JPH0739111B2 - Method for manufacturing umbrella handle made of hollow molded product - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an umbrella handle made of a synthetic resin, particularly a curved umbrella handle having a J-shape or L-shape by an injection molding method.

[0002]

2. Description of the Related Art Conventionally, a solid umbrella has been generally used as a handle of a synthetic resin, but the handle itself may be hollow in order to reduce the weight of the umbrella and enhance portability. Is desired. However, there is no means for easily and inexpensively obtaining a hollow molded product having a J-shaped or L-shaped curved handle, which has good assemblability with the umbrella body, strength, and finish.

That is, although the extrusion molding method can manufacture a straight hollow body such as a pipe, it cannot directly form a hollow body having a curved shape or a bent shape with a small radius of curvature.
In addition, in order to form a hollow body with closed ends, it was necessary to carry out the fusion sealing by secondary processing. In the blow molding method, the tube produced by the extrusion molding method is heated and softened in the mold to inflate by blowing a pressurized fluid, so the target is a thin mouthed container with a thin mouth like a bottle. Limited to

On the other hand, in the injection molding method, a sufficient amount of molten resin to fill the cavity is injected into the cavity, and then a gas body such as air is continuously injected from the injection port to fill the cavity. A method for obtaining a hollow body of meat has also been proposed (Japanese Patent Publication No. 57-1496).
No. 8, No. 46-25270, Jitsukai Sho. However, in the handle of the umbrella, it is necessary to provide the insertion portion of the pillar of the umbrella main body at one end side, and in the above proposed method, the press-fitting side of the gas body is the insertion portion, but the opening becomes narrower. In addition, the shape and wall thickness of the inner surface fluctuate depending on the press-fitting state of the gas body, and uneven thickness is likely to occur, so that there is a fatal problem that the insertion portion having a constant size and shape cannot be formed.

Therefore, in order to manufacture a curved umbrella handle having a curved shape, split molded products once prepared by an injection molding method or the like are fused together and integrated, or a hollow molding manufactured by an extrusion molding method. Although it will be bent in the state of being softened by heating,
Since these methods require secondary processing after molding,
There are problems that the process is complicated, the manufacturing efficiency is poor, the cost is high, and the finished appearance of the fused portion and the bent portion is easily deteriorated.

In view of the above situation, the present invention makes it possible to easily manufacture a curved and hollow synthetic resin umbrella handle with a single molding at a low cost, and further, to provide an umbrella pillar provided at one end side. It is an object of the present invention to provide an epoch-making method in which the insertion portion is a tubular portion having a constant size and shape without uneven thickness.

[0007]

In order to achieve the above object, a method for producing a hollow molded article according to the present invention is an injection molding method using a molding die having a cavity corresponding to a curved shape of a handle of an umbrella. A cylindrical core having a small hole in the tip end surface is inserted into a linear portion on one end side of the cavity to form an annular space around the core, the inside of the core is water-cooled, and the cavity is formed. Molten resin is injected into the molding die from a sprue gate provided near one end of the core, and after the injected molten resin fills the annular space and covers the front end surface of the core, the pressure is inserted into the core. By introducing a pressurized fluid into the molten resin through the small holes through the fluid supply pipe, the molten resin is expanded in the molding die and spread on the entire inner surface of the die.

[0008]

In the method of the present invention, when a pressurized fluid is introduced into the molten resin after the molten resin injected into the mold covers the tip end surface of the core, bubbles of the fluid are formed in the molten resin. By continuing to introduce the fluid, the bubble grows, and along with this, the molten resin expands into the mold while expanding, and finally spreads over the entire inner surface of the mold. A curved umbrella handle having a hollow bubble portion can be obtained. The handle has a straight tubular portion made of a resin filled in an annular space around the core on one end side, and a partition wall portion is formed between an inner bottom and a hollow portion of the tubular portion, and the tubular portion is formed. And the hollow portion communicate with each other through a small diameter hole formed outside the small hole of the core when the pressurized fluid is introduced.

Although the above-mentioned cylindrical portion serves as a plug-in portion of the pillar of the umbrella body in assembling the umbrella, since it is formed by the core that is inserted into the cavity, fluctuations in the inner diameter and distortion of the inner peripheral surface occur. There is no need to make the opening narrow, and it is possible to always set a constant size and shape.
Since the partition wall portion serves as a positioning portion that abuts the lower end of the support column and regulates the insertion depth, the support column can be securely inserted and connected and fixed in a stable state. Further, the water cooling inside the core during molding accelerates the hardening of the molten resin filled in the annular space around the core, and the intrusion of the pressurized fluid introduced by the molten resin into the annular space is reliably prevented. Since there is no possibility that a bubble of fluid will be mixed in, a hole or a defective portion will not be formed, and an uneven thickness will not occur in the cylindrical portion, by appropriately setting the wall thickness by the outer diameter of the core, Sufficient strength and a good appearance can be imparted to the support of the column.

On the other hand, since the size of the hollow portion can be arbitrarily set depending on the introduction amount of the pressurized fluid, it is possible to form the hollow portion as a whole excluding the tubular portion of the molded product, and of course to form a partial hollow portion. Is also possible. Thus, the wall thickness in the hollow portion can be adjusted by setting conditions such as the viscosity of the molten resin, the fluid introduction speed, and the cooling and hardening speed. As the fluid, any fluid may be used as long as it has poor reactivity with the resin component and does not adversely affect the moldability and the resin characteristics, air,
In addition to gases such as oxygen gas, nitrogen gas and carbon dioxide gas, non-volatile liquids having a high boiling point can also be used.

Further, in order to carry out the method of the present invention, it is only necessary to provide the mold for injection molding with the inlet for the pressurized fluid and the core, so that various existing injection molding apparatuses can be used as they are and the injection molding can be performed. The resin to which the method can be applied is not limited to a thermoplastic resin, and a thermosetting resin can be used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an injection mold for producing a hollow umbrella handle. A J-shaped cavity 2 corresponding to the handle shape is formed in the mold 1, and a cylindrical shaft-shaped core 3 is inserted and arranged in a straight portion on one end side of the cavity 2 to form an annular space 2a, and a sprue gate 4 is formed. Is provided so as to communicate with the annular space 2a near the one end of the cavity 2.
Then, the air blowing pipe 5 and the cooling water introducing pipe 6 introduced from the outside of the mold are arranged inside the core 3, and the air blowing pipe 5
Of the core 3 is tightly fitted into a small hole 3a communicating with the cavity 2 and the tip of the cooling water introducing pipe 6 is located inside the core 3 near the inner end. The cooling water, which is opened in the space and flows out from the introduction pipe 6, passes through the core 3 and is discharged from a cooling water discharge pipe 7 provided at the outer end portion of the core 3. Reference numeral 8 is a nozzle of the injection molding machine connected to the sprue gate 4, and 8a is a heater covering the outer periphery thereof.

As shown in FIG. 2, in order to carry out molding, first, the cooling water 12 is made to flow out from the cooling water introducing pipe 6 in the core 3, and the molten resin is injected into the cavity 2 from the nozzle 8 to obtain the molten resin. The injection is stopped when 9 reaches a predetermined injection amount. At this time, the molten resin 9 fills the annular space 2a to a position beyond the tip of the core 3, but the portion filling the annular space 2a is hardened by heat exchange with the cooling water 12 in the core 3. is there. Next, when the blowing of the pressurized air 10 from the air blowing pipe 5 is started, bubbles 11 are formed in the molten resin 9 and the bubbles 1 are formed as shown by the one-dot chain line in FIG.
As the molten resin 9 swells, the molten resin 9 swells and advances to the inner part of the cavity 2, and finally spreads over the entire inner surface of the cavity 2 as indicated by the chain double-dashed line in FIG. At this point, the blowing of the pressurized air 10 is stopped and the molten resin 9 is cooled and hardened. When the blowing of the pressurized air 10 is stopped, the cavity 3
, The injection amount set value of the molten resin 9 and the air blowing speed, and can be determined empirically. The cooling water 12 is set to flow out from the cooling water introduction pipe 6 in the core 3.

FIG. 3 shows a J-shaped umbrella handle 13 which is a molded product of transparent synthetic resin taken out from the mold 1 after the above cooling and curing. This handle 13 has a straight portion 13 which is the base end side.
a, the cylindrical portion 1 based on the annular space 2a of the cavity 2
4 and a hollow portion 15 formed of an air layer in which the bubbles 11 grow in a portion extending from the lower portion of the straight portion 13a to the entire arcuate portion 13b. The cylindrical portion 14 and the hollow portion 15 are separated by the partition wall portion 17, and a small diameter hole 16 formed outside the small hole 3a (cavity side) of the core 3 due to the air blowing at the time of molding is formed. Communicate with each other.

In the handle 1, the pillar of the umbrella body can be inserted and connected to the tubular portion 14 opened at the base end, and various ornaments such as, for example, the hollow portion 15 can be inserted through the tubular portion 14 and the small diameter hole 16. A peculiar decorative property can be imparted by containing a colored string, a colored bead, a solid such as colored sand, a colored liquid, a liquid such as a transparent liquid containing metal flakes, colored particles or colored liquid bubbles. In the case of containing a liquid material, it is possible to use the liquid material as the pressurized fluid at the time of molding and omit the step of injecting into the hollow portion 15 after molding.

[0016]

According to the manufacturing method of the present invention, a synthetic resin umbrella handle having a J-shaped or L-shaped curved shape and having a hollow shape serves as an insertion portion of a pillar of the umbrella body on one end side. In addition to having a linear tubular portion, a partition wall portion that regulates the insertion depth of the pillar is provided between the tubular portion and the hollow portion, and the tubular portion is always of a constant size and shape. The pillars can be securely inserted and connected and fixed in a stable state, and there is no uneven thickness and there are no bubbles of fluid or holes or defects, so there is sufficient strength as a supporting part for the pillars and a good appearance. It is possible to directly mold the material having the above-mentioned structure easily at a low cost without the need for secondary processing. Further, the method of the present invention has an advantage that it can be carried out by utilizing existing various injection molding apparatuses as it is, only by providing a molding die in injection molding with a cylindrical core serving as an inlet for a pressurized fluid.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an injection mold used in an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a main part showing a molding process in the example.

FIG. 3 is a vertical sectional view of a handle of an umbrella manufactured in the same example.

[Explanation of symbols]

 1 Injection Mold 2 Cavity 2a Annular Space 3 Core 3a Small Hole 4 Sprue Gate 5 Air Blow Pipe (Pressurized Fluid Supply Pipe) 9 Molten Resin 10 Pressurized Air (Pressurized Fluid) 11 Bubbles 12 Cooling Water 13 Umbrella Handle 14 Cylinder Part 15 Hollow part

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // B29D 22/00 2126-4F

Claims (1)

[Claims] 1. A cavite corresponding to a curved shape of an umbrella handle.
In the injection molding method using a mold having a I, the key
A cylinder with a small hole in the tip surface in the straight part on one end side of the cavity
By arranging the core in the shape of
An annular space is formed, and while cooling the inside of the core with water,
Injecting molten resin into a mold in more Supurugeto provided near one end of the cavity, the injected molten resin is the
After filling the annular space and covering the tip surface of the core,
Through the pressurized fluid supply pipe inserted in the core,
A method for manufacturing an umbrella handle made of a hollow molded article, characterized in that a molten fluid is introduced into the molten resin to expand the molten resin in the molding die and to spread the molten resin over the entire inner surface of the die.