METHOD FOR PACKAGING GLASS STRANDS
United States Patent 3687381
A rotatable mandrel for holding a tube on which a glass strand is wound into a package which has elongated fingers extending lengthwise of the mandrel in closely adjoining relation, said fingers being loosely held for outward movement under the centrifugal force of the rotation of the mandrel whereby the tube is held to its greatest diameter, each of said fingers having a groove along its longitudinal center line and tapered edges whereby on termination of the rotating movement of the mandrel and of the associated application of centrifugal force against the tube, the tube is constricted by the tension of the wound strand thereon and to effect an accommodating reduction in diameter, portions of the tube collapse and enter into the depressed areas of the center grooves and tapered edges of the fingers.
US Patent References:
Winding mechanism and method
Fletcher - March 1942 - 2274681
Apparatus for winding strands
Slayter - December 1948 - 2457786
Winding mandrel for packaging glass strands
Smith - June 1959 - 2891798
Winding apparatus
Fletcher - September 1959 - 2906470
Expansible mandrel
Sokal - September 1961 - 3000585
Winding mechanism and method
Fletcher - March 1942 - 2274681
Apparatus for winding strands
Slayter - December 1948 - 2457786
Winding mandrel for packaging glass strands
Smith - June 1959 - 2891798
Winding apparatus
Fletcher - September 1959 - 2906470
Expansible mandrel
Sokal - September 1961 - 3000585
Inventors:
Cunningham, Cecil R. (Aiken, SC)
Rushton, James C. (Aiken, SC)
Rushton, James C. (Aiken, SC)
Application Number:
05/012531
Publication Date:
08/29/1972
Filing Date:
01/29/1970
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
242/920, 242/571.600, 242/610
International Classes:
B65H54/54; B65H54/40; B65H54/02
Field of Search:
242/18G,18,1,54,47
Primary Examiner:
Gilreath, Stanley N.
Parent Case Data:
This is a division of applicants' copending application Ser. No. 711,776, filed Mar. 8, 1969, now U.S. Pat. No. 3,544,016.
Claims:
We claim
1. A method of packaging a fibrous glass strand on a non-elastic tube which comprises holding the tube in a taut cylindrical form while the fibrous glass strand is tensionally wound thereon, releasing the tube from its taut condition after the fibrous glass strand has been wound thereon, supporting the tube in a generally cylindrical form of reduced diameter to relieve the tension of the wound strand and providing indented areas into which portions of the tube may be gathered in wrinkles to permit such reduction in the diameter of the tube.
2. A method according to claim 1 in which the tube is of fibrous composition.
3. A method according to claim 1 in which the tube diameter is reduced between 2 and 6 percent.
4. A method of packaging for later easy dispensing a fibrous glass strand which may be elongated under tensional stress due to its elasticity and straightening of the strand and the filaments thereof from predisposed twists and turns, which comprises tensionally winding the strand upon itself in cylindrical form over a tautly stretched, wrinklable, non-elastic sleeve held in cylindrical shape by internal support means while maintaining the wound strand in the elongated condition due to the tensional winding, after the winding of the strand is completed tensionally relieving the wound strand to return it to substantially its original length through contraction of its cylindrically wound form by limited retraction of the internal support means of the sleeve and proportional collapse of the sleeve, providing longitudinally positioned depressed areas in the internal support means for receipt of thickened portions of the sleeve to accommodate the sleeve to its reduced cylindrical shape, and finally removing the wound strand and sleeve from the support means.
5. A method according to claim 4 in which the tube is creped or wrinkled before it is tautly stretched.
6. A method according to claim 4 in which the tube is of fibrous composition.
7. A method according to claim 6 in which the tube is composed of paper stock.
1. A method of packaging a fibrous glass strand on a non-elastic tube which comprises holding the tube in a taut cylindrical form while the fibrous glass strand is tensionally wound thereon, releasing the tube from its taut condition after the fibrous glass strand has been wound thereon, supporting the tube in a generally cylindrical form of reduced diameter to relieve the tension of the wound strand and providing indented areas into which portions of the tube may be gathered in wrinkles to permit such reduction in the diameter of the tube.
2. A method according to claim 1 in which the tube is of fibrous composition.
3. A method according to claim 1 in which the tube diameter is reduced between 2 and 6 percent.
4. A method of packaging for later easy dispensing a fibrous glass strand which may be elongated under tensional stress due to its elasticity and straightening of the strand and the filaments thereof from predisposed twists and turns, which comprises tensionally winding the strand upon itself in cylindrical form over a tautly stretched, wrinklable, non-elastic sleeve held in cylindrical shape by internal support means while maintaining the wound strand in the elongated condition due to the tensional winding, after the winding of the strand is completed tensionally relieving the wound strand to return it to substantially its original length through contraction of its cylindrically wound form by limited retraction of the internal support means of the sleeve and proportional collapse of the sleeve, providing longitudinally positioned depressed areas in the internal support means for receipt of thickened portions of the sleeve to accommodate the sleeve to its reduced cylindrical shape, and finally removing the wound strand and sleeve from the support means.
5. A method according to claim 4 in which the tube is creped or wrinkled before it is tautly stretched.
6. A method according to claim 4 in which the tube is of fibrous composition.
7. A method according to claim 6 in which the tube is composed of paper stock.
Description:
The present invention relates generally to apparatus and methods for drawing and winding a strand of continuous glass filaments. More specifically the invention pertains to a mandrel for holding a tube upon which such a fibrous glass strand is wound into a package and a method of utilizing such a mandrel in conjunction with a collapsible tube.
Because of the inherent greater tensile strength of a fibrous glass strand, its elastic elongation under tensile forces, and the speed with which it has been customarily wound upon spools or tubes, a greater compression force is developed in the winding operation than accompanies that of strands of other filaments of natural or synthetic origin.
This accumulated high compression force in the completely wound package has the objectionable effect of constricting the packaging tube into a smaller diameter. This constricting force may make it difficult to remove the tube from the mandrel. It also is inclined to bind the turns of the glass strand so tightly together around the tube that the unwinding operation for subsequent use or treatment of the strand, such as twisting and plying, is unsatisfactory.
A resilient plastic tube which is expandable while the strand is being wound and then returns to a reduced diameter has worked quite effectively in relieving the tension of the wound strand and releasing the strand quite freely in later unwinding operations of the strand from the tube.
A mandrel that has served well in carrying such plastic tubes is shown in U.S. Pat. No. 2,891,798 granted to R. E. Smith on June 23, 1959.
In this device, there are long narrow fingers, loosely carried by the mandrel. These are thrust outwardly against the interior surface of the packaging tube by the centrifugal force developed by the rotation of the mandrel in the winding process and expands the tube. This centrifugal force counters the constricting effect of the winding of the strand upon the expanded tube during the winding operation.
With the termination of the winding operation and the attendant rotation of the mandrel, the centrifugal force is nullified and the tube is then free to contract under the constricting stress of the wound strand and to return to its original diameter. The tube is still loose enough upon the mandrel to be easily removed. Also, the expanded form of the tube during rotation of the mandrel and the return of the tube to its original size at the termination of the rotation reduces the binding between turns of the strand whereby subsequent unwinding of the strand from the tube is smoothly effected.
While mandrels of the Smith design and plastic tubes served quite efficiently for many years, recently, under more demanding requirements it has become desirable to make improvements therein.
Under the repeated, alternate expansion and contraction the plastic tubes may become misshaped. Much more disruptive and hazardous is a tendency of the tubes to occasionally explode under the buildup of internal stresses.
Another objection to these tubes is their comparatively high cost in the severely competitive textile industry.
It is accordingly the principal purpose of this invention to provide a mandrel designed particularly for carrying a tube not subject to injurious warping or explosion and also adapted to cooperate with the variations in tube diameters required in effectively winding a glass strand upon the tube and the satisfactory unwinding of the strand therefrom.
A further object of the invention is a mandrel suitable for use with a collapsible tube composed of material which does not possess substantial elasticity or rigidity.
These and other objects and advantages of the invention are attained largely through the provision of a mandrel, the fingers of which have depressed zones in their conventional arcuate outer surfaces which bear against the inner surface of the tube and the use of a collapsible, wrinklable tube, portions of which may gather in such depressed zones to effect an overall reduction in the diameter of the tube. The depressed zones may encompass tapered indented edges of the fingers which have the additional function of minimizing pinching of the tube between the fingers.
The successful performance of the invention is further advanced through the use of a tube which returns to its original diameter through straightening of its collapsed portions under outward thrust of the fingers of the mandrel.
The principal features and other characteristics of the invention will be brought out more clearly in the following description with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic illustration of a conventional apparatus for forming and winding a glass strand into a package;
FIG. 2 is a perspective view of one of the fingers of the mandrel on which the packaging tube is mounted;
FIG. 3 is an end view of the mandrel;
FIG. 4 is a side elevational view thereof;
FIG. 5 is a partial sectional view of the mandrel taken on line 5--5 of FIG. 4 showing three adjoining fingers in their most outwardly extended position;
FIG. 6 is a similar partial sectional view of the mandrel with the packaging tube shown thereon and the fingers slightly depressed under the tube;
FIG. 7 is the same sectional view of the mandrel showing a preliminary portion of a strand wound on the packaging tube; and
FIG. 8 is a like sectional view of the mandrel on which a full package of the strand has been collected, and shows the collapsed portions of the tube after rotation of the mandrel has been terminated and the compressive force of the wound strand has constricted the tube.
Referring to the drawings in more detail, in FIG. 1 is depicted diagrammatically a molten glass feeding bushing 12 with outlet nipples 14 projecting downwardly therefrom. Issuing from the outlet nipples 14, generally 200 to 400 in number, are small streams of molten glass which are attenuated into filaments 16. The filaments are drawn downwardly by the rotation of the mandrel 18 of the winding mechanism 20. Not far below the bushing 12 the filaments 16 are coated with a size by the applicator 24 and are then brought together to form strand 26 by the gathering action of the grooved shoe 25.
A traversing device 27 of conventional design diagrammatically depicted reciprocates the strand 26 back and forth longitudinally of the surface of the packaging tube 22 mounted on the mandrel 18. The flanged tube holding fingers 29 of the mandrel have their lower ends lodged in dove tail slots 31 extending longitudinally of the body 32 of the mandrel 18 for substantially the full length thereof and are radially locked in the slots by their dove tail shaped lower portions and longitudinally by end cap 33 and retaining ring 35.
The mandrel 18 is secured to the tapered motor spindle 37, fragmentarily shown in FIG. 4, which extends outwardly from the housing of the winding mechanism 20. A member 38 encircles the spindle 37 and includes bearings to support the spindle and mandrel.
Two annular sets of springs 39 individually located in wells 40 near opposite ends of the slots as shown in FIG. 4 bear against the bottom of the fingers 29 to propel them to the outward limit of their radial movement as shown in FIG. 5. In this extreme position of the fingers 29 the flared sides of the fingers abut against the converging tapered portions of the slots 31.
In the embodiment of the invention herein disclosed the mandrel is approximately 22 inches long and there are 12 fingers. With the fingers extended the diameter of the mandrel is approximately 6 36/100 of an inch. The outer flanged portions of the fingers are sufficiently broad to together constitute a continuous circumferential surface around the mandrel when the fingers are depressed to the limit of their inward movement within the slots 31.
In FIG. 6 a packaging tube 22 has been placed on the mandrel with a slight depression of the fingers 29 against the thrust of the springs 39. The spring tension retains the tube in position until rotation of the mandrel is initiated and is not sufficient to impede later removal of the tube.
Before the winding drive is actuated to turn the mandrel with the tube mounted on it, the starting end of the glass strand is manually tied around the tube. With the glass strand thus secured to the tube the winding drive is set in operation. This may be accomplished through release of a clutch which has been held in drive-disengaging position by the foot of the operator while he placed the tube on the mandrel and fastened the leading end of the glass strand around the tube. As the tube accelerates to its selected speed (which may be 10,000 revolutions per minute) the fingers are propelled by centrifugal force outwardly against the interior of the tube.
Under the high rotational speed of the mandrel the weight of the fingers brings considerable centrifugal force to bear against the inner surface of the tube and holds it in a taut condition. For larger packages of the strand, fingers of chrome plated stainless steel are desirable for generating greater force. Aluminum fingers serve satisfactorily for small packages.
One type of packaging tube adaptable to the practice of this invention has in its original form its greatest diameter such as the tube shown placed on the mandrel in FIG. 6. This tube may have two or three plies and be composed of a paper or other fibrous base strengthened sufficiently with a size or binder to make it substantially non-stretchable while retaining considerable flexibility. One tube of this type which has performed well has an inner diameter of approximately 61/3 inches and a wall thickness of 0.030 of an inch.
In FIG. 7 a portion of the mandrel with the tube 22 thereon is pictured under rotation wherein the winding of the strand 26 on the tube has been started with the attendant continuous drawing of the filaments 16 from the bushing 12 and their gathering into the strand 26. The traversing device 27 evenly distributes the strand back and forth over the length of the tube.
The high rotational speed of the mandrel applies such a pulling tension on the strand being collected that the strand is stretched to a substantial proportion of the approximately 3 percent limit in its estimated possible inherent elastic elongation. This extension in length of the strand is retained while the strand is wound.
Due to the strength of the strand and its substantially ideal elastic characteristics a considerable compressive force against the tube is developed. However, the weight of the fingers and the speed of rotation have been predeterminately correlated to generate sufficient centrifugal force against the tube to hold the tube against the opposing centripetal force of the strand.
There is some indication that a slight stretching of the tube may occur due to the compression or squeezing of the tube between the opposing centrifugal and centripetal forces. Any thinning and lateral extension of the tube resulting therefrom would be relieved by thickening or wrinkling of the tube portions disposed above the grooves 43 and the tapered edges 45 of the fingers 29.
The major contraction of the tube is effected when the packaging of the strand upon the tube has been completed and the rotation of the mandrel has been terminated. Then the strand through its inherent elasticity tends to shorten to its original length. Its previous elongation under the pulling force of the rotation may vary within an approximate range between 11/2 and 3 percent dependent upon the rotational speed of the mandrel, the length of the winding operation, and the glass composition. Both greater winding speed and a long winding period increase the elongation.
In FIG. 8, the packaging of the strand 26 has been completed and rotation of the mandrel 18 brought to a stop. As there depicted the tube 22 has been constricted about 2 percent of its diameter by the shortening of the strand to its normal length from the elongation effected by the winding process. In extreme cases the desired reduction in the diameter of the tube may be as high as 6 percent.
The fingers 29 are shown depressed somewhat above the limit of their inward movement which in this embodiment is set by abutment of adjacent edges of the fingers. This inward limit could also be determined in mandrels of alternate design by the inward ends of the fingers reaching the bottom of the slots 31 or the bottom of the finger flanges seating upon the flat lands of the mandrel body 32.
The corresponding reduction in the diameter of the tube 22 is achieved through collapsing of the tube portions above the longitudinal center grooves 43 and the indented tapered edges 45 of the fingers which together constitute in this instance about one-third of the outer faces of the fingers. In the spaces provided by the grooves and tapered edges the surplus tube portions are gathered in wrinkled form as indicated at 22c. While the basic nature of the fibrous composition of the tubes supports such wrinkling, the humid atmosphere in the winding zone is a facilitating factor.
The easing of the tension of the strand accompanying the reduction in diameter enables the packaged tube to be removed from the mandrel and subsequent facile feeding of the strand from the tube in plying and twisting processes.
In addition to the actual elastic elongation of the strand during the winding process, the filaments of the strand are straightened and brought tightly together by the pulling force in opposition to any individual tendency to variously curl. This may effect elongation of the strand beyond the 3 percent of pure elastic elongation. The strand may also be considered to be unnaturally curved about the tube and to have some propensity to straighten.
Accordingly, there are believed to be subsidiary stresses in the strand which are eased through the reduction in diameter of the tube and the elimination of which facilitates unwinding of the strand.
The new reduced diameter of the tube is retained until it is used again. Any moisture absorbed by it during the original winding operation is lost during storage or subsequent drawing of the strand from the tube.
Under the centrifugal thrust of the fingers in the next strand packaging operation the tube is expanded to its original diameter.
Instead of starting with a smooth surface tube, one manufactured with an initial creped form may be utilized. The creping should be controlled to permit at least a 3 percent increase in diameter. When such a tube is first placed on the mandrel it would depress the fingers to an extent comparable to that of the fingers in FIG. 8 and then through action of the fingers would be expanded to a diameter of the tube depicted in FIG. 6. When later collapsed the creping of the tube would be concentrated in the spaces of the grooves 43 and tapered edges 45.
The various features which contribute to the success of the invention include fingers with outer flanges which cover as completely as possible the full periphery of the mandrel and thus provide a minimum space between the fingers for entry of portions of the tube when under collapsing pressure. Such entry not only may jam the fingers preventing their depression but also may allow portions of the tube to be gripped between adjacent fingers and consequently prevent removal of the tube from the mandrel.
The principal feature of the mandrel of this invention is the provision of depressed areas in which excess portions of the tube may be gathered to accommodate the required reduction in the diameter of the tube.
While a center groove and tapered edges are preferred for establishing gathering areas, depressed areas of other forms and extent may be just as effective. Such areas should run fairly uniformly lengthwise of the fingers and be regularly spaced circumferentially of the mandrel.
Alternate forms may include two offset smaller grooves in place of the single center groove. A series of spherical depressions or of short grooves, or combinations thereof.
In addition to providing gathering space for wrinkling portions of the tube, as noted above, the tapered edges have the further important function of reducing the possibility of the tube being pinched between the edges of adjoining fingers. In some instances tapered edges alone may serve the full purpose of the invention.
In summary it may be observed that the invention involves a mandrel of a special structure adapted for allowing shrinkage of a tube of a non-resilient or inelastic material and a method utilizing such a mandrel with a tube of the stated nature.
Various modifications and substitutions in the particular apparatus and method here chosen for purposes of disclosure and explanation may occur to those skilled in the arts involved without departing from the spirit of the invention and the scope of the accompanying claims.
Because of the inherent greater tensile strength of a fibrous glass strand, its elastic elongation under tensile forces, and the speed with which it has been customarily wound upon spools or tubes, a greater compression force is developed in the winding operation than accompanies that of strands of other filaments of natural or synthetic origin.
This accumulated high compression force in the completely wound package has the objectionable effect of constricting the packaging tube into a smaller diameter. This constricting force may make it difficult to remove the tube from the mandrel. It also is inclined to bind the turns of the glass strand so tightly together around the tube that the unwinding operation for subsequent use or treatment of the strand, such as twisting and plying, is unsatisfactory.
A resilient plastic tube which is expandable while the strand is being wound and then returns to a reduced diameter has worked quite effectively in relieving the tension of the wound strand and releasing the strand quite freely in later unwinding operations of the strand from the tube.
A mandrel that has served well in carrying such plastic tubes is shown in U.S. Pat. No. 2,891,798 granted to R. E. Smith on June 23, 1959.
In this device, there are long narrow fingers, loosely carried by the mandrel. These are thrust outwardly against the interior surface of the packaging tube by the centrifugal force developed by the rotation of the mandrel in the winding process and expands the tube. This centrifugal force counters the constricting effect of the winding of the strand upon the expanded tube during the winding operation.
With the termination of the winding operation and the attendant rotation of the mandrel, the centrifugal force is nullified and the tube is then free to contract under the constricting stress of the wound strand and to return to its original diameter. The tube is still loose enough upon the mandrel to be easily removed. Also, the expanded form of the tube during rotation of the mandrel and the return of the tube to its original size at the termination of the rotation reduces the binding between turns of the strand whereby subsequent unwinding of the strand from the tube is smoothly effected.
While mandrels of the Smith design and plastic tubes served quite efficiently for many years, recently, under more demanding requirements it has become desirable to make improvements therein.
Under the repeated, alternate expansion and contraction the plastic tubes may become misshaped. Much more disruptive and hazardous is a tendency of the tubes to occasionally explode under the buildup of internal stresses.
Another objection to these tubes is their comparatively high cost in the severely competitive textile industry.
It is accordingly the principal purpose of this invention to provide a mandrel designed particularly for carrying a tube not subject to injurious warping or explosion and also adapted to cooperate with the variations in tube diameters required in effectively winding a glass strand upon the tube and the satisfactory unwinding of the strand therefrom.
A further object of the invention is a mandrel suitable for use with a collapsible tube composed of material which does not possess substantial elasticity or rigidity.
These and other objects and advantages of the invention are attained largely through the provision of a mandrel, the fingers of which have depressed zones in their conventional arcuate outer surfaces which bear against the inner surface of the tube and the use of a collapsible, wrinklable tube, portions of which may gather in such depressed zones to effect an overall reduction in the diameter of the tube. The depressed zones may encompass tapered indented edges of the fingers which have the additional function of minimizing pinching of the tube between the fingers.
The successful performance of the invention is further advanced through the use of a tube which returns to its original diameter through straightening of its collapsed portions under outward thrust of the fingers of the mandrel.
The principal features and other characteristics of the invention will be brought out more clearly in the following description with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic illustration of a conventional apparatus for forming and winding a glass strand into a package;
FIG. 2 is a perspective view of one of the fingers of the mandrel on which the packaging tube is mounted;
FIG. 3 is an end view of the mandrel;
FIG. 4 is a side elevational view thereof;
FIG. 5 is a partial sectional view of the mandrel taken on line 5--5 of FIG. 4 showing three adjoining fingers in their most outwardly extended position;
FIG. 6 is a similar partial sectional view of the mandrel with the packaging tube shown thereon and the fingers slightly depressed under the tube;
FIG. 7 is the same sectional view of the mandrel showing a preliminary portion of a strand wound on the packaging tube; and
FIG. 8 is a like sectional view of the mandrel on which a full package of the strand has been collected, and shows the collapsed portions of the tube after rotation of the mandrel has been terminated and the compressive force of the wound strand has constricted the tube.
Referring to the drawings in more detail, in FIG. 1 is depicted diagrammatically a molten glass feeding bushing 12 with outlet nipples 14 projecting downwardly therefrom. Issuing from the outlet nipples 14, generally 200 to 400 in number, are small streams of molten glass which are attenuated into filaments 16. The filaments are drawn downwardly by the rotation of the mandrel 18 of the winding mechanism 20. Not far below the bushing 12 the filaments 16 are coated with a size by the applicator 24 and are then brought together to form strand 26 by the gathering action of the grooved shoe 25.
A traversing device 27 of conventional design diagrammatically depicted reciprocates the strand 26 back and forth longitudinally of the surface of the packaging tube 22 mounted on the mandrel 18. The flanged tube holding fingers 29 of the mandrel have their lower ends lodged in dove tail slots 31 extending longitudinally of the body 32 of the mandrel 18 for substantially the full length thereof and are radially locked in the slots by their dove tail shaped lower portions and longitudinally by end cap 33 and retaining ring 35.
The mandrel 18 is secured to the tapered motor spindle 37, fragmentarily shown in FIG. 4, which extends outwardly from the housing of the winding mechanism 20. A member 38 encircles the spindle 37 and includes bearings to support the spindle and mandrel.
Two annular sets of springs 39 individually located in wells 40 near opposite ends of the slots as shown in FIG. 4 bear against the bottom of the fingers 29 to propel them to the outward limit of their radial movement as shown in FIG. 5. In this extreme position of the fingers 29 the flared sides of the fingers abut against the converging tapered portions of the slots 31.
In the embodiment of the invention herein disclosed the mandrel is approximately 22 inches long and there are 12 fingers. With the fingers extended the diameter of the mandrel is approximately 6 36/100 of an inch. The outer flanged portions of the fingers are sufficiently broad to together constitute a continuous circumferential surface around the mandrel when the fingers are depressed to the limit of their inward movement within the slots 31.
In FIG. 6 a packaging tube 22 has been placed on the mandrel with a slight depression of the fingers 29 against the thrust of the springs 39. The spring tension retains the tube in position until rotation of the mandrel is initiated and is not sufficient to impede later removal of the tube.
Before the winding drive is actuated to turn the mandrel with the tube mounted on it, the starting end of the glass strand is manually tied around the tube. With the glass strand thus secured to the tube the winding drive is set in operation. This may be accomplished through release of a clutch which has been held in drive-disengaging position by the foot of the operator while he placed the tube on the mandrel and fastened the leading end of the glass strand around the tube. As the tube accelerates to its selected speed (which may be 10,000 revolutions per minute) the fingers are propelled by centrifugal force outwardly against the interior of the tube.
Under the high rotational speed of the mandrel the weight of the fingers brings considerable centrifugal force to bear against the inner surface of the tube and holds it in a taut condition. For larger packages of the strand, fingers of chrome plated stainless steel are desirable for generating greater force. Aluminum fingers serve satisfactorily for small packages.
One type of packaging tube adaptable to the practice of this invention has in its original form its greatest diameter such as the tube shown placed on the mandrel in FIG. 6. This tube may have two or three plies and be composed of a paper or other fibrous base strengthened sufficiently with a size or binder to make it substantially non-stretchable while retaining considerable flexibility. One tube of this type which has performed well has an inner diameter of approximately 61/3 inches and a wall thickness of 0.030 of an inch.
In FIG. 7 a portion of the mandrel with the tube 22 thereon is pictured under rotation wherein the winding of the strand 26 on the tube has been started with the attendant continuous drawing of the filaments 16 from the bushing 12 and their gathering into the strand 26. The traversing device 27 evenly distributes the strand back and forth over the length of the tube.
The high rotational speed of the mandrel applies such a pulling tension on the strand being collected that the strand is stretched to a substantial proportion of the approximately 3 percent limit in its estimated possible inherent elastic elongation. This extension in length of the strand is retained while the strand is wound.
Due to the strength of the strand and its substantially ideal elastic characteristics a considerable compressive force against the tube is developed. However, the weight of the fingers and the speed of rotation have been predeterminately correlated to generate sufficient centrifugal force against the tube to hold the tube against the opposing centripetal force of the strand.
There is some indication that a slight stretching of the tube may occur due to the compression or squeezing of the tube between the opposing centrifugal and centripetal forces. Any thinning and lateral extension of the tube resulting therefrom would be relieved by thickening or wrinkling of the tube portions disposed above the grooves 43 and the tapered edges 45 of the fingers 29.
The major contraction of the tube is effected when the packaging of the strand upon the tube has been completed and the rotation of the mandrel has been terminated. Then the strand through its inherent elasticity tends to shorten to its original length. Its previous elongation under the pulling force of the rotation may vary within an approximate range between 11/2 and 3 percent dependent upon the rotational speed of the mandrel, the length of the winding operation, and the glass composition. Both greater winding speed and a long winding period increase the elongation.
In FIG. 8, the packaging of the strand 26 has been completed and rotation of the mandrel 18 brought to a stop. As there depicted the tube 22 has been constricted about 2 percent of its diameter by the shortening of the strand to its normal length from the elongation effected by the winding process. In extreme cases the desired reduction in the diameter of the tube may be as high as 6 percent.
The fingers 29 are shown depressed somewhat above the limit of their inward movement which in this embodiment is set by abutment of adjacent edges of the fingers. This inward limit could also be determined in mandrels of alternate design by the inward ends of the fingers reaching the bottom of the slots 31 or the bottom of the finger flanges seating upon the flat lands of the mandrel body 32.
The corresponding reduction in the diameter of the tube 22 is achieved through collapsing of the tube portions above the longitudinal center grooves 43 and the indented tapered edges 45 of the fingers which together constitute in this instance about one-third of the outer faces of the fingers. In the spaces provided by the grooves and tapered edges the surplus tube portions are gathered in wrinkled form as indicated at 22c. While the basic nature of the fibrous composition of the tubes supports such wrinkling, the humid atmosphere in the winding zone is a facilitating factor.
The easing of the tension of the strand accompanying the reduction in diameter enables the packaged tube to be removed from the mandrel and subsequent facile feeding of the strand from the tube in plying and twisting processes.
In addition to the actual elastic elongation of the strand during the winding process, the filaments of the strand are straightened and brought tightly together by the pulling force in opposition to any individual tendency to variously curl. This may effect elongation of the strand beyond the 3 percent of pure elastic elongation. The strand may also be considered to be unnaturally curved about the tube and to have some propensity to straighten.
Accordingly, there are believed to be subsidiary stresses in the strand which are eased through the reduction in diameter of the tube and the elimination of which facilitates unwinding of the strand.
The new reduced diameter of the tube is retained until it is used again. Any moisture absorbed by it during the original winding operation is lost during storage or subsequent drawing of the strand from the tube.
Under the centrifugal thrust of the fingers in the next strand packaging operation the tube is expanded to its original diameter.
Instead of starting with a smooth surface tube, one manufactured with an initial creped form may be utilized. The creping should be controlled to permit at least a 3 percent increase in diameter. When such a tube is first placed on the mandrel it would depress the fingers to an extent comparable to that of the fingers in FIG. 8 and then through action of the fingers would be expanded to a diameter of the tube depicted in FIG. 6. When later collapsed the creping of the tube would be concentrated in the spaces of the grooves 43 and tapered edges 45.
The various features which contribute to the success of the invention include fingers with outer flanges which cover as completely as possible the full periphery of the mandrel and thus provide a minimum space between the fingers for entry of portions of the tube when under collapsing pressure. Such entry not only may jam the fingers preventing their depression but also may allow portions of the tube to be gripped between adjacent fingers and consequently prevent removal of the tube from the mandrel.
The principal feature of the mandrel of this invention is the provision of depressed areas in which excess portions of the tube may be gathered to accommodate the required reduction in the diameter of the tube.
While a center groove and tapered edges are preferred for establishing gathering areas, depressed areas of other forms and extent may be just as effective. Such areas should run fairly uniformly lengthwise of the fingers and be regularly spaced circumferentially of the mandrel.
Alternate forms may include two offset smaller grooves in place of the single center groove. A series of spherical depressions or of short grooves, or combinations thereof.
In addition to providing gathering space for wrinkling portions of the tube, as noted above, the tapered edges have the further important function of reducing the possibility of the tube being pinched between the edges of adjoining fingers. In some instances tapered edges alone may serve the full purpose of the invention.
In summary it may be observed that the invention involves a mandrel of a special structure adapted for allowing shrinkage of a tube of a non-resilient or inelastic material and a method utilizing such a mandrel with a tube of the stated nature.
Various modifications and substitutions in the particular apparatus and method here chosen for purposes of disclosure and explanation may occur to those skilled in the arts involved without departing from the spirit of the invention and the scope of the accompanying claims.