APPARATUS AND METHOD OF KNITTING MATERIAL INTO A CIRCULAR TUBE

Information

  • Patent Application
  • 20200255990
  • Publication Number
    20200255990
  • Date Filed
    February 12, 2019
    5 years ago
  • Date Published
    August 13, 2020
    3 years ago
Abstract
The field of the present invention relates, in general, to apparatus and methods of knitting a material into a tubular form, where the length of such tubular form is not dictated by conventional distances between the knitting areas and the catch basins of integrated machines. In short, this invention increases the distal relationship between the needle-equipped element, which performs the knitting function, and the basin that catches the resulting tubular form of the material. The basin rotates synchronized with the rotation of the resulting tubular form. The separation facilitates the continuous production of a length of the resulting tubular form of the material. The tubular form thus can be longer than such length where, as taught in the prior art, the catch basin is fixed—as part of integrated machines—in close proximity with the element that performs the knitting. As an inventive method, the steps include (A) feeding such material into the proximity of a needle-equipped element; (B) knitting such material with such needle-equipped element to produce such resulting tubular form; (C) catching such resulting tubular form in a basin that is physically disconnected from the needle-equipped element and distanced therefrom to produce a desirably longer length of the resulting tubular form; and (D) electronically controlling such feeding step, such knitting step, and such catching step (synchronizing the catching with the rotation of resulting tubular form), whereby the rates of the feeding, knitting and catching produce such resulting tubular form that is unbuckled.
Description
BACKGROUND

Traditional circular knitting machines have built-in catch basins. Often, these basins are a roller-style collection mechanism or a simple basket. In order to prevent twisting and damage to the resulting tubular product produced by such an apparatus, the basin is preferably rotated synchronously with the tubular product it is catching (and with the knitting element remaining fixed) and the material to be knitted is introduced vertically in proximity to the knitting element while such material is simultaneously rotated, while knitted. The moving of the basin in concert with the rotation of the material (and thus with the rotation of the resulting tubular product) facilities production of a product with a more desirable and consistent knitting pattern.


An inherent limitation in traditional apparatuses, however, is the physical connection between the knitting element and the basin. This physical connection tends to enhance the coordinated operation of the entire apparatus, including, among other things, the synchronization of the rotating resulting tubular product and the rotating catch basin. The ‘oneness’ of such traditional apparatus, however, limits the total amount of material that can be knitted in a single piece of resulting tubular product. The limitation arises from the fixed distance between the knitting elements and the attached catch basin.


The prior art discloses various apparatuses in the field of knitting tubes, but none of the prior art references, clearly discloses or suggests apparatuses and/or methods of producing runs of resulting tubular product that are not limited or otherwise predicated upon the physical connection between the knitting apparatus and the catch basin and the distance therebetween. For example, the Moretta patent (U.S. Pat. No. 799,636) focuses upon a tensioning device for knitting machines, with the noted material being hosiery. The tensioning is accomplished by grabbing the material and pulling it downward but the length, which for hosiery would be relatively short, is dictated by the ‘built-in’ distance between the plurality of needles and length of the cylinder in which the product is produced. The Fleisher patent (U.S. Pat. No. 2,238,560) discloses a napping machine (with elements positioned on three separate floors of a building) and a process through which the material is fed from the bottom up. The length of the tubular fabric produced is limited to the fixed and physically connected locations of the fabric supply mechanism on the lower floor of a building, the napping mechanism on a middle floor, and the fabric take-up on an upper floor. The Brooks patent (U.S. Pat. No. 2,481,718) focuses on attachments for a knitting machine and not on the primary operable elements. Like the Fleisher patent, the finished product from the operation of the Brooks device is drawn upward. The Ducol patent (U.S. Pat. No. 4,314,462) discloses the transitioning of a tube of a material from an annular cross section to a flattened straight cross section. Accordingly, the focus of this patent is alignment and not length. The final example herein, the Quay patent (U.S. Pat. No. 6,601,412), focuses upon the means of guiding fabric downward and away from a needle cylinder but does not address the limitations on the length of the resulting tubular product.


Consequently, none of the cited prior art discloses or appears to suggest a device or method where the length of the resulting tubular product is not limited or otherwise dictated by the physical connection between the knitting element and the catch basin. Barring such limitation, the catch basin could be positioned arbitrarily distant from the knitting element. The catch basin could also therefor be arbitrarily tall and/or wide. Depending on the tensile strength and other properties of the resulting tubular product, one could even put the catch basin a great distance below the knitting element (for example, the length of the resulting tubular product could extend to distances limited only by the point at which the resulting tubular product would tear under its own weight).


SUMMARY OF THE INVENTION

The object of the present invention is to address the limitation inherently imposed upon the length of the resulting tubular product by the physical attachment of a basin to the structure that holds a knitting element. Accordingly, the present invention comprises an apparatus and a method of knitting a material into a tubular form, where the length of such tubular form is not dictated by conventional distances between the knitting areas and the catch basins of integrated machines.


One of the unique features of one embodiment of the present invention is the increased distal relationship between the needle-equipped element, which performs the knitting function, and the basin that catches the resulting tubular form of the material. Unlike conventional apparatuses—in which the basin is more typically in close proximity with the element that performs the knitting function, the present inventive apparatus has lengthened separation between the needle-equipped element and the basin, accompanied by a control system that monitors and manages, among other things, the knitting rate and the rotation of the basin. This separation facilitates the continuous production of a length of the resulting tubular form of the material that can be longer than such length where, as taught in the prior art, the catch basin is fixed—as part of integrated machines—in close proximity with the element that performs the knitting.


In one embodiment of the present invention, the apparatus, more specifically, includes a housing that holds a needle-equipped element, which produces the resulting tubular form of the material. The housing also has mounted, in proximity to its top, a feeder system, through which the material can be rotationally fed to be knitted by the needle-equipped element. A motor system powers the needles and the feeder through mechanical connections. A control system electronically coordinates not only the feeder system's rate of feeding and the needle-equipped element's rate of knitting, but also coordinates the rotation of the basin, even though the basin is not physically connected to the housing and is rotated by a separate means.


In other embodiments of the present inventive apparatus, the resulting tubular form is captured in an unbuckled configuration and the variability in the maximum length of the resulting tubular form producible in one run primarily dictated by (x) the distance between the needle-equipped element and the basin and (y) the length of the resulting tubular form that would result in a tear thereof due to its weight. In still other embodiments, (A) the combination of the feeder system and the needle-equipped element is configured and structured to hold the weight of the resulting tubular form, (B) the housing also has connected thereto at least one roller to guide the resulting tubular form away from such needle-equipped element and toward such basin, (C) such control system is programmable to discontinue the operation of the apparatus at a predetermined point prior to the weight of the resulting tubular form causing a tear in such resulting tubular form, or (D) a combination of the foregoing exists. In other embodiments, the basin is physically connected to the housing, but the basin can also be moved vertically away from the housing, thereby accommodating the increasing length of such resulting tubular form as it is being produced.


The present inventive method of knitting a material into a resulting tubular form thereof comprises the steps of (A) feeding such material into the proximity of a needle-equipped element; (B) knitting such material with such needle-equipped element to produce such resulting tubular form; (C) catching such resulting tubular form in a basin that is physically disconnected from the needle-equipped element and distanced therefrom to produce a desirably longer length of the resulting tubular form; and (D) electronically controlling such feeding step, such knitting step, and such catching step, whereby the rates of the feeding, knitting and catching produce such resulting tubular form that is unbuckled.


In further embodiments of the present inventive method, the variability in the maximum length of the resulting tubular form producible is primarily dictated by (x) the distance between the location in which such material is knitted and the location such resulting tubular form is caught and (y) the length of the resulting tubular form that would result in a tear thereof due to its weight. The process could also be enhanced (A) by adding a step of guiding the resulting tubular form away from the location of the knitting and toward the location of the catching, (B) wherein the weight of the resulting tubular form is held in the location of the knitting and the feeding of the material is discontinued at a predetermined point prior to the weight of the resulting tubular form causing a tear in such resulting tubular form, or (C) a combination of the foregoing. The foregoing could also be further enhanced by including the step of guiding and holding, below the location of the knitting location, of the weight of the resulting tubular form. The efficiency of the method could also possibly be improved if the same motor system drives the feeding step and the knitting step, and such motor system rotates the basin that catches the resulting tubular form. Further, the length of the resulting tubular form produced could be increased by moving the basin vertically away from the housing during the production of the resulting tubular form.





SUMMARY OF THE FIGURES


FIG. 1 shows an embodiment of the present invention that is inclusive of the material feeder, the needle-equipped element a catch basin, a control system and other elements.



FIG. 2 focuses more particularly on the needle-equipped element, the resulting tubular form of the material being knitted, and the roller assembly.



FIG. 3 shows the elements of FIG. 2 with the addition of the detected catch basin, a guide and weights that help draw the guide vertically down as the resulting tubular is formed.



FIG. 4 shows a flow chart depicting the steps of the present inventive method inclusive feeding of the material, knitting, and catching the resulting tubular form in a basin with movement electronically controlled to be coordinated with the other functions.





DETAILED DESCRIPTION OF THE EMBODIMENTS


FIG. 1 shows an embodiment of the present inventive apparatus that is structured to knit material 118 in a circular configuration and thus produce resulting tubular form 150 from such material 118. The main supporting structure of this embodiment of the present invention is housing 100. One of ordinary skill in the art would know that housing 100 could take a multitude of forms and be constructed with a variety of materials and elements. For the purpose and operation of the present invention, housing 100 need only be configured to position needle-equipped element 112 in a desirable location.


Needle-equipped element 112 is capable of knitting such material 118, producing such resulting tubular form 150. The type, number, positioning and other aspects of needle-equipped element may vary with the specifics of the operation and the type of material to be knitted. In the embodiment shown, needle-equipped element 112 includes a ring in which individual needles may be housed.


At the top housing 100 are the operable elements of feeder system 114. In this particular embodiment, the base of feeder system 114 sits on the top of and is connected to housing 100. The elements of feeder system 114 meet and manage the flow of the material 118, such that material 118 can be rotated when it comes into contact with needle-equipped element 112. The most notable parts of feeder system 114 are rollers 116, which guide material 118 into proximity of needle-equipped element 112. One of ordinary skill in the art would know that there are a number of designs and configurations of feeder system 114 that can provide the desired functions.


In this particular embodiment, motor system 120 is sized to provide the power need to operate various elements of this embodiment. One or ordinary skill in the art would understand the variety of options regarding the specifics of motor system 120—given its intended use. FIG. 1 also shows gear system 122 (for driving feeder system 114) through belt 124. Additional, gear system 126 (for driving needle-equipped element 112) through belt 128 is also shown. The combination of gear system 122 and belt 124 is an example of one means for mechanically connecting a powering source (such, for example, motor system 120) to, and thereby serve as the means to drive the desired operation of, feeder system 114. In parallel, the combination of gear system 126 and belt 128 is one example of one means for mechanically connecting a powering source (such, for example, also motor system 120 in this case) to, and thereby serve as the means to drive the desired operation of, needle-equipped element 112.



FIG. 1 also shows control system 130. Control system 130 directs the operation of the primary operational components of the present invention. In this particular embodiment, control system 130 includes programmable functionality through which an operator can set conditions for, and execute the operation or, the inventive apparatus. The controllable paraments could relate to the operation as a whole, the operations of one or more specific elements, and other aspects of the present invention that it might be desirable for an operator to manage through such operator's input of data and/or have control system 130 manage through the evaluation of embedded data and external conditions.


Wire 132 is an example of a means for electronically connecting an element of the inventive apparatus, such as control system 130, to a powering system, such as motor system 120, to coordinate the operable rates and other functions of feeder system 114 and needle-equipped element 112, respectively. In this embodiment, their rate is controlled by single wire 132 with the varying of the rates and the operations being dictated by the properties of the respective gear systems 122 and 126, respectively. One of ordinary skill in the art would recognize the variance in the rates and other functions could alternatively be created by varying outputs of motor system 120 in powering feeder system 114 and needle-equipped element 112 (for example if the gears driving the elements were internal to the powering system, with the attached belts connected to the powering system moving at differing rates). One of ordinary skill would know that the electronic connection between, for example, control system 130 and motor system 120 could be wireless. Further, in another embodiment, there could separate powering systems for feeder system 114 and needle-equipped element 112. In such an instance, control system 130 could be programmed to communicate with each powering system separately, via two wires, one wire to one powering system and wirelessly to the other, wirelessly to both powering systems, or otherwise,


Basin 134 is shown as separate, detached and a distance from housing 100. In this particular embodiment, basin 134 is rotated by motor system 136, which moves basin 134 through extension 148. Motor system 136 also has attached to it receiver 138. It is signal 140, emitted from signal generator 142 connected to control system 130 that manages the rotational speed and other functions of basin 134. With the connection between control system 130 and motor system 120 and the connection between control system 130 and motor system 136, through signal 140, control system 130 can coordinate the rates, movements and other functions of the feeding, knitting and rotation of the operative elements. One of ordinary skill in the art would also realize that, depending on the configuration of the present invention, motor system 120, in lieu of motor system 136, could be used to power the rotation of basin 134.


Also, as shown in FIG. 1′s embodiment of the present invention, basin 134 can be moved vertically relative to housing 100. This movement is guided along tracks 144. In some embodiments of the present invention, there could be a physical connection between housing 100 and basin 134 through the opposing ends of tracks 144 or other means, but such a physical connection is not a necessary aspect for the construction and use of the present invention. Where there is such a physical connection, it is desirable that such physical connection facilitate the movement of basin 134 vertically toward and alternatively away from housing 100 thereby accommodating the length of resulting tubular form 150 to be produced.


With the distance between basin 134 and needle-equipped element 112 being variable (with basin 134 not being physically attached to housing 100), the length of resulting tubular form 150 that is producible is also variable. That said, there are other limitations to the maximum length of resulting tubular form 150. Such limitations include, for example, the tensile strength of resulting tubular form 150 (at what length might resulting tubular form 150 tear due to its own weight?). It is desirable to have resulting tubular form 150 captured by basin 134 unbuckled. It is also desirable to have control system 130, in an enhanced version of the present embodiment, receive input on the attributes of material 118, which, with information about the strength of the knitted connection of resulting tubular form 150, could be used to calculate the maximum length of resulting tubular form 150 producible in one run of the present inventive apparatus. Such information can be used, for example, to confirm that the optimal distance between needle-equipped element 112 and basin 134, mindful of the length of resulting tubular form 150 that would result in a tear thereof due to its weight. Accordingly, the combination of feeder system 114 and needle-equipped element 112 can be configured and structured to hold the weight of resulting tubular form 150 and control system 130 can be programmed to discontinue the operation of the present invention at a predetermined point prior to the weight of resulting tubular form 150 causing a tear therein.


One of ordinary skill in the art would also realize that the amount of material 118 that can be formed into a tube through the use of convention system may be increased, depending upon the characteristics of the material, by piling or stacking the material upon itself vertically following the knitting function. For example, there are existing machines with relatively small basins and with the desired result being maximally long tubes, that are supplemented in their production by operators stopping production periodically to manually force the piling up of the resulting tube in and above the basin (e.g., the operators apply downward forces on the material with rods to fit more material into and above the basin). In one such instance, the operators are producing, for example, 80 feet of tubing per batch when its preferable to produce 300 feet per batch and the application of the additional force allows the operator to produce a few more feet.


The same piling or stacking could be used in connection with the present inventive system to increase the length of the resulting tubular form 150 beyond, for example, the length dictated by the material's tensile strength. By way of example, when the leading end of resulting tubular form 150 reaches basin 134, depending upon the nature of material 118 (i.e., the main component of resulting tubular form 150) and the strength of the knitting, the user of present inventive system could allow the system to continue to run, causing resulting tubular form 150 to pile and stack. Accordingly, the maximum chance of tearing that is dictated by the unsupported weight of resulting tubular form 150 the point in time when resulting tubular form 150 first touches the bottom of basin 134 (note that as long as the whole pile resulting tubular form 150 is rotating there can be minimal, if any, twisting of resulting tubular form 150).


Further, if resulting tubular form 150 and its knitting are strong enough, additional downward force to be applied to resulting tubular form 150 to increase the length of resulting tubular form 150 produced between basin 134 and needle-equipped element 112. If and as necessary guides, walls or their equivalents could be employed to eliminate or at least minimize any undesirable horizontal displacement and/or overflow along the length of any portion of resulting tubular form 150. Also, as the pile of resulting tubular form 150 gets deeper, the effective unsupported length of resulting tubular form 150 below needle-equipped element 112 will decrease (i.e., resulting tubular form 150 could be in essence supporting itself until the point that there is no space for the production of any additional piled resulting tubular form 150).



FIG. 2 shows roller assembly 200. In one embodiment of the present invention, roller assembly 200 is positioned relatively close to and below needle-equipped element 202. As resulting tubular form 204 moves vertically down and away from needle-equipped element 202, resulting tubular form 204 is guided into contact with roller assembly 200. Depending on the characteristics of resulting tubular form 204, roller assembly 200 can be configured to, for example, assert pressure to the outside surface of resulting tubular form 204. As desired, such pressure could assist in supporting the weight of resulting tubular form 204. In a more enhanced version of this embodiment, roller assembly 200 could be driven by a motor so roller assembly 200 could apply its own supportive forces in holding and guiding resulting tubular form 204. Further, the motor driving roller assembly 200 could be electronically connected with a control system, whereby the rotation of roller assembly 200 could be coordinated with the movement of other elements of the embodiment (e.g., the needle-equipped element, the feeder, the basin, or a combination of the foregoing). Such coordination could lead to a more efficient and error-free production of resulting tubular form 204. One of ordinary skill in the art would also know that additional versions of roller assembly 200 or similar elements could be positioned along the path of resulting tubular form 204 to provide additional guidance and/or support along the path.



FIG. 3 shows guide 300. In this particular embodiment, guide 300 is a flexible material that is itself, in its unrolled configuration, a tube. As resulting tubular form 302 moves from needle-equipped element 304 toward basin 306, guide 300, which sits on roller assembly 308, unrolls. Weights 310, at the bottom end of guide 300, help to draw guide 300 vertically down as resulting tubular form 302, inside of guide 300, similarly moves vertically down. Accordingly, the internal surface area of guide 300 in contact with resulting tubular form 302 increases as guide 300 extends vertically (e.g., as the initial portion of resulting tubular form 302 moves from the needle-equipped element to the top of such basin and guide 300 increasing engulfs resulting tubular form 302). In some embodiments of the present invention, the edge of guide 300 can be extended to come into contact with such top of basin 306, thereby engulfing at least the initial portion of resulting tubular form 302 until it first enters such top of basin 306. In this particular embodiment of the present invention, guide 300 protects the outer surface of resulting tubular form 302 and provides some level of guidance toward basin 306. If roller assembly 308 is powered, then roller assembly 308 can be synchronized with the other elements of the present invention such that the extending of guide 300 will be coordinated with the operation of such other elements. Conversely or additionally, a powered roller assembly 308 could retract guide 300 to its pre-operative rolled position.



FIG. 4 shows a flow chart that depicts the present inventive method of knitting a material into a circular configuration, thereby producing a resulting tubular form. After the initial setup of the operations (e.g., sourcing and loading the material and configuring all of the elements of the knitting apparatus), the material is fed into the proximity of a needle-equipped element. The needle-equipped element knits the material to produce the resulting tubular form. A basin is used to catch the resulting tubular form. This basin, physically disconnected from the needle-equipped element and distanced therefrom, catches a desirably longer length of the resulting tubular form. The feeding step, such knitting step, and such catching step are all electronically controlled so that their respective rates and other operative functions are coordinated and the process thereby produces a resulting tubular form that is unbuckled and otherwise has desirable characteristics.


It is intended that, in the performance of this inventive method, the variability in the maximum length of the resulting tubular form producible is primarily dictated by (x) the distance between the location in which the material is knitted and the location such resulting tubular form is caught and (y) the length of the resulting tubular form that would result in a tear thereof due to its weight. The method can be enhanced by guiding the resulting tubular form away from the location of the knitting and toward the location of the catching. Conversely or additionally, the weight of the resulting tubular form can be held in the location of the knitting and the feeding of the material can be discontinued at a predetermined point prior to the weight of the resulting tubular form causing a tear in such resulting tubular form. More support can be provided for the resulting tubular form by guiding and holding its weight below the location of the knitting location.


In another embodiment of the present inventive method, the same motor system that drives the feeding step and the knitting step is also used to rotate the basin that catches the resulting tubular form. Another enhancement would be the guiding of the resulting tubular form from a location in proximity to the location of the knitting to a location in proximity to the top of the basin. In such a case, the element that provides such guiding could extend to come in contact with the top of the basin, such that at least the initial portion of the resulting tubular form could be engulfed until it first enters such top of such basin. Further, the basin could be moved vertically towards and away from the housing as the resulting tubular form is produced.

Claims
  • 1. An apparatus for knitting material in a circular configuration to produce of a resulting tubular form of the material comprising: a housing:a needle-equipped element within the housing that is capable of knitting the material to produce the resulting tubular form;a feeder system mounted in proximity of the top of the housing through which the material can be rotationally fed and be knitted by the needle-equipped element;a motor system;a control system;means for mechanically connecting the motor system to drive operation of the needle-equipped element;means for mechanically connecting the motor system to drive operation of the feeder system; andmeans for electronically connecting the control system to (a) the motor system to coordinate the feeder system's rate of feeding and (b) the motor system to coordinate the needle-equipped element's rate of knitting, so the rates can be coordinated with the rotation of the basin that is also dictated by the control system.
  • 2. The apparatus of claim 1 wherein the resulting tubular form captured by the basin is unbuckled and the variability in the maximum length of the resulting tubular form producible in one run of the apparatus is primarily dictated by (x) the distance between the needle-equipped element and the basin and (y) the length of the resulting tubular form that would result in a tear thereof due its weight.
  • 3. The apparatus of claim 1 further comprising at least one roller mounted in the housing to guide the resulting tubular form away from the needle-equipped element and toward the basin.
  • 4. The apparatus of claim 2 wherein (x) the combination of the feeder system and the needle-equipped element is configured and structured to hold the weight of the resulting tubular form and (y) the control system is programmable to discontinue the operation of the apparatus at a predetermined point prior to the weight of the resulting tubular form causing a tear in the resulting tubular form.
  • 5. The apparatus of claim 4 further comprising at least one roller that at least partially guides and holds the weight of the resulting tubular form.
  • 6. The apparatus of claim 1 wherein there is mechanical connection between the motor system and a means for rotating the basin.
  • 7. The apparatus of claim 3 further comprising at least one guide with a surface area that increases vertically as the initial portion of the resulting tubular form moves from the bottom of the housing to the top of the basin.
  • 8. The apparatus of claim 7 in which the edge of the guide can be extended to come into contact with the top of the basin, thereby engulfing the portion of the resulting tubular form until it first enters the top of the basin.
  • 9. The apparatus of claim 1 further comprising a physical connection between the housing and the basin.
  • 10. The apparatus of claim 9 wherein the physical connection facilitates the movement of the basin vertically away from the housing thereby accommodating the increasing length of the resulting tubular form as the resulting tubular form is being produced.
  • 11. A method of knitting a material into a circular configuration to produce of a resulting tubular form of the material comprising the steps of: feeding the material into the proximity of a needle-equipped element;knitting the material with the needle-equipped element to produce the resulting tubular form;catching the resulting tubular form in a basin that is physically disconnected from the needle-equipped element and distanced therefrom to produce a desirably longer length of the resulting tubular form;electronically controlling the feeding step, the knitting step, and the catching step, whereby the rates of the feeding, knitting and catching produce the resulting tubular form that is unbuckled.
  • 12. The method of claim 11 wherein the variability in the maximum length of the resulting tubular form producible is primarily dictated by (x) the distance between the location in which the material is knitted and the location the resulting tubular form is caught and (y) the length of the resulting tubular form that would result in a tear thereof due to its weight.
  • 13. The method of claim 11 further comprising the step of guiding the resulting tubular form away from the location of the knitting and toward the location of the catching.
  • 14. The method of 13 wherein the weight of the resulting tubular form is held in the location of the knitting and the feeding of the material is discontinued at a predetermined point prior to the weight of the resulting tubular form causing a tear in the resulting tubular form.
  • 15. The method of claim 13 further comprising the step of guiding and holding, below the location of the knitting location, of the weight of the resulting tubular form.
  • 16. The method of claim 11 wherein the same motor system drives the feeding step and the knitting step, and the motor system rotates the basin that catches the resulting tubular form.
  • 17. The method of claim 13 further comprising the step of guiding the resulting tubular form from a location in proximity to the location of the knitting to a location in proximity to the top of the basin.
  • 18. The method of claim 17 wherein the element that provides the guiding extends to come in contact with the top of the basin, that the resulting tubular form is engulfed until it first enters the top of the basin.
  • 19. The method of claim 11 further comprising the step of moving the basin vertically away from the housing as the resulting tubular form is produced.