METHOD AND APPARATUS FOR WINDING FLAT COILS OF FILAMENTARY MATERIALS SUCH AS OPTICAL FIBERS

Abstract: A winding assembly has at least two flat coils wound from a single filament and arranged with the coil major side surfaces facing one another, the filament winding in adjacent coils being oppositely directed. Three spaced apart guide plates (26), (28), (30) are axially mounted on a shaft (46) defining first and second winding spaces (32), (34). A first winding arm (40) rotates about the shaft to build up a flat coil in the first winding space and second winding arm (42) rotates about the shaft in the opposite direction to lay down a further flat coil in the second winding space.

Description: METHOD AND APPARATUS FOR WINDING FLAT COILS OF FILAMENTARY MATERIALS SUCH AS . ' OPTICAL FIBERS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to the winding of filamentary materials into a spool, and, more particularly, to a method and apparatus for the winding of filamentary materials into a tandem stack of flat coils. 2. Description of Related Art There are many situations in which it is necessary Jig . unwind from a prefabricated spool, an extended length of either a metal wire or an optical fiber at a rapid rate and in such a manner as not to crimp, distort or over-stress the filamentary material. For example, certain present-day missiles include a stored spool of an optical fiber which, upon launching of the missile, is paid out and remains interconnected with the launching station. The target scene information and the missile guidance commands are transmitted via the fiber data link for the entire or portion of the missile travel. Conven¬ tional cylindrical layered windings such as typically encounteredT ^ i the winding of transformers or in the textile industry, for example, are not fully satisfactory for optical fibers and are accompanied with several difficulties in use. For example, on rapid payout of an optical fiber from a conventional spool which is cylindrically wound, there is a high lateral friction drag which produces heat and possible damage to the fiber resulting in the fiber data link failure or undesirable optical signal modulation. Also, during shelf storage or temperature cycling, the winding pattern may collapse or slump which can prevent a smooth payout operation. Still further, there is an inherent requirement in cylindrical layered winding of fiber crossover areas between the layers, and this produces what is referred to as "micro- bending" resulting in added optical signal loss. In an attempt to overcome the deficiencies of a cylindrical lay'ered winding, coils have been made up by winding a tandem stack of flat coils each consisting of a fixed length of fiber wound into a spiral. Although this approach overcomes the noted difficulties with cylindrical layered winding, until now a practical and high-speed process of making flat coil windings from a single continuous fiber has not been achieved. SUMMARY OF THE INVENTION It is a primary object and aim of the present invention to provide method and apparatus for simul¬ taneously making a pair of flat coils from a single optical fiber. A two-coil winding apparatus is constructed of three closely spaced, parallel guide plates mounted onto a shaft defining the first and second winding spaces, each of a width enabling only a single fiber to be wound therein. A length of fiber is pulled off a supply spool equal to one coil length and it is temporarily stored on a takeup spool with the inner end of the one-coil fiber length being located in an axially located opening in the central guide plate. Two fiber winding devices respectively wind one flat coil in the first winding space from the temporarily stored fiber length, and another flat coil in the second winding space taken from fiber on the supply spool. The two flat coils are simultaneously wound and in opposite directions, and are connected at the innermost turn. After the flat coils are wound, the guide plates are removed and a light coat of adhesive is applied to the coils to maintain geometric and dimensional integrity. Alternatively, the adhesive may be applied through access slots or cut-outs on the guide plates directly to the coils. The completed pair of flat coils are slid to one end of the shaft and a further pair of coils may now be wound as described, and so forth until the required number of coils are obtained. DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of apparatus for winding flat coils in accordance with this invention. FIGS. 2A and 2B depict a side elevational, sec¬ tional view of the flat coil winding apparatus of FIG. 1. FIG. 3 is a side elevational view of a cylindri- cally layered coil showing micro-bending. FIG. 4 is a side elevational view of a split guide plate. DESCRIPTION OF A PREFERRED EMBODIMENT There are a number of situations in which an optical fiber or a metal wire must be paid out very rapidly from a spool upon which it is wound. For example, in certain missiles an optical fiber interconnects the missile with the launch terminal, which may be aboard a ship, an aircraft or ground based. When the missile is fired, a continuous optical signal data link is provided by the optical fiber which is allowed to pay out from a spool in the missile. In this manner, target tracking and guidance computation can be accomplished at the terminal and command instructions can be given over the ■ A optical fiber thereby obviating the necessity for includ¬ ing all the complex computing and tracking equipment on board the missile. Although the described method of winding and appa- ratus for practicing the method are useful for winding all -kinds of filamentary materials, they are especially advantageous when applied to winding optical fibers and will be described particularly in that connection here. With reference now to FIG. 3 of the drawings there is shown a conventional cylindrical layered coil 10 which is seen to include', for descriptive purposes only, two layers 12 and 14 of optical fibers, the layer 12 being helically wound to form a cylindrical layer on the outer surface of a cylindrical bobbin 16, for example, and the second layer 14 being similarly wound over the first layer. In actual practice, of course, and depending upon the total length of the fiber, there may be many such layers. ' Assuming that a fiber were to be paid out from the right end of the bobbin, as shown in FIG. 1, each loop from the outer-most layer,. as the peel point progresses to the left, would be exposed to contacting part or all of the underlying winding layer as it moves therepast. This frictional contact produces a drag upon the fiber which can damage or deform the fiber, thus adversely affecting its optical signal transmission characteristics. A urther difficulty with cylindrical layered winding, sometimes referred to as "micro-bending", is the bending of the fiber as a result of overlaying a foreward- helix outer layer onto a backward-helix underlying layer. These micro-bendings can accumulate significant signal loss which degrades signal transmission along the fiber. The micro-bending of the fiber is enumerated as 17, and the bends for adjacent loops are shown immediately adjacent to each other as, in practice, this is done to achieve maximum density winding. The cylindrical layered windings also exhibit a tendency to collapse or slump during extended shelf storage or in circumstances where there are substantial temperature changes. This is undesirable and can cause the fibers of adjacent layers to be intermixed with one another to the extent that payout may be interrupted. To avoid the disadvantages of cylindrical layered coils, it is fundamental to the present invention to wind the optical fiber in a flat-coil configuration, or, more precisely, a series of flat coils wound from a single continuous fiber. A flat coil consists essentially of winding each fiber loop on top of a previous loop, forming a disk-like coil that is one fiber diameter thick. In the past, such a flat coil has been made by hand laying the fiber on a horizontal surface. However, when a plurality of flat coils are required there is no effi¬ cient method and apparatus to achieve the flat-coil winding with acceptable speed. For the ensuing description of the method and apparatus of the present invention, reference is now made to FIGS. 1, 2A and 2B. The first step constitutes removing a length of optical fiber 18 from a fiber supply spool 20 that is equal to the amount of fiber to form one flat coil and storing this amount on a temporary takeup spool 22. Without reference to details at this time, the coil forming apparatus 24 includes three guide plates 26, 28 and 30, located on a common shaft and separated so as to form two winding spaces 32 and 34, each slightly wider than the diameter of the optical fiber. The end point 36 of the temporarily stored fiber is positioned in an opening 38 of the central guide plate 28. Two flat coils are wound simultaneously. One is taken from the temporary storage spool 22 and the second is wound directly off the fiber supply spool 20. More particularly, two fiber winding devices 40 and 42 rotate in opposite directions to form a first flat coil in the space between guide plates 26 and 28 and a second flat coil between guide plates 28 and 30, respectively. By winding the coils in opposite directions the inner- connecting fiber located in the center guide opening 38 has not been subjected to a sharp bend. Upon completion of the fabrication of the two adjacent flat coils, the guide plates are removed, the coils sprayed or otherwise provided with a light coat of adhesive and the two coils are then moved or slid to the end of the winding spool where they are stacked in tandem in a side-by-side rela¬ tion to previously made coils 44. With particular reference to FIGS. 1 and 2B, the winding framework defining the flat coils consists of three generally circular plates 26, 28 and 30 which are arranged parallel to one another and are secured together in a unitary relationship on a hollow cylindrical shaft 46. The plates are each constructed of two semicircular parts which are fitted together and secured with pins 54 located within openings in the guide plates. The three guide plates are so spaced apart along the shaft as to provide a winding space 32 between guide plates 26 and 28 and a further winding space 34 between plates 28 and 30. Each winding space 32 or 34 is of a width slightly exceeding the diameter of the fiber 18. The edge portions of plates 26 and 30 facing toward one another are beveled to provide a smooth surface for guiding the fiber during winding as will be described. The fiber winding devices 40 and 42 are identical to each other and, therefore, only the device 40 will be described in detail. The device 40 is an elongated rotary member of total length slightly greater than the radius of a guide plate (FIG. 1) . A ball bearing 58 in one end of the member 40 is fitted onto the shaft 46 for rotation about the shaft just outwardly of guide plate 26. The upper end portion of the device has a first grooved pulley 62 mounted on the device outwardly facing side and a second grooved pulley 64 mounted on the device side facing the guide plates. Drive motors (not shown) are operatively connected to rotate the device 40 in a pre¬ determined direction, e.g., clockwise as depicted in FIG. 1. The device 42 is identically constructed to device 40 except that it will be rotated oppositely (e.g., counterclockwise as shown in FIG. 1). As a first step in using the described apparatus, a length of optical fiber 18 is pulled off the supply spool 20 equal to that amount necessary to form one flat coil and temprarily wound onto the takeup spool 22 with the fiber also being placed around the grooved pulleys 62 and 64 of both fiber winding devices 40 and 42. The point on the fiber 18 defining the inner end point 36 of the one flat coil amount that has been temporarily stored on the takeup spool is then located through opening 38 in the central guide plate 28. All three guide plates 26, 28 and 30 are now mounted onto shaft 46 (FIG. 2B) and located in place by pins 54. Next, the winding devices 40, 42 are rotated in opposite directions a sufficient number of turns until two flat coils are completed: one in the space 32 between guide plates 26 and 28, and a second in space 34 between plates 28 and 30. The pins 54 are withdrawn, the two flat coils covered (e.g., by spraying) with a light coat of adhesive, and the coils are slid along shaft 46 to a storage position 44 (FIG. 2A) . The process is repeated until the required number of flat coils are obtained ' . There is provided in accordance with this invention a method and apparatus for forming a coil assembly from a single continuous optical fiber consisting of a tandem stack of flat coils in which the fiber portion inter- connecting adjacent flat coils is not subjected to any stretching or bending. The fiber of such a coil assembly upon payout is only subjected to adhesive drag between the fiber and the winding immediately below. The flat coils do not experience undesirable stresses or friction and the fiber is not subject to micro-bending. Although other adhesives may. be found satisfactory for maintaining a fiber coil dimensioned integrity while forming a multiple coil assembly, excellent results have been obtained with a blend of silicon adhesives. In addition to applying the adhesive to the coils after removal of the plates one at a time, slots or cutouts 70 can be provided in each plate 26 and 30 through which the adhesive may be applied prior to the guide plate removal. Although several somewhat preferred embodiments have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined Jay that of the appended claims.

Claims: CLAIMS What is Claimed is: 1. Method of winding a coil assembly from a filament supply including at least two flat coils, com¬ prising the steps of: removing a length of filament from the supply sufficient to wind one flat coil; winding the removed length of filament in a first direction to form a first flat coil; and winding a second flat coil of filament taken from the supply and wound in the opposite direction to that of the first flat coil. 2. Method of winding as in claim 1, in which the first and second coils are wound simultaneously. 3. Method as in claim 1, in which the length of filament removed from the supply stored on a takeup spool prior to being wound into the first coil. 4. A method of winding two flat coils from a single continuous filament supply, comprising the steps of: locating three platelike guides in a mutually facing spaced apart relation to form first and second winding spaces, the central guide having an opening therei ; passing the end of the filament through the central guide opening; pulling a length of filament off the supply sufficient to wind one flat coil, passing it through the central guide opening and temporarily storing the length of filament on a takeup spool; winding the takeup spool filament in one direction in a first winding space to form a first coil; simultaneously winding filament from the supply in the second winding space in the opposite direction to form a second flat coil; and removing the platelike guides. 5. A method as in claim 4, including the further step of applying adhesive to the first and second flat coils. 6. A method as in claim 4, in which the filament is an optical fiber and the flat coils each have a width equal to the filament diameter. 7. A flat coil assembly, comprising: at least two flat coils formed from a single continuous filament arranged with coil major surfaces facing one another and the direction of winding being different for the two coils. 8. A flat coil assembly as in claim 7, in which a quantity of adhesive is applied to each coil unitarily relating the turns of each coil to one another. 9. Apparatus for simultaneously winding a pair of flat coils from a single filament comprising: a shaft; three platelike means each having a central opening received on the shaft with the two outer plate¬ like means being spaced from the central platelike means to define first and second winding spaces, the central platelike means having a second opening closely adjacent the shaft; 1 2 first filament winding means for winding a length of the filament into the first winding space; and second filament winding means for winding a further filament length into the second winding space, said first and second filament winding means forming flat. coils wound in opposite directions. 10. ^ .Apparatus as in claim 9, in which the plate¬ like means are formed in separable parts. 11. Apparatus as in claim 10, in which the separable parts of each platelike means are releasably secured together by a removable pin. 12. Apparatus as in claim 9, in which the winding means each include an elongated member having one end journaled to the shaft for rotating thereabout. 13. Apparatus as in claim 9, in which the winding ■ spaces each have a width substantially equal to the fila¬ ment diameter.

Inventors: HSU HUI-PIN, HU WILLIAM C, HSU, HUI-PIN, HU, WILLIAM, C.
Applicants: HUGHES AIRCRAFT CO, HUGHES AIRCRAFT COMPANY
Application year: 1989
Main classification: B65H55
IPC codes: B65H55, G02B6