Field of invention:
The present invention is related to shuttles utilized in circular weaving looms; in particular it relates to a weft unwinding and tensioning system and a circular loom shuttle that incorporates the shuttle pad assembly and a circular loom that deploys the shuttle carrying the shuttle pad assembly.
Background:
The circular loom has been recognized as one of the most practical weaving machines for producing tubular fabric, which is preferably used as a base material-fabric for making a transportation container or a storage container of granules, such as grains, sugar, fertilizers, polymer granules and chemicals.
In the known circular looms, an even number of shuttles is mounted on an annular shuttle guide member so that they can travel along this guide member. Engaging means to be engaged with corresponding shuttles, respectively, such as press rollers, are moved along the shuttle guide member. Each shuttle is pressed by the corresponding engaging means and propelled along the shuttle guide member. Wefts taken out from the respective shuttles are fabricated with warps sequentially opened on both the upper and lower sides of the respective shuttles by healds, and a tubular fabric is thus formed.
In the circular loom, for an increase in the production-efficiency, it is required to use so-called large-package-bobbins. However, since it is obvious that, if the size of the yarn package becomes larger, there will be difference in unwinding characteristic of full bobbin diameter, especially when the bobbin diameter reduces to below a certain size.
In the case of the shuttles for circular looms which are used, for example, for the tubular bag manufacture, it has been customary to attach a flap on the weft bobbin body, which is held down by a spring against on the bobbin thread winding. The flap, which moves about a fulcrum point, has a covering of leather or felt and

pivots with decreasing bobbin winding always to the coil axis. This consequently results in decreased braking force or the applied pressure towards the end of the winding. However, different thread or strip materials that have been processed in the circular loom require different braking force. For example, slit film strip material made of polypropylene are slightly stiffer and rougher than the softer and smoother tapes made from polyethylene material. The braking force generated by a pressure pad (or a brake pad) being acted directly on the thread or strip material, continuous abrasion could lead to damage to the brake material. This may further lead to uneven tension control, if pressure pads are not regularly replaced. Also, it may damage the weft tape material. The replacement of pressure pads lead to decrease in productivity of loom and expense on consumable items.
WIPO publication WO2010084074A1 discloses a device for controlling the weft band tension on a shuttle, shuttle and a circular loom equipped therewith. The publication makes a reference to the brake liners used in the shuttles deployed in the circular looms and how the pressure applied by the brake liners is instrumental in generating tension in the weft yarn.
Another document, US patent 4365651, also discloses a shuttle utilized in a circular loom. In particular, this document discloses a shuttle that is provided with an improved structure for easily mounting on or dismounting from said circular loom while providing a stable structure that is able to support large size bobbins. It makes a passing reference to an element 51 (see figures 6 and 8 A of the document) which is capable of always keeping a braking action against a bobbin for providing an adequate yarn tension to the weft yarn.
However, neither of the documents, WO2010084074A1 orUS4365651, makes any reference to the wear and tear of the brake liners themselves or the need for replacing them frequently, and the adverse impact of it on the fabric production. Nor does it provide a solution to obviate the problems that are widely faced in the industry.

Thus, there is need for alternative shuttle pad assembly system deploying a pressure pad assembly which has enhanced wear resistance and which is gentle on the weft material. Further, there is also a need for a cost-effective system having long service life.
Objects of Invention:
One object of the present invention to provide a shuttle pad assembly system deploying a pressure pad assembly which has enhanced wear resistance and at the same time is gentle on the weft material.
Another object of the present invention is to provide a shuttle pad assembly system deploying a pressure pad assembly which is cost-effective and having long service life.
A further object of the invention is to provide a shuttle that employs a shuttle pad assembly which has a pressure pad assembly with enhanced wear resitance.
A still further object of the invention is to provide a circular loom that employs a shuttle having a shuttle pad with a pressure liner that has enhanced wear resistance.
Brief Description Of Figures:
Figure 1 shows a schematic of the working of the braking system used in a
circular loom
Figure 2 shows the pressure pad assembly arrangement of the invention.
Figure 3 shows a number of alternatives of the cross-sectional curvature of the
pressure pad liner
Figure 4 shows a perspective view of the pressure pad liner
List Of Parts:

SA - Shuttle pad assembly 10 B - Bobbin or bobbin package
SB - Shuttle body Do - Bobbin diameter at end
1 - Connecting arm or tension arm Di - Bobbin diameter at start (full)
2 - Pressure pad assembly 6 - Outer surface of pressure pad 5 2A - Pressure pad liner liner
2B - Pressure pad receiver 15 6A - Hump in the pressure pad liner
3 - Pivot mechanism cross-section
4 - Tension spring 7 - Outside surface of bobbin
5 - Fixed support for tension spring package
Summary of invention:
The invention discloses a shuttle pad assembly (SA) that incorporates a pressure pad assembly (2) that is harmless to the yarn as well as to itself. The pressure pad assembly (2) is provided at one end of the tension arm (1). The pressure pad assembly (2) has a pressure pad liner (2A) that is mounted on a pressure pad receiver (2B) which is connected to the tension arm (1). Figure 2 shows the pressure pad assembly (2) of the invention. The tension arm (1) connects the pressure pad assembly (2) to a pivot mechanism (3) which is affixed to the shuttle body. The pivot mechanism (3), in turn, is connected to a fixed support (5) through a tension spring (4). The pressure pad liner (2A) of the invention is made of hard wearing such as metals such as stainless steel or alloy steel. They may be made from sheet metal or shaped by machining solid metal block. The invention also discloses a shuttle that incorporates the shuttle pad assembly as disclosed here and a circular loom that deploys the shuttle carrying the shuttle pad assembly disclosed here.
Description:
The unwinding tension of yarn from wound bobbins (B) is a very important criterion determining the quality of the product. It has been observed that the nature and magnitude of variation in yarn tension depend on the size of the bobbin (B) at the start and end of the unwinding process. The tension increases both with

the depletion of bobbin (B) and with the increase in unwinding speed of the bobbin (B). In a circular loom weaving, during the production process, the weft yarn unwinding tension is controlled by a shuttle pad assembly (SA). The shuttle pad assembly (SA) rotates around a pivot point with the help of a tension spring mounted on the shuttle body. The shuttle pad assembly (SA) also has a mechanism to control the speed of the rotating bobbin, typically a pressure pad assembly (2) that presses on the weft bobbin surface (refer to Figure 1).
The surface of the pressure pad assembly (2) that comes in contact with the wound bobbin (B) experiences friction from the yarn that is getting unwound. The material of this contact surface should be such that it does not cause damage to the yarn. At the same time the material should be such that it does not get worn out itself from the friction. Generally, the pressure pad assembly (2) provided in the shuttle pad assembly (SA) has a pressure pad liner (2A) that is made of leather or felt, which pressed against the weft bobbin. This material is found to be generally harmless to the yarn, however, it has been found that as the weft yarn runs through the pressure pads made of felt or leather, the contact surface of the pressure pad liner (2A) wears out due to constant abrasion with the yarn. This leads to frequent change/replacement of the pressure pad liner (2A) depending on the type of yarn material of weft bobbin (B).
The general working of a shuttle pad assembly (SA) of the invention is now
explained. Figure 1 shows a bobbin (B) that is being unwound and the shuttle pad
assembly (SA). It shows a pressure pad assembly (2), which is a part of the shuttle
pad assembly (SA), that exerts pressure on the outside face (7) of the wound
bobbin (B). The pressure pad assembly (2) comprises a pressure pad receiver (2B)
on which a pressure pad liner (2A) is mounted. A connecting arm or the tension
arm (1) connects the pressure pad assembly (2) to a pivot mechanism (3) that is in
turn affixed to the body of the shuttle that carries the bobbin. The pivot
mechanism (3), in turn, is connected to a fixed support (5) that is also affixed to
the shuttle body through a tension spring (4). As shown in Figure 1, deformation
6

of the tension spring (4) develops tension in the tension arm (1). As a consequence, the pressure pad assembly (2) presses onto the weft bobbin (B), thereby hampering the uncontrolled free rotation of the weft bobbin (B), which in turn leads to developing a pre-determined amount of tension in the weft yarns.
As weaving production process progresses, the diameter of weft bobbin (B) gradually decreases. At the start, the outer diameter of the wound package for full package size of the weft yarn bobbin is about 110 to 90 mm (represented by Di in Figure 1), whereas towards the end, the outer diameter of the empty bobbin is around 35 to 40mm (represented by Do in Figure 1). On a newly installed weft bobbin (B) with full volume, the shuttle pad assembly is designed to exert pressure through its pressure pad liner (2A) on the outer surface (7) of the full bobbin (B). At this stage the deformation of the tension spring (4) is Li. With time, as the weft bobbin diameter decreases, the brake pad now acts on the outside surface (7) of the bobbin (B), which has a reduced diameter D0, and the spring deformation reduces to L0. At this point, the traction force to overcome the frictional and the tension force generated by the pressure pad assembly (2) also reduces.
The invention discloses a shuttle pad assembly (SA) that incorporates a pressure pad assembly (2) that is harmless to the yarn as well as to itself. The pressure pad assembly (2) is provided at one end of the tension arm (1). The pressure pad assembly (2) has a pressure pad liner (2A) that is mounted on a pressure pad receiver (2B) which is connected to the tension arm (1). Figure 2 shows the pressure pad assembly (2) of the invention. The tension arm (1) connects the pressure pad assembly (2) to a pivot mechanism (3) which is affixed to the shuttle body (shown indicatively as SB). The pivot mechanism (3), in turn, is corrected to a fixed support (5) through a tension spring (4). The pressure pad liner (2A) is mounted on the pressure pad receiver (2B) by any one of the number of arrangements selected from screw-on type, or glue-on type, or press-fit clip-on type, or a combination thereof.

The pressure pad liner (2A) of the invention is made of hard wearing material such as metals, for instance stainless steel or alloy steel. They may be made from sheet metal or shaped by machining solid metal block. The texture of the outer surface (6) of the pressure pad liner (2A) that comes in contact with the bobbin (B) is of importance. The outer surface (6) is polished to reduce its friction coefficient as much as possible, preferably to between 0.1 and 0.25. Alternatively, the pressure pad liner (2 A) may be made of any material as a base material and on which a hard-wearing coating/abrasion resistance coating using a number of technologies such as like nitriding or hard anodizing or chrome plating or plasma electrolytic oxidation, or chrome carbide, or chrome oxide, or tungsten carbide or ceramic coating may be provided. The coating surface has roughness preferably in the range between 0.1 and 2.3 micron Ra.
Also is of importance is the shape or the curvature of the outer surface (6) of the pressure pad liner (2A) - it should be such that the contact area between the outer surface (6) and outside surface (7) of the bobbin (B) being unwound is minimised. For this purpose, the outer surface (6) has a preferably curved cross-sectional geometry as shown in Figure 3. As shown in part (a) of Figure 3 and 4, a single hump is provided in the pressure pad liner (2A), and which runs over the entire length of the pressure pad liner (2A). In one aspect of the invention, the pressure pad liner (2A) may have a multiple-hump contact surface (6). As shown in part
(b) of Figure 3, the outer surface (6) may have a double hump, or as shown in part
(c) of Figure 3, it may have a linear shape. The curved shape is preferably convex.
The pressure pad liner (2A) is mounted on the pressure pad receiver (2B) by any one of the number of arrangements or their combination. The mounting arrangement may be of a screw-on type or the pressure pad liner (2A) may be glued on to the pressure pad receiver (2B) using suitable type of glue. The shape of the pressure pad liner (2A) may be such that it may be in the form of a clip that may be press fitted onto the receiver (2B).

In another aspect of the invention, the pressure pad liner (2A) of the shuttle pad assembly (SA) disclosed in the invention has been provided with wear resistant treatment like plasma electrolytic oxidation coating or carbide coating, leading to very long service life. In the some case the base material of the shuttle pad liner may be hard wearing plastic like PEEK, acetal, or UHMW.
Example: A pressure pad made of stainless steel was used in shuttle in a circular loom. Bobbins carrying slit film tape yarn were used to make circular tubular fabric, of 500mm width. Fabrics were made using shuttle pad assembly deploying conventional brake liners made of leather/felt and also separately pressure pad liners of the invention. It was observed that the conventional brake liners needed replacing after 15 to 22 hours whereas at the end of 300 hours, the pressure pad liners of the invention were still operational.
Further experimental data suggested that service life of the shuttle pad assembly deploying felt type brake liner is around 10 to 24 hours, while that of the shuttle pad assembly (SA) of deploying hard wearing pressure pad liner (2A) of the invention is more than 30 days. This leads to increase productivity of loom and better quality of woven circular fabric with lesser width variation.
The invention also discloses a shuttle assembly incorporating the shuttle pad assembly. The shuttle pad assembly of the invention requires less frequent replacements of the pressure pad liner (2A) as compared with the existing shuttles that deploy brake pads.
The invention also discloses a circular loom that deploys shuttles using the shuttle pad assembly disclosed here. The loom of the invention requires fewer shutdowns to replace the brake pad liners (2A).

While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

We claim:
1. A shuttle pad assembly (SA) used in a circular weaving loom, said shuttle pad assembly (SA) comprising a tension arm (1), a tension spring (4), a pivot mechanism (3) around which said tension arm (1) is rotatable at one end of said tension arm (1), a fixed support (5) to which said tension spring (4) is attached, a brake pad assembly (2) mounted at the other end of said tension arm (1), said shuttle pad assembly (SA) is provided in a shuttle that carries a bobbin (B) on which yarn is wound, characterised in that said brake pad assembly (2) comprises a pressure pad receiver (2B) on which a pressure pad liner (2A) is mounted, wherein said pressure pad liner (2 A) applies pressure on outer surface of the wound bobbin (B).
2. The shuttle pad assembly (SA) as claimed in claim 1, wherein said pressure pad liner is made of hard wearing materials.
3. The shuttle pad assembly (SA) as claimed in claim 2, wherein said hard wearing material is either metals, or metals coated with wear resistance coating.
4. The shuttle pad assembly (SA) as claimed in claims 1 to 3, wherein said pressure pad liner (2A) has a single hump (6A) type outer surface (6) that presses against the outside surface (7) of the wound bobbin (B), said hump (6A) being convex in shape.
5. The shuttle pad assembly (SA) as claimed in claims 1 to 3, wherein said outer surface (6) has multiple humps (6A).
6. The shuttle pad assembly (SA) as claimed in claims 1 to 5, wherein said pressure pad liner (2A) is mounted on the pressure pad receiver (2B) by any one of the number of arrangements selected from screw-on type, or glue-on type, or press-fit clip-on type, or a combination thereof.
7. The shuttle pad assembly (SA) as claimed in claims 1 to 6, wherein said wear resistant coating may be provided using any one of nitriding or hard anodizing or plasma electrolytic oxidation or chrome carbide, or chrome oxide, or tungsten carbide, or chrome plating or ceramic coating process and has a roughness between 0.6 and 2.3 micron Ra.

8. The shuttle pad assembly (SA) as claimed in claims 1 to 7, wherein in the case said outer surface (6) of said pressure pad liner (2A) is made of metal, it is polished to provide a friction coefficient between 0.1 and 0.25.
9. The shuttle pad assembly (SA) as claimed in claims 1 to 8, wherein in the case said outer surface (6) of said pressure pad liner is that of a wear resistant coating provided on any material base.
10. The shuttle pad assembly (SA) as claimed in claims 3 to 9, wherein said metal pressure pad liner (2A) is made from sheet metal or by machining solid block of metal.
11. A shuttle (S) for use in a circular loom, wherein said shuttle comprises a shuttle pad assembly as claimed in claims 4 to 10, wherein said contact surface has multiple humps.
12. A circular loom for weaving woven tubular fabric, wherein said circular loom employs a shuttle as claimed in claim 10, said shuttle in turn comprises a shuttle pad assembly as claimed in claims 1 to 10.