JPH04308703A - Sheetlike thermoplastic resin material molding device - Google Patents

Abstract

PURPOSE:To prevent generation of a drawdown phenomenon and effect a uniform heating of a resin material, by a method wherein a heating part heating a sheetlike thermoplastic resin material into a plasticized state is constituted of a heat-resistant endless belt conveying the resin material at fixed speed turning and a heating device. CONSTITUTION:A sheetlike thermoplastic resin material 1 drawn out through a wind-around roll 6A is preheated by a preheating plate 2 through a plurality of holding and conveying rollers 8 and tension rollers and then conveyed on a circumferential surface of a tuning drum 9. The turning drum 9 is formed into a hollow form where one side is open, a resin material 1' which is conveyed on the circumferential surface of the turning drum 9 is heated by a heating source 11 on an inner circumferential side of the tuning drum 9 at its lower part and heated by a heating source 12 at the upper part. A conveyor belt 14 laid by stretching over rollers 14A-14E is arranged between those heat sources 11, 12 and the resin material 1' is placed and held between the conveyor belt 14 and the circumferential surface of the turning drum 9, through which a deformation of the resin material 1 at the time of heating is prevented.

Description

[Detailed description of the invention]

[Field of Industrial Application] This invention relates to an apparatus for molding thermoplastic resin materials such as so-called plastics. This invention relates to improvements in heating devices for materials.

[Prior Art] Figure 1 schematically shows a molding apparatus for molding thermoplastic resin materials. There is a tendency for molding equipment to be used. In FIG. 1, 1 indicates a sheet-like thermoplastic material, which is a material to be formed, having a thickness of, for example, about 0.15 to 1.00 mm, and the sheet-like thermoplastic resin material 1 is fed out from a wound roll 6A. Then, it is stretched over tension rollers 7 and transport rollers 8 and transported in the direction of arrow M. When the sheet-like thermoplastic resin material 1 is transferred in the direction of arrow M, it is subjected to preheating treatment by a preheating plate 2, heat treatment by a heating device 3, molding processing by a molding device 4, and product cutting die treatment by a press device 5. be done. The preheating treatment of the preheating plate 2 is performed as a pretreatment of the heating treatment in the heating device 3, and the sheet-shaped thermoplastic resin material 1 is subjected to a heat treatment at a relatively low temperature.
The heat source temperature used is, for example, 100°C. The heating device 3 heats the sheet-like thermoplastic resin material 1 to a plastic state (for example, 120°C), and the heat source temperature is set to, for example, 300°C. This heating device 3 is equipped so that its installation position in the vertical direction can be adjusted, and by this vertical adjustment, it is possible to adjust the heating of the sheet-shaped thermoplastic resin material. The molding device 4 is a device that molds the sheet-like thermoplastic resin material 1, which is in a plastic state as a result of the heating, into a desired shape to process the molded product 1A, and uses, for example, a vacuum molding method. During molding, the molding device 4 descends onto the sheet-like thermoplastic resin material, presses the sheet-like thermoplastic resin material 1 between the lower mold and the upper mold, and molds the molded product 1A. The press device 5 performs a cutting die process 5A in which the molded product after the above molding process is separated from the sheet-like thermoplastic resin material 1 while repeating an up-and-down operation. Various known methods can be used for this method, for example, a method called Thomson press is used. The sheet-like thermoplastic resin agent 1 after being subjected to the punching process in the press device 5 is called a punched dregs, and is wound up on a winding drum 6B called a punched dregs drum. The above molding processing apparatus is an extremely effective technique as a mass production processing apparatus for sheet-shaped thermoplastic resin materials such as so-called plastic materials. However, a problem with the conventional device described above is that a drawdown phenomenon occurs during the heating process. The drawdown phenomenon, as shown in FIG. 2, is a phenomenon in which, when the sheet-like thermoplastic resin material 1 is heated to a plastic state in the heating process, a sagging portion 1DW is generated due to its own weight. This is because the crystalline plastic material is heated,
This phenomenon occurs due to rapid thermal deformation near the melting point of the crystal. In the molding process, in order to process a product with uniform quality, it is required that the sheet thickness of the sheet-shaped thermoplastic material that is the workpiece is uniform. However, the drawdown phenomenon induces changes in sheet thickness that exceed acceptable limits, resulting in defective products. The sheet-like thermoplastic resin material to be molded has extremely small concave portions called pinholes (0.05 m in diameter) on its surface.
m), and it is said that the occurrence of these pinholes to some extent is unavoidable in the production of sheet-like thermoplastic resin materials. When a drawdown phenomenon occurs in the sheet-like thermoplastic resin material during the plastic heating, an expansion phenomenon of the pinhole portion occurs due to the tension acting on the periphery of the pinhole. When the wall thickness of the expanded portion becomes thinner as a result of the expansion of the pinhole portion, the heating effect of the thinned portion is emphasized, and further tension acts to promote thinning. At the same time, in the peripheral area of the pinhole expansion, the sheet material drawn from the thin part of the pinhole part is stacked, so that a thickening phenomenon occurs, contrary to the thin part. As a result of the above, the drawdown phenomenon causes non-uniformity in the sheet thickness of the sheet-shaped thermoplastic material, and as a result, breaks occur at the corners of the molded product during molding, making it inevitable to produce defective products. do. Furthermore, another problem with the above-mentioned conventional device is that the heating device 3 is
As shown in Figure 2, it must be installed at a position lower than the hanging part 1DW of the sheet-shaped thermoplastic resin material, which poses the problem of making it difficult to uniformly heat the surface of the sheet-shaped thermoplastic resin material. It is. Non-uniform heating of the sheet-like thermoplastic resin material causes problems such as deteriorating the molding effect during molding, inducing non-uniformity in product quality, and further reducing productivity. As a method to prevent the above-mentioned problem, conventionally, methods have been considered in which the sheet-shaped thermoplastic resin material is heated at a temperature lower than the plastic state, such as solid phase pressure forming method or vacuum forming method after stretching. ing. However, all of these methods have drawbacks such as high raw material costs and complication of molds and molding equipment, resulting in inevitably high product costs.

[Problems to be Solved by the Invention] The present invention aims to prevent the above-mentioned drawdown phenomenon from occurring when a sheet-like thermoplastic resin material is heated to a plastic state, thereby improving vacuum forming using conventional relatively inexpensive resin materials. Furthermore, by installing a heating device in close proximity, the sheet-shaped thermoplastic resin material can be heated uniformly, thereby eliminating the occurrence of defective products and making it possible to mass-produce resin molded products at low cost. It's something to do.

[Means for Solving the Problem] As a means for solving the problem, a heating section that heats a sheet-like thermoplastic resin material to a plastic state and a molding section that molds the sheet-like thermoplastic resin material after heating are provided. In the apparatus for molding a sheet-like thermoplastic resin material, the heating section includes a heat-resistant endless belt that conveys the sheet-like thermoplastic resin material by rotating at a constant speed, and the sheet that is conveyed on the heat-resistant endless belt. A heating means is provided for heating the shaped thermoplastic resin material to a plastic state.

[Operation] In the above, the heating section is constituted by an endless belt that rotates at a constant speed, and the sheet-like thermoplastic resin material is conveyed on this endless belt as the endless belt rotates at a constant speed. Although the sheet-like thermoplastic resin material is heated to a plastic state by a heating device during conveyance, since the sheet-like thermoplastic resin material is held by the endless band, the occurrence of a drawdown phenomenon is prevented.

[Embodiment] FIG. 3 shows a side view of an embodiment of the present invention, in which a sheet-like thermoplastic resin material 1 fed out from a winding roll 6A is passed through a plurality of conveyance rollers 8 and a tension roller 7, (FIG. 1), it is transferred to the preheating section of the preheating plate 2. Reference numeral 9 denotes a rotating drum, on which the sheet-shaped thermoplastic resin material 1' that has passed through the preheating plate 2 is conveyed. The rotating drum 9 has a drum circumferential surface having a width at least equal to or larger than the sheet width of the sheet-like thermoplastic resin material 1, and the drum circumferential surface is made of a heat-resistant material such as Teflon material, and is heated to a plastic state. This prevents the sheet-like thermoplastic resin material from being fused to its surface. Further, as shown in an axial cross-sectional view in FIG. 4, the rotating drum 9 is formed in a U-shape with an opening on one side of the drum, and a rotating shaft 10 provided on the side opposite to the opening 9A is mounted on a bearing. 10A, and is rotated by transmitting the rotational force from the rotating device 10B (electric motor). Further, the rotary drum 9 rotates with its lower open end supported by a freely rotating mechanism such as a roller 10C, and as the rotary drum 9 rotates, the sheet-like thermoplastic resin material 1' that has passed through the preheating plate 2 rotates. It is conveyed on the circumferential surface of the drum 9 and transferred to the molding device 4. Reference numeral 11 denotes a heating source, which heats the sheet-like thermoplastic resin material 1' from the lower part of the conveyance path of the sheet-like thermoplastic resin material 1' conveyed on the circumferential surface of the rotary drum 9 via the rotary drum 9. The heating source 11 is fixed outside the rotating drum 9 and is connected to the opening 9A of the drum 9.
The support arm 11A extends from the support arm 11A into the drum. The support arm 11A is arranged at a position close to the lower part of the conveyance path of the sheet-like thermoplastic resin material 1' on the circumferential surface of the rotating drum. Reference numeral 12 denotes a heating source similar to 11, and is placed close to the conveying path of the sheet-shaped thermoplastic resin material 1' on the circumferential surface of the rotating drum 9. The heat sources 11 and 12 apply plastic heating to the sheet-like thermoplastic resin material 1' conveyed on the circumferential surface of the rotary drum from inside and outside of the rotary drum 9, similarly to the heat source 3 in FIG. conduct. Reference numeral 14 indicates a conveyor belt, which is stretched around rollers 14A to 14E. and roller 14
Of the rollers A to 14E, rollers 14B and 14C are pressed in the direction of the conveyance path of the sheet-like thermoplastic resin material of the rotating drum 9, and the conveyor belt 1 is stretched across the rollers 14B and 14C.
By sandwiching and conveying the sheet-like thermoplastic resin material between the circumferential surfaces of the rotary drum 4 and the rotating drum 9, deformation of the sheet-like thermoplastic resin material 1 is prevented at the time of overheating. In addition, in the above, the heating sources 11 and 12 can be made of various materials, and for example, a known material called a ceramic heater can also be used. Further, the arrangement structure of the heating sources 11 and 12 can be changed as appropriate, and the material is not limited to a planar shape, but may be arranged using a material having a curved surface shape. Further, the heating source is not limited to the above-mentioned heating element, but may also be a heating means such as jetted hot air, or an oil heater that circulates heated oil. The hot air jetting means may be configured, for example, by forming the circumferential surface of the rotating drum into a net shape using a heat-resistant material such as Teflon material, and jetting hot air from the lower part of the sheet-shaped thermoplastic resin material conveying path inside the rotating drum 9. Good too. In this way, the sheet-shaped thermoplastic resin material is heated plastically by the hot air jet, and at the same time,
By conveying the material while slightly floating above the circumferential surface of the rotating drum, the drawdown phenomenon can be prevented. Various methods are possible for installing hot air injection equipment, but
For example, in FIG. 4, an injection nozzle may be installed instead of the heating source 11. Alternatively, the opening 9A of the rotating drum 9 may be sealed and high-pressure hot air may be injected into the rotating drum 9 so that the hot air is blown out from the circumferential surface of the rotating drum. The hot air can be injected into the rotating drum 9, for example, through a hollow portion of a rotating shaft having a hollow interior. For example, a rotary mechanism called a rotary joint is known as the hollow rotating shaft. In addition, heating by the oil heater method is performed by making the entire circumferential surface and side surface of the rotating drum 9 a sealed structure, and injecting heated oil into the rotating drum from a known hollow rotating shaft mechanism such as a rotary joint. A circumferential sheet-shaped thermoplastic resin material is heated. In this case, the circumferential surface of the rotating drum is coated with a heat-resistant non-fusing material such as Teflon material in order to prevent the sheet-like thermoplastic resin material heated into a plastic state from fusing to the drum circumferential surface. be done. The sheet-shaped thermoplastic resin material is heated continuously by circulating heating oil. Circulation of the heated oil is possible by injecting the heated oil from one of the hollow rotating shafts provided on both rotating sides of the rotating drum 9, and discharging the heated oil from the other rotating shaft. Note that for heating and circulating the heated oil, any known means can be adopted as appropriate. FIG. 5 is a side view of another embodiment, showing an embodiment in which a so-called caterpillar is used as the conveyance means in place of the rotary drum 9. The conveyor material 52 constituting the caterpillar is connected at its center by a connecting tool 53, and is connected to a pair of tension carriers 5.
It is stretched between 1A and 51B. The arms 54 of each conveyance material 52 extending in the chain direction are assembled with each other to form a conveyance path plane for the sheet-like thermoplastic resin material 1 . Reference numeral 55 denotes a heating device, which is installed close to the caterpillar conveyor 52 and heats the sheet-like thermoplastic resin material conveyed by the caterpillar conveyor 52 until it becomes plastic.

As described above, the present invention performs plastic heating while holding and conveying a sheet-like thermoplastic resin material on a rotating endless band. Therefore, it is possible to plastically heat the sheet-shaped thermoplastic resin material without causing a drawdown phenomenon, so it is possible to create a practical and economical molding device without making any changes to conventionally used molding equipment. A widely used vacuum forming method can be used. Furthermore, it is now possible to use conventional relatively inexpensive resin materials as the molding material, making low-cost mass production molding possible. Furthermore, since the sheet-shaped thermoplastic resin material is always conveyed along a constant conveyance path by the endless belt, it is possible to place the heating device as close to the conveyance path as possible, allowing for high accuracy in the heating state of the sheet-shaped thermoplastic resin material. Uniform heating is possible through adjustment. Therefore, uniform plastic heating of the sheet-like thermoplastic resin material becomes possible, and mass production of molded products of uniform quality becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of a sheet-shaped thermoplastic resin material molding apparatus.

FIG. 2 is a diagram for explaining a conventional device.

FIG. 3: Example of this invention.

FIG. 4 is a diagram for explaining the rotating drum structure in FIG. 3.

FIG. 5 Other examples.

Claims (3)

[Claims] 1. A molding apparatus for a sheet thermoplastic resin material, which is provided with a heating section that heats the sheet thermoplastic resin material to a plastic state, and a molding section that molds the heated sheet thermoplastic resin material, The heating section includes a heat-resistant endless belt that conveys the sheet-like thermoplastic resin material by rotating at a constant speed, and heating that heats the sheet-like thermoplastic resin material conveyed on the heat-resistant endless belt to a plastic state. A sheet-like thermoplastic resin material molding apparatus comprising means. [Claim 2] A molding apparatus for a sheet thermoplastic resin material, which is provided with a heating section that heats the sheet thermoplastic resin material to a plastic state, and a molding section that molds the heated sheet thermoplastic resin material, The heating section includes a rotating drum body that transfers the sheet-shaped thermoplastic resin material while rotating at a constant speed, and the sheet-shaped heat that is provided inside and outside of the rotating drum body and that transfers the sheet-shaped thermoplastic resin material on the circumferential surface of the rotating drum. A sheet-shaped thermoplastic resin material forming apparatus comprising heating means for heating a plastic resin material to a plastic state. 3. A molding apparatus for a sheet thermoplastic resin material, which is provided with a heating section that heats the sheet thermoplastic resin material to a plastic state, and a molding section that molds the heated sheet thermoplastic resin material, The heating section includes a rotating drum body that transfers the sheet-like thermoplastic resin material while rotating at a constant speed, and a hollow rotating shaft of the rotating drum that circulates high-temperature oil into the rotating drum. A sheet-like thermoplastic resin material forming apparatus comprising: high-temperature oil circulation means for heating the sheet-like thermoplastic resin material transferred on the circumferential surface of a rotating drum.