TECHNICAU FIEUD

[0001] The present disclosure generally relates to the field of net making. In particular, the present disclosure relates to a method for making a rigid cage net structure with a stiff mesh.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Aquaculture is a fast-growing industry bom to cater to consumers of seafood where fish are grown from fingerlings to adulthood in grow out cages. An important function of the grow out cage is to prevent the fish, especially the adult fish, from escaping the cage, while still allowing sufficient flow of water through the cage for maintaining a healthy dissolved oxygen level for the growth of the fish.

[0004] Grow out cages are typically a synthetic net attached to a floating framework made of HDPE pipes or steel cages. The synthetic net is typically made of nylon, as nylon offers good strength and has a specific gravity of 1.14 gem , thus allowing the net to sink in water.

[0005] Nylon, however, suffers from being flexible, which means that, even though the nylon nets may be anchored to keep the cage taut, the net cage can deform during strong currents. Nylon is also susceptible to long term problems such as loss of strength and toughness due to absorption of water. There can be up to a 40-50% reduction in strength of nylon after 3 to 4 years of being submerged in water. Further, nylon nets shrink in water and thereby resulting in volume reduction and causing tension on the mooring system.

[0006] High density polyethylene (HDPE) has largely replaced Nylon as a material for making nets, in many parts of the aquaculture industry. Knotless and knotted HDPE nets are used with increase in life and ease of maintenance being major value additions. HDPE nets can form efficient grow out cages due to their dimensional stability (no shrinkage, maintaining cage dimension and volumcjthroughout the service life of the net. HDPE nets have demonstrated great improvements over the traditional nylon nets in terms of mesh stiffness, resistance to net washing and service life (in some cases, almost twice that of nylon nets).

[0007] However, both knotless and knotted HDPE nets are flexible, leading to issues of mesh occlusion during strong water currents. This compromises the ability of the net to retain the shape of the mesh.

[0008] There is, therefore, a requirement for a net structure in aquaculture that can offer therequired rigidity in the mesh and that can also exhibit required strength and longevity in water.

[0009] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0010] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term“about”. Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0011] As used in the description herein and throughout the claims that follow, the meaning of“a,”“an,” and“the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of“in” includes“in” and “on” unless the context clearly dictates otherwise.

[0012] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g.“such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0013] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

OBJECTS

[0014] A general object of the present disclosure is to provide a rigid cage structure for aquaculture.

[0015] Another object of the present invention is to provide a mesh that undergoes minimal deformation.

[0016] Another object of the present invention is to provide a composite twine for making a rigid cage structure.

SUMMARY

[0017] The present disclosure generally relates to the field of net making. In particular, the present disclosure relates to a method for making a rigid cage net structure with a stiff mesh.

[0018] In an aspect, the present disclosure provides a rigid cage structure for aquaculture, said rigid cage structure comprising a composite twine that comprises: an outer shell comprising one or more polymer yarns; andan inner core comprising a combination of: a low melting polymer multifilament; andany or a combination of a polymer monofilament and a polymer multifilament, wherein said polymer multifilament is different from said low melting polymer multifilament. [0019] In an aspect, the present disclosure provides a composite twine, said composite twine comprising: an outer shell comprising one or more polymer yams; andan inner core comprising a combination of: a low melting polymer multifilament; andany or a combination of a polymer monofilament and a polymer multifilament, wherein said polymer multifilament is different from said low melting polymer multifilament.

[0020] In an embodiment, the inner core further comprises at least one metal wire.

[0021] In another embodiment, the any or a combination the polymer monofilament and the polymer multifilament is selected, independently, from the group comprising polyester, polyolefin and polyamide.

[0022] In another embodiment, the inner core further comprises a hot melt resin.

[0023] In an aspect, the present disclosure provides a method for making the composite twine, said method comprising the steps of: stretching the composite twine at a pre-defined temperature to a desired length; andcooling the stretched composite twine, wherein, one or more iterations of heating and subsequent cooling of the stretched composite twine is performed to provide a rigid twine conforming to the stretched shape.

[0024] In an embodiment, the predefined temperature ranges from 85 °C to 115 °C.

[0025] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure, and wherein:

[0027] FIG. 1 illustrates an exemplary rigid net structure using a composite twine, for making a rigid cage, in accordance with embodiments of the present disclosure.

[0028] FIG. 2 illustrates an exemplary flow diagram for a method to make a rigid net composed of a composite twine, in accordance with embodiments of the present disclosure.

[0029] FIG. 3 illustrates a demonstration of rigidity of proposed mesh structure when compared to a typical mesh found in the art. DETAILED DESCRIPTION

[0030] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.

[0031] The present disclosure generally relates to the field of net making. In particular, the present disclosure relates to a method for making a rigid cage net structure with a stiff mesh.

[0032] FIG. 1 illustrates an exemplary net rigid structure 100 and rigid mesh using a composite twine, for making a rigid cage, in accordance with embodiments of the present disclosure. In an embodiment, the net made from the composite twine can be stretched to a desired shape and upon a heating-cooling cycle, can form a rigid net structure 100 conforming to the stretched shape.

[0033] In another embodiment, the composite twine has an inner core and an outer shell, running parallel to one another along the length of the composite twine. In another embodiment, the outer shell is comprised of high melting polymer yams that provide the composite twine toughness against wear and abrasion. In an exemplary embodiment, the high melting polymer can be any or a combination of polyolefin homopolymer yam, other polyolefin yams, mix of polyolefin and polyamide yams and a mix of polyolefin and polyester yarns.

[0034] In another embodiment, the inner core comprises a mix of high melting polymers and low melting polymers. When heated to the softening point of the polymer, the low melting polymers soften and bind with the high melting polymers. During the lengthway, stretching the net is heated up to the melting point of the low melting polymer and then cooled. Upon cooling, the low melting polymers bind to the high melting polymer yams, thus making the mesh rigid. The composite twine, after a heating-cooling cycle, thus, is a matrix of“solidified”polymer yarns to offer rigidity and high melting polymer to offer resistance to wear and abrasion. In another embodiment, a metal wire is also part of the inner core, offering additional strength to said inner core.

[0035] In an aspect, typically, polyester yarns are coated in wax to improve the rigidity of the twine. However, this process is both dangerous and expensive to follow during manufacture, and further, it does not add much in terms of rigidity to polyester yarns. [0036] In an embodiment, the proposed composite twine does not have any wax coating or any wax in its core, and still, it assumes a higher rigidity and stiffness than the typical wax coated polyester yarns.

[0037] In an exemplary embodiment, the inner core of the composite twine is made of any or a combination of a mix of polyolefin yarns, a polyester monofilament, a polyester multifilament, a low melting polyester multifilament. A hot melt resin can also be a part of the inner core. In another exemplary embodiment, the metal wire is a stainless-steel wire.

[0038] In another embodiment, the net made from the composite twine, upon heating to a specific temperature, the low melting polyester multifilament yam in the core melts and, upon cooling, binds with the polyester monofilament and polyester multifilament. The mesh and net turn rigid due to“solidification” of the molten yarn upon cooling. Additionally, the stainless-steel wire adds strength and rigidity to the composite twine.

[0039] FIG. 2 illustrates an exemplary flow diagram for a method to make a rigid net composed of a composite twine, in accordance with embodiments of the present disclosure. In an embodiment, said method 200 comprises the steps of: barring a raw net; stretching the net depthway with at temperatures around the softening point of the low melting yam; and stretching the net lengthway at a temperature around the melting point of the low melting yarn.

[0040] In an embodiment, a raw net is composed of the composite twine which has not yet been subjected to a heat treatment. In another embodiment, at step 202, the raw net is barred on at least two sides using bars, in order that the net does not get entangled. In an exemplary instance, the bars have rings which can be used to hook the net.

[0041] In another embodiment, at step 204, the raw net is stretched along the width of the net in a depthway stretch machine. The depthway stretch module is set based on desired net parameters such as hanging ratio, mesh size, depth mesh and netting weight.

[0042] In another embodiment, the raw net is stretched in the depthway stretch machine for a specified period of time at a specified temperature. The heat initiates melting of the low melting polyester multifilament in the core leading to desired knot tightness.

[0043] In an exemplary embodiment, the time period of stretching is about two minutes at a temperature of about 85 °C. After two minutes, the raw net is allowed to cool.

[0044] In another embodiment, at step 206, the raw net is stretched along the length of the net in a lengthway stretch machine. The lengthway stretch module is set based on desired net parameters such as hanging ratio, mesh size, depth mesh and netting weight. [0045] In another embodiment, the raw net is stretched for a specified period of time at a specified temperature, the raw net being at a temperature around the melting point of the low melting polyester multifilament.

[0046] In an exemplary embodiment, the temperature for lengthway stretching is about 115 °C. the stretch ratio for the lengthway stretch is about 1: 1.8.

[0047] In another exemplary embodiment, the meshes of the net are further joined to one another using a suitable twine such as braided nylon twine with a mean diameter of 5 mm or more.

[0048] In another embodiment, upon cooling, the mesh and net turn rigid due tothe “solidification” of the molten yam. In an exemplary embodiment, one or more of such net structures can be used to make a rigid cage.

[0049] In another exemplary embodiment, table 1 below provides a process for the making of rigid net using a composite twine, in accordance with embodiments of the present invention.

Table 1: Exemplary process for making rigid net structure

[0050] In an exemplary embodiment, the mesh size of the formed cage can be varied based on the size of fish that is being held. The size of the mesh must be such that it allows free flow of water through the cage but prevents escape of fish. Table 2 below provides an exemplary range of mesh sizes based on size of fish.

Table 2: Exemplary mesh sizes for grow-out cages for different size offish

[0051] In an aspect, the stiffness of a body (k) is a measure of the resistance offered by the body to deformation. In another aspect, for an elastic body with a single degree of freedom (DOF), the stiffness is defined as,

F - force on the body.

b - displacement produces by the force (F) along the same degree of freedom.

[0052] In another aspect, the stiffness (k) of nets can be measured using the California Bearing Ratio (CBR) puncture Resistance test. The test asses the strength of a twine by forcing a plunger through a twine suspended unsupported in a test jig. In actuality, the CBR test is an axisymmetric strength test. The unsupported twine is under tension and the stress conditions are known, allowing an accurate calculation of stress and strain of the twine.

[0053] In another aspect, the fishing net of the present disclosure comprising the composite twine is subjected to the CBR test and calculations are performed to determine the stress and strain on the net. The value of stiffness (k) obtained can be compared to that of other nets to tabulate a comparative study of the net of the present disclosure with other nets available in the art. Further, the net was subjected to the CBR test before and after subjecting the net to different materials of chemical and biological incubation in order to assess changes in stiffness of the net.

[0054] In an embodiment, table 3below provides the machine parameters considered during the testing of the proposed net.

Table 3: Machine parameters for CBR test of the proposed net

[0055] In an embodiment, the stiffness (k) of the proposed net structure can be such that the mesh of the rigid net structure formed retains its structure even when the cage itself is distorted due to currents. In an exemplary embodiment, the proposed net structure has a stiffness (k) value between 4 and 7.

[0056] FIG. 3 illustrates a demonstration of the rigidity and stiffness of the proposed mesh when compared to a typical mesh found in the art. In a typical mesh, as the water current becomes faster to attain a speed of about 1 knot, it can be seen that the mesh undergoes deformation, which can result in less than optimal exchange of water and maintenance of dissolved oxygen, endangering the health of the fish.

[0057] In an embodiment, the proposed mesh, due to the“solidification” of the molten yarn achieves higher stiffness and rigidity than the typical mesh. It can be seen that at a water current speed of 1 knot, the mesh retains its shape, thereby ensuring optimal dissolved oxygen.

[0058] Thus, the present disclosure provides a rigid net structure composed of a composite twine that can prevent escape of the fish contained within. Further, the rigid cage has a higher durability and is simpler and safer to manufacture. For the rigid cage structure, an exemplary advantage is the“mesh stiffness” such that when the mesh is flexible, during strong water currents, the mesh shape is distorted, resulting in reduction of size of the mesh. The rigid mesh allows the mesh shape retention, and therefore during strong currents, the mesh will not distort as much, resulting in better water exchange and hence better dissolved oxygen.

[0059] Without departing from the spirit and concept of the present invention, any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art, and therefore fall in the scope of the present invention which is defined by the accompanied claims. Though the present invention has been described on the basis of some preferred embodiments, those skilled in the art should appreciate that those embodiments should by no means limit the scope of the present invention. Without departing from the spirit and concept of the present invention, any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art, and therefore fall in the scope of the present invention which is defined by the accompanied claims. [0060] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES

[0061] The present disclosure provides a rigid cage structure for aquaculture.

[0062] The present disclosure provides a mesh that undergoes minimal deformation.

[0063] The present disclosure provides a composite twine for making a rigid cage structure.