JPS588522Y2 - parison heating furnace - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a parison heating furnace used when blow molding a parison molded from a synthetic resin.

Conventional heating devices of this type have various structures, but most of them use a heater to directly heat the parison, which makes it difficult to adjust the heating temperature for the parison, and the entire parison has to be stretched and blown. It had the disadvantage that it was difficult to heat-treat it to a state suitable for molding.

Therefore, the present applicant buried heaters concentrically in a donut-shaped metal heating block, formed the required number of heating blocks into one cylindrical body having a parison insertion hole, and each heating block We have devised a parison heating furnace that can heat the parison using radiant heat from the parison, and can maintain an appropriate heating temperature for the entire parison by changing the temperature for each heating block.

However, even when the parison heating furnace is used, the blow-molded hollow molded products often have a poor finish.

This is mainly due to the shoulder thickness of the parison itself, and unless the shoulder thickness of the parison is removed, it is extremely difficult to mold a hollow molded product with a uniform thickness distribution.

It has been pointed out that there are various causes for the shoulder thickness of the parison that occurs during injection molding, such as the condition of the hot runner, the influence of the cooling rate of the mold, and slight misalignment of the mold. It is said that it is easy to produce meat.

However, even if the parison has some shoulder thickness, if the entire parison is stretched according to the thickness distribution,
It is possible to improve the finish of hollow molded products.

This idea was made in view of the above points, and the above-mentioned parison heating furnace, which can adjust the heating of the parison in each circumferential direction, is provided with means for heating the parison along the longitudinal direction. By partially controlling heating in the direction and longitudinal direction, the entire parison can be heated to a state suitable for stretch blow molding.

This invention will be explained in detail below using illustrated examples.

Reference numeral 1 denotes a heating block made of aluminum alloy in the shape of a doughnut, and heaters 2 are attached concentrically to the outer periphery of the heating block.

The inner diameter of the heating block 1 is slightly larger than the outer diameter of the parison A, and is configured to be heated by a heater 2 to generate radiant heat.

3 is a heat insulating material such as mica, which is inserted between the stacked heating blocks 1, 1, etc., and prevents the heat of adjacent heating blocks 1, 1 from being conducted to each other. There is.

In the heating furnace B, seven of the heating blocks 1 are placed on a metal bottom plate 5 in a predetermined shape with a heat insulating plate 4 placed thereon and the heater 2a is provided in the center, and the heat insulating material 3 is placed on each heating block 1,
1. Insert the parison insertion hole 6 in the center between...
The outer periphery is covered with a heat insulating cover 7 made of asbestos or the like.

In addition, each heating block 1, 1...
Six vertical holes 8 spanning the length are bored at regular intervals along the inner surface, and each of the vertical holes 8 is provided with a heater 9.

Each of the heaters 2, 2a, and 9 is equipped with a temperature controller, and the heating furnace B is heated by each heating block 1 by these heaters.
, 1... and the bottom plate 5 to heat the parison insertion hole 6 to a predetermined temperature, and if necessary, the temperature can be adjusted for each heater to change the temperature distribution inside the parison insertion hole. It is now possible.

Therefore, in the heating furnace B having the above configuration, since the parison insertion hole 6 is heated from the vertical direction and the horizontal direction, the heating of the parison A can be partially adjusted depending on the thickness distribution of the parison A. .

For example, when a part of parison A has thick shoulder meat in the longitudinal direction, the temperature of the vertical heater 9 at the position facing the shoulder meat is set lower than the temperature of the other vertical heaters, and each The temperature of the heaters 2 of the heating blocks 1, 1, . . . is maintained at a pre-adjusted temperature.

As a result, the heating of the shoulder meat part becomes lower than that of other parts, and the temperature distribution in the parison A also becomes lower in the shoulder meat part.

This temperature difference is reduced by the heat dissipation that occurs during elongation blowing when the parison A is sent from the heating furnace B to the blow mold, and thereby the influence of shoulder thickness on the hollow molded product is almost eliminated.

In other words, the temperature decreases faster in thin-walled parts due to heat radiation than in thicker-walled parts, and in a parison where the entire part is heated the same regardless of the wall thickness distribution, a temperature difference will already occur before it is stretched and blown. It is difficult to stretch-blow a hollow molded product with uniform wall thickness, but if you take into consideration the cooling of the parison due to heat radiation and heat it according to the wall thickness distribution, even if there is shoulder meat, it will not work. This is because the temperature of the parison in the stretch blow molded product is suitable for stretching and blow molding.

Therefore, according to this invention, it is possible to heat the parison by partially changing the temperature in the horizontal and vertical directions.
Even if a parison has shoulder thickness, a hollow molded product with a uniform wall thickness can be stretch blow molded without being affected by the shoulder thickness.

In addition, since partial heating can be performed in the vertical direction, it is convenient for forming flat containers, and vertical holes can be formed by simply penetrating each heating block and stacking the holes together. Since it is simple, the structure does not become particularly complicated, and it has the advantage that it is easy to partially adjust each heater.

[Brief explanation of the drawing]

The drawings show an embodiment of this invention; FIG. 1 is a longitudinal side view during heating of the parison, and FIG. 2 is a cross-sectional plan view. 1... Heating block, 2, 2 a...
Heater, 3...Insulation material, 5...Bottom plate, 6...Parison insertion hole, 8...Vertical hole, 9...Heater , A...Parison,
B... Heating furnace.

Claims (1)

[Scope of utility model registration request] Heaters are placed concentrically on a donut-shaped metal heating body to form a heating block, and the required number of heating blocks are stacked on a metal bottom plate with a heater with insulation material sandwiched between them so that the temperature can be adjusted individually. to form one cylindrical body having a parison insertion hole, and a plurality of vertical holes extending through each heating block are bored at regular intervals in the cylindrical body,
A parison heating furnace is equipped with a heater installed in the vertical hole to heat the parison in the longitudinal direction.