US2920348A - Apparatus for forming spring cords - Google Patents

Description

Jan. 12, 1960 E. L. FRANKE, JR 2,920,348

APPARATUS FOR FORMING SPRING CORDS Filed Aug. 29, 1957 4 Sheets-Sheet 1 FIG. I

IN V EN TOR. E. L m4 NKE, JR.

A TTORNEV Jan. 12, 1960 Filed Aug. 29, 1957 E. L. FRANKE, JR

APPARATUS FOR FORMING SPRING CORDS 4 Sheets-Sheet 3 r ATTORNEY Jan. 12, 1960 E. L. FRANKE, JR

APPARATUS FOR FORMING SPRING CORDS Filed Aug. 29, 1957 4 Sheets-Sheet 4 v INVENTOR. E. L. FRANKIE, JR.

A TTORNEY 2,920,348 I Patented Jan. 12, 1960 United States Patent fifice 2,920,34s APPARATUS FOR FORMING SPRING coRDS This invention relates to apparatus for forming spring cords, and more particularly to apparatus for forming helically coiled spring cords.

In the telephone field and the field of various electrical appliances, it has been the practice in certain applications to utilize spring or retractile cords which are formed normally in a compact helical coil, and which will lengthen during tension but will return to the normal coiled position upon the removal of tension therefrom.

Various types of apparatus are known for performing varied operations with respect to the formation and manufacture of spring cords. Many of these machines require much in the way of manual operations, which of course increases the cost with respect to the end product.

It is an object of the present invention to provide improved apparatus for making spring cords.

It is a further object of the invention to provide apparatus for reverse coiling of a partially formed spring cord.

It is a still further object of the invention to provide apparatus for advancing a spring cord therethrough and for simultaneously reversing the helical coil thereof.

It is yet another object of the invention to provide apparatus for reversing the helical coil of a spring cord, for overtwisting the cord during reversal thereof, and for untwisting substantially all of the overtwist imparted to the coil.

In the manufacture of spring cords in the past, it has been found advantageous to provide a length of cordage which is coiled on a mandrel in a helical configuration. An apparatus for performing such an operation may consist of means for rotating and advancing laterally a mandrel on which the cordage is directed from a supply spool, which supply spool is rotated on an axis perpendicular to the axis of the supply reel to provide axial twist to the cord which is being coiled on the mandrel. After the complete helical coil is'formed on the mandrel, the mandrel with the coil thereon is then placed in a heattreat oven for a sufiicient time and at a suflicient temperature to set the material forming the jacket on the spring cord. Such a machine is disclosed in Patent 2,413,715, issued to A. R. Kemp et al. on January 7, 1947.

After the cord is properly heat treated and cooled, it is removed from the mandrel, and then apparatus is utilized to reverse the pitch of the helical coil. It has been found that by reversing the pitch of the helices of the coil, a cord having greater retractility is obtained.

The present apparatus is provided to reverse the pitch of the helicm of the spring cord, and in the description thereof it will be assumed that the cords have initially been wound on a mandrel and heat treated in some manner, such as that disclosed in the above-referred to patent. However, in the present apparatus it should be understood that no axial pretwist is imparted to the cord during winding on the mandrel. Instead a spring cord is provided wherein the forces-necessary for retractability are enhanced by the use of the present apparatus. Such a spring cord is disclosed in detail in copending application Serial No. 681,035, filed on August 29, 1957, in the names of E. C. Hardesty and D. L. Myers.

Generally, the apparatus may consist of a pair of spaced endless members, each having a plurality of opposed article holders secured thereon, between pairs of which partially formedspring cords may be secured. As the endless members are moved in synchronism, the opposite holders are' rotated in opposite directions to cause the spring cord to be coiled in a reverse direction and to an extent greater than necessary to form the coil, resulting in an overtwist. During the reverse coiling operation, an endless chain with fingers thereon serves to impart tension to the spring cord to prevent knotting and kinking thereof. After the endless members advance the reversed and overtwisted spring cord beyond the point where the holders are rotated, a second means causes the holders secured to one of the members to be rotated in a direction opposite to its previous rotation to remove substantially all of the overtwist therefrom.

A more detailed understanding of the invention may be had by reference to the following detailed description thereof, when reviewed in conjunction with the accompanying drawings, wherein:

Fig. l is a plan view, with portions away, illustrating the apparatus;

Fig. 2 is a side elevation of the apparatus illustrated in Fig. 1;

thereof broken Fig. 3 is a sectional view of the apparatus taken sub-' stantially on the line3-3 of Fig. 2;

Fig. 4 is an enlarged sectional view taken substantially on the line 4-4 of Fig. 1;

Fig. 5 is a sectional view taken substantially on the line 5-5 of Fig. 4, and

Fig. 6 is a view similar to ment of the invention.

Referring now to the drawings, wherein like reference numerals throughout the various views designate the same elements, and particularly to Figs. 1, 2 and 3, it may be seen that the apparatus consists of a pair of spaced, parallel, endless members 11 which are each supported by an idler sprocket 12 and a driven sprocket 13. The sprockets 12 and 13 are supported on shafts 14 and 16, respectively, which: are journalled in suitable bearings 17 extending from frame members 18, which form a portion of the frame of the apparatus.

The shaft 16 is provided with a gear 19 extremity thereof. The gear 19 is driven motor 21- through a chain or pulley 22, which extends around the gear 19 and at the opposite end is driven by a gear 23 on the shaft of the motor 21. Thus, at such time as the motor 21 is operating, the gear 19 will be rotated in a clockwise direction, as viewed in Fig. 2, causing the shaft 16 and the sprockets 13 to rotate in a similar direction, thus causing the endless members 11 to likewise move in a clockwise direction with the upper portion thereof moving from left to right, as viewed in Fig. 2.

The endless members 11 are each provided with a plurality of members 24 secured suitably thereto. The members 24 are each provided with an upstanding portion 26, such as may be seen in Fig. 5, in which is journalled a shaft 27. The shaft 27 is provided at one extremity with an article holder or chuck 28', and at the opposite extremity witha wheel 29 in the form of a pulley. The wheel 29' does not rotate with respect to the shaft 27, but instead, if any rotational impetus is given to the wheel 29, the shaft 27 and article holder 28 will rotate therewit v Extending above and substantially parallel to each of the endless members '11 for a portion of the apparatus are driving members or belts 31, which are secured rotatably at one endover idler pulleys 32, which are jour- Fig. 3 of a second embodinear one by means of a 3 nalled in bearings 33 on the frame members 18. The opposite end of each belt or drive member 31 is supported on a second pulley 34, which is on a shaft 36 secured suitably by journals 37 to the frame member 18. The shaft 36, associated with one of the drive members 31, is provided near one end thereof with a pulley 38 over which passes a drive belt 39.

The drive belt 39 has its opposite extremity passing over a pulley 41, which is secured to a shaft 42 journalled in bearings 43. The shaft 42 is provided with a second pulley 44 over which passes a drive belt which also passes over a pulley 47 secured near the end of a drive shaft 48 of a suitable motor 49.

The shaft 42 is further provided with a gear 51 thereon, which meshes with a companion gear one extremity of a shaft 53, which is journalled suitably in bearings 54. The opposite end of the shaft 53 is provided with a pulley 56, over which passes a drive belt 57 which at its opposite extremity passes over a pulley associated with the other of the drive members 31. The drive belt 57 and the pulley 58 are similar and for the same purpose as the drive belt 39 and the pulley 38, respectively. in other words, one of the drive belts 31, the two of which are secured in parallel relationship on opposite sides of the apparatus, is caused to move in a counterclockwise direction, as viewed in Fig. 2, under the control of the pulley 38. However, because of the provision of the companion meshing gears 51 and 52, the other drive member 31 will be moved in an opposite direction. For example, the member 31, as viewed in Fig. 2, will move in a counterclockwise direction, whereas the drive member 31 at the opposite side of the machine, not illustrated except in Fig. 4 and then in a reverse position, will be moved in a clockwise direction.

As mentioned previously, the drive members 31 are suspended above and in parallel relationship to the upper portion of the endless members 11. The members 31 are so positioned that as the endless members 11 move, thereby imparting similar movement to their upstanding members 26 and the shafts 27 on which are secured the article holders 28 and the wheels 29, some of the wheels 29 will underlie and will be in contact with the member 31. Therefore, as the endless members 11 advance and move the shafts 27, the article holders 28 and the wheels 29 therewith, during a portion of their travel the wheels 29 will come into engagement with the members 31 to cause rotation to the wheels 29 and similar rotation to the article holders 28. As mentioned above, the wheels 29 associated with one of the members 11 will be rotated in one direction, and the wheels 29 associated with the other of the members 11 will be rotated in the opposite direction.

Also positioned near the apparatus, as viewed in Fig.

rightward extremity of the 2, are a pair of idler pulleys 61 and a drive pulley 62 in a somewhat triangular configuration and over which passes a drive member 63. The idler pulleys 61 are so positioned that the lower run of the drive member 63 is substantially parallel to one of the endless members 11, and is so located that, during a portion of the movement of the members 11, the drive member 63' will overlie and be in actuating contact with respect to the wheels 29 at the extremity of the shafts 27 associated with one of the members 11 only.

The drive pulley 62 is secured to a stub shaft 64, which is journalled in bearings 66 and on the opposite extremity of which is provided a gear 67. The gear 67 is in meshing engagement with a companion gear 68, which is secured to one extremity of a stub shaft 69, which is journalled in bearings 71 and which is provided at its opposite extremity with a pulley 72. A drive belt F3 passes over the pulley 72, and at its opposite extremity passes over a pulley 74 which is secured to the shaft 48 of the motor 49, and is similar to the pulley 47. Thus, at such time as the motor 49 and the shaft 48 52 which forms i are operating, the drive member 31, as mentioned previously, will be moving in a counterclockwise direction, as viewed in Fig. 2. However, because of the provision of the gears 67 and 68, the drive member 63 will be moving in an opposite or clockwise direction, as viewed in Fig. 2.

Positioned intermediate the sides of the machine is an endless chain 76 which passes over an idler sprocket 77 at the leftward extremity thereof, as viewed in Fig. 2. The sprocket 77 is secured in suitable bearings 78. The endless chain 76 also passes over a second smaller idler sprocket 79 at the rightward extremity, as viewed in Fig. 2, which is likewise journalled in suitable bearings 81. A drive sprocket 82 for the chain 76 is secured in suitable :7. ings between and above the sprockets 77 and 79 in a position so that the sprockets 77, 79 and 82 and the chain 76 are in the configuration of a triangle. As viewed in Fig. 2, the chain 76 will move in a counterclockwise direction.

The sprocket 82 is secured on a shaft 83, which is journalled in suitable bearings 84 and which is provided with a gear 86 intermediate thereof. The gear 86 meshes with a companion gear 87 which is at one extremity of a stub shaft 88, which is suitably journalled in bearings 89. The stub shaft 88 is provided at its opposite extremity with a sprocket 91 over which passes a drive chain 92. The opposite extremity of the drive chain 92 passes over a sprocket 93, which is secured on the shaft 16. Thus, at such time as the motor 21 is operated to move the drive members 11 in a clockwise direction, as viewed in Fig. 2, the chain 76 will be moved through the various shaft and pulley arrangements in a counterclockwise direction, as viewed in Fig. 2.

The chain 76 is provided at suitable intervals with extending fingers 94-, as may be seen more clearly in Figs. 2 and 4.

The drive members 31 are each provided with a guide consisting of vertical supports 96 and horizontal members 97 secured to the framework of the apparatus. The lower member 97 is so positioned that the lower run of the drive member 31 will pass therebeneath, assuring that that portion of the drive member 31 will be maintained in a horizontal position and in engagement with the wheels 29.

Similarly, the drive member a guide of vertical supports 98 and a horizontal member 99. The lower member 99 is so positioned that the lower min of the drive member 63 will pass therebeneath and will maintain that portion of the drive member 63 in a horizontal position and in engagement with the wheels 29.

63 is also provided with Operation In operating the apparatus to provide the proper reverse twist to the spring cord, it must be remembered, as indicated previously, that the instant apparatus is used in conjunction with spring cords which have been wound initially in a helical coil, but with no axial twist, and which have been properly heat treated. Thereafter, the cords are positioned in the instant apparatus to obtain proper reversal of the helices of the coil to provide a finished spring cord.

With reference now to Fig. 3, and particularly the left side thereof, partially fabricated spring cords 100 are positioned in the machine with the opposite extremities of each cord being inserted in opposed article holders 28 secured to members 24, one on each of the endless members 11. The extremities of the cords 100 may be positioned in the article holders 28 manually, which article holders may be of any suitable and conventional design whereby the cords may be loaded rapidly and easily in the machine.

If it is assumed that the motor 21 is operating at this time, the endless members 11 will be moving in a clockwise direction, as viewed in Fig. 2, which will cause the 100is for the article holders 28 and the cords 100 to be moved from the left toward the right, asviewed inFigsJZ and 3.

As the cords 100 are advanced toward the right, as viewed in Figs. .2.and 3, a position will be reached where- ,at the fingers 94 on the chain .76 will engagethe cord 100 at substantially the midpoint thereof. .Inasmuch as the chain 76 is moving in a counterclockwise direction, as viewed in Fig. 2,the c'hain'76, through the fingers 94, will cause the cord 100 to follow vthe course of the chain 76 to a position where it will underlie the underportion of the chain in its movement to extend or tension the cord 100. The chain 76 and its operation of tensioning the cords purpose of preventing any knotting or twisting of the cord during the reverse coiling operation.

As the members 11, article holders 28 and cords 100 continue to move toward the right, as viewed in Figs. 2 and 3, a position will be reached whereby the wheels 29 on the shafts 27, to which ;the article holders 28 are also connected, will pass under the drive members 31 at opposite sides of the machine. At-this time the members 31 will impart rotation to the wheels 29 and, as mentioned previously, likewise to the shafts 27 and article holders 28. However, as was also mentioned previously, because of the gears 51 and 52, the members 31 at opposite sides of the apparatus will be rotated in opposite directions. This will result in the article holders 28 likewise rotating in opposite directions, imparting similar movement to the ends of the cord 100 held thereby.

As the apparatus continues to operate to advance the cords 100 toward the right, the members 31 will impart sufficient rotation to the wheels 29 to cause an entire reversal of the pitch of the helices of the coil in the initially coiled spring cords 100, and, further, will impart additional rotation thereto to provide an overtwist or more twist than is necessary to coil the cord to its ultimate reverse size convolutions.

It has been found that by placingthe additional twist, which is currently termed overtwist to the cord, there results an even distribution of forces throughout the entire length of the cord. The actual result, which is visible as a result of the overtwist, will be that the convolutions of the coil will be more compact and will assume a smaller diameter than in the final finished product.

As the cords continue in their rightward movement, as viewed in Fig. 2, a position will be reached at which the wheels 29 will no longer underlie the member 31, and, therefore, no further rotation will be imparted to the wheels 29 and article holders 28. The length of the members 31 and the speed at which the wheels 29 are advanced therepast must be determined in accordance with the desired finished product.

The cords 100 will continue to be moved toward the right, as viewed in Fig. 2, and, if there should be any tendency for the forces in the overtwisted cord 100 to cause rotation to the article holders 28 and wheels 29 to relieve the forces therein, it may be desirable to include a cam plate and cam on the shaft or wheel flange to overcome any tendency of the cords 100 to cause rotation to the holders 28.

As the cords 100 move further toward the right, as viewed in Fig. 2, they will reach the position where the wheels 29 will underlie the member 63. The motor 49, which has been imparting motion to the members 31, likewise is imparting motion at this time to the member 63, all in a manner as described previously.

The movement of the member 63, which imparts rotation to the wheels 29, will cause rotation of the wheels 29 associated with one of the endless members 11 only. As a result, the article holders 28 at one side of the machine will be rotated, but, because of the gears 67 and 68, in a direction opposite to the rotation imparted to the Wheels 29 as they passed under the member 31 on the same side of the machine- Thus, the. rotation of the wheels 29 at this point will, result in an unwinding or the endless chain 76 is .-removal of substantially-all of the overtwist which had "been placed in the cords through their movement under the mem'bers31.

It s'houldbe noted that shortly after the wheels-29 are engaged by the drive member 63, the end of the run of reached. At this position the fingers 94 will releasethe cords 100 and no further tension willbe. imparted thereto.

The operative length of the member 63 in engagement with the wheels '29 and the speed at which the members 11 are advancing the cords through the machine must be determined in accordance with the final product desired.

As the members 11 advance the cords 100 further to the .right, they will be advanced to a position where the Wheels 29'will no longer engage the member 63. At this point, the overtwist will have been removed from the cords and they will 'now'be of a size, pitch and compactness of the final product. It will then only be necessary for an operator to release the article'holders 28 and remove the finished cord therefrom. If desirable, it is possible to design the article holders 28 so that, as they reach the rightward extremity of the machinery, they may be opened automatically and the cords released therefrom and dropped in any suitable container.

By reference to Fig. 3, a comparison may be made of the initially wound cord as it is placed in the machine,

which is illustrated by the two cords 100 at the extreme leftward extremity of the machine, with the finished cord which is illustrated by the cord at the extreme rightward extremity of the machine. From a comparison of the two cords, it will be seen that the pitch of the convolutions have been reversed and that the finished cord is compact and that the convolutions are of equal pitch and of even size. It may also be noted by the fourth cord from the left that the cord is smaller and has more convolutions. This cord is at a position after overtwist and before complete removal of the overtwist.

While the extremities of the cords 100 have not been illustrated, it should be understood that it is contemplated that the instant machine may be used for spring cords with unfinished ends as well as spring cords which have been tipped and banded prior to their initial helical coiling and heat treating. If such latter are used, it may be desirable to design article holders, such as 28, which are provided with space therein for the tipped conductors extending outwardly from the insulating jacket at the end of the spring cord. Such may be advisable to prevent the individual conductors from flying loose as rotation is imparted to the cord, which may result in entanglement with operating parts of the machine or with similar conductors of adjacent cords.

Second embodiment If reference is now to Fig. 6, a second embodiment of v the invention may be seen. It should be understood that the apparatus of Fig. 6 will have the same elements operating in the same manner as the first embodiment disclosed in Figs. 1 to 5, inclusive, except that the courses of the endless members 11 are not parallel throughout.

In the embodiment disclosed in Fig. 6, it may be seen that the members 11 are spaced closer together at the loading portion thereof, as viewed at the left end in Fig. 6. It has been found that such a spacing is most advantageous for the machine operator inserting the ends of the cords 100 in the article holders 28 on opposite sides of the machine.

The spacing at the left end is not proper for the reversing operation however, and, therefore, the members 11 are positioned further apart for the portion of the apparatus wherein the reversing occurs of the pitch of the convolutions of the cord. Such change in spacing may be achieved by proper positioning of the supporting and mounting means for the endless members 11.

The spacing of the members 11' is the same during the portion of the apparatus wherein the removal of the overtwist occurs, under the control of the drive member 63, as it is during the portion of the apparatus wherein the reversing occurs, under the control of the drive members 31.

After the reversal and removal of overtwist in the cords 100 is performed by the apparatus, the members 11 are spaced closer together than either of the previous courses, as seen at the extreme right in Fig. 6. Such spacing at this position is equal to the length of the finished cord 160 when it is removed from the apparatus.

It should be understood that at each width of spacing of the members 11 that they are parallel to eachother.

Although specific embodiments of the invention have been illustrated and described, it will be understood that such embodiments are but illustrative, and that various modifications may be made therein without departing from the scope and spirit of this invention.

What is claimed is:

1. Apparatus for forming spring cords, which comprises a plurality of opposed pairs of holders, each holder of an opposed pair receiving the opposite extremity of a spring cord formed in a helical coil, means for moving said holders through a fixed path, means for rotating said opposed holders in opposite directions during the movement thereof so as to cause a reversal of the coiling of the spring cord, whereby a spring cord is formed having a helical coil with a pitch opposite to that of the initial helical coil, and means for maintaining the spring cord under tension during at least a portion of the movement of said holders through the fixed path.

2. Apparatus for forming spring cords, which comprises a plurality of opposed pairs of holders, each holder of an opposed pair receiving the opposite extremity of a spring cord formed in a helical coil, means to move said holders through a fixed path, means to rotate said opposed holders in opposite directions during the movement thereof in a direction to impart a reversal of the coiling of the spring cord and to an extent greater than necessary to form the reversed coiling to impart overtwist to the cord, and means to rotate at least one of said holders in a reverse direction to remove the overtwist from the spring cord.

3. The apparatus described in claim 2 wherein means are provided to maintain the spring cord under tension during at least a portion of the movement of said holders through the fixed path.

4. Apparatus for forming spring cords, which comprises a pair of spaced endless members, a plurality of article holders on said members positioned in opposed spaced relationship, means to move said members in synchronism, means to rotate said article holders during a portion of the movement of said members, and means to rotate said article holders on one of said members only in a direction opposite to the direction in which they were rotated by said first article holder rotating means during a further portion of the movement of said members.

5. Apparatus for forming spring cords, which comprises a pair of spaced members, a plurality of article holders secured to said members positioned in opposed spaced relationship for receiving the opposite extremities of helically coiled spring cords, means to move said members in synchronism, means to rotate said article holders during a portion of the movement of said members, said article holders on opposite of said members being rotated oppositely, to reverse the pitch of the helices of the coil and to an extent greater than necessary to form the reversed helical coil, and means to rotate said article holders on one of said members only in a direction opposite to that in which they were rotated by said first article holder rotating means during a further portion of the movement of said members to remove the excess twist placed in the helical coil.

6. The apparatus as described in claim 5 wherein means are provided to maintain the spring cords under tension substantially during the interval in which said first-mentioned article holder rotating means is acting on the spring cords.

7. The apparatus as described in claim 5 wherein an endless member having fingers projecting therefrom is provided, the fingers engaging the spring cords and maintaining them under tension substantially during the interval in which said first-mentioned article holder rotating means is acting on the spring cords.

8. Apparatus for forming spring cords, which comprises a pair of spaced members, a plurality of rotatable article holders secured to each of said members for movement therewith and positioned in opposed paired relationship, each pair of opposed holders receiving the opposite extremity of a helically coiled spring cord, a wheel secured to each of said article holders for imparting rotation thereto, means for moving said spaced members in synchronism, first actuating means positioned adjacent to a portion of the members for imparting rotation to the wheels as said members are moved and said wheels are presented to said actuating means, the first actuating means being designed to impart rotation to said wheels to an extent greater than necessary to reverse the helical coil so as to place an overtwist in the cord, and second actuating means positioned adjacent to a subsequent portion of one of said spaced members for imparting rotation to the wheels of the holders on said last-mentioned member in a direction opposite to the previous rotation thereof as said last-mentioned wheels are presented to the second actuating means so as to remove the overtwist from the cord.

9. The apparatus as described in claim 8, wherein means are provided to maintain the spring cords under tension substantially during the interval that the first actuating means imparts rotation to the wheels.

10. The apparatus as described in claim 8, wherein an endless member having fingers projecting therefrom is provided, the fingers engaging the spring cords and maintaining them under tension substantially during the interval that the first actuating means imparts rotation to the wheels.

11. The apparatus as described in claim 10, wherein said endless member is positioned substantially midway between said spaced members and the fingers engage the spring cords at substantially the midpoint thereof.

12. Apparatus for forming spring cords, which comprises a pair of endless members, a plurality of article holders secured to said members in opposed spaced relationship for receiving the opposite extremities of helically coiled spring cords, said members being spaced apart at one distance at the position whereat the cords are secured in said holders, means to move said members in synchronism, means to rotate said article holders during a portion of the movement of said members, said article holders on opposite of said members being rotated oppositely, to reverse the pitch of the helices of the coil and to an extent greater than necessary to form the reversed helical coil, and means to rotate said article holders on one of said members only in a direction opposite to that in which they were rotated by said first article holder rotating means during a further portion of the movement of said members to remove the excess twist placed in the helical coil, said members being spaced apart at a greater distance than said first distance adjacent to said first and said second article holder rotating means.

13. The apparatus as described in claim 12 wherein said members are spaced at a third distance at a position past said second article holder rotating means to facilitate removal of the finished cords from said article holders, said third distance being less said first and said second distances.

14. Apparatus for forming spring cords, which comprises a plurality of pairs of article holders, an endless conveyor for mounting said holders in an endless succession of aligned spaced pairs, means for driving said conveyor so that the aligned pairs of article holders advance continuously a succession of spring cords having helically coiled portions, the opposite ends of each of the spring cords being held by an associated pair of holders, first actuating means for imparting relative rotation to the pairs of holders about their axes of alignment in a manner such as to reverse the helically coiled portion of each of the spring cords, said first actuating means being designed to impart rotation to said holders to an extent greater than necessary to accomplish a complete reversal of said helically coiled portion so as to impart a predetermined amount of overtwist thereto, and second actuating means for imparting relative rotation in the opposite direction to the pairs of holders to an extent suflieient to remove substantially all of the overtwist from the spring cords.

15. The apparatus as described in claim 14, wherein portions of the endless conveyor are so constructed and arranged as to cause a gradual movement of the spaced holders of each pair away from one another to stretch and tension the spring cord held therebetween.

16. Apparatus for forming spring cords, which comprises a plurality of spaced pairs of article holders, an endless conveyor for mounting said holders in an endless succession of aligned spaced pairs, means for driving said conveyor so that the aligned pairs of article holders advance continuously a succession of spring cords having helically coiled portions, the opposite ends of each of said spring cords being held by an associated pair of holders, means for rotating said holders relative to each other about their axes of alignment during the advance thereof in a direction such as to impart a reversal of the coiling of the spring cord whereby a spring cord is formed having a helical coil with a pitch opposite to that of the initial helical coil, and means for maintaining the spring cord under tension during at least a portion of the advance thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,653,381 Whitemore et al Dec. 20, 1927 2,334,793 ScuSa NOV. 23, 1943 2,478,861 Collins et al. Aug. 9, 1949

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