US3677054A - Method of forming a double torsion spring and machine therefor - Google Patents

Abstract

A wire forming machine and method wherein a length of wire is cut and provided with a bow-shape at a coiling station by forming jaws moving relative to a forming arbor and with a pair of wire legs lying to either side of a stationary element at the coiling station. Right and left tool slides each carry a rotatable coiling head which is advanced into engagement with the wire legs and with catch pins on the coiling heads engaging and holding the wire whereby rotation of the coiling heads will form coils in each of the wire legs. The central bowed wire base is free to advance toward the coiling heads while being restrained against rotation whereby the lengths of wire to form the coils are provided by the advancing wire base, rather than by shortening of the free ends of the wire legs.

Description

United States Patent Strzepek 1 July 18,1972

[54] METHOD OF FORMING A DOUBLE TORSION SPRING AND MACHINE THEREFOR Edward S. Strzepek, Cicero, lll.

Assignee: Lewis Spring & Manufacturing Co.

Filed: June 23, 1970 Appl. No.: 49,075

Inventor:

Field of Search ..140/102, 103, 104, 92; 72/129, 72/130,l31,l33,135,137,142

[56] References Cited UNITED STATES PATENTS 237,397 2/1881 Lewthwaite ..l40/l03 3,227,195 1/1966 Stegmann 140/103 Primary Examiner-Lowell A. Larson Attorney-Hofgren, Wegner, Allen, Stellman & McCord [57] ABSTRACT A wire forming machine and method wherein a length of wire is cut and provided with a bow-shape at a coiling station by forming jaws moving relative to a forming arbor and with a pair of wire legs lying to either side of a stationary element at the coiling station. Right and left tool slides each carry a rotatable coiling head which is advanced into engagement with the wire legs and with catch pins on the coiling heads engaging and holding the wire whereby rotation of the coiling heads will form coils in each of the wire legs. The central bowed wire base is free to advance toward the coiling heads while being restrained against rotation whereby the lengths of wire to form the coils are provided by the advancing wire base, rather than by shortening of the free ends of the wire legs.

14 Claims, 8 Drawing Figures fff fjjjflijli- I: IYIQILKKJ lllllllllllllllllllllllllllllllllllllllllllllllllli PATENTED JUL] 8 I972 SHEET 1 UF 3 PATENTED JUL] 81972 SHEET 2 (IF 3 METHOD OF FORMING A DOUBLE TORSION SPRING AND MACHINE THEREFOR BACKGROUND OF THE INVENTION This invention pertains to wire forming machines and tooling therefor to form double torsion springs, along with a new and improved method of forming such springs without the performance of secondary operations in plural machines and with the number of coils formed in the torsion spring not being limited by the free ends of the wire legs, since said free ends are not caused to shorten during the coiling operation. This results in not having long lengths of wire rotated during the coiling operation.

It is known in the prior art to form double torsion springs by first forming a wire length into a U-shape with a wire base and a pair of legs, commonly called a staple, and then individually placing these staples in a kick press along with a coiling adapter slipped onto the arbor of the kick press, followed by rotation of the arbor to form the coils and with the wire being pulled around the arbor from the free ends of the wire legs. Another known system utilizing a four-slide machine is to cut off a length of wire and from it into a U-shape, followed by coiling of the legs, with the lengths of wire for the coils being provided by shortening of the free ends of the wire legs during coiling.

In the first of these known systems, two successive operations, in different machines, are required, with the mounting and removal of an adapter in forming each spring. In the second known system, utilizing a four-slide machine, there are definite limitations, since the number of coils to be made are limited by the amount of wire in the legs which is free to rotate during the coiling operation without obstruction with the surrounding parts of the machine. This limits the number of coils to be formed to a length of the free wire legs which will still not be obstructed by the machine as the free ends rotate during the coiling operation.

SUMMARY OF THE INVENTION An object of this invention is to provide a new and improved method of forming double torsion springs wherein the number of coils are not limited by the amount of wire in the wire legs that can freely rotate in the coiling operation, but wherein the number of coils are theoretically unlimited since the free ends of the wire legs do not change in length during coiling but the wire for coiling is provided by permitting the base of the U- shaped wire to advance without rotation during coiling.

Another object of the invention is to provide a machine and tooling therefor for forming double torsion springs wherein at a coiling station a forming arbor in a lower position coacts with forming jaws on a front slide to form a bow in a length of wire to have the wire U-shaped, with a pair of legs extending from a central wire base, the forming arbor being movable to an upper position to subsequently permit advance of the wire base during coiling to provide wire for the coils, a pair of right and left tool slides each carrying a rotatable coiling head with a catch pin which can be advanced into engagement with the wire legs with rotation thereof causing forming of the coils in each of the legs as the wire base advances theretoward, and with a stationary element having horizontal surfaces engaging the wire between the base thereof and the coiling engagement thereof by the catch pins to permit advance of the wire base while preventing rotation thereof.

Still other objects of the invention are to provide a wire forming machine and tooling as defined in the preceding paragraph wherein the right and left tool slides carry abutments engageable with the jaws on the front slide for forming a smooth curve at the wire base, the coiling heads are rotated by rack drives operated from the rear slide cam of the machine through racks interconnected by a bridge and with the racks slidable thereon to permit movement of the coiling heads toward and away from each other while maintaining the rack and pinion drive to the coiling heads, the provision of a coiling arbor on oneof the coiling headS which advances into a recess in the other coiling head and which is of a length to provide an arbor for the coils throughout the entire coiling operation and as the right and left tool slides retract from each other during formation of the coils, the utilization of a surface on the forming arbor in its raised position which defines a limit of advance for the wire base to provide a controlled length for the base section of the double torsion spring, as well as other new and improved structural features of the machine providing for economical, rapid production of double torsion springs.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a four-slide machine having the tooling associated therewith for forming a double torsion spring;

FIG. 2 is a fragmentary plan view on an enlarged scale of the basic tooling elements added to the four-slide machine and with parts in section;

FIG. 3 is an elevational view, taken generally along the line 3-3 in FIG. 2;

FIG. 4 is a diagrammatic plan view, showing the elements positioned with the wire formed into a U-shape or staple and with the coiling heads still in retracted position;

FIG. 5 is a view, similar to FIG. 4, showing the coiling heads in advanced position in engagement with the wire for coiling;

FIG. 6 is a fragmentary side elevational view of the structure shown in FIG. 5, preparatory to rotation of the coiling heads to form the coils in the wire legs;

FIG. 7 is a view similar to FIG. 6 showing the forming arbor elevated to permit advance of the wire base during coiling as indicated by the rotation of the coiling head; and

FIG. 8 is a perspective view of a double torsion spring made by the method and machine disclosed herein.

DESCRIPTION OF THE PREFERRED EMBODIMENT The general machine is shown in FIG. 1, which is of a generally conventional type. The basic machine illustrated is of a type sold by The U.S. Baird Corporation and offered in a series of different sizes, and known as the Baird Four Slide Wire Forming Machine. This machine has a base, indicated generally at 10, which receives a wire 11 at the lefthand end thereof with the wire advancing through a wire straightener, indicated generally at 12, and being fed by a feed mechanism, indicated generally at 15, which reciprocates under the operation of a rotatable crank 16 and connecting linkage I7 and 18. The advanced length of wire 11 is held by holding structure, indicated generally at 20, immediately preceding a reciprocable cutter, indicated generally at 21. Beyond the cutter 21 is a coiling station, indicated generally at 22, and with the structure at said coiling station being more fully shown in the other Figures of the drawings.

The machine has a front slide, indicated generally at 25, which is operable reciprocably in a cycle by a cam 26 mounted on a front slide cam shaft 27 rotatably mounted in the base 10 and with a spring 28 being provided for returning of the front slide and to insure following of the cam 26. A right tool slide is indicated generally at 30 and is slidably mounted on the base 10 and with the movement thereof being controlled by a cam 31 on a cam shaft 32 rotatably mounted in the base 10. The cam 31 coacts with the follower 35 on the slide and a spring 36 causes the follower to follow the cam and provide for return movement of the right tool slide. A left tool slide is indicated generally at 40 and is slidably mounted on the base 10 with the movement of this slide being controlled by a cam 41 mounted on a cam shaft 42 rotatably mounted in the base 10. This cam engages a cam follower 43 on the left tool slide and a spring 44 maintains engagement between the cam and cam follower and causes return movement of the left tool slide.

A rear tool slide, indicated generally at 50, is movably mounted on the base 10 and is operated by a cam 51 mounted on a rear cam shaft 52 rotatable in the base 10. A cam fol lower 53 coacts with the cam 51 and a return spring 54 insures following of the cam 51 by the cam follower and return of the rear tool slide 50.

The rear cam shaft 52 has an additional cam 55 mounted thereon which coacts with a follower 56 on a crank arm pivotally mounted to a portion of the base with the opposite end of the crank arm being connected to a forming arbor to be described to provide for movement thereof 5 between raised and lowered positions. This crank arm is identified at 57 and is connected to a block 58 which is attached to the upper end of a forming arbor 60. A return spring 61 provides for following of the cam 55 by the follower 56. The rear slide 50 does not carry a tool, but has a bridge and associated rack structure for rotating coiling heads, later described.

With the structure described, the rotation of the cam shafts and the timing provided by the cams on the cam shafts as well as rotation of the crank 16 causes feeding of wire to the coiling station and a sequence of movement of the various slides in a manner to be described to form double torsion springs.

Referring particularly to FIGS. 2, 4, and 6, a length of wire 11 is shown in FIG. 2, in position between the lower part of the forming arbor 60 and the tooling on slide 25. This tooling includes a pair of pivoted jaws 70 and 71 mounted on block 72 and urged towards each other by a pair of internally mounted springs 73 and 74. As the front slide 25 advances toward the forming arbor 60, the jaws 70 and 71 pass to either side of the forming arbor 60 to form the wire into a U-shape or staple, as shown in FIG. 4. As soon as the jaws have engaged the wire against the forming arbor, the movement of the cutter 21 is timed to cut the length of wire off the supply to permit the wire to be formed with a wire base 75 (FIG. 4) and with a pair of wire legs 76 and 77 which lie against a pair of surfaces 78 and 79 on a vertically extending, stationary element 99 positioned to the rear of the forming arbor 60. These surfaces limit and define the U-shape formed by the forming jaws 70 and 71. The operation referred to, as shown in FIG. 4, is with the forming arbor 60 in the lowered position, as shown in FIG. 6, wherein a front edge 80 thereof is at the elevation of the jaws 70 and 71 and with the jaws being advanced to fully seat the forming arbor to the full depth of the jaws.

The next sequence of operation has the cam 55 on the rear cam shaft 52 raise the forming arbor 60 to the position shown in FIG. 7 wherein the leading edge 80 is raised above the wire base 75 with a leg 81 of the forming arbor still at the elevation of the wire. At the same time, the right tool slide cam 31 and left tool slide cam 41 advance their respective slides toward the coiling location. When these slides are retracted, they are in the position shown in FIGS. 1 and 2. The right tool slide 30 has a block 85 adjustably mounted thereon which rotatably mounts a coiling head 86 having a coiling arbor rotatable therewith, as well as a catch pin 88. The left-hand tool slide 40 adjustably mounts a block 90 carrying a coiling head 91 and having a catch pin 92. As shown particularly with respect to coiling head 91, the head is rotatably mounted within the block 90 and has a pinion 93 which coacts with a rack 94 extending rearwardly from the left tool slide 40. A similar pinion is associated with the coiling head 86 and has a rack 95 extending rearwardly therefrom. The coiling heads 86 and 91 are shown in retracted position in FIG. 4 and are shown in advanced, operative position in FIG. 5. In the advanced position, the coiling arbor 87 advances through a pilot hole 98 in the stationary element 99 having the guiding surfaces 78 and 79 and into an internal recess 100 in the coiling head 91.

Each of the coiling heads 86 and 91 are yieldably mounted in their respective housings and urged toward each other by a spring-urged hardened steel ball (not shown).

With the coiling heads positioned as shown in FIG. 5 and with the catch pins 88 and 92 being on top of the wire legs, rotation of the coiling heads 86 and 91 in the direction of the arrow 101 of FIG. 7 will cause rotation of the wire about the coiling arbor 87 to form coils in each of the wire legs 76 and 77. The catch pins 88 and 92 slightly grip or catch upon the wire legs and cause rotation of the wire without relative movement therebetween. This requires a supply of wire in forming the coils which is provided by advance of the wire base 75 toward the coiling occurring about the coiling arbor 87. This advance is permitted by elevation previously of the forming arbor 60 whereby the wire base can move from the broken line position, shown in FIG. 7, to a final position, shown in full line, wherein the wire base engages against the depending part 81 of the forming arbor. During this advance of the wire base, it will be advanced out of the forming jaws 70 and 71, which are still in position and do not retract until the end of a cycle, when all parts retract.

The wire base 75 is permitted to advance to supply the wire for forming the coils. However, it does not rotate and is prevented from doing so by the wire legs 76 and 77 sliding along and in engagement with the underside of horizontal surfaces 105 and 106 provided in the stationary element 99. Referring particularly to FIG. 7, it will be seen that rotation of the coiling arbor 87 and the catch pin 88 will cause the formation of a coil, with movement of the wire base from left to right and with the wire leg 77, or the part thereof between the base 75, and the coiling arbor 87 sliding under the surface 105 to prevent rotation of the wire base 75. The desired number of coils results from the desired number of revolutions of the coiling heads. As shown in FIG. 8, a resulting double torsion spring with the legs 76 and 77 has wire base 75 and with a number of coils formed in each leg.

The rotation of the coiling arbors 86 and 91 and their associated catch pins as well as the coiling arbor 87 is derived from reciprocation of the racks 94 and 95 which are interconnected for simultaneous movement by a bridge connected to the rear slide 50 by a member 121. The free ends of each of the racks 94 and 95 are slidably connected to the bridge 120 whereby they may move along the length of the bridge as shown in FIG. 2 to permit in and out movement of the coiling heads while still insuring simultaneous linear movement thereof under actuation of the rear cam 51 to cause simultaneous rotation of the coiling heads. The rear cam is shaped to have the catch pins always return to the rotative position shown in FIG. 6 prior to beginning of a cycle.

To form a smooth curve in the wire base 75, each of the tool slides 30 and 40 carries an adjustable abutment member and 126, respectively, which, upon advance of the tool slides 30 and 40 toward each other, engage the jaws 70 and 71, as shown in FIG. 4 to squeeze the jaws and impart a smooth curvature to the wire. This advance causes slight yielding of the coiling heads 86 and 91 as permitted by their spring loading.

The cams 31 and 41 associated with the right and left tool slides 30 and 40 are contoured to permit slight retracting movement of the tool slides 30 and 40 to retract the abutment members 125 and 126 a distance equal to the wire thickness before coiling and further retraction of the tool slides 30 and 40 during coiling to provide progressive separating movement of the coiling heads 86 and 91 and a space axially of the torsion spring as the coils are formed.

After the completion of the double torsion spring, as shown in FIG. 8, the front and rear as well as right and left tool slides all retract and the forming arbor is lowered to position the parts preparatory to feed of wire for formation of the next spring.

As will be seen, a method is provided herein wherein a length of wire is bent into a U-shape with a pair of legs, the legs are gripped and rotated and with the central wire base advancing toward the locations where the wire legs are gripped to provide wire length for the coils, whereby the free ends of the completed spring are substantially equal in length to the free ends of said wire legs beyond the location of gripping thereof.

It will be seen that the number of coils that can be formed in the legs 76 and 77 is substantially unlimited, since although the free ends of the wire legs 76 and 77 rotate during the coiling, they need not be of a length to provide wire for forming the coils, since this wire comes from the wire base end of the spring. Previously, the number of coils was limited because the wire for the coils came from the free ends and you could not have long, free ends of wire rotating during the coiling because of contact with nearby parts of the machine.

I claim:

l. The method of forming a double torsion spring comprising the following steps, feeding a continuous length of wire to a forming station, cutting a section of wire from said wire length at said forming station, forming the wire section at said forming station into an approximate U-shape with a pair of spaced legs, and coiling a plurality of coils in each of said legs simultaneously at said forming station by holding and rotating each of said legs and with the base of the wire section being held against rotation but movable toward the coils to provide sufficient wire for the coils, the spacing between the locations where the two legs are held increasing as the legs are rotated to form outwardly extending coils.

2. The method as defined in claim 1 wherein said legs are engaged by rotatable members which slightly bite into the wire.

3. The method as defined in claim 1 wherein said wire base is held against rotation by engaging the top of the wire legs between the wire base and the coiling location to permit sliding movement of the legs as the coils are formed.

4. A machine for forming double torsion springs comprising, a base, wire feeding and straightening means thereon, a coiling station having a center form with a forming arbor and a stationary element, a front slide with a bow-forming tool movable onto the forming arbor to form a center bow in a length of wire to bend the wire into a general U-shape with a base and a pair of legs against the stationary element, left and right tool slides each carrying a rotatable coiling head and a catch pin movable toward each other to engage the spacedapart wire legs, means for simultaneously rotating said coiling heads and catch pins to form a plurality of coils in each wire leg with progressive separating movement of the coiling heads, means retracting said forming arbor to permit movement of said wire base toward the coiling heads to provide wire for the coils, and means engaging said wire to hold said wire base against rotation while permitting advance thereof.

5, A machine as defined in claim 4 wherein said forming arbor has a surface in the plane of said wire base after said retraction to define a limit of advance for the wire base in the coiling operation.

6. A machine as defined in claim 4 wherein said stationary element has a pilot hole, a coiling arbor extending from one coiling head and of a length to extend through the pilot hole and into a central recess in the opposite coiling head and remain in said recess during said progressive separating movement.

7. A machine as defined in claim 4 wherein said bow-forming tool has a pair of spaced-apart jaws spring-urged toward each other which move along opposite sides of said forming arbor to form the center bow, and abutments on each of said right and left tool slides which engage said jaws to squeeze said wire and form a smoothly curved wire base.

8. A wire forming machine for forming double torsion springs comprising, a base, a coiling station having a center forming arbor movable between at least a bottom position and a raised position and a stationary element positioned to the rear thereof, a front slide with a bow-forming tool having a pair of jaws movable onto said forming arbor in said bottom position to form a bow at the center of a piece of wire to form the wire into a U-shape with a wire base and a pair of legs extending horizontally therefrom, said legs lying against the sides of the stationary element and under horizontal surfaces formed thereon, right and left tool slides movably mounted on said base and a rotatable coiling head with catch pin on each thereof, means including cams for moving said right and left slides toward each other to bring said coiling heads to the wire legs and said catch pins over the top of the wire legs, and means for rotating said coiling heads a desired number of revolutions to form the desired number of coils in each leg with said forming arbor in its raised position which permits advance of the wire base toward the coiling heads to provide wire for the coils and with said horizontal surfaces on the stationary element preventing rotation of the wire base.

9. A machine as defined in claim 8 including abutments on each of said right and left tool slides which en age said pair of aws to squeeze said wire and form a smoot ly curved wire base.

10. A machine as defined in claim 8 wherein each of said coiling heads is rotatably mounted in its respective slide, a pinion affixed to each head, a pair of racks associated one with each pinion, means for actuating said racks from the rear slide cam of the machine including a bridge moved by the cam, and means for slidably connecting the end of each rack to the bridge whereby the bridge movement imparts linear movement to the racks while permitting movement of the racks lengthwise of the bridge as the right and left tool slides move toward and away from each other.

11. A machine as defined in claim 8 wherein said forming arbor has a surface in the plane of said wire base in said raised position to define a limit of advance for the wire base in the coiling operation.

12. A machine as defined in claim 8 wherein means are provided to cause progressive separating movement of said coiling heads as the coils are formed in said legs.

13. A machine as defined in claim 12 wherein said stationary element has a pilot hole, a coiling arbor extending from one coiling head and of a length to extend through the pilot hole and into a central recess in the opposite coiling head and remain in said recess during said progressive separating movement.

14. A method of forming a double torsion spring at a single station wherein a length of wire is bent into a U-shape with a pair of legs extending from a central wire base, the legs are gripped and rotated and with the central wire base advancing toward the locations where the wire legs are gripped to provide wire length for the coils whereby the free ends of the completed spring are substantially equal in length to the free length of said wire legs beyond the location of gripping thereof, and with the distance between the gripping locations on the two legs increasing during rotation of the legs to form outwardly extending coils.

Claims (14)

1. The method of forming a double torsion spring comprising the following steps, feeding a continuous length of wire to a forming station, cutting a section of wire from said wire length at said forming station, forming the wire section at said forming station into an approximate U-shape with a pair of spaced legs, and coiling a plurality of coils in each of said legs simultaneously at said forming station by holding and rotating each of said legs and with the base of the wire section being held against rotation but movable toward the coils to provide sufficient wire for the coils, the spacing between the locations where the two legs are held increasing as the legs are rotated to form outwardly extending coils.

2. The method as defined in claim 1 wherein said legs are engaged by rotatable members which slightly bite into the wire.

3. The method as defined in claim 1 wherein said wire base is held against rotation by engaging the top of the wire legs between the wire base and the coiling location to permit sliding movement of the legs as the coils are formed.

4. A machine for forming double torsion springs comprising, a base, wire feeding and straightening means thereon, a coiling station having a center form with a forming arbor and a stationary element, a front slide with a bow-forming tool movable onto the forming arbor to form a center bow in a length of wire to bend the wire into a general U-shape with a base and a pair of legs against the stationary element, left and right tool slides each carrying a rotatable coiling head and a catch pin movable toward each other to engage the spaced-apart wire legs, means for simultaneously rotating said coiling heads and catch pins to form a plurality of coils in each wire leg with progressive separating movement of the coiling heads, means retracting said formIng arbor to permit movement of said wire base toward the coiling heads to provide wire for the coils, and means engaging said wire to hold said wire base against rotation while permitting advance thereof.

5. A machine as defined in claim 4 wherein said forming arbor has a surface in the plane of said wire base after said retraction to define a limit of advance for the wire base in the coiling operation.

6. A machine as defined in claim 4 wherein said stationary element has a pilot hole, a coiling arbor extending from one coiling head and of a length to extend through the pilot hole and into a central recess in the opposite coiling head and remain in said recess during said progressive separating movement.

7. A machine as defined in claim 4 wherein said bow-forming tool has a pair of spaced-apart jaws spring-urged toward each other which move along opposite sides of said forming arbor to form the center bow, and abutments on each of said right and left tool slides which engage said jaws to squeeze said wire and form a smoothly curved wire base.

8. A wire forming machine for forming double torsion springs comprising, a base, a coiling station having a center forming arbor movable between at least a bottom position and a raised position and a stationary element positioned to the rear thereof, a front slide with a bow-forming tool having a pair of jaws movable onto said forming arbor in said bottom position to form a bow at the center of a piece of wire to form the wire into a U-shape with a wire base and a pair of legs extending horizontally therefrom, said legs lying against the sides of the stationary element and under horizontal surfaces formed thereon, right and left tool slides movably mounted on said base and a rotatable coiling head with catch pin on each thereof, means including cams for moving said right and left slides toward each other to bring said coiling heads to the wire legs and said catch pins over the top of the wire legs, and means for rotating said coiling heads a desired number of revolutions to form the desired number of coils in each leg with said forming arbor in its raised position which permits advance of the wire base toward the coiling heads to provide wire for the coils and with said horizontal surfaces on the stationary element preventing rotation of the wire base.

9. A machine as defined in claim 8 including abutments on each of said right and left tool slides which engage said pair of jaws to squeeze said wire and form a smoothly curved wire base.

10. A machine as defined in claim 8 wherein each of said coiling heads is rotatably mounted in its respective slide, a pinion affixed to each head, a pair of racks associated one with each pinion, means for actuating said racks from the rear slide cam of the machine including a bridge moved by the cam, and means for slidably connecting the end of each rack to the bridge whereby the bridge movement imparts linear movement to the racks while permitting movement of the racks lengthwise of the bridge as the right and left tool slides move toward and away from each other.

11. A machine as defined in claim 8 wherein said forming arbor has a surface in the plane of said wire base in said raised position to define a limit of advance for the wire base in the coiling operation.

12. A machine as defined in claim 8 wherein means are provided to cause progressive separating movement of said coiling heads as the coils are formed in said legs.

13. A machine as defined in claim 12 wherein said stationary element has a pilot hole, a coiling arbor extending from one coiling head and of a length to extend through the pilot hole and into a central recess in the opposite coiling head and remain in said recess during said progressive separating movement.

14. A method of forming a double torsion spring at a single station wherein a length of wire is bent into a U-shape with a pair of legs extending from a central wire base, the legs are gripped and rotated and with the central wire baSe advancing toward the locations where the wire legs are gripped to provide wire length for the coils whereby the free ends of the completed spring are substantially equal in length to the free length of said wire legs beyond the location of gripping thereof, and with the distance between the gripping locations on the two legs increasing during rotation of the legs to form outwardly extending coils.

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