Thermoforming apparatus

Abstract

To provide a thermoforming apparatus capable of enhancing productivity while suppressing behavior of a sheet or a film.SOLUTION: In a thermoforming apparatus 100 which performs air pressure forming or vacuum forming, an upper room 51 is formed in an upper chamber 101 and a lower room 52 is formed in a lower chamber 102 by separating a work space 50 by a resin sheet S held while the upper chamber 101 and the lower chamber 102 are closed. The thermoforming apparatus comprises: a first main piping path 121 connected to the upper room 51 so as to form an upper vacuum circuit 120; a first sub piping path 122 having a reduced flow path than the first main piping path 121 and provided branched from the first main piping path 121; a second main piping path 131 connected to the lower room 52 so as to form a lower vacuum circuit 130; and a second sub piping path 132 having a reduced flow path than the second main piping path 131 and provided branched from the second main piping path 131.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for controlling the pressure inside a thermoforming device, and more particularly to a technique for adjusting the degree of vacuum at the start of vacuum build-up in a top and bottom chamber type thermoforming machine. [Background technology]

[0002] Thermoforming machines are now used in a wide range of fields, such as food trays and packages, and there are an increasing number of cases where higher precision molding is required. In addition, when molded products are used in car dashboards, there are cases where the texture is created by painting the molded product using decorative film on the surface, and there are also cases where device markings are required to be displayed in a specified position. Therefore, there are also increasing cases where positional precision is required in molding.

[0003] Patent Document 1 discloses a technology related to a vacuum forming machine. A lower box that opens upward and an upper box that opens downward form a molding space, and the vacuum forming machine forms a decorative film by adhering it to the surface of an adherend in the molding space. The decorative film is adhered to the adherend in a pressure adjustment process in which the upper molding space partitioned by the decorative film held by the upper and lower boxes is a pressurized environment and the lower molding space is a reduced pressure environment. This technology prevents sagging of the decorative film, which causes the decorative film to float, by stopping heating when a pressure difference is generated in the molding space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-107638 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the degree of vacuum is increased to increase the adhesion to the adherend during thermoforming of the product, it takes time to reach the target degree of vacuum. For this reason, it is necessary to increase the evacuation speed of the vacuum circuit to increase productivity, but the applicant has confirmed that this will cause the behavior of the resin sheet or film to be molded to become unstable. The technology described in Patent Document 1 does not mention such points, making it difficult to solve. In general, depending on the thickness of the film or sheet, the physical properties of the material, and the heating temperature control, drawdown is likely to occur when the film or sheet is heated. In particular, when the degree of vacuum is increased to increase the adhesion to the adherend, the influence of the drawdown of the film is likely to be significant.

[0006] As a result of the applicant's investigation, it has been confirmed that when a sheet or film is softened by heating, in addition to drawdown, in which the center of the film sags, deformations that affect molding can also occur. When forming a film using a mold or the like in a work space formed by preparing and closing an upper and lower container in pressure forming or vacuum forming, if a pressure difference occurs when increasing the vacuum level between the upper and lower chambers separated by the film, the side with the lower pressure will swell (sag). It was found that when the exhaust speed is increased, the vacuum level overshoots (exceeds the target range) as the valve opens and closes, causing the pressure difference to switch between the upper and lower chambers, causing the film to repeatedly move up and down. This can lead to defects such as wrinkles in the product.

[0007] Although this problem can be solved by narrowing the piping diameter to sufficiently slow down the exhaust speed, this would then result in a drop in productivity. Therefore, the object of the present invention is to provide a thermoforming device that can improve productivity while suppressing the behavior of the sheet or film. [Means for solving the problem]

[0008] In order to achieve the above object, a thermoforming apparatus according to one aspect of the present invention has the following features.

[0009] (1) A thermoforming device for performing pressure forming or vacuum forming, comprising: an upper container having pressure resistance and opening downward; a lower container having pressure resistance and opening upward; a vacuum circuit connected to the upper container and the lower container; and a heating means for heating a resin molded body while the resin molded body is held in a working space formed when the upper container and the lower container are closed, The work space is divided by the molded body held in a closed state between the upper container and the lower container, so that an upper chamber is formed on the upper container side and a lower chamber is formed on the lower container side, An upper vacuum circuit connected to the upper chamber for adjusting the pressure in the upper chamber includes: The system includes a first main piping line and a first sub-piping line whose flow path is narrowed from the first main piping line, a lower vacuum circuit connected to the lower chamber and adjusting the pressure in the lower chamber, a second main piping line and a second sub-piping line whose flow path is narrowed from the second main piping line; adjusting a flow rate by switching a flow path from the first main piping line to the first sub-piping line and from the second main piping line to the second sub-piping line, respectively, when the molding body is heated by the heating means; It is characterized by:

[0010] According to the aspect described in (1) above, the pressure adjustment of the upper chamber and the lower chamber is realized by switching between the first main piping line and the first sub-piping line in the upper vacuum circuit, and by switching between the second main piping line and the second sub-piping line in the lower vacuum circuit. Specifically, the flow rate of the first sub-piping line is narrower than that of the first main piping line, and the flow rate of the second sub-piping line is narrower than that of the second main piping line. This allows the pumping speed to be selected freely.

[0011] Considering the cycle time for manufacturing a molded product using a thermoforming device, the heating time or the time required to increase the degree of vacuum is high. However, if the pipe diameter of the first main pipe line and the second main pipe line are widened or the flow rate is increased to increase the exhaust speed, it becomes difficult to control the target vacuum level after it is reached, as mentioned in the problem section. Therefore, by preparing and switching between the first and second sub-pipe lines with reduced flow rates, it becomes easier to control the vacuum level. As a result, it is possible to achieve both the ease of control of the exhaust speed and the degree of vacuum, and by controlling the pressure difference between the upper and lower chambers to be small, it becomes possible to prevent the effects of the pressure difference, such as drawdown of the molded body, such as a film or sheet.

[0012] (2) In the thermoforming apparatus according to (1), The upper vacuum circuit includes: a first main piping valve for connecting / blocking the first main piping passage; a first sub-pipe valve for connecting / blocking the first sub-pipe; a first flow rate control valve used for the purpose of narrowing the flow path of the first sub-pipe; In the lower vacuum circuit, a second main piping valve for connecting / blocking the second main piping passage; a second sub-pipe valve for connecting / blocking the second sub-pipe; a second flow control valve used for the purpose of narrowing the flow path of the second sub-pipe; reducing the degree of vacuum in the upper chamber and the lower chamber using the first main piping line and the second main piping line, and then closing the first main piping valve and the second main piping valve, and thereafter heating the molded body by the heating means while adjusting the flow rate of the upper vacuum circuit and the flow rate of the lower vacuum circuit by opening and closing the first auxiliary piping valve and the second auxiliary piping valve; is preferred.

[0013] According to the aspect described in (2) above, the pressure adjustment of the upper and lower chambers is performed by adjusting the flow rate of air flowing in or out of the upper or lower chambers with either the first flow rate adjustment valve or the second flow rate adjustment valve, thereby making it possible to control the behavior of the resin molded body. It is easily affected by the pressure difference between the upper and lower chambers, or the flow velocity and flow rate. For this reason, for example, when the air discharged from the first main circuit connected to the upper chamber is throttled by the first flow rate adjustment valve and the lower chamber side is controlled for vacuum molding, the air discharged from the second main circuit connected to the lower chamber is throttled by the second flow rate adjustment valve, and the differential pressure is controlled to be small, thereby making it possible to prevent the influence of the differential pressure, such as drawdown of the molded body, such as a film or sheet. This makes it possible to reduce the occurrence rate of defects such as wrinkles or deformation in the molded product.

[0014] (3) In the thermoforming apparatus according to any one of (1) and (2), a first vacuum gauge for measuring a vacuum level is provided in the upper chamber or the first main piping line; A second vacuum gauge for measuring a vacuum degree is provided in the lower chamber or the second main piping line, using the vacuum degree of the upper chamber or the lower chamber obtained by the first vacuum gauge or the second vacuum gauge for controlling opening and closing of the first sub-piping valve or the second sub-piping valve; is preferred.

[0015] According to the aspect described in (3) above, by providing the first and second vacuum gauges and using their data as a trigger, it is possible to control the vacuum adjustment accurately. As a result, it is possible to start molding from a state where the pressure difference between the upper and lower chambers is suppressed and the bulging of the molded body is suppressed.

[0016] (4) A thermoforming apparatus according to any one of (1) to (3), A first vacuum pump for increasing the degree of vacuum in the upper chamber is connected to the first main piping line, A second vacuum pump or the first vacuum pump is connected to the second main piping line to increase the vacuum level in the lower chamber, adjusting a flow rate of air exhausted through the upper vacuum circuit and a flow rate of air exhausted through the lower vacuum circuit by opening and closing the first sub-piping valve and the second sub-piping valve; is preferred.

[0017] According to the embodiment described in (4) above, the behavior of the film or sheet to be molded can be suppressed in the process of increasing the degree of vacuum in the upper and lower chambers. As a result, it is possible to suppress the occurrence of defects such as wrinkles and deformation in the molded product. As shown in the problem, if a pressure difference occurs when the degree of vacuum in the upper and lower chambers is increased, the molded product will expand to either the top or bottom, and it has been confirmed that the molded product will move up and down when the pressure balance is reversed. This phenomenon is more pronounced when the vacuum exhaust speed of the vacuum circuit is increased to increase productivity, and if this expansion of the molded product (drawdown, etc.) occurs, the molded product will unintentionally adhere to the mold surface, which will result in a defective molded product. To solve these problems, molding is performed while controlling the pressure difference between the upper and lower chambers so that it is less likely to occur.

[0018] Specifically, after the first vacuum pump and the second vacuum pump are used to reduce the pressure to a predetermined level, the first main piping valve provided on the first main piping line and the second main piping valve provided on the second main piping line are closed, and the flow rates of the first and second sub-piping lines are adjusted by the first and second flow control valves, and the first and second sub-piping valves are opened and closed to control the vacuum level and reach the target vacuum level. By performing such control, it becomes possible to start molding in a state where the pressure difference between the upper and lower chambers is suppressed and swelling of the molded body is suppressed.

[0019] As a result, it is possible to increase the evacuation speed by using the first main piping line and the second main piping line, while finely adjusting the vacuum level at a high vacuum level, which means that a molding cycle time can be improved and a molded product with high precision can be obtained. In this case, the same effect can be obtained by providing only the first vacuum pump and controlling the first flow rate control valve, the second flow rate control valve, the first sub-piping valve, and the second sub-piping valve. When a second vacuum pump is provided in addition to the first vacuum pump, fine control is achieved by controlling each vacuum pump. However, when the capacities of the upper and lower chambers are small and complex control is not required, a configuration in which only the first vacuum pump is selectively used can be used to optimize costs. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a thermoforming device according to a first embodiment. [Diagram 2] 4 is a time chart before molding in the first embodiment. [Diagram 3] FIG. 2 is an explanatory diagram illustrating a schematic configuration of the thermoforming device in the first embodiment at the stage of starting to heat the resin sheet. [Figure 4] FIG. 2 is an explanatory diagram illustrating a schematic configuration of the thermoforming device in the first embodiment with a vacuum circuit switched. [Diagram 5] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a thermoforming device according to a conventional technique prepared for comparison. [Figure 6] FIG. 11 is an explanatory diagram illustrating a schematic configuration of a thermoforming device according to a second embodiment. [Figure 7] FIG. 11 is an explanatory diagram illustrating a schematic configuration of a thermoforming device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] (First embodiment) First, an outline of the configuration of a thermoforming apparatus 100 according to a first embodiment of the present invention will be described. Fig. 1 is an explanatory diagram illustrating the outline of the configuration of the thermoforming apparatus 100 according to the first embodiment. The thermoforming apparatus 100 holds a resin sheet S between an upper chamber (upper container) 101 and a lower chamber (lower container) 102, and performs molding using a mold 150 while heating the resin sheet S with heating means 110 that can be raised and lowered, such as a radiant heating device.

[0022] The resin sheet S corresponding to the molded body is an ABS sheet material made of a thermoplastic resin having a thickness of about 500 μm. According to the JIS standard, a sheet is defined as a plate-like material having a thickness of 250 μm or more, and a film is defined as a membrane-like material having a thickness of less than 250 μm, but this does not prevent the present invention from being applied to a film. In addition, the material of the resin sheet S is not limited to ABS, and resins such as polypropylene can be appropriately selected as necessary.

[0023] An upper vacuum circuit 120 is connected to the upper chamber 101. The upper vacuum circuit 120 includes a first main piping line 121 connected to the upper chamber 101, and a first sub-piping line 122 provided in parallel. A first main piping valve 123 is provided in the first main piping line 121, and the first main piping valve 123 is opened and closed to connect and disconnect the first main piping line 121. A first sub-piping valve 124 and a first flow rate control valve 125 are provided in the first sub-piping line 122, and the first sub-piping valve 124 is opened and closed to connect and disconnect the first sub-piping line 122, and the flow rate of the first sub-piping line 122 can be adjusted by opening and closing the first sub-piping valve 124, and adjusting the opening degree of the first flow rate control valve 125.

[0024] The first sub-piping path 122 is designed to branch off between the upper chamber 101 of the first main piping path 121 and the first main piping valve 123, and merge between the first main piping valve 123 and the first vacuum pump 126. Therefore, when the first vacuum pump 126 connected to the upper vacuum circuit 120 is operated to exhaust air, the first sub-piping path 122 can be used to exhaust air with the flow rate adjusted. Here, the first main piping valve 123 and the first sub-piping valve 124 are so-called vacuum valves that are used in the vacuum circuit and have the function of connecting / disconnecting the circuit. Also, the first flow rate adjustment valve 125 is an adjustment valve that can be used in the vacuum circuit to adjust the flow rate.

[0025] A lower vacuum circuit 130 is connected to the lower chamber 102. The lower vacuum circuit 130 includes a second main piping path 131 connected to the lower chamber 102, and a second sub-piping path 132 provided in parallel. A second main piping valve 133 is provided in the second main piping path 131, and the second main piping path 131 is opened and closed by opening and closing the second main piping valve 133. A second sub-piping valve 134 and a second flow rate control valve 135 are provided in the second sub-piping path 132, and the second sub-piping path 132 is opened and closed by opening and closing the second sub-piping valve 134, and the flow rate of the second sub-piping path 132 can be adjusted by adjusting the opening degree of the second flow rate control valve 135.

[0026] The second sub-pipe 132 is designed to branch off between the lower chamber 102 of the second main pipe 131 and the second main pipe valve 133, and to merge between the second main pipe valve 133 and the second vacuum pump 136. Therefore, when the second vacuum pump 136 connected to the lower vacuum circuit 130 is operated to increase the degree of vacuum, the second sub-pipe 132 can be used to perform evacuation with flow rate adjustment. Here, the second main pipe valve 133 and the second sub-pipe valve 134 are so-called vacuum valves, which are used in the vacuum circuit and have the function of connecting / disconnecting the circuit. The second flow rate adjustment valve 135 is an adjustment valve that can be used in the vacuum circuit to adjust the flow rate.

[0027] The first flow rate control valve 125 is adjusted so that the flow rate of the first sub-pipe line 122 is, for example, about 1 / 10 to 1 / 20 of that of the first main piping line 121. The second flow rate control valve 135 is similarly adjusted so that the flow rate of the second sub-pipe line 132 is, for example, about 1 / 10 to 1 / 20 of that of the second main piping line 131. The opening adjustments of the first flow rate control valve 125 and the second flow rate control valve 135 are preferably selected as appropriate depending on the physical properties of the resin sheet S, etc.

[0028] The upper chamber 101 and the lower chamber 102 are connected by a connecting pipe 140, and communication / disconnection is performed by opening and closing a connecting pipe valve 141. When the upper chamber 101 and the lower chamber 102 are closed, the inner space becomes a working space 50, and is divided into an upper chamber 51 and a lower chamber 52 by a resin sheet S. Therefore, when the upper chamber 51 and the lower chamber 52 are in communication with each other by the connecting pipe 140, a pressure difference between the upper chamber 51 and the lower chamber 52 is unlikely to occur, but on the other hand, by blocking the flow path by the connecting pipe valve 141, separate pressure control is possible in the upper vacuum circuit 120 and the lower vacuum circuit 130.

[0029] In this way, the upper vacuum circuit 120 is connected to the upper chamber 101, and the lower vacuum circuit 130 is connected to the lower chamber 102 so that compressed air / vacuum forming can be performed by the upper vacuum circuit 120 and the lower vacuum circuit 130. The upper chamber 101 is provided with a first vacuum gauge 105, and the lower chamber 102 is provided with a second vacuum gauge 106. By measuring the degree of vacuum with the first vacuum gauge 105 and the second vacuum gauge 106, the value is used as a trigger for pressure control of the upper chamber 51 and the lower chamber 52.

[0030] The outline of the configuration of the thermoforming apparatus 100 according to the present invention has been described above. Next, the molding procedure using the thermoforming apparatus 100 will be briefly described.

[0031] Figure 2 shows a time chart before molding. The vertical axis shows the operation of each piece of equipment, and the horizontal axis shows the passage of time. The word "chamber" on the left side indicates the upper chamber 101 and lower chamber 102 that make up the working space 50, and means that in the "open" state, the upper chamber 101 and the lower chamber 102 are separated, and in the "closed" state, the upper chamber 101 and the lower chamber 102 are held with the resin sheet S sandwiched between them.

[0032] The "upper vacuum valve" refers to the first main piping valve 123, which is open when "ON" and communicates with the first main piping line 121. The "off" state is closed and the first main piping line 121 is blocked. The "upper vacuum retention valve" refers to the first sub-piping valve 124, which is open when "ON" and blocks the flow in the first sub-piping line 122. The "off" state is closed and blocks the flow in the first sub-piping line 122.

[0033] The "lower vacuum valve" refers to the second main piping valve 133, and is open when "ON" to indicate a state in which the second main piping path 131 is connected. The "off" is closed when "OFF" to indicate a state in which the second main piping path 131 is blocked. The "lower vacuum retention valve" refers to the second sub-piping valve 134, and is open when "ON" to block the flow in the second sub-piping path 132. The "off" is closed when "OFF" to block the flow in the second sub-piping path 132.

[0034] "Heater" indicates the overheated state of the heating means 110; "ON" energizes the heater to heat the resin sheet S, and "OFF" stops energizing the heater. "Upper vacuum" indicates the degree of vacuum in the upper chamber 101. "Lower vacuum" indicates the degree of vacuum in the lower chamber 102. Figure 3 shows a schematic configuration of the thermoforming device at the stage when heating of the resin sheet begins. Figure 4 shows a schematic configuration of the thermoforming device when the vacuum circuit is switched.

[0035] First, after the resin sheet S is put into the thermoforming device 100, the upper chamber 101 and the lower chamber 102 are brought close to each other so that the resin sheet S is sandwiched between the upper chamber 101 and the lower chamber 102. This is performed between t1 and t2 in Fig. 2. Although not shown, the resin sheet S may be held by a holding frame fixed to the lower chamber 102 as necessary.

[0036] Next, during the period from t2 to t5 that constitutes the early exhaust period p1, the first main piping valve 123, the first sub-piping valve 124, the second main piping valve 133, the second sub-piping valve 134, and the connecting piping valve 141 are all opened between t2 and t3. Then, the first vacuum pump 126 and the second vacuum pump 136 increase the degree of vacuum in each of the upper chamber 101 and the lower chamber 102. This state is shown in FIG. 1. Then, by t4, the degree of vacuum in the upper chamber 101 and the lower chamber 102 is reduced to about 700 Pa, and heating by the heating means 110 is started. This state is shown in FIG. 3.

[0037] Then, at the timing t5, the first main piping valve 123 and the second main piping valve 133 are closed to shut off the first main piping line 121 and the second main piping line 131. The connecting piping valve 141 is also shut off. As a result, the degree of vacuum is increased in the first sub-piping line 122, whose flow rate is determined by the first flow rate adjustment valve 125, and the second sub-piping line 132, whose flow rate is determined by the second flow rate adjustment valve 135, so the evacuation speed decreases.

[0038] Next, during the period from t5 to t16 that constitutes the latter exhaust period p2, the first sub-piping valve 124 is closed between t6 and t7 to stop the evacuation in the upper vacuum circuit 120. Furthermore, the first sub-piping valve 124 is opened between t8 and t9 to perform the evacuation in the upper vacuum circuit 120. Furthermore, the first sub-piping valve 124 is controlled to be closed between t11 and t12, and opened between t14 and t15. The opening and closing control of the first sub-piping valve 124 is performed based on the value obtained by measuring the degree of vacuum in the upper chamber 51 by the first vacuum gauge 105. When the upper vacuum degree lower limit b12 is reached, the first sub-piping valve 124 is closed, and when the upper vacuum degree upper limit b11 is reached, the first sub-piping valve 124 is controlled to be opened. In this manner, the degree of vacuum in upper chamber 101 is controlled so as to be between upper vacuum upper limit value b11 and upper vacuum lower limit value b12.

[0039] Also, between t9 and t10, the second sub-piping valve 134 is closed to stop the evacuation in the lower vacuum circuit 130. Next, between t11 and t12, the second sub-piping valve 134 is opened to perform evacuation in the lower vacuum circuit 130. The opening and closing control of the second sub-piping valve 134 is performed based on the value obtained by measuring the vacuum degree in the lower chamber 52 by the second vacuum gauge 106. When the lower vacuum degree lower limit b22 is reached, the second sub-piping valve 134 is closed, and when the lower vacuum degree upper limit b21 is reached, the second sub-piping valve 134 is opened. In this way, the vacuum degree in the lower chamber 102 is controlled between the lower vacuum degree upper limit b21 and the lower vacuum degree lower limit b22. The state of this latter exhaust period p2 is shown in FIG. 4.

[0040] Then, at timing t16, the heating of the resin sheet S is completed. The degree of vacuum in the upper chamber 101 is controlled between the upper vacuum upper limit b11 and the upper vacuum lower limit b12, and the degree of vacuum in the lower chamber 102 is controlled between the lower vacuum upper limit b21 and the lower vacuum lower limit b22, so that the pressure difference between the upper chamber 101 and the lower chamber 102 is a specified value. In this state, molding of the resin sheet S is started using the mold 150.

[0041] The thermoforming apparatus 100 of the first embodiment has the above-mentioned configuration and therefore provides the following actions and effects.

[0042] First, it is possible to provide a thermoforming apparatus 100 capable of preventing drawdown of the resin sheet S during heating, which leads to defective molded products. This is an effect of the thermoforming apparatus 100, which is provided with an upper container (upper chamber 101) that has pressure resistance and opens downward, and a lower container (lower chamber 102) that has pressure resistance and opens upward, in which vacuum circuits (upper vacuum circuit 120, lower vacuum circuit 130) are connected to the upper chamber 101 and the lower chamber 102, and in which a resin molded body (resin sheet S) is held in a working space formed when the upper chamber 101 and the lower chamber 102 are closed, and heated by a heating means 110 to perform pressure molding or vacuum molding, the working space 50 is partitioned by the resin sheet S held in the upper chamber 101 and the lower chamber 102 are closed, forming an upper chamber 51 in the upper chamber 101 and a lower chamber 52 in the lower chamber 102.

[0043] The vacuum circuit 120 further includes a first main piping path 121 connected to the upper chamber 51 to form an upper vacuum circuit 120, a first sub-piping path 122 having a flow path narrowed from the first main piping path 121 and branching off from the first main piping path 121, a second main piping path 131 connected to the lower chamber 52 to form a lower vacuum circuit 130, and a second sub-piping path 132 having a flow path narrowed from the second main piping path 131 and branching off from the second main piping path 131.

[0044] Then, the flow rate is adjusted by switching the flow path from the first main piping path 121 and the second main piping path 131 to the first sub-piping path 122 and the second sub-piping path 132, and the resin sheet S is heated by the heating means 110 and molded. Due to such characteristics, the effect of being able to prevent deformation such as drawdown when the resin sheet S is heated can be obtained.

[0045] This is believed to be due to the action described below. Figure 5 shows a thermoforming machine prepared for comparison in which a sub-pipe is not provided in the vacuum circuit. Thermoforming machine 200 prepared for comparison with the embodiment of the present invention is equipped with a first main piping path 121 and a first main piping valve 123, and a second main piping path 131 and a second main piping valve 133. A first vacuum pump 126 and a second vacuum pump 136 are connected to each of them to perform evacuation.

[0046] In the case of such a configuration, evacuation is performed using the first vacuum pump 126 and the second vacuum pump 136, and when a target degree of vacuum is reached and the first main piping valve 123 and the second main piping valve 133 are closed, the evacuation stops. This may cause the resin sheet S to behave up and down as shown in FIG.

[0047] This is because differences in the capacity of the upper chamber 101 and the lower chamber 102, and differences in the path lengths of the first main piping path 121 and the second main piping path 131 result in a difference in the speed of evacuation, causing the degree of vacuum to increase faster in either the upper chamber 101 or the lower chamber 102, and as a result, swelling of the resin sheet S (when swelling occurs in the lower chamber 102, this is also called drawdown) occurs in the chamber with the lower vacuum.

[0048] In particular, this problem is likely to occur when the effective cross-sectional areas of the first main piping passage 121 and the second main piping passage 131 are increased to increase the vacuum exhaust speed in the process of manufacturing molded products using the thermoforming apparatus 100. This is unlikely to be a problem in the early exhaust period p1, but in the late exhaust period p2, the exhaust speed is fast at the timing of opening and closing the first main piping valve 123 or the second main piping valve 133, and the exhaust speed falls below the lower limit when one side is opened.

[0049] In other words, the controllable vacuum degree has a large fluctuation range, and the resin sheet S moves up and down due to the effect of an overshoot in the vacuum degree that occurs when the first main piping valve 123 or the second main piping valve 133 is opened and closed. This can cause wrinkles in the resin sheet S, resulting in a defective product. To prevent this, it is possible to adjust the vacuum degree by opening the connecting piping valve 141 to leak air from the upper chamber 51 and the lower chamber 52, but this is not very desirable because it can lead to problems such as air getting between the mold 150 and the resin sheet S.

[0050] To prevent such effects, in the thermoforming apparatus 100 of the present invention, the flow paths are switched so that the first main piping path 121 and the second main piping path 131 are used in the early exhaust period p1, and the first sub-piping path 122 and the second sub-piping path 132 are used in the later exhaust period p2. Since the flow rates of the first sub-piping path 122 and the second sub-piping path 132 are restricted by the first flow control valve 125 and the second flow control valve 135, it is possible to suppress overshooting of the vacuum level even when adjusting the vacuum level of the upper chamber 101 and the lower chamber 102 by opening and closing the first sub-piping valve 124 and the second sub-piping valve 134.

[0051] In addition, by separating the upper vacuum circuit 120 and the lower vacuum circuit 130, the upper vacuum upper limit b11 and the upper vacuum lower limit b12, and the lower vacuum upper limit b21 and the lower vacuum lower limit b22 can be set in different ranges. In this example, for example, if the upper vacuum upper limit b11 is 585 Pa, the upper vacuum lower limit b12 is 580 Pa, the lower vacuum upper limit b21 is 605 Pa, and the lower vacuum lower limit b22 is 600 Pa, by setting the upper vacuum circuit 120 to a higher vacuum than the lower vacuum circuit 130, the pressure is adjusted so that the resin sheet S is pulled toward the upper chamber 51.

[0052] Therefore, even if drawdown of the resin sheet S occurs due to the effect of heating by the heating means 110 that starts at (around t4 to t6 in FIG. 2) as shown in Fig. 3, drawdown of the resin sheet S can be suppressed by closing the first sub-piping valve 124 in the latter exhaust period p2 (around t8 to t15 in FIG. 4), separating the upper vacuum circuit 120 from the lower vacuum circuit 130, and setting the degree of vacuum on the upper vacuum circuit 120 side to be higher. As a result, this leads to improved manufacturing accuracy of the molded product.

[0053] Second embodiment Next, a second embodiment of the present invention will be described. The thermoforming device of the second embodiment has almost the same configuration as the thermoforming device of the first embodiment, but the configurations of the upper vacuum circuit 120 and the lower vacuum circuit 130 are different. FIG. 6 shows an explanatory diagram for explaining the schematic configuration of the thermoforming device of the second embodiment. In the upper vacuum circuit 120, a first main piping line 121 and a first sub-piping line 122 are respectively connected to the upper chamber 101. The first main piping line 121 is provided with a first main piping valve 123 and a first vacuum pump 126. The first sub-piping line 122 is provided with a first sub-piping valve 124, a first flow rate control valve 125, and a third vacuum pump 127.

[0054] In the lower vacuum circuit 130, a second main piping line 131 and a second sub-piping line 132 are each connected to the lower chamber 102. A second main piping valve 133 and a second vacuum pump 136 are provided in the second main piping line 131. A second sub-piping valve 134, a second flow rate control valve 135, and a fourth vacuum pump 137 are provided in the second sub-piping line 132. The valves of the upper vacuum circuit 120 and the lower vacuum circuit 130 configured as above can be controlled in the same way as in the thermoforming apparatus 100 of the first embodiment, and similar effects can be obtained.

[0055] Third embodiment Next, a third embodiment of the present invention will be described. The thermoforming device of the third embodiment has almost the same configuration as the thermoforming device of the first embodiment, but the configurations of the upper vacuum circuit 120 and the lower vacuum circuit 130 are different. Fig. 7 shows an explanatory diagram for explaining the schematic configuration of the thermoforming device of the third embodiment. The upper vacuum circuit 120 and the lower vacuum circuit 130 are configured to evacuate using a common fifth vacuum pump 128. The valve control of the upper vacuum circuit 120 and the lower vacuum circuit 130 configured in this way may be the same as that of the thermoforming device 100 of the first embodiment, and similar effects can be obtained.

[0056] Therefore, by connecting the fifth vacuum pump 128 to the upper vacuum circuit 120 and the lower vacuum circuit 130, the number of vacuum pumps used can be reduced, which can contribute to cost reduction. Even if only one fifth vacuum pump 128 is provided, depending on the capacity of the upper chamber 51 and the lower chamber 52 and the required responsiveness, it is possible to obtain the same effects as in the first or second embodiment and to optimize costs. Furthermore, the simplification of the device configuration can be expected to contribute to the miniaturization of the device.

[0057] Although the thermoforming apparatus 100 according to the present invention has been described above, the present invention is not limited thereto, and various modifications are possible within the scope of the present invention. For example, the first sub-pipe line 122 and the second sub-pipe line 132 may be used for a short period of time during the early exhaust period p1 so as to be less susceptible to the effects of vacuum exhaust immediately after start-up, thereby controlling the vacuum exhaust speed. In addition, the configurations of the upper vacuum circuit 120 and the lower vacuum circuit 130 shown in the first to third embodiments are also examples, so that other configurations that provide similar effects may be used. For example, the upper vacuum circuit 120 may adopt the method of the first embodiment, and the lower vacuum circuit 130 may adopt the method of the second embodiment, and so on.

[0058] Furthermore, although the first to third embodiments each describe thermoforming using a mold, this does not preclude the use of the configuration of the present invention for coating or molding onto a substrate or for transferring onto a substrate. [Explanation of symbols]

[0059] S Plastic Sheet 50 Working Space 51 Upper Room 52 Lower chamber 100 Thermoforming equipment 101 Upper Chamber 102 Lower Chamber 110 Heating means 120 Upper vacuum circuit 130 Lower vacuum circuit

Claims

1. A thermoforming device for performing pressure forming or vacuum forming, comprising: an upper container having pressure resistance and opening downward; a lower container having pressure resistance and opening upward; a vacuum circuit connected to the upper container and the lower container; and a heating means for heating a resin molded body while the resin molded body is held in a working space formed when the upper container and the lower container are closed, The work space is divided by the molded body held in a closed state between the upper container and the lower container, so that an upper chamber is formed on the upper container side and a lower chamber is formed on the lower container side, An upper vacuum circuit connected to the upper chamber for adjusting the pressure in the upper chamber includes: a first main piping line and a first sub-piping line whose flow path is narrowed from the first main piping line, a lower vacuum circuit connected to the lower chamber and adjusting the pressure in the lower chamber, a second main piping line and a second sub-piping line whose flow path is narrowed from the second main piping line, a flow rate adjustment is performed by switching a flow path from the first main piping line to the first sub-piping line and from the second main piping line to the second sub-piping line when the molding body is heated by the heating means; A thermoforming device comprising:

2. 2. The thermoforming apparatus of claim 1, The upper vacuum circuit includes: a first main piping valve for connecting and disconnecting the first main piping passage; a first sub-pipe valve for connecting and disconnecting the first sub-pipe; a first flow rate control valve used for the purpose of narrowing the flow path of the first sub-pipe; In the lower vacuum circuit, a second main piping valve for connecting and blocking the second main piping passage; a second sub-pipe valve that opens and closes the second sub-pipe; a second flow rate control valve used for the purpose of narrowing the flow path of the second sub-pipe; reducing the degree of vacuum in the upper chamber and the lower chamber using the first main piping line and the second main piping line, and then closing the first main piping valve and the second main piping valve, and thereafter heating the molded body by the heating means while adjusting the flow rate of the upper vacuum circuit and the flow rate of the lower vacuum circuit by opening and closing the first auxiliary piping valve and the second auxiliary piping valve; A thermoforming device comprising:

3. 3. The thermoforming apparatus according to claim 1, a first vacuum gauge for measuring a vacuum degree is provided in the upper chamber or the first main piping line; a second vacuum gauge for measuring a vacuum degree is provided in the lower chamber or the second main piping line; using the vacuum degree of the upper chamber or the lower chamber obtained by the first vacuum gauge or the second vacuum gauge for controlling opening and closing of the first sub-piping valve or the second sub-piping valve; A thermoforming device comprising:

4. 3. The thermoforming apparatus according to claim 1, a first vacuum pump for increasing the degree of vacuum in the upper chamber is connected to the first main piping line; A second vacuum pump or the first vacuum pump is connected to the second main piping line to increase the vacuum level in the lower chamber, adjusting a flow rate of air exhausted through the upper vacuum circuit and a flow rate of air exhausted through the lower vacuum circuit by opening and closing the first sub-piping valve and the second sub-piping valve; A thermoforming device comprising:

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