US2963847A - Core wrapping method and apparatus - Google Patents

Description

Dec. 13, 1960 Filed Sept. 2, 1954 C. E. NIXON CORE WRAPPING METHOD AND APPARATUS @L VE I 5 Sheets-Sheet 1 Eur a suaw INVENTOR 6 17/4/9455 5 /V/X0/V BY 63425, H w in/M ATTO R N EY5 Dec. 13, 1960 c. E. NIXON 2,963,847

CORE WRAPPING METHOD AND APPARATUS FiledSept. 2,, 1954 5 Sheets-Sheet 2 A l. FIG.9

INVENTOR 0564/94 619 6. N/X0/V D ATTORNEYS Dec. 13, 1960 c. E. NIXON 2,963,847

CORE WRAPPING METHOD AND APPARATUS Filed Sept. 2, 1954 l4; ;0 5 Sheets-Sheet 3 .ll 41 j w t u 1 E 1. Ln

II l (9' -J- a E E ATTO R N EY$ Dec. 13, 1960 c. E. NIXON 2,963,847

CORE WRAPPING METHOD AND APPARATUS Filed Sept. 2, 1954 5 Sheets-Sheet 4 FIG. 5. FIG. 6.

INVENTOR 0664/?! 5 E N/)( 0/1/ ATTORNEY Dec. 13, 1960 c. E. NIXON CORE WRAPPING METHOD AND APPARATUS Filed Sept. 2, 1954 5 Sheets-Sheet 5 ATTORNEY United States Patent CORE WRAPPING METHOD AND APPARATUS Charles E. Nixon, Sayville, N.Y., assignor, by mesne assignments, to Inso Electronic Products, Inc, New York, N.Y., a corporation of New Jersey Filed Sept. 2, 1954, Ser. No. 453,758

17 Claims. (Cl. 57-17) The present invention relates to method and apparatus for wrapping strips or tapes about a core to form a covering layer and relates more particularly to method and apparatus for helically wrapping tapes around a core with the tension in each tape independently and accurately controllable and with the positions of the various tapes as they lie on the core precisely controllable.

The method and apparatus disclosed may be employed to Wind a covering layer about a conductor or textile or other type of core, but they are particularly advantageous for use in applying tapes of easily stretched material and for thin, narrow tapes which have a low tensile strength. The method and apparatus are described as being used for helically wrapping plastic insulation tapes of low tensile strength on an electrical conductor to form a continuous insulation layer.

Insulating machines for wrapping insulation tapes on wire generally operate on the principle of feeding the wire through a serving mechanism. The serving mechanism is revolved around the wire, while the tape is fed in from an arm on the serving mechanism to the moving wire to wrap it in a helix on the wire. It is customary to use a tape supply spool mounted on or adjacent the serving mechanism with the tape being payed out from the sup ply spool to the arm. The supply spool slowly rotates with respect to the serving structure as the tape unwinds. In order to control the tension in the tape as it passes the arm it has been customary to brake the rotation of the tape supply spool by means of a felt brake pad or similar brake mounted on or adjacent the serving mechanism and acting between the serving mechanism and the tape supply spool, tending to stop the slow rotation of the supply spool with respect to the serving mechanism. Thus, in such prior machines the braking force acts with respect to the difierential in speed of rotation of the supply spool with respect to the serving mechanism resisting the paying out of the tape and thus tightening it up. This differential speed is quite low, as will be understood from the detail description below, so that wide fluctuations in the braking force occur from moment to moment during operation, since the braking force is in effect, in an un' stable region between static and dynamic operation. Where a friction brake is used it tends alternately to slide and grab, sometimes chattering. Moreover, changes in effective diameter of the tape supply spool as the tape un' winds cause other fluctuations.

In the past, insulation tapes have been made of material, such as fabric or threads, having a relatively high tensile strength. With insulation tapes of such materials this type of braking arrangement described Was acceptable. Any fluctuations in the braking force were simply absorbed by the insulation tape, causing the insulation layer to be more tightly wound at some places on the wire than at others. These variations in the tightness of the insulation were acceptable with such materials.

The various synthetic resin tapes and other plastic tapes which are now available, for example such as unfused polytetrafluorethylene, have extremely desirable electrical insulation properties. Thus thinner insulation layers can now be wound on electrical conductors and yet provide much higher voltage ratings and greatly increased ranges of operating temperature, resulting in considerable savings in space and weight of electrical equipment utilizing conductors insulated with these newer tape materials.

However, these newer materials generally have much lower tensile strength and are far more easily stretched and damaged than any prior common insulation tapes.

When these newer tape materials are wound on a wire in the types of machines using the customary principles discussed above, the tapes are often shredded and broken and even when not visibly damaged, the tapes are usually stretched to an extent to cause large numbers of minute voids, which can be seen in magnification. Such voids allow the penetration of moisture and cause low resistance leakage paths through the insulation, leading to break down of the equipment.

In such prior machines the problems of tape stretch and breakage are serious only a single tape of stretchable plastic is being applied to a wire. When a number of these tapes are wound on at the same time, the results have usually been the wastage of half of the wire and tape, with only very short lengths of minimum standard insulated wire being produced. Moreover, the machines are subject to almost constant stoppage because of tape breakage.

Also, such machines are diflicult to start and stop and usually spoil the insulation as they speed up and slow down.

Among the many advantages of the method and apparatus described are those resulting from the fact that the tensions in the tapes as they are applied are independently, accurately, and continuously controllable over wide ranges. The tensions in the different tapes can all be set at the same value or each at a different value. All of the tensions, irrespective of their setting, can be gradual ly increased or decreased together. Adjustments in tension can be made at any time during the operation of the machine.

Another advantage of the apparatus described is that the tension in the conductor being insulated is readily and accurately controlled, and the rate of feed of the conductor with respect to the speed of wrapping is readily adjusted.

A further advantage is that the tension control force for every tape supply spool is applied independently of its diflerential speed with respect to the revolving serving structure.

Another advantage of the apparatus described is that the tension control force is applied as a controllable torque, whose value is independent of speed of rotation. With the automatic control described the apparatus can be started from a dead stop automatically accelerated at a fast rate to at least 2000 r.p.m., held at this speed as long as desired, and then automatically quickly slowed back to a stop, and the entire length of the resulting insulated wire will have a highly desirable uniform smooth layer of insulation material. Even when narrow tapes of unfused polytetrafluorethylene are used, the resulting insulated wire is of such uniformly good quality that no visible or electrical test of the insulation will determine which portions were produced at constant speed and which were produced during rapid changes in speed of operation.

The result is a large saving in time and materials and the production of hundreds of feet of wire insulated with unfused polytetrafluorethylene tape or any other easily stretched tape, whereas previously only relatively short lengths of such insulated wire were produced.

The various features, aspects and advantages of the present invention will be more fully understood from the following description considered in conjunction with the accompanying drawings illustrating an embodiment of the present invention, in which:

Figure 1 is a perspective view of a conductor insulating machine with a small portion shown broken away for better illustration; 7 a e V Figure 2 is a skeletonized perspective view, partially diagrammatic and on an enlarged scale showing portions of the operating mechanism of the machine of Figure 1;

Figure 3 isan axial sectional view on further enlarged scale showing the turntable serving apparatus and" the tape supply spools and concentric bearing and tension control members;

Figure 4 is an axial'sectional view taken along the line 4+4 in Figure 3 showing one of the guide: tube members located near the periphery of the turntable;

Figure 5 is an exploded perspective view as seen from above-showing details of the concentric tape spoolsupporting bearing and tension control members shown in the center of Figure 3; p

Figure 6 is an exploded perspective view of the members shown in Figure 5 as seen from below;

Figure 7 is a schematic and diagrammatic drawing of the control circuits and associated parts of the machine;

Figure 8 is an enlarged cross sectional view of one of several similar small ball bearing units; and I Figure 9 is a diagram for purposes of explanation, il-

lustrating the angular relationships between the wire and each of the insulating tapes.

As shown in Figures 1 and 2, the bare conductor 10, is unwound from a reel 12 controlled by an electric motor 14, in the base portion 16 of the machine. The reel is located close behind a panel door 18 with a handle 20 so that the reel can be conveniently replaced with a full reel from time to time. The conductor passes successively around pulleys 22 and 24 and is pulled up by a capstan wheel 25 through a hollow shaft 26 rotatably supported by a pair of bearings 28. The capstan 25 is supported on'a frame 30 at the top of the machine and is driven by a drive shaft 32. 7

As shown in detail in Figure 3, a turntable serving apparatus, generally indicated at 34, including a turntable 35 is fastened by a set screw 36 near the upper end of the rotatable shaft 26. A main drive motor 38 rotates the shaft 26 and turntable apparatus 34 in the direction shown by means of a V-belt 40 and'a pulley wheel 42 on the shaft 26. a 7

As the bare conductor 10 is pulled up through the serving apparatus 34, three separate insulation tapes 44, 46, and 48 are led upwardly from three supply spools 49, 50

and 51 through three individual tubular guide members.

52, 53 and 54 which are spaced symmetrically around the turntable 35 near its rim and revolve around the conductor 10. These tapes feed in and up to a nose piece assembly, generally indicated at 56, supported on a hollow shank 57 at the center of the turntable 35. The nose piece assembly 56 may, for example, desirably have the form shown in detail and claimed in my copending application Serial No. 453,852, filed September 2, 1954, now U.S. Patent No. 2,910,821, which includes three bent pins 58'and three guide vanes 59 extending up parallel with the insulated conductor 10', as seen in Figure 2. The shank 57 of the nose piece assembly is held in the upper end of the shaft 26 by a set screw 60. As theturntable 35 and the nose piece assembly 56 rotate each of the three tapes is pulled around the pins 58 and then upwardly in the direction of motion of the wire 10' and in across an inner edge of one of the vanes 59 and then wrapped around the conductor to form a uniform insulation layer on the conductor 10, as explained in greater detail in my above copending application.

The insulated conductor 10 continues up past a small guide sheave 61 (see Figure 1) and between another small sheave 62 on the opposite side of the insulated wire 10' and a micrometer 63 which measures the diam- 4 eter of the wire 10' as it passes the sheave 62. The wire 10' passes twice around the capstan wheel 25 and over a pulley wheel 64 on the upper frame 30 then back down through a hole 66 in the top panel 68 of the base 16. The insulated conductor is wound up on a reel 70 turned by a motor 14a, which is identical with the motor 14, for reasons discussed in detail below.

The capstan 25 is V driven from the main motor 38 through a speed control mechanism generally indicated at 72, in Figure 2, which enables adjustment of the relative rate at which the conductor lfi is pulled through the turntable 35 with respect to the speed of rotation of the turntable, to control the amount of insulation wound on a given length of insulated conductor 10".

As explained in detail hereinafter, automatic speed control means are provided for the motor 38 so that both the rate of feeding of the conductor 10 and the rotational speed of the turntable 35 can be correspondingly changed, for example in starting and stopping the machine and in regulating the production rate.

In order to enable independent control of the tension in each of the tapes 44, 46, and 48 as they feed up through their respective guide tubes and in to the nose piece assembly 56, the tapes 44, 46, and 48 are payed out from three independently rotatable tape supply spools 49, 50 and 51, respectively, which'are concentric with each other and with the shaft 26.

As shown most clearly in Figure 3, each of these tape supply spools is secured to an individual bearing and tension control member 74, 76, or 78, respectively. These control members are concentric with eachother and with the shaft 26 and the conductor 15!. Each control member 74, 76, or 78 is freely rotatable with respect to the shaft 26 and with respect to the serving mechanism 34.

In order to control the tension in each of the tapes 44,

46, and 48 as they payout from the supply spools to their respective guide members 52, 53, and 54, grooved flanges 80, 82, and 84 are provided at the lower ends of the members 74, 76 and 78, respectively. Three small round belts 86, 88, and each connect respective ones of these control members 74, 76 or 78 to a small electric motor 92, 94, or 96. When the machine is in operation these motors are used as generators to place a constant braking torque on the spools 49, 5t) and 51, as explained in detail hereinafter. Referring to the spool 49 and its control member 74 in greater detail, the spool 49 may be formed of a transparent plastic material, such as Plexiglas with a hub portion and a pair of wide flanges spaced apart slightly farther than the width of the tape. The hub is fastened to the top, end of the cylindrical metal body of the control member 74 which has a bore :of slightly larger diameter than the outside of the shaft 26. Three small ball bearing units 104 are equally spaced around the top and bottom ends of the cylinder 100, and rotatably support the member 74 around the shaft 26.

Each ball bearing unit includes an inner race held by a machine screw 166 onto the cylinder 180 and anouter race whose rim runs on the outer surface of the shaft 26. The lower end of the cylinder 100. has the flange 80 with a groove 108 engaging the belt 86. p

In order to support the bearing and control members 74, 76, and 78, on the shaft 26, .a conical bearing surface 110 is provided on the rim 89 adjacent the groove 108. A collar 112 held by four'set screws 114 on the shaft 2'5 has three larger ball bearing units 116 mounted at an angle to run on the bearing surface 110'. c

The spool 50 is similar to the spool 49 with its. hub portion fastened to the upper end of the cylindrical body 118 of, the control member 76' which has a bore 128 slightly larger than the outside. of the cylinder 109, as seen in Figure 3.

Six equally spaced slots 122 (see Figure 5) are cut in the top ofthe cylinder 118 to carry six ball bearing units 124 and 126 in alternate inner and outer positions and all similar to the units 104 and similarly held by machine screws 106. The three units 124 have their rims projecting slightly into the bore so as to run on the outer surface of the cylinder 100; whereas the three alternate units 126 have their rims projecting beyond the outer surface of the cylinder 11-5 to support the upper end of the control member 78 around the cylinder 118, as seen best in Figure 3.

At the lower end of the cylinder 118, as seen in Figure 6, are three more ball bearing units 124 with their rims projecting slightly into the bore 120 to roll on the outer surface of the cylinder 100. An annular recess 127 is formed in the upper surface of the flange 80 to provide clearance for the three lower bearing units 124. Three equally spaced slots 12S carry three more ball bearing units 126 with their rims extending out beyond the outer surface of the cylinder 118 and above the flange 82 so as to support the lower end of the outer control member 78 around the cylinder 118, as seen in Figure 3.

The lower end of the cylinder 118 has the flange 82 with a groove 130 engaging the belt 88. A conical bearing surface 132 is provided on the flange 82 to engage three ball bearing units 134 secured at equally spaced points around the flange 80 thus supporting the control members 76 and 78. These bearing units 134 may also be similar to the units 104.

The spool 51 is generally similar to the spools 49 and 50 and is fastened to the upper end of the cylindrical portion 136 of the control member 78. At the lower end of the cylinder 136 is the flange 84 with a groove 137 engaging the tape tension control belt 90. A conical bearing surface 138 is provided at the lower end of the cylinder 136 to ride on three ball bearing units 140 equally spaced around the upper surface of the flange 82. The ball bearing units 140 may be generally similar to the units 104 described above.

With this bearing arrangement as described, all of the supply spools 49, 50 and 51, are independently rotatably supported in concentric relationship with the shaft 26. Moreover, the belts 86, 88 and 90 running in their respective grooves on the flanges at the lower ends of the control members 74, 76 and 78 provide easy means for applying the desired amount of torque to these control members to tension the tapes 44, 46 and 48 as they pay out from the supply spools 49, 50 and 51. The belts 86, 88 and 90 run around small pulley wheels 142, 143, and 144 on the shfits of the small motors 92, 94 and 96, respectively. These belts are held taut by spring biased pulley wheels 148.

Another advantage of the arrangement of the bearings is that the conical surfaces 110, 132 and 138 are arranged at a 45 angle, which helps to position accurately the control members 74, 76 and 78 in concentric relationship with each other.

A further advantage of the independent concentric arrangement of the tape supply spools and their control members is that the motions of the various spools is not directly compared to the turntable speed by any coupling mechanism such as the tension control brakes used in prior machines, as described above.

Among the advantages of using the small individual bearing units 104, 124, 126, 134 and 140 is that any friction is very eflectively minimized. These bearing units (see Figure 8) have their small balls 139 located in races closely adjacent the central hole 105 for the machine screw 106, and the relatively larger diameter of the outer rim 141 of the ball bearing units provides considerable leverage for the rolling surfaces, further minimizing any slight friction effects due to rolling friction of the balls 139.

With the construction shown I have found that the supply spools 49, 50, 51, all operate substantially without any frictional drag upon each other, for example, even when operating in different directions at different rates of speed. It is to be understood that other antifriction bearing arrangements may be used in order to allow all of the tape supply spools 49, 50, and 51 and the control members 74, 76 and 78 to rotate independently of each other and of the turntable and yet to enable independent control of the rotation of each spool.

In Figure 9 is shown a diagram which will be used in connection with a discussion of the differential in speed between the turntable 35 and the supply spools 49, 50 and 51. This diagram relates the mean distance D around the conductor 10 which is covered by any one of the insu lation tapes during one revolution of the turntable serving apparatus, with the length L of the conductor 10 which passes through the head assembly 56 during one revolution of the turntable 35, with the total un-overlapped width W of tape wound onto the conductor during each revolution of the turntable and with the amount A of tape which is helically wrapped on the conductor during each revolution of the turntable 35. I

For example, assume that the conductor 10 has a diameter of 60 mils and that each of the tapes 44, 46 and 48 of unfused polytetrafluorethylene is 4 mils thick and is 716 of an inch in width. Also assume that each tape is being wound on the conductor 10 so that approximately two-thirds of each tape overlaps one or both of the preceding tapes as shown in my copending application, identified above. This makes the insulation 12 mils thick before fusing. Thus, the mean distance D around the conductor is 7211 mils or 226 mils. The sum of the un-overlapped tape widths is fi of an inch or 187 mils. The angle 0 at which the tape is Wound with respect to the axis of the conductor 10 is cos- (187/226)=34.1. The length L is thus 226 ctn (34.l)=334 mils, and the amount A of each tape wound on the conductor during each revolution is 226/sin 34.1:403 mils.

With the precise control provided by the present method and apparatus, there is substantially no stretch in the tapes 44, 46 and 48. Thus, approximately 403 mils of tape pays out from each spool during each rotation of the turntable.

Assuming that the machine is operating at 1000 r.p.m., and that each of the spools 49, 50 and 51 has an over-all diameter of 10 inches and is full, then each of the spools is rotated by about .0128 of a turn for each revolution of the turntable 35. Thus, the spools 49, 50 and 51, are

rotating at about 12.8 r.p.m. with respect to the turntable 35. Depending upon the direction in which the tapes were wound on the spools, they either travel 12.8 r.p.m. faster or slower than the turntable 35. In the machine, as shown, the spools 49, 50 and 51 travel faster than the turntable at 1012.8 r.p.m. with respect to the machine frame.

As the tapes unwind, the effective diameter of the rolls of tape in the spools 49, 50 and 51 decreases and so their differential in speed increases. For example, assuming that the diameter of the hubs of the spools is 4 inches,

then when they are almost unwound the difierential in speed rises to 32 r.p.m. This is a 250% change in the differential speed.

On the other hand, the absolute speed has risen only to 1032 r.p.m. with respect to the machine frame, a 1.9%

unwinding of the tape.

In prior machines which apply the braking force between the revolving serving apparatus itself and the tape supply spool, the low difierential speed sometimes causes the braking apparatus periodically to stick and then jump,

causing wide tension variations. It is seen that in prior machines thetension is also subject to large, variations due to the unwinding of the spool and the consequent large amountofincrease in difierential speed which in addition,maycausechanges in the running character-' istics.

Moreover, the reduction in the effective diameter of rolls of tape on the supply spools as it unwinds has the efiect of reducing the leverage arms of the taps in turning the spools 49, 50 and 51 about their axes. In the example discussed above the leverage arm drops to .4 of its initial value. The result in prior machines is a further increase in the tensions to which the tapes are subjected.

' In the present machine, this same change in leverage arm takes-place, but it occurs without any substantial change in thespeed of rotations of the spools with respect to the external tension controlling motors 92, 94 and 96. Moreover, an advantage of the method and apparatus disclosed herein is that the'tension control operates in such a way that this change in leverage has no significant effects, or it may be compensated for simply by changing the constant torque-braking force applied by the motors 92, 94 and 96 through the belts 86, 88 and 90.

To accommodate the different heights of the supply spools 49, 50 and 51, the tubular guide members 52,53 and 54 project down different distances below the turntable 35, as indicated in phantom in Figure 3. The lower ends of these tubular guides are cut off at an angle of 45 to provide clearance for the tapes to enter. Each guide. includes lower and upper rollers 145 and 146, with the axes. of each lower roller 145 turned slightly so as to face it in the direction from which the tape pays out from the respective tape supply spools when they are about half full, i.e. to face the mean radius of the tape winding. The upper rollers 146 are'held in short sleeves 147 and can be turned at any desired angle with respect to the turntable 35, depending upon the shape of the nose piece assembly 56 being used and the relative positions of the pins 58..

Another advantage of the arrangement disclosed is that the control motors 92, 94 and 96 are used to turn the tape spools to wind them up. As illustrated diagrammatically on reduced scale at the right in Figure 3, a bobbin 148 of newtape is placed on one of the three pins 150 near one side of the top panel of the machine and the tape is wound onto the corresponding spool. All three spools can be wound at once by using three bobbinsg'each bobbin is preferably held at adifierent height.

The power for driving the capstan wheel- 25 is coupled from anadjustable pulley 151 on the lower end of the shaft of the main motor 38, through a V-belt 152 to a pulley 154 on a shaft 156 carried on a carriage 158 slidingly supported on apair of rods 160 secured to the frame of the machine.

In order to slow the speed of the capstan wheel 25 with respect to the turntable 35, a hand wheel 162 on the front of the machine is turned clockwise, rotating a screw 164 and moving the carriage 158 along the rods 160 toward the hand wheel 162. The belt 152 becomes tightened and slides down deeper into the adjustable pulley 151, thus reducing the effective diameter of this pulley. At the same time, the motion of the carriage moves, another adjustable pulley 166 on the upper end of the shaft 156 further from a pulley 168 on the lower end of the shaft 32, tightening up a V-belt 170 extending between them and causing it to slide down further into the adjustable pulley 166, reducing its elfective diameter. Thus, the unit 72 reduces the effective diameters of each of the driving pulleys 151 and 166 with. respect to the driven pulleys 154- and 168, respectively and thus slows down the'shaft 3'2 with respect to the turntable. As shown in Figure 1 the top end of the shaft 32 carries a cone gear 168 engaging another cone gear 170 connected to a worm-drive speed reducing unit 172 coupled to the shaft of the capstan wheel 25.

Turning the hand wheel 162 in the opposite direction enlargesthe efiective diameters of the respective driving pulley 151 and 166 and thus speeds up the capstan wheel 25 with respect to the speed of the turntable 35.

Shown within the outlined area 174' at the lower left of Figure 7 is the automatic speed change mechanism for the machine as a whole. This includes '2: Ward- Leonard motor-generator system with an induction motor 176 connected by leads 178' to a pair of alternating current power lines 180 on the machine. The motor 176 is connected by a shaft with a direct current generator 182 connected by leads 184 to the main drive motor 38 which is a DC. motor. The field winding 186 of the generator 182 is energized from the lines 180 through a bridge" rectifier 188 having its output connected across a potentiometer 190. One end of 'the field 186 is connected to one side of the potentiometer 190 and the other side is. connected to a movable contact 192 on the potentiometer. A reversible series A.C. motor 194 is connected through a worm-gear speed reducing unit 196 to the movable contact 192. The motor 194 has its field 198 and armature connected to the A.C. lines 180 through a double-pole double-throw reversing switch 200 shown at the right of the instrument panel of the machine adjacent an indicator 202 which shows the r.p.m. of the main drive motor 38' and also by a suitable conversion factor shows the speed of the turntable 35. When the switch 200 is thrown to its Fast position (the up position in Figure l), the motor 194 drives the movable contact 192 slowly around the rheostat 190 so as to increase the voltage applied to the field winding 186 of the generator 182'. The gear ratio in the unit 196 is such that it takes about one minute for the movable contact 192 to move from the left end of the rheostat 190 to the right end, speeding up the motor 38 so as to accelerate the turntable from zero to about 2,000 r.p.m. Throwing the switch 200 to its slow position gradually slows down the machine. The speed indicator 202 can be a voltmeter movement connected to a small D.C. generator 203 mounted on the panel 68' (see Figure l) driven by the motor shaft and arranged to have an output voltage which linearly increases with speed.

In order to control the tension throughout the length of the conductor 10 between the reels 12 and 70, the identical D.C. shunt motors 14 and 14a are used with their field windings 204 and 204a, respectively connected in parallel by leads 206 and energized from a bridge rectifier 208 connected to 'the A.C. lines 180. Thus, full rated DC. voltage is continuously applied to both of the fields 204 and 20411 when the machine is on. The arma- .turcs of these meters 14 and 14a are connected in series by a lead 210 and are both connected across a bridge rectifier 212 by the leads 214 and 216. The bridge rectifier '212'is energized by an adjustable A.C. voltage from a variable reactor 217 having a sliding contact 218', adjustable by a conduct'ortension control knob 219 at the rear of the top panel. 68.

The motors 14 and 14a are both arranged to drive their respective reels 12 and 70 in such directions that they both tend to wind up the conductor 10 and thus tension it between the reels 12 and 70. The amount of tension is quickly and easily adjusted by moving the contact 218 of the variable voltage control 217' so as to change the armature currents in these motors. Since the motors 14. and 14a are identical, the opposed forces on opposite ends of the conductor 10 are always substantially equal, irrespective of the motion of the conductor 10, and thus the tensions along the conductor are the same at all points varying only with changes in the diameter of the wire wound on the reels 12 and 70.

The capstan wheel 25' is subjected to no net force from the motors 14 and 14a irrespective of the speed or tension of the conductor. This arrangement has proven quite advantageous, for it enables independent adjustments of the conductor tension and of the capstan speed, regulated 9, by the unit 72, and also assures uniform tension all along the length of the conductor 10.

In order to regulate the tape tension controlling motors 92, 94 and 96, the circuits at the right of Figure 7 are provided. The individual branch circuits I, II and III for these three motors are identical, and so corresponding parts are indicated by the same reference numeral. When these motors are being used to control the tensions in the three tapes, they are connected as generators by means of their respective four-pole double-throw switches 230, which are thrown into the left or Tension Position. In the Tension Position, the field windings 232 are connected through individual tape tension equalization potentiometers 234 to a pair of leads 236 connected to the Tension Position contacts of a double-pole doublethrow master switch 238. The movable contacts 239 of the potentiometers 234 are adjusted by the respective control knobs 240 adjacent the motors 92, 94, and 96 on the top panel 68. With the master switch 238 in its Tension Position, the leads 236 are connected across a voltmeter 242 at the left of the instrument panel of the machine to the output of another bridge rectifier 244, which is energized from a variable reactor 245. This variable reactor is connected from the secondary 246 of step-down transformer 248 having its primary 250 connected to the AC. lines 180. The movable contact 252 of the variable voltage control 245 is adjusted by the knob 254 on the instrument panel to regulate the D.C. voltage available on the leads 236 as indicated by the meter 242, thus regulating the currents in the field windings 232, and hence regulating the amount of field flux in the motors 92, 94 and 96 and so the torque required to turn their armatures when they are operating as generators.

During operation at the normal turntable speed of about 1,000 r.p.m., the armatures 256 of the motors 92, 94 and 96 are driven at a fairly high rate of speed by the belts 86, 88 and 90. Each of these armatures is connected through an ammeter 258 and through the switch 230 to a variable load resistor 260, which is used as an individual tape tension control. The movable contacts of the variable resistors 260 are adjusted by the control knobs 262 on the instrument panel beneath the dials of the respective ammeters 258; The current generated by the armatures 256 is dissipated in the variable load resistors 260, thus causing a braking torque to be exerted by the pulley wheels 142, 143 and 144 on the respective belts 86, 88 and 90.

In adjusting the machine for the operation of wrapping a core, the individual tape tension equalization knobs 240 are adjusted so that the voltages applied to the individual fields 232 produce equal currents in the armatures 256 when the individual tape tension control knobs 262 have identical settings. Once the knobs 240 have been adjusted, any slight actual differences in characteristics of the motors 92, 94, and 96 are compensated for, and usually the knobs 240 need not be adjusted again. With the motors 92, 94 and 96 all equalized for generator action, the magnitudes of the currents through the meters 258 is an accurate measure of the torque being applied by these motors to the respective control members 74, 76 and 78. The individual tape tensions can be set at a wide range of different values, as may be desired, by adjusting the individual load resistors 260. All of these tensions can be simultaneously increased or decreased by varying the amount of field voltage by using the knob 254 on the master tape tension control 245.

Among the many advantages of this arrangement is that the motors 92, 94 and 96 when used as generators provide an easily adjusted constant torque, which is a linear function of speed, being the combined result of the field flux in the motors and of the respective armature currents. The field flux is adjusted by the setting of the contact 252, while the armature current is a function of generated E.M.F., which is proportional to speed.

In order to rewind the spools 49, 50 and 51, the individual switches 230 and the master switch 238 are thrown to the Rewind Position (the right position in Figure 7 or the rear position as seen in Figure 1). This energizes the field windings 232 with fixed D.C. voltage through leads 263 from a bridge rectifier 264 connected to the secondary 246. In the rewind position, the armatures are connected to the leads 236 so that the applied voltage and hence their speeds of rewind can be adjusted by the knob 254, as desired. In rewind operation, the master tape tension control 245 becomes a master rewind speed control, and the potentiometers 234 may act as individual speed controls if desired.

I have found that small D.C. shunt motors, for example such as those made by John Oster Manufacturing Corporation of Genoa, Illinois, Type BT-2-l5, having a rating of 28 volts, 1.1 amperes, and providing 1 ounceinch of torque are well suited to provide the braking torque desired on the control members 74, 76 and 78. By selecting the ratios of the diameters of the pulleys 142, 143 and 144 on the motor shafts and the diameters of the grooves in the flanges of the control members 74, 76 and 78, the motors 92, 94 and 96 can be arranged to provide 1 ounce-inch of torque on the tape spools when the spools are half full. Thus, the ammeters 258 may be read directly in ounce-inches of braking torque as a function of amperes.

Other braking torque devices can be used, for example such as eddy current brakes of the kind found in wattmeters, but provided with electromagnets instead of fixed magnets to enable adjustment or provided with viscosity friction braking devices, or the like. However, I find that the motor-generator type of tension control unit, such as the Oster motors described, are quite satisfactory for most applications for they have the additional advantage of providing an easy means of rewinding the tape spools. When desired a small portable electric motor with a rubber-tired wheel on its shaft that can be held against the flanges of the supply spools is used to wind on the tape.

The power for the machine is supplied from 60 cycle AC. power mains 270 through a main switch 272 associated with a pair of fuses 274 and a suitable on-off indicator lamp '276 connected across the lines in the machine.

In the method of the present invention, as embodied in the machine described, the core to be wrapped is fed along a path, and the strip or strips to be wrapped on the core are unwound from a concentric relationship with this path and are fed out to points spaced from the path and revolving around the path of the core and are then fed back in toward the path and are helically wrapped around the core, while a braking torque independent of the motion of the revolving points is applied to the strip or strips as they are in their concentric relationship with respect to the path of the core.

More broadly the method of the present invention includes the steps of feeding a core to be wrapped along a path, feeding the strip to be wrapped on the core to a point which is spaced from the path and which is revolving around the path and applying a tension force to the strip before it reaches said point this tension force being independent of the motion of said point, and feeding the strip in to said path and wrapping it helically on the core.

From the foregoing description it will be understood that the present invention is well adapted to accomplish the ends and objects set forth and to provide the advantages described and that the method and apparatus of the invention may be subject to various modifications each as may best suit the method and apparatus to a particular application and that the scope of my invention includes such modifications.

I claim:

l. The method of helically wrapping a plurality of strips around a'core, comprising the steps: of feeding .the core along, a path fixed inv position with respect to' a fixedv and stationary referenceelemeut, providing supply spools of'equaldiameter in concentric relationship with said path for supplying said strips, unwinding the strips from respective ones of said: spools. in concentric relationship with said path, feeding the strips out to points. spaced from said path and revolvin'g'around said path, feeding the strips from said points in to the path, wrapping the strips around the core, and applying individual controlling torques to. eachxof the spools as the strips unwind from their concentric relationship with said path, said controlling torques being applied directly from torque exterting means mounted on said fixed and stationary reference element to each of said spools to control the rate of rotationof each of said spools with respect to its torque exerting means.

2; Apparatusffor helically wrapping a core with a tape comprising a fixed and stationary machine frame, means on said fixed and stationaryframe defining a path for said core, core tensioning and moving means for tensioning said core in said 'path and moving it along said path, a first tape guide spaced out from said path and mounted on said fixed and stationary frame to revolve around said path, revolving drive means coupled to said first guide for revolving it around said path, a second tape guide closely adjacent said path, a tape supply spool rotatably mounted on said fixed and stationary frame concentric with said'path to rotate independently of the motion of said first guide, the tape on' said spool unwinding and paying out to said first guide and from. said first guide to said second guide and then being wrapped around said core in said path, and an adjustable tape tensioning mechanism having stationary and rotating portions, said stationary portion being rigidly secured to said fixed and stationary frame and said rotating portion being coupled to said'spool, said tape tensioning mechanism applying torque to said spool to tension said tape as it pays out from said spool' 3. Apparatus for wrapping a conductor with a plural,- ity of tapes comprising a machine frame, means on said frame defining a'path for said core, core 'tensioning and moving means for tensioning said core in said path and moving it along said path, a structure rotatably mounted on said frame to rotate concentric with said path, a plurality of first tape guides on said structure and spaced out from said path to revolve around said path, drive means for rotating said structure, a second tape guide with portions spaced around said path, a plurality of tape supply spools rotatably mounted on said machine frame, each of said spools rotatable independently of any other spool and independently of said structure and each being adapted to carry at least one tape, said spools being arranged to pay out the tapes to respective ones of said first guides, said first guides being arranged to feed the tapes to said second guide and to Wrap the tapes around the core, and a plurality of controllable torque-exerting devices'mounted on said frame and each coupled to one of said spools.

4. Apparatus for wrapping tapes around a core comprising a machine frame, a hollow drive shaft rotatably supported on said frame, drive means connected to rotate said shaft, core tensioning and feeding means for feeding the core along a path through said drive shaft, a plurality of tape guiding members secured to said shaft and spaced out from said path to revolve around said path as the shaft is rotated, a plurality of tape supply spools concentric with said shaft, bearing means supporting each of said spools to rotate freely with respect to said shaft and with respect to said guiding members, a plurality of electric motors on said frame each coupled to one of said spools, and a plurality of controls for regulating the current in said motors to regulate the tension in each of said tapes as they pay out from their respective spools.

' 5. Apparatus for wrapping, tapes around a core com- 12 prising a machineframe, a hollow drive shaft rotatably supported on said frame, drive means connected to rotate said shaft, core; tensioning and feeding" meansfor feeding. the core along arpaththrough said drive shaft, a plurality. of tape guiding'ielements secured to said shaft and spaced" outfrorn: said path to. revolve around said path as. the shaft isirotated, a pluralityjof; tape supply spoolsarranged side by side, and concentric with said shaft and each freely rotatable. with respect to. each other and with nespect to said shaft,a plurality of spool controlmemprising a machine frame, a hollow drive shaft rotatably supported on said frame, drive means connected to rotate said shaft, core tensioning and feeding means for feeding the core along a path'through said drive shaft, a plu rality of'tape guiding elements secured to said shaft and spaced out from. said path to revolve around said path as the shaft is rotated, a plurality of'tape supply spools arranged side. by sidev and concentric with said shaft and each freely rotatable with respect to each other and with respect to said shaft, a plurality of cylindrical spool control memberseachi concentric with said shaft and with each other and having first and second respective ends, the inner memberbeing longe'st'and' having its first end connected to an end spool, successive outer members being progressively shorter, each successive outer memher having its firstend connected to a spool successively farther from. said end spool, and a plurality of torque exerting devices each coupled between said frame and one ofthe second ends of said members.

[Apparatus for wrapping tapes around a core as claimedin claim 6 and wherein said torque-exerting devices are electric motors each mounted on the frame and having its rotor connected to. the second end of one of said control members.

8. Apparatus for wrapping tapes around a core as claimed in claim 7 and wherein the second end of each successive outer control member is shorter than the second end of the next inner member, and the second ends of all of said members having pulley. grooves and the rotors of respect-iveones of said electric motors are con nected by'belts to said grooves. f

9. Apparatus for helically wrapping a tape around a core comprising a machine frame, tape serving mechanism revolvably mounted on the frame, drive means for revolving said mechanism, first and second electric motors each'havingfield and armature windings, first and second core reels respectively coupled thereto, said core being arranged to unwind from said first reel, to pass along a' path through said serving mechanism and to wind up on said second reel, a capstan arranged to move said core along said path, first circuit means connecting said' field windings together, current source means connected to said first circuit means equally to energize said field windings, second circuit means connecting said annature windings together, current source means'conn ected to' said second circuit means equally to energize said armature windingslto urge both of said reels in directions such as to tend r wind up said core, and a current control arranged to regulate the current from one of said current sources to one of said circuit means to regulate the'tension insaid core. 5

10. Apparatus as claimed in claim 9 and wherein said second circuit means connectszsaid armature windings in series and said current control regulates the. current through bothofi said armature windings.

1.1. Apparatus. for wrapping tape. around. a core comprising a machine frame, tape serving mechanism revolvably mounted on said frame,'a main drive motor for revolving said serving mechanism, core guiding means defining a path through said serving mechanism, a core driving wheel, for moving a core along said path, an adjustable speed control power transmission mechanism coupling said Wheel to said main dnive motor, whereby said wheel is driven by said main motor and the speed ratio between said tape serving mechanism and said core driving wheel can be adjusted, and a master speed control connected to said main drive motor for simultaneously controlling the speeds of said tape serving mechanism and said core driving wheel.

12. Apparatus as claimed in claim 11 and wherein said master speed control includes a movable element which can be moved through a range of positions and is arranged to produce a corresponding range in speeds of said main drive motor, and a reversible motor connected to said element to move it in either direction through said range of positions.

13. Apparatus for wrapping insulation tapes around a conductor comprising a machine frame, a vertical hollow drive shaft rotatably supported on said frame, drive means coupled to said shaft to rotate it, a turntable secured to said shaft near its upper end, a plurality of tape guiding elements on said turntable near its edge each adapted to guide a tape from below to above said turntable, a plurality of tape supply spools arranged horizontally side by side below said turntable and concentric with said shaft, a plurality of cylindrical spool control members concentric with said shaft and telescoped within one another, each successive inner member projecting above and below the members therearound, the hub of the top spool being secured near the upper end of the inner member, the hubs of successively lower spools being secured near the upper ends of successive outer members, an abutment on said shaft below the inner member, low friction bearing means between said abutment and the lower end of said inner member and between said shaft and the inside of said member, a flange on the lower end of each member which is surrounded by another member, low friction bearing means between each of said flanges and the next outer member and between the outside of each member and the inside of the next member, whereby all of said members and their respective spools are freely rotatable about said shaft with respect to each other, and a plurality of controllable electric motors on said frame coupled to said flanges.

14. Apparatus for wrapping insulation tape around a conductor comprising a machine frame, tape serving mechanism revolvably mounted on said frame, a main drive direct current motor, a first drive connection between said motor and said serving mechanism for revol ing said serving mechanism, means defining a path for said conductor through said serving mechanism, a capstan wheel adapted to engage a conductor in said path, a second drive connection between said wheel and said motor for moving said conductor along a path, a source of alternating current, an alternating current motor connected thereto, a DO. generator having its armature mechanically connected to the rotor of said AC. motor and being electrically connected to said main motor, a source of direct current, a rheostat, the field of said generator being connected to said source through said rheostat, and a reversible motor connected to said rheostat and arranged to vary its resistance to change the speed of said main motor.

15. Apparatus for helically wrapping a plurality of insulation tapes around an electrical conductor while accurately controlling the tension in each tape comprising a machine frame, means on the machine frame defining a path for the conductor, tensioning and driving mechanism for moving the conductor along said path, a plurality of revolving tape supply spools concentric with said path, a revolving serving mechanism concentric with said path and having a plurality of tape-guiding elements spaced from said path, revolving drive mechanism for revolving said serving mechanism, the tape from each of said spools being adapted to unwind from its spool, pass its respective tape-guiding element, and then to approach said path and wind around the electrical conductor passing therealong as the serving mechanism is revolved, and tape tension controlling mechanism for each of said spools including a revolving member coupled to each spool and revolving therewith and a member fixed on the machine frame co-operating with said revolving members for applying accurate tension controlling torques between the fixed machine frame and each of said revolving spools.

16. Apparatus for wrapping a plurality of insulation tapes around an electrical conductor while accurately controlling the tension in each tape comprising a machine frame, conductor supporting means on the machine frame supporting the conductor for movement along a path through the machine, a plurality of revolving tape supplies concentric with the path of the conductor, said tape supplies being revolvably supported for revolution independently one from another, a revolving serving mechanism concentric with said path and including a plu rality of tape-guiding elements spaced from said path, revolving drive mechanism for revolving said serving mechanism, said tape supplies being revolvably supported for revolution independently of the serving mechanism, the tape being adapted to unwind from each of said supplies and to pass its respective revolving tape-guiding element and then to approach said path and wind around the electrical conductor passing along said path as the serving mechanism is revolved, and tape-tension-controlling mechanism for each of said tapes including a member coupled to each of said tape supplies and revolving therewith, a stationary member, and adjustable torquecontrolling means operatively associated with said stationary member and said revolving members for applying accurate tension-controlling torques between the fixed machine frame and each of said revolving tape supplies.

17. Apparatus for helically wrapping a plurality of insulation tapes around an electrical conductor while accurately controlling the tension in each tape comprising a fixed and stationary machine frame, conductorguiding means on the machine frame adapted to guide the conductor along a path through the machine, a revolving serving mechanism concentric with said path and having a plurality of tape-guiding elements spaced from said path, revolving drive mechanism for revolving said serving mechanism, a plurality of tape supply spools of the same diameter adapted to have tape wound thereon concentric with said path, each of said tape supply spools being rotatably supported for rotation independent one from another and independent of the movement of said serving mechanism, the tape from each of said spools being adapted to unwind from its spool and to be guided by its respective tape-guiding element so as to wind around the electrical conductor passing along said path as the serving mechanism is revolved, and tape tension controlling mechanism for each of said spools including a member held stationary with respect to the fixed and stationary machine frame, and tension-controlling torque-exerting means acting from said stationary member to each of said tape supply spools for providing accurate tension-controlling torques individually to each of said tape supply spools, said torque-exerting means being operatively interposed between said stationary member and each of said tape supply spools for controlling the rate of rotation of each of said spools with respect to said stationary member, whereby the tension of each tape is accurately controlled as it unwinds from its spool and winds around the electrical conductor.

(References on following page) Refe l enges Cited in the, file of this patent UNITED STATES PATENTS Kruesi et a1. Jan. 19, 1886 16? EampnQ- t; a1 '.'.,,June, 4, 19.35 Henning'et a1. -7 Aug. 10, 19,43v Bouge t De 28, 19 48 Bouget L. Feb. 22, 1949 Spillmap 1, 1949 Olson et a1. Feb. '19 1 957

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