US2792617A

US2792617A - Process of heat setting thermoplastic net in rope form and product produced thereby

Info

Publication number: US2792617A
Application number: US334479A
Authority: US
Inventors: Haller John Walter Ecroyd
Original assignee: Linen Thread Co Ltd
Current assignee: Linen Thread Co Ltd
Priority date: 1953-02-02
Filing date: 1953-02-02
Publication date: 1957-05-21
Anticipated expiration: 1974-05-21

Description

ay 7 J. w. E. HALLER 2,792,617

PROCESS OF HEAT SETTING THERMOPLASTIC NET IN ROPE FORM AND PRODUCT PRODUCED THEREBY Filed Feb. 2, 1953 3 Sheets-Sheet l INVENTOR.

JOHN WALTER ECROYD HALLER ATTORNEY May 21, 1957 J. w. E. HALL-ER 2,792,617

PROCESS OF HEAT SETTING THERMOPLASTIC NET IN ROPE FORM AND PRODUCT PRODUCED THEREBY 3 Sheets-Sheet 2 Filed Feb. 2, 1955 INVENTOR. JOHN WALTER ECROYD HALLER AT'IY'ORNEY May 21, 1957 J w E. HALLER 2,792,617

PROCESS OF HEAT S ETTiNG THERMOPLASTIC NET IN ROPE FORM AND PRODUCT PRODUCED THEREBY Filed Feb. 2, 1953 '3 Sheets-Sheet 3 FIG] INVENTOR. JOHN WALTER ECROYD HALLER ATTORNEY United States Patent PROCESS OF HEAT SETTING THERMOPLASTIC NET 1N ROPE FORM AND PRODUCT PRODUCED THEREBY John Walter Ecroyd Haller, Belfast, Northern Ireland,

assignor to The Linen Thread Company Limited, fliesgcw, Scotland, a British company Application February 2, 1953, Serial No. 334,479

9 Claims. (Cl. 28-78) The present application is a continuation-in-part of my copending application, Serial Number 282,970, filed April 18, 1952, now U. S. Patent 2,744,306.

The present invention relates to an improved netting, particularly an improved fishnetting, and to methods and apparatus for producing the same.

Until very recent years, it has been the practice to manufacture fishnetting from strands or twines of vegetable fibers, such as cotton and linen. These nettings were relatively shortlived under micro-biological attack from bacteria or fungi, usual wear and strain, and the alternate wetting and drying to which netting is subjected.

With the advent of twines and filaments of the thermosensitive synthetic resins, such as nylon, it became possible to make fishnettings which overcame many of the deficiencies of the fishnettings woven from strands of vegetable fibers. The new nettings of thermo-sensitive synthetic resins, while having great tensile strength and being resistant to weathering, micro-biological attack, etc., suffer from a very serious defect; the knots have a tendency to open up and slip or tip over during usage. This results in a variation in the size of the meshes of the netting making the netting substantially useless; particularly where used for gilling fish. Government agencies require stringent adherence to their regulations defining the minimum mesh size of netting to be used for particular purposes. Fishermen want fishnets with the smallest size mesh which is permitted by law; for the smaller the mesh size, the greater will be the catch. Thus, it becomes important that the dimensions of the mesh be as small as permissible and yet the knots of the netting must not slip to reduce the size of some of the meshes to a dimension below that permitted by law. It must also be appreciated that when one of the meshes is reduced in size due to slippage of a knot, there must be a corresponding enlargement of the adjacent mesh. This is equally undesirable because fish can escape through the enlarged mesh.

Numerous efiorts have been made to overcome the knot slippage problem inherent to the use of twines of synthetic resins by using twines which are coated or bonded with another and more compressible synthetic resin than that of the core resin, by the use of double knots and various special knots more resistant to slippage. These measures have met with some degree of success but suifer from one or more serious disadvantages including higher cost. In a highly competitive industry, the added cost of these devices to prevent slippage of the knots can be prohibitive.

The netting produced by the present invention possesses all of the advantages of netting made from thermo-sensitive synthetic resins, without the disadvantage of knot slippage and yet is produced very economically without the use of costly coatings, materials, equipment or manufacturing procedures. In addition, the meeting of the invention is significantly superior to netting made from a twine having a bonded coating in that it does not shrink nearly as much during normal usage. This net- 2,792,617 Patented May 21, 1957 ting is also unexpectedly superior in resistance to shrinkage when washed in lime water which is the common washing practice among commercial fishermen. Tests also show the netting of the invention to be more resistant to slippage at the knots than that made from a. twine bonded with a more compressible synthetic resin.

It is an object of the present invention to provide a netting of a thermo-sensitive synthetic resin which will not slip at the knots or shrink unduly during repeated usage and upon cleaning of the netting with hot lime water.

It is also an object of the present invention to provide economical and novel process and equipment for providing netting which will not slip at the knots.

Other objects and advantages of the invention will be apparent to those skilled in the art from a reading of the disclosure which follows and from the attached drawings.

The invention will be in part described by reference to the accompanying drawings.

In the drawings:

Figure 1 is a view of the weavers knot, which is the common knot used in the weaving of fishnetting.

Figure 2 is a view of the weavers knot (opposite side from that of Figure 1) which has not been treated by the process of the invention and which has been tipped by pulling the ends of the bend of the knot.

Figure 3 is a view of the two twines which had been tied into the weavers knot in a fishnetting and then untied without being treated in accordance with the process of the present invention.

Figure 4 is a view of the two twines which had been tied into the weavers knot in a fishnetting, the fishnetting treated in accordance with the process of the present invention, and then untied.

Figure 5 is a view of the weavers knot which has been loosened and enlarged to show the details of construction of the knot and to explain the test for evaluating the resistance to slippage of the knots treated under various circumstances.

Figure 6 is a diagrammatic side view of the apparatus of the invention showing the process of the fishnetting in accordance with the process of the invention.

Figure 7 is a diagrammatic plan view of the apparatus corresponding to Figure 6.

The present invention relates to nets, and particularly to fishnets, made with knotted meshes of a thermo-sensitive synthetic resin twine wherein the net is set in knotted form. it is contemplated that the twine of which the net is made shall be free of permanent bonding or coating such as of resinous or cementatory materials. Neither is it contemplated that the Woven or finished net shall have any permanent coating or bonding. The woven net of knotted meshes is set by the heat treatment of the invention so that the twines of which the net is woven shall assume the permanent configuration of the knots and the twines are brought into greater surface contact with the adjacent twines at the knots. The twine of which the nets of the invention are made, the individual components of the twine, are held in compact form by the twist, structure or contours of the twine and of its components. In the sense that the exterior of the filaments, staple-fibers, yarns, strands, threads, or other components of which the twines may be woven, twisted, cabled, etc., as well as the finished twine itself, is unbonded or free of any coatings of resinous or cementatory materials, it might be said that they are each of chemically substantially homogeneous cross-section or material which is of uniform compressibility throughout. It is contemplated that the twine and its individual components may contain small amounts of chemical delus trants, such as titanium dioxide, and diluting and plasticizing materials uniformly dispersed throughout the twine and each of its component parts. It Will be apparent to those familiar with the net-making art that the twine used may be manufactured of individual components or strands, yarns, threads, staple-fibers, filaments which are not each of the same thermo-sensitive synthetic resin. Thus, for example, the finished twine may be made by twisting filaments of nylon with filaments of Perlon or a difierent substance.

The invention also comprises a novel process for preparing netting of thermo-sensitive synthetic resins which comprises tensioning the woven net and passing the net, while tensioned, through a heating medium so that the knots are set therein. The preferred heating medium is hot water and best results are obtained with a bath of water, maintained at its boiling temperature. It is also preferred to pass the still tensioned netting through a second bath of cool or cold water promptly after passing through the hot water bath. A further improved feature of the pr cess is to tension the netting in the condensed form of a rope-like. or ribbon-like member. In other words, the netting is tensioned lengthwise in a manner designed to rnakethe netting as compact as possible during the process.

r The invention also comprises the'novel apparatus which will be describedin conjunction with the process of the invention which utilizes this equipmnt. The apparatus, shownin Figures 6 and 7, comprises essentially a machine having' an open-topped tank 1 to contain a hotfluid bath, an open-topped cooling fluid tank 2, a net beater 3,1 a net laying device. a, and a series of rollers, pulleys and drives for efiecting passage of the net through the machine.

The novel netting of the invention is intended to encompass only those nets which are woven in the form of; knots to hold the twines together. It is contemplated that the t'ivines woven into the he g be of thermo-sensitive synthetic resin material. This 'is a well defined class of materials known to the art. Certain types of thermosensitive synthetic resins are better known than others and an is particularly true of the (1) linear polyamide resins, also known generically as nylons, of which two important examples are polyhexametiylene adipamide, and caprolactam polymer, a commercial form of which is marketed under the trademark 'Perlon or Perlon L. Polyhexamethylene'adipamide is usually known simply as nylon and is sold under this name, although strictly speaking, the name nylon apphes to the whole group ot's ntlietic linear polyamide resins; (2) the acrylic resins, such as the polyacrylic esters and polyacrylonn e, the latterclass of which the well known Orlon is representative;'('3) the polyester type resins derived from polyhydric alcohols and polyoasic acids, such as the resins produced from the esters of ethylene glycol nrl terephthalic acid of which an example is known as T rylene or Dacron; (4) the vinyl resins and their copolymers, such as the copolymer of vi ylidene chloride and vinyl c .loride known commer lly as Saran; and (5) copolymers of any of the various types of resins referred to above, such as the resins formed by the copoiymerization of vinyl chloride and acrylonitrile, known as Vinyon-N and Dynel, or the copolymer of vinyl acetate and acrylcnitrile, known as Acrilan. As can be see, the preferred resin materials are polymers of unsaturated compounds capable of forming resins. Nylon and Terylene (or Dacron) are the most desirable materials ava able at present. Nylon is preferred because of its greater commercial availability. In general, it might be said that any plastic, or synthetic thermo-sensitive material, may be the subject of the netting and the process for making said netting resistant to slippage at the knots. V

The merino-sensitive s nthetic resins of the invention are to be distinguished from the sc-calied thereto-setting resins. class of resins beecrne rigid or hard when subjected to heat. They become-set or poly- T" ,1 1. no latter merize-whenheated and cannot be softened by subse-- quent reheating. The thermo-sensitive synthetic resins,

on the other hand, once polymerized to a given state do not become hard or rigid upon heating. When subjected to heat, they soften or become pliable, and they harden upon cooling. While these thermo-sensitive synthetic resins may be hard when in bulk, they are, nevertheless, flexible and'elastic when in' the form of extruded filamerits, or multifilament yarns and threads. The alternate heating and cooling of the thermo-sensitive resins may be ated again. and againwithout altering the chemi be. cture, so long as the temperature upon heating is not unduly high. 7

The term twine, as used in the specification, is intended to include twine, yarn, thread and strands or i "lCfitS of the resin. The twine may be made from .inuons filaments or from the form known as staple tioer. Twine made from staple fibers is lower in tensile strength, has a high elongation and is rougher. This roughness gives such a twine an inherent'resistance to knot-slippage. Therefore, the benefits of the present invention are primarily applicable to continuous filament twine although the invention is also applicable to staplefiber twine. Continuous filament twines are preferred.

The invention is especially applicable to fishing nets, but it will be understood that the nets may be produced or used for other purposes. Fishing nets, when produced in accordance with the invention, have been found highly satisfactory.

The twine used in the weaving and knotting of the makes the knots substantially immune to tipping or slippage. The process takes advantage of a setting phenomenon. Setting of the thermo-sensitive resin twine 'n' the netting is, in part, a change in the configuration of of their shape or configuration. the twine in the position of the knots, the netting twine will now resist any distortion of woven and knotted twine from the configuration in which it is set. This result enables one to produce a non-slipping netting without resorting to a costly bonding treatment.

The results produced by setting the woven netting may be illustrated with reference to the appended drawings. Figure 1 illustrates a single knot taken from a woven letting showing the so-calied weavers knot which is that most commonly used in the weaving of fishnetting. If the netting is not subjected to the process of the invention, upon'untying the'knot shown in Fig. l, the two strands appear as shown in Figure 3. It is quite apparent that the two strands have; not been distorted from their original connguration. Neither is there any change in configuration upon long usage under normal conditions of use. Nor will tightening of the knots be effective in distorting the permanent configuration of the two strands. On the other hand, when the woven netting is treated in accordance with the invention and then the knot of Figure l is untied, the two strands appear as in Figure The same results as shown in Figures 3 and 4 are also obtained if the strands in the knots are wetting by soaking in water either before or after untying the knots. It is quite apparent that a change in configuration of the two strands of twine has taken place and that the cross-section of the twine has been distorted. It is diificult to show such distortion in the drawings. The twine becomes soft or somewhat plastic during the heat-setting treat eat and since the knot is under some tension, the twine is distorted in cross-section to acconnnodate the adjacent twine of each knot. Each strand has become set to conform with the shape of the knot it forms. It is believed that this distortion phenomenon plays an important part in the resistance of nets according to the. present in- By means of setting.

E vention to slippage at the knots. The twine will remain in the shape set at temperatures less than that at which it was heat-set.

Resistance of netting to slippage at the knots is in part indicated by the resistance of the knots of the netting to tipping. The enhanced resistance to tipping of the knots treated according to the invention, may be shown by reference to the drawings. Figure 2 shows a knot such as that of Figure 1 (from the reverse side) which has been tipped. This knot had not been treated in accordance with the process of the invention, which explains the reason for easily tipping the knot. I have discovered that the knots of netting treated in accordance with the present invention are quite resistant to tipping. The susceptibility of the knots to tipping is evidenced by the ease with which the bight 56 of the knot tips over, as shown in Figure 2, when the ends 57 and S8 of the bend 55 of the knot are pulled apart. When the bight of the knot tips over, there is less tension brought to bear on the bend of the knot and it is most likely that slippage will occur.

Some thermo-sensitive synthetic resins, and particularly the various grades of nylon twines, which are the preferred resins for making the nettings according to the invention, also have a tendency to shrink during setting. This may result in an additional force for making the knots resistant to slippage. As the twine shrinks, there is a reduction of the length of the twine with a corresponding increase or swelling in the cross-section or diameter of the twine. Stated in another way, the twine must always displace a constant volume of a fluid. If the knots are held taut and in close contact during the setting treatment by means of tensioning of the netting as contemplated, this swelling of the diameter will result in a distortion of the cross-section of the twine causing it to be forced into inn'mate contact with the adjacent segment of twine and the resulting pressure caused by shrinkage forces the twines to assume a cross-section of crescent shape in places of most intimate contact. This aids in producing a knot more resistant to slippage.

In comparing the resistance of various netting to knot slippage, the critical test is, of course, the stability under long-term conditions of service. Long-term service tests suffer from two defects. First, they are time-consuming since a long period of time is often required before proof of stability is obtained. Secondly, service stability tests provide neither a precise comparison nor an absolute comparison between nettings. To overcome these undesirable shortcomings of relying solely upon service tests, a more precise analytical method has been developed.

This test will be explained by reference to Figure of the drawings. In conducting the test of the resistance of a particular knot to slippage, a weavers knot is first tied from two pieces of the twine to be tested as in Figure 5. Two ends of one twine 59 and 66 are held fast in one jaw of a tensioning machine and the ends of the

other twine

57 and 58 are fastened in the other jaw. Tension is applied to tighten the knot. Various degrees of tension may be applied, but for the twine sizes and the results to be described, 30 pounds was found satisfactory. It is desirable to apply as much tension as the weight of twine will permit without approaching the breaking point of the twine too closely. Of course, to provide a fair comparison of slippage resistance between various netting, the same weight of twine should be used and the same tension should be applied in all cases.

The tension is then released and the tightened knot is permitted to stand for three or four hours in the case of the dry test and for the wet test, the tensioned knot is immersed in water at room temperature for sixteen to eighteen hours. The two ends 59 and 60 of the bight 56 (twine which crosses over in the knot) are fastened securely in one jaw of the testing machine and end 57 of the bend 55 of the knot is secured to the other jaw. An

increasing load is applied in separating the two jaws until G the twine 51-58 begins to slip. The load required to cause slippage provides a comparison of the resistance of the knot to slippage. It is important that the same ends of the twines be subjected to the pulling in this test. In order to obtain results less subject to experimental error, it is advisable to take an average of at least 10 test knots for each type of netting. Of course, the greater the load required to produce slippage, the more resistant is the knot to slippage.

In accordance with the above-described test, knots of variously-treated nylon twines of 3150 total denier made by twisting five 210 denier yarns three of which are then cabled to make the finished twine, were tested for their resistance to knot slippage. Knots produced according to the present invention were compared with knots made of raw twine, boiled twine and twine permanently bonded with a more compressible thermoplastic resin, such as proposed in U. S. Patent 2,590,586 to Thompson et al. In preparing the knots according to the present invention for the test, it was, of course, necessary to subject the knots to the heat setting treatment of the invention. This was done by making the knot from twine coated with only a temporary binding agent and tensioning the knot at 30 pounds. The knot was dip ed in hot water at which time the temporary binding was washed away and chilled under various degrees of tension of 3 ounces, 9 ounces, 1% pounds and 3 pounds. Tests as to knot slippage were conducted in both the dry state and the wet state, as described above. Also, tests were made on twine which had been pre-boiled and dried to shrink the twine before the knot was tied. In the following table are given the results obtained with the various knots:

Load Required to Cause Knot Sllppage (in lbs.)

Twine Dry Wet Raw twine 6. 8 6.0 Boiled twine 7. 7 4. 4 Permanently bonded twine according to U. S. Patent 2,590 ass 10. 6 8.3

KNOTS SET IN ACCORDANCE WITH THE PRESENT It is believed apparent from the above results that netting according to the present invention is far superior to that of untreated twine and significantly superior to the costly twines coated with a permanent bonding of a more compressible thermo-sensitive synthetic resin. This has also been confirmed by tests under conditions of serv- 168.

The value of netting according to the invention is further demonstrated by its resistance to shrinkage during normal service and when washed with lime water. Various nettings were compared with respect to shrinkage by the following tests. To test comparative shrinkage under normal wetting in cold water, netting of raw nylon, nylon permanently bonded with a compressible thermoplastic resin bonding and netting prepared according to the present invention which had been tensioned to permit a shrinkage during the setting process of about 4.5% were subjected to the test to be described. In all cases the nylon netting was of the gilling type made from twine of 1260 total denier made by twisting two 210 denier yarns three of which are then cabled to make the finished twine. Samples of a given length of each netting were soaked in cold water for four hours, measured for length again, dried and measured for length again. Another set of samples of each netting were subjected to the lime water cleaning test, which is a repetition of the above test except for using a hot lime water bath instead of cold water. Cleaning in hot lime water is a common cleaning technique among commercial fishermen. The shrinkages obtained are indicated below:

Shrinkage in cold water 7 Shrinkage while Wet Shrinks go when T wine dry . Raw nylon .Nettmg of thermoplasti auentlv Nun I31 bonded twine according to U. S. Patent 3. Present invention 1.0% stretch Shrinkage in hot lime water at 180 F.

Shrinkage while wet Shrinkage when Twine 1. Raw nylon 2. Netting 0i thermoplastic permanently bonded twine according to U. S. Patent No. 2,590,586.

3. Present invention 0.5% stretch... 0.8%.

It is apparent from the above results that the netting of the present invention is significantly superior to netting of raw nylon twine and permanently thermoplastic resin bonded twine in resistance to shrinkage upon immersion and drying in cold water and vastly superior when cleaned in hot lime water.

In its broadest aspect, the novel process of the invention comprises first tensioning a woven netting'made of knotted meshes from a thermo-sensitive synthetic resin twine, and then while tensioned, passing the netting through a heating medium to set the knots of the nettin Although any heating medium, such as hot dry'air, steam or hot liquids may be used, hot water has been found to be significantly advantageous because of its ability to set the knots of the'netting without causing the yellowing or coloration often occurring with the use of hot air or steam. Presumably hot air and steam have a tendency to cause local overheating and decomposition of the resin. Water may easily be maintained at a uniform temperature, particuiarly at its boiling point, and since the netting may be immersed in the hot Water, all surfaces of the netting may bebrought into intimate contact with the'heat source and thus produce uniform heating of the netting. Additionally, hot water will accomplish the same degree of heat setting at a lower temperature than is required with hot air or steam. It is convenient to maintain the water bath at the boiling point by bubbling steam into it. This method also has the advantage of aiding in maintaining a constant level of water by replacing that lost in wetting the netting passing through the bath and by evaporation, with con-' densate resulting from heating of the bath.

After passing through the heating medium, the netting should remain tens-ioned until it has cooled'to some extent. it is particularly convenient to cool the netting by it through a tank of cold water, especially where hot water is used as the heating medium. If desired the 0 netting may be dried before the tension is released.

it has been found highly desirable to gather the woven nett ng as it comes from the weaving machine into a ribhon-like or rope-like form before passing-it through the apparatus for processing according to theinvention. By gathering the finished net into a rope-like member, his

. possible to use smaller equipment and it also facilitates the tensioning of the netting lengthwise while passing through the setting apparatus.

Optionally, the twine of therrno-sensitive synthetic resin material may advantageously be coated before weaving with a temporary binding agent or one adapted to increase the coefiicient of friction of the twine. When the netting is woven this temporary binding agent acts to resist any tendency of the knots to loosen. In this manner, the not can be left untensioned until such time as it is convenient to pass it through the setting machine. Thus, there is no necessity for the net to be passed immediately in a tensioned state from the weaving machine to the setting machine, but the nets, when formed, can be left stacked until a suitable number have accumulated and they can then be passed in succession through the setting machine. it will therefore be clear that one machine or a compar tively small number of machines are sufiicient to deal with the total output of a netting factory, thus resulting in a considerable saving in space, expense and the number of operators required. The nature of the temporary binding agent should desirably be such that it is rinsed from the netting while passing through the heat setting bath or by passing the netting through a tank of water which may or may not contain a detergent to wash off the temporary binding agent.

The nature of the temporary binding agent used is not critical as long as it minimizes any tendency for the knots to loosen before they have been heat-set and does not cause any undue difficulty in the weaving of the net. Suitable examples of temporary binding agents are as follows:

(1) A solution made up of:

10 gallons water,

2 lbs. textile (bar) soap, 7

10 lbs. Syton (a colloidal dispersion of about 14% silica in an aqueous medium), or,

(2) A rosin dip made up of:

1 /2 lbs. rosin soap, 3 oz. powdered rosin, and 3 gallons water.

It is quite important for successful operation of the process that the netting be under tension during the heat setting. Netting which has been set under tension is found to have compact or sharper twine and will gill fish well. The knots are set in a tightened condition and are thus less likely to slip during the life, of the fishnettin The twine of the resulting netting is exceptionally free from kinks or bends. By the use of tension as described it is possible to produce netting having good dimensional stability. Most of the thermo-sensitive synthetic resins, unless previously subjected to a heat-setting treatment, have a tendency to shrink upon heating, especially when heated in the presence of moisture. By tensioning during heat setting, excessive shrinkage may be prevented. For example, nylon twine immersed in boiling water without any tensioning will shrink about 9% of its length. In one particular example it was found that by subjecting the nylon netting to the degree of tension imposed by one particular unit of apparatus constructed in accordance with the apparatus of the present invention, the shrinkage was held to approximately 5% of the length of the twine. When employing a degree of tension sumcicnt to insure that the twine is kept sharp and that the knots are set in a fully-tightened condition, it is unusual for the degree of shrinkage to be substantially higher than 5 /2 in the case of netting woven from twine made from the types of nylon yarn at present on the market. It will, however, be readily understood that if the netting is made from a synthetic resin twine of different extensibility, or which shrinks to a different extent when immersed in boiling water without any tension, then the dimensional change occurring'during the knot-setting process according to the present invention may be substantially different. Also,

it will be understood that if the netting, or the twine from which the netting is made, has already undergone preshrinkage, for example, in dyeing, the passage of the net through the knot-setting machine will result in a lower shrinkage, and that in some cases there will be no shrinkage whatever, or even an increase in length, depending upon the amount of pre-shrinkage which has already occurred in the twine before passing through the machine according to the present invention, and depending, also, upon the amount of tension applied. In addition to preshrinkage, the degree of dimensional change which occurs is also dependent upon the structure and twist of the twine. The invention is therefore not limited to any particular degree of shrinkage or stretch occurring during the knot-setting process. By varying the diameter along the length of the'rollers and pulleys of the apparatus of the invention and/or by varying the relative peripheral speed between successive rollers or pulleys, selected conditions may be obtained which produce any desired degree of tension.

Netting treated in accordance with the present invention has the remarkable property of resisting progressive shrinkage when subjected to repeated wetting and drying such as in the normal usage of fishnetting; The treated netting of the invention is particularly resistant to shrinkage when washed with lime water which is a customary practice among fishermen. Untreated netting and netting made of twine bonded with a permanent coating of plastic material, on the other hand, are particularly vulnerable to shrinkage during normal usage and washing practices and do not possess the other desirable properties just stated.

in order more clearly to disclose the nature of the process of the present invention, the following description is intended to illustrate the preferred embodiment of the process. It should be understood, however, that this is solely in the nature of an example and is intended neither to delineate the scope of the invention nor limit the ambit of the appended claims. Reference numbers refer to Figs. 6 and 7 of the appended drawings.

In preparing the apparatus of the invention for processing the woven netting, a heavy nylon braided cord is fed through the apparatus to act as a guide cord. A heavy string is passed laterally through the first row of meshes of the net, looped, and then tied to the trailing end of the guide cord. This is to insure that the net passes through the machine with the various rows of knots aligned as closely as possible and so that the net is evenly tensioned throughout. A similar cord is attached to the end of the net for attachment to the string of a second net so that a whole series of nets may be continuously fed through the machine.

The net pulled by the guide cord is drawn from container 5, or unrolled from a drum, and passed in contact with the beater 3, which consists of two interspaced rotary discs 7 interconnected by two diametrically opposed rods 8 and 9, which beat against the net to loosen any tangles therein. The net then passes upwards between two fixed

rods

10 and 11 and around the latter and down and around a rod 12. In one embodiment of the invention, the net is brought into contact with the beater twice; once, when passing from rod 10 to rod 11, and again when passing from rod 11 to rod 12. The

rods

10, 11 and 12 efiect a certain amount of tension which causes the net to maintain a rope-like formation which it maintains throughout its passage through the machine. The net is then passed in succession around a series of rollers and pulleys 13 to 18, 2t and 21. Its path is clearly indicated by the dotted line A shown in Figure 6 of the drawings. The arrowheads indicate the direction of movement of the net during the process.

Pulleys

15 and 16 are respectively in the form of treble and double pulley or guide wheels, the sections of at least one of these being of successively increasing diameter. The net, in rope-like form, passes successively around the increasing diameter of the pulley and is increas ingly tensioned before passing down to and in a plurality of successiveloops around rollers 17 and 18. The path of the loops is defined by the guide fingers 19. To facilitate the unwinding of the rope-like member from the pulley 15 to pulley 16, the latter is angled slightly as shown in Figure 7. The rollers 17 and 18 are located within the tank 1 and at least one roller increases in diameter from one end to the other end so that the net in rope form is further tensioned during the actual knot setting which is efiected while the net is passed through a hot fluid, and preferably boiling water, in tank 1. It will be seen from Figure 6 that the roller 17 lies at an angle to roller 18 so as to eifect movement of the net from one end to the other. The arrangement of

pulleys

20, 21 is similar to

rollers

15, 16 and roller 21 is located so that it passes the net through cold water bath in tank 2.

From the roller 20, the ribbon passes into the net laying device 4. Device 4 consists of

concentric pulley wheels

22 and 23 and on the same axis as the

wheels

22 and 23 is a freely oscillating arm 24. At its lower end, the arm 24 carries pulley wheel 25 and two

small rollers

26 and 27 geared so as to be driven by pulley wheel 25.

Pulley wheels

23 and 25 are interconnected by a belt drive 28. The net in rope-like form passes around pulley wheel 22 down between

rollers

26 and 27 and from there is fed into receptacle 6. A disk rubber-covered roller 29 presses on top of the net as it passes over pulley wheel 22 and is mounted on a pivotal bar 30 which is loaded by a weight 31 in order to insure that tension is maintained up to this point. The oscillating motion of the arm 24 is efiected by a crank drive 32 and connecting rod 33 so that the lower end of arm 24 swings from end to end of the receptacle 6 and as the rope-like member is fed, from between

rollers

26 and 27, it is laid in superimposed layers in the receptacle.

A number of driving connections areprovided to drive the various rollers 15 to 18, 26 and 21 at appropriate speeds to assist in obtaining the desired degree of tensioning and to drive the beater 3 and net laying device 4. The driving connections are indicated by chain lines at 34 to 39; the main drive being at 34 from the electric motor 40. Stop means is provided at 42 to stop the machine should any portion of the net pass the heater 3 without being untangled. A thermostat is provided in tank 1 to insure that the water therein is kept at a desired temperature, which is preferably the boiling point of water. Also, tank 2 is preferably maintained with a continuous supply of fresh water to cool the net and complete the setting operation. Receptacle 6 may be provided with opposed slots 6A on each side wall and strings wound from one slot to the other across the receptacle so as to divide the net into easily carried portions and to minimize the possibility of entanglement of the nets.

Various degrees of tensioning may be efiected by varying the differential in diameters from one end to the other of

pulleys

15 and 16, as well as

rollers

17, 18, 20 and 21 so as to provide increased tension of the net as it passes through the machine. Also, it is possible to vary the degree of tensioning by varying the speed of the

pulleys

20 and 21 in relation to the speed of the

pulleys

15 and 16. It is the usual practice that any dimensional changes expected during the treatment are allowed for when the mesh is initially formed, and it is recommended that prior to commencing the process of the invention, a sample of the netting be first passed through the machine so that the dimensional change, if any, may be calculated for the particular supply of twine used. This has been found to be the most convenient method of ensuring that the treated netting is of the correct mesh size, but it will be understood that the dimensional changes occurring during knot-setting could also be controlled to some extent, if desired, by varying the amount of tension applied during the knot-setting process. The invention is not restricted as to the means for compensating or controlling dimensional change during processin The amount and direc tion of the dimensional change to be expected depends upon a number of factors, including the nature of the thermo-sensitive synthetic resin of which the twine is composed, the degree of thermo-sensitivity of the said resin, the extensibility and elasticity of the yarn components of the twine, the degree of twist imparted to the twine and its components, and the presence or absence of any pie-treatment given to the twine or its component strands, or to the netting, before the said netting is subjected to the knot-setting process of the present invention. Pretreatments which may be given to the twine or its components before weaving into netting which is to be subjected to the process of the present invention include treatment with steam, hot air, or other hot gas, or with hot or boiling liquids as for example in dyeing, but pre-treatment with Water-insoluble synthetic resin is excluded. Pro-treatment which may be applied to the woven net include treatment, untensioned, in hot water or other liquids, as, for example, in dyeing.

It is also contemplated that where desirable, the tensioning of the net may be continued While the net is being dried. Drying may be expedited by blowing a stream' of air over the tensioned net. 7

While the speed at which the net is passed through the machine is not normally critical, there is a maximum speed at which the net may be subjected to the setting treatment. This will depend primarily upon the weight of the twine of the netting, the type of thermo-sensitive synthetic resin and upon the temperature of the heating medium. The heavier the twine and the lower the temperature, the longer is the period required to set the nets. For example it has been found that where boiling water is used, a period of 30 seconds is satisfactory for netting a 420 denier nylon twine. For heavier twines, the net may be passed through the machine at a slower rate. A rate of 75 seconds for the heating period in the boiling Water in tank It has been found to be both a satisfactory rate for mechanical handling of most nets and also to effect satisfactory heat setting.

Although the water in tank 1 is preferably maintained at its boiling point and the cooling water in tank 2 maintained at the normal temperature of the available water supply, other temperatures may be satisfactorily used, providing that the temperature is high enough to set the resin. While the temperature of the heating and cooling water is not considered critical, it is preferred that they be kept constant throughout the operation so that the net is evenly treated throughout.

With reference to the treatment with a temporary binding agent aforementioned, it is to be understood that this is not essential to the invention, but may be employed where desired. it is either rinsed ofi in the tanks of the machine or washed oil at a later stage if necessary. Also, the removal of the temporary binding agent is not essential, but again is preferable, so that the nylon, for example, in the finished net may retain its natural and attractive lustre. When a temporary binding agent is not used, the net may or may not be held tensioned until required for the heat-setting process, this depending on the circumstances including the type of knot used.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expression, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

What is claimed is:

l. A method for continuously heat-setting lengths of netting knotted in mesh form from twines of a Waterinsoluble thermo-plastic synthetic resin capable of being heat-set, comprising gathering together the meshes laterally in rope-form so that the twines are in substantially parallel ali nment with each other and with the length wise direction of the netting, tensioning lengthwise the resulting narrow and laterally compact band of netting sufficiently to tighten the knots and passing it through a. heating medium maintained at a high enough temperature to heat-set the knots and twines of said netting until the twines and knots are heat-set and the knots resist slippage, to thereby heat-set the twines of the netting in substantially parallel alignment to each other and render the knots substantially resistant to slippage; said heating medium being chemically inert to and being capable of heat-setting said resin.

2. A method as defined by claim 1 for continuously heat-setting lengths of fishnetting knotted in mesh form from twines of a water-insoluble thermoplastic synthetic resin capable of being heat-set, wherein the fishnetting, after being heat-set, is subsequently promptly passed through an aqueous liquid cooling bath, while remaining tension lengthwise in the laterally compact form.

3. A method as defined by claim 1 for continuously heat-setting lengths offishnetting knotted in mesh form from twines of a water-insoluble thermoplastic synthetic resin capable of being heat-set, wherein the heating medium comprises a bath of water at substantially its a boiling point.

4. A method as defined by claim 1 for continuously heat-settinglengths of fishnetting knotted in mesh form from twines of a water-insoluble thermoplastic synthetic resin capable of bein heat-set, wherein the fishnetting, which has been gathered together laterally in rope form, is subjected to continuous and progressively increasing lengthwise tension while being passed through the heating medium.

5. A method as defined by claim 1 for continuously heat-setting lengths of fishnetting knotted in mesh form r from twines of a water-insoluble thermoplastic synthetic resin capable of being heat-set, wherein the netting is subjected to a temperature not in excess of the boiling point of water at atmospheric pressure during its treatment.

6. A method for continuously heat-setting lengths of fishnetting knotted in mesh form from twines of a waterinsoluble thermoplastic synthetic resin capable of being heat-set, comprising gathering together the meshes laterally in rope form so that the twines are in substantially parallel alignment with each other and with the lengthwise direction of the fishnetting, passing it through a bath of boiling water for a period of 30 to 75 seconds to heat-set the knots and the twines of said fishnetting, said fishnetting being subjected to suflicient progressively increasing lengthwise tension while in the boiling water bath to tighten the knots, to thereby heat-set the twines of the netting in substantially parallel alignment to each other and render the knots substantially resistant to slippage.

7. A method as defined by claim 1 for continuously heat-sealing lengths of fishnetting knotted in mesh form from twines of a water-insoluble thermoplastic synthetic esin capable of being heat-set, wherein the fishnetting is initially produced from twine coated with a temporary coating and slip-preventive agent having a greaterco efiicient of friction than that of the twines of the netting and which is water-dispersible and capable of being washed from said netting, which renders the knots of said netting substantially resistant to slippage prior to being heat-set.

8. A method for continuously heat-setting lengths of fishnetting knotted in mesh form from twines of a waterinsoluble thermoplastic synthetic resin capable of being heat-set, said twines being coated with a temporary coating and slip-preventive agent having a greater coefiicient of friction than said twines and which is water-dispersible and capable of being washed from said netting, comprising gathering together laterally the meshes of the fishnetting in rope form so that the twines are in substantially parallel alignment with each other and with the lengthwise direction of the fishnetting, passing it while in this condition through a hot aqueous liquid bath maintained at a temperature sufficient to heat-set the knots and the twines of said fishnetting until the twines and knots are heat-set and the knots resist slippage, said fishnetting being subjected to sufi'icient progressively increasing lengthwise tension while in said bath to tighten the knots, to thereby heat-set the twines of the netting in substantially parallel alignment to each other and render the knots substantially resistant to slippage.

9. A netting knotted in mesh form from twines of a water-insoluble thermoplastic synthetic resin capable of being heat-set, said netting having its plastic memory altered to the form in which said netting is placed during heat-setting with the knots rendered resistant to slippage and said netting having the tendency to return to a laterally gathered rope form condition, said netting being produced in accordance with the process defined by claim 1.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. A METHOD FOR CONTINUOUSLY HEAT-SETTING LENGTHS OF NETTING KNOTTED IN MESH FORM FROM TWINES OF A WATERINSOLUBLE THERMO-PLASTIC SYNTHETIC RESIN CAPABLE OF BEING HEAT-SET, COMPRISING GATHERING TOGETHER THE MESHES LATERALLY IN ROPE FORM SO THAT THE TWINES ARE IN SUBSTANTIALLY PARALLEL ALIGNMENT WITH EACH OTHER AND WITH THE LENGTHWISE DIRECTION OF THE NETTING, TENSIONING LENGTHWISE THE RESULTING NARROW AND LATERALLY COMPACT BAND OF NETTING SUFFICIENTLY TO TIGHTEN THE KNOTS AND PASSING IT THROUGH A HEATING MEDIUM MAINTAINED AT A HIGH ENOUGH TEMPERATURE TO HEAT-SET THE KNOTS AND TWINES OF SAID NETTING UNTIL THE TWINES AND KNOTS ARE HEAT-SET AND THE KNOTS RESIST SLIPPAGE, TO THEREBY HEAT-SET THE TWINES OF THE NETTING IN SUBSTANTIALLY PARALLEL ALIGNMENT TO EACH OTHER AND RENDER THE KNOTS SUBSTANTIALLY RESISTANT TO SLIPPAGE; SAID HEATING MEDIUM BEING CHEMICALLY INERT TO AND BEING CAPABLE OF HEAT-SETTING SAID RESIN.