US3833182A

US3833182A - Integral open mesh spool

Info

Publication number: US3833182A
Application number: US00209182A
Authority: US
Inventors: A Wilcox; R Mees
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-12-17
Filing date: 1971-12-17
Publication date: 1974-09-03
Anticipated expiration: 1991-09-03

Abstract

An integral, open mesh, wound spool of generally cylindrical form includes a body section of a crossed strip of material, forming plurality of open diamonds, and a pair of spaced apart substantially solid end portions. The diamonds are in rows, circumferentially and rows longitudinally of the spool, with each of the circumferential rows having a predetermined odd number of diamonds and with the number of diamonds in each circumferential row and the number of diamonds in each longitudinal row having only unity as a common factor.

Description

United States Patent [191 Wilcox et al.

[ INTEGRAL OPEN MESH SPOOL [75] Inventors: Albert F. Wilcox, Yoder; Robert D.

Mees, Fort Wayne, both of Ind.

[73] Assignee: General Electric Company,

lndianapolis, lnd.

[22] Filed: Dec. 17, 1971 [21] Appl. No.: 209,182

[52] US. Cl 242/l18.1, 242/1l8.32, 336/205 [51] Int. Cl ..-B65h 75/20, B65h 75/10 [58] Field of Search 242/ll8.2, 118.1, 118.11, 242/ll8.32,118.31,118.3,118,118.4,

[56] References Cited UNITED STATES PATENTS 1,404,634 1/1922 Morton 242/1 18.1 2,336,086 12/1943 Goldman 242/1 18.32 2,888,258 5/1959 l-loffstrom 267/181 Sept. 3, 1974 Whipple 336/205 X FOREIGN PATENTS OR APPLICATIONS 1,136,984 1 1957 France 242/1l8.32

' Primary'ExaminerGe0rge F. Mautz [5 7] ABSTRACT An integral, open mesh, wound spool of generally cylindrical form includes a body section of a crossed strip of material, forming plurality of open diamonds, and a pair of spaced apart substantially solid end portions. The diamonds are in rows, circumferentially and rows longitudinally of the spool, with each of the circumferential rows having a predetermined odd number of diamonds and with the number of diamonds in each circumferential row and the number of diamonds in each longitudinal row having only unity as a common factor.

13 Claims, 6 Drawing Figures 1 INTEGRAL OPEN MESH SPOOL An apparatus for forming an integral open mesh wound spool includes an elongated arbor rotatable about its longitudi ial axis and a feeder head for guiding an elongated strip of material to the arbor. The head is reciprocally movable longitudinally of the arbor for winding the strip about the arbor in a reversible spiral to form an interleaved diamond pattern. The rotary movement of the arbor and the longitudinal movement of the head are coordinated so that a predetermined odd number of diamonds are formed in the circumferential rows of diamonds and the number of diamonds in the circumferential rows and the number of diamonds in the longitudinal rows have only unity as a common .factor. Longitudinal movement of the head may be interrupted while rotation of the arbor continues in order to provide integral, circumferentially extending bands of the strip material.

The apparatus also may include a bath of adhesive in a liquid state and guides for conducting the strip of material thru the bath forcoating the strip material with the adhesive prior to winding the spool. Also at least one wiper mechanism may be provided in conjunction with the bath for removing excessive adhesive from the strip the wiping action of the wiper mechanism may be coordinated with the feeder head for momentarily releasing the wiper mechanism to pass wiped strip material so that the unwiped strip material. is wound on the arbor at positions other than apexes of the diamonds.

The arbor may be in the form of a split sleeve which may be selectively contracted to enhance removal of formed spools and collars may be positioned about the sleeve for positively defining theaxial length of spools formed on the sleeve.

BACKGROUND OF THE INVENTION This invention relates generally to an improved open mesh wound spool which can be wound to exacting dimensions on automatic equipment. There are many applications in which an essentially self-supporting open mesh spool is'useful. For instance, in forming encapsulated transformers, that is transformers in which the transformer windings are encapsulated or encased in a material such as an epoxy resin and sand mixture, it is desirable for the coils to be supported on an open mesh spool. Providing openings in the supporting spool for such a transformer allows better penetration of the epoxy-sand mixture and more complete removal of unwanted vapors.

In the past it has been possible to form open mesh v spools by winding a strand of materialon what is essentially a conventional lathe mechanism. However, such spool forming apparatus and spools have a number of disadvantages. With such an apparatus the end portions of the open mesh spools became unuseable and must be cut off and thrown away. Additionally circumferentially extending bands of the spool forming material cannot be wound during the diamond pattern winding process and must therefore be wound over the outside of the diamond pattern at predetermined locations to form the ends of the spools. Normally such, spools 1 process and still the bands and the diamond pattern are not truly integral. Additionally the diamonds cannot readily be varied in order to fit the diamond pattern to the desired spool length.

There is a need, therefore, for a improved, open mesh spool and for an apparatus for automatically winding such spools.

Accordingly it is an object of this invention to provide an improved integral open mesh spool.

It is another object of this invention to provide such an improved spool which. may be formed from an elongated strip of material in a continuous operation, including an open diamond pattern body portion with integral, circumferentially extending bands.

SUMMARY OF THE INVENTION According to one form of present invention, there is provided an integral, open mesh, spool of generally cylindrical form wound from an elongated strip of material. At least a portion of the strip is disposed in a reciprocating sprial to from a plurality of interleaved diamonds disposed in a circumferential and axial rows with the circumferential apexes of one circumferential row coinciding with the axial apexes of the axially adjacent circumferential rows. The direction of spiral of the strip of material is substantially instantaneously reversed at the axially outer apexes of the circumferential row of diamonds adjacent to each end of the spool.

There is an odd number of diamonds in each of the circumferential rows and the number of diamonds in each circumferential row and the number of diamonds in each axial row have only unity as a common factor.

Also there is provided an improved apparatus for forming an integral, open mesh, wound spool. The apparatus includes an elongated arbor rotatable about its longitudinal axis and a feeder head for guiding an elongated strip of material to the arbor. The feeder head is reciprocably movable longitudinally of the arbor for winding the strip about the arbor in a reversible spiral to form an integral diamond pattern. The apparatus also includes means for coordinating the rotary movement of the arbor and the longitudinal movement of the feeder head such that there is formed a predetermined odd number of diamonds in each circumferential row of diamonds and a predetermined number of diamonds in each axial row of diamonds, with a numberof diamonds in each circumferential row and the number of diamonds in each axial row having only unity as a common factor. The apparatus further includes means for interrupting longitudinal movement of the head while allowing continual rotary movementof the arbor for integrally forming circumferentially extending bands of the strip of material at the axial ends of the interleaved diamond pattern.

The subject matter which we regard as our invention is particularly. pointed out and distinctly claimed in the concluding portion of the specification. The invention itself, however, together with further objects and advantages thereof, may be better understood by reference to the following description taken in conjunction with the accompanying drawings.

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 in the drawings is a simplified somewhat schematic front elevational view of the spool forming apparatus for forming open mesh spools in accordance with I one form of the present invention, the view being partially broken away for purposes of illustration;

FIG. 2 is a partial somewhat schematic side elevational view of the spool forming apparatus of FIG. 1;

FIG. 3 is a somewhat enlarged generally as seen along line 33 in FIG. 1;

FIG. 4 is a somewhat enlarged view generally as seen along 4-4 in FIG. 1;

FIG. 5 is a somewhat enlarged elevational view of a collar suitable for use with the arbor of the apparatus of FIG. 1; and

FIG. 6 is a somewhat simplified side view of a typical integral, open mesh spool formed in accordance with one form of the invention.

Referring now to the drawings, and particularly to FIGS. 1 and 2, there is shown a new and improved spool forming apparatus 10 for forming open mesh spools in accordance with one form of the present invention. Theapparatus 10 may be somewhat similar to a lathe, including a bed 11 supported by a pair of upright end structures 12 and 13. End structure 13 houses and supports the power source or the drive mechanism 14. The drive mechanism 14 conventionally may take the form of an electrically energized motor and gear reduction unit which terminates in an output shaft 15.

A first sprocket 16 is mounted on the output shaft for rotation therewith and is connected by a chain 17 to a second sprocket 18 mounted on a stub shaft 19. A cup like arbor drive 20 is mounted to the other end of shaft 19 for rotation therewith. An arbor 21 includes an elongated, generally cylindrical sleeve 22 mounted on an elongated shaft 23 for rotation therewith. One end of the shaft 23 includes a pin 24 and is received in the cup like drive member 22 with the pin 24 received in a slot 25 in the drive member. The other end of shaft 23 is mounted on a conical centering member 26,

which, in turn, rotates with a freewheeling stub shaft I 27. With this arrangement, so long as the drive mechanism 14 is operating, the arbor drive member 20 will rotate the arbor.

The distal end of output shaft 15 is drivingly received in a conventional one revolution clutch 28 and forms the input to the clutch. The output of the clutch 28 is in the form of a shaft 29. A sprocket 30 is mounted for rotation with the shaft 29 and is connected by a chain 31 to a sprocket 32 mounted on a shaft 33. Proper tension is maintained in the chain 31 by idler sprockets 34 in a conventional manner. Similarly idler sprocket 35 maintains proper tension in chain 17.

Shaft 33 provides the input to an instant reversal mechanism 36 which has an output shaft 37. The instant reversal mechanism is capable of reversing the direction of rotation of shaft 37 substantially instantenuously. One instant reversal mechanism particularly suitable for use with the spool forming apparatus 10 is shown and described in copending application Ser. No. 209,183 filed concurrently herewith, now US. Pat. No. 3,766,794, and assigned to General Electric Company, assignee of the present invention. With this mechanism, so long as one revolution clutch 28 transmits motion from shaft 15 to shaft 29, shaft 33 will drive reversal mechanism 36 and shaft 37 is rotated in a predetermined direction. One revolution clutch 28 is designed such that, upon proper energization, it will prevent rotation of shaft 29 for one revolution of shaft 15' and then will automatically reconnect shaft 29 to shaft 15. With this arrangement shaft 33 may be selectively stopped for one revolution of shaft 15 and thus one revolution of arbor 21.

The shaft 37 is the input shaft for gear mechanism 38 which includes an output shaft 39. Referring particularly to FIG. 3, it will be seen that the gear mechanism output shaft 39 is supported in and extends through a box-like cross frame 40, which extends between the end structures 12, 13. A sprocket 41 is mounted on the distal end of the shaft 39. As best seen in FIG. 1, a chain 42 extends between sprocket 41 and an idler sprocket 43. The

sprockets

41 and 43 are spaced sufficiently apart on the cross frame 40 that chain 42 spans the entire length of the cylindrical sleeve portion 22 of the arbor 21. Thus, rotation of the shaft 37 causes the sprocket 41 to move the chain 42 longitudinally of the cylindrical sleeve 22.

A feeder head mechanism generally indicated at 44 is mounted for longitudinal movement along the frame 40. In the exemplification, the feeder head mechanism includes an angle bracket 45 which is supported from the frame 40 by means of roller bearings 46. Each of the roller bearings engages a differentlongitudinal surface of the frame 40 and are provided in pairs at diagonally opposite comers of the cross frame 40 so that the bracket 45 will move longitudinally of the cross frame without any tilting or shifting motion. An attachment mechanism generally and somewhat schematically illustrated at 47 is fixidly attached to the frame 45 and removeably connects the frame 45 to the chain 42. Thus the attachment mechanism 47 operatively connects the frame 45 to the chain 42 and, at the same time allows, the bracket 45 to be selectively positioned relative to the chain and thus relative to sleeve 22.

A first arm 48 is firmly connected to the bracket 45 by mounting block arrangement 49 and projects outwardly and downwardly from the frame toward the sleeve 22. A second arm 50 extends outwardly and downwardly from the first arm 48. The

arms

48, 50 include cooperating slots 51, 52 which receive a nut and bolt 53 so that the position of arm 50 relative to arm 48 may be selectively adjusted. A guide arm 54 is pivotally attached to arm 50 at 51 and is selectively held in a desired position relative to arm 50 by a pin and slot arrangement generally shown at 55. An elongated, slotted guide 57 is carried by the pivot arm 54. By proper positioning of arm 50 relative to arm 48 and pivoted arm 54 relative to arm 50 the lower end of slotted guide 57 may be placed adjacent to the sleeve portion 22 of arbor 21 and the appropriate relationship between guide 57 and sleeve 22 may be maintained even through arbors having different size sleeves 22 are used with the spool forming apparatus.

A strip of spool forming material is fed through the slotted guide 57 to the cylindrical sleeve 22 of the arbor 21 to form a wound spool about the sleeve 22. Energization of the drive mechanism l4causes the arbor 21 and thus the cylindircal sleeve 22 to rotate about its longitudinal axis. The feeder head mechanism 44, and

thus the slotted guide 57, is moved longitudinally of the sleeve 22 by the chain 42 and sprocket 41. Selective energization of the motion reversing mechanism 36 will cause the direction of rotation of the feeder head mechanism 44 to periodically reverse in a substantially instantaneous manner so that the strip of spool forming material is wound on the sleeve 22 in a reciprocating spiral to form a plurality of interleaved diamonds. The diamonds are disposed in circumferential rows and in axial rows with the apexes of the diamonds of one circurnferential row coinciding with the axial apexes of the adjacent circumferential rows. By selective energization of the one revolution clutch 28, longitudinal movement of the feeder mechanism is interrupted for one-revolution of the sleeve 22. This causes strip forming material to be wound about the sleeve 22 in a generally cylindrical manner.

In many applications for open mesh, wound spools, such as a spool to support windings in a cast transformer, it is necessary that the finished spool be selfsupporting. To this end the strip of spool material includes one or more essentially .continuous strands of contains a supply of suitable adhesive resin material. It,

may include heating means.(not shown) for maintain.- ing the resin at a suitable temperature. Located within the bath and below in the normal liquid level is a series of

hardened pins

61, 62, 63. As the spool forming material is led through the bath it passes under pin 61, over a pin 62 and underpin 63 so that the pins can insure that each of the strands or filaments as suitably coated or impregnated with the resin. Two additional pins, 64, 65

are located above the normal liquid level of the bath and in fact may be above the open top of the container 60. These pins form part of a wiping mechanism which also include wiping

blades

66, 67. The coated filament or strand material passes between the

pins

64, 65 and the cooperating wiping

blades

66, 67 to wipe excess resin material from the strands. A pair of solenoids 68, 69 are positioned for momentarily moving the

wiping blades

66, 67 away from the cooperating pins 64, 65 in order to momentarily release the wiping action.

By way of example, when it is desired to use the wound spool as the coil supporting structure in a cast transformer, the filament material advantageously may take the form of one or more rovings 70 of glass fibers, it being understood that each roving may contain a number of ends or strands. The adhesive advantageously may be a low molecular weight epichlorohydrin-bisphenol-A epoxy resin with 2-ethyl-4-methyl imidazole as an accelerator. The low molecular weight resin crosslinked withan accelerator provides a spool with a high distortion temperature 'lhe rovings 70 are led individually thru thebath, including passingover the pins and thru the wiping mechanism and then are brought together in an essentially unitary strip of spool forming material by the slotted guide 57. Glass fiber roving, particularly when coated with an epoxy resin, will provide a mechanically strong spool. The glassfibers provide. high mechanical strength particularly in the circumferential or radial direction relative to the spool. While glass fiber alone will not provide high mechanical strength longitudinally of the spool, coating the rovings with an epoxy resin greatly enhances the longitudinal strength of the finished spool.

Each of the rovings is formed of a number of ends or strands and an individual strand may be broken or discontinuous at one or more points in the roving. As the roving passes thru the wiping

mechanism thewiping arms

66, 67 may catch the end of an individual strand and tend to cause it to bunch up at the wiping mechanism rather than passing through. Momentarily moving the wiping arm away from its associated pin to release the wiping action will allow any build up of individual strands or fibers to pass through the wiping mechanism. This allows the apparatus to run for a considerable period of time without forming large unwanted masses of material.

After winding it is often advantageous to heat the formed spools, while they remain on the arbor, in order to accelerate the curing of the resin or hardening of other adhesive which has been used. This may bedone advantageously by a conveyor type oven through which the arbor and the spools wound on it pass forelevating the temperature of the adhesive and thus accelerating its curing; To this end, a pair of

roller bearings

71, 72 are mounted about the arborshaft 23 so that the arbor may be placed on the conveying mechanism of the conveyor by means of the roller bearings and thus move thru the furnace. At least one sprocket 73 is firmly attached to the shaft 23. It will be engaged by a continuous chain within the furnace, which travels at a different speed than the

conveyor engaging bearings

71, 72. With such an arrangement the arbor 21 will be rotated about its longitudinal axis as it passes thru the furnace. This prevents droop of the spool material before the adhesive curesand prevents the resin from collecting along one portion of the spool before it cures.

In order to build up spools, particularly multi-layer spools having square, clearly defined ends a number of collars 76 may be mounted about the sleeve 22 with the axially adjacent surfaces of a pair of adjacent collars being positioned to define the axial extremities of a spool to be wound between those collars.

Referring particularly to FIG. 5 it will be seen that the collars 76 are of a generally ring like figuration and have a central opening 77 which is substantially the size of the sleeve22 so that the collar will remain in place about the sleeve. The circumferential outer surface of the collar includes a pair of sloped portions 78 which are slanted or angled with respect to the axis of the collar. When collars are mounted on the sleeve 22 one of the angled portions 78 is disposed toward a spool to be formed. Thus, any spool forming material which is wound on the collars will tend to slide off of the collars onto the sleeve 22. This sliding off of spool forming material is enhanced by forming the outer surface of the collars of a low friction material. By way of example the collars could be constructed from steel and coated with a low friction material such as tetrafluoroeth elene. Alternatively the collars may be constructed from a low friction material such as tetrafiuoroethelene.

Referring now to FIG. 4 additional details of structure of the arbor 21, and particularly the sleeve 22, are shown. The sleeve 22, is preferably constructed from a sturdy material such as steel and is mounted to the shaft 23 by a number of radially extending arms 80,-which are firmly connected to the shaft and to the sleeve by some. suitable means such as welding. The arms 80 preferably are connected to the sleeve 22 at positions opposite a slot 81 which extends longitudinally of the sleeve. Adjacent each end of the sleeve 22 a pair of

arms

82, 83 extend from each side of the slot 81 and overlap. A rod extends lengthwise of the sleeve 22 includes a pair of reduced diameter off centerend portions, one of which is shown at 84. The portions 84 are rotatably received in mating openings in the arms 83 so that, when the shaft is rotated it will rotate within the arms 83 about the reduced diameter portions 84. The larger, central portion 85 of the rod in effect forms an eccentric about the axis of the reduced diameter portions 84 and this eccentric is received in an elongated slot 86 in each of the arms 82. As the rod is rotated 90 degrees about the reduced diameter end portions 84 the larger or eccentric central portion 85 moves within the slots 86 causing the

arms

82, 83 to move relative to one another. This causes the slot 81 either to open or close. By closing the slot 81 the effective diameter of the sleeve 22 is slightly reduced. This enables the cured spools to be removed from about the outer circumference of the sleeve 22. It also will allow the collars 76 to be placed in exactly the desired position on the sleeve 22. Thereafter when the shaft is rotated about reduced diameter portions 84 the sleeve 22 is expanded and firmly locks the collars in place about the outer periphery of the sleeve. To expedite removal of formed spools the outer surface of sleeve 22 advantageously can be formed as a low friction surface. By way of illustration, a separate sleeve 87 of a low friction material such as tetrafiuoroethelene is shown mounted about the metal sleeve 22.

With the exemplification apparatus shown in FIG. 2 the collars 76 are placed in the desired location of sleeve 22 in order to positively define the axial limits of a pair of spools. The arbor 21 then is placed between the arbor drive member 20 and the conical centering member 26. The attachment mechanism 47 is released from the chain 42 and the feeder head mechanism 44 is moved so that slotted guide 57 is in alignment with the axially inner edge of the collar defining one end of one of the spools. The attachment mechanism 47 is then firmly attached to the chain 42.

Energization of the drive mechanism 14 causes the arbor 21 to rotate about its longitudinal axis and feeder head mechanism 44 to be reciprocated longitudinally of the arbor. The strip of coil forming material is fed from the slotted guide 57 on to the sleeve 22 in a reciprocating spiral fashion between an opposed pair of the collars 76. When the coil forming strip has formed a complete pattern of open mesh, interleaved diamonds the one revolution clutch 28 is actuated to stop feeder head mechanism 44 while arbor 21 rotates through one revolution. This causes a cylindrical band of spool forming material to be wrapped about the sleeve 22 adjacent one of the collars 76. Most conveniently this will be done first by actuating clutch 28 when the feed head has one pass remaining. This will form a band at one end of the spool. Then the last spiral pass across the axial length of the spool is made to complete the spiral pattern and the clutch is again actuated to form the cylindrically extending band at the other end of the spool. The arbor and feeder head mechanism then are at the beginning point of thewinding pattern and the pattern may be repeated in order to build up multi layers of coil forming material with essentially the same pattern.

The spool forming apparatus is designed to automatically proceed through a spool forming process generally as described above and, if desired, to repeat the process a predetermined number of times to build up a multi layer spool with the coil forming material of each successive layer being layed down essentially exactly on top of the preceeding layers. There are a number of advantages in building up a multi layer spool with a relatively small number of strands in each layer. As discussed above, coating the strands with an adhesive, particularly coating glass fiber strands with poxy resin, enhances the structural strength of the spool formed with the strands. By using a relatively small number of strands in the strip the coating operation is more complete and better strength results. Also a spool formed of glass fibers has a high dielectric constant when measured across the fibers but a relatively low dielectric constant when measured longitudinally of the fibers. Coating each of the strands or fiberswith a suitable resin substantially increases the longitudinal dielectric constant. Further, when such a spool is used as a coil support in a transformer, any voids in the spool can result in unwanted corona discharge during transformer operation. By making the spool from a number of layers, each of which has a fairly small number of well coated strands, the number and size of voids is greatly reduced. By forming a number of layers with an open mesh center portion and integral circumferentially extending end bands the center portion and end bands of the final spool are truly integral and the final spool is stronger.

The operation of various active components of the apparatus are controlled and interrelated to provide such a multi layer operation by means of a control mechanism including a tape reader 90, which responds to prepunched holes in an endless tape 91 in order to control acutation of various components of the spool forming apparatus at the appropriate times. The tape reader is driven by means of an input gear 92 which meshes with an output gear 93 that, in turn, is mounted for rotation by shaft 33. Thus the tape reader is driven from the apparatus drive mechanism 14 through shaft 15, one revolution clutch 28, shaft 29, sprocket 30, chain 31, and sprocket 32 to shaft 33. The tape reader may conveniently be of .the generally available type such that rotation of the input gear 92 causes the tape to be advanced in a step-like manner to bring succeeding portions of the tape to the reading head as the gear 92 rotates through various segments of a revolution. Each portion of the tape may be punched to provide appropriate signals to give the desired operation of the various active components of apparatus 10.

Assuming for the moment that gear 30 and gear 32 are provided with a 1 to 1 gear ratio, as by providing each of them with 20 teeth, then the tape reader easily could be driven so as to advance the tape 10 steps per revolution of gear.30. This would provide 10 possible positions during one revolution of shaft 15, and thus one revolution of arbor 21, during which the tape reader can activate the instant reversal mechanism 36 to reverse the direction of longitudinal movement of the feeder head mechanism 44. Since a complete diamond pattern for a spool will be formed by reversing the feeder head mechanism once at each possible reversal point at each end of the pattern, such an arrangement would provide a spool having 10 diamonds in each circumferentially extending row of diamonds. If it is desired to provide a different number of diamonds in each circumferenital row of diamonds it merely is necessary to change the ratio of the teeth in

sprockets

30, 32. For instance, 18 teeth in

sprocket

30 and 20 teeth in 32 would then provide nine possible reversal points for each revolution of the arbor 21 and thus would provide a diamond pattern having nine diamonds in each circumferential row. Similarly a ratio of 22 teeth for sprocket to 20 teeth for sprocket 32 would provide a diamond pattern having 11 diamonds in each circumferential row.

For purposes of illustration and in order to coordinate the explanation with the illustrative spool shown in FIG. 6 (which has nine circumferential diamonds per row and I3 diamonds per axial row of diamonds) it is feeder head were reversed each time the arbor has made a complete revolution there would tend to be formed nine diamonds in each axial row. In order to form the spool shown in FIG. 6, in which there are 13 diamonds in each axial row, the arbor is rotated 13 increments, that is thirteen-ninths of a revolution between each reversal of the feeder head mechanism. The number of increments advanced between reversals is determined by proper punching of the tape 91 so that the instant reversing mechanism is energized under the control of the tape reader at the desired points in the revolution of the arbor.

As explained briefly above, a complete open mesh interleaved diamond pattern of essentially uniform size diamonds is formed once the feeder head mechanism has reversed one time at each of the possible reversal points at each end of the spool and returned to the beginning point of the pattern. If the feeder head mechanism returns to the beginning point of s spiral pattern prior to having reversed at each of the other possible reversal points a complete diamond pattern will not have been formed yet the mechanism will then retrace its previous path. Therefore, the pattern for forming the diamonds must be such that the feeder head mechanism returns to the beginning point only at the completion of the entire pattern. Also, if the reversals are counted from the beginning point the odd numbered reversals occur at the opposite end of the pattern and the even numbered reversals occur at the beginning end of the pattern We have found that a specific relationship between the number of diamonds in each circumferential row of diamonds and the number of diamonds in each axial row must exist in order to automatically form a complete uniform diamond pattern as an integral unit. With the required relationship no even number (less than twice the number of diamonds in a circumferential row) when multiplied by the difference in the number of diamonds in a circumferential row and the number of diamonds in an axial row can provide a number which is evenly divisible by the number of diamonds in a circumferential row. With this requirement two relationships should exist between the number of circumferential diamonds and the number of axial diamonds. First, the number of circumferential diamonds should be odd. Secondly the number of circumferential diamonds and the number of axial diamonds should have only unity as a common factor.

The exemplification spool of FIG. 6 clearly meets these criterion since the number of diamonds in a circumferential row is nine (an odd number) and the diamonds in a circumferential row (nine) and the diamonds in an axial row (13) have only unity as a common factor.

The spool 94 illustrated in FIG. 6 clearly shows the desired general relationship of components of a spool in accordance with the present invention and which is obtained with the exemplification apparatus. The strip 95 of coil forming material has been wound in a reciprocating spiral in a central portion to provide a number of interleaved diamond shaped openings 96 defined by the strip of material. The diamonds are formed in circumferentially extending rows as indicated by line 97 and a axially extending rows as indicated by line 98. The diamonds are all essentially the same size and with their interleaved relationship apexes such as 99 and 100 are circumferential apexes of one diamond opening 96a and are the axial apexes of

diamonds

96b, 96c in one circumferential row axially adjacent to the row in which 96a lies and are axial apexes of diamonds 96d and 96e in the other axially adjacent circumferential row of diamonds. The strip 95 of spool forming material is also wound into a pair of circumferentially extending end bands 101, which are formed integrally with the open mesh center portion and overlie the axially outer apexes of the two circumferential end rows of diamonds. This provides positive control of the spool length and enhances the mechanical strength of the spool. It will be understood that, since the tape reader 90 controls the one revolution clutch 28, if additional circumferentially extending bands are desired at locations other than the ends of the spool, they can be wound intersecting any circumferentially disposed row of diamond apexes without adversely effecting the winding pattern.

While the number of diamonds in an axial row is determined by the incremental rotation of arbor 21 be tween reversals of the feeder head mechanism, the axial width of the diamonds is determined by the longitudinal speed of the feeder head mechanism 44. This basically is a function of the gear ratio between sprocket 41 and sprocket 30, which sets the basic rotational speed of sprocket 41. A sprocket 41 is chosen in size to provide a feeder head speed which give an optimum axial diamond width. Gear mechanism 38 may be included in order to easily vary the feeder head speed. By way of illustration, the gear mechanism 38 may include several matched pairs of gears generally shown 103, 104, and 106. Each pair of gears is controlled by a clutch (not shown) so that only one set of gears is effective or operative at any one time. By way of example gear set 104 may be provided with a one to one gear ratio so that the speed of feeder head 44 is effectively determined by sprocket 41 and sprocket 30. Then'gear pairs 102 and 103 may provide slightly higher speeds of sprocket 41 while gear pairs 105 and 106 may provide slightly lower speeds of sprocket 41. This will modify the speed of feeder head 44 and thus change the axial diamond width.

Considering for a moment the formation of spools to be used to support windings in cast transformers, the optimum spool may be provided by determining the optimum circumferential diamond width and the optimum axial diamond width and then constructing an arbor with a sleeve 22 of appropriate circumferential size to exactly fit the optimum circumferential diameter length and winding a spool thereon of the appropriate overall length to exactly fit the optimum axial diamond length. However, it is not always possible to vary the overall spool size in order to provide the optimum diamond opening. For instance it may be desired to use spools formed on the exemplification apparatus in order to form transformer coil structures to go into already designed transformers. Thus the spool structure must be made to fit the other components. Also other factors may be controlling in a particular design so that the spool structure must be varied somewhat from the optimum in order to satisfy other overiding requirements.

The exemplification apparatus is capable of being easily adjusted in order to provide the required overall spool size while maintaining close to optimum diamond size. Assume for purposes of illustration that the optimum circumferential diamond length is 2% inches and the optimum axial diamond length is 6/10 of an inch. An optimum spool such as illustrated in FIG. 6 would have an inside circumferential of nine (the number of circumferential diamonds) times 2% inches. However, quite often other criteria will dictate a specific inner-circumferential size for the spool. This required circumferential in inches is divided by 2% inches to provide the desired number of circumferential diamonds; however, in all probability the answer will not be a whole number. The answer then is rounded off to the nearest odd number (remembering that it is required that there be an odd number of diamonds in each circumferential row). This nearest odd number than provides the actual number of circumferential diamonds to be wound and is provided by changing one of the

sprockets

30, 32 to provide the appropriate gear ratio. This will vary the actual circumferential length of the individual diamonds form the optimum but such variation will be small. By varying the number of circumferential diamonds to the nearest odd number the error introduced in the ratio between sprocket 41 and sprocket is sufficiently small that the optimum de- As explained previously the collars 76 are placed on the sleeve 22 and spaced apart exactly the required spool length. The pattern is started with the spool forming material against one of the collars. By using a larger number of diamonds (if possible) where the desired number of diamonds is essentially half way between possible numbers and by using a larger gear ratio any error will tend to cause the apparatus to wind a pattern which is slightly longer than that set by the collars. However, as explained above the collars include portions 78 which slant inwardly toward the spool and are provided with low friction surfaces. Thus any overage in diamond winding will be wound on the slanted portions 78 and will slide off of these portions down onto the sleeve 22. Thus the collars effectively confine the spool to the desired length and any extra buildup of material is provided at the axial ends, which have the circumferentially extending integral bands. Any such build tends to provide stronger ends without materially altering the open mesh diamond pattern.

The tape reader performs at least one additional function, that is actuation of solenoids 68 and 69 to relieve thev wiping action on the spool forming material as it passes through the bath. The tape reader coordinates this release of wiping action with the winding on the arbor so that any buildup of material passed out of the bath will be wound on the spool at points other than in the circumferentially extending end bands.

While we have described what at present are considered to be the preferred embodiments of the present sired axial diamond width (six-tenths of an inch in the illustration) can be used in calculating the actual number of axial diamonds. The required total axial length of the spool (in inches) is divided by the desired diamond axial length (six-tenths inch). This answer probably will not be a whole number. You choose the nearest whole number which has only unity as a common factor with the number of circumferential diamonds. If both of the two nearest numbers are possible and the fraction is close to a half it is normally better to go to the higher number. This number is the whole number of axial diamonds. The required axial spool length then is divided by whole number of axial diamonds. This gives the desired axial feed of the feeder head per axial diamond. The ratio of the desired axial feed per diamond to the optimum axial diamond length (six-tenths of an inch in the example) is the gear ratio desired in gear box 38. Since this number will vary only slightly from a one to one ratio it may be sufficiently approximated by having gear pair s 102 and 103 step down the gear ratio from one to one by only one or two teeth each and having the gear pairs 104 and 105 step up the gear ratio only one or two teeth each. The particular gear pair chosen for use is the one having the closest ratio to the actual ratio. Again if the actual ratio is essentially half way between two available ratios it is normally better to go to the larger.

ivnention, it will be understood that various modifications may be made therein without departing from the invention. Therefore it is aimed in the appended claims to cover all such modifications which fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent in the United States is:

1. An integral open mesh, wound spool of generally cylindrical form including: a body portion of a crossed material, defining a plurality of generally diamond shaped openings; said material including at least one filamentary strand; and a pair of spaced apart, substantially solid, circumferential end portions; said body portion and said end portions being formed from an essentially continuous strip of material; said wound spool being substantially self supporting.

2. A wound spool as set forth in claim 1 wherein: each of said diamonds has a predetermined length circumferentially of said spool and a predetermined length axially of said spool.

3. A wound spool as set forth in claim 1 wherein: the diamonds are in rows circumferentially of the spool and rows longitudinally of the spool; there being a predetermined odd number of diamonds in each circumferential row; and the number of diamonds in each circumferential row and the number of diamonds in each longitudinal row have only unity as a common factor.

4. A wound spool as set forth in claim 1 wherein: said strip consists of plurality of strands of filamentary material coated with a resin so that spool is self-supporting upon curing of said resin.

5. A wound spool as set forth in claim 1 wherein said strip consists of a plurality of strands of glass fiber coated with an epoxy resin.

6. A wound spool as set forth in claims 5 wherein said epoxy resin is epichlorohydrin-bisphenol-A.

l 7. An integral, open mesh, wound spool of generally cylindrical form: said spool including multiple layers; each layer having a body portion of a crossed strip of material forming a plurality of generally diamond shaped openings; said crossed strip of each layer being in substantial register with said crossed strip of each of the other layers; at least some of said layers including a continuous end portion of cylindrically wound strip material overlapping the axially adjacent strip material of said body portion; said strip material of said body portion and said end portion being essentially continuous.

8. A wound spool as set forth in claim 7 wherein each of said diamonds has a predetermined length circumferentially of said spool and a predetermined length axially of said spool.

9. A wound spool as set forth in claim 7 wherein: the diamonds are in rows circumferentially of the spool and rows longitudinally of the spool; there being a predetermined odd number of diamonds in each circumferential row; and the number of diamonds in each circumferential row and the number of diamonds in each longitudinal row have only unity as a common factor.

10. A wound spool as set forth in claim 7 wherein: the strip consists of a plurality of strands of filamentary material coated with a resin so that said spool is selfi supporting upon curing of the resin.

11. An integral, multiple layer, open mesh, spool of generally cylindrical form wound from an elongated strip of material; said layers being in substantial register with one another; at least a portion of said strip being disposed in a reciprocating spiral to form a plurality of interleaved diamonds disposed in circumferential and axial rows with the circumferential apexes of one cir cumferential row coinciding with the axial apexes of the axially adjacent circumferential rows; the direction of the spiral of said strip being reversed at the axially outer apexes of the circumferential row of diamonds adjacent each end of said spool; there being an odd number of diamonds in a circumferential row; and the number of diamonds in a circumferential row and the number of diamonds in an axial row having only unity as a common factor.

12. A spool as set forth in claim 11, in which other portions of said strip of material provide circumferential bands overlying the apexes at which the direction of spiral reverses.

13. A spool asset forth in claim 11 wherein said strip is a filamentary material coated with a resin so as to be self-supporting upon curing of said resin.

Claims

7. An integral, open mesh, wound spool of generally cylindrical form: said spool including multiple layers; each layer having a body portion of a crossed strip of material forming a plurality of generally diamond shaped openings; said crossed strip of each layer being in substantial register with said crossed strip of each of the other layers; at least some of said layers including a continuous end portion of cylindrically wound strip material overlapping the axially adjacent strip material of said body portion; said strip material of said body portion and said end portion being essentially continuous.

10. A wound spool as set forth in claim 7 whereiN: the strip consists of a plurality of strands of filamentary material coated with a resin so that said spool is self-supporting upon curing of the resin.

11. An integral, multiple layer, open mesh, spool of generally cylindrical form wound from an elongated strip of material; said layers being in substantial register with one another; at least a portion of said strip being disposed in a reciprocating spiral to form a plurality of interleaved diamonds disposed in circumferential and axial rows with the circumferential apexes of one circumferential row coinciding with the axial apexes of the axially adjacent circumferential rows; the direction of the spiral of said strip being reversed at the axially outer apexes of the circumferential row of diamonds adjacent each end of said spool; there being an odd number of diamonds in a circumferential row; and the number of diamonds in a circumferential row and the number of diamonds in an axial row having only unity as a common factor.

13. A spool as set forth in claim 11 wherein said strip is a filamentary material coated with a resin so as to be self-supporting upon curing of said resin.