DIE AND METHOD FOR MOLDING REINFORCING BAR

Abstract

A die for molding a reinforcing bar, which enables the production of a reinforcing bar having sufficient strength in a convenient and inexpensive manner, includes: a main flow channel (F1), formed in a central portion of a main body, that receives a molten thermoplastic polymer material (Rt) output from an extruder (2); at least one first sub flow channel (F2), formed in an outer peripheral portion of the main body, that receives the molten thermoplastic polymer material (Rt) and fluidly connects with an outer peripheral portion in the main flow channel (F1); and at least one second sub flow channel (F3) configured to receive reinforcing fibers (4) and fluidly connected with the main flow channel F1 upstream of a junction position of the main flow channel F1 and the at least one first sub flow channel (F2).

Claims

1. A die for molding a reinforcing bar, comprising: a main body; a main flow channel formed in a central portion of the main body and configured to fluidly communicate a molten thermoplastic polymer material output from an extruder; at least one first sub flow channel formed in an outer peripheral portion of the main body and configured to fluidly communicate thermoplastic resin material from the extruder, the first sub flow channel being fluidly connected to an outer peripheral portion of the main flow channel at a junction position within the main body; and at least one second sub flow channel defined in the main body and configured to guide reinforcing fibers into the main flow channel upstream of the junction position of the main flow channel and the at least one first sub flow channel.

2. The die according to claim 1, wherein: the main body is composed of a plurality of columnar dies that are coupled from an upstream side to a downstream side; and the main flow channel, the at least one first sub flow channel, and the at least one second sub flow channel are formed within one or more of the plurality of columnar dies.

3. The die according to claim 2, wherein: at least a downstream portion of the at least one first sub flow channel is configured as an entire-circumference channel having a ring-shaped cross section, and a diameter and a thickness of the entire-circumference channel reduce toward the downstream side.

4. The die according to claim 3, wherein the at least one second sub flow channel curves as the at least one second sub flow channel approaches the main flow channel.

5. The die according to claim 4, wherein the at least one second sub flow channel is a plurality of second sub flow channels that are respectively formed at a plurality of positions around a circumferential direction of the main body.

6. The die according to claim 5, wherein: the plurality of columnar dies comprises a supply die fastened to a junction die, the at least one first sub flow channel is a plurality of first through holes discretely extending through the supply die, and the first through holes are fluidly connected to the entire-circumference channel defined in the junction die.

7. The die according to claim 6, wherein the plurality of second sub flow channels is fluidly connected to the main flow channel within the supply die.

8. The die according to claim 7, wherein the entire-circumference channel fluidly connects with the main flow channel in the junction die.

9. The die according to claim 1, wherein: at least a downstream portion of the at least one first sub flow channel is configured as a conical channel having a ring-shaped cross section, and a diameter and a thickness of the conical channel tapers toward a downstream side of the main body.

10. The die according to claim 1, wherein the at least one second sub flow channel curves as the at least one second sub flow channel approaches the main flow channel.

11. The die according to claim 1, wherein the at least one second sub flow channel is a plurality of second sub flow channels that are respectively formed at a plurality of positions around a circumferential direction of the main body.

12. The die according to claim 2, wherein: the plurality of columnar dies comprises a supply die fastened to a junction die, the at least one first sub flow channel is a plurality of first through holes discretely extending through the supply die, and the first through holes are fluidly connected to the entire-circumference channel defined in the junction die.

13. The die according to claim 12, wherein the plurality of second sub flow channels is fluidly connected to the main flow channel within the supply die.

14. The die according to claim 13, wherein the entire-circumference channel fluidly connects with the main flow channel in the junction die.

15. The die according to claim 14, further comprising: a plurality of nozzles upstream of the respective second sub flow channels, wherein the nozzles are configured to each loosen a plurality of reinforcing fibers prior to supplying the reinforcing fibers to the respective second sub flow channels.

16. The die according to claim 1, further comprising: a nozzle upstream of the at least one second sub flow channel, wherein the nozzle is configured to loosen a plurality of reinforcing fibers prior to supplying the reinforcing fibers to the at least one second sub flow channel.

17. A method for producing a reinforcing bar, comprising: supplying a molten thermoplastic polymer material into the main flow channel and the at least one first sub flow channel of the die according to claim 1, supplying a plurality of reinforcing fibers into the at least one second sub flow channel of the die, and forming the reinforcing bar inside the main body such that the reinforcing fibers are impregnated with the thermoplastic polymer material in a central portion of the reinforcing bar and an outer layer of the thermoplastic polymer material surrounds the central portion.

18. The method according to claim 17, wherein: the thermoplastic polymer material comprises one or more of polypropylene, nylon and/or polyester, and the reinforcing fibers comprise one or more of basalt fibers, glass fibers, carbon fibers, aramid fibers and/or acrylic fibers.

19. The method according to claim 18, further comprising: prior to supplying the reinforcing fibers into the at least one second sub flow channel, loosening the reinforcing fibers by passing the reinforcing fibers through a nozzle while supplying pressurized air into the nozzle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic perspective view showing the overall configuration of a reinforcing bar producing device provided with a die for molding a reinforcing bar according to one representative embodiment of the present teachings.

[0021] FIG. 2 is an overall vertical cross-sectional view of the die for molding a reinforcing bar according to FIG. 1.

[0022] FIG. 3 is a vertical cross-sectional view of a supply die.

[0023] FIG. 4 is a front view of the supply die, as viewed in the direction of an arrow X in FIG. 3.

[0024] FIG. 5 is a vertical cross-sectional view of a junction die.

[0025] FIG. 6 is a front view of the junction die, as viewed in the direction of an arrow Y in FIG. 5.

[0026] FIG. 7 is a vertical cross-sectional view of a covering die.

[0027] FIG. 8 is a vertical cross-sectional view of a molding die.

[0028] FIG. 9 is a cross-sectional view of a nozzle for loosening, separating, or otherwise introducing spaces (gaps) between, the reinforcing fibers.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0029] It is noted that the representative exemplary embodiment described below is merely an example, and various design improvements, which may be made by one of ordinary skill in the art without departing from the spirit of the present invention, are also encompassed within the scope of the present teachings.

[0030] FIG. 1 shows the overall configuration of a reinforcing bar producing device provided with a die 1 for molding a reinforcing bar (hereinafter referred to as “die for molding 1”) according to the present teachings. In FIG. 1, an extruder 2 having a well-known structure is provided, and polypropylene (PP) Rt, which serves as the thermoplastic polymer (resin) material, is supplied from a charging hopper, which is mounted on an upper face of one end of extruder 2, into the extruder 2. The PP Rt is heated to a predetermined temperature to bring it into a molten state in the extruder 2, and then the molten PP is supplied into the die for molding 1, which is described below in greater detail, coupled (fastened) to the other end of the extruder 2 by one or more screws, bolts, etc., provided therein.

[0031] A mold main body of the die for molding 1 has a generally columnar shape and is constituted by coupling (joining, fastening) four separately-manufactured dies, namely: a supply die 11; a junction die 12; a covering die 13; and a molding die 14. An overall cross-sectional view of the die for molding 1 is shown in FIG. 2. FIG. 3 shows a vertical cross-sectional view of the supply die 11, and FIG. 4 shows a front view of the supply die 11, as viewed in the direction of arrow X in FIG. 3. A first end face 11a of the supply die 11 (left side in FIG. 3) includes a bulging central portion 115 that bulges in a mountain (peak, truncated conical) shape. The first end face 11a is attached to the output end of the extruder 2 so as to cover an outlet opening 21 in the extruder 2. A central through hole 111 is formed in (extends through) the center of the supply die 11 and penetrates (extends) from the first end face 11a to a second (opposite) end face 11b of the supply die 11. The central through hole 111 further penetrates through the center of a guide portion 112 that protrudes from the central portion of the second end face 11b of the supply die 11. The outer diameter of the guide portion 112 reduces (tapers) toward the forward end (right side in FIG. 3) thereof.

[0032] At least two first through holes 113 (eighteen first through holes 113 are shown in FIG. 4, although more or fewer first through holes 113 may be provided in the supply die 11, e.g., 2-30 first through holes 113, preferably 10-25 first through holes 113) penetrate through the supply die 11 to the second end face 11b and are arranged at intervals around a circumference (periphery) of the bulging central portion 115. In addition, multiple second through holes 114 (two second through holes 114 are shown in FIG. 4, although more second through holes 114 may be provided in the supply die 11, e.g., 3-8 second through holes 114, preferably 2 or 4 second through holes 114) are formed in the supply die 11 and respectively extend from radially symmetric positions on an outer peripheral surface of the supply die 11 toward the central (interior) portion of the supply die 11, in a curved manner in the vertical cross section. These second through holes 114 reach the central (interior) portion of the second end face 11b, where the second through holes 114 open into and join (fluidly communicate with or fluidly connect to) the central through hole 111.

[0033] FIG. 5 shows a vertical cross-sectional view of the junction die 12, and FIG. 6 shows a front view of FIG. 5 as viewed in the direction of arrow Y shown in FIG. 5. A central through hole 121 is formed in the center of the junction die 12. The central through hole 121 has a larger opening in an inner peripheral portion of a first end face 12a, and the diameter gradually reduces (tapers) toward the second end face 12b while extending through an inner peripheral portion 122, which protrudes in a round shape. That is, the central through hole 121 is cone-shaped and has a shape that substantially matches (follows) the cone-shaped guide portion 112 of the supply die 11, as will be further explained below.

[0034] FIG. 7 shows a vertical cross-sectional view of the covering die 13. The covering die 13 has a round concave area 131, which is recessed in an inner peripheral portion of a first end face 13a by a predetermined depth. A central through hole 132 penetrates through to a second end face 13b and is formed (opens) in a central portion of the round concave area 131. At least two positioning bolts 133 are inserted from the external side into a peripheral wall of the round concave area 131 at a plurality of equispaced positions in (around) the circumferential direction.

[0035] FIG. 8 shows a vertical cross-sectional view of the molding die 14. A central through hole 141 is formed in the center of the molding die 14 and is configured to gradually reduce (taper) in diameter from the side of a first end face 14a to match the intended external diameter of a reinforcing bar (rebar) that will be produced as the end product.

[0036] The supply die 11, the junction die 12, the covering die 13, and the molding die 14 as described above are coupled (joined, fastened together) as follows. The protruding guide portion 112 of the supply die 11 (FIG. 3) is inserted into the central through hole 121 of the junction die 12 (FIG. 5). Then, bolts are respectively inserted into each of bolt holes 123 (FIG. 6) provided at regular intervals in an outer peripheral portion of the junction die 12 until reaching into each of bolt holes 116 (FIG. 4) provided at regular intervals in an outer peripheral portion of the supply die 11. The bolts are then respectively screwed into each of screw holes (not illustrated) provided in a circumference of the outlet opening 21 of the extruder 2. The molding die 11 and the junction die 12 are thus integrally fixed to the extruder 2.

[0037] Then, the protruding inner peripheral portion 122 of the junction die 12 is inserted into the round concave area 131 of the covering die 13. Thereafter, bolts are respectively inserted into each of bolt holes 134 (FIG. 7) provided at regular intervals in an outer peripheral portion thereof, and then screwed into each of screw holes 124 (FIG. 6) provided at regular intervals in the inner peripheral portion 122 of the junction die 12, to thereby couple and fix the covering die 13 to the junction die 12. During this mounting operation, a forward end of the protruding guide portion 112 of the supply die 11 enters the central through hole 132 of the covering die 13.

[0038] Bolts are then respectively inserted into each of bolt holes 142 (FIG. 8) provided at regular intervals in an outer peripheral portion of the molding die 14, and then screwed into each of screw holes 135 (FIG. 7) provided at regular intervals in the inner peripheral portion of the covering die 13, to thereby couple and fix the molding die 14 to the covering die 13.

[0039] Thus, the die for molding 1 is assembled by coupling the supply die 11, the junction die 12, the covering die 13 and the molding die 14 as described above, and fixing the die for molding 1 to the outlet opening 21 of the extruder 2 (FIG. 2). In this assembled state, the main flow channel F1 is formed by the central through hole 111 of the supply die 11 and the central through hole 141 of the molding die 14, which are fluidly connected with each other. In addition, the first sub flow channel F2, which fluidly connects to the outer peripheral portion in the main flow channel F1 at the border (junction) with the molding die 14, is formed by fluidly connecting: (a) the first through holes 113 of the supply die 11, (b) a gap 125 formed between the outer (conical) periphery of the guide portion 112 of the supply die 11 and the inner (conical) periphery of the central through hole 121 of the junction die 12, and (c) a gap 136 formed between the outer (conical) periphery of the forward end of the guide portion 112 of the supply die 11 and the inner (conical) periphery of the central through hole 132 of the covering die 13.

[0040] Here, it is noted that at least the downstream portion of the first sub flow channel F2 is an entire-circumference (conical, single continuous, endless) channel having a ring-shaped (endless) cross section that gradually reduces (tapers) in diameter in the junction die 12 and leads to the interior of the covering die 13, where a ring-shaped cross section having a desired diameter and a desired thickness (radial width) is obtained. In addition, the second through holes 114 extend in a curved manner through the supply die 11 and join (fluidly connect with) the main flow channel F1 in the central portion of the second end face 11b of the supply die 11 on the upstream side of the junction position of the main flow channel F1 and the first sub flow channel F2, to form the second sub flow channels F3.

[0041] Referring to FIG. 1, the reinforcing fibers may be incorporated (embedded) into the reinforcing bar 9 as follows. Basalt fiber bundles (twisted fibers) 4, which serve as the reinforcing fiber material, are respectively drawn from a pair of coils 3 and are respectively supplied to the two second sub flow channels F3 (second through holes 114) that open on (at) the outer periphery of the supply die 11. Then, the basalt fiber bundles 4 respectively pass from the second sub flow channels F3 into the main flow channel F1 joined (fluidly coupled) to the second sub flow channels F3. After exiting the die for molding 1, the basalt fibers (when disposed in the reinforcing bar 9) pass through cooling water 51 in a cooling device 5 in the subsequent stage; and then the reinforcing bar 9 (with the basalt fibers disposed therein) is pinched vertically by a pulling belt 6 in the last stage, to pull the reinforcing bar 9 forward out of the die for molding 1. In this example, the thickness of each basalt fiber bundle 4 may be 4,800 TEX.

[0042] It is noted that the basalt fiber bundles 4 drawn from the pair of coils 3 are respectively passed through two nozzles 7 as shown in FIG. 9, and are loosened (separated) by pressurized air 71 supplied thereto in a direction at least substantially perpendicular to the extension direction of basalt fiber bundles 4. That is, each basalt fiber bundle 4 may be provided in the form of a plurality of basalt filaments that are twisted together. By loosening the twisted structure, gaps or spaces are provided between individual basalt filaments in the bundle so that the molten thermoplastic polymer can more easily infiltrate (impregnate) between the respective filaments of each basalt fiber bundle 4. The basalt fiber bundles 4 loosened (separated) by this fiber loosening process are then each supplied to the respective openings of the second sub flow channels F3 (second through holes 114) via respective tension rollers 8. For facilitating understanding, the positions of the openings of the second sub flow channels F3 shown in FIG. 1 are different from the position of those openings in reality.

[0043] In this state, while the pulling belt 6 is pulling the basalt fiber bundles 4 in a straight manner without twisting, molten PP Rt is supplied from the extruder 2 into the main flow channel F1 and into the first sub flow channel F2 of the die for molding 1. To the molten PP Rt flowing in the main flow channel F1, the loosened basalt fiber bundles 4 described above are supplied from the second sub flow channels F3 that join in the middle, whereby the PP Rt is caused to infiltrate (impregnate) between the basalt fibers in a thorough and advantageous manner. Then, at a downstream position, molten PP Rt is also supplied from the first sub flow channel F2 to the outer periphery of the basalt fibers impregnated with the molten PP Rt in the central portion, so as to cover the outer circumference of the basalt fibers. After cooling in the cooling device 5 in the subsequent stage, a reinforcing bar 9 (FIG. 1) having sufficient strength is obtained, in which the basalt fibers impregnated with the PP Rt are positioned in a central portion and a predetermined thickness of the PP Rt evenly covers the outer periphery (circumference) of the central portion of the reinforcing bar 9. The diameter of the reinforcing bar 9 may be, e.g., approximately 5 mm, the diameter of the central portion may be, e.g., approximately 4 to 4.5 mm, and the tensile strength of the reinforcing bar 9 thus obtained is preferably about 15 kN.

[0044] It is noted that, although the second sub flow channels are formed at two radially symmetric positions in the circumferential direction in the above-described embodiment, supply of the reinforcing fibers in small portions to the main flow channel permits the thermoplastic polymer (resin) material to advantageously infiltrate (impregnate) between the reinforcing fibers. Therefore, it is preferred to form second sub flow channels at two to four positions in the circumferential direction, to minimize complexity of the die.

[0045] In addition or in the alternative to PP, the thermoplastic polymer (resin) material of the above-described embodiment may be or include, e.g., polyethylene, nylon, polyester, or the like. In addition or in the alternative to basalt fibers, the reinforcing fibers may be or include another type of inorganic fiber, such as, e.g., glass fiber or carbon fiber, and/or may be an organic fiber such as aramid fiber or acrylic fiber.

[0046] According to the embodiment as described above, the overall size of a device for making a fiber reinforced polymer reinforcing bar can be reduced by eliminating a storage tank for molten polymer, thereby leading to a reduction in production costs as compared to conventional dipping (immersion) methods, whereby production of a reinforcing bar having sufficient strength in a relatively convenient and inexpensive manner is enabled. Note that the specific structure of the die for molding is not necessarily limited to that shown in FIG. 2.

[0047] Additional teachings that may be advantageously utilized together with the teachings of the present application, such as compositions, sizes, arrangements, etc. of suitable thermoplastic polymers, reinforcing fibers, etc., are disclosed in U.S. patent application Ser. No. 17/464,996, the contents of which are fully incorporated herein by reference.

[0048] Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved dies for molding a reinforcing bar and methods of using the same.

[0049] Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

[0050] All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.