Mold heating device and powder slush molding machine

Abstract

To provide a mold heating device and a powder slush molding machine, which are capable of efficiently and uniformly heating a mold placed inside a heating unit without substantially generating exhaust gas that causes environmental degradation.SOLUTION: There is provided a mold heating device comprising: a mold placement unit for holding the mold; a blower unit that takes in air from the inside of a housing through an air intake port, sends the air through an air blowing duct, and circulates the air inside the housing; and a heating unit that communicates with the air blowing duct and configured to heat the circulating air sent by the blower unit. The heating unit has an inclined surface that expands a flow path cross-sectional area toward the mold placement unit, and a central blowing port and a side blowing port for blowing heated air. Between the inclined surface and the central blowing port, a predetermined frame body having openings at a top and bottom and one or more long resistance heaters having an electric heating element are disposed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a mold heating device and a powder slush molding machine. In particular, the present invention relates to a mold heating device that can efficiently and uniformly heat a mold placed inside a heating unit without substantially generating exhaust gas that causes environmental degradation, and a powder slush molding machine using the same.

Background Art

[0002] Conventionally, in manufacturing a sheet-like object having a complex shape such as an automotive interior material, a powder slush molding method is widely practiced in which powder resin powder (molding resin) is sprayed onto the molding surface of a heated mold to form a resin melt, and then cooled and solidified to form a resin molded product. Such a powder slush molding method consists of steps such as a mold heating step, a powder slush step, a cooling step, and a demolding step.

[0003] Here, as shown in FIG. 9(a), in a mold heating step, there is disclosed a powder slush molding machine (not shown) having a mold heating device 100 provided with a predetermined electric heating element 152a that generates heat by energization and has a heat-resistant member at least on the back side (for example, see Patent Document 1). That is, in the mold heating device 100, the mold 160 can be heated quickly and uniformly by heating it with an infrared heater as the electric heating element 152a from above the mold 160 and blowing hot air W from the hot air generating device 140 from below and the side.

[0004] Also, as shown in FIG. 9(b), there is disclosed a powder slush molding machine (not shown) having a mold heating device 200 provided with a shutter 259 that opens both front and rear along the conveyance direction of the mold at the ceiling portion of the mold heating device 200 and a hot air generating device 240 below (for example, see Patent Document 2). In other words, by providing a shutter 259 of a predetermined configuration in the mold heating device 200, the mold can be moved in and out quickly, and the release of heat associated with opening the shutter 259 can be suppressed. Furthermore, by suppressing heat release in this way, the mold 260 can be effectively heated using only hot air from below, allowing for rapid heating of the mold 260 in a small space. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-98544 (Claims, etc.) [Patent Document 2] Japanese Patent Publication No. 2020-29018 (Claims, etc.) [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the mold heating device described in Patent Document 1 has a far-infrared heater installed above the mold. Therefore, when the top of the device is opened, such as when changing the mold, the opening inevitably becomes larger, which causes the temperature inside the mold heating device to drop excessively. Furthermore, since the infrared heater requires a heat-resistant component on its back, a problem arose where placing it below the mold heating device obstructed the blowing of hot air.

[0007] Furthermore, the mold heating device described in Patent Document 2 essentially burns gas or the like to generate hot air, and has the problem of requiring a large amount of fuel (LPG, etc.) in order to heat the mold to a more rapid and uniform temperature. Therefore, burning hydrocarbon fuels in this way not only increases manufacturing costs but also contributes to further environmental degradation and global warming, as it releases large amounts of exhaust gases such as carbon dioxide (CO2) and carbon monoxide (CO).

[0008] Therefore, in view of these problems, the inventors of this invention have made diligent efforts and have found that by providing a predetermined heating section, the mold can be heated efficiently and uniformly without using a combustion heater, thus completing the present invention. In other words, the object of the present invention is to provide a mold heating device and a powder slush molding machine using the same, which can efficiently and uniformly heat a mold placed inside a heating section without generating exhaust gases that cause environmental degradation. [Means for solving the problem]

[0009] According to the present invention, a mold heating device for heating a mold comprises a mold mounting section for holding the mold in a predetermined position within a housing, a blowing section that takes in air from inside the housing through an air intake and sends the air through a blowing duct, and a heating section that communicates with the blowing duct and heats the air sent by the blowing section. The heating section has an inclined surface that increases the cross-sectional area of ​​the flow path toward the mold mounting section, a central outlet that blows heated air toward the bottom of the mold, and a lateral outlet that blows heated air toward the side of the mold. Between the inclined surface and the central outlet, one or more elongated resistance heating heaters are arranged, each having a frame with openings at the top and bottom and an electric heating element surrounded by the frame. In other words, by making the resistance heating heater elongated, the opening required to insert the resistance heating heater into the housing can be reduced, thereby reducing the release of heated air to the outside of the housing. At the same time, the volume of the heating section can be increased, allowing heated air to be blown uniformly onto the mold. Furthermore, by surrounding the electric heating element with a frame having openings at the top and bottom, the air introduced from the air blower can be straightened without excessive dispersion, and the heated air can be blown onto the mold more efficiently. Furthermore, even when multiple resistance heating elements are provided, enclosing them in a predetermined frame allows for precise placement at predetermined intervals or at arbitrary positions, and also facilitates replacement in the event of a malfunction. Therefore, the mold placed inside can be heated efficiently and uniformly without generating exhaust gases that cause environmental degradation.

[0010] Furthermore, in constructing the present invention, the heating section has a circular communication port that communicates with the air duct, and it is preferable that the shape of the heating section is a truncated square pyramidal shape that slopes outwards in all directions from the surface having the communication port. This configuration allows the air supplied from the blower to flow effectively within the heating section, enabling more effective heating of the air. Furthermore, it is possible to make the air temperature uniform, allowing the mold to be heated more efficiently and uniformly.

[0011] Furthermore, in constructing the present invention, it is preferable that the resistance heating heater is fixed to the side of the housing via a frame, and that when the frame is fixed to the housing, it has a heating region that is inserted into the heating section and a non-heating region located between the heating region and the housing. This configuration allows only the air inside the heating section to be heated, enabling more efficient heating of the mold. Furthermore, by returning the heated air through the non-heated area along the direction of gravity to the bottom of the mold heating device, a portion of it can be taken back into the air blower, thereby significantly improving the reusability of the heated air.

[0012] Furthermore, in constructing the present invention, it is preferable that the resistance heating heater has a ceramic rod as its core material, and that an electric heating element is wound around the core material in a coil shape. This configuration allows the electric heating element to be inserted into the heating section without bending, and the air can be effectively heated by the resistance heater. Furthermore, even if the unit is subjected to airflow from the heating element, the risk of it shaking and coming into contact with the heating element wall or other resistance heating elements, thereby reducing the risk of short circuits.

[0013] Furthermore, in constructing the present invention, it is preferable that a heat-shielding material is attached around the heating element side of the central air outlet. This configuration allows heat from the resistance heater to be effectively distributed around the central outlet, enabling the mold to be heated with a more uniform temperature distribution.

[0014] Furthermore, in constructing the present invention, it is preferable that the heating section has louvers at the central outlet and the side outlets to adjust the direction in which the heated air is blown. This configuration allows the hot air blown from each outlet to be effectively distributed throughout the entire mold, resulting in a more uniform temperature distribution when heating the mold.

[0015] Furthermore, in constructing the present invention, it is preferable that the mold mounting section, the resistance heating heater, and the inclined surface are arranged in order along the direction of gravity. This configuration allows the air heated by the resistance heater to rise, enabling more efficient delivery of hot air to the mold without lowering its temperature.

[0016] Another aspect of the present invention is a powder slush molding machine comprising: a mold heating device for heating a mold; a powder slush device for forming a sheet-like material on the heated inner surface of the mold by spraying a molding resin while powdering it; a mold cooling device for cooling the mold and the formed sheet-like material; a mold processing device for demolding the cooled sheet-like material from the mold; and a conveying device for moving the mold between its various parts along a predetermined conveying direction. Specifically, the mold heating device includes a mold placement part for holding the mold at a predetermined position inside the housing, a blower part for taking in air inside the housing from an air intake and sending the air through a blower duct, and a heating part that communicates with the blower duct and heats the air sent by the blower part. The heating part has an inclined surface that expands the flow path cross-sectional area toward the mold placement part, a central air outlet for blowing the heated air toward the lower surface of the mold, and side air outlets for blowing the heated air toward the side surface of the mold. Between the inclined surface and the central air outlet, one or more long resistance heaters having a frame body with openings vertically and an electric heating element surrounded by the frame body are arranged. That is, by making the resistance heater long, the opening when inserting the resistance heater into the housing can be made smaller, the release of the heated air to the outside of the housing can be reduced, and the volume of the heating part can be widened to uniformly blow the heated air against the mold. Also, by surrounding the periphery of the electric heating element with a frame body having an opening at the bottom, the air introduced from the blower part can be rectified without being overly dispersed, and the heated air can be blown more efficiently against the mold. Furthermore, even when a plurality of resistance heaters are provided, by surrounding them with a predetermined frame body, they can be accurately arranged at a predetermined interval or at an arbitrary position, and it is also easier to replace them in case of a problem. Therefore, it is possible to efficiently form a uniform sheet-like object while suppressing the generation of exhaust gases such as carbon dioxide gas that leads to global warming and the like.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a perspective view of the inside of a housing provided for explaining the internal configuration of the mold heating device of the present invention. [Figure 2] FIGS. 2(a) to (b) are diagrams provided for explaining the main configuration of the mold heating device of the present invention. [Figure 3] FIG. 3 is a diagram provided for explaining an example of the resistance heater of the present invention. [Figure 4]Figures 4(a) to 4(c) are diagrams provided to illustrate examples of the configuration of the heating section in the present invention. [Figure 5] Figures 5(a) to 5(d) are provided to illustrate modified examples of the heating section in the present invention. [Figure 6] Figure 6 is a diagram used to illustrate the airflow within the housing of the present invention. [Figure 7] Figure 7 is a diagram used to illustrate the temperature change at the central outlet in the present invention and the prior art. [Figure 8] Figure 8 is a diagram provided to illustrate another embodiment of the present invention, a powder slush molding machine. [Figure 9] Figures 9(a) and 9(b) illustrate a mold heating device in a conventional powder slush molding machine. [Modes for carrying out the invention]

[0018] The embodiments of the present invention will be described below with reference to the drawings as appropriate. Furthermore, the figures used in this explanation are schematic representations sufficient to understand these inventions, and the devices, shapes, dimensions, materials, etc., described in the explanation are merely preferred examples within the scope of this invention. Accordingly, the present invention is not limited without reason to the following embodiments.

[0019] [First Embodiment] The first embodiment, as illustrated in Figures 1 and 2(a) to 2(b), is a mold heating device 10 for heating a mold 13, comprising: a mold mounting section 12 for holding the mold 13 in a predetermined position within a housing 11; a blowing section 14 that takes in air from inside the housing 11 through an air intake port 14b and sends the air through a blowing duct 14a; and a heating section 16 that communicates with the blowing duct 14a and heats the air sent by the blowing section 14, wherein the heating section 16 has a flow path cross-sectional area toward the mold mounting section 12 The mold heating device 10 is characterized by having an inclined surface 16a that expands the temperature, a central outlet 16c that blows heated air toward the lower surface of the mold 13, and a lateral outlet 16d that blows heated air toward the side of the mold 13, and by having one or more elongated resistance heating heaters 16b, each having a frame 15a (see Figure 3) with openings at the top and bottom, and an electric heating element 15b (see Figure 3) surrounded by the frame 15a, positioned between the inclined surface 16a and the central outlet 16c. Hereinafter, embodiments of the mold heating apparatus of the present invention will be described in detail with reference to the drawings as appropriate.

[0020] 1. Mold The mold has a configuration with recesses that have the shape of the desired sheet-like material. By pouring resin powder into the recesses while heated, the resin powder is melted and adhered to the molding surface, thereby obtaining a sheet-like material as a molded product. The material of the mold is not particularly limited as long as it has heat resistance that prevents thermal deformation when heated and strength that allows for resin molding, but it is generally preferable to use iron, steel, cast iron, etc.

[0021] 2. Enclosure The enclosure is the part that heats the mold by placing the mold inside and trapping heated air within it. In other words, as shown in Figure 2(a), the housing 11 has a wall surface that covers the perimeter and is equipped with a mold mounting section 12, a heating section 16, and an air blowing section 14 inside. Specifically, the material of the casing is not particularly limited, but it is preferably made of iron, stainless steel, or the like. The reason for this is that such materials can stably support even heavy molds when placed on them. Furthermore, such materials can effectively prevent thermal deformation even when high-temperature air is introduced into them.

[0022] 3. Mold mounting section The mold mounting section is a part that holds the mold in a predetermined position inside the housing, with the recessed surface, which serves as the molding surface, facing the direction of gravity (hereafter, the direction of gravity may simply be referred to as downward). Specifically, as shown in Figures 2(a) to 2(b), when viewed from the front, it is preferable that the mold 13 is held higher than the top plate 22 of the heating section 16, and that the support frame 12a and the mold 13 are in contact via an extension plate 12b that extends upward from the support frame 12a. The reason for this is that the support frame allows the mold to be held stably, and by indirectly bringing the support frame and the mold into contact via the extended plate, the contact area between the support frame and the mold is reduced, allowing for faster heating. Therefore, it is preferable that the thickness of the extension plate be within the range of 1 to 30 mm, more preferably within the range of 2 to 20 mm, and even more preferably within the range of 3 to 10 mm. In this invention, "front view" refers to the view as shown in Figure 2(a), where the side outlets are facing each other from left to right.

[0023] 4. Air blower The air blower unit is the part that takes in air from inside the housing through the air intake and sends the air to the heating unit, which will be described later, via the air blower duct. In other words, the air blowing unit has a configuration (sometimes referred to as a self-circulating type) that circulates air sequentially through the air blowing unit, the heating unit, and each outlet inside the housing. The reason for this configuration is that by reusing the air that has been heated once, it becomes less likely for the temperature inside the enclosure to drop. Furthermore, even when the enclosure door is opened for mold removal or other purposes, the heated air can be retained inside the enclosure without escaping, allowing the mold to be heated continuously and effectively.

[0024] Furthermore, although the blowing section is not particularly limited, it is preferable to include one of the following: a centrifugal blower (sometimes referred to as a cross-flow blower), an axial flow blower, a mixed-flow blower, a rotary piston blower, etc. The reason for this is that such a blower can take in a sufficient amount of air to blow onto the mold, and can maintain stable operation even when exposed to heated air. Therefore, as shown in Figures 1 and 2(a) to (b), the air blowing unit 14 is a centrifugal blower that blows air by rotating fins (not shown) that are linked to the blowing motor 14d, and it is particularly preferable that it is configured to send air to the heating unit via the air blowing duct 14a.

[0025] Furthermore, it is preferable that the air supply duct is connected in a U-shape from the air supply unit 14 to the heating unit 16, as shown in Figures 1 and 2(b). The reason for this configuration is that it makes it easier to arrange the air blower and heating unit side by side, allowing the mold heating device to be made more compact.

[0026] 5.Heating part (1) Basic configuration The heating section is the part that heats the air that is blown around the mold. In other words, it is connected to the air supply duct and is the part that heats the air supplied from the air supply section (sometimes referred to as circulating air) and guides the heated circulating air to the central outlet and the side outlets. Therefore, the basic configuration includes an inclined surface 16a, a resistance heating heater 16b, a central outlet 16c, and a side outlet 16d, as shown in Figure 2(a). Specifically, the heating element is preferably made of iron, stainless steel, aluminum, or the like.

[0027] (2) Resistance heating heater A resistance heater is a device that uses a power source to heat an electrically heated element that has a resistance above a certain level and is a conductive material, by passing an electric current through it, thereby transferring the Joule heat generated to the surrounding area. In other words, as shown in Figure 3, it is characterized by having an electric heating element 15b and electrodes (15g, 15h) at both ends of the electric heating element, and being elongated in shape. Specifically, it is preferable that the electric heating element includes nickel-chromium alloy (nichrome), iron-chromium alloy, molybdenum disilicide, etc. The reason for this is that such materials can efficiently convert the applied electric current into heat, allowing the mold to be heated more quickly and efficiently.

[0028] Furthermore, as shown in Figure 3, it is preferable that the resistance heating heater has a configuration in which the electric heating element 15b is folded back along the width direction of the frame so that the electrodes (15g, 15h) at both ends are arranged on the same side of the frame. The reason for this configuration is that it allows for simpler wiring of the power supply and other components in the electric heating element, and consequently, enables the overall miniaturization of the mold heating device.

[0029] Furthermore, the resistance heating heater is characterized by having an opening in the vertical direction and a frame 15a surrounding the electric heating element 15b, which will be described later, as shown in Figure 3. Specifically, it is preferable that the frame has a metal plate surrounding the electric heating element. The reason for this configuration is that the heat from the electric heating element heats the metal plate, increasing the contact surface area with the surrounding air as a heat transfer medium, and thus allowing the air to be heated more efficiently. Furthermore, because it has openings in the vertical direction, the air introduced from the blower can be straightened without excessive dispersion, allowing the heated air to be blown onto the mold more efficiently. Therefore, although not particularly limited, as shown in Figure 3, it is preferable that the height H of the frame along the direction of gravity be in the range of 30 to 300 mm, more preferably in the range of 50 to 250 mm, and even more preferably in the range of 100 to 200 mm.

[0030] Furthermore, although not particularly limited, it is preferable that the frame length La be within the range of 50 to 250 mm, as shown in Figure 3. The reason for this is that, with this length, it is easy to position the electric heating element without it coming into contact with the frame, and it also allows for more efficient air guidance without dispersing the air within the frame. Therefore, it is more preferable to set the frame length La to a value within the range of 80 to 230 mm, and even more preferable to set it to a value within the range of 100 to 200 mm.

[0031] Furthermore, although not particularly limited, it is preferable that the width Wa of the frame be within the range of 500 to 3000 mm, as shown in Figure 3. The reason for this is that, with this width, when inserted into the heating section, it can maintain its position in a cantilevered manner without distortion, and even when inserted from the side of the mold heating device, the electric heating element can be easily positioned in the center. Therefore, it is more preferable to set the width Wa of the frame to a value within the range of 800 to 2500 mm, and even more preferable to set it to a value within the range of 1000 to 2000 mm.

[0032] Furthermore, when viewed from above, the shape of the resistance heater is preferably such that the outer edge has a rectangular, elliptical, elongated hole, or polygonal shape (for example, a triangular to octagonal). The reason for this is that by adopting this shape, the gaps can be reduced when placed in the heating section, allowing the mold to be heated more efficiently.

[0033] Furthermore, although the power of the resistance heater varies depending on the size of the mold and the cycle time, it is generally preferable that the power of a single resistance heater be in the range of 5 to 20 kW. The reason for this is that by using such a heater output, the mold can be heated more efficiently without excessive or insufficient heating, and the output can be controlled more precisely according to the temperature state of the mold. Therefore, the power of the resistance heater is more preferably in the range of 8 to 18 kW, and even more preferably in the range of 10 to 15 kW.

[0034] Furthermore, as shown in Figure 3, the resistance heater is preferably fixed to the side of the housing (not shown) via a frame 15a, and has a heating region 15x that is inserted into the heating section (not shown) when the frame 15a is fixed to the housing, and a non-heating region 15y located between the heating region 15x and the housing. Specifically, it is preferable that the electric heating element is arranged along the width direction of the frame, and that the electrodes for passing electric current through the electric heating element are arranged to lead out to the housing side via a non-heating area. The reason for this is that it allows for efficient heating of the air inside the heating section, and by returning the heated air that has been blown onto the mold to the blower section through the non-heated area, the air can be circulated inside the housing, preventing an excessive drop in temperature inside the housing. Furthermore, as shown in Figure 3, it is preferable that the electrodes in the non-heated region are surrounded by a metal cylinder 15e. The reason for this configuration is that, by using this configuration, it is possible to more effectively prevent the electrodes from becoming distorted and short-circuiting with the frame as air passes through the non-heated area.

[0035] Furthermore, as shown in Figure 3, it is preferable that the resistance heating heater is provided with a fixing plate 15f at one end in the width direction of the frame 15a, and that the fixing plate 15f and the housing (not shown) are fastened together with screws, bolts, etc., through fixing holes 15f'. The reason for this is that it allows the resistance heating element to be more easily and securely fixed to the housing.

[0036] Furthermore, as shown in Figure 3, when the resistance heating heater has a heating region 15x and a non-heating region 15y, it is preferable to have a partition wall 15d that divides each region. The reason for this is that it effectively prevents the air heated in the heated area from flowing directly into the unheated area instead of towards the mold. Therefore, it is preferable that the electrodes are fixed to the partition wall via ceramic.

[0037] Furthermore, as shown in Figure 3, the resistance heating heater preferably has a ceramic rod as the core material 15c, and an electric heating element 15b is wound around the core material 15c in a coil shape. The reason for this configuration is that it allows the electric heating element to be inserted into the heating section without bending, and thus effectively heats the air with the electric heating element. Furthermore, this configuration reduces the risk of short circuits or other problems caused by vibrations that could cause the heating element to come into contact with the heating element wall or other resistance heating elements, even when subjected to airflow from the heating element.

[0038] Furthermore, it is preferable to have multiple resistance heating elements. The reason for this configuration is that it allows the air to be heated more quickly. Therefore, it is preferable that the number of resistance heating elements be in the range of 2 to 50, more preferably in the range of 4 to 45, and even more preferably in the range of 8 to 40.

[0039] Furthermore, as shown in Figure 2(a), it is preferable that the resistance heating heaters are inserted and positioned opposite each other along the horizontal plane from both the left and right sides (hereinafter sometimes simply referred to as sides) when viewed from the front. The reason for this configuration is that, by using this setup, the heat from the resistance heater is directly transferred to the mold through the central outlet, effectively preventing excessive heating of a portion of the mold, while also allowing the air passing through the heating section to be heated over a wide area.

[0040] Furthermore, when resistance heating heaters are arranged facing each other on the left and right sides, it is preferable that the distance between the opposing resistance heating heaters on the left and right sides be within the range of 20 to 520 mm. The reason for this spacing is that it makes it less likely to obstruct the airflow towards the central outlet, allowing for a more stable airflow. Therefore, when resistance heaters are arranged facing each other on the left and right sides, it is more preferable to set the distance between the left and right resistance heaters to a value in the range of 40 to 440 mm, and even more preferable to set it to a value in the range of 60 to 360 mm.

[0041] Furthermore, when multiple resistance heaters are provided, it is preferable to set the spacing between the resistance heaters along the length of the central outlet to a value within the range of 5 to 200 mm. The reason for this arrangement is that by using this spacing, the amount of air passing outside the frame of the resistance heater is reduced, allowing the air inside the heating section to be heated more efficiently. Therefore, it is more preferable to set the spacing between the resistance heating heaters to a value within the range of 10 to 150 mm, and even more preferable to set it to a value within the range of 15 to 100 mm.

[0042] Furthermore, when multiple resistance heaters are provided, it is preferable to control the output of each resistance heater simultaneously and under the same conditions, but it is even more preferable to control the output of each resistance heater individually and under different conditions. The reason for this is that by controlling the output of each resistance heater simultaneously and under the same conditions, the output can be adjusted with a simpler control device. On the other hand, by individually controlling the output of each resistance heating heater under different conditions, the output can be varied in each location according to the shape of the mold, etc., allowing for more uniform heating of the mold.

[0043] (3) Inclined surface The heating section is characterized by having an inclined surface 16a that increases the flow path cross-sectional area toward the mold mounting section 12, as shown in Figure 2(a). Specifically, it is sufficient that at least one surface of the flow path toward the mold mounting section is an inclined surface (including a curved surface), but it is preferable that it be, for example, frustoconical, truncated pyramidal, or triangular (trapezoidal columnar) shape. The reason for this is that this shape allows the air introduced from the air blower to be effectively spread across the entire left and right sides of the mold, enabling more uniform heating of the mold. Therefore, when the shape is a truncated pyramidal pyramid, it is more preferable to have three to eight sides, and even more preferable to have four to six sides.

[0044] Furthermore, the heating section has a circular communication port that connects to the air duct, and it is particularly preferable that the shape of the heating section be a truncated square pyramidal shape that slopes outwards in all directions from the surface having the communication port. The reason for this is that this shape allows the air sent from the blower to circulate effectively within the heating section, thus heating the air more effectively. Furthermore, it allows for a uniform air temperature, enabling more efficient and uniform heating of the mold.

[0045] Furthermore, as shown in Figure 4(a), it is preferable to set the angle θ of the inclined surface to a value within the range of 30 to 80° with respect to the direction opposite to the direction of gravity. The reason for this is that, at this angle, turbulence is less likely to occur inside the heating section, allowing the entire mold to be heated more efficiently. Therefore, it is more preferable to set the angle of the inclined surface to a value within the range of 40 to 75° with respect to the direction opposite to the direction of gravity, and even more preferable to set it to a value within the range of 50 to 70°.

[0046] (4) Central air outlet The central outlet is configured to blow heated air, supplied from the heating section, out from below the mold placed on the mold mounting section. Specifically, the central air outlet is preferably a through-hole drilled in the top plate 22 of the heating unit 16, as shown in Figures 2(a) to (b). The reason for this is that an opening for the central air outlet can be formed simply by drilling a hole in the top plate, and consequently, the entire heating section can be made with a simpler structure.

[0047] Therefore, the shape of the central outlet is preferably an opening with a shape such as a rectangle, ellipse, elongated hole, sawtooth, or wave. The reason for this design is that it allows for effective control of the flow rate and velocity from the central outlet. Furthermore, while it is preferable for the central air outlet to be completely open, it is also preferable to cover the opening with a mesh or perforated plate to prevent objects from falling from the mold mounting area or the like into the heating area.

[0048] Furthermore, although not particularly limited, it is preferable that the length L1 of the central air outlet be within the range of 500 to 3000 mm, as shown in Figure 4(b). The reason for this is that this length allows for more efficient heating of the mold while maintaining a uniform temperature throughout the entire mold. Therefore, it is more preferable to set the length L1 of the central air outlet to a value within the range of 800 to 2500 mm, and even more preferable to set it to a value within the range of 1000 to 2000 mm. Figures 4(b) to 4(c) show the view from inside the heating section looking upwards.

[0049] Furthermore, although not particularly limited, it is preferable that the width W1 of the central air outlet be within the range of 10 to 500 mm, as shown in Figure 4(b). The reason for this is that by using this width, the heated air in the heating section can be blown out more efficiently onto the mold without excessive leakage. Therefore, it is more preferable to set the width W1 of the central air outlet to a value within the range of 20 to 400 mm, and even more preferable to set it to a value within the range of 30 to 300 mm.

[0050] Furthermore, as shown in Figures 4(a) to (c), it is preferable to provide a heat shielding member 23 around the central air outlet 16c. Specifically, it is preferable to provide an aluminum plate as a heat shield in the area from the central air outlet to the left and right lateral ducts. The reason for this is that by attaching heat-shielding material around the perimeter, the heat from the resistance heating heater can be effectively reflected, more effectively preventing the heat from being transferred unevenly to the mold via the top plate of the heating section.

[0051] Furthermore, as shown in Figure 4(c), it is preferable to provide heat-shielding members 23' at predetermined intervals along the length. The reason for this is that by not providing a heat shield in the central part where heat tends to concentrate, the temperature is dispersed, allowing the air to be heated more uniformly. Therefore, it is preferable to set the spacing L2 of the heat shielding members to a value within the range of 200 to 2000 mm, more preferably within the range of 300 to 1500 mm, and even more preferably within the range of 400 to 1000 mm.

[0052] (5) Side outlet The side outlets are the parts that blow out heated air supplied from the heating section from the left and right sides of the mold placed on the mold mount. Specifically, these are through-holes located at the ends of multiple upward-extending lateral ducts arranged along the sides of the top plate of the heating section, with openings provided so that the left and right air outlets face each other.

[0053] Furthermore, it is preferable that at least one lateral air outlet be provided on each side. The reason for this configuration is that it allows the sides of the mold to be heated more uniformly. Therefore, it is more preferable to have three or more lateral air outlets on each side, and even more preferable to have six or more. Furthermore, while it is preferable for a single lateral duct to have multiple lateral outlets, it is particularly preferable for a single lateral duct to have only one lateral outlet.

[0054] (6) Louver The louvers are components that control the direction in which heated air is blown out from the heating unit. In other words, it consists of two metal plates arranged parallel to each other at a predetermined distance, with one end acting as a pivot point, allowing each metal plate to swing. Specifically, as shown in Figure 2(a), it is preferable that the louver 24 has a central louver 24a provided on the outlet side of the central air outlet 16c and a lateral louver 24b provided on the outlet side of the lateral air outlet 16d. The reason for this configuration is that heated air can be blown over the entire mold, allowing for more uniform heating of the mold. In this case, it is preferable that the louvers are installed within a range of 10 to 200 mm from each air outlet.

[0055] Furthermore, while the length of the louvers is not particularly limited as long as it is longer than the mold used, it is preferable that they be at least 10 mm longer than the length L1 of the central air outlet (see Figure 4(b)). The reason for this is that by using this length, the direction of airflow can be controlled more efficiently without letting any air escape from the outlet. Therefore, it is more preferable that the length of the central air outlet L1 be 100 mm or longer, and even more preferable that it be 200 mm or longer. Here, the louvers do not have to be continuous in the longitudinal direction; as shown in Figure 1, it is also preferable to have multiple parallel metal plates arranged with a gap of about 10 to 300 mm between them. In this case, the length of the louvers can be expressed as the distance between the ends of the outermost louvers among a row of louvers.

[0056] Furthermore, the spacing between the two metal plates in the louver is not particularly limited as long as it is narrower than the width W1 of the central air outlet (see Figure 4(b)), but it is preferable that it be within the range of 8 to 450 mm. The reason for this is that by using such a spacing, the direction of air blown out from the outlet can be controlled more efficiently along the metal plate. Therefore, it is more preferable to set the spacing between the two metal plates in the louver to a value within the range of 15 to 300 mm, and even more preferable to set it to a value within the range of 25 to 150 mm.

[0057] (7) Variant Furthermore, it is also preferable to change the arrangement of the resistance heating heater 16b in the heating section, as shown in Figures 5(a) to (d). Specifically, as shown in Figure 5(a), it is preferable to have a heating section 17' in which a resistance heating heater 16b is inserted from one side. The reason for this configuration is that it effectively prevents variations in power output between the left and right sides, allowing the mold to be heated more uniformly.

[0058] Furthermore, as shown in Figure 5(b), it is preferable to have a heating section 17'' in which the resistance heating heater 16b is inserted diagonally from the left and right sides along the angle of the inclined surface 16a (see Figure 2). The reason for this configuration is that the inclined surface acts as a heat reflector, allowing the air to be heated more quickly.

[0059] Furthermore, as shown in Figure 5(c), when the mold heating device 10 (see Figure 2) is viewed from one side, it is preferable that the heating section 17'''' has a configuration in which the resistance heating heaters 16b are arranged in a staggered pattern. The reason for this configuration is that it more effectively prevents the temperature difference between the top and bottom of the heating section from widening, which would otherwise cause unintended convection to occur inside the heating section.

[0060] Furthermore, as shown in Figure 5(d), when the mold heating device 10 (see Figure 2) is viewed from one side, it is preferable that the heating section 17'''' is configured such that multiple resistance heating heaters 16b are stacked vertically. In other words, it is preferable to have a configuration in which the resistance heating heaters are arranged in two or more rows, stacked in six rows or less, more preferably in a configuration in which they are stacked in five rows or less, and even more preferably in a configuration in which they are stacked in four rows or less. The reason for this configuration is that it allows for faster heating of the air.

[0061] 6. Other components (1) Slide shutter The mold heating device of the present invention preferably has a slide shutter 26 that slides open and closed from left to right when viewed from the front, as shown in Figures 2(a) to (b). Specifically, the slide shutter is preferably connected to a motor (not shown) via a chain 28a and a gear 28b, as shown in Figure 2(a), and is configured to slide left and right by the rotation of the motor. The reason for this configuration is that it allows for rapid movement of the mold in and out, and more effectively suppresses heat dissipation associated with the opening of the slide shutter. Therefore, when the slide shutter is closed, it is preferable to provide an aluminum plate as a heat shield on the lower surface of the slide shutter to prevent heat from escaping to the outside through the slide shutter.

[0062] (2) Airflow during heating The airflow during heating within the mold heating device of the present invention is not particularly limited, but it is preferable that the heated air, which has been blown from the blower to the heating section and onto the mold, is returned to the blower for reuse. Specifically, as shown in Figure 6, it is preferable to have a configuration that includes a flow path R1 from the air blower 14 to each outlet (16c, 16d) via the resistance heating heater 16b, a flow path R2 blown out from the central outlet and guided downwards to the mold by a louver, a flow path R3 that passes through the lateral duct 20 and blown out from the lateral outlet and guided to the side of the mold by a louver, and a flow path R4 that is blown onto the mold and returns to the intake port 14b. The reason for this configuration is that, once the heated air is blown onto the mold, it can be circulated, and higher temperature air can be blown onto the mold without excessively increasing the output of the resistance heater.

[0063] (3) Temperature during heating Although the temperature inside the mold heating device of the present invention varies depending on the timing and location of measurement, it is preferable that the maximum temperature at the central outlet be within the range of 300 to 500°C. The reason for this is that by setting the temperature to this level, the resin powder sprayed onto the mold can be melted more stably, and excessive heating can be prevented, more effectively preventing the molten resin powder from melting and deforming. Therefore, it is more preferable to set the maximum temperature at the central outlet to a value within the range of 330 to 480°C, and even more preferable to set it to a value within the range of 350 to 450°C. Here, the length L1 of the central air outlet (see Figure 4(b)) was set to 1800 mm and the width to 30 mm, and the temperature change at the central air outlet over time was measured. In this case, the case where heating was performed using resistance heaters (12kW x 20 units) is represented by curve A, and the case where heating was performed using conventional gas combustion heaters is represented by curve B. In both cases, the initial temperature was set to 200°C and the target temperature to 420°C, and the temperature was measured. According to these measurement results, when heated with a gas combustion heater, the temperature rose relatively quickly, but it exceeded the target temperature of 420°C and finally stabilized at the target temperature of 420°C only after 30 minutes from the start of heating. On the other hand, when heated with the resistance heating heater of the present invention, although the temperature rise was relatively gradual, it stabilized at the target temperature of 420°C after 18 minutes from the start of heating. Therefore, it can be understood that using a resistance heating heater allows for more precise temperature control and more efficient heating of the mold.

[0064] [Second Embodiment] The second embodiment, as illustrated in Figure 8, is a powder slush molding machine 50 comprising a mold heating device 10 for heating the mold, a powder slush device 51 for forming a sheet-like material on the heated inner surface of the mold by spraying molding resin while powdering it, a mold cooling device 53 for cooling the mold 13 and the formed sheet-like material, a mold processing device 57 for demolding the cooled sheet-like material from the mold, and a conveying device 52 for moving the mold between its parts along a predetermined conveying direction, wherein the mold heating device 10 has a mold mounting section for holding the mold in a predetermined position within the housing and an air intake port for the air inside the housing The powder slush molding machine 50 is characterized by comprising a blowing section that takes in air and sends it through a blowing duct, and a heating section that communicates with the blowing duct and heats the air sent by the blowing section, wherein the heating section has an inclined surface that expands the flow path cross-sectional area toward the mold mounting section, a central outlet that blows heated air toward the bottom surface of the mold, and a lateral outlet that blows heated air toward the side surface of the mold, and between the inclined surface and the central outlet, one or more elongated resistance heating heaters having a frame with openings at the top and bottom and an electric heating element surrounded by the frame. Hereinafter, embodiments of the powder slush molding machine of the present invention will be described in detail with reference to the drawings as appropriate.

[0065] 1. Sheet-like material This is a molded resin product produced by applying a molding resin to the inner surface of a heated mold, melting it, and then cooling and solidifying it. In other words, there are no particular restrictions on the resin used as the raw material for sheet-like materials (hereinafter sometimes referred to as molding resin), but examples include epoxy resin, urethane resin (including thermoplastic urethane resin), polyester resin (including thermoplastic polyester resin), acrylic resin, polyvinyl chloride resin, olefin resin (including thermoplastic olefin resin), silicone resin, etc., either individually or in combination of two or more. In particular, polyvinyl chloride resin and thermoplastic urethane resin are suitable resins because they have good affinity with the second resin that forms the base layer, provide strong adhesion, and also exhibit excellent low-temperature brittleness.

[0066] Furthermore, although the thickness of the sheet-like material is not particularly limited, it is generally preferable to have a value within the range of 0.5 to 2 mm. The reason for this is that by using this thickness, the heat generated by the mold heating device is easily transferred, allowing for efficient molding of sheet-like materials while maintaining the mechanical strength of the molded sheet-like material. Therefore, the thickness of the sheet-like material is more preferably in the range of 0.8 to 1.8 mm, and even more preferably in the range of 1 to 1.5 mm.

[0067] Here, the melting point of the molding resin is not particularly limited as long as it is lower than the temperature at which the mold heating device is heated, but it is preferably in the range of 150 to 400°C. The reason for this is that by setting such a melting point, when the material is sprayed onto a mold heated in the heating section, it melts easily, forming a sheet-like material of uniform thickness. Therefore, the melting point of the molding resin is more preferably in the range of 180 to 350°C, and even more preferably in the range of 200 to 300°C.

[0068] 2. Mold heating device This is a device for heating a mold to the temperature at which the molding resin, or resin powder, melts. Furthermore, since it is preferable to have the same configuration as the mold heating device of the first embodiment, we will omit further explanation of the overlapping parts.

[0069] 3. Powder slush machine A powder slush machine is a device used to melt and adhere resin powder to the molded surface of a heated mold. Specifically, although not particularly limited, such a powder slush apparatus preferably includes a reservoir tank into which resin powder is introduced, and which is positioned with the molding surface of the mold facing the opening of the reservoir tank. Furthermore, the reservoir tank is configured to rotate vertically. With the mold integrally connected, the mold rotates so that it is positioned downwards and the reservoir tank upwards, causing the resin powder in the reservoir tank to fall and adhere to the molding surface of the mold.

[0070] Furthermore, in order to improve the dispersibility of the resin powder in the reservoir tank and to form a resin film (sheet-like material) of uniform thickness, it is preferable to provide a space below the reservoir tank that is partitioned by a mesh member such as canvas. The reason for this is that air can be introduced into the space, allowing the resin powder to become fluid. Therefore, it is more preferable that the upper part of the space is composed of a perforated member (mesh member) and that the resin powder is stirred up by the introduced air.

[0071] Furthermore, when inverting the mold including the frame member, it is preferable to provide a rectangular frame having a predetermined thickness (height) between the mold and the reservoir tank so that a resin film can be formed only on the desired molding surface of the mold. Therefore, it is preferable to fill the gap between the mold and the reservoir tank by, for example, constructing the lower part of the frame from aluminum and the upper part of the frame from a combination of silicone rubber / fluororesin film.

[0072] 4. Mold cooling device A mold cooling device is a device used to cool a mold, including its frame components, in order to cure the resin film. In other words, the configuration is not limited as long as it can cool the resin to a temperature below the melting point, but it is preferable to have an air cooling device that blows air onto the mold, or a water cooling device that sprays water onto the mold.

[0073] 5. Conveying device The transport device is not particularly limited, but it is preferably a robot-type transport device (including chain blocks, etc.) that includes at least a gripping section for gripping the mold, an arm section that can extend and retract while gripping the mold, and a rotating section that rotates radially. The reason for this is that such a conveying device can efficiently move the mold while gripping it, rotating radially, between at least the mold heating device which heats the mold with an electric heating element, the powder slush device, and the mold cooling device. Furthermore, the arm extends and retracts while gripping the mold, allowing the mold to be placed in a predetermined location.

[0074] 6. Other devices (1) Preheating device The powder slush molding machine of the present invention preferably has a preheating device that is different from the mold heating device described above, and which heats the mold to a temperature lower than the temperature required by the powder slush device before it is transported to the mold heating device. Specifically, the preheating device preferably includes various preheating electric heaters such as far-infrared heaters, near-infrared heaters, and resistance heaters, as well as a blower fan. The reason for this is that by preheating the mold to a certain temperature, the processing time in the heating device can be shortened, which in turn can further reduce the cycle time of the powder slush molding machine.

[0075] Furthermore, it is preferable to provide a preheating device in the conveying device. In other words, the mold is transferred from the mold processing device to the mold heating device by a transfer device (for example, a crane), and it is preferable that the transfer device be configured to heat at least the outer surface of the mold during the transfer. More specifically, it is preferable that the preheating device of the conveying device has the same configuration as the preheating device, but from the viewpoint of miniaturization, it is even more preferable that it is equipped with multiple far-infrared heaters so as to cover the mold in a dome shape while it is being conveyed.

[0076] (2) Mold changing device Furthermore, the powder slush molding machine of the present invention preferably further comprises a mold changing device 55, as shown in Figure 8. The reason for this is to use such a mold changing device to change molds for molding different types of two-color molded sheet materials during powder slush molding, or to address situations where mold damage occurs during powder slush molding. In other words, even in such cases, the mold can be changed while the powder slush molding machine is still in operation.

[0077] On the other hand, when powder slush molding is being performed, such a mold changing device also serves as a temporary base for the cooling device. Therefore, it is preferable that such a mold changing device is equipped with a support base for placing the mold, and that the position of the support base is movable by external control.

[0078] (3) Demolding equipment Furthermore, the powder slush molding machine of the present invention preferably further includes a demolding device as an apparatus for performing a demolding operation to remove the powder slush-molded sheet-like material from the mold. Specifically, it is preferable that the device is configured to grip a mold on which a sheet-like material has been formed, which has been transported by a conveying device, and to be able to move it as desired. The reason for this is that it allows for quick demolding, and after demolding, the mold can be cleaned, and the mold from which the sheet material has been removed can be used directly for the next molding process. [Industrial applicability]

[0079] As described above, the mold heating device and powder slush molding machine of the present invention, by providing a predetermined heating section, can efficiently and uniformly heat the mold without using a combustion heater. Therefore, by precisely controlling the temperature inside the enclosure, it is possible to eliminate overheating or underheating of the mold, and it is expected that this will result in a more energy-efficient mold heating device. Furthermore, by incorporating sensors to measure the mold temperature, it is expected that the mold heating device can be made capable of heating the mold more uniformly by adjusting the output of the resistance heater according to the state of the mold temperature. Furthermore, by using such a mold heating device in a powder slush molding machine and equipping the outlet with louvers, it is expected that a sheet-like material with more uniform thickness can be obtained. [Explanation of Symbols]

[0080] 10: Mold heating device 11: Mold 12: Mold mounting section 14: Blower unit 15a: Frame 15b: Electric heating element 15c: Ceramic rod 15d: Bulkhead 15x: heating area 15y: Non-heating area 16: Heating part 16a: Inclined surface 16b: Resistance heating element 16c: Central air outlet 16d: Side outlet 20: Side duct 22: Top plate 24: Luba 26: Slide shutter 50: Powder slush molding machine 51: Powder slush device 52: Conveying device 53: Mold cooling device 55: Mold changing device 57: Mold processing equipment

Claims

1. A mold heating device for heating a mold, A mold mounting section for holding the mold in a predetermined position within the housing, A ventilation unit that takes in air from inside the housing through an air intake and sends the air through a ventilation duct, It is connected to the aforementioned air duct and includes a heating section for heating the air supplied by the air supply section, The heating section has an inclined surface that increases the flow path cross-sectional area toward the mold mounting section, a central outlet that blows the heated air toward the lower surface of the mold, and a lateral outlet that blows the heated air toward the side surface of the mold. A mold heating apparatus characterized in that, between the inclined surface and the central air outlet, one or more elongated resistance heating heaters are arranged, each having a frame with openings at the top and bottom and an electric heating element surrounded by the frame.

2. The mold heating apparatus according to claim 1, characterized in that the heating section has a circular communication port that communicates with the air duct, and the shape of the heating section is a truncated square pyramidal shape that slopes in all directions from the surface having the communication port.

3. The mold heating apparatus according to claim 1 or 2, wherein the resistance heating heater is fixed to the side of the housing via the frame, and has a heating region that is inserted into the heating section when the frame is fixed to the housing, and a non-heating region located between the heating region and the housing.

4. The mold heating apparatus according to claim 1 or 2, characterized in that the resistance heating heater is in the form of a wound wire in which the electric heating element is wound around a ceramic rod as a core material.

5. The mold heating apparatus according to claim 1 or 2, characterized in that the heating section is provided with a heat shielding member around the central outlet.

6. The mold heating apparatus according to claim 1 or 2, characterized in that the heating section has louvers at the central outlet and the lateral outlet for adjusting the direction in which the heated air is blown.

7. The mold heating apparatus according to claim 1 or 2, characterized in that the mold mounting section, the resistance heating heater, and the inclined surface are arranged in order along the direction of gravity.

8. A mold heating device for heating the mold, A powder slush device that sprays molding resin while powdering it to form a sheet-like material on the heated inner surface of the mold, The mold and a mold cooling device for cooling the molded sheet-like material, A mold processing apparatus for demolding a cooled sheet-like material from the mold, A powder slush molding machine comprising a conveying device for moving the mold between its parts along a predetermined conveying direction, The mold heating device includes a mold mounting section for holding the mold in a predetermined position within the housing, A ventilation unit that takes in air from inside the housing through an air intake and sends the air through a ventilation duct, It is connected to the aforementioned air duct and includes a heating section for heating the air supplied by the air supply section, The heating section has an inclined surface that increases the flow path cross-sectional area toward the mold mounting section, a central outlet that blows the heated air toward the lower surface of the mold, and a lateral outlet that blows the heated air toward the side surface of the mold. A powder slush molding machine characterized in that, between the inclined surface and the central air outlet, one or more elongated resistance heating heaters are arranged, each having a frame with openings at the top and bottom and an electric heating element surrounded by the frame.

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