JP2878142B2 - Synthetic resin wheel, molding method therefor, and die apparatus therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a synthetic resin wheel,
The present invention relates to a molding method and a mold device used for the method.

[0002]

2. Description of the Related Art Wheels made of synthetic resin, for example, caster wheels are made of polypropylene, ABS resin or the like, and are formed by injection molding. FIG. 4 shows the flow of synthetic resin flow when wheels are molded by a conventional injection molding method. The interior of the cavity 6 is divided into right and left from a gate 1 provided in a central axle mounting hole. The traveling synthetic resin flow (indicated by the arrow) finally merges at a portion opposite to the gate 1, and as a result, a substantially straight weld line 2 is formed in the radial direction and the thickness direction of the wheel 3 (FIG. 5) is obtained. In the figure, reference numeral 4 denotes a runner portion, and 5 denotes a gate portion. However, when a wheel is formed by the injection molding method, a linear weld line indicating the confluence of the injected synthetic resin flow is formed at a position farthest from the gate serving as the injection port of the synthetic resin. It is known that the mechanical strength of the weld line formed at the location where the weld line is formed is weaker than that of the other parts due to insufficient fusion of the resin. There was a problem that damage occurred from the point. The above-mentioned drawbacks are not limited to wheels of casters, and similarly cause problems in wheels made of synthetic resin for various uses.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a synthetic resin wheel capable of eliminating deterioration in mechanical strength of a weld line portion, a molding method thereof, and It is an object of the present invention to provide a mold apparatus.

[0004]

According to the present invention, in order to solve the above-mentioned problems, in a wheel made of synthetic resin, a synthetic resin is inserted through a gate into a cavity corresponding to the shape of the wheel formed in a pair of dies. In a synthetic resin wheel molded by the injection molding method of injecting, the turbulence is generated at the injected confluence, and the weld line is formed in a complicated shape, taking the technical means that I have. Also,
In the method of molding wheels of a caster, in the method of injection molding a wheel, a synthetic resin is injected through a gate into a cavity corresponding to a shape of a synthetic resin wheel formed in a pair of dies. Injection molding is started with a resin flow obstruction rod that can advance and retreat into the cavity from the cavity inner wall portion on the opposite side, and the leading ends of the injected left and right synthetic resin flows contact the resin flow obstruction rod. This causes a turbulent flow at the junction of the left and right synthetic resin flows,
Technical measures are taken such that the resin flow obstruction rod is gradually retracted out of the cavity by the filling pressure of the synthetic resin flow to complete the injection of the synthetic resin flow. Further, in the wheel molding die apparatus made of a synthetic resin, the wheel molding die apparatus includes a pair of dies for injection molding the wheel, and at least one of the dies has an inner wall portion opposite to the gate arrangement position. Along with opening a passage communicating with the inside of the cavity, a resin flow obstruction rod is slidably disposed in the passage, and a tip portion of the resin flow obstruction rod is led out into the cavity in a free state,
Technical measures are taken such that the resin flow obstruction rod can be almost completely retracted into the passage by the pressure inside the cavity. The resin flow obstruction rod is urged via an elastic body, and at the beginning of the molding process, the tip end of the resin flow obstruction rod is led out into the cavity by the urging force of the elastic body and flows into the cavity. The pressure of the synthetic resin flow may cause the resin flow obstruction rod to retract from the inside of the cavity against the urging force of the elastic body.

[0005]

In the injection molding of a wheel, if a turbulent flow is generated in the injected confluence to form a weld line in a complicated shape, the mechanical strength of the weld line can be improved. Also, as a molding method, when the synthetic resin flow introduced from the gate into the cavity during the injection molding approaches the weld line forming portion, the synthetic resin flow is prevented from moving forward by the resin flow obstructing rod, and as a result, the synthetic resin flow is formed at this portion. Turbulence occurs in the resin flow, and the state is blurred, for example, the weld line becomes zigzag, so that the weld line substantially disappears, and as a result, the shape of the weld line portion can be complicated.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A synthetic resin wheel, a method of molding the same, and a molding apparatus used in the method of the present invention will be described below with reference to the drawings when applied to a caster wheel. FIG. 1 is a cross-sectional view showing a main part of a molding die for a wheel of a caster. This molding die has a pair of dies 1 having internal shapes substantially symmetric to each other.
1a and 11b, which form a cavity 12 corresponding to the shape of the wheels of the caster (for example as shown in FIG. 5). This pair of molds 11a, 11b
The cavity 1 is formed in at least one of the molds, for example, the mold inner wall of the mold 11a on the side opposite to the gate 13 arrangement position.
A plurality of passages 14 communicating with the inside 2 are provided along the radial direction of the mold 11a (for example, in a zigzag pattern as shown in FIG. 2). A resin flow obstruction rod 15 having a circular cross section is slidably disposed in the passage 14 in the longitudinal direction. An elastic body 16 is in contact with and arranged on the base end portion 15a of the resin flow obstruction rod 15, and the resin flow obstruction rod 15
Is constantly urged to be led out into the cavity 12. The pressing force of the elastic body 16 against the resin flow obstruction rod 15 is caused by the pressing force in the direction of the elastic body 16 due to the filling of the synthetic resin flow injected into the cavity 12. Must be weak enough to be easily pushed back (retracted) out of the cavity 12.

The shape, number, and arrangement of the resin flow obstructing rods 15 are not particularly limited, as long as a zigzag shape can be formed on the weld line due to the disturbance of the synthetic resin flow at the weld line forming site. Good. In the figure, reference numeral 17 denotes a runner serving as a synthetic resin flow passage.

Next, the operation of the molding die having such a configuration will be described. First, the molds 11a and 11b heated to an appropriate temperature are closed and adhered to each other. At this time, the resin flow obstruction rod 1 provided on the mold 11a is
In 5, the tip 15 b is led into the cavity 12 by the urging force of the elastic body 16. Next, as shown in FIG. 2, a predetermined resin is injected into the cavity 12 through a mold runner 17 and a gate 13 through an injection molding machine. The synthetic resin flow injected into the cavity 12 is split right and left from the gate 13 and spreads into the cavity 12 as indicated by the arrow in the figure, and the left and right synthetic resin flows at the opposite cavity portion farthest from the position of the gate 13. Although the flows merge, the resin flow obstruction rod 15 is present immediately before the flow, so that it is not possible to form a straight weld line in the radial direction by merging straightly as in the related art. The synthetic resin flow is disturbed by, for example, bypassing around the resin flow obstruction rod 15, and the weld line 18 is formed in this disturbed state (for example, in a zigzag shape as shown). That is, the weld line 18 is formed in a blurred state. The caster wheels thus formed are pushed out of the mold after a certain cooling time.

In the above embodiment, the resin flow obstructing rod 1
5 is provided in only one mold 11a, but the resin flow obstruction rod 15 having the same configuration is connected to the other mold 11a.
b may be similarly provided at the corresponding site.

FIG. 3 shows another embodiment in which a gate 13 'is provided outside the wheel 3. Also in this case, Gate 1
The resin flow merges at a position opposite to 3 ', but the weld line 18 can be disturbed by the resin flow obstructing rod 15. The other configuration is the same as that of the above embodiment, and the description is omitted.

In this way, the weld line 18 is formed not on the surface but on the wheels of the caster in a disturbed state. This wheel is preferable because it has a higher strength because the weld line is not more complicated than in the past and is not formed in a planar shape. The present invention is not limited to the above-described embodiment as long as the weld line is not formed in a planar shape and the resin is further fused.

[0012]

As described above in detail, according to the method for molding a synthetic resin wheel and the molding die according to the present invention,
The fusion of the resin is enhanced by the turbulence of the synthetic resin flow, and the weld line can be blurred. Further, in such a synthetic resin wheel in which the weld line is disturbed, the mechanical strength of the weld line portion can be improved, and the conventional weakness of the weld line can be eliminated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a molding die used in the method of the present invention.

FIG. 2 is a cross-sectional view for explaining a progress process of a synthetic resin flow in a cavity in the molding die of FIG.

FIG. 3 is a cross-sectional view for explaining a progress process of a synthetic resin flow in a cavity when a different molding die as an outer gate is used.

FIG. 4 is a cross-sectional view for explaining a progress process of a synthetic resin flow in a cavity in a conventional molding die.

FIG. 5 is a perspective view showing an example of wheels of a caster formed using a conventional forming die.

[Explanation of symbols]

 11a, 11b: mold, 12: cavity, 13: gate, 14: passage, 15: resin flow obstruction rod, 16: elastic body, 17: runner, 18: weld line.

Claims (5)

(57) [Claims] 1. A synthetic resin wheel formed by an injection molding method comprising injecting a synthetic resin through a gate into a cavity corresponding to the shape of a synthetic resin wheel formed in a pair of molds. A synthetic resin wheel, wherein a turbulence is generated at a junction of the injected synthetic resin flow and a weld line is formed in a complicated shape. 2. A synthetic resin wheel injection molding method comprising: injecting a synthetic resin through a gate into a cavity corresponding to a shape of a synthetic resin wheel formed in a pair of molds. Injection molding is started with the resin flow obstruction rod that can advance and retreat into the cavity from the cavity inner wall portion opposite to the gate, and the tip of the injected left and right synthetic resin flow is applied to the resin flow obstruction rod. This causes a turbulent flow at the junction of the left and right synthetic resin flows, and the resin flow obstruction rod is gradually retracted out of the cavity by the filling pressure of the synthetic resin flow to complete the injection of the synthetic resin flow. A method of molding a wheel made of a synthetic resin. 3. A pair of dies for injection-molding a synthetic resin wheel, wherein at least one of the dies communicates with the inside of the cavity on the inner wall of the mold opposite to the gate position. And a resin flow obstruction rod is slidably disposed in the passage, and a free end portion of the resin flow obstruction rod is led out into the cavity in a free state.
A synthetic resin wheel molding die apparatus, wherein the resin flow obstruction rod can be almost completely retracted into the passage by the pressure inside the cavity. 4. The resin flow obstruction rod is urged via an elastic body, and the tip of the resin flow obstruction rod is guided into the cavity in a free state by the urging force of the elastic body. The molding die for a synthetic resin wheel according to claim 3, wherein: 5. The molding die for a synthetic resin wheel according to claim 3, wherein the resin flow obstructing rod is led into the cavity from both the dies.