KR20170021389A

KR20170021389A - Three-way mold for injection molded plastic gear having improved overflow structuer

Info

Publication number: KR20170021389A
Application number: KR1020150115162A
Authority: KR
Inventors: 김석진; 노재두
Original assignee: 우리정공(주)
Priority date: 2015-08-17
Filing date: 2015-08-17
Publication date: 2017-02-28

Abstract

The present invention relates to a three-stage mold for injecting a plastic gear having an improved overflow structure and, more specifically, to a three-stage mold for injecting a plastic gear having an improved overflow structure, comprising: a top fixing plate and a lower fixing plate; a bottom plate; an upper plate; a runner plate; an upper portion core; and a lower portion core.

Description

TECHNICAL FIELD [0001] The present invention relates to a three-step mold for injection molding a plastic gear having an improved overflow structure,

The present invention relates to a three-stage mold for injecting a plastic gear having an improved overflow structure, and more particularly, to a mold for injecting a plastic gear into which a resin filled into a cavity overflows to an overflow hole formed between gates, Stage mold for injecting a plastic gear with an improved overflow structure for dispersing a reinforcing material component.

Plastic gears have become a key component in replacing traditional metal gears in a variety of applications, and the range in which plastic gears are used has been extended to more demanding powertrains, from low-power precision motion transmitters.

Plastic gears are lighter than metal gears, have lower moment of inertia, are less noisy than metal gears, plastic gears usually do not need lubricant, or contain internal lubricants such as PTFE or silicone. Generally, plastic gears are lower in price than metal gears, and can be designed to include various functions required for assembly, and have a strong resistance to corrosion compared to metal.

The first thermoplastic gears used in these plastic gears were simple nylon and acetal gears that carried small loads at low speeds, but with the benefits of using thermoplastic gears clear, new high performance materials were introduced, .

In particular, the use of thermoplastic resin gears has started to become more diverse due to the use of reinforcing agents and internal lubricants synthesized in plastic materials.

However, when a reinforcing material such as glass, carbon, or aramid is applied to a resin, the abrasion coefficient is significantly lowered in most resin systems. However, glass and carbon fiber cause warping due to anisotropic shrinkage in the mold The accuracy of the gear is lowered.

In order to precisely mold the plastic resin gear product, the arrangement of the gates formed on the cavity is very important.

FIG. 1 is a view showing an example of a shape in which a gate is disposed on the upper part of a conventional cavity, and FIG. 2 is a view showing an example of a state in which a molded product is cured in a conventional three-

Referring to the drawing, three or six gates 34 are radially arranged on the upper part of the cavity 42 so that a uniform amount of resin is supplied simultaneously into the cavity 42 for each gate 34, Reduce product quality.

However, a weld line L is formed at a portion where the resin filled in the cavity 42 in each of the gates 34 is in contact with each other. As the gas is injected into the weld line L, air is trapped in the mold, The melting temperature and the cavity pressure are changed.

As a result of such changes in the conditions, the surface strength, dimensional deviation, roundness, etc. of the gear are influenced, resulting in a problem that the finished product is inferior.

In addition, a reinforcing material such as glass or carbon contained in the resin is pushed toward the weld line L due to the difference in specific gravity, so that the product is easily broken at the weld line, and the glass material is exposed to the surface of the product, A serious problem occurs.

Accordingly, there is a demand for a three-stage mold for injection molding of a plastic gear in which a reinforcing material such as gas or glass is mixed with the weld line generated between such conventional gates to improve the structure so as not to cause defective gear products by the weld line Is increasing.

Korean Patent Publication No. 2008-0007945

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to overcome the problem of overflow of the resin filled into the cavity through the gate, To disperse the stiffener component in the overflow hole.

Another object of the present invention is to form an overflow hole in the upper core to separate the upper and lower molds in order to take out the molded product in the cavity, so that the cured resin in the overflow hole is automatically separated from the molded product.

According to an aspect of the present invention, there is provided an image forming apparatus including upper and lower fixing plates provided on upper and lower portions, a lower plate provided on an upper portion of the upper plate to form a forming portion, A runner plate provided between the upper plate and the upper plate to form a runner through which the resin passes; and an upper core and a lower core interposed between the upper plate and the lower plate to form a molded part, , A spiral in which the molten resin supplied through the nozzle at the upper portion of the upper fixing plate is injected to the lower runner plate side is formed and the resin transferred to the lower end portion of the upper core is radially branched at the same angle A branch portion is formed, and each end portion of the branch portion penetrates downwardly of the upper core, Wherein a lower end of the runner is formed with a gate smaller than the flow path of the runner and a space in which the resin flowing through the respective gates is filled in the lower core is filled with a resin in the form of a molded product An overflow hole is formed between the respective gates radially disposed on the upper portion of the cavity to a certain depth from the lower surface of the upper core to the inside of the upper core so that the resin is filled inside the cavity through the gate , The resin flowing into the cavity overflows to an overflow hole formed on the cavity.

Wherein the overflow hole is disposed on a weld line where resin supplied through each gate is generated by mutual contact in the cavity.

In addition, the overflow hole is disposed so as to be closer to the outer surface of the cavity where the tooth is formed to have a tooth profile than the central axis of the cavity.

Further, the overflow hole is formed to penetrate from the lower surface of the upper core to the upper surface of the upper core, one side is inserted into the runner plate, the other side passes through the lower surface of the runner plate, Wherein when the upper core and the lower core are separated from each other, a hardened resin in the overflow hole is separated from the molded article in the cavity while being fixed to the end of the lock pin.

According to the present invention, the resin charged into the cavity through the gate overflows to the overflow hole, thereby dispersing the reinforcement component such as gas or glass, which is poured into the weld line, into the overflow hole, Development, exposure of the surface glass, and the like, thereby reducing defects in the finished product.

In addition, when the upper and lower molds are separated in order to take out the cured molded article in the cavity, the resin hardened in the overflow hole is automatically separated from the molded article while being fixed to the lock pin, It is possible to reduce the production cost.

1 is a view showing an example of a shape in which a gate is disposed on a conventional cavity.
2 is a view showing an example of a state in which a molded product is cured in a conventional three-stage mold.
3 is a cross-sectional view of a three-stage mold for injecting a plastic gear according to an embodiment of the present invention.
4 is a view showing an example of a runner in which a three-stage mold according to the present invention is separated and discharged.
5 is a view showing an example of a shape in which a gate and an overflow hole are disposed on a cavity according to the present invention.
6 is a detailed view showing the flow of the resin in the three-stage mold according to the present invention.
7 is a sectional view showing a state in which a three-stage mold is separated according to the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a sectional view of a three-stage mold for injection of a plastic gear having an improved overflow structure according to the present invention, FIG. 4 is a view showing an example of a runner in which a three- And FIG. 5 is a view showing an example of a shape in which a gate and an overflow hole are disposed on a cavity according to the present invention.

Referring to the drawings, a three-stage mold for injecting a plastic gear with an improved overflow structure according to the present invention includes an upper fixing plate 10 and upper and lower plates 50 and 50 mounted on upper and lower sides, A lower plate 40 which forms a molding part, a upper plate 30 which is provided at the lower part of the upper fixing plate 10 and forms a molding part, and a lower plate 40 which is provided between the upper plate 30 and the upper fixing plate 10, And a lower core 41 which is interposed between the upper plate 30 and the lower plate 40 so as to form a molded part so that the upper spool The molten resin supplied through the nozzles in the nozzle 11 is branched to both sides through the runner plate 20 to form the runner 33 which is a passage through which the resin is moved to the cavity 42. [

In the present invention, a sprue 11 is formed in which the molten resin supplied through the nozzle A from above the upper fixing plate 10 is injected toward the lower runner plate 20 side. This sprue 11 serves as an inlet through which the molten resin is fed into the cavity 42 through the runner and gate 34 and the radius of the sprue 11 bushing is equal or slightly larger than the nozzle radius And the hole of the sprue 11 is formed to be equal to or slightly larger than the nozzle hole.

The resin injected downward through the sprue 11 is conveyed to the branching portion 32 having a radial groove shape on the upper surface of the upper core 31 to be guided along each branching path of the branching portion 32 The resin is dispensed.

At each end of the branching section 32, a runner 33 penetrating downwardly of the upper core 31 and branched down to the branching section 32 is downwardly radially formed.

At the lower end of the runner 33, a gate 34 smaller than the flow path of the runner 33 is formed. The gate 34 is formed at the lower end of the upper core 31 and acts as a gate through which the resin flows from the runner into the cavity 42. The size of the gate 34 is determined by the thickness, Loses.

The lower core 41 is closely attached to the lower portion of the upper core 31. The resin flowing through the gates 34 formed at the lower end of the upper core 31 is filled in the lower core 41 The cavity 42 is formed.

The interior of the cavity 42 is formed in the same shape as the shape of the molded product. The three-stage mold of the present invention is for injecting a gear product. The inside of the cavity 42 is cylindrical, Axis.

Here, the gates 34 are formed on the lower surface of the upper core 31 so as to be radially spaced from each other at regular intervals with respect to the central axis of the cavity 42 as shown in Fig. Thus, the gate 34 surrounds the gate 42 in a circular arc with respect to the central axis of the cavity 42, so that the resin is simultaneously supplied to the inside of the cavity 42 through the gates 34.

An overflow hole 35 is formed at a certain depth from the lower surface of the upper core 31 to the inside of the upper core 31 between the gates 34 radially disposed above the cavity 42.

This overflow hole 35 is located above the weld line L where the resin charged into the cavity 42 from the adjacent two gates 34 abuts and is generated so that the resin charged into the cavity 42 And overflows along the overflow hole 35 to improve the gas flow phenomenon in the weld line and the inner filling material.

The overflow hole 35 is disposed on the line of the weld line L so as to be closer to the outer surface of the cavity 42 which is formed to have a tooth profile than the center axis of the cavity 42. [ The resin charged into the cavity 42 spreads in both directions so that the gas is more likely to flow toward the outer side of the cavity 42 so that the overflow hole 35 is located closer to the outer side of the cavity 42 Ensure smooth gas discharge.

Hereinafter, a method of injecting a gear product using a three-stage mold for injecting a plastic gear with an overflow structure according to the present invention will be described in detail.

FIG. 6 is a detailed view showing the flow of the resin in the three-stage mold according to the present invention, and FIG. 7 is a view showing a sectional structure in a state where the three-stage mold is separated according to the present invention.

Referring to the drawing, the resin is injected downward along the sprue 11 through the nozzle, and the resin is transferred to the branch portion 32, which is radially branched at the lower end of the sprue 11. [ In this branched portion 32, the resin is distributed to the respective branched paths in a uniform amount, and the resin is transported along the runners 33 connected to the respective ends of the branched portions 32 downwardly. The resin is filled into the cavity 42 through the gate 34 formed in the cavity 42. [

The resin filled into the cavity 42 is overflowed to the upper portion along the overflow hole 35 formed between the gates 34 while being filled in the cavity 42. [

As described above, the overflow hole 35 is positioned above the weld line, and the gas, which is pumped into the weld line, is guided to the overflow hole 35 to improve the gas flow phenomenon, and the glass, carbon, Is transferred to the overflow hole (35) without being caught by the weld line, thereby improving the strength of the weld line.

7, the three-stage mold is separated to automatically separate the runner 33 from the molded product. In the present invention, not only the runner 33 but also the overflow hole 35 is hardened So that the resin is automatically separated.

In the present invention, an overflow hole 35 is formed to penetrate from the lower surface of the upper core 31 to the upper surface of the upper core 31. And the lock pin 23 whose one end is inserted into the runner plate 20 and whose other end passes through the lower surface of the runner plate 20 and whose end is protruded by the overflow hole 35 is inserted into the overflow hole 35 .

When the upper core 31 and the lower core 41 are separated from each other, the resin hardened in the overflow hole 35 is fixed to the end of the lock pin 23, And is automatically separated from the molded product in the cavity (42).

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications and variations without departing from the spirit and scope of the invention. Accordingly, the scope of the appended claims should include all such modifications and changes as fall within the scope of the present invention.

10: phase fixing plate 11: sprue
20: runner plate 23: lock pin
30: upper plate 31: upper core
32: branch 33: runner
34: gate 35: overflow ball
40: Lower plate 41: Lower core
42: cavity
50: And the rest

Claims

An upper fixing plate provided on the upper and lower portions,
A lower plate provided above the upper plate to form a forming portion,
A top plate provided at a lower portion of the upper fixing plate to form a forming portion,
A runner plate disposed between the upper plate and the upper plate to form a runner through which the resin passes,
And an upper core and a lower core interposed between the upper plate and the lower plate to form a molded part,
A spout in which the molten resin supplied through the nozzle is injected to the lower runner plate side is formed on the upper fixed plate,
A branch portion is formed on the upper surface of the upper core so that the resin to be transferred to the lower end portion of the sprue is radially branched at the same angle,
Wherein a runner is formed at each end of the branch portion so as to penetrate downwardly of the upper core and to be branched down to the branch portion,
A gate smaller than the flow path of the runner is formed at the lower end of the runner,
A cavity formed in the form of a molded product is formed in a space inside the lower core where the resin flowing through the respective gates is filled,
An overflow hole is formed between the respective gates radially disposed on the upper portion of the cavity so as to have a predetermined depth from the lower surface of the upper core to the inside of the upper core so that the resin is filled inside the cavity through the gate, Is overflowed with an overflow hole formed in an upper portion of the cavity. &Lt; Desc / Clms Page number 20 >

The method according to claim 1,
Wherein the overflow hole is arranged on a weld line line where resin supplied through each gate is generated in a mutual contact in the cavity.

3. The method of claim 2,
Wherein the overflow hole is disposed so as to be closer to the outer surface of the cavity where the tooth is formed to have a tooth profile than the center axis of the cavity.

The method according to claim 1,
The overflow hole is formed to penetrate from the lower surface of the upper core to the upper surface of the upper core,
Further comprising a lock pin having one side inserted into the runner plate and the other side protruding through the lower surface of the runner plate to the overflow hole,
Wherein when the upper core and the lower core are separated from each other, the resin cured in the overflow hole is separated from the molded article in the cavity while being fixed to the end of the lock pin. Three - stage mold for injection molding.