US3322021A - Process for producing a net - Google Patents

Description

May 30, 1967 v. s. VAN SCOY PROCESS FOR PRODUCING A NET Filed Feb. 4, 1964 INVENTOR VICTOR SAMUEL VAN SCOY ATTORNEY United States Patent 3,322,021 PROCESS FOR PRODUCING A NET Victor Samuel Van Scoy, Newark, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Feb. 4, 1964, Ser. No. 342,377 1 Claim. (Cl. 871) This invention relates to improvements in nets and, more particularly, to fish nets or safety nets. The invention specifically relates to the encapsulating of knots used in such nets and a method of manufacturing such encapsulated knots.

The problem of knot slippage is one that has been recognized by manufacturers of netting for many years and as a result various methods have been suggested for overcoming this problem. Such methods include the modification of the elastic memory of the twine material by wet heat-setting and drying of the knot while under tension as described in US. Patent 2,653,372. While this method has improved the knot retention, it does not permanently secure the knot or provide protection from internal abrasion during use.

Several processes have also been suggested for applying heavy coatings of resinous materials to an entire net to fix the knots and protect the filamentous twines from the deg'radative action of sun, water, sand, or other elements of exposure. Such coatings have not been fully successful because of the increase in weight, change in hand, or still other adverse elfects. Another approach at overcoming the problem has involved impregnation of the cord or twine of the netting with a solution of a resin in order to stiffen the yarn within the knot. This method also, however, results in an undesirable stiffening of the twine segments between knots. Accordingly a compromise must be sought between using suflicient stiffening agent to hold the knots but not so much that the stiffness of the net is unduly increased. Such procedures and products are described in US. Patent 2,823,576 and in U.S. Patent 2,823,575. Impregnation of the twine or cord prior to fabrication of the net has also been described in US. Patent 2,590,586.

As a further problem in the fabrication of fish nets, it has also been recognized that knot strength is normally less than the strength of the straight seine twine. Means heretofore suggested for improving knot slippage have not generally been satisfactory for also avoiding the knot strength problem.

This invention has as an object an encapsulated knot structure which eliminates knot slippage, increases knot strength, and provides protection against the degradative action of sand, water, and other elements of exposure.

A further object is to increase knot strength and, consequently, over-all net strength or, conversely, to permit a decrease in net weight for a given net strength requirement by the use of finer twines.

A still further object is to provide a method of manufacturing nets of increased strength.

Other objects will be apparent from the remainder of the specification and claims.

In accordance with the invention a method is provided for producing a fish net of improved resistance to knot slippage. The method comprises forming a fish net of filamentous twine, applying solely to the knot and immediately adjacent twine portions of the net a waterproof adhesive resin to encapsulate each of the knots, and solidifying the adhesive resin. It is important that the segments of twine between knots be uncoated and essentially free of said adhesive resin. It will be understood that in encapsulating a knot, the adhesive resin should penetrate and at least partially fill the void between the twines form- 3,322,021 Patented May 30, 1967 ing the knot. Although the knot may have first been pulled tight to a set condition, it is highly preferred to apply the encapsulating adhesive material after the knot has been formed but not tightened. The encapsulating material may be a solution of a resin in a solvent, such as a 15% solution of a polyamide resin in alcohol and water, or polyvinyl acetate in water, or a hot-melt adhesive having good adhesive characteristics for the fiber used in manufacturing the net.

The knot encapsulating process can be conveniently carried out on a conventional netting machine which has been modified to include a container for an adhesive resin solution or melt and means for intermittently immersing or coating a row of knots with the adhesive resin.

This invention will be further described with reference to the accompanying drawings wherein:

FIGURE 1 is a diagrammatic representation of a portion of a fish net prepared according to the invention.

FIGURE 2 is a diagrammatic illustration on an enlarged scale of an encapsulated knot of the net of FIG- URE 1.

FIGURE 3 is a diagrammatic side view of a netting machine equipped with means for applying adhesive to the knots of the net.

FIGURE 4 is also a side view of a netting machine equipped with alternate means for applying adhesive to the knots of the net.

Referring more particularly to the drawings, FIGURE 1 iilustrates a section of atypical net treated in accordance with the invention showing the knots 11 produced at the cross-over point of the twines -10 of the net, each knot being encapsulated by a globule of adhesive resin 12. FIGURE 2 shows the adhesive 12 as completely surrounding the loops of the knot 11 and extending a short portion along the twines 10. It will be seen that the adhesive has been confined almost exclusively to the knot portions of the net.

The operation of applying the adhesive to the knot can best be understood by referring to FIGURE 3, in which 13 represents generally a conventional netting machine which forms the knots 11 in a customary manner. .Feed rolls 14 transmit the loosely knotted net structure through the machine and into close proximity with a tank or trough 15 filled with a solution, melt or dispersion of adhesive 16. If the adhesive is of the melt-type, the molten condition is maintained by suitable heating devices, not shown. The netting advances and first passes about a nose bar 17 which extends across the width of the net and which is mounted in a stationary position to the frame of machine 13. The net then discharges from the machine through take-up rolls 18, these being adequately spaced from trough 15 to allow the adhesive applied at nose bar 17 to solidify, e.g. by cooling or by loss of solvent. The adhesive 16 is applied to the row of knots aligned on the rounded point of the nose bar 17 while the net is stationary during the formation of a new row of knots on the netting machine. While a row of knots is in position on the blunt edge of the nose bar, the adhesive trough 15 is raised by a suitable mechanical connection activated by an indexing device attached to the feed roll 14.

A preferred apparatus for use with lighter-Weight netting is illustrated by FIGURE 4 In this embodiment the netting machine 13 is adjusted to manufacture a loosely knotted net which is forwarded from the machine in close proximity to a rotating roll 40 which dips in a trough of adhesive 41. As the knotted net structure pauses in its advance past the rotating roll 40, a movable bar 42 presses against the net to move a row of knots 43 into contact with the adhesive coating on rotating roll 40. The amount of adhesive applied to the individual knots in this way may be varied by suitable adjustment of the timing of the movement of bar 42 through use of an indexing mechanism connected to the feed roll 14. The speed of rotation of the roll 40 and other factors such as the depth of penetration of the roll into the adhesive trough 41, the viscosity of the adhesive in the trough, or the use of grooves n the face of the roll, are also effective in controlling the amount of adhesive applied to the individual knots.

It is to be understood that the present invention is not limited to the particular type of twineemployed. Also the adhesive may be any film-forming resin, either thermoplastic or thermosetting, which is water-insoluble and forms a good bond on the twine. Thus, the adhesive may be a polyester resin, a polyvinyl resin, a polyamide resin, a polystyrene resin, a polyacrylic resin, or copolymers of any of the above resins of the same type, or different types. 7

By applying the adhesive to a loosely tied knot, complete penetration of the adhesive around the twine inside the knot permits the adhesive, when it has been dried or otherwise solidified or hardened, to form a saddle or cushion which reduces the fiber-to-fiber cutting and thereby increases knot strength over and above the increase obtained in coating tightened knots. The hardened adhesive material also serves to transmit some of the tensile load applied to the twine around the knot rather than through the knot. In actual use, the hardened adhesive also prevents sand or grit from entering the knot so that the abrasive action of these materials upon the twine within the knot is diminished.

It is a significant feature of the invention that nets so produced have suffered no losses in flexibility. Also the increase in weight of the knot due to the addition of the encapsulating adhesive is generally about 5 to of the weight of the knot, analrnost insignificant portion of the total weight of the net. 7

The following examples will further illustrate the practice of the invention. Unless otherwise indicated, parts and percentages are by weight.

EXAMPLE I V p A test net was prepared on a conventional netting machine using twines of 840 denier nylon 66 seine twine; The adhesive employed was a 15% solution in an 80%" ethanol/ 20% water mixture of a polyamide formed by the copolymerization of hexamethylene diammonium adipate, hexamethylene diammonium sebacate, and caprolactam. One section of netting was treated while the knots were loose 'and another section was treated while the minute in order to measure the breaking strength. The following data show the surprising advantage of encapsulating knots by the technique of the invention. a

Mesh breaking Nylon net: strength, in pounds Untreated 33.70 Knots tight when encapsulated 44.50 Knots loose when encapsulated 47.00,

These results show that the tight encapsulated knot has an increase of 32% of the strength of the untreated knot and the loose encapsulated knot has a 38% increase in breaking strength over the untreated knot.

EXAMPLE 11 Samples of gill nets made from 210 denier, nylon 66 seine twine were prepared and encapsulated using the encapsulating process and adhesive resin of Example 1.,

Immersion tests were performed upon these and control samples to determine the rate at which a loss in strength occurs under conditions of continuous exposure while submerged in a fresh water lake. After one year exposure,

the untreated control net had lost over 10% of its original Method for producing a net of improved resistance to knot slippage and breakage comprising forming a fish net of filamentous twine in which knots are formed but not tightened, applying solely to the untightened knot, the

twinerwhich forms the knot and immediately adjacent twine portions of the net a waterproof adhesive'resin to encapsulate each of the knots and the twine which forms the knot, thereafter tightening the knots before the resin solidifies and finally solidifying the adhesive resin.

References Cited UNITED STATES PATENTS 2,590,586 3/1952 Thompson et a1 8712 X 2,653,372 9/1953 Johnson et al 8712 X 2,823,575 2/1958 Needham et al. .'87'--12 X 2,823,576 2/1958 Needham et al. 8712 X 2,868,676 1/ 1959 Ljungbo 87-1 X 2,870,669 1/1959 Kopacki 8712 X 2,945,412 7/1960 Johnson 8712 X FOREIGN PATENTS '7 685,623 1/ 1953 Great Britain.

FRANK I. COHEN, Primary Examiner. I. PETRAKES, Assistant Examiner.

Images