Thermoforming apparatus

Abstract

In a thermoforming apparatus (100) for performing pneumatic forming or vacuum forming, an upper chamber (51) is formed in an upper chamber (101), a lower chamber (52) is formed in a lower chamber (102), an upper-side vacuum circuit (120) is connected to the upper chamber (51), and a lower-side vacuum circuit (120) is connected to the lower chamber (52), the upper-side vacuum circuit (120) is connected to the lower chamber (52), and the lower-side vacuum circuit (120) is connected to the lower chamber (52). Comprising a first main distribution line (121) and a first auxiliary distribution line (122) which has a smaller flow path than the first main distribution line (121) and is provided branched from the first main distribution line (121), and the lower vacuum circuit (130) is connected to the lower chamber (52) and comprises a second main distribution line (131) and a second auxiliary distribution line (132) which has a smaller flow path than the second main distribution line (131) and is provided branched from the second main distribution line (131).

Description

Technical Field

[0001] This invention relates to a technique for controlling the pressure inside a thermoforming apparatus, and more specifically, to a technique for adjusting the vacuum level at the start of a vacuum in an upper and lower chamber thermoforming machine. Background Technology

[0002] Thermoforming equipment is widely used in food trays, packaging, and other fields, and an increasing number of outer shells require higher precision forming. Furthermore, when molded products are used in automotive dashboards, decorative films are sometimes applied to the surface to give the product a high-quality feel, and it is desirable to display machine information in designated locations. Therefore, the requirements for positional accuracy in the forming process are becoming increasingly stringent.

[0003] Patent Document 1 discloses a technique related to a vacuum forming machine. This vacuum forming machine seals the forming space by a lower chamber that opens upwards and an upper chamber that opens downwards. Within this forming space, a decorative film is formed in close adhesion to the surface of an object. During a pressure adjustment step, the upper forming space, separated by the decorative film held by the upper and lower chambers, serves as a pressurized environment, while the lower forming space serves as a depressurized environment, ensuring the decorative film adheres tightly to the object. This technique suppresses the sagging of the decorative film, a cause of film lifting, by stopping heating when a pressure difference is generated within the forming space.

[0004] [Prior Technology Documents]

[0005] [Patent Literature]

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-107638. Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] However, when thermoforming a product, there is a time required to reach the target vacuum level while increasing the vacuum level to improve adhesion to the substrate. Therefore, to increase productivity, it is necessary to increase the vacuum exhaust speed of the vacuum circuit; however, the applicant has confirmed that doing so would cause instability in the behavior of the resin sheet or film used as the substrate. The technology described in Patent Document 1 does not address this issue and is difficult to resolve. Generally, depending on the thickness of the film or sheet, the material properties, and the heating temperature control, sag is prone to occur when heating the film or sheet. In particular, the effect of film sag tends to increase when increasing the vacuum level to improve adhesion to the substrate.

[0009] When sheets or films soften due to heating, the applicant's research confirms that in addition to sag at the center of the film, deformation affecting the forming process also occurs. During pneumatic or vacuum forming, in a working space formed with upper and lower containers in a closed state, when forming a film using a mold, if pressure is generated by increasing the vacuum level of the upper and lower chambers separated by the film, the film expands (sags) towards the side with lower pressure. It is known that when the exhaust speed increases, the vacuum level overshoots (exceeds the target range) due to the opening and closing of the valves. Under this influence, a switching phenomenon occurs between the pressure difference in the upper and lower chambers, and the film repeatedly moves up and down. This may lead to defects such as wrinkles in the product.

[0010] While these problems can be solved by significantly reducing the exhaust velocity through smaller piping diameters, this results in a decrease in productivity. Therefore, the object of the present invention is to provide a thermoforming apparatus that can suppress the behavior of sheets or films while increasing productivity.

[0011] [Methods used to solve problems]

[0012] To achieve the aforementioned objectives, a thermoforming apparatus according to the present invention has the following features.

[0013] (1) A thermoforming apparatus for performing pneumatic forming or vacuum forming, comprising:

[0014] The upper container is pressure-resistant and opens downwards.

[0015] The lower container is pressure-resistant and opens upwards; and

[0016] The heating device, with a vacuum circuit connected to the aforementioned upper container and the aforementioned lower container, heats the resin-made molded object within a working space formed while the aforementioned upper container and the aforementioned lower container are closed.

[0017] The aforementioned working space is divided by the formed body, which is held in a closed state between the aforementioned upper container and the aforementioned lower container, forming an upper chamber on the side of the aforementioned upper container and a lower chamber on the side of the aforementioned lower container.

[0018] The upper vacuum circuit, which is connected to the aforementioned upper chamber and adjusts the pressure within the upper chamber, includes a first main piping and a first secondary piping with a reduced flow path compared to the aforementioned first main piping.

[0019] The lower vacuum circuit, which is connected to the aforementioned lower chamber and adjusts the pressure within the lower chamber, includes a second main piping and a second auxiliary piping with a reduced flow path compared to the aforementioned second main piping.

[0020] When the aforementioned formed body is heated by a heating device, the flow rate is adjusted by switching the flow path from the aforementioned first main pipe to the aforementioned first auxiliary pipe and by switching the flow path from the aforementioned second main pipe to the aforementioned second auxiliary pipe.

[0021] By using the configuration described in (1) above, the pressure adjustment of the upper and lower chambers is achieved by switching the first main pipe and the first auxiliary pipe in the upper vacuum circuit, and the second main pipe and the second auxiliary pipe in the lower vacuum circuit. Specifically, the flow rate of the first auxiliary pipe is reduced compared to the first main pipe, and the flow rate of the second auxiliary pipe is reduced compared to the second main pipe. Therefore, the exhaust speed can be arbitrarily selected.

[0022] Considering the numerous takt times involved in manufacturing molded articles using a thermoforming apparatus, the proportion of time required for heating or increasing vacuum is very high. However, if the pipe diameters of the first and second main piping lines are increased to increase the flow rate in order to improve the exhaust velocity, as mentioned in the problem to be solved by the invention, control after reaching the target vacuum level becomes difficult. Therefore, by preparing and switching the first and second auxiliary piping lines with reduced flow rates, vacuum control becomes easier. As a result, both exhaust velocity and vacuum control become easier, and by keeping the pressure difference between the upper and lower chambers small, the effects of pressure differences such as the sag of the film or sheet being formed can be prevented.

[0023] (2) Of the thermoforming apparatus described in (1), the preferred one is

[0024] The aforementioned upper vacuum circuit includes:

[0025] The first main piping valve is used to connect / disconnect the aforementioned first main piping.

[0026] The first set of piping valves is used to connect / disconnect the aforementioned first set of piping; and

[0027] The first flow regulating valve is used to narrow the flow path of the aforementioned first auxiliary piping.

[0028] The aforementioned lower vacuum circuit includes:

[0029] The valve for the second main piping is used to connect / disconnect the aforementioned second main piping.

[0030] The second auxiliary piping valve is used to connect / disconnect the aforementioned second auxiliary piping; and

[0031] The second flow regulating valve is used to narrow the flow path of the aforementioned second auxiliary piping.

[0032] After reducing the vacuum levels of the upper and lower chambers using the first and second main piping lines, the valves for the first and second main piping lines are closed. Then, the flow rates of the upper and lower vacuum circuits are adjusted by opening and closing the valves for the first and second auxiliary piping lines, and the heating device is used to heat the formed body.

[0033] By adjusting the flow rate of air flowing into or out of the upper or lower chamber using either the first or second flow rate regulating valve as described above, the pressure in the upper and lower chambers can be adjusted, thereby controlling the behavior of the resin-made workpiece. It is easily affected by the pressure difference between the upper and lower chambers, or by the flow rate or velocity. Therefore, for example, when the air discharged from the first main circuit connected to the upper chamber is reduced using the first flow rate regulating valve and vacuum forming is controlled on the lower chamber side, reducing the air discharged from the second main circuit connected to the lower chamber using the second flow rate regulating valve and keeping the pressure difference small can prevent the effects of pressure difference such as sag caused by the film or sheet being formed. This can suppress the occurrence of defects such as wrinkles and deformation in the formed product.

[0034] (3) Of the thermoforming apparatus described in (2), the preferred one is

[0035] A first vacuum gauge for measuring vacuum is installed in the aforementioned upper chamber or the aforementioned first main piping.

[0036] A second vacuum gauge for measuring vacuum is installed in the aforementioned lower chamber or the aforementioned second main piping.

[0037] The vacuum level of the upper chamber or the lower chamber obtained by the aforementioned first vacuum gauge or the aforementioned second vacuum gauge is used for the opening and closing control of the aforementioned first auxiliary piping valve or the second auxiliary piping valve.

[0038] By using the configuration described in (3) above, and by setting up a first vacuum gauge and a second vacuum gauge and using their data as a trigger, the vacuum level adjustment can be accurately controlled. As a result, the pressure difference between the upper and lower chambers can be suppressed, and forming can begin from a state that suppresses the expansion of the workpiece.

[0039] (4) Of the thermoforming apparatus described in (2) or (3), the preferred one is

[0040] The first vacuum pump used to increase the vacuum level of the aforementioned upper chamber is connected to the aforementioned first main piping.

[0041] The second vacuum pump or the first vacuum pump used to increase the vacuum level of the aforementioned lower chamber is connected to the aforementioned second main piping.

[0042] The flow rate of air discharged from the upper vacuum circuit and the flow rate of air discharged from the lower vacuum circuit are adjusted by opening and closing the aforementioned first auxiliary piping valve and the aforementioned second auxiliary piping valve.

[0043] By using the configuration described in (4) above, the behavior of the film or sheet material being formed can be suppressed during the process of increasing the vacuum level of the upper and lower chambers. As a result, the occurrence of defects such as wrinkles and deformation in the molded article can be suppressed. As the problem to be solved by the invention is shown, if a pressure difference is generated under the assumption of increasing the vacuum level of the upper and lower chambers, the material being formed will expand upward or downward, and if the pressure balance is replaced, it is also confirmed that the material being formed will move up and down in the vertical direction. This is a phenomenon that is particularly evident when the vacuum exhaust speed of the vacuum circuit is increased in order to improve productivity, and when this expansion (sag, etc.) of the material being formed occurs, the material being formed may unintentionally adhere to the mold surface, resulting in defects in the molded article. In order to solve these problems, the molding process is controlled so that the pressure difference between the upper and lower chambers is unlikely to occur simultaneously.

[0044] Specifically, after reducing the vacuum level to the desired level using the first and second vacuum pumps, the first main piping valve (including the first main piping valve) and the second main piping valve (including the second main piping valve) are closed. While adjusting the flow rates of the first and second auxiliary piping lines using the first and second flow adjustment valves, the vacuum level is controlled by closing the first and second auxiliary piping valves, thus achieving the target vacuum level. By performing this control, the pressure difference between the upper and lower chambers can be suppressed, and forming can begin from a state that suppresses the expansion of the workpiece.

[0045] This result allows for increasing the vacuum exhaust speed while simultaneously using both the first and second main piping lines, and fine-tuning the vacuum level while maintaining the increased vacuum. In other words, it enables both extending the forming cycle time and obtaining high-precision molded products. Furthermore, the same effect can be achieved by using only the first vacuum pump and controlling the first flow control valve, the second flow control valve, the valve for the first auxiliary piping, and the valve for the second auxiliary piping. While a second vacuum pump is provided in addition to the first, and fine control is achieved through controlling each pump individually, cost optimization can be achieved by selectively using only the first vacuum pump when the upper and lower chambers have small capacities and complex control is not required. Attached Figure Description

[0046] Figure 1 This is an explanatory diagram illustrating the general configuration of the thermoforming apparatus according to the first embodiment.

[0047] Figure 2 This is a timeline before molding in the first embodiment.

[0048] Figure 3 This is an explanatory diagram illustrating the general configuration of the thermoforming apparatus for the initial heating stage of the resin sheet according to the first embodiment.

[0049] Figure 4 This is an explanatory diagram illustrating the general configuration of the thermoforming apparatus under the vacuum circuit switching state of the first embodiment.

[0050] Figure 5 This is an explanatory diagram illustrating the general structure of a prior art thermoforming apparatus prepared for comparison.

[0051] Figure 6 This is an explanatory diagram illustrating the general configuration of the thermoforming apparatus according to the second embodiment.

[0052] Figure 7 This is an explanatory diagram illustrating the general configuration of the thermoforming apparatus according to the third embodiment. Detailed Implementation

[0053] (First Implementation)

[0054] First, a summary of the configuration of the thermoforming apparatus 100 according to the first embodiment of the present invention will be given. Figure 1 This is an explanatory diagram illustrating the general configuration of the thermoforming apparatus 100 according to the first embodiment. The thermoforming apparatus 100 holds a resin sheet S in 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 a lifting heating device 110, such as a radiant heating device.

[0055] The resin sheet S, which is equivalent to the molded body, is an ABS sheet made of thermoplastic resin with a thickness of approximately 500 μm. Furthermore, although according to JIS standards, sheets are defined as plate-like materials with a thickness of 250 μm or more, and films are defined as film-like materials with a thickness of less than 250 μm, this invention can also be applied to films. Moreover, the material of the resin sheet S is not limited to ABS; resins such as polypropylene can be appropriately selected according to the requirements.

[0056] The upper vacuum circuit 120 is connected to the upper chamber 101. The upper vacuum circuit 120 includes a first main piping 121 connected to the upper chamber 101 and a first secondary piping 122 arranged in parallel. A first main piping valve 123 is provided in the first main piping 121, and the first main piping 121 is connected / disconnected by opening and closing the first main piping valve 123. A first secondary piping valve 124 and a first flow regulating valve 125 are provided in the first secondary piping 122, and the first secondary piping 122 is connected / disconnected by opening and closing the first secondary piping valve 124. The flow rate of the first secondary piping 122 can be adjusted by adjusting the opening degree of the first flow regulating valve 125.

[0057] The first auxiliary piping 122 is designed to branch between the upper chamber 101 of the first main piping 121 and the first main piping valve 123, and to 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 actuated to discharge air, air discharge can be performed with flow rate adjustment via the first auxiliary piping 122. Here, the first main piping valve 123 and the first auxiliary piping valve 124 are valves used in vacuum circuits and have the function of connecting / closing the circuit, referred to as vacuum valves. Furthermore, the first flow rate regulating valve 125 is a regulating valve used in vacuum circuits that allows flow rate adjustment.

[0058] The lower vacuum circuit 130 is connected to the lower chamber 102. The lower vacuum circuit 130 includes a second main piping 131 connected to the lower chamber 102 and a second auxiliary piping 132 arranged in parallel. A second main piping valve 133 is provided in the second main piping 131, and the second main piping 131 is connected / disconnected by opening and closing the second main piping valve 133. A second auxiliary piping valve 134 and a second flow regulating valve 135 are provided in the second auxiliary piping 132, and the second auxiliary piping 132 is connected / disconnected by opening and closing the second auxiliary piping valve 134. The flow rate of the second auxiliary piping 132 can be adjusted by adjusting the opening degree of the second flow regulating valve 135.

[0059] The second auxiliary piping 132 is designed to branch between the lower chamber 102 of the second main piping 131 and the second main piping valve 133, and to merge between the second main piping valve 133 and the second vacuum pump 136. Therefore, when the second vacuum pump 136, connected to the lower vacuum circuit 130, is actuated to increase the vacuum level, air can be discharged while adjusting the flow rate via the second auxiliary piping 132. Here, the second main piping valve 133 and the second auxiliary piping valve 134 are valves used in vacuum circuits and have the function of connecting / closing the circuit, referred to as vacuum valves. Furthermore, the second flow adjustment valve 135 is a regulating valve used in vacuum circuits that allows for flow rate adjustment.

[0060] The first flow regulating valve 125 is adjusted to allow the flow rate of the first auxiliary piping 122 to be approximately 1 / 10 to 1 / 20 of the flow rate of the first main piping 121. Similarly, the second flow regulating valve 135 is adjusted to allow the flow rate of the second auxiliary piping 132 to be approximately 1 / 10 to 1 / 20 of the flow rate of the second main piping 131. The opening degree of the first flow regulating valve 125 and the second flow regulating valve 135 is preferably selected appropriately based on the physical properties of the resin sheet S.

[0061] The upper chamber 101 and the lower chamber 102 are connected by a connecting pipe 140, and are connected / disconnected via a connecting pipe valve 141. When the upper chamber 101 and the lower chamber 102 are closed, the inner space becomes the working space 50, which 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 connected by the connecting pipe 140, it is difficult for a pressure difference to occur between the upper chamber 51 and the lower chamber 52. On the other hand, by blocking the flow path with the connecting pipe valve 141, other pressure controls can be performed in the upper vacuum circuit 120 and the lower vacuum circuit 130.

[0062] Thus, 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, allowing for pressure / vacuum shaping via the upper vacuum circuit 120 and the lower vacuum circuit 130. A first vacuum gauge 105 is installed in the upper chamber 101, and a second vacuum gauge 106 is installed in the lower chamber 102. The vacuum level is measured using the first vacuum gauge 105 and the second vacuum gauge 106, and the measured values ​​are used to trigger pressure control in the upper chamber 51 and the lower chamber 52.

[0063] The general structure of the thermoforming apparatus 100 according to the present invention has been described above. The forming process using the thermoforming apparatus 100 will be briefly described below.

[0064] Figure 2 This diagram shows the timeline before molding. The vertical axis represents the operation of each machine, and the horizontal axis represents the passage of time. The term "chamber" on the left refers to the upper chamber 101 and the lower chamber 102 that constitute the working space 50. In the "open" state, the upper chamber 101 and the lower chamber 102 are separate, while "closed" means that the upper chamber 101 and the lower chamber 102 are in a state where the resin sheet S is clamped and held.

[0065] "Upper vacuum valve" refers to valve 123 for the first main piping. "ON" indicates that it is in the open state and the first main piping 121 is connected. "OFF" indicates that it is in the closed state and the first main piping 121 is blocked. "Upper vacuum holding valve" refers to valve 124 for the first auxiliary piping. "ON" indicates that it is in the open state and blocks the flow in the first auxiliary piping 122. Also, "OFF" indicates that it is in the closed state and blocks the flow in the first auxiliary piping 122.

[0066] "Lower vacuum valve" refers to valve 133 for the second main piping. "ON" indicates that it is in the open state and the second main piping 131 is connected. "OFF" indicates that it is in the closed state and the second main piping 131 is blocked. "Lower vacuum holding valve" refers to valve 134 for the second auxiliary piping. "ON" indicates that it is in the open state and blocks the flow in the second auxiliary piping 132. Also, "OFF" indicates that it is in the closed state and blocks the flow in the second auxiliary piping 132.

[0067] "Heater" indicates the overheated state of heating device 110. When "ON," the heater is energized to heat the resin sheet S; when "OFF," the heater is de-energized. "Upper vacuum" indicates the vacuum level within the upper chamber 101. "Lower vacuum" indicates the vacuum level within the lower chamber 102. Figure 3 This describes the general structure of a thermoforming apparatus for the initial heating stage of resin sheet production. Figure 4 This section describes the general structure of a thermoforming apparatus under vacuum circuit switching conditions.

[0068] First, after placing the resin sheet S into the thermoforming apparatus 100, the upper chamber 101 and the lower chamber 102 are brought close together, so that the resin sheet S is sandwiched between the upper chamber 101 and the lower chamber 102. This is in... Figure 2 The process takes place between t1 and t2. Additionally, although not shown, the resin sheet S can be held in a retaining frame fixed to the lower chamber 102 as needed.

[0069] Next, during the initial venting period p1 from t2 to t5, between t2 and t3, the first main piping valve 123, the first auxiliary piping valve 124, the second main piping valve 133, the second auxiliary piping valve 134, and the connecting piping valve 141 are all open. Then, the vacuum levels of the upper chamber 101 and the lower chamber 102 are increased by the first vacuum pump 126 and the second vacuum pump 136. This state is... Figure 1 The state shown. Then, at t4, the vacuum level in the upper chamber 101 and the lower chamber 102 decreases to approximately 700 Pa, and heating begins from the heating device 110. This state is... Figure 3 The state shown.

[0070] Then, at time t5, the first main piping valve 123 and the second main piping valve 133 are closed, shutting off the first main piping line 121 and the second main piping line 131. Additionally, the connecting piping valve 141 is also shut off. As a result, because the vacuum levels of the first auxiliary piping line 122 (whose flow rate is determined by the first flow regulating valve 125) and the second auxiliary piping line 132 (whose flow rate is determined by the second flow regulating valve 135) increase, the vacuum exhaust rate decreases.

[0071] Next, during the later exhaust period p2 from t5 to t16, between t6 and t7, exhaust in the upper vacuum circuit 120 is stopped by closing the first auxiliary piping valve 124. Then, between t8 and t9, vacuum exhaust in the upper vacuum circuit 120 is performed by opening the first auxiliary piping valve 124. Then, between t11 and t12, the first auxiliary piping valve 124 is closed, and between t14 and t15, the first auxiliary piping valve 124 is controlled to be open. This opening and closing control of the first auxiliary piping valve 124 is based on the value obtained by measuring the vacuum level of the upper chamber 51 using the first vacuum gauge 105. If the lower limit of the upper vacuum level b12 is reached, the control of closing the first auxiliary piping valve 124 is performed; if the upper limit of the upper vacuum level b11 is reached, the control of opening the first auxiliary piping valve 124 is performed. In this way, the vacuum level of the upper chamber 101 can be controlled between the upper vacuum limit value b11 and the lower vacuum limit value b12.

[0072] Furthermore, between t9 and t10, vacuum venting in the lower vacuum circuit 130 is stopped by closing the second auxiliary piping valve 134. Next, between t11 and t12, vacuum venting in the lower vacuum circuit 130 is performed by opening the second auxiliary piping valve 134. The opening and closing control of this second auxiliary piping valve 134 is based on the value obtained by measuring the vacuum level of the lower chamber 52 using the second vacuum gauge 106. If the lower vacuum level lower limit b22 is reached, the second auxiliary piping valve 134 is closed; if the lower vacuum level upper limit b21 is reached, the second auxiliary piping valve 134 is opened. This allows the vacuum level of the lower chamber 102 to be controlled between the lower vacuum level upper limit b21 and the lower vacuum level lower limit b22. During this later venting period, the state of p2 is... Figure 4 The state shown.

[0073] Then, at time t16, the heating of the resin sheet S is completed. Furthermore, because the vacuum level of the upper chamber 101 is controlled between the upper vacuum limit b11 and the upper vacuum limit b12, and the vacuum level of the lower chamber 102 is controlled between the lower vacuum limit b21 and the lower vacuum limit b22, the pressure difference between the upper chamber 101 and the lower chamber 102 is a predetermined value. In this state, the molding of the resin sheet S begins using the mold 150.

[0074] Since the thermoforming apparatus 100 of the first embodiment has the above-described configuration, it has the following functions and effects.

[0075] Firstly, as an effect, it is provided that the thermoforming apparatus 100 can prevent defects in the molded article caused by the sag of the resin sheet S during heating. The thermoforming apparatus 100 includes an upper container (upper chamber 101) with pressure resistance and an opening to the lower side, and a lower container (lower chamber 102) with pressure resistance and an opening to the upper side. Vacuum circuits (upper vacuum circuit 120 and lower vacuum circuit 130) are connected to the upper chamber 101 and the lower chamber 102. A resin sheet (resin sheet S) is held in the working space formed when the upper chamber 101 and the lower chamber 102 are closed and heated by a heating device 110. In the thermoforming apparatus 100 that performs air pressure forming or vacuum forming, the resin sheet S held in the upper chamber 101 and the lower chamber 102 are separated by the working space 50. An upper chamber 51 is formed in the upper chamber 101 and a lower chamber 52 is formed in the lower chamber 102.

[0076] Then, it includes a first main piping 121, a first auxiliary piping 122, a second main piping 131, and a second auxiliary piping 132. The first main piping 121 is connected to the upper chamber 51 to form an upper vacuum circuit 120. The first auxiliary piping 122 has a smaller flow path than the first main piping 121 and branches off from the first main piping 121. The second main piping 131 is connected to the lower chamber 52 to form a lower vacuum circuit 130. The second auxiliary piping 132 has a smaller flow path than the second main piping 131 and branches off from the second main piping 131.

[0077] Then, by switching the flow path from the first main piping 121 and the second main piping 131 to the first auxiliary piping 122 and the second auxiliary piping 132, the flow rate is adjusted, and the resin sheet S is heated by the heating device 110 and formed. Due to this feature, the aforementioned effect of preventing deformation such as sag during the heating of the resin sheet S can be obtained.

[0078] This is believed to be due to the effect of the following explanation. Figure 5The image shows a thermoforming machine prepared for comparison, without auxiliary piping in the vacuum circuit. The thermoforming machine 200 prepared for comparison with an embodiment of the present invention includes a first main piping 121 and a first main piping valve 123, and a second main piping 131 and a second main piping valve 133. It is then configured to be connected to a first vacuum pump 126 and a second vacuum pump 136 for vacuum exhaust.

[0079] In this configuration, vacuum exhaust is performed using a first vacuum pump 126 and a second vacuum pump 136. Vacuum exhaust stops when the target vacuum level is reached and the first main piping valve 123 and the second main piping valve 133 are closed. As a result, the resin sheet S may exhibit the following characteristics: Figure 5 The shown action is vertical movement.

[0080] This is due to the difference in capacity between the upper chamber 101 and the lower chamber 102, and the difference in length between the first main pipe 121 and the second main pipe 131, resulting in a difference in the vacuum exhaust speed. The vacuum level of either the upper chamber 101 or the lower chamber 102 rises faster, and as a result, the resin sheet S with the lower vacuum level expands (the case of expansion towards the lower chamber 102 is also called sag).

[0081] In particular, this problem is prone to occur during the manufacturing process of molded articles using the thermoforming apparatus 100 when the effective cross-sectional area of ​​the first main piping 121 and the second main piping 131 is increased to improve the vacuum exhaust speed. Although this is unlikely to be a problem during the early exhaust period p1, it is affected by the rapid exhaust speed at the opening and closing points of the first main piping valve 123 or the second main piping valve 133 during the later exhaust period p2, and decreases to below the lower limit during the opening phase.

[0082] In other words, the amplitude of the controllable vacuum becomes larger, and due to the vacuum overshoot that occurs when the first main piping valve 123 or the second main piping valve 133 is opened and closed, the resin sheet S moves up and down. As a result, the resin sheet S may wrinkle, leading to product defects. To prevent this, although it is possible to adjust the vacuum by venting the upper chamber 51 and lower chamber 52 through the opening of the connecting piping valve 141, this is not ideal because it may cause problems such as air entering between the mold 150 and the resin sheet S.

[0083] To prevent these effects, in the thermoforming apparatus 100 of the present invention, the flow path is switched so that the first main piping 121 and the second main piping 131 are used during the initial venting period p1, and the first auxiliary piping 122 and the second auxiliary piping 132 are used during the later venting period p2. Since the flow paths of the first auxiliary piping 122 and the second auxiliary piping 132 are reduced by the first flow regulating valve 125 and the second flow regulating valve 135, even when the vacuum of the upper chamber 101 and the lower chamber 102 is adjusted by opening and closing the first auxiliary piping valve 124 and the second auxiliary piping valve 134, vacuum overshoot can be suppressed.

[0084] Furthermore, by separating the upper vacuum circuit 120 and the lower vacuum circuit 130, the upper vacuum limit value b11 and the upper vacuum limit value b12, as well as the lower vacuum limit value b21 and the lower vacuum limit value b22, can be set to their respective ranges. Here, for example, if the upper vacuum limit value b11 is set to 585 Pa, the upper vacuum limit value b12 is set to 580 Pa, and the lower vacuum limit value b21 is set to 605 Pa and the lower vacuum limit value b22 is set to 600 Pa, by setting the vacuum level of the upper vacuum circuit 120 to be higher than that of the lower vacuum circuit 130, the pressure is adjusted to pull the resin sheet S towards the upper chamber 51.

[0085] Therefore, even in such Figure 3 As shown ( Figure 2 In the case of sag of resin sheet S caused by the heating effect of heating device 110 starting from t4 to t6, via p2 (during the later venting period) Figure 4 (Around t8 to t15), closing the first auxiliary piping valve 124 separates the upper vacuum circuit 120 from the lower vacuum circuit 130, allowing the vacuum level on the upper vacuum circuit 120 side to be set higher, thereby suppressing the sag of the resin sheet S. This result can improve the manufacturing accuracy of the molded product, etc.

[0086] (Second Implementation)

[0087] Next, the second embodiment of the present invention will be described. Although the thermoforming apparatus of the second embodiment has almost the same configuration as the thermoforming apparatus of the first embodiment, the configurations of the upper vacuum circuit 120 and the lower vacuum circuit 130 are different. Figure 6This diagram illustrates the general configuration of the thermoforming apparatus according to the second embodiment. In the upper vacuum circuit 120, a first main piping 121 and a first auxiliary piping 122 are respectively connected to the upper chamber 101. A first main piping valve 123 and a first vacuum pump 126 are provided in the first main piping 121. A first auxiliary piping valve 124, a first flow regulating valve 125, and a third vacuum pump 127 are provided in the first auxiliary piping 122.

[0088] In the lower vacuum circuit 130, the second main piping 131 and the second auxiliary piping 132 are respectively connected to the lower chamber 102. The second main piping 131 is equipped with a second main piping valve 133 and a second vacuum pump 136. The second auxiliary piping 132 is equipped with a second auxiliary piping valve 134, a second flow regulating valve 135, and a fourth vacuum pump 137. The valve control of the upper vacuum circuit 120 and the lower vacuum circuit 130 configured in this way can be the same as the valve control of the thermoforming apparatus 100 in the first embodiment, and the same effect can be obtained.

[0089] (Third Implementation)

[0090] Next, the third embodiment of the present invention will be described. Although the thermoforming apparatus of the third embodiment has almost the same configuration as the thermoforming apparatus of the first embodiment, the configurations of the upper vacuum circuit 120 and the lower vacuum circuit 130 are different. Figure 7 This diagram illustrates the general configuration of the thermoforming apparatus according to the third embodiment. It shows a configuration where a common fifth vacuum pump 128 is used to exhaust air from both the upper vacuum circuit 120 and the lower vacuum circuit 130. The valve control of the upper vacuum circuit 120 and the lower vacuum circuit 130 configured in this way can be the same as the valve control of the thermoforming apparatus 100 of the first embodiment, and the same effect can be obtained.

[0091] 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, thus helping to lower costs. Depending on the capacity of the upper chamber 51 and the lower chamber 52, the required responsiveness, etc., even with only one fifth vacuum pump 128, the same effects as the first or second embodiment can be obtained, and cost optimization can be achieved. Furthermore, simplifying the device configuration is expected to contribute to the miniaturization of the device.

[0092] While the thermoforming apparatus 100 according to the present invention has been described above, the present invention is not limited thereto, and various modifications can be made without departing from its spirit. For example, during the initial venting period p1, in order to avoid being easily affected by direct vacuum evacuation after the start, the first auxiliary piping 122 and the second auxiliary piping 132 can be used only for a short period of time, and the vacuum venting speed can be controlled. Furthermore, since any of the configurations of the upper vacuum circuit 120 and the lower vacuum circuit 130 shown in the first to third embodiments are examples, other configurations that can achieve the same effect can be used. For example, the upper vacuum circuit 120 can adopt the method of the first embodiment, and the lower vacuum circuit 130 can adopt the method of the second embodiment, etc., can be combined.

[0093] Furthermore, although each of the first to third embodiments describes thermoforming using a mold, the configuration of the present invention can be used for coating molding of substrates, transfer printing of substrates, etc.

[0094] [Explanation of reference numerals in the attached figures]

[0095] S: Resin sheet material

[0096] 50: Workspace

[0097] 51: Upper room

[0098] 52: Lower Room

[0099] 100: Thermoforming apparatus

[0100] 101: Upper chamber

[0101] 102:Lower chamber

[0102] 110: Heating device

[0103] 120: Upper vacuum circuit

[0104] 130: Lower vacuum circuit

Claims

1. A thermoforming apparatus for performing pneumatic forming or vacuum forming, comprising: The upper container is pressure-resistant and opens downwards. The lower container is pressure-resistant and opens upwards; and The heating device, with a vacuum circuit connected to the upper and lower containers, heats the resin-made workpiece within a working space formed while the upper and lower containers are closed. The work space is divided by the formed body, which is held in a closed state by the upper and lower containers, with an upper chamber formed on the upper container side and a lower chamber formed on the lower container side. The upper vacuum circuit, which is connected to the upper chamber and adjusts the pressure inside the upper chamber, includes a first main piping and a first secondary piping with a reduced flow path compared to the first main piping. The lower vacuum circuit, which is connected to the lower chamber and adjusts the pressure within the lower chamber, includes a second main piping and a second auxiliary piping with a reduced flow path compared to the second main piping. When the formed body is heated by the heating device, the flow rate is adjusted by switching the flow path from the first main pipe to the first auxiliary pipe and from the second main pipe to the second auxiliary pipe.

2. The thermoforming apparatus according to claim 1, wherein the upper vacuum circuit comprises: The first main piping valve is used to connect / disconnect the first main piping. The first auxiliary piping valve is used to connect / disconnect the first auxiliary piping line; as well as The first flow regulating valve is used to narrow the flow path of the first auxiliary piping. The lower vacuum circuit includes: The valve for the second main piping is used to connect / disconnect the second main piping. The second auxiliary piping valve is used to connect / disconnect the second auxiliary piping line; as well as The second flow regulating valve is used to narrow the flow path of the second auxiliary piping. After reducing the vacuum level of the upper and lower chambers using the first and second main piping lines, the first and second main piping valves are closed. Then, the flow rates of the upper and lower vacuum circuits are adjusted by opening and closing the first and second auxiliary piping valves, and the formed body is heated by the heating device.

3. The thermoforming apparatus according to claim 2, wherein a first vacuum gauge for measuring vacuum degree is provided in the upper chamber or the first main piping. A second vacuum gauge for measuring vacuum is installed in the lower chamber or the second main piping. The vacuum level of the upper chamber or the lower chamber obtained by the first vacuum gauge or the second vacuum gauge is used for the opening and closing control of the first auxiliary piping valve or the second auxiliary piping valve.

4. The thermoforming apparatus according to claim 2, wherein a first vacuum pump for increasing the vacuum level of the upper chamber is connected to the first main piping. The second vacuum pump or the first vacuum pump used to increase the vacuum level of the lower chamber is connected to the second main piping. The flow rate of air discharged from the upper vacuum circuit and the flow rate of air discharged from the lower vacuum circuit are adjusted by opening and closing the first auxiliary piping valve and the second auxiliary piping valve.

Images