US2260011A

US2260011A - Stationary induction apparatus

Info

Publication number: US2260011A
Application number: US296940A
Authority: US
Inventors: Herbert L Driftmeyer
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1939-09-28
Filing date: 1939-09-28
Publication date: 1941-10-21
Anticipated expiration: 1958-10-21

Description

Oct. 21, 1941. H. L. DRIFTMEYr-:R 2,260,011

I STATIONARY INDUCTION APPARATUS Filed Sept. 28, 1959 4 Sheets-Sheet Fig. s.

' Il Y WW' 9.7 Inventor:

Herbefb L. Dr'tmeger,

,Oct 21, 1941.- H 1 DRIFTMEYER 2,260,011

STATIONARY INDUCTION APPARATUS Filed Sept. 28. 1959 4 Sheets-Sheet 2 His Attorney.

Herbert L. Driftmeger,

Oct. 21, 1941. H. l.. DRIFTMEYER STATIONARY INDUCTION APPARATUS Filed Sept. 28, 1939 4 Sheets-Sheet 3 Inv'entor:

Herbert 'L Drlftmege" 1 b5 #aM/gf J is Attovneg.

Oct. 21, 1941. H. L. DRIFTMEYER 2,260,011

STATIONARY INDUCTION APPARATUS Filed Sept. 28, 1939 4 Sheets-Sheet 4 I nvevfm'. Hevbert LDrftmegeT, b5 C? HIS Attovneg.

`dow of the conductive winding structure.

Patented Oct'. 21, 1941.

STATIONARY INDUCTION APPARATUS Herbert L. Driftmeyer, Fort Wayne, Ind., assignor to General Electric Company, a corporation ol' New York Application September 28, 1939, Serial No. 296,940 C 8 Claims.

My invention relates to wound strip core stationary induction apparatus.

It is an object of my invention to provide improved, fastcr methods and apparatus for applying the wound strip core to the conductive winding structure of stationary induction apparatus, such as transformers and reactors of the wound core type.

Other and further objects and advantages will become apparent as the description proceeds.

In carrying out my invention in its preferred form, particularly in connection with stationary induction apparatus having two parallel winding legs each carrying an annular core or core part, I wind strips of magnetic material flatwise spirally to form a pair of coils of strip with the turns having the same size and shape as they' are to have in the finished magnetic cores, I subject the coils of strip to heat treatment to bring out the most favorable magnetic properties and to give the material a permanent set, I then bring the coils of strip in proximity to the conductive winding structure and transfer the strip from the original coils to the winding legs. The two coils may be applied to the conductive winding structure simultaneously. Each coil is unwound and simultaneously rewound into a larger loop passing through the opening or win- For the sake of speed and certainty in unwinding the original coil and rotating the larger loop, I cause the coils of strip to be driven from the inner end by driving spindles each arranged to engage the inside end of the strip and then release it automatically when. all the material of the original coil has been unwound. When all the material has been transferred to the larger loops they are collapsed to form the finished magnetic cores closely embracing the winding legs. In the collapsing process the larger loops are reduced to smaller size by rotation of collapsing rollers frictionally engaging the outer surfaces of the larger loops. The two loops are tangent in the center of the winding window and rotate together in the same tangential direction at the point of tangency (but in opposite angular directions), thereby facilitating the collapsing process by the frictional engagement between the two loops and by the mutual reaction tending to prevent either strip from being pushed to the opposite side of the winding window by the collapsing rollers.

The invention will be understood more readily from the following detailed description when considered in connection with the accompanying 55 drawings and those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended hereto or appended to my divisional application, Serial No. 398,944, led June 20, 1941. Y

In the drawings, Fig. l is a perspective view of one of the wound-strip annular magnetic cores utilized in one embodiment of my invention. Fig. 2 is a perspective view of a machine for assembling woundcores with conductive winding structures of stationary induction apparatus. Fig. 3 is a perspectiveview of a driving spindle for engaging and driving the coils of strip which are to be transferred to the conductive winding legs. Fig. 4 is a view showing in part a section of the apparatus of Fig. 2 cut by a vertical plane passing transversely through the top center portion of the machine including the arrangement for supporting the winding structure in place. Fig. 5 is an illustration of a linished transformer constructed in accordance with my invention. Fig. 6 is a view showing in part a. section of the apparatus of Fig. 2 cut by a vertical plane passing longitudinally and centrally through the machine. Fig. 7 isa fragmentary plan view of the apparatus of Fig. 2. Fig. 8 is a detail view, as seen from the top, of a socket for receiving the driving spindle of Fig. 3. Fig. 9 is a fragmentary side view of the socket shown in Fig. 8. Fig. 10 is a schematic diagram illustrating an initial step in the process of producing Wound cores, namely, the rst part of the process of winding the strip into a coil.,) Fig. 1l is a schematic diagram showing a further step in the process at which the strip has been wound into the coil. Fig. 12 is a schematic diagram representing a step in the process at which the strip is cut off at the completion of -the coil. Fig. 13 shows the strip as it would appear if unwound from the coil and laid out dat, portions thereof being broken out. Fig. 14 is an elevation partially in section of the core-driving spindle of Fig. 3. Fig. 15 is a plan view (taken on line I5-I5 of Fig. 14) of a portion of the apparatus of the preceding figures showing another step in the process 0f applying the strip to the conductive winding structure at the point where the unwinding of the original coil of strip and the rewinding of the larger loop to the window of the winding structure has just begun. Fig. 16 is a view corresponding to Fig. 15 showing the point in the process at which very nearly all of the strip has been transferred from the original coil and passed through the window of the winding structure. Fig. .17 is a view corresponding to the another, as shown in Fig. 11.

previous two views showing the condition preparatory to the collapsing of the larger loops around the winding legs, and Fig. 18 is a horizontal seftional view of the completed transformer corresponding to the previous views and showing the final result of the core-applying process.

In order to apply the magnetic strips to the conductive winding legs in such a manner that the strip will have the most desirable magnetic properties, the strip is first wound up into coils which may be given suitable heat treatment to bring out the magnetic properties. As shown in Fig. 10 a strip I0 of magnetic material from a large reel II is wound upon a mandrel I2 by securing the end I3 of the strip in a slot I4 in the mandrel and rotating the mandrel. The slot I4 is not exactly radial, but forms a portion of a chord of the substantially circularfcross-section of the mandrel I2, such that a bend I5 is formed in the strip, making an angle of somewhat less than 90 degrees. The mandrel I2 is not exactly circular in cross-section, but has a slightly reduced radius at the portion of the slot I3 on the counterclockwise side of said slot. The difference in radius on either side of the slot I3 is the thickness of the strip I9 in order that when a complete turn of strip has been wound upon the mandrel I2 there will be no bulge above. the bend I5 in the strip and the succeeding layers will lie flatly, substantially circularly above one Actually the surfaces of the mandrel I2 and the successive layers of strip are along a spiral having a radius 'increasing an amount equal to the thickness of the strip I0 for each complete revolution or turn.

The strip I0 is passed through a die and cutter head I6 located between the reel I I and the mandrel I2. The die and cutter I6 has an operating lever I1 and an internal mechanism, not shown, with three positions. In the first position, with the lever I1 perpendicular, as shown in Fig. 10, the strip may pass freely through the head I6. By moving the lever I1 to the second position I3, represented by the dotted lines in Fig. 11, a punch is brought against a die block, such as to cut a rectangular opening I9, as shown in Fig. 13. By moving the lever I1 to the third position 20,

in which the handle I1 is horizontal, as shown in.

full lines, the strip is cut off and simultaneously a hook 23 is punched near the end of the strip. The cut-01T forms the final end 2I of the strip I0 as well as the initial end 22 of the next strip IIJ', corresponding in shape to the initial end I3, which is the end that is inserted in the slot I4 of the mandrel I2.

' The opening I9 is punched near the outer end of the strip by bringing the lever i1 into the p0- sition I8 after nearly acomplete length of strip has been wound upon the mandrel I2. After rotating the mandrel I2 a short distance further, approximately two or three turns, the die operating lever I1 is brought to the position 20 so .as

to cut off the strip and form the hook 23. The

mandrel I2 is then rotated until all of the strip has been Wound up to form the coil 24. It desired, shoes 25 pressing against the surfaces of the coil 24 may be employed to insure that the strip is wound tightly. After the coil 24 has been formed, the end of the strip 2i is preferably fastened down in some suitable manner to avoid unwinding of the strip during anneal. This may be done, if desired, by spot welding. utilizing a welding electrode 26 carried by a pivoted arm having the electrical circuit completed through the shoe 25. The coil ls then ready to be subjected to suitable heat treatment for bringing out its best magnetic loss and magnetizing current properties and giving the material a permanent set. It will be understood that the coil 24 has the turns of the same size and shape as the core of the completed induction apparatus. It will also be understood that the mandrel I2 is so constructed that the coil 24 may be slipped off endwise.

In order to transfer the strip material from the coils, such as the coil 24, to a conductive winding, a pair of coils is placed on driving spindles 35 adapted to engage the bent ends I3, as shown in Fig. 15. A conductive winding structure 21 is placed between a pair of such coils, only one of which is shown in Fig. 15, and the outer ends of the coils are unfastened so that they may be slipped through the opening or window 29 of the conductive winding structure 21. The outer end 2| of the strip I0 is brought around and fastened to the next underlying layer of strip to form a larger loop 30. The fastening may be accomplished quickly by drawing the hook 23 through the opening I9 and pulling the strip back tightly so as to cause the hook 23 to grasp the material at the edge 3| of the opening I9. The spindle 35 is rotated to force rotation of the coil 24 and the larger loop 30, and consequently cause transference of the material from the outside of the coil 24 to the inside of the larger loop 30. The rotation of the drive spindles 35 is continued until substantially all of the material has been transferred to the larger loops 30, as shown in Fig. 16, whereupon the drive spindles 35 are removed. The inner bent ends I3 of the strip are placed in suitable recesses in the winding legs 32. For example, in the case of a cruciform section coil the bent ends I3 may be caused to occupy the corner 32 between the high and low voltage windings. The process as carried out in the foregoing manner avoids any possibility of bending the strip material so far as to strain it beyond the elastic limit, and permits bringing the material back to the original size and shape of turn so that it will befree from elastic strains and it will havel more favorable magnetic properties.

The transformer and reactor assembling machine illustrated in Fig. 2 comprises a table 33, a pair of turn tables 34 for supporting and driving the coils of strip 24 of Figs. 1 and l1, a pair of core-driving spindles 35, shown in Figs. 3 and 14, adapted to fit into sockets in the turn tables 34, a driving motor 36 arranged to rotate the sockets and turn tables 34, a pair of idling pressure rollers 31 for holding the strip in the coils 24 until unwound, two pairs of collapsing rollers 38 for quickly collapsing the larger loops when completed, and a clamping arrangement 39 for holding the conductive-winding structure 21 while the core strip material is being applied.

Preferably the top of the table 33 is so made that its top surface will be flush with the top trude, the coil clamping arrangement 39 of course also being partly above the top surface of the table'33. However, in order to avoid confusion in the drawing, certain other parts, such as a pair of levers 40, springs 4I, and straps 42, the function of which will be explained hereinafter, have been shown above table 33, although they would ordinarily be placed on the under sur- (not shown) connected to a welding transformer 7 5 face of the table top 33 instead of the top surface.

The driving-spindle socket is shown more in detail in Figs. 6, 8, 9, and 14 and designated by the reference numeral 43. It has a cylindrical opening 44 for receiving the driving spindle 35 and is arranged to have the disk forming the turntable 34 fastened to the top thereof by means of screws 45. A shoulder 46 of the thickness'of the coil supporting turn table disk 34 may be provided on the socket 4 3 andthe turn table disk 34 may have an internal opening of such a diameter as to fit around the shoulder 46 and thereby make the top surface of the combined drive-spindle socketand turn table flush. Three keyways 41 angularly spaced about 120 degrees are cut into the turn table 34 and into the spindle driving socket 43. They are shown more clearly in Figs. '7, 8, and 9. At the bottoms of the keyways 41, transverse grooves 48 (Figs. 6 and 9) are provided to form duo-directional bayonet locks for pins in the driving spindle, as will be explained hereinafter. The lower end of the spindle socket 43 has secured thereto the gear 49 transmitting rotative power to the socket 43. It will be understood that a suitable housing 42' including bearings 43' is provided for rotatably supporting the socket member 43. For driving the gear 49 there is a shaft 50 carrying a worm, not shown, engaging the gear 49. For transmitting rotative motion to the shaft 50 there is a vertical shaft with a pair of bevel gears 52 secured to the ends of the shafts 59 and 5|, respectively. A gear box 53 is provided for connecting the motor 36 to the shaft 5|.

The coil driving spindles 35 shown in Figs. 3 and 14 each include a lower cylindrical portion 54 of smaller diameter adapted to fit into the opening 44 of the spindle socket 43, and a rotation-transmitting transverse projecting pin 55 fastened in the projecting end 54 adapted to slide into any one of the keyways 41 of the socket 43 and to lock in either end of the transverse groove 48 to prevent the spindle 35 from jolting out of the socket 43. 'I'he spindle 35 also has a portion 56 (Fig. 3) having a diameter corresponding to the inner diameter of the coil 24 and to the diameter of the winding leg 32 of the conductive winding structure 21. A collar 51 is provided on the portion 56 of the spindle 35 in order to serve as a guide for the strip on the coil 24 as the coil 24 is being unwound. A set screw 58 may be provided for adjustably securing the collar 51 at the proper height for the width of strip in the coil 24. To facilitate handling the drive spindle a handle 58 may be provided.

For receiving the end I3 of the magnetic strip and releasing it at the proper time, a self-opening slot 59 (see Figs. 3, 14, or 15) is provided in the drive spindle 35. This self-opening slot 59 is formed by cutting a sector longitudinally out of the portion 56 of the spindle 35 and providing a pivoted latch 60 with a pivot axis 6| parallel with the axis of the spindle 35, but off center. The latch 60 is adapted to lie against edge 6|' (Fig. l5) of the sector cut into the spindle pori two arms 63 through which pass the pivot pin 6| of the latch 69. The arms 63 are at the upper and lower ends of the lengthwise extending tip portion 62 and extend into transverse slots or recesses 64 in the spindle portion 56. ,To permit the latch tip 62' to swing away from the surface 6|' and open the slot 59, a notch 51 is cut inthe collar 51. It will be observed that the spindle portion 56 has surface elements which dei-lne an outline fitting the inner surface of the coil of strip 24 supported by the spindle 35, that the latch 68 is confined within this outline so long as the strip material is wound upon the spindle portion 56, and that the outer tip 62' extends outside the aforesaid outline when the slot 59 is opened by a separation of the tip 62 from the surface 6|' in the opening in the spindle portion 56.

The idle rollers 31 are carried by suitable sliding bars 64 held in channels in the table 33 by straps 42 and biased by means of springs 4| toward each other so as to bear against coils placed upon the turn tables 34.

The collapsing rollers 38 are carried by swinging arms 65 (Fig. 7) pivoted by securing them to bushings 66 (Fig. 6) surrounding hollow posts 61 around shafts 68, located at either end of the machine but only one of which is shown. For rotatably driving the rollers 38, they are mounted upon shafts 69 carried by housings 10, supported by the swinging arms 65, and pulleys 1| are secured to lower ends of the shafts 69. Pulleys 12 are al'so provided at the lower ends of the shaft 68 and connected to the pulleys 1| by belts 13. The shafts 68 in turn are connected to the drive shaft 50 through gearing 14 as a result of which they are driven by the motor 36. 'I'he arrangement of gearing and belts is such that the righthand pair of collapsing rollers 38 rotates in the opposite direction from the left-hand pair, and the turn tables 34 rotate in the opposite directions from the collapsing rollers on the same side of the machine.

In order to permit the collapsing rollers 38 and their supporting axle housings 19 to be swung in as the loops of strip are collapsed, openings 15 are provided in the table 33. These openings 15 are arc-shaped and of suilicient width to permit the length of the arms 65 to be adjusted for adapting the apparatus to magnetic cores of different diameter. For'permitting the adjustment in length of the arms 65, a suitable arrangement such as joints 16 and elongated-slot-and-bolt arrange- Jments 11 may be provided.

For forcing the collapsing rollers inward as the larger loops of strip are being collapsed, a lever arrangement is provided consisting of a lever 18, a link 19, spreading links and crank arms 8|. The crank arms 8| project from the pivoted ends of the collapsing-roller-carrying arms 65, and the spreading links 89 are each connected at one end to the crank arms 8| and at the other end to the link 19, which is connected to the operating lever 18.

The clamping arrangement 39 for holding the conductive winding structure 31 (Figs. 2 and 4) includes a jaw 82 mounted under a conductivewinding-receiving opening 93 in the table 33 and supported adjustably in height by means of a pivoted lever 84 adjustable by a screw 85. The clamping arrangement 39 also includes an upper jaw 86. For carrying the jaw 86 there is a horizontal arm 81 and a screw arrangement 88 which adjusts the height of the clamp 86 with respect to the arm 81. To permit the insertion and removal of conductive winding structures, the arm 81 is not rigidly fastened, but carried by an arrangement including a vertical post 89 which is plvotally mounted and may be secured by removable fastenings to the table 33. A clamp lifting lever 99 is pivotally secured to the center of the post 89. For fastening the post 89 an opening is provided in the lower end thereof, and there is a pin 9| 'adapted to pass through and to secure the lower end of the post 89 pivotally to the end of a plate 9|', bolted to the table 33. 'I'he lever 99 has a slot 93 at the lower end fitting a fixed pin 94 secured to the table 33 in order to form a lock for the lever 99. A spring 95 maybe provided for swinging the lever 99 and the Winding structure clamp 86 out of the way when the lever 99 is moved to unlock the slot 93 from the pin 94.

Before applying the coiled strip to the conductive-winding structure 21 the winding structure is placed on the clamp jaw 82 with the conductive winding legs 32 vertical, the handle of lever 99 is moved forward to bring the jaw 86 upon the conductive winding structure and to rotate the lower end of the lever 99 upward causing the slot 93 to engage the pin 94 for locking the post 89 in the vertical position to hold the conductive-winding clamp rigid. The screw 83 may be turned to bring the clamp jaw 86 down on the top of the conductive winding. Coiled strips 24 which have been heat treated are mounted on driving spindles 35 and the latter are mounted in the spindle sockets 43.` The coils are mounted upon the spindles 35 by moving the pivoted latch 69 into the position shown in Figs. 3, 14, and l and the spindle portions 56 are placed through the openings or windows 96 in the coils 24 with the bent inner ends i3 of the coils inserted in the slots 59 in the driving spindle 35. Before placing the coils 24 in the turn tables 34, the levers 49 are pressed outwardly by means of the handles 91 in order to move the idling rollers 31 out of the Way. In inserting each driving spindle 35 in its spindle socket 43, the pin 55 is caused to slide into any one of the three keyways 41 and when the lower end 54 of the spindle 35 has been inserted as far as necessary the pin 55 becomes aligned with the transverse groove 48. so that the driving spindle 35 and the coil 24 will be locked in place as soon as rotation of the sockets 43 may be begun. The handles 91 are then released causing the springs 4| to press the idle rollers 31 against the outside turn of the larger loop 30. The, pressure of the rollers 31 causes the strip to be unwound uniformly and rcauses the linear speed of the adjacent portions of strip in the coil 24 in the larger loop 39 to remain approximately the same, so that the coil 24 and the loop 39 remain tangent and the strip will feed smoothly from the coil 24 to the inside of the loop 39. The two coils 24 are so placed on the turn tables 34 that they unwind by being rotated in opposite directions.

Owing to the fact that the latch 69 is pivoted off center it can not be rotated away from the position shown in Figs. 3, 14, am" 15 without pressing against the inner surface of the coil 24. Just so long as the strip remains coiled in the form of the coil 24, the latch 69 is held in place, the bent end of the strip I4 is held in the slot 59 and the spindle 35, driven from the motordriven socket 43 through the keyways 41 and pin 55, produces positive drive of the coil 24 and causes it to rotate and unwind into the larger loop 30, which is in turn caused to rotate thereby. After nearly all of the strip has wound into the larger loop so that there is no longer a complete turn of strip on the spindle portion 56, as shown in Fig. 16, the pivoted latch 69 is released permitting the slot 59 to open up. Thus, the bentA inner end I4 of the strip is released and springs out as a result of the rotation of the spindle 35.

This makes it unnecessary to stop the driving motor 36 at the precise moment that the inner,

turn of coil 24 starts to unwind, and prevents the bent end I3 from being broken oil' or unduly strained. Since the two spindles 35 rotate in opposite directions it will be understood that they must be constructed right hand and left hand but they are otherwise identical and therefore only one form isy illustrated. 'Ihe spindles 3l may then be lifted out of the sockets 43 by means of the handles 68 whereupon the strip material in the larger loops 39 collapses to the position shown in Fig. 17 due to the permanent set which the material has acquired in the heat treatment. The outer ends of the strip are then uniastened and the bent inner ends I4 are positioned in recesses in the winding legs 32. It will be undei-stood that friction of the strip upon the supporting table prevents the strip from collapsing completely as its permanent set would otherwise cause it to do. The levers 18 are then moved toward each other to bring the driving rollers 38 in frictional contact with the magnetic strip, rotating the loops 39 and collapsing them to the size and shape shown in Fig. 18. Since each loop exerts substantially the same pressure as the other at the point of tangency 98, 'the strip is kept approximately at the middle of the winding window 29 so as to minimize the possibility of scraping of the strip material on the conductive winding structure. 'I'he frictional contact at the point 98 also helps to keep the outer layers of both loops 39 in rotation. The directions of rotation are opposite so as to have the same linear direction of motion of the strip at the point of tangency 98. It will be understood that the top surface of table 33 prevents the edge of the strip from dropping against the conductive winding structure at the lower end of the winding window. Although the permanent set of the material tends to keep it in the shape shown in Fig. 18, it may be advantageous to secure the outer ends 2| of the strip to the next adjacent lower layer in some suitable manner as by means of spot welds 99. When the operation is complete the jaw 86 of the winding clamp is loosened, and

the lever 99 is moved back to permit the coment statutes, I have described the principle of operation of my invention together with the apparatus which I 'now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.'

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A machine for assembling wound strip cores with conductive winding structures having pairs of parallel winding legs adapted to be embraced by annular cores, the machine comprising means for holding a conductive winding structure in position with its winding legs vertical, a pair of vertical-axis turn tables adapted to support a pair of flatwise wound coils of magnetic strip material having projections inwardly bent at the( inside of the coils, driving spindles having slots' engaging said inner bent ends of the coils of strip, and power driven collapsingroilers. said turn tables including sockets with keyways, said driving spindles each including a portion adapted to t in one of said sockets and having a pin cooperating with the keyway, means for rotating the turn tables and sockets and the collapsing rollers, said collapsing rollers having pivoted supporting arms, and means for moving the collapsing rollers inward in irictional engagement with the coils of strip.

2. A method of assembling a pair of flatwise spirally wound magnetic cores with a conductive winding structure having a pair of parallel winding legs, said method comprising the steps of bringing a pair of oppositely wound coils of strip in proximity to the winding legs with axes parallel to the winding legs, unwinding the coils of strip and simultaneously rewinding each of them around one of said winding legsand the axis of the coil of strip to form larger loops, then collapsing the larger loops by simultaneously rotating the larger loops in opposite directions with one tangent to the other.

3. A method of assembling a atwise spirally wound coil of magnetic strip around the leg of `a conductive winding structure which comprises unwinding the outer end of such a coil, passing the end around the axis of the coil and the winding leg to form a larger loop, engaging and rotatively driving the inner tip end of the coil of strip for simultaneously unwinding the strip material from the coil and rewinding it into the larger loop, and releasing the inner end of the coil of strip as soon as the inner turn of the coil of strip begins to wind into the larger loop.

4. The method of applying a atwise spirally wound coil of magnetic strip to a conductive winding to form a magneticcore, said method including the steps of passing the outer end of said coil through the winding and back upon the strip to form a loop around one side of the winding, hooking the end of the strip into the underlying portion of the strip in the loop, rotatively driving the inner end of the coil to unwind the coil from the outside and simultaneously rewindA it into the inside of the loop, detaching the outer end of the strip from the portion of the strip underlying and collapsing the rewound strip into a compact cylinder.

5. A machine for applying wound strip magnetic cores to conductive winding structures, comprising means for holding a winding structure in position to be wound, means for supporting a coil of magnetic strip, said supporting means being spaced away from the winding structure a sufiicient distance to permit a relatively large loop of strip from the coil to be threaded through said winding structure, said'supporting means including a spindle inside the coil slotted to receive the inner end of the coil of strip for positively rotatively driving the coil, and a rotatable roller engaging the outside of the coil of strip, and means for biasing the roller toward the spindle to maintain the layers of strip compactly in said coil and in the larger loop.

through the latch arms to form pivots therefor to support said arms pivotally within said sectorshaped recesses, said longitudinal portion of the latch adjacent the side of the sector-shaped opening away from the transverse recesses being cut back suiiciently to form a longitudinal slot between it and saidedge of the longitudinal sectorshaped opening when the latch is deected toward said edge of the opening, said latch being of such dimensions that the outer surface of the longitudinal portion thereof conforms substan tially to the cylindrical surface of said rod when the latch is in the closed position toward said edge of the longitudinal opening, whereby said latch is held in the closed position when a coil of strip having an inner diameter corresponding to the diameter of the cylindrical rod surrounds the rod but the latch is free to deect and open the slot for releasing the inner end of the strip when no strip surrounds the rod. 7. A driving spindle for a wound-strip-core` applying machine comprising a substantially cylindrical rod adapted to be rotatively driven, having a longitudinal opening therein, a movable latch pivotally mounted for movement in said longitudinal opening to form a self-opening longitudinal slot between one edge of the latch and one edge of the longitudinal opening, the pivot axis being so locatedvthat when the latch is released lt may be moved away from the edge of the longtiudinal opening to open the slot.

8. In a machine for applying wound strip magnetic cores to conductive winding structures, means for supporting a coil of magnetic strip having an inwardly projecting inner end, said supporting means including a spindle having surface elements defining an outline fitting the inner surface of a coil to be supported having a self-opening slot to receive the inner end oi the coil of, strip for positively rotatively driving the coil of strip, said spindle including a pair of relatively movable portions with adjacent longitudinal surfaces to form the sides of said self-opening slot, one of said portions having a part which is so shaped as to extend outside the aforesaid outline when the said movable portions are separated to open the slot, said part thereby serving for preventing separation of said portions and opening of the slot when the strip material remains wrapped around the spindle, so long as a turn of strip is wound upon the spindle.

HERBERT L. DRIFTMEYER.