JP2000210895A - Rotary blade for pelletizer and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary blade for pelletizer in which a long size edge member made of a cement carbide is fixed by the soldering to the installing step of a rotary blade base which consists of a stainless steel, an alloy tool steel or the like, and the residual stress generated at the inside by the difference of the thermal expansion coefficient of the material is made as small as possible. SOLUTION: This rotary blade is manufactured through a first process to finish the inner diameter (d) of a hollow cylindrical outer tube 5 in 0.2 to 0.7% smaller than the diameter D of the tube fitting part 9 of a rotary shaft 3, a second process to solder a long size blade member made of a cement carbide, to an installing step 7 provided to the hollow cylindrical outer tube 5, a third process to even heat process the hollow cylindrical outer tube 5 finishing the soldering, a fourth process to cool to the normal temperature after the hollow cylindrical outer tube 5 is fitted playable to the tube fitting part 9 of the rotary shaft 3, and a fifth process to finish the blade outer periphery of the rotary blade 2 in the cylinder form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary blade for a pelletizer incorporated in a cutting portion of a pelletizer used for cutting and granulating a thermoplastic resin which has been melted and extruded from a nozzle to form a strip. And a method of manufacturing the same.

[0002]

2. Description of the Related Art A cutting device for granulating a thermoplastic resin (generally called a strand) which has been melted and extruded from a nozzle into a string shape, that is, a cutting portion of a so-called pelletizer is generally shown in FIG. Fixed rectangular blade 1
And a rotary blade 2 provided at the center of a rotary shaft 3 provided in parallel with the fixed blade 1 and having a cross section shaped like a ratchet wheel. The rotating blade 2 that rotates the strand 15 guided to the upper surface of the fixed blade 1 by the take-up roll 14 and the like at a predetermined speed with the cutting edge of the fixed blade 1
The cutting edge is used to cut into granules.

As shown in FIGS. 4 and 5, the rotary blade 2 for a pelletizer is provided at the center of a rotary shaft 3.
Its cross section is shaped like a ratchet. As shown in FIG. 4, the rotary blade 2 includes a plurality of angled bases 6 extending in a spiral shape in the axial direction at equal intervals in the circumferential direction on a cylindrical outer peripheral surface, and A long blade member 8 brazed and fixed to a spiral mounting step 7 for mounting the long blade member provided on each of the threads of the angled base 6 of the rotary blade base 4. ing.

As another configuration of the rotary blade for a pelletizer, as shown in FIG.
Is constituted by a cylindrical fitting portion 9 formed at the center of the rotary shaft 3 and a hollow cylindrical outer cylinder 5 fitted to the cylindrical fitting portion 9 in a loose fit state. In this configuration, the movement of the hollow cylindrical outer cylinder 5 in the axial direction is restricted by the flange 10 and the holding nut 11 provided on the rotating shaft 3, and the cylinder fitting portion of the hollow cylindrical outer cylinder 5. 9
Is stopped by a detent means such as a key, and the cylinder fitting portion 9 of the rotating shaft 3 and the hollow cylindrical outer cylinder 5 are integrally fixed.

[0005]

However, in the above-mentioned rotary blade for a pelletizer, the rotary blade base and the hollow cylindrical outer cylinder are formed of stainless steel or alloy tool steel, and the rotary blade base and the hollow cylindrical outer cylinder are formed. The cemented carbide is used for the long blade member brazed and fixed to the spiral mounting step provided at the tip of the plurality of mountain bases provided on the outer peripheral surface of the blade. As a result, when the long blade member made of cemented carbide is brazed to the mounting step at a predetermined temperature and then the rotary blade is cooled to room temperature, the rotary blade base or the hollow cylindrical outer cylinder and the long blade A large residual stress is generated between the member and the member due to the difference in the coefficient of thermal expansion between the two.

In particular, in the case of a rotary blade base or a rotary blade having a hollow cylindrical outer cylinder having a length of more than 200 mm, peeling of a brazing layer or super-hardness occurs due to a difference in shrinkage between the two during cooling after brazing. There has been a problem that the long blade member made of alloy is broken. Thus, in order to avoid the disadvantage after brazing caused by the difference in the coefficient of thermal expansion of the material, up to now a rotary blade base having a length exceeding 200 mm, or a rotary blade having a hollow cylindrical outer cylinder has a length of 200 mm or less. Long blade members made of cemented carbide were connected in the longitudinal direction and brazed.

[0007] However, in this conventional technique, the brazing material is filled in the joint of the long blade member made of cemented carbide,
Alternatively, some voids were formed. And, the joint in such a state has the same effect as the presence of a chipped portion in a part of the long blade member, inducing a cutting defect, causing a reduction in the quality of the pellet, and sometimes, There was also a problem that a chip was generated at the joint corner.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art. For example, a long blade made of cemented carbide is fixed to a mounting step by brazing. Even with a rotary blade for a pelletizer made of alloy tool steel, etc., the residual stress generated inside due to the difference in the coefficient of thermal expansion is small. In particular, even with a rotary blade having a length exceeding 200 mm, A rotary blade for a pelletizer, which does not cause any problem even if the long blade member having the same length as the rotary blade is brazed and fixed to the mounting step portion without joining the long blade members in the length direction, and the same. It is intended to provide a manufacturing method.

[0009]

To achieve the above object, the present invention is as follows.

A first invention to be patented is a rectangular parallelepiped fixed blade and a rotary blade having a cross section provided at the center of a rotary shaft provided in parallel with the fixed blade. A plurality of angled bases extending spirally in the axial direction on the outer peripheral surface of the rotary blade base are formed at equal intervals in the circumferential direction. A rotary blade to which a long blade member made of brazing is fixed by brazing, wherein the rotary blade base is used for a cutting portion of a pelletizer for finely cutting and granulating a thin strip thermoplastic resin. A cylinder fitting portion formed at the center of the rotating shaft, and a hollow cylindrical outer cylinder in which a plurality of chevron bases extending spirally in the axial direction on the outer peripheral surface are formed at equal intervals in the circumferential direction, The hollow cylindrical outer cylinder is burned into the cylinder fitting portion of the rotating shaft. A rotary blade pelletizer are integrated immovably by fitting.

According to the rotary blade for a pelletizer of the present invention,
The rotary blade base of the rotary blade for the pelletizer has a cylindrical fitting portion formed at the center of the rotary shaft, and a plurality of chevron bases extending spirally in the axial direction on the outer peripheral surface are formed at equal intervals in the circumferential direction. Since the hollow cylindrical outer cylinder is integrated by shrink-fitting into a cylindrical fitting portion formed at the center of the rotating shaft, the hollow cylindrical outer cylinder at room temperature is formed. After the long blade member is brazed and fixed at a predetermined temperature to the threaded portion of the angled base of the hollow cylindrical outer cylinder, the hollow cylindrical outer cylinder is evenly cooled at a predetermined temperature equal to or lower than the brazing temperature. If the inner peripheral side of the hollow cylindrical outer cylinder is finished to the size that starts shrink-fitting to the cylinder fitting part at the early stage of the temperature drop by cooling after the heat treatment, the cooling of the hollow cylindrical outer cylinder Contraction of the inner diameter of the hollow cylindrical outer cylinder due to It is prevented me. As a result, since the rotary blade for a pelletizer of the present invention has a near-dimensional change in the dimensional change after cooling between the hollow cylindrical outer cylinder and the long blade member made of materials having significantly different coefficients of thermal expansion, brazing due to residual stress is performed. It does not cause peeling of the portion or breakage of the cemented carbide long blade member.

[0012] A second invention for which a patent is sought is that the cylindrical fitting portion of the rotary shaft having a cylindrical fitting portion having a predetermined diameter in the center portion, and a hollow circle fitted externally to the cylindrical fitting portion. A column-shaped outer cylinder, in which a plurality of chevron bases extending spirally in the axial direction are formed on the outer periphery at equal intervals in the circumferential direction, and a spiral attachment for attaching a long blade member to the thread of the chevron base. A rotary blade is constituted by a hollow cylindrical outer cylinder provided with a step, and a plurality of cemented carbide long blade members brazed and fixed to the spiral mounting step of the hollow cylindrical outer cylinder. In the method for manufacturing a rotary blade for a pelletizer, the inner diameter of the hollow cylindrical outer cylinder, after brazing and fixing the long blade member made of cemented carbide to the spiral mounting step of the hollow cylindrical outer cylinder, Soaking the entire hollow cylindrical outer cylinder at a predetermined temperature below the brazing temperature A first step of finishing at a predetermined temperature during cooling after the shrink fitting into the cylinder fitting portion of the rotary shaft so as to start integration, and a spiral mounting step provided on the hollow cylindrical outer cylinder. A second step of brazing the long blade member made of cemented carbide to the portion, and a third step of soaking the hollow cylindrical outer cylinder completed in the second step at a predetermined temperature equal to or lower than the brazing temperature. A fourth step of loosely fitting the hollow cylindrical outer cylinder, which has been soaked in the third step, to the cylinder fitting portion of the rotary shaft and then cooling the same to room temperature; and a hollow circle cooled in the fourth step. A fifth step of finishing the end of the long blade member made of cemented carbide brazed to the columnar outer cylinder into a cylindrical shape concentrically with the rotation axis.

According to the manufacturing method of the present invention, a spiral-shaped mounting step provided in a spiral thread on a mountain-shaped base formed at equal intervals in the circumferential direction on the outer peripheral surface of the hollow cylindrical outer cylinder is made of cemented carbide. After brazing and fixing the long blade member, the entire hollow cylindrical outer cylinder is soaked at a predetermined temperature equal to or lower than the brazing temperature, and the inside of the hollow cylindrical outer cylinder is early in the temperature lowering process by subsequent cooling. The inner diameter of the hollow cylindrical outer cylinder is finished so as to start the shrink-fitting integration with the cylinder fitting portion having a predetermined diameter provided at the center of the rotating shaft, so that the hollow circle is formed. The columnar outer cylinder is prevented from contracting in the radial direction by the tube fitting portion.

As the cooling proceeds further, the restraint by the tube fitting portion becomes stronger, and the frictional resistance in the length direction is added to the hollow cylindrical outer tube. As a result, the contraction in the length direction does not progress, so that the thermal expansion is prevented. The dimensional change due to the contraction between the hollow cylindrical outer cylinder and the long blade member, which are formed of materials having greatly different rates, can be made close to each other. As a result, even if one long blade member of the same length is brazed to a rotary blade having a length of the rotary blade base exceeding 200 mm, brazing due to residual stress generated due to a difference in both shrinkage amounts. Accidents such as peeling of the attachment portion and breaking of the long blade member made of cemented carbide do not occur.

A third invention for which a patent is sought is that the material of the hollow cylindrical outer cylinder in the method for manufacturing a rotary blade for a pelletizer of the second invention for which a patent is claimed is SUS30.
4, the inner diameter of the hollow cylindrical outer cylinder at room temperature is smaller by 0.2 to 0.7% than the shaft diameter of the cylindrical fitting portion of the rotary shaft on which the hollow cylindrical outer cylinder is externally fitted. The inner diameter is finished and the shrink-fitting of the hollow cylindrical outer cylinder into the cylinder fitting portion is started at a temperature of 150 ° C. or more.

In the third invention, the material of the hollow cylindrical outer cylinder in the second invention is specified to be SUS304 which is resistant to rust, and the shrink-fitting of the hollow cylindrical outer cylinder by shrink fitting to the cylindrical fitting portion is 0.2 to 0.2. It is specified in the range of 0.7%, and the shrink-fitting integration of the hollow cylindrical outer cylinder into the cylinder fitting part starts from the soaking temperature after brazing to 150 ° C by cooling. In this case, the method for manufacturing the rotary blade for a pelletizer according to the second aspect of the invention is more specifically described.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1A shows the rotary shaft 3, and FIGS. 1B and 1C show the hollow cylindrical outer cylinder 5, and FIG. Indicates a side surface, and indicates a state before fitting. Also,
FIG. 2 shows a rotary blade for a pelletizer of the present invention,
(D) is a front view, and (e) is a side view. In FIG. 1, a cylinder fitting portion 9 having an outer diameter D and a length k is provided at the center of the rotating shaft 3. A flange 10 serving as a stopper is provided at one end of the tube fitting portion 9 so that the fitting position of the hollow cylindrical outer tube 5 can be accurately determined. Reference numeral 12 denotes a bearing fitting portion for rotating the shaft, and reference numeral 13 denotes a drive shaft, in which a pulley and the like are incorporated.

The length h of the hollow cylindrical outer cylinder 5 is also substantially the same as the length K of the cylinder fitting portion 9, and the outer peripheral surface thereof has a plurality of mountain bases 6 extending spirally in the axial direction. Are formed at equal intervals in the circumferential direction, and a spiral mounting step 7 for mounting and fixing the long blade member by brazing is provided on the thread of the angled base 6. The inner diameter d of the hollow cylindrical outer cylinder 5 is 0.2 to 0.7% smaller than the outer diameter D of the cylindrical fitting portion 9 of the rotating shaft 3 at room temperature, that is, d = 0.998D. Finished to 0.993D.

Next, the spiral-shaped mounting steps 7 provided on the threads of the mountain-shaped base 6 provided on the outer periphery of the hollow cylindrical outer cylinder 5 formed as described above are formed by using a silver solder or the like. The long blade member 8 made of cemented carbide is brazed and fixed. After all the long blade members 8 have been fixed to the respective mounting steps 7 by brazing, the hollow cylindrical outer cylinder 5 is heated to 150 ° C.
Before the temperature is lowered, the entire hollow cylindrical outer cylinder 5 is soaked at a predetermined temperature lower than the brazing temperature, for example, about 450 ° C., and the inner diameter is expanded by a predetermined amount by thermal expansion.
Here, the cooling temperature of the hollow cylindrical outer cylinder 5 after brazing is set to 1
The reason why the temperature is not lowered to 50 ° C. or lower is that if the temperature is lowered to 150 ° C. or lower, the same problem as that of the above-described conventional technique occurs.

Next, the room temperature is temporarily set to 20 ° C., and the material of the hollow cylindrical outer cylinder 5 is SUS304 (coefficient of thermal expansion: 0.00001).
7 / ° C), 450 ° C by soaking
The inner diameter d2 of the hollow cylindrical outer cylinder 5 becomes d2 = (0.0
00017 × 430 × d) + d = 1.0731d. On the other hand, the outer diameter D of the cylinder fitting portion 9 is d = 0.998D to 0.
Since D is 993D, D = 1.002d to 1.007
d. As a result, the hollow cylindrical outer cylinder 5 that has been soaked at 450 ° C. is freely fitted to the cylinder fitting portion 9 in a loose fit state. After the soaked hollow cylindrical outer cylinder 5 is loosely fitted to a predetermined position of the cylinder fitting portion 9, the hollow cylindrical outer cylinder 5
Is naturally cooled, the inner diameter of the hollow cylindrical outer cylinder 5 is the same as the shaft diameter D of the cylinder fitting portion 9, that is, from 1.002d to 1.00.
The diameter is reduced to 7d, but after that, the diameter cannot be reduced because it is hindered by the tube fitting portion 9. As the cooling further proceeds, the longitudinal contraction of the hollow cylindrical outer cylinder 5 is prevented by frictional resistance.

[0021]

In the embodiment, SUS304 is used for the rotating shaft and the hollow cylindrical outer cylinder, and the respective dimensions are the outer diameter of the rotating blade: C = 150 mm The length of the rotating shaft: L = 600 mm Cylinder fitting portion Length: k = 300 mm Shaft diameter of tube fitting portion: D = 110 mm Length of hollow cylindrical outer tube: h = 300 mm Inner diameter of hollow cylindrical outer tube: d = 109.6 mm, that is, tube fitting The hollow cylindrical outer cylinder was set so that the shrinkage of the outer cylinder with respect to the joint was 0.36%. A spiral blade made of a cemented carbide having a length of about 300 mm and a length of about 300 mm was brazed at about 700 ° C. with a silver braze (BAg) to the mounting step of the screw thread at each base of the hollow cylindrical outer cylinder. . Thereafter, the hollow cylindrical outer cylinder is soaked for about 1 hour in an electric furnace maintained at about 450 ° C., and then the hollow cylindrical outer cylinder is loosely fitted to the cylindrical fitting portion of the rotating shaft. It was cooled to room temperature by natural cooling. As a result, the long blade member is connected to the rotary blade for the pelletizer of the length of the present embodiment, which is impossible to perform with a single long blade member in the prior art because the brazing layer is peeled off in the prior art. It could be completed without any problems.

[0022]

As described above, according to the present invention,
Even with a rotary blade for a pelletizer made of stainless steel or alloy tool steel, in which a long blade member made of cemented carbide is fixed by brazing, residual stress generated inside due to differences in the coefficient of thermal expansion of the material Is small, so even if it is a rotary blade for a pelletizer having a length exceeding 200 mm, one long blade member made of cemented carbide is not joined in the length direction. Can be used, and it is possible to eliminate the seam at the cutting edge of the rotary blade for the pelletizer, so that the cutting defect that was conventionally induced by the seam does not occur and the quality of the cut pellet is avoided. It was started. In addition, the problem of chipping that sometimes occurred at the joint corner has been eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram showing components of a rotary blade for a pelletizer according to an embodiment of the present invention.

FIG. 2 is a diagram showing a rotary blade for a pelletizer according to an embodiment of the present invention.

FIG. 3 is a schematic explanatory view showing a cut portion of a general pelletizer, wherein (f) is a front view and (g) is a plan view.

FIG. 4 is a view showing an example of a conventional rotary blade for a pelletizer, wherein (h) is a front view, and (l) is a cross-sectional view along AA.

FIG. 5 is a view showing another example of a conventional rotary blade for a pelletizer, in which (nu) is a front view showing a part in section and (lu) is a side view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed blade 2 Rotating blade 3 Rotating shaft 4 Rotating blade base 5 Hollow cylindrical outer cylinder 6 Angle base 7 Mounting step 8 Long blade member 9 Cylinder fitting part 10 Flange 11 Holding nut 12 Bearing fitting part 13 Drive shaft 14 Take-off roll 15 Strand

Continued on the front page (72) Inventor Tsutomu Sakai 2-4-1 Miyauchi, Tagajo City, Miyagi Prefecture Toyo Knives Co., Ltd. Tagajo Plant (72) Inventor Toshiro Kano 2-4-1 Miyauchi Tagajo City, Miyagi Prefecture Toyo Cutlery Stock F term in the Tagajo factory of the company (reference) 4D065 CA16 CB01 DD05 DD18 EB14 EC03 EC09

Claims (3)

[Claims] A fixed blade having a rectangular parallelepiped shape, and a rotary blade having a pawl-shaped cross section provided at a central portion of a rotary shaft provided in parallel with the fixed blade, the rotary blade having an axial center direction on an outer peripheral surface thereof. A long blade member made of a cemented carbide that extends spirally in the axial direction is brazed to the tip of the mountain-shaped base of the rotary blade base in which a plurality of mountain-shaped bases extending in a spiral shape are formed at equal intervals in the circumferential direction. A rotary blade for a pelletizer used in a cutting portion of a pelletizer that finely cuts and granulates a strip of thermoplastic resin with a fixed rotary blade, wherein the rotary blade base is formed at a central portion of the rotary shaft. A hollow cylindrical outer cylinder in which a plurality of chevron bases extending spirally in the axial direction on the outer peripheral surface are formed at equal intervals in the circumferential direction, and the hollow cylindrical outer cylinder is configured to rotate the hollow cylindrical outer cylinder; It is immovably integrated by shrink fitting to the cylinder fitting part of the shaft. A rotary blade for a pelletizer. 2. A rotary shaft having a cylindrical fitting portion having a predetermined diameter at a central portion thereof, and a hollow cylindrical outer cylinder externally fitted to the cylindrical fitting portion; A plurality of chevron bases extending spirally in the axial direction are formed at equal intervals in the circumferential direction,
A hollow cylindrical outer cylinder in which a spiral mounting step for mounting a long blade member is provided on the thread of the mountain base, and brazing fixed to the spiral mounting step of the hollow cylindrical outer cylinder In the method for manufacturing a rotary blade for a pelletizer, in which a rotary blade is formed by a plurality of cemented carbide long blade members, the inner diameter of the hollow cylindrical outer cylinder is reduced by using the cemented carbide long blade member. After brazing and fixing to the spiral mounting step of the hollow cylindrical outer cylinder, the rotating shaft is cooled at a predetermined temperature during cooling after the entire hollow cylindrical outer cylinder is soaked at a predetermined temperature equal to or lower than the brazing temperature. A first step of finishing to an inner diameter dimension in which shrink-fitting and integration are started at the cylindrical fitting portion, and a long blade member made of a cemented carbide at a spiral mounting step provided on the hollow cylindrical outer cylinder. A second step of brazing A third step of soaking the hollow cylindrical outer cylinder that has been brazed at a predetermined temperature equal to or lower than the brazing temperature; and a third step of soaking the hollow shaft in the cylinder fitting portion of the rotary shaft in the third step. A fourth step of loosely fitting the columnar outer cylinder and then cooling to room temperature, and rotating the tip of a cemented carbide long blade member brazed to the hollow cylindrical outer cylinder cooled in the fourth step. 5. A method for producing a rotary blade for a pelletizer, comprising: a fifth step of finishing cylindrically with a shaft and a concentric circle. 3. The material of the hollow cylindrical outer cylinder is SUS304, and the inner diameter of the hollow cylindrical outer cylinder is smaller than the outer diameter of the cylindrical fitting portion of the rotary shaft on which the hollow cylindrical outer cylinder is externally fitted. 0.2 to 0.7
The method for producing a rotary blade for a pelletizer according to claim 2, wherein the rotary blade is finished to a small diameter.