JP3449402B2 - Injection mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die in an injection molding machine for injection molding a molded product such as a cylinder from a molding material such as synthetic rubber or thermoplastic resin.

[0002]

2. Description of the Related Art A conventional example of a mold used in an injection molding machine for injection molding a long rubber pipe such as a paper feed roller pipe of a copying machine will be described with reference to FIGS. The split mold in the figure is composed of a fixed mold 1 and a movable mold 2 for horizontal installation. Upper surface of fixed mold 1 and movable mold 2
Both ends of a round rod-shaped core 4 which penetrates the center of a cavity 3 having a long circular cross section formed by abutting the lower surfaces of the two are clamped from above and below by the two dies 1 and 2. Further, for example, a gate 5 for injecting a synthetic rubber molding material from one end side of the cavity 3 is formed on the upper surface of the fixed mold 1, and both molds 1 and 2 are formed.
A burr groove 6 having an air trapping function and a burr absorbing function is formed on the center core clamping surface M of the end opposite to the gate 5.

As shown in FIG. 8A, when the molten synthetic rubber molding material 7 is injected from the gate 5 into the cavity 3, the molding material 7 flows in the cavity 3 in the direction of the arrow in FIG. 8A. The molding material 7 is filled into the cavity 3 while the air in the cavity 3 is being pushed out to the burr groove 6, and a part of the molding material 7 flows out into the burr groove 6 as a rubber burr and is absorbed, and the remaining molding material 10 is left in the burr groove 6. Harden. When the molding material 7 filled in the cavity 3 is cured, the upper and lower molds 1,
2 is opened, and the center core 4 is pressed as shown in FIG. 8 (B).
A molded product in which the pipe-shaped molded product 7 is fixed to the outer periphery of is taken out. This intermediate molded product is sent to the core extracting process shown in FIG. 9, and the core 4 is extracted from the molded product 7.

The equipment for the core extracting process shown in FIG. 9 includes a vertically movable core removing member 8 for removably fixing the upper end of the vertical core 4, and the core removing member 8 and the upper end surface of the molded product 7. A molded product removing member 9 is fixed at a fixed position between the core removing plate 8 and the core removing plate 8. As shown in FIG. 9 (B), the upper end surface of the molded product 7 is brought into contact with the lower surface of the molded product removing member 9 by raising the core removing member 8 from the state before drawing shown in FIG. 9 (A). The core 4 is raised by the core removing member 8 to pull out the core 4 from the molded product 7. When the lower end of the core 4 comes out of the molded product 7, the molded product 7 falls by its own weight and is sent to the next step.

In the next step, the molded product 7 is commercialized as, for example, a paper feed roller pipe of a copying machine. This process
For example, this includes cutting and removing the burr groove residual molding material 10 from the molded product 7, removing burrs on the inner and outer surfaces of the molded product 7, and polishing. The outer peripheral surface of the molded product 7 is polished for the purpose of adjusting the friction coefficient of the outer peripheral surface to an appropriate value for the paper feed roller. The outer peripheral surface of the molded product 7 is polished, for example, by pressing a polishing core into the cylindrical molded product 7 and polishing the outer peripheral surface.

[0006]

As shown in FIG. 8, when a cylindrical molded product 7 is injection-molded by the upper and lower molds 1 and 2, the molded product 7 has an outer periphery and an end face in the axial direction of the molded product 7. A thin burr 11 may be formed. The thin burr 11 is a rubber burr protruding from the abutting surfaces of the upper and lower molds 1, 2.
Further, a thin burr 12 protruding from the burr groove 6 may be formed at the tip of the burr groove residual molding material 10. Then, as shown in FIG. 9, a part of such thin burrs 11 and 12 is drawn into the inner surface of the molded product 7 when the core 4 is pulled out from the molded product 7, and adheres to the inner surface of the molded product 7 as it is. Sometimes. That is, when the core 4 is pulled out from the molded product 7 as shown in FIG. 9, a part of the thin burr 11 on the lower end surface of the molded product 7 or the thin burr 12 of the burr groove residual molding material 10 causes friction with the core 4. The resistance may draw the core 4 together with the inner surface of the molded product 7 and stick to the inner surface of the molded product 7.

In the case of the cylindrical molded article of synthetic rubber as described above, the polishing core is press-fitted with the burrs of the same molding material adhered to the inner surface to polish the outer peripheral surface, and when the polishing core is removed after polishing. A dent may occur at a portion corresponding to the inner surface burr-attached portion on the outer periphery of the polished molded product. Also, when a similar molded product is pressed into a resin core of a paper feed roller of a copying machine without polishing the outer periphery of the product,
A convex surface may be formed on the outer periphery of the molded product at a location corresponding to the inner surface burr adhesion portion.

The above-mentioned partial depressions and projections on the outer periphery of the cylindrical molded product impair the functions of the paper feed roller and the like. Therefore, in the past, for example, by increasing the mold clamping ability between molds in an injection molding machine so as to minimize the amount of burr generated on the outer surface of the molded product, the inner surface of the molded product is pulled out when the core is pulled out. We are trying to reduce the amount of burr that is drawn in. However, as the mold clamping capacity of the injection molding machine increases, the size of the injection molding machine increases and the cost of the entire equipment increases. Currently, it is necessary to manually remove burrs adhering to the inner surface of the molded product, or Burrs adhering to the inner surface of the product are removed by cleaning with a cleaning machine.

However, the work process of manually removing the burrs adhering to the inner surface of the cylindrical molded product is poor in workability and increases the product cost. Also, the process of cleaning the inner surface of a cylindrical molded product with a cleaning machine is easy to automate, but it is difficult to reliably remove the burrs of synthetic rubber stuck to the inner surface of the molded product only by cleaning, and reliability is high. I have a problem. In addition, it is difficult to reliably clean the inner surface of a synthetic rubber cylindrical molded product having a particularly small inner diameter, and it is the current situation that the removal of such inner surface burrs must be done manually.

An object of the present invention is to reduce the occurrence of thin burrs on a molded product without increasing the mold clamping ability of the injection molding machine, thereby avoiding and reducing the adhesion of burrs to the inner surface of the molded product. To provide the mold.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a center core is made to penetrate a central portion of a cavity formed by clamping a split mold, and a cylindrical shape formed by the outer periphery of the center core and the cavity. A mold in an injection molding machine for molding a cylindrical molded product by injecting a molding material into a space from one end of the cylindrical space, and touching around the cavity where the molds of the split mold come into contact with each other. In order to increase the touch pressure per unit area between the touch surfaces that are in direct contact with each other by reducing the contact area between the touch surfaces to a portion other than the peripheral portion along the cavity of the surface, the depth is 0.1 to 0.1%. A 5.0 mm recess is formed so that the core and
One end side where the molding material in the cylindrical space between cavities is injected
Clamp the core on the side opposite to
The burr groove, which has a pooling function and a burr absorbing function, is
How the molding material flows inside the cavity on the inner wall on the vity side
A tapered surface that rises at an angle of 45 degrees or more
The above-mentioned object is achieved by the formation .

Here, the concave portion formed on the touch surface of the split mold is formed on at least one touch surface of a pair of molds that are clamped to each other, and the touch surface around the concave portion is the counterpart. The mold is clamped by touching the touch surface. The contact area between the pair of molds to be clamped is reduced by the area of the concave part of the touch surface, and the mold clamping at the portion of the touch surface of the pair of molds that is in direct contact is proportional to this reduced area. The force is increased, and the amount of burr generated on the die-butting surface of the cavity is reduced.

Further, burr groove that is formed in the mold is a groove for storing to discharge air of the cavity when injecting a molding material into the cavity, with grooves for residual absorbs burrs of the molding material protruding from the cavity , By setting the cavity side inner wall surface of this burr groove to a tapered surface with a constant angle,
The rigidity of the molding material remaining in the burr groove is increased, and the occurrence of burr can be suppressed.

Further, according to the present invention, the center core clamping surface of the injection molding die is fixed to a fixed position adjacent to the burr groove formed on the center core clamping surface on the side opposite to the cavity. Bali groove
A second burr groove for absorbing a thin burr that protrudes is formed.
By thus forming the two burr grooves adjacent to each other on the mold core clamping surface, the burr generation can be more reliably suppressed in two steps.

[0015]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS. The injection molding die shown in this embodiment is applied to the injection molding die of FIGS. 7 and 8, and is the same as that of FIG. 7 and FIG. Avoid duplication.

The present invention is characterized in that a concave portion 20 is partially formed on the touch surface N which is the upper surface of the fixed mold 1 as shown in FIG. The touch surface N is the upper and lower molds 1,
This is a surface that comes into contact with the lower surface of the movable mold 2 when the mold 2 is clamped, and in the case of the movable mold 2, the lower surface is the touch surface.
When a plurality of cavities 3 are formed in parallel on the upper surface of the fixed mold 1 at equal intervals, a touch surface N between adjacent cavities 3 and a touch surface N outside the cavities 3 at the outermost ends.
A recess 20 is formed in the.

The concave portion 20 on the touch surface N in one region has such an area that the contact area with the touch surface of the movable mold 2 is reduced to increase the touch pressure per unit area between the touch surfaces directly contacting each other by 20% or more. And a depth of 0.1 to 5.0 mm. For example, as shown in FIGS. 1 and 2, in one touch surface N between adjacent cavities 3, one recess 20 is formed in the central portion of the touch surface N except for the peripheral edge portion along the cavity 3. As shown in FIG. 3, the depth h and the area of the recess 20 are such that the touch pressure (mold clamping force) per unit area between the touch surfaces when the upper and lower molds 1 and 2 are clamped is 20.
It is set to be 20% or more higher than the touch pressure between the touch surfaces without each other.

In the above embodiment, as shown in FIG. 3, the fixed mold 1 and the movable mold 2 clamp the center core 4 with the same mold clamping force as the conventional mold shown in FIG. When the molding product 7 is molded by filling the cavity 3 with the molding material of synthetic rubber as shown in (1), burrs do not occur in the axial direction of the outer periphery of the molding product 7, or even a small amount of burrs occurs. That is, since the concave portion 20 is formed on the touch surface N of the fixed mold 1, the touch surface N
The contact area between the touch surface of the movable mold 2 and
Even if the mold is clamped with the same mold clamping force, the touch pressure between the touch surfaces of the upper and lower molds 1 and 2 increases, and thin burr on the abutting surfaces of the upper and lower molds 1 and 2 increases in proportion to the increase in the touch pressure. Occurrence is suppressed.

As a result, when the molded product 7 is formed into a cylindrical shape using the upper and lower molds 1 and 2 and the core 4, and the core 4 is pulled out from the molded product 7 as shown in FIG. Since no thin burr is generated on the outer surface of the molded article 7, there is almost no possibility that the burr will be drawn and adhere to the inner surface of the molded product 7 when the core 4 is pulled out.

The effect of suppressing the occurrence of thin burr on the outer surface of the molded product 7 is that the touch pressure per unit area between the touch surfaces when the upper and lower molds 1 and 2 are clamped is as shown in FIG. Experiments have shown that it may be set to be higher than the touch pressure of 20% or more. The experimental example will be described.

The injection mold shown in FIG. 7 is 73 tons / 514c.
With an m2 injection molding machine, the touch pressure during mold clamping is 142
In the case of kgf / cm2, a thin burr is generated on the outer periphery of the molded product and the above-mentioned problem occurs. However, when a concave portion is formed in this mold so as to be 73 tons / 347 cm2 as in the above embodiment. It was proved that the touch pressure was increased to 210 kgf / cm @ 2 by 48% and thin burrs did not occur on the outer periphery of the molded product, and that the amount was small enough to cause no problem.

The injection molding die shown in FIG. 7 has a capacity of 90 tons / 4.
When the touch pressure at the time of mold clamping was 200 kgf / cm2 with a 50 cm2 injection molding machine, a thin burr was generated on the outer periphery of the molded product, but a concave part was formed in this mold to be 90 tons / 330 cm2 And the touch pressure is 273k
It was proved that thin burr did not occur on the outer periphery of the molded product by increasing gf / cm2 by about 36%.

The depth h of the recess 20 in the above embodiment
The reason for defining 0.1 to 5.0 mm will be described. If the depth h of the recess 20 is less than 0.1 mm, the effect of increasing the touch pressure is reduced, and thin burrs are likely to occur on the outer periphery of the molded product.
Further, if the depth h of the recess 20 exceeds 5 mm, the mechanical strength of the touch surface N of the fixed mold 1 may be reduced, which may cause the mold to settle. Further, if the depth h exceeds 5 mm, the mold temperature may fluctuate due to the accumulation of air in the deep recess 20, and the quality of the molded product may fluctuate. For the above reason, the depth h is 0.1 to 5.
0 mm is preferable, but more preferably the depth h is 0.1
A range of 3.0 mm is preferable.

In the above embodiment, the recess 20 is formed only on the touch surface N of the fixed mold 1. However, a similar recess may be formed only on the touch surface of the movable mold 2, or both the molds may be formed. You may form a recessed part in the touch surface of molds 1 and 2.

Next, the present invention will be described with reference to FIGS. 5 and 6. In this embodiment, the fixed mold 1 and the movable mold 2 are butted against each other and the center core 4 is clamped. The first burr groove 21 and the second burr groove 22 are formed adjacent to each other on the surface M. This pair of burr grooves 2
The core die clamping surface M on which the first and the second parts 22 are formed is the cavity 3
Is located on the downstream side in the injection direction of the molding material. The first burr groove 21 shown in FIG. 5 is a groove for an air vent pool when the molding material of synthetic rubber is injected into the cavity 3, and is a groove for absorbing and accumulating burrs of the molding material protruding from the cavity 3. It corresponds to the burr groove 6 in FIG.

The feature of the first burr groove 21 different from the burr groove 6 of FIG. 7 is that the inner wall surface 21a of the first burr groove 21 on the side of the cavity 3 is 45 with respect to the inflow direction of the molding material in the cavity 3. That is, the taper surface rises at an angle θ of not less than 10 degrees. By the way, the rising angle corresponding to the above-mentioned angle θ of the cavity side inner wall surface of the burr groove 6 in FIG. 7 is about 45 degrees at the maximum, and therefore, the burr groove 6 has a maximum depth of about 2 mm. In the groove 6, a thin burr is likely to occur further rearward. However, when the inclination angle θ of the cavity side inner wall surface 21a is set to 45 degrees or more like the first burr groove 21, the depth of the first burr groove 21 can be increased to about 2 to 5 mm, and When the burr absorption capacity of the burr groove 21 and the rigidity of the residual molding material 23 of synthetic rubber which flows into the first burr groove 21 and hardens increases, and when the core 4 is pulled out from the molded product 7 as shown in FIG. With this frictional resistance, the cushion effect in which the burr groove residual molding material 23 elastically deforms can be expected.

Therefore, when the core 4 is pulled out from the cylindrical molded product 7, the high-rigidity burr groove residual molding material 23 formed by the first burr groove 21 makes it difficult for the burr to enter the inner surface of the molded product 7. Moreover, the cushion effect of the burr groove residual molding material 23 makes it difficult for the thin burr to enter the inner surface of the molded product 7.
The possibility of thin burrs of synthetic rubber adhering to the inner surface of the molded product 7 is greatly reduced.

The second burr groove 22 adjacent to the first burr groove 21 is a groove that absorbs a thin burr of the molding material protruding from the first burr groove 21, and the first burr on the center mold clamping surface M. Groove 21
In addition to the above, by forming the second burr groove 22, thin burr generation is suppressed in two steps, and the molded product 7 when the core 4 is pulled out from the cylindrical molded product 7 as shown in FIG. The thin burr can be more reliably prevented from entering the inner surface of the.

In particular, if the clearance between the center core type clamping surface M and the center core 4 behind the second burr groove 22 is set to 0, the generation of thin burrs can be further effectively suppressed. Also,
The depth of the second burr groove 22 is set to be larger than that of the first burr groove 21, and the rigidity of the burr groove residual molding material 24 that enters the second burr groove 22 and hardens is set to the first burr groove. If the rigidity is set to be larger than the rigidity of the residual molding material 23, the effect of preventing burrs from entering the inner surface of the cylindrical molded product 7 is improved.

Although the above embodiment has been described with reference to the case where a cylindrical molded product for a paper feed roller is injection molded with a synthetic rubber molding material, the present invention is not limited to this.
It can also be applied to a mold for injection-molding other long resin-made cylindrical molded products.

[0031]

According to the present invention , the touch pressure per unit area of the touch surface between molds is increased without increasing the mold clamping ability of the injection molding machine, and the occurrence of thin burrs on the outer surface of the molded product is suppressed. Therefore, it is advantageous in terms of capital investment,
Further, it is possible to provide an injection mold that simplifies the burr removal work after molding the molded product.

Further, since the thin burr of the outer surface of the molded cylindrical molded article can be suppressed by using a corrugating, deposited thin burrs on the inner surface of the molded article when pulling the center core from the molded article invades Therefore, the work of removing burrs from the inner surface of the cylindrical molded product when finishing the cylindrical molded product as a paper feed roller etc. is omitted or simplified. The manufacturing process and manufacturing cost of a cylindrical molded product such as a roller pipe can be reduced.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing an embodiment of an injection molding die according to the present invention.

FIG. 2 is a partially enlarged sectional view of the injection mold of FIG. 1 in a direction orthogonal to a cavity.

FIG. 3 is a partially enlarged sectional view of the injection molding die shown in FIG.

4 is a partially enlarged cross-sectional view of the injection molding die shown in FIG. 1 during injection molding of a molding material.

5A is a partially enlarged cross-sectional view in a direction parallel to the cavity of the injection molding die in FIG. 1, and FIG. 5B is a partially enlarged cross-sectional view at the time of molding material injection molding.

6 (A) is a cross-sectional view of a facility for extracting a core from a tubular molded product molded by the mold of FIG.
FIG. 6B is a cross-sectional view when the center core is pulled out.

FIG. 7A is a sectional view of a conventional injection molding die, and FIG.
Is a sectional view taken along line XX, and (C) is a sectional view taken along line YY.

8 (A) is a cross-sectional view of the mold shown in FIG. 7 when the molding material is filled, and FIG. 8 (B) is a front view of an injection-molded molded product.

9 (A) is a cross-sectional view of a facility for pulling out a core from a tubular molded product molded by the mold of FIG.
FIG. 6B is a cross-sectional view when the center core is pulled out.

[Explanation of symbols]

1 mold (fixed mold) 2 molds (movable molds) 3 cavities 4 core 7 molded products M Core type clamping surface N touch surface 20 recess 21 burr groove (first burr groove) 22 Second burr groove

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 33/00-33/76 B29C 39/26-39/34 B29C 43/36-43/42 B29C 45/26-45 / 37 B29C 49/48-49/54

Claims (2)

(57) [Claims] 1. A core is made to penetrate through the center of a cavity formed by clamping a split mold, and a cylindrical space formed by the outer periphery of this core and the cavity is A mold in an injection molding machine that molds a molding material by injecting a molding material from one end, and a peripheral portion along a cavity of a touch surface around the cavity where molds of a split mold come into contact with each other. A recess having a depth of 0.1 to 5.0 mm is formed in a portion other than the above so as to reduce the contact area between the touch surfaces and increase the touch pressure per unit area between the touch surfaces that directly contact each other by 20% or more. , The molding material in the cylindrical space between the core and the cavity is injected
On the side opposite to the one end side for clamping the core
The burr groove which has the function of collecting air and the function of absorbing burr,
The inner wall surface on the cavity side is the molding material inside the cavity.
Rises at an angle of 45 degrees or more with respect to the inflow direction of
An injection-molding die characterized by being formed with a flat surface . To 2. A core clamping surface in the injection mold according to claim 1, in position adjacent the opposite side of the cavity with respect to the formed burr groove on the inside core clamping surface, burr groove Karami
An injection molding die characterized in that a second burr groove for absorbing thin burr is formed.