the newly applied fibres so that the fibrous coating remains firmly in contact with the surface of the spindle thruout its passage therealong. This orientation and wrapping continues between the tip of the spindle and the surface of the conductor and results in a spinning down and tight wrapping of the fibres into a felted, twisted coating on the conductor which is seamless, has mechanical strength in all directions and a permanent firm structure.
The drawing forming a part of this disclosure illustrates one mechanism embodying the invention of which:
Fig. 1 is a perspective view of the entire assembly;
Fig. 2 is an enlarged plan view of the spindle and collector showing the fibre transfer; and
Fig. 3 is a cross section of the wire and felted covering thereon.
In the illustrated device, molten glass flows in fine streams from the melting furnace H and is attenuated to, filaments of from .0015" to .0003 by jets of steam issuing at high speed from blowers l2. These fibres, which have a length of several inches or more are drawn down to the surface of a foraminous drum i3 by means of suction box l4 which is connected with a suitable vacuum pump by conduit l5. This collector drum i3 is supported in a horizontal position in a framework I6 and is rotated about its longitudinal axis by a variable speed power source such as motor I 7. Mounted on the same frame work I 6 with its surface uniformly spaced from drum I3 is a hollow tapered spindle 3. This spindle may be driven from the same or a separate power source #9 with a peripheral speed somewhat in excess of the peripheral speed of the drum I3. A
drum 20 containing the conductor 2! to be insulated may be mounted on frame 22 in alignment with the spindle while a second drum 23 mounted on frame 24 driven at suitable speed by motor 25 provides a means for drawing the conductor thru the spindle as well as a reeling device for its reception.
In operation glass fibres are formed and collected as a thin tangled mass on the surface of drum l3 from which they are drawn'and wound about spindle l8 in the manner described at length above and illustrated in enlarged detail in Fig. 2. As conductor 2| is drawn thru the spindle I8 the fibrous layer thereon is drawn off over its free end and spun down into a tight felted covering 26 on the surface of the conductor which is thereafter wound on the reel 23.
While adhesives may be applied to the conductor prior to its passage thru the spindle and the resulting covering may be impregnated and polished in the customary way if desired, such operations are unnecessary for the formation of a tight strong coating according to the present invention and have therefore been omitted from the disclosure.
It is to be understood that the structure described herein is merely by way of illustration and the invention is to be limited solely by the scope of the appended claims.
1. The process of applying fibrous insulating material to the surface of a conductor comprising the steps of forming a thin layer of interengaging fibres on a moving support, removing said layer of fibres from said support at a speed greater than that of the support, wrapping said layer of fibres about a conductor but out of contact therewith, a portion of said fibres being disposed substantially circumferentially of said conductor, drafting said layer of fibres longitudinally of said conductor to arrange a portion of said fibres longitudinally thereof, and rotating said mass of fibres relative to said conductor and spinning said fibres down into a tight felted mass on the surface of said conductor.
2. The process of applying fibrous insulating material to the surface of a conductor comprising the steps of collecting a thin felted layer of insulating fibres on a moving support, drafting said layer of fibres to partially orient said fibres, wrapping said drafted layer of fibres circumferentially about a. conductor but out of contact therewith to form a conical body of fibrous insulation, drafting said body of insulation longitudinally of said conductor to partially orient the fibres therewith and rotating said body with respect to said conductor to spin said fibres down into a tight felted layer thereon.
3. The process of forming a fibrous insulating coating for a conductor forming a thin felted layer of fibres, wrapping said layer about a conductor, but out of contact therewith, to form a conical body of insulation, drafting said body longitudinally of said conductor while simultaneously reducing its diameter, and spinning said body down into contact with said conductor to form a tight felted covering thereon.
4. In combination, a source of air borne fibres, means for collecting said fibres as a felted sheet, means for wrapping said sheet about a conductor and means for drafting said wrapped sheet longitudinally of said condctor and spinning it into contact therewith.
5. In combination, a source of air borne fibres, a perforate conveyor, means for collecting said comprising the steps of fibres on said conveyor, a spindle positioned adjacent said conveyor and having its axis substantially at right angles to the direction of movement of said conveyor, and means for passing a conductor through said spindle.
6. In combination, a source of air borne fibres, a perforate conveyor, means for drawing a body of air thru said conveyor, a tapered spindle positioned adjacent said conveyor and having its surface uniformly spaced therefrom, and means for passing a conductor thru said spindle.
7. In combination, a source of air borne fibres, means for collecting said fibres as a felted sheet and conical means for removing said sheet from said collecting means and wrapping it about a conductor, said last named means being disposed substantially at right angles to the direction of movement of said sheet and uniformly spaced from said collecting means.
8. In combination, a source of air borne fibres, a perforate conveyor, means for collecting said fibres on said conveyor and means for'withdrawing the collected fibres from said conveyor as a sheet, said last named means being driven at a higher peripheral speed than said conveyor.
9. In combination, a source of air borne fibres, a collector adjacent thereto comprising a perforate drum and means for drawing air therethrLr, means for driving said drum, 9. spindle positioned adjacent said drum with its surface parallel therewith, and means for driving said spindle at a higher peripheral speed than said drum.
10. In combination, a source of air borne fibres, a collector adjacent thereto comprising a perforate drum and means for drawing air therethru, means for driving said drum, a spindle positioned adjacent said drum with its surface parallel therewith, and means for driving said spindle at a higher peripheral speed than said drum and means for passing a conductor thru the center 10 of said spindle.
STUART M. DOCKERTY. OTIS W. WILEY.