Field of the Invention

The present invention relates to aluminum alloy tube or bobbin with internal knurling and manufacturing method thereof. More particularly, the present invention relates to an improved internal grip to avoid slippage and holding aluminum alloy tube or bobbin on the spindle for multifilament yarn winding application.

Background of the Invention

Spirally wound paperboard tubes or paper tubes are widely used in textile and other industries as cores for winding of filaments, yarns, and other materials such as films as they are produced. Although paperboard is relatively weak on a single layer basis, a tube constructed from multiple spirally wound paperboard layers can attain substantial strength. In the textile industry, yarn winding speeds have increased dramatically in recent years. Currently available textile winders are capable of operating at winding speeds of up to 8,000 meters/min. High winding speeds result in the application of significant forces to the textile cores as is well known in the art. For example, U.S. Pat. No. 3,980,249 to Cunning ham et al., issued in 1976, reported the phenomena of disintegrating and exploding high speed textile cores with winding speeds of 12,000 feet per minute (3660 meters/min). The significant increases in textile winding speeds since that time have worsened the known problems. The forces exerted on the textile cores particularly during start up of a high speed winding operation thus include compressive forces (head pressure) such as are exerted by contact between the drive land and the face of the textile core; shear and abrasive forces such as are exerted by the driven winding drum during initial acceleration of the textile core surface; tensile forces resulting from circumferential acceleration from rest to start-up speed; radially oriented stresses resulting from the centrifugal force generated by the high rotational speed of the textile core; and circumferential stresses caused by tube rotation.

Paperboard tubes are formed of layers which have been adhered together during the manufacturing process. And the paperboard forming each of these layers is an orthotropic material having properties in the lengthwise or machine direction (MD) that are different from the properties of the same paperboard in the widthwise or cross machine direction (CD) due to the tendency for more paper fibers to be aligned along the MD as compared to CD. In addition, paperboard strength properties in the direction perpendicular to the plane of the paper are less than those of the paperboard in either the MD or CD, also due to fiber alignment.

A multi-filament yarn is composed of a bundle of very thin, infinitely long threads. Multi-filament yarns contain a multitude of fine, continuous filaments (often 5 to 100 individual filaments) usually with some twist in the yarn to facilitate handling. Sizes range from 5-10 deniers up to a few hundred deniers. Polypropylene (PP) is a yarn raw material for a number of applications due to properties such as high tensile strength, low weight compared to other materials and its resistance against mildew and noxious effects of water. The multi-filament polypropylene yarn is manufactured on Multi-filament Spin-dr aw- wind lines. The machines are compact and flexible to meet the dynamic requirements of varied applications. The process includes the steps of spinning an undrawn yarn on a bobbin.

The yarn output of the Multifilament machine is normally carried out to accommodate 2 to 6 kg of yarn. The machines have normally two, four or eight yarn output positions depending on capacity of the machine. The yarns which are high and medium tenacity type are very strong and exert pressure on the yarn carrier.

Normally, the winding speed is up to 1500 meters/min. The capacity of the machine is called melt capacity which is up to 80 kg/hour. The Denier range is wide up to 5050 D and same is dependent on ultimate yarn application.

Presently the yarn carrier utilized is a paper tube. Paper tubes consist of paper or paperboard sheet layers wound together to form strong, hollow, and usually cylindrical shapes. The paper layers are laminated or bonded together using adhesives. The wall thickness of the tube can vary depending on the number of layers wrapped during manufacturing. Paper tubes are made from wound plies of paper or paperboard with inner dimension of 110mm (one hundred and ten millimeter). The outside diameter is generally 122mm with length of 280mm. Paper tubes or cores can be constructed from one, two or many plies of brown craft paper or paperboard. The innermost layer or ply, the liner, and the outermost layer, the wrap, can consist of different materials (foil, film, etc.) or specialized paper. The specialized paper and materials can provide water resistance, graphics or labeling, or a specific color. The paper tube weight is about 450 to 600 gm depending on type of paper and thickness of paper tube. The two main types of paper tubes and cores include spiral wound and convolute or parallel wound paper tubes. The paper tube is mounted on the winding head(spindle) where the tube is griped on circular springs, which are two in numbers and at a distance of about 30 mm from both the ends of spindle.

The paper tube wound with Polypropylene multifilament yarn is sent for further twisting and other processes. The unwounded paper tube is brought back to spin draw machine for winding the yarn again (reuse). Normally the weight of the wound yarn is 2 to 6 kg on each paper tube.

The paper tubes have certain drawbacks like paper tubes can absorb water and moisture in damp environments; the absorption of moisture or release of moisture can cause dimensional changes and distortion or warping Paper tubes as cores are not as strong. Paper can fray or tear over time. Core ends can experience "chew-out" after extended use and high loads.

Further the paper tube used for number of cycle is somewhat limited. Paper tubes are often damaged during shipment and/or winding of the yarn. It is observed that disfiguration of the tube may cause uneven rotation during yarn winding. Moisture absorption by the paper tube may also cause changes in dimension and other physical properties. Furthermore the paper tubes tend to create dust in the high friction environment.

In U.S. patent No. 3,756,530 by Miyaji Ito is directed to paper tube bobbin for treatment of yarn in cheese form and discloses a paper bobbin of a cylindrical or tubular form covered with a thin paper. This bobbin has grooves or one slit running along the length of the tube. This paper bobbin can be used for heat-treatment of yarn in cheese form. It collapses and contracts in its periphery length when a cheese is heated. The pressure caused by thermal shrinking of wound yarn causes the paper tube to collapse with ease. In the embodiment illustrated of this patent, paper tube bobbin is used for treatment of yarn.

The paper tube or paper bobbin normally gets affected during atmosphere with high humidity. This particularly happens during monsoon. The paper looses rigidity and the wound yarn gets affected. The yarn pressure on paper tube during humid atmosphere leads to collapse / de shaping of paper tube.

It is to be noted that when paper tube is mounted on the winding head (Spindle) it is required to slide over circular springs and thus while doing so, it has to be inserted with force/pressure which leads to damage to ends of the paper tube in terms of tearing and flattened expansion of ends. This hinders the proper unwinding of yarn from paper tube during further operation of yarn twisting. Thus paper tube loses its life. Also when yarn with a paper tube is transported, there is a chance for paper tube to get damaged. In general, paper tube has a life cycle of 2 to 4 rotations. The paper tube required higher storage space because it is bulky, scrapped and sold at regular interval.

Hence, to overcome above mentioned problems (paper tube ends damage, softening, de shaping due to humidity), it is desperately needed to invent a method of manufacturing aluminum alloy tube/bobbin for Polypropylene Multifilament yarn industry. The tube/bobbin is processed and produced in such a way that it can overcome aforesaid problems. The tube should be hard enough to sustain impact while inserting on the winding head (spindle), it should be strong enough to withstand winding load of High Tenacity Polypropylene multifilament yarn. It should also have features wherein it should have good grip with the springs to avoid slippage of tube/bobbin while the PP Multifilament Yarn is wound on the same.

Object of Invention

The main object of the present invention is to provide an aluminum alloy tube or bobbin with internal knurling for improved gripping and manufacturing method thereof.

The further object of the present invention is to provide aluminum alloy tube with inside and outside knurling having excellent ductility, suitable tensile strength and proof stress.

Another object of the present invention is to replace the paper tube with aluminum alloy tube for polypropylene multifilament yarn winding.

Yet another object of the present invention is to provide bobbin/tube made up of aluminum alloy with a capacity to withstand bobbin insertion impact without getting any damage at its ends.

Yet another object of the present invention is to provide aluminum tube/bobbin with inside knurled surface at two symmetrical places on the bobbin to perfectly position on circular springs on winding heads (spindle) of multifilament yarn manufacturing machine for slippage free rotation of aluminum alloy /bobbin/tube. Yet another object of the present invention is to provide a knurling assembly for knurling the inner peripheral surface of the bobbin or tube.

Yet another object of the present invention is to provide aluminum tube/ bobbin with outside longitudinal grooves or V- grooves along length to facilitate bottom layer yarn.

Yet another object of the present invention is to provide aluminum tube/ bobbin with outside rough surface to prevent slippage in initial winding.

Further object of the present invention is to provide a light weight aluminum bobbin/tube with high tensile strength so that it does not get deformed due to multifilament yarn pressure or the reason like monsoon.

Yet another object of present invention is to provide a method of manufacturing aluminum tube / bobbin made up of different aluminum alloy and variations thereof.

One more object is to provide tube/bobbin with inside/outside special round surface preparation on both ends for easy insertion and ejection of tubes before and after winding Polypropylene Multifilament yarn.

Summary of the Invention

The present invention relates to an aluminum alloy bobbin with internal knurling for improved gripping and manufacturing method thereof. The present invention provides an assembly for providing the knurling at the inner peripheral surface of the bobbin with the help of knurling tool at predetermined position. The present invention provides slippage free features made from different versions of aluminum alloy. The primary billets of aluminum alloys are subjected to a porthole extrusion process followed by cold drawing. Cold drawn tubes are further solution treated by special water quenching. After successive cold drawing, the tubes are straightened on the straightening machine and subsequently the age hardening is carried out to achieve desired tensile strength and ductility in the product. After cutting to required length product is cut to specified size followed by deburring of both ends outside and inside to ease of insertion and removal.

Brief description of drawing

Figure 1 depicts an isometric view of an aluminum alloy bobbin.

Figure 2 shows cross sectional view of aluminum alloy bobbin.

Figure 3 illustrates another view of aluminum alloy bobbin.

Figure 4 illustrates a cross sectional view of a knurling mechanism as the preferred embodiment.

Detailed Description of the Invention

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated. The invention is capable of other embodiments, as described above and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not to limitation. The invention may have various embodiments and they may be performed as described in the following pages of the complete specification.

Dimension and weight of the aluminum tube used conventionally varies as per the definitive application. Dimension of the Aluminum tube for Polypropylene Multifilament Yarn is 110 mm ID x 116 mm OD or 110 mm ID x 115 mm or 110 mm ID x 114 mm OD depending on the denier tenacity of yarn.

Present invention provides aluminum alloy bobbin with internal knurling for improved gripping. Now as shown in figure 1 and 2, an aluminum bobbin (1) where knurling (2) is provided in inner side at predetermined distance from both ends of the tube. Outside surface of the aluminum bobbin or tube is rough and also provided with External knurling (3) from starting to ending for better gripping of multifilament yarn. The centerless roughing machine is used to create outside rough surface. Further, on the outside surface of the tube longitudinal grooves or V- grooves (4) are provided in one or more nos. at specific location to facilitate bottom layer yarn removal without damaging the surface of tube. The yarn can be removed by any available methods such as through yarn stripping machine or manually (i.e. _z by knife).

Now as shown in fig. 2 total length of aluminum bobbin or tube is 280 mm (L). The tube has knurling portion at 25 mm (LI) from the edge of tube. The distance between two knurling portion is 180 mm (L0) on the tube. The selection of the depth and height of the knurling depends on the Spindle or spring that will hold the tube at the time of winding. Now as illustrated in figure 3, its shows another view of the aluminum alloy bobbin, where knurling have many number of groove. The pitch (P) of the groove is 0.4 mm and depth (W) is 0.2 mm. Horizontal longitudinal grooves or V groove (4) is provided to facilitate removal of last layer of yarn.

Figure 4 shows cross sectional view of knurling mechanism (11) to create inside knurling comprising a lathe chuck (6) with three jaws fitted on head stock (5) for clamping of the bobbin, the lathe chuck (6) rotates in clockwise direction along with a bobbin at specific speed, a rubber sheet (7) provided to avoid aluminum bobbin damage at the end of the lathe chuck (6) to hold the bobbin (1) firmly during rotation, and knurling tool (8) coupled with a tool holder (9) and the said tool holder provides movement to the knurling tool.

Continue to figure 4, the tool holder (9) is connected with a tool post (10) and the said tool post moves the tool holder (9) upward and downward direction or in vertical direction for knurling the bobbin (1) through knurling tool (8) on peripheral of inner surface of the bobbin (1). Tool post (10) also moves in horizontal direction along with tool holder (9) for providing the knurling depth (2) at predetermined position.

The aluminum tubes or bobbin of size 110mm ID(Inner Diameter) x 116mm OD (Outer diameter) or 110mm ID x 115mm OD or 110mm ID x 114mm OD are developed from alloy 6082/6061 and other different versions of both alloys. The composition of both the alloys is shown in below tables.

Table 1 Table 2

Table 3 Table 4

Alloys 6082/6061 have good mechanical property. To increase the strength of aluminum tube, process called cold drawing and hardening is done further while also providing precise thickness control, internal diameter and increases the strength of aluminum tube. The process will be explained below in detail.

Extruded porthole aluminum tubes (6082/6061) can be used as feed stock or mother tube in two different conditions i.e. T4 and M for both the alloys (6082 and 6061) and its different versions. Here T4 condition means solution treated porthole extruded tubes which does not require solution treatment in later stages. M condition means porthole extrusions of alloy as manufactured without solution treatment. This tube requires solution treatment at a later stage. The alloy is casted into shape suitable for extrusion by continuous or semi-continuous casting i.e. Round Billet. The Billet is used to extrude required size round tubes. As this is a hot extrusion, there is a variation in thickness and limitation of achieving lower thickness for required diameter which leads to uneven mass distribution.

T4 condition means solution treated porthole extruded tubes which does not require solution treatment in later stages. M condition means porthole extrusions of alloy without solution treatment. The alloy is casted into shape suitable for extrusion by continuous or semi-continuous casting i.e. Round Billet. The Billet is used to extrude required size round tubes. As this is a hot extrusion, there is a variation in thickness and limitation of achieving lower thickness for required diameter which leads to uneven mass distribution.

After the said extrusion, tensile strength of the aluminum tubes is achieved on particular level from 140 to 235 MPa and percentage elongation is achieved in range of 14% - 21%. However, these mechanical properties are not sufficient for making aluminum tubes suitable for the application. Further, during hot extrusion, the dimensional tolerances achieved are wider. Hence to counter these issues, the extruded aluminum tubes are subsequently cold drawn at room temperature. This cold drawing process serves to reduce cross section area of the aluminum tubes while improving the surface finish and also to achieve close dimensional tolerance on internal diameter and thickness. In the cold drawing process, due to work hardening, tensile strength of the aluminum tubes increase to about 185 to 290 MPa while percentage elongation is decreased to about 6 to 12% with reference to extruded aluminum tubes.

During the cold drawing process an undesirable stress is developed in the aluminum tubes. Hence, to relieve surface stress, the cold drawn aluminum tubes are then straightened on hyperbolic 6 rolls machine. This straightening process is carried out with tubes inputs from one direction and if required, the tube direction is reversed and is again passed through the straightening machine with a view to make sure that straightness achieved is exceptionally good to the level of about 1/1500.

Once the desired mechanical properties in the resultant aluminum tubes are achieved, the tubes with original starting of extruded tubes of M condition (as manufactured condition) are solution treated at this stage followed by Age Hardening. The tubes which were originally solution treated (T4 condition) during extrusion stage are directly Age Hardened.

In artificial age hardening process, the aluminum tubes are heated at about 160 to 200° C for soaking time of about 6 to 18 hours. The time generally depends upon the dimension and thickness of the tubes. The tensile strength shall go beyond 295 MPa and percentage elongation to a level of 10 to 16%. The resultant aluminum tubes obtained by the above method of the invention from the alloys 6061, 6082 and different versions of both alloys are suitable for PP multifilament yarn.

After the heat treatment the tubes cut to required length. They are subjected to special deburring operation at both ends of tube on inside and outside.

The tubes are then subjected to knurling operation at specific distance from the end; the operation is carry out on inside diameter of the tube through the knurling tool (8) to create anti-slip feature. It is carrying out at a distance where spring is fixed on spindle due to which proper grip on the spindle is achieved.

ADVANTAGES:

• Cold drawn aluminum alloy tube/bobbin with internal knurling provides close tolerance, good straightness, exceptional tensile strength, desired percentage elongation and required ductility. The deburring at both the ends of the tubes facilitate easy insertion and withdrawal. Providing thickness which is not available by any other process such as extrusion. The manufactured aluminum alloy tube/bobbin by method according to present invention have features such as inside two circular knurling areas, deburred ends outside and inside, good straightness, excellent thickness control for uniform mass distribution, high strength, required ductility which all have usefulness for Polypropylene multifilament yarn.

• Rough surface on the aluminum tube/bobbin prevent slippage of yarn and v- grooves facilitate for removal of bottom yarn layer.

• While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. It is expressly understood, however, that such modifications and adaptations are within the spirit and scope of the present invention as set forth in the following claims.

Reference Numerals:

1- Aluminum bobbin or tube

2- Internal or inside knurling

3- External or outside knurling

4- V - grooves

5- Head stock

6- Lathe chuck with Jaws

7- Rubber sheet

8- Knurling tool

9- Tool holder

10- Tool post

11- Knurling mechanism