The present invention relates to a method for producing a thermoplastic resin string roll, more specifically, to a method for producing a thermoplastic resin string roll without a core.
One example of a method for producing a thermoplastic resin string roll without a core is disclosed in JP 2000-344422A. With this method, a through-hole is provided in stacked resin string layers inside of a coil, and the resin string is connected by integrating the periphery of the through-hole. As a method of forming a through-hole and integrating the resin string in this manner, a method of penetrating and integrating in the diameter direction from the center of the coil, using a heated needle in the process of winding, a supersonic welding method and the like are disclosed.
In the method using a heated needle, as shown in
On the other hand, in a supersonic welding method, as shown in
Moreover, in structures provided with such an anvil, as in
On the other hand, it is possible to constitute a structure without an anvil, for example a structure where the horn 134 is inserted from the inside, as shown in
Further, in the case where the end shape of the horn is round, as shown in
Concerning thermoplastic resin strings used for packaging, in the case where the packaged goods are heavy goods, strings made of polyester are used for that. The important thing about such polyester strings is obviously that they are able to stand the heaviness of such packages.
That means that as the coreless rolls of thermoplastic resin strings, for example, polypropylene strings or polyester strings can be used, but it is preferable to constitute a structure, considering the characteristics and usage of these materials. In the following, the characteristics of these materials and the problems in the case of using such materials as packaging strings will be explained.
Table 1 below shows the respective characteristics of polypropylene strings and polyester strings. The diameter d of the through-hole of each string is 1 mm and the string width w is 15.5 mm.
In case a method is used that integrates the peripheral portion of a through-hole in a thermoplastic resin string for bonding, in the case of polypropylene strings, the intensity decreases by 1 mm (diameter a)/15.5 mm (band width b) as shown in Table 1, while in the case of polyester strings, the intensity decreases by (1 mm or more/15.5. mm), which is a decrease of the hole diameter or more. That means, as for polypropylene thermoplastic resin strings, because stretching fiberization proceeds in the longitudinal direction (direction L in
In view of the conventional technology described above, the present invention has a first object to provide a method for producing a coreless roll of a thermoplastic resin string, in which no collapses inside of the coreless roll of the thermoplastic resin string, no vertical splits of the string or no thread drawn from the string surface occur while in use. Furthermore, it is a second object to realize a coreless roll of a thermoplastic resin string, in the case where a polyester string is used as the thermoplastic resin string, whose tensile strength decrease is low, and that have an appropriate peel strength, and thereby to provide a method for producing a coreless roll that allows the string to be drawn smoothly out of the reel of a baler.
In order to achieve the above-described objects, a method for producing a thermoplastic resin string roll of the present invention includes using a core made of a plurality of core pieces that are arranged along a circumference and can move back and forth in a diameter direction, the outer faces of the core pieces forming a part of a cylinder when the core pieces are extended in the diameter direction; fixing an end of a thermoplastic resin string while the core pieces of the core are extended in the diameter direction, rotating the core to wind the thermoplastic resin string a plurality of times around the periphery of the core; applying supersonic vibration to a plurality of layers of the thermoplastic resin string that is wound round the core via a horn, thereby causing frictional heat, so that the plurality of layers of the thermoplastic resin string are connected by thermal fusion due to the frictional heat; and winding continuously the thermoplastic resin string, wherein the plurality of layers of the thermoplastic resin string are connected by inserting the horn in the thermoplastic resin string and drilling while melting.
This constitution may be such that a core in which a groove is formed on the outer face of each of the core pieces may be sued, and the horn is inserted in the plurality of layers of the thermoplastic resin string that cover the groove, and the plurality of layers of the thermoplastic resin string is drilled while being melted, to form a through-hole that penetrates the plurality of layers of the thermoplastic resin string that cover the groove.
With this constitution, where the horn penetrates a plurality of layers of a thermoplastic resin string, the stretched fibered layer can be divided so that no thread is drawn.
Furthermore, in the above constitution, a contact portion of the horn may be in the peripheral surface of the plurality of layers of the thermoplastic resin string, and the thermoplastic resin string may be drilled from the peripheral surface toward the inner surface while being melted.
With this constitution, for example, as shown in
In this constitution, it is preferable that in a method of forming a through-hole, the horn has a cylindrical shape, and the diameter thereof is 1 mm or less. This is because the peel strength of the string becomes larger as the periphery of the horn becomes longer, so that when the diameter exceeds 1 mm, the string tears easily.
Furthermore, instead of the above constitution in which the through-hole is formed, the thermoplastic resin string may be drilled while being melted by inserting the horn in one outermost layer of the plurality of layers of the thermoplastic resin string to a depth of insertion that does not reach the thickness of the outermost layer of the thermoplastic resin string.
With this constitution, the through-hole is not formed in the string, so that the decrease in the tensile strength is low and an appropriate peel strength can be obtained.
Furthermore, in this constitution, it is preferable that the depth of insertion is ⅘ or less of the thickness of the outermost layer of the thermoplastic resin string in view of the tensile strength.
In this constitution, it is preferable that the horn has a cylindrical shape, and the diameter thereof is 2 mm or less. This is because the diameter of 2 mm corresponds to the upper limit of the peel strength.
In the above constitutions, that is, either a constitution in which a through-hole is formed or a constitution in which a through-hole is not formed, it is preferable that the plurality of layers of the thermoplastic resin string that are to be connected are two layers. This is because when a bonding process is performed to three or more layers of the thermoplastic resin string, an interface tends to be formed between the melted junction and the string constituted by a stretched fibered layer, which can be avoided with this constitution.
Furthermore, it is preferable that the horn has a flat end surface. With this constitution, the melting volume is substantially constant, and little resin can enter the gaps of the string, so that the fused portion can be formed stably. In addition, surplus resin can be discharged efficiently.
FIGS. 1(a)-1(e) are diagrams that explain the structure of a relevant portion of Embodiment 1 of the present invention over time.
FIGS. 5(a)-5(g) are diagrams that show the method for producing rolls of Embodiment 1 of the present invention over time.
FIGS. 6(a)-6(c) are diagrams that explain the structure of a relevant portion of Embodiment 2 of the present invention over time.
A roll produced by a production method of an embodiment of the present invention is formed by multiple windings of a thermoplastic resin string with a hollow portion formed. This thermoplastic resin string is made of olefin resin of polypropylene that has been stretched about 5 to 10 times so that the tensile strength has been remarkably increased, and thermoplastic resin strings having a width of about 10 mm to 20 mm and a thickness of about 0.3 to 1 mm are usually often used. For the thermoplastic resin string, any materials that increase the tensile strength through stretching, for example, polyester or polyamide can be used. Such a thermoplastic resin string being wound up to 1000 m to 2500 m makes one roll. Regarding the measures of this roll, the width is about 100 mm to 250 mm, the inner diameter is about 200 mm to 410 mm, the outer diameter is about 300 mm to 650 mm, and the weight is about 10 kg to 25 kg. In a roll formed by multiple winding of the thermoplastic resin string in coil shape without a core, the thermoplastic resin string that is stacked in the vicinity of the end portion at the beginning of the roll is mutually connected so as to form a loop element.
Hereinafter an embodiment in which the supersonic welding method is used in the process for forming the loop element will be described with reference to the drawings.
<First Embodiment >
In this production method , winding of a thermoplastic resin string 11 is performed, using a core 2 and a supersonic welding machine 1. This supersonic welding machine 1 is provided with a cylindrical horn 10 as shown in
Hereinafter, the production method of the present invention will be explained.
First, as shown in
Then, as shown in
Moreover, as shown in FIGS. 1(c) and 5(d), only the resin 13, which is of the resin amount that is necessary for bonding remains in the space between the thermoplastic resin string 11a and the thermoplastic resin string 11b, and the needless surplus of the resin 13a is pushed to the groove 21 of the core piece and is discharged into the inside of the thermoplastic resin string 11. Through the process described above, the two layered thermoplastic resin string 11 is melted for bonding, and connected.
Furthermore, as shown in
Thereafter, the core 2 is rotated slightly and, as shown in
After the thermoplastic resin string 11 is melted for bonding at a plurality of different positions in this manner, as shown in
<Second Embodiment >
In this embodiment, a method for producing a coreless roll in the case of using a polyester string as a resin string that is used for packaging heavy goods will be explained.
As described above, polyester strings have the characteristic that fiberization does not proceed in the longitudinal direction as much as polypropylene strings, and therefore tear easily in the width direction. In case of such a polyester string, in the production process shown in
In this embodiment, as shown in FIGS. 6(a) and 6(b), supersonic vibration (15 to 60 kHz) is applied while the end of the horn 10 of the supersonic welding machine 1 is pressed against the peripheral surface of the thermoplastic resin string 11b wound around the core 2, and the horn 10 is inserted only in the first layer of the thermoplastic resin string 11b. It is preferable that the depth h of insertion of the horn 10 is not greater than ⅘ of the thickness of the thermoplastic resin string 11b from the aspect of tensile strength. Then, as shown in
By the process described above, a melted junction portion 19 is formed between the thermoplastic resin string 11a and 11b.
Similarly to Embodiment 1, the bonding process is performed to each of the core pieces 22 . . . 22, and then as shown in
The tensile strength of the fused portion in an automatic baler with a polyester string is about 90% of the strength of the material, and it is believed that the tensile strength retention necessary for practical use is 90% or more. Moreover, the peel strength is preferably 200 gf or more, but not more than 1500 gf so that the roll does not collapse. From this point of view, in the production method of Embodiment 2, the ratio of the thickness of the thermoplastic resin string to the insertion depth of the horn is 0.8% or less, and it is verified that if it is 0.8% or less and not less than 0.35%, the decrease of the tensile strength is low and the peel strength is appropriate.
On the other hand, in the method of production in Embodiment 2, in the case where a through-hole is provided in the thermoplastic resin string, as evident from
In particular, in the case where a horn diameter of 0.5 mm is used, no satisfying results can be achieved, concerning the tensile strength retention and the peel strength.
The horn 10 that is used in the above embodiments is constituted by a titanium alloy, but the present invention is not limited thereto, and can be made of a material such as iron.
As described above, the method for producing a coreless roll of a thermoplastic resin string of the present invention can produce a coreless roll of a thermal plastic resin string in which the inside of the coreless roll of a thermoplastic resin string does not collapse, the string can be pulled out of the baler reel smoothly while in use, no threads is drawn from the surface, and no vertical splits occur in the string. Furthermore, also in the case where a polyester string is used for the thermoplastic resin string, a coreless roll that has a low decrease of tensile strength and an appropriate peel strength can be produced. Therefore, it is possible to use up the roll of a thermoplastic resin string to the end, which is economical. Furthermore, the present invention is useful in that by applying the production method of the present invention as appropriate, depending on the material of the thermal plastic resin string, the present invention can be used also for packaging heavy goods.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP03/06083 | 5/15/2003 | WO | 11/10/2005 |