JPS5869020A - Method of heating molded item to be reformed into biaxially stretched bottle - Google Patents

Abstract

PURPOSE:To heat uniformly and precisely a molded item, by heating the molded item to be blow molded by the radiation heat from a plurality of heaters arranged side by side while the molded item is positioned horizontally and is being rotated about its axis. CONSTITUTION:When the cylindrical molded item (P) that has a bottom and is to be blow molded should be heated by the radiation heat of heaters, the molded item (P) is positioned horizontally and while the molded item (P) is being rotated about its axis, it is heated by the radiation heat of the plurality heaters H1-H7 arranged side by side so that interference of heat may not be caused which would be otherwise caused by the convection of heat due to heaters arranged oppositely above and below the molded item (P). In this method, the molded item (P) is heated uniformly as a whole, so that thickness deviation would not occur in the biaxially orientated and blow molded item. Furthermore, as there is no interference of heat, the control of the heaters (H) can be facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for heating a primary molded product for biaxial stretching molding, and more specifically, uniform heating of the primary molded product can be easily and accurately achieved. It is intended to.

A primary molded product (hereinafter simply referred to as a piece) made of synthetic resin and has a cylindrical shape with a bottom is reheated to a temperature that produces a stretching effect, and this piece is biaxially stretched and blow molded. Increased body mass is formed.

Its mechanical strength, durability, and price make it suitable for use in a wide variety of fields.

As mentioned above, in this biaxial stretching molding facility, the injection molded piece is reheated to a temperature at which a stretching effect is produced, and then biaxially stretching is performed. When heating up to a certain temperature, it is necessary to heat the entire piece to as uniform a temperature as possible.

If the heating of this piece becomes partially uneven and a temperature difference occurs locally, thinning will occur in the added body that is biaxially stretch-produced from this piece. That's it.

Conventionally, heating this piece to a temperature that produces a stretching effect is achieved by arranging a plurality of heaters (1) vertically in parallel in a heating furnace along the moving path Kff3 of the piece P, as shown in Fig. 1. , the piece P held in an upright position is centered around its central axis P.
A method has been adopted in which the peace zone is moved while rotating around the peace zone, and heated by radiant heat from a plurality of heaters H1, H2, . . . arranged on the sides of the peace zone.

5 busy, each heater Ml, H1! -... Since they are arranged in parallel vertically, each heater H1, H2...
When operated with the same calorific value, each heater H1, H2...
・Thermal interference due to thermal convection occurs between the heaters H1 and H.
2... The thermal energy radiated from piece PK is not the same.

Therefore, k, which sets the calorific value of each heater H1, 12,... )12...The thermal interference that occurs should be known in advance, and based on this measured value, the amount of heat generated by each heater El, H2, etc. should be set, for example, as shown in the diagram in Figure 1. did not become.

However, it is extremely difficult to accurately know the thermal interference described above, even though the heating furnace has nine thresholds that are blocked. Since it takes a considerable amount of time for the temperature to settle down to a steady state, the time that the heating furnace operates to heat the piece P has to be short compared to the driving time of the heating furnace.

The most basic inconvenience is that each heater Ml, 11! Even if you set the calorific value for...
Because the thermal interference itself changes slightly under the influence of the moving movement of the piece P, and because this change in thermal interference cannot occur on the child side, the
It is simply impossible to heat the entire area uniformly.

Therefore, conventionally, the piece P is heated to near the upper limit of the temperature range in which the stretching effect occurs, and even if a temperature difference occurs between parts of the piece P, the ratio of that temperature difference to the actual heating temperature is small. Therefore, they tried to avoid any negative effects on stretch forming as much as possible.

The present invention was devised to eliminate the inconveniences and shortcomings of the above-mentioned conventional examples, and it is possible to uniformly heat a piece by preventing thermal interference due to thermal convection between multiple heaters arranged in parallel. That is.

The present invention will be explained below with reference to the drawings.

The method of heating a piece P according to the present invention is to place a piece P that rotates around one central axis Pi in a sideways position and moves in a heating furnace, so that the piece P faces the outer circumferential surface of the piece P and heat convection occurs between them. Radiant heating is performed by heaters Ml, H2, etc., which are arranged in parallel so that there is no vertical relationship that would cause thermal interference.

In other words, the most basic configuration in which the first invention is implemented is the third one.
As shown in Figure 1, a plurality of heaters Ml, H2, etc., extending in the direction of movement of the piece P, are placed directly below the piece P, which is rotating while lying on its side, parallel to the central axis P1 of the piece P. They are arranged in parallel on a horizontal plane.

Since each heater IN, H2, etc. are arranged in parallel on a horizontal plane, each heater H is not subject to thermal interference due to thermal convection from other heaters H, and therefore the amount of heat generated by each heater is a preset value for each heater (2), that is, an accurate value according to the electric power given to each heater HVC.

In this way, each heater H can accurately generate heat with a preset amount of heat.

Each heater 1111 is responsible for uniformly heating the entire piece P.
The amount of heat generated by °H2... may be set in accordance with the distance to the opposing part 72.

For example, in the case of the third tooth illustrated embodiment, the opposing f of each heater H
The cylindrical wall part of Bee Each of the heaters H1, H2, .

The amount of heat radiated from a unit heat source to any object is.

Since it is almost inversely proportional to the square of the distance between the heat source and the object, if the heat generation amount of each heater (■) is set to a value proportional to the square of the distance from the opposing part of the piece P, then The entire piece P is heated to a uniform temperature.

Of course, as shown in FIG. 2a, each heater H1.

H2... are arranged in parallel on a plane parallel to the plane in contact with the outer peripheral surface of the cylindrical wall of piece P, each heater H1, H
! Since the distances between the opposing parts of the heaters H1, H2, and so on are all equal, it is sufficient for each heater H1, H2, and so on to generate heat with the same amount of heat.

However, as shown in FIG. 2a, when the heaters (2) are placed in parallel on an inclined surface, there will be a slight vertical relationship between Fi and each heater H.

This vertical relationship between each heater H causes thermal interference due to thermal convection, but if each heater H is distributed in parallel with intervals and the vertical relationship is an extremely small value, each heater H Since there is no thermal interference caused by thermal convection between the heaters 8, there is no possibility that thermal interference due to thermal convection will occur between the heaters 8 if the vertical relationship between the heaters H as shown in FIG.

Furthermore, if the relationship between the heater H and the piece P shown in FIG. The structure of a heating furnace that maintains the relationship between the heater H and the piece P is arranged in parallel on a horizontal plane as shown in FIG.

The piece P may be held with the central axis P1 inclined so that the plane in contact with the outer circumferential surface of the piece P is a horizontal plane.

Furthermore, as is clear from the above explanation, theoretically,
If the positional relationship between the heaters H1, H2... and the piece P is as shown in Fig. 2, the amount of heat generated by the heaters I'll, H2... may be the same, but in reality, the heat output from the heaters I'll, H2... may be the same. When heating is operated in a heating furnace that forms a space.

The heat loss is large on the opening side of the piece P, where the jig that holds and moves the piece P is located, and the bottom side of the piece P is a completely closed space, so there is less heat loss, and the ambient temperature is accordingly lower. Each heater 11,1! !
As shown in Figure 2, the set temperature of the heater H1 facing the opening of the piece P is highest, gradually decreases as it approaches the bottom of the piece P, and the set temperature of the heater H7 facing the bottom of the piece P is the highest. is set to the lowest value, and the entire fs-space P is evenly heated.

In addition, each heater does not have to be placed directly under the piece P; in some cases, the piece P
They may be arranged in parallel on the sides.

However, in this case, not only does the structure of the holding jig for the piece P become complicated and complicated, but also a large number of short heaters H must be used, and the electrical connection becomes complicated. Therefore, it is disadvantageous from a structural point of view.

As is clear from the above explanation, in #5 the present invention
Since thermal interference due to thermal convection between the two heaters is prevented, each heater (■) can heat the bea with the set amount of heat, and since the amount of heat generated by each heater (H) can be simply set, the piece P Not only can the whole be heated uniformly, but the heating temperature of the piece P can be easily and accurately controlled, and the posture of the half-wax piece P and the heater H can be easily and accurately controlled.
It has many excellent functions and effects, such as being able to be easily installed in an already manufactured heating furnace by simply changing its position.

[Brief explanation of drawings]

Figure 1 shows a conventional piece heating method. Figure 1a shows the arrangement of each heater with respect to the piece. FIG. 1 shows the set temperature of each heater. FIG. 2A shows an embodiment of the present invention, and FIG. 2a shows the arrangement of heaters with respect to the piece, and fs2 shows the relationship between the set temperatures of each heater. FIG. 3 shows the arrangement of heaters for the basic pieces of the method of the present invention. Explanation of symbols P...Primary molded product (piece), a, at, a2, mountain...Heater j PI...Center axis. Inventor: Hiroshi Uekusa Inventor: Akira Onodera - Applicant: Yoshino Kogyo Co., Ltd. User: Yata Yoshino 2 Recommendations: 7 (a) (b) T ('C) Gudo Z4

Claims (1)

[Claims] Biaxially Stretched Bulb I - A method of radiant heating using a heater for a primary molded product in the shape of a cylinder with a bottom for molding a synthetic resin bottle, in which the product is rotated around the central axis in a horizontal copper position. The primary molded product is radiantly heated by a plurality of heaters arranged in parallel to face the outer peripheral surface of the #1 primary molded product so as not to have a vertical relationship that would cause thermal interference due to thermal convection between them. A method for heating a primary formed crystal for forming a biaxially stretched forming field body.