Pelletizer

Abstract

To provide a pelletizer that can smoothly draw in a strand to be supplied even if the strand is made of a flexible material, and can easily set a leading edge of the strand at the start of operation.SOLUTION: The pelletizer includes: a strand pulling-in device 4 having a first roller 41 and a second roller 42, and for pulling in a plurality of strands extruded from an extruder and conveyed while being cooled by a strand cooling device 2; a cutting device 5 for cutting the plurality of strands pulled in by the strand pulling-in device 4 into a granular state; and a drive roller conveyor 6 installed between the strand cooling device 2 and the strand pulling-in device 4 so that the strands to be conveyed by the strand cooling device 2 toward between the first roller 41 and the second roller 42, and having a plurality of drive rollers and a non-contacting power transmission device for transmitting rotation power by a motor to the plurality of drive rollers by a magnetic force in a non-contact manner.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pelletizer (also called a strand cutter) that cuts a string-like resin strand into pellets. [Background technology]

[0002] One of the methods for producing pellets, which are the raw material for resin products, is the strand cut method, which involves kneading and melting resin material and additives in an extruder, forming the molten resin into string-like resin (strands) and extruding them from a multi-hole die attached to the tip of the extruder, transporting the strands to a pelletizer while cooling them, and cutting the strands into granular pellets by the pelletizer (see, for example, Patent Documents 1 and 2).

[0003] In this case, a device (hereinafter referred to as a strand cooling device) is installed between the pelletizer and the extruder to cool the strands extruded from the extruder and supply them to the pelletizer. One example of this strand cooling device is a configuration in which a water cooling device that sprays cooling water onto the upstream side (extruder side) of a conveyor using a mesh belt is provided, and an air cooling device that sprays cooling air onto the downstream side of the conveyor is provided (see, for example, FIG. 1 of Patent Document 1, etc.). In this case, the strands extruded from the extruder are placed on the conveyor and transported toward the pelletizer, and during this transportation, the water cooling device sprays cooling water onto the strands on the conveyor on the upstream side of the conveyor, and the air cooling device sprays cooling air onto the strands on the downstream side. As a result, the strands reach the pelletizer after their surfaces are cooled to a solidified state.

[0004] Another example of a strand cooling device is one having a water tank that holds a cooling liquid for cooling the strands, and multiple guide rollers that guide the strands in the cooling liquid are provided in the water tank (see, for example, FIG. 8 of Patent Document 2). In this case, multiple strands extruded from the extruder are guided by multiple guide rollers in the cooling liquid in the water tank and transported toward the pelletizer. The strands reach the pelletizer after passing through the cooling liquid, where the surface is cooled to a solidified state.

[0005] Fig. 4 is a side view showing an outline of the internal structure of the main part of a conventional pelletizer. The pelletizer 31 shown in Fig. 4 includes a strand drawing device 4 that draws in a plurality of strands St and sends them out to a cutting device 5, and a cutting device 5 that cuts (shears) the strands St sent out from the strand drawing device 4 to a predetermined length. The strand drawing device 4 and the cutting device 5 are provided with safety covers 40, 50, respectively.

[0006] The strand pull-in device 4 includes a first roller 41 and a second roller 42 that is vertically displaceable within a predetermined range. The second roller 42 is disposed above and facing the first roller 41, and rotates in the opposite direction to the first roller 41. The first roller 41 is rotated by a motor. The second roller 42 may be rotated by a motor, or may be driven in response to the rotation of the first roller 41.

[0007] The strand cooling device described above is installed upstream of the pelletizer 31, and the strand St sent from the strand cooling device is clamped between the first roller 41 and the second roller 42, and is drawn in by the rotation of the first and second rollers 41, 42, sliding on the strand sliding table 43 and sent to the cutting device 5. At this time, the strand St sent from the strand cooling device passes over a rotatable roller 102, slides on a stainless steel chute plate 101 installed in front of the first and second rollers 41, 42, passes between the first and second rollers 41, 42, and is sent to the cutting device 5.

[0008] The cutting device 5 includes a rotary blade 51 and a fixed blade 52. The fixed blade 52 is fixed to the end of the strand sliding base 43 on the rotary blade 51 side. The rotary blade 51 is configured as a drum-type cutter, and multiple cutting edges 51b are formed at regular intervals in the circumferential direction of the drum. The strand St is fed onto the fixed blade 52 by the rotation of the first roller 41 and the second roller 42, and the strand St is continuously cut to a predetermined length by the rotary blade 51 rotating at high speed, thereby continuously producing granular (cylindrical) resin pellets. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2021-70302 [Patent Document 2] JP 2021-130289 A Summary of the Invention [Problem to be solved by the invention]

[0010] In the above-mentioned conventional pelletizer 31, a plurality of strands St sent from a strand cooling device in a preceding stage are transferred by sliding on a stainless steel chute plate 101, and are drawn between the first and second rollers 41, 42 of the strand drawing device 4. However, when the material forming the strands St is an elastomeric material having elasticity like rubber (hereinafter referred to as a soft material), the strands St do not slide well on the chute plate 101, and the strands St may stagnate on the chute plate 101, making it impossible to draw the strands St smoothly into the strand drawing device 4.

[0011] Furthermore, when starting operation of the pelletizer 31, an operator must set the tip end of the strand St sent from the strand cooling device in the pelletizer 31. At that time, the operator must insert the tip end of the strand St so that it is sandwiched between the first and second rollers 41, 42. However, if the strand St is a soft material, the strand St is twisted and the chute plate 101 gets in the way, and it is not easy for the operator to set the tip end of the strand St in the pelletizer 31 so that it is sandwiched between the first and second rollers 41, 42.

[0012] The present invention has been made to solve the above-mentioned problems, and has an object to provide a pelletizer that can smoothly draw in strands supplied from a strand cooling device in a preceding stage, even if the strands are made of a soft material, and that can easily set the tip portion of the strand at the start of operation. [Means for solving the problem]

[0013] In order to achieve the above object, a pelletizer according to one embodiment of the present invention has a first roller that rotates in a predetermined direction and a second roller arranged above and opposite the first roller, and is equipped with a strand drawing-in device that clamps and draws in a plurality of strands extruded from an extruder and transported while being cooled by a strand cooling device, between the first roller and the second roller, a cutting device that cuts the plurality of strands drawn in by the strand drawing-in device into granules, a drive roller conveyor having a plurality of drive rollers that are arranged side by side in the transport direction of the strands and driven to rotate, and that are installed between the strand cooling device and the strand drawing-in device so as to transport the strands transported by the strand cooling device toward between the first roller and the second roller, and a non-contact power transmission device that transmits rotational power from a motor to the plurality of drive rollers in a non-contact manner by magnetic force.

[0014] According to this configuration, a drive roller conveyor is provided between the strand cooling device and the strand drawing-in device, and the strand supplied from the strand cooling device is transported by the drive roller conveyor toward between the first roller and the second roller of the strand drawing-in device. Therefore, even if the strand is made of a soft material, the strand can be smoothly drawn in by the strand drawing-in device.

[0015] In addition, when an operator sets the tip portion of the strand at the start of operation, the tip portion of the strand and the portion adjacent to it are placed on the drive roller conveyor, and the strand is transported by the drive roller conveyor, and the tip portion of the strand is inserted between the first roller and the second roller of the strand retraction device. Therefore, even if the strand is made of a soft material, the tip portion of the strand can be easily set at the start of operation.

[0016] In addition, since the drive roller conveyor transmits the rotational power from the motor to the multiple drive rollers in a non-contact manner via a non-contact power transmission device, if an operator accidentally holds down a drive roller with his or her hand, for example when starting operation to set the end of the strand, the rotation of the drive roller being held down by the hand will stop, and the operator's hand will not be pulled in between the first and second rollers of the strand retraction device, ensuring the safety of the operator.

[0017] The non-contact power transmission device may include a plurality of first magnet gears fixed to the rotating shafts of each of the plurality of drive rollers and arranged in a linear array, a drive shaft arranged so that its axial direction is parallel to the arrangement direction of the plurality of first magnet gears and rotated by the motor, and a second magnet gear fixed to the drive shaft at a position close to but not in contact with the first magnet gear, and transmitting the rotational power of the drive shaft to the drive roller together with the first magnet gear.

[0018] The second magnet gear may be provided in a plurality of parts aligned in the axial direction on the drive shaft corresponding to the plurality of first magnet gears. Effect of the Invention

[0019] The present invention has the above-described configuration, and has the effect of providing a pelletizer that can smoothly draw in the strands supplied from the upstream strand cooling device, even if the strands are made of a soft material, and can easily set the tip portions of the strands at the start of operation. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram showing an example of a pellet production system equipped with the pelletizer of this embodiment. [Diagram 2] FIG. 2 is a side view showing an outline of the internal structure of the main part of the pelletizer of this embodiment. [Diagram 3] FIG. 3 is a plan view showing an outline of the main part of the pelletizer of this embodiment. [Figure 4] FIG. 4 is a side view showing an outline of the internal structure of a main part of a conventional pelletizer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following, the same or corresponding elements are denoted by the same reference numerals throughout the drawings, and duplicated descriptions thereof may be omitted. In addition, the drawings are schematic illustrations of the respective components for ease of understanding, and shapes, dimensional ratios, and the like may not be accurately depicted. In addition, the present invention is not limited to the following embodiments.

[0022] (Embodiment) 1 is a schematic diagram showing an example of a pellet production system equipped with a pelletizer of this embodiment. This pellet production system includes an extruder 1, a strand cooling device 2, and a pelletizer 3 of this embodiment. In the extruder 1, a resin material and an additive are mixed and melted, and the molten resin is shaped into a string-like resin (strand) having a circular cross section (for example, a diameter of 3 mm) and extruded from a multi-hole die 1a attached to the tip. The strand extruded from the extruder 1 is supplied to a strand cooling device 2 provided adjacent to the extruder 1 on the downstream side in the conveying direction of the strand.

[0023] The strand cooling device 2 includes, for example, a conveyor 21 consisting of a belt conveyor using a mesh belt, a water cooling device 22 arranged above the conveyor 21 and spraying cooling water onto the strands transported on the conveyor 21, and an air cooling device 23 spraying cooling air onto the strands transported on the conveyor 21. In the strand cooling device 2, on the upstream side of the strand transport direction, the water cooling device 12 sprays cooling water having a large heat capacity from above the transported strands to rapidly cool them, and on the downstream side of the strand transport direction, the air cooling device 23 sprays cooling air from above the strands to cool and dry them. The strands extruded from the extruder 1 in this way are cooled in the strand cooling device 2 so that the temperature gradually decreases from the upstream side to the downstream side of the transport direction. In the strand cooling device 2, near the upstream end of the strand transport direction, i.e., near the area where the molten resin is extruded as a strand from the multi-hole die 1a of the extruder 1, the temperature of the resin is high and the strands are hardly hardened. On the other hand, near the downstream end of the strand in the transport direction, i.e., near the point where the strand is sent from the strand cooling device 2 to the pelletizer 3, the strand is not completely hardened, but its surface is solidified.

[0024] The strands sent from the strand cooling device 2 to the pelletizer 3 are cut into a predetermined length (e.g., 3 mm) by the pelletizer 3 to generate granular (cylindrical) resin pellets. These resin pellets are discharged from the discharge port 3a of the pelletizer 3. These discharged resin pellets are supplied to, for example, a sorting device, where they are sorted into standard products and non-standard products.

[0025] Next, the pelletizer 3 of this embodiment will be described in detail. Fig. 2 is a side view showing an outline of the internal structure of the main part of the pelletizer 3. Fig. 3 is a plan view showing an outline of the main part of the pelletizer 3.

[0026] The pelletizer 3 includes a strand drawing-in device 4 that draws in a plurality of strands St and sends them out to a cutting device 5, a cutting device 5 that cuts (shears) the strands St sent out from the strand drawing-in device 4 to a predetermined length, and a drive roller conveyor 6. The strand drawing-in device 4 and the cutting device 5 are provided with safety covers 40, 50, respectively.

[0027] The strand drawing device 4 includes a first roller 41 that rotates around a horizontal fixed rotation axis 41a, and a second roller 42 that rotates around a movable rotation axis 42a that is vertically displaceable within a predetermined range. The second roller 42 is disposed above the first roller 41 in opposition to it, and rotates in the opposite direction to the first roller 41. The first roller 41 rotates by motor drive. The second roller 42 may be rotated by motor drive, or may be driven in response to the rotation of the first roller 41. The strand St is sandwiched between the first roller 41 and the second roller 42, and the strand St drawn in by the rotation of the first and second rollers 41 and 42 slides on the strand sliding table 43 and is sent to the cutting device 5. The second roller 42 is configured such that the movable rotation axis 42a is vertically displaceable as described above in order to draw in the strand St by sandwiching it between the first roller 41 and the second roller 42.

[0028] The cutting device 5 includes a rotary blade 51 and a fixed blade 52. The fixed blade 52 is fixed to the end of the strand sliding base 43 on the rotary blade 51 side. The rotary blade 51 is configured as a drum-type cutter that rotates about a rotation axis 51a parallel to the rotation axes 41a, 42a of the first and second rollers 41, 42, and has a plurality of blade edges 51b formed at regular intervals in the circumferential direction of the drum. The fixed blade 52 supports the strand St that is sent out by the rotation of the first roller 41 and the second roller 42, and the rotary blade 51 rotates at high speed to continuously cut the strand St to a predetermined length, and granular (cylindrical) resin pellets are continuously formed.

[0029] As shown in FIG. 2, the drive roller conveyor 6 is disposed between the strand cooling device 2 and the strand drawing device 4, and is installed so as to convey the strand St conveyed by the strand cooling device 2 toward the gap (gap) between the first roller 41 and the second roller 42. Here, the conveyor 21 of the strand cooling device 2 conveys the strand St on the conveyor belt 25 in the direction of arrow b by the rotation of the drive roller 24, and sends it to the drive roller conveyor 6. The strand St sent to the drive roller conveyor 6 is conveyed by the drive roller conveyor 6 in the direction of arrow a, and sent to the gap (gap) between the first roller 41 and the second roller 42 of the strand drawing device 4. In this example, a cross plate 26 is disposed at the end of the conveyor 21 so that the strand St can easily transfer from the conveyor 21 to the drive roller conveyor 6.

[0030] The drive roller conveyor 6 includes a plurality of metal drive rollers 61 (FIG. 3) arranged in parallel in the conveying direction (arrow a direction) of the strand St and driven to rotate, a motor 65, and a non-contact power transmission device that transmits the rotational power of the motor 65 to the plurality of drive rollers 61 in a non-contact manner by magnetic force. Between the adjacent drive rollers 61 shown in FIG. 3, there are gaps (not shown) so that the drive rollers 61 can rotate in the same direction. The diameter of the drive roller 61 is smaller than the diameter of the first roller 41, and the conveying direction of the strand St (arrow a direction) is perpendicular to the rotation axis direction of the first roller 41 in a plan view. By using the drive roller 61 whose diameter is smaller than the diameter of the first roller 41, the strand St can be conveyed smoothly.

[0031] The roller shafts (rotating shafts) of the multiple drive rollers 61 are rotatably supported by left and right frames 68, 69. The left and right frames 68, 69 are fixed by multiple connecting plates 70 (FIG. 2) arranged on their lower surfaces. The framework consisting of the left and right frames 68, 69 and the multiple connecting plates 70 is fixed to the base 30 or the like using appropriate members (not shown).

[0032] A short cylindrical first magnet gear 62 is fixed to the end of the roller shaft 61a (FIG. 3) of each drive roller 61 protruding outward from the frame 68. The first magnet gears 62 fixed to the roller shaft 61a, which is the rotation shaft of each of the drive rollers 61, are arranged in a straight line. A drive shaft 63 is arranged below the first magnet gears 62. In other words, the drive shaft 63 is arranged so that its axial direction is parallel to the arrangement direction of the first magnet gears 62. The drive shaft 63 is rotatably supported by a plurality of bearings 71. The bearings 71 are fixed to the outer side surface of the frame 68.

[0033] A plurality of short cylindrical second magnet gears 64 are fixed to the drive shaft 63 in a line in the axial direction of the drive shaft 63 in correspondence with the plurality of first magnet gears 62. The second magnet gears 64 are fixed to the drive shaft 63 at positions close to but not in contact with the first magnet gears 62. Note that in Fig. 3, the drive shaft 63 and the like are omitted from illustration in order to avoid complicating the drawing.

[0034] Each roller shaft 61a, which is the rotation axis of each first magnet gear 62, and the drive shaft 63, which is the rotation axis of the second magnet gears 64, are arranged so as to be perpendicular to each other in a plan view. The first magnet gear 62 and the second magnet gear 64 are arranged in close proximity to each other in a non-contact state. The first and second magnet gears 62 and 64 are made of a neodymium magnet or the like having a large magnetic force, for example, a magnetic flux density of 1 Tesla. The first magnet gear 62 and the second magnet gear 64 have magnetic poles formed in a spiral shape on a cylindrical surface along the axial direction of each rotation axis, and have a power transmission function similar to that of a miter gear or the like. In other words, the second magnet gears 64 can transmit the rotational power of the drive shaft 63 to the drive roller 61 together with the first magnet gears 62 in a non-contact state.

[0035] A motor 65 for rotating a drive shaft 63 is fixed on the base 30. A belt 67 is hung between the drive shaft 63 and a pulley 66 attached to the shaft of the motor 65, and the drive shaft 63 is rotated by the rotation of the motor 65.

[0036] In this drive roller conveyor 6, a non-contact power transmission device that transmits the rotational power of the motor 65 to the multiple drive rollers 61 is composed of multiple first magnet gears 62, a drive shaft 63, and multiple second magnet gears 64. This drive roller conveyor 6 is configured such that, by rotating the motor 65 in a predetermined direction, the drive shaft 63 rotates in a predetermined direction, and the drive roller 61 rotates via the second magnet gear 64 and the first magnet gear 62 so that the conveying direction is the direction of the arrow a. Here, the peripheral speed of the surface of the drive roller 61 is configured to be equal to the peripheral speed of the surface of the first roller 41. In other words, the conveying speed of the strand St by the drive roller conveyor 6 is configured to be equal to the speed at which the strand St is drawn in by the strand drawing device 4. At the start of operation, after an operator inserts the tip portion of the strand St so that it is sandwiched between the first and second rollers 41, 42 and sets the tip portion of the strand St in the strand drawing device 4, the actual transport speed of the strand St is governed by the speed at which the strand St is drawn in by the strand drawing device 4, so the transport speed of the strand St by the drive roller conveyor 6 may be slower than the speed at which the strand St is drawn in by the strand drawing device 4. In this case, the strand St is drawn into the strand drawing device 4 while slipping on the surface of the drive roller 61 of the drive roller conveyor 6.

[0037] In this embodiment, a drive roller conveyor 6 is installed between the strand cooling device 2 and the strand drawing-in device 4, and the strand St supplied from the strand cooling device 2 is transported by the drive roller conveyor 6 toward the gap (gap) between the first roller 41 and the second roller 42 of the strand drawing-in device 4, so that even if the strand St is made of a soft material (an elastomer-based material having elasticity like rubber), the strand St can be smoothly drawn in by the strand drawing-in device 4. It goes without saying that this effect can be obtained even if the strand St is made of a material that hardens normally rather than a soft material.

[0038] Furthermore, when an operator sets the tip portion of the strand St at the start of operation, the tip portion of the strand St and the portion adjacent thereto are placed on the driving roller conveyor 6, and the driving roller conveyor 6 transports the strand St, and the tip portion of the strand St is inserted between the first roller 41 and the second roller 42 of the strand drawing device 4. Therefore, even if the strand St is made of a soft material, the tip portion of the strand St can be easily set at the start of operation. It goes without saying that this effect can be obtained even if the strand St is made of a material that hardens normally rather than a soft material.

[0039] Moreover, the driving roller conveyor 6 is low-noise because the rotational power is transmitted without contact between the first magnet gear 62 and the second magnet gear 64. If an operator mistakenly holds down the driving roller 61 with his / her hand, for example, when starting operation to set the tip portion of the strand St, the first magnet gear 62, which is in a non-contact state, slips against the rotating second magnet gear 64 and stops rotating, and the rotation of the driving roller 61 held down by the hand stops. This prevents the operator's hand from being pulled in between the first roller 41 and the second roller 42 of the strand drawing device 4, ensuring the safety of the operator.

[0040] In this embodiment, as shown by the two-dot chain line in FIG. 2, a roller unit 8 may be arranged above the downstream side in the conveying direction of the drive roller conveyor 6, in which a plurality of rollers 81 are rotatably supported by frames 82 on both sides. Here, each of the plurality of rollers 81 is arranged in a line in the conveying direction of the strand St, facing each of the drive rollers 61. The roller unit 8 is arranged so as to be displaceable in the vertical direction. By providing such a roller unit 8, the strand St conveyed on the drive roller conveyor 6 is conveyed in a state of being sandwiched between the drive roller 61 and the roller 81 in the arrangement area of ​​the roller unit 8 and in contact with the roller 81, and the roller 81 rotates according to the movement of the strand St in contact with it. In this case, when setting the tip portion of the strand St at the start of operation, if the tip portion of the strand St is placed in front of the roller unit 8, the strand St is easily sandwiched between the drive roller 61 and the roller 81 and conveyed, and even if the strand St is made of a soft material, the strand St can be smoothly drawn in by the strand drawing device 4. It goes without saying that this effect can be obtained even if the strands St are made of a material that normally hardens rather than a soft material.

[0041] In this embodiment, a plurality of second magnet gears 64 are provided corresponding to each of the plurality of first magnet gears 62, but a configuration in which one long cylindrical second magnet gear is provided for each of the plurality of first magnet gears 62 may also be used.

[0042] In addition, in this embodiment, the strand cooling device 2 shown in FIG. 1 has been exemplified as the strand cooling device. However, instead of this, a configuration may be used which has a water tank that holds a cooling liquid for cooling the strands, and in which a plurality of guide rollers are provided in the water tank for guiding the strands in the cooling liquid.

[0043] From the above description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed as merely illustrative and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention. [Industrial Applicability]

[0044] The present invention is useful as a pelletizer or the like that can smoothly draw in a strand supplied from a strand cooling device in a preceding stage, even if the strand is made of a soft material, and can easily set the tip portion of the strand at the start of operation. [Explanation of symbols]

[0045] 1. Extruder 2 Strand Cooling Unit 3 Pelletizer 4 Strand retraction device 41 First Roller 42 Second Roller 5 Cutting device 6 Drive roller conveyor 61 Drive roller 62 First Magnet Gear 63 Drive shaft 64 Second Magnet Gear 65 Motor

Claims

1. a strand drawing device having a first roller that rotates in a predetermined direction and a second roller disposed above the first roller in an opposing manner, the strand drawing device clamping and drawing in a plurality of strands that are extruded from an extruder and conveyed while being cooled by a strand cooling device between the first roller and the second roller; a cutting device that cuts the plurality of strands drawn in by the strand drawing device into granular pieces; a drive roller conveyor including: a plurality of drive rollers arranged side by side in a conveying direction of the strand and driven to rotate, the drive roller conveyor being installed between the strand cooling device and the strand drawing device so as to convey the strand conveyed by the strand cooling device toward a space between the first roller and the second roller; and a non-contact power transmission device which transmits rotational power of a motor to the plurality of drive rollers in a non-contact manner by magnetic force; A pelletizer equipped with

2. The non-contact power transmission device includes: A plurality of first magnet gears fixed to the rotation shafts of the plurality of drive rollers and arranged in a straight line; a drive shaft that is arranged so that its axial direction is parallel to the arrangement direction of the plurality of first magnet gears and is rotated by the motor; a second magnet gear that is fixed to the drive shaft at a position close to but not in contact with the first magnet gear and transmits the rotational power of the drive shaft to the drive roller together with the first magnet gear; 2. The pelletizer of claim 1.

3. The second magnet gear is provided in a plurality of parts on the drive shaft so as to correspond to the plurality of first magnet gears, and is arranged in the axial direction of the drive shaft.

3. The pelletizer of claim 2.

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