DE-112024002840-T5 - THERMOFORMING DEVICE

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Abstract

This thermoforming device (100), which is used for performing compressed air or vacuum forming and in which a working chamber (50) is divided by a resin sheet structure (S) which is held in a state in which an upper chamber (101) and a lower chamber (102) are closed, thus forming an upper compartment (51) in the upper chamber (101) and a lower compartment (52) in the lower chamber (102), includes the following: a first main pipe path (121) which is connected to the upper compartment (51) to form an upper vacuum circuit (120); a first subordinate pipe path (122) in which the flow path narrows from the first main pipe path (121) and which branches off from the first main pipe path (121); a second main pipe path (131) which is connected to the lower compartment (52) and forms a lower vacuum circuit (130); and a second subordinate pipe path (132) in which the flow path narrows from the second main pipe path (131) and branches off from the second main pipe path (131).

Inventors

TAKAI SHOGO
KAWANO SHINGO
HIGASHIJIMA Norio
TAKEDA Tsubasa
TERAMOTO KAZUNORI

Assignees

ASANO LAB CO LTD

Dates

Publication Date: 20260507
Application Date: 20240729
Priority Date: 20230912

Claims (4)

A thermoforming device for performing pressure forming or vacuum forming, the device comprising: an upper container having a pressure-resistant property and opening downwards; a lower container having a pressure-resistant property and opening upwards; and heating means for heating a workpiece made of resin, which is held in a working space formed by the upper container and the lower container in a closed state, wherein the upper container and the lower container are connected to a vacuum circuit, characterized in that the workpiece clamped by the upper container and the lower container in the closed state divides the working space into an upper compartment in the upper chamber and a lower compartment in the lower chamber, an upper vacuum circuit connected to the upper compartment for regulating the internal pressure of the upper compartment includes a first main line and a first branch line with a flow path that is more restricted than the first main line, a lower vacuum circuit connected to the lower compartment for regulating the internal pressure of the lower compartment includes a second main line and a second branch line with a flow path that is more restricted than the second main line, when the workpiece is heated using the heating means, a flow rate is regulated by switching the flow paths from the first main line to the first branch line and from the second main line to the second branch line becomes.
Thermoforming device as in Claim 1 described, wherein the upper vacuum circuit comprises: a first main line valve for opening and closing the first main line; a first branch line valve for opening and closing the first branch line; and a first flow control valve used to restrict the flow path of the first branch line, the lower vacuum circuit comprising: a second main line valve for opening and closing the second main line; a second branch line valve for opening and closing the second branch line; and a second flow control valve used to restrict the flow path of the second branch line, and the device is configured to reduce the vacuum level of the upper compartment using the first main line and to reduce the vacuum level of the lower compartment using the second main line, and then to close the first main line valve and the second main line valve, after which the workpiece is heated by means of the heating medium while the first branch line valve and the second branch line valve are opened and closed to control a flow rate in the upper vacuum circuit and a flow rate in the lower vacuum circuit.
Thermoforming device as in Claim 2 described, comprising: a first vacuum gauge in the upper compartment or first main line for measuring the degree of vacuum; and a second vacuum gauge in the lower compartment or second main line for measuring the degree of vacuum, wherein the first main line valve or the second main line valve is controlled to open and close by using the degree of vacuum of the upper compartment or the lower compartment, as measured by the first vacuum gauge or the second vacuum gauge.
Thermoforming device as in Claim 2 described, wherein a first vacuum pump is connected to the first main line to increase the vacuum level of the upper compartment, a second vacuum pump or the first vacuum pump is connected to the second main line to increase the vacuum level of the lower compartment, and a flow rate of air to be extracted through the upper vacuum circuit and a flow rate of air to be extracted through the lower vacuum circuit are regulated by opening and closing the first branch line valve and the second branch line valve.

Description

AREA OF INVENTION The present invention relates to a technique for controlling the internal pressure of a thermoforming device, specifically a technique for adjusting the degree of vacuum at a vacuum rise time of a thermoforming device of the type with an upper and a lower chamber. GENERAL STATE OF THE ART It is increasingly necessary for thermoforming equipment, widely used for food trays, packaging, and other applications, to achieve highly accurate forming or shaping. Furthermore, when formed products are used, for example, as vehicle dashboards, decorative films are sometimes applied to their surface to allow for printing and adding texture. In such cases, the labels for displays or gauges must be printed in specific positions. Consequently, there is a growing need for positional accuracy in the forming process. Patent document 1 discloses the technology relating to a vacuum forming machine. This vacuum forming machine is configured such that a forming chamber is hermetically sealed by a lower box opening upwards and an upper box opening downwards, and a decorative film is firmly applied to the surface of a substrate and shaped within the forming chamber. In this machine, the decorative film, clamped by the upper and lower boxes, thus dividing the forming chamber into an upper and a lower chamber, is brought into close contact with the substrate in a pressure setting step involving the creation of a high-pressure environment in the upper chamber and a low-pressure environment in the lower chamber. This technology prevents sagging of the decorative film, which can cause it to float, by stopping the heating process when a pressure differential is created between the forming chambers. DOCUMENTS ON RELATED TECHNOLOGY PATENT DOCUMENTS Patent document 1: Japanese unexamined patent application, publication no. 2015-107638 SUMMARY OF THE INVENTION PROBLEMS SOLVED BY THE INVENTION However, when products are thermoformed while the vacuum level is increased to enhance adhesion to the substrate, reaching the target vacuum level takes time. Therefore, to improve productivity, it is necessary to increase the vacuum extraction rate of a vacuum circuit. The applicant has confirmed, however, that such an increased rate results in unstable behavior of a resin sheet or film, which is the workpiece to be formed. The technology disclosed in patent document 1 does not address this defect and therefore could not remedy it. Depending on the thickness and material properties of the film or sheet and the heating temperature control, the film or sheet is generally prone to sagging during heating. In particular, when the vacuum level is increased to enhance adhesion to a substrate, the increased vacuum tends to cause significant sagging of the film. The applicant has confirmed through investigations that when a sheet or film is heated and softened, it not only sags (i.e., a sagging of the film's center) but also undergoes deformation affecting its forming process. In pressure forming or vacuum forming, when film forming is carried out using a forming tool and other equipment in a workspace formed by an upper and lower container in a closed state, a pressure differential is created between the upper and lower compartments, which are separated by the film at the time the vacuum level is increased. This causes the film to bulge (sag) towards the side with the lower pressure. Increasing the suction rate causes the vacuum level to overshoot (exceed a target range) in conjunction with the opening and closing of the valve. This causes the differential pressure between the upper and lower compartments to reverse, resulting in the film repeatedly moving up and down. This can lead to product defects, such as creases. The problems mentioned above could be solved by reducing the diameter of the pipes to sufficiently slow the extraction rate. However, such a configuration would reduce productivity. Therefore, the present invention aims to provide a thermoforming device to provide a system capable of increasing productivity while suppressing the behavior of a flat structure or film. MEANS TO SOLVE THE PROBLEMS To achieve the above-mentioned goal, one aspect of the present invention provides the following configurations. (1) A thermoforming device for carrying out pressure forming or vacuum forming, the device comprising: an upper container having a pressure-resistant property and opening downwards; a lower container having a pressure-resistant property and opening upwards; and heating medium for heating a workpiece made of resin, which is held in a working space formed by the upper container and the lower container in a closed state, wherein the upper container and the lower container are connected by a vacuum circuit, is characterized in that the workpiece clamped by the upper container and the lower container in the closed state divides the working space into an upper compartment in the upper chamber and a lower compartment in the lower chamb