JPH09254240A - Drawing rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sore of the leading end surface of a press member or the heating and softening of the bottom part of a preform by forming the leading end surface of the press member into a protruding surface and providing a large diameter metal core to the central part thereof and forming the central part of the contact surface of the press member by the leading end surface of the metal core and connecting the rear end part of the metal core to a metal rod. SOLUTION: The leading end surface of the press member 12 of a drawing rod 10 is formed into a protruding surface and a metal core 13 made of aluminum is inserted in the screw hole 14 bored in the central part thereof to be screwed in the screw hole 15 within the leading end of a metal rod 11 from its leading end surface and the press member 12 is threaded with the leading end of the metal rod 11. Further, the central part 16 of the contact surface of the press member 12 is formed by a countersink. Since the central part of the press member 12 is composed of the metal core 13 good in heat conductivity, the heat accumulation quantity of the press member 12 is little and the central part 16 of the contact surface always precedes at a time of drawing to closely come into contact with an inner bottom surface to stretch a bottom part and, therefore, the heat effect on the peripheral edge part of the press member 12 from the bottom part is reduced and the problem caused by heat accumulation is hard to generate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch rod used for stretch-blowing an injection-molded preform into a hollow molded article such as a bottle.

[0002]

2. Description of the Related Art FIG. 3 shows an example of stretch-blow molding, in which a preform 1 in a heated state is transferred while holding its mouth.
However, when the blow mold 2 is positioned at the center of the blow mold 2 in the mold open state, the blow mold 2 is closed. The stretch rod 3 is inserted into the preform in parallel with the mold closing. The stretch rod 3 is inserted into a blow core 4 that closes the mouth of the preform 1, and a pressing member 5 is screwed to the tip.

The pressing member 5 contacts the inner bottom surface of the preform 1 by the extension of the drawing rod 3 and extends the preform 1 in the axial direction until the bottom portion 1a reaches the bottom die 6. Almost at the same time as this stretching operation, compressed air is blown into the preform from the blowing core 4, and the air pressure causes the preform 1 to expand to fill the cavity and become a bottle (not shown) having a thin body.

[0004]

In an ordinary preform, when the bottom part is molded in the same manner as the body part, the drawn rod may be too soft to penetrate, so as a means for preventing this, the wall thickness of the bottom part should be smaller than that of the body part. It is thinly molded so that it is easier to cool than the barrel during injection molding, and the bottom is molded to a hardness that can withstand the pressing force of the stretch rod.

As the pressing member, silicone rubber, resin, or the like is used in terms of controlling heat loss at the bottom of the preform at the time of contact and heat resistance. However, these are inferior in thermal conductivity and thus easily accumulate heat, and when the heated preform is repeatedly stretched, the heat from the preform is accumulated and the temperature of the tip portion in contact with the inner bottom surface rises.

The heat storage of the pressing member becomes extremely high due to the stretching work for a long time, and the pressing member presses the bottom portion of the preform by the front end surface.
The tip surface may be sorely deformed, or the bottom part molded to an appropriate hardness is softened more than necessary by the heat from the pressing member, and the center that is in close contact with the pressing member before reaching the bottom mold The part is extremely thinly stretched, which causes defective molding of the bottom part. Further, in the case of a preform having a large axial draw ratio, sometimes the bottom portion is pierced, and blown air leaks from the bottom portion, making it impossible to mold.

The present invention has been conceived in order to solve the above-mentioned conventional problems, and an object thereof is to solve the heat accumulation in the pressing member by adopting a member having good heat conduction as a part of the pressing member. However, it is intended to provide a new stretch rod which prevents the sore of the front end surface and the heating and softening of the bottom of the preform, thereby preventing defective products even if stretch blow molding is performed for a long time.

[0008]

According to the present invention for the above object, in a stretched rod having a pressing member such as a heat resistant resin which is in contact with the inner bottom surface of a preform at the tip of a metal rod, the tip surface of the pressing member is A metal core having a large diameter is formed in the center while forming a convex surface, and the tip end surface of the metal core forms the center of the contact surface of the pressing member, while the rear end of the metal core is connected to the metal rod. , Is.

Further, according to the present invention, the metal core is an aluminum screw screw, and the screw screw is screwed into the tip portion of the metal rod from the contact surface with the central portion of the pressing member formed of heat-resistant nylon (polyamide). Then, the pressing member is screwed to the tip of the metal rod, and the central portion of the contact surface of the pressing member is formed with a screw tray.

In the above structure, since the central portion of the pressing member that is most likely to receive heat from the bottom of the preform during stretching is formed of a metal such as aluminum having good heat conductivity,
Even if the pressing member is made of heat-resistant resin with poor thermal conductivity, the heat received from the bottom of the preform is immediately transferred from the center to the metal rod, so that heat is less likely to accumulate in the pressing member, and it is formed on a convex surface. In the front end surface, the central part precedes the inner bottom surface in close contact, so the heat effect from the bottom side on the peripheral edge of the pressing member is small, and even if stretching is repeated for a long time, the heat of the front surface will be soaked due to heat accumulation. Unnecessary softening due to heating of the preform bottom is prevented.

Further, the heat loss at the bottom of the preform is limited to the central portion with which the metal core is in contact, and the portion is finally pressed against the bottom mold to be flattened, so that the heat due to contact with the metal core is lost. The loss does not make molding the bottom difficult. In addition, when the pressing member is made of nylon, the smoothness of nylon makes sliding of the inner peripheral surface of the preform during stretching better than before, and enables smooth stretching in the axial direction. .

[0012]

1 and 2 show an embodiment of the present invention, in which a drawing rod 10 is provided with a pressing member 12 formed of nylon 6, nylon 6-6 or the like at the tip of a metal rod 11. It consists of The pressing member 12
A large diameter metal core 13 made of aluminum or the like is provided at the center of the
Is provided.

The embodiment shown in FIG. 1 is a case in which the metal core 13 is provided as a screw screw in the central portion of the pressing member 12, and the tip end surface is formed in a convex surface of a gentle curved surface in the central portion of the pressing member 12. A screw hole 14 is formed, and the screw hole 14
The metal core 12 is screwed into the screw hole 15 in the tip of the metal rod 11 from the tip end surface to screw the pressing member 12 to the tip of the metal rod 11, and the pressing member with a screw tray having a diameter larger than the screw shaft. A contact surface center 16 of 12 is formed.

In the embodiment shown in FIG. 2, a screw hole 17 is bored in the center of a pressing member 12 having a convex tip surface, and a short shaft-shaped head having a large diameter is provided on the tip side of the screw hole 17. The metal core 13 having a portion is provided by insert molding, and the pressing member 1
The contact surface center 16 of 2 is formed by the head portion, and the pressing member 12 is screwed into the threaded rod 18 until the tip of the threaded rod 18 protruding from the tip of the metal rod 11 contacts the metal core 13. It is attached to the tip of the stretching rod 10.

In the above embodiment, the pressing member 12 is used.
Since the central part of the core is made of a metal core 13 such as aluminum having good heat conductivity, even if the pressing member 12 is formed of a heat resistant resin such as nylon having poor heat conductivity, the heat received from the bottom of the preform abuts. Metal rod 1 immediately from the center 16
Heat is transferred to 1. Therefore, the amount of heat stored in the pressing member 12 is small, and since the tip end surface is formed into a convex surface, the center 16 of the contact surface always precedes and closely contacts the inner bottom surface during stretching, and the bottom portion is pushed out. The influence of heat from the bottom side on the peripheral portion of the pressed member 12 is small, and the problem due to heat storage is unlikely to occur even during the drawing and blowing operation for a long time. Moreover, the smoothness of nylon improves the slippage of the inner peripheral surface of the preform, so that the stretch in the axial direction also becomes smooth.

Further, since the portion where the pressing member 12 is mainly in contact with the bottom of the preform is the center 16 of the contact surface on which the metal core 13 is provided, the heat loss on the bottom side due to the contact is limited to the center, and the bottom is bottom. At the time of reaching the mold, the bottom portion is pressed by the metal core 13 and formed into a flat shape.
Even if the temperature is lowered by contact with 3, the molding of the bottom portion will not be impaired.

Furthermore, as shown in FIG. 1, when the screw screw is also used as the metal core 13 for heat conduction, the contact area between the metal rod 11 and the metal core 13 can be set large,
The heat transfer efficiency is high, and the heat transfer of the metal rod 11 is radiated from the rod surface.
Since the heat is transferred to the other metal parts on the upper part connected to 1, the heat will not be trapped in the stretch rod 10.

[Brief description of drawings]

FIG. 1 is a partially longitudinal tip portion of an embodiment of a stretch rod according to the present invention.

FIG. 2 is also a partially longitudinal tip portion of another embodiment.

FIG. 3 is an explanatory diagram of general stretch blow molding.

[Explanation of symbols]

 10 Drawing Rod 11 Metal Rod 12 Pressing Member 13 Metal Core 16 Center of Contact Surface

Claims (2)

[Claims] 1. A stretched rod having a pressing member made of heat-resistant synthetic resin or the like in contact with the inner bottom surface of a preform at the tip of a metal rod, wherein the tip surface of the pressing member is formed into a convex surface and has a large diameter in the central portion. The stretched rod, wherein the metal core is provided, and the tip end surface of the metal core forms the center of the contact surface of the pressing member, and the rear end of the metal core is connected to the metal rod. 2. The metal core is a screw screw made of aluminum, and the screw screw is screwed into the center of the pressing member made of heat-resistant nylon from the end face into the end part of the metal rod, and the pressing member is made of metal. A stretched rod, characterized in that it is screwed to the tip of the rod, and the center of the contact surface of the pressing member is formed with a screw pan.