Resin melter and plunger-type injection molding machine equipped therewith

Abstract

To provide a resin melter equipped with a melting hole that has superior wear resistance compared to conventional models, and a plunger-type injection molding machine equipped with the same. [Solution] This is a resin melter 2 incorporated into a plunger-type injection molding machine. The resin melter 2 has a melter body 20 with a plurality of melting holes 29 arranged axially, each consisting of through holes whose opening area decreases from the inlet to the outlet. An inner tube 7, which has better wear resistance than the material constituting the melter body 20, is disposed on the inner surface of the melting holes 29. Preferably, the melting holes 29 have a tapered shape in which the inner diameter decreases from the inlet to the outlet, and the inner tube 7 has a tapered shape that conforms to the inner surface of the melting holes 29. Preferably, a locking portion 298 is provided near the outlet of the melting hole 29 of the melter body 20, which abuts against the outlet end 71 of the inner tube 7.

Description

Technical Field

[0001] The present invention relates to a resin melter and a plunger-type injection molding machine provided with the same.

Background Art

[0002] As injection molding machines used for injection molding of resin products, there are a screw type equipped with a kneading screw and a plunger type equipped with a plunger for pressing resin pellets. Among these, the plunger-type injection molding machine is very compact compared to the screw type, has a relatively simple device configuration, and can be effectively utilized for trial products and small-lot, multi-variety production.

[0003] The plunger-type injection molding machine has a basic configuration in which resin pellets introduced into a cylinder are pressed by a plunger toward a resin melter, and the resin melted in the resin melter is injected from a nozzle at the tip by the pressing force from the plunger. In this basic configuration, as a resin melter (hereinafter, simply referred to as "melter" as appropriate) for melting resin pellets, for example, a melter having a configuration with a plurality of melting holes described in Patent Document 1 has been put into practical use.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The multiple melting holes provided in the melting chamber are through-holes whose opening area decreases from the inlet to the outlet. The resin pellets introduced into these melting holes are heated by heat transfer from the inner surface of the melting holes, and the pressing force from the plunger acts on the material, causing it to gradually melt and become completely molten near the outlet of the melting hole before being discharged through the nozzle. The pressing force from the plunger is constantly applied to the resin pellets. Therefore, during the operation of the plunger-type injection molding machine, the upper end surface of the melting chamber (the surface where the inlet of the melting hole opens) and the inner surface of the melting hole are constantly in contact with the solid or molten resin, causing friction, and thus wear resistance is required.

[0006] Conventional melting vessels prioritize thermal conductivity, and materials such as copper and beryllium copper are used. These materials have sufficiently high hardness compared to the resins commonly used in injection molding and exhibit a certain degree of wear resistance. On the other hand, in some cases, resins containing relatively hard fillers are injected, and in these cases, it has been observed that the opening edges of the melting holes and the inner surfaces of the melting holes gradually wear down due to the effects of the fillers. Therefore, there is a need for the development of melting vessels with melting holes that have superior wear resistance compared to conventional vessels.

[0007] This invention was made in view of the above background, and aims to provide a resin melter equipped with a melting hole that has superior wear resistance compared to conventional melters, and a plunger-type injection molding machine equipped with the same. [Means for solving the problem]

[0008] One aspect of the present invention is a resin melter incorporated into a plunger-type injection molding machine, The resin melting device is Multiple molten holes penetrating in the axial direction are spaced apart on multiple concentric circles centered on the axis of the resin melter. It has a melting body provided, The melting vessel body is constructed by connecting two or more separate parts with different wear resistances in the axial direction. Within the multiple molten holes formed by penetrating all of the aforementioned components, an inner tube made of a metal material with better wear resistance than the least wear-resistant component constituting the melting vessel body is provided. It is located in the resin melting chamber. [Effects of the Invention]

[0009] The aforementioned resin melter is equipped with an inner tube on the inner surface of the melting hole of the melter body. This inner tube has superior wear resistance compared to the material that makes up the melter body, i.e., the material that makes up the inner surface of the melting hole. Therefore, even when melting resins containing hard fillers, for example, wear of the melting hole can be suppressed, and the lifespan of the resin melter can be significantly improved. [Brief explanation of the drawing]

[0010] [Figure 1] A longitudinal cross-sectional view of the plunger-type injection molding machine in Example 1. [Figure 2] A perspective view of the plunger-type injection molding machine in Example 1. [Figure 3] A longitudinal cross-sectional view of the melting machine body in Example 1. [Figure 4] Plan view of the inlet component in Example 1. [Figure 5] A perspective view of the inlet component in Example 1. [Figure 6] A perspective view of the first central component in Example 1. [Figure 7] A perspective view of the second central component in Example 1. [Figure 8] A perspective view of the exit component in Example 1. [Figure 9] A perspective view of the nozzle holder component in Example 1. [Figure 10] Front view of the inner tube in Example 1. [Figure 11] Plan view of the inner tube in Example 1. [Figure 12] Front view of the heater in Example 1. [Figure 13] A longitudinal cross-sectional view of the resin melting machine in Example 1. [Figure 14] Bottom view of the first insulation material in Example 1. [Figure 15] A longitudinal cross-sectional view of the melting machine body in Example 2. [Figure 16] An explanatory diagram showing a modified example of the locking portion provided in the molten hole in Example 3. [Figure 17]Explanatory drawing showing an example of shape modification of the melting hole and the inner tube in Example 4. [Figure 18] Explanatory drawing showing an example of shape modification of the melting hole and the inner tube in Example 5.

Mode for Carrying Out the Invention

[0011] The melting vessel body constituting the resin melting device may be composed of a single part, or may be composed of a combination of a plurality of parts as described later. And, as the inner tube disposed in the melting hole, when the melting vessel body is composed of a single part, an inner tube made of a material having better wear resistance than that single part is adopted. When the melting vessel body is composed of a combination of a plurality of parts, an inner tube made of a material having better wear resistance than the part with the lowest wear resistance is adopted.

[0012] The melting hole is a through hole whose opening area decreases from the inlet to the outlet. Specifically, the melting hole can take various forms as long as the opening area of the outlet is smaller than that of the inlet. For example, it can be in the form of reducing the inner diameter stepwise, or in the form of combining a straight part and a tapered part. In this case, an inner tube having the same shape can be arranged.

[0013] More preferably, the melting hole has a tapered shape with an inner diameter decreasing from the inlet to the outlet, and the inner tube preferably has a tapered shape following the inner surface of the melting hole. Thereby, the manufacture of the inner tube and the work of disposing the inner tube become relatively easy, and the resin can smoothly pass through the melting hole, and problems such as resin remaining and stagnating in the melting hole can be suppressed.

[0014] Also, it is preferable that a locking portion axially contacting the inner tube is provided in the melting hole of the melting vessel body to prevent the inner tube from being displaced to the outlet side in the melting hole. Thereby, over time, it is possible to reliably prevent the phenomenon that the inner tube is pushed by the resin pellets and is displaced to the outlet side in the melting hole, and a stable arrangement state of the inner tube can be maintained.

[0015] Various forms can be adopted for the locking portion described above. For example, a locking portion can be provided near the outlet of the melting hole in the melting vessel body, which abuts against the outlet end of the inner tube from the outlet side. In this case, a tapered tube can be used as the inner tube, and displacement of the inner tube can be reliably prevented.

[0016] Alternatively, an inner tube-side locking portion, consisting of a stepped or large-diameter portion projecting outward, can be provided at any axial position on the outer surface of the inner tube, and a locking portion that engages with the inner tube-side locking portion from the outlet side can be provided on the inner surface of the molten hole. In this case, it is preferable for manufacturing and structural stability to provide the inner tube-side locking portion and the locking portion near the inlet side of the molten hole. Furthermore, various other configurations can be adopted to prevent the inner tube from shifting position over time.

[0017] Furthermore, as will be described later, when the melting machine body is constructed by connecting multiple parts in the axial direction, by selecting a material that can be welded to the inner tube as the material for the inlet part that provides the entrance to the melting hole, the inlet end of the inner tube and the entrance to the melting hole can be firmly fixed by welding. In this case, structural stability can be further improved. As a welding method, it is preferable to use, for example, laser welding.

[0018] The inner tube is preferably made of stainless steel. While the inner tube can be constructed from various materials, it is preferable to use a metal material considering manufacturing and installation work. In particular, by using stainless steel, a structure with excellent not only wear resistance but also corrosion resistance can be obtained. As for the stainless steel, most commercially available stainless steels can be used, but pipe materials with excellent swaging workability, such as austenitic or ferritic stainless steel, are preferred. When copper or a copper alloy is used as the material for the melting machine body, austenitic stainless steel, such as general-purpose SUS304, is preferred. Since SUS304 has a coefficient of thermal expansion that is almost the same as that of copper or a copper alloy, it can improve the structural stability of the melting machine body.

[0019] Furthermore, while not essential, surface modification treatment of stainless steel pipes is preferable to further enhance wear resistance. Specifically, this can include nitriding treatment using salt baths, ions, or gases, or coating treatments using materials such as TiN, CrN, or DLC. In particular, to modify the surface deep into the pores of the stainless steel pipe, it is preferable to create a hardened layer on the surface layer in which nitride compounds are finely dispersed by gas nitriding treatment.

[0020] Alternatively, a hardened film such as a chromium plating film or a nickel plating film can be formed on the inner surface of the molten hole by chemical means and used as the inner tube. In this case, if the molten machine body is formed from a single component, it is expected that the inner tube will function adequately. On the other hand, if the molten machine body is constructed by combining multiple components in the axial direction, there is a risk that defects may occur in the hardened film at the interface. Therefore, when the molten machine body is constructed from multiple components, it is preferable to use a metal tube as the inner tube.

[0021] The melting body is constructed by connecting at least two or more separate parts in the axial direction, and it is preferable that the inlet part located at the upstream end is made of a material with better wear resistance than the other parts. First, by constructing the melting body from two or more parts, the processing length when forming the melting hole can be shortened, and the processability can be greatly improved.

[0022] Furthermore, by constructing the melting pot body from multiple parts, it becomes possible to change the material depending on the part. In this case, for the inlet part, it is effective to use a material with superior wear resistance compared to other parts, from the viewpoint of improving the wear resistance of the entire inlet surface, which is the axial end face where the inlet of the melting hole is opened. Also, for parts downstream of the inlet part, since the inner tube is present on the inner surface of the melting hole, it is not necessary to consider wear resistance, and a material with excellent heat transfer characteristics can be used, prioritizing increased heating capacity. Therefore, by constructing the melting pot body by connecting parts in the axial direction, it becomes possible to adopt an optimal configuration in terms of both processing and performance.

[0023] Furthermore, stainless steel is preferably used as the material for inlet components where wear resistance is particularly required. This allows for a configuration that is excellent not only in wear resistance but also in corrosion resistance. Most commercially available stainless steels can be used for inlet components, but if other components are made of copper or copper alloys, austenitic stainless steel, such as general-purpose SUS304, is preferred, as is the case with the inner pipe. Since SUS304 has a coefficient of thermal expansion that is almost the same as that of copper or copper alloys, it can improve the structural stability of the melting machine body. Also, when inlet components are made of stainless steel, it is preferable to apply the same surface modification treatment as described above for the inner pipe.

[0024] Furthermore, it is preferable that the melting vessel body is integrally provided with a cylindrical tip piece that is erected axially from the outer circumference of the inlet surface, which is the axial end surface through which the inlet of the melting hole is opened. In this case, the inlet surface and the inner surface of the cylindrical tip piece are connected without any gaps, and the resin pellets pressed by the plunger at the inlet side of the melting vessel can be reliably received, preventing problems such as resin leakage.

[0025] The melting holes are arranged at intervals on a plurality of concentric circles centered on the axis of the melting vessel body, and it is preferable that a central projection protruding upstream is provided on the axis of the melting vessel body without the melting holes. The melting holes provided in the melting vessel body can also be provided on the central axis of the melting vessel, but by adopting the above configuration and providing a central projection protruding upstream without providing melting holes on the central axis of the melting vessel, it is expected that the pressed resin pellets will flow smoothly from the center to the outer circumference, and since the central projection itself is heated by heat transfer, it is possible to obtain the effect of raising the temperature of the resin near the center. The central projection can be, for example, a shape close to a cone, with the diameter decreasing towards the tip, and the tip surface being a smooth hemisphere.

[0026] The resin melter described above is used by being incorporated into a plunger-type injection molding machine. As will be detailed in the embodiments, the plunger-type injection molding machine has at least a cylinder equipped with a pellet supply port, a plunger arranged to move axially back and forth within the cylinder, a drive unit for moving the plunger, a resin melter for melting resin pellets supplied from the pellet supply port, and a nozzle for discharging the molten resin. [Examples]

[0027] (Example 1) Embodiments relating to a resin melter and a plunger-type injection molding machine equipped therewith will be described with reference to the drawings. As shown in Figures 1 and 2, the plunger-type injection molding machine 1 of this example includes at least a cylinder 10 equipped with a pellet supply port 12, a plunger 3 arranged to move axially back and forth within the cylinder 10, a drive unit 4 for moving the plunger 3, a resin melter 2 for melting resin pellets supplied from the pellet supply port 12, and a nozzle 5 for discharging the molten resin.

[0028] [cylinder] As shown in Figure 1, the cylinder 10 has a cylindrical shape and has a pellet supply port 12 in the middle of its longitudinal direction (vertical direction). Inside the cylinder 10, a plunger 3 is positioned above the pellet supply port 12, and a melter 2 is positioned below it. A supply pipe 13 is connected to the outside of the pellet supply port 12 of the cylinder 10, and a pellet hopper 14, which is a container for storing resin pellets, can be detachably connected to its upper end opening 130. The pellet hopper 14 can be, for example, one with a shape similar to a beverage PET bottle, and the upper end opening 130 of the supply pipe 13 can be provided with a female threaded portion that can be screwed with a male threaded portion similar to the opening of a PET bottle, thereby enabling a detachable connection.

[0029] [Plunger and drive unit] As shown in Figure 1, the plunger 3 has a cylindrical shape and is arranged within the cylinder 10 so as to be movable in the axial direction. A solid tip is formed at the tip (lower end) of the plunger 3, and its tip surface is configured to function as a pressing surface 32. A shaft housing hole 33 extending in the direction of the centerline is formed at the rear end (upper end) of the plunger 3, and a shaft connecting member 34 having a threaded hole 340 is fixed to its open end, and the drive shaft 41 of the drive unit 4, which will be described later, is screwed into the threaded hole 340.

[0030] As shown in Figures 1 and 2, the drive unit 4, which controls the forward and backward position of the plunger 3, is supported together with the plunger 3 on a frame portion 40 located above the cylinder 10. The frame portion 40 has a lower plate frame 401 that engages with the outer peripheral surface near the upper end of the cylinder 10, a vertical plate frame 402 erected from its side end face, and an upper plate frame 403 extending horizontally from the upper end of the vertical plate frame 402. Two guide poles 404 are arranged in the space enclosed by these frames to guide the forward and backward movement of the plunger 3. Each of the two guide poles 404 is fitted with a slidable sleeve 405, and the sleeves 405 and the shaft connecting member 34 are connected via a bracket 406.

[0031] The upper end of the drive shaft 41, which is screwed into the shaft connecting member 34 of the plunger 3, protrudes upward from a through hole in the upper plate frame 403, and a large gear 431 that receives the driving force is disposed at its tip. The motor 45, which serves as the driving source, is fixed in a suspended state from the upper plate frame 403 as shown in Figure 2, and its motor shaft 451 protrudes upward from a through hole in the upper plate frame 403, and a small gear 432 that meshes with the large gear 431 is disposed at its tip.

[0032] In this structure, the driving force of the motor 45 is transmitted to the drive shaft 41 via the small gear 432 and the large gear 431. As the drive shaft 41 rotates, the plunger 3 moves axially without rotating via the shaft connecting member 34 that is screwed onto it. At the same time, the blanket 406 and sleeve 405 also move along the guide pole 404 together with the plunger 3 to guide the position of the plunger 3.

[0033] [Resin melting machine] As shown in Figure 3, the melting furnace 2 includes a melting furnace body 20. As shown in Figures 3 to 9, the melting furnace body 20 in this example is constructed by connecting multiple separate parts in the axial direction. Specifically, it is constructed by connecting an inlet part 21, a first central part 22, a second central part 23, an outlet part 24, and a nozzle holder part 25 from the axial upstream side.

[0034] The inlet component 21 is formed from SUS304 by machining or other processes. As shown in Figures 3 to 5, the inlet component 21 has a disc-shaped base 210 in which multiple molten holes 29 are formed at intervals on multiple concentric circles centered on the axis. Each molten hole 29 is provided in a tapered shape in which the inner diameter smoothly decreases from the upstream side to the downstream side.

[0035] The inlet part 21 integrally includes a cylindrical tip piece 212 that is erected axially from the outer circumference of the inlet surface 211, which is the axial end surface that opens the inlet of the molten hole 29 in the base portion 210 of the inlet part 21. The cylindrical tip piece 212 has a thick-walled portion at the base end and a thinner-walled portion at the tip end, and a male screw (not shown) for engaging with the cylinder 10 is provided on its outer circumference 213.

[0036] A central projection 214 is provided on the axis of the inlet component 21, protruding upstream without having a melting hole. The central projection 214 has a conical shape with a hemispherical tip, and the hemispherical tip is positioned to face the center of the pressing surface 32 of the plunger 3.

[0037] The inlet part 21 has an upper flange portion 215 located on the outer circumference side of the cylindrical tip piece 212 of the base portion 210, which has a plurality of through holes that penetrate axially. The upper flange portion 215 has fastening holes 26 for inserting fixing bolts and heater insertion holes 27 for inserting the heater 6, which will be described later, alternately provided in the circumferential direction. The heater insertion holes 27 have a counterbore portion 275 on the inlet side that is larger in diameter than the through holes.

[0038] As shown in Figures 3 and 6, the first central component 22 is a cylindrical component that is thicker than the inlet component 21 and is formed from tellurium copper by machining or other processes. The first central component 22 has the same external dimensions as the inlet component 21 and has the same number of melting holes 29 on the same axis as the inlet component 21. Each melting hole 29 is provided in a tapered shape, with the inner diameter decreasing from the upstream side to the downstream side, so as to create a smooth tapered shape that is continuous with the melting holes 29 of the inlet component 21.

[0039] Near the outer peripheral end of the first central component 22, fastening holes 26 and heater insertion holes 27, which are connected to the fastening holes 26 and heater insertion holes 27 provided in the upper flange portion 215 of the inlet component 21, are arranged alternately in the circumferential direction and penetrate through in the axial direction.

[0040] As shown in Figures 3 and 7, the second central component 23 is a cylindrical component with the same thickness as the first central component 22 described above, and is formed from tellurium copper by cutting or other processes. The second central component 23 has the same external dimensions as the inlet component 21 and the first central component 22, and has the same number of melting holes 29 on the same axis as the melting holes 29 provided in the inlet component 21 and the first central component 22. Each melting hole 29 is provided in a tapered shape with the inner diameter decreasing from the upstream side to the downstream side so as to create a smooth tapered shape that is continuous with the melting holes 29 of the inlet component 21 and the first central component 22.

[0041] Near the outer peripheral end of the second central component 23, fastening holes 26 and heater insertion holes 27, which are connected to the upper flange portion 215 of the inlet component 21 and the fastening holes 26 and heater insertion holes 27 provided in the first central component 22, are arranged alternately in the circumferential direction and penetrate through in the axial direction.

[0042] As shown in Figures 3 and 8, the outlet component 24 has a disc shape that is thinner and has a smaller outer diameter than the first and second central components 23 and 24, and is formed from SUS304 by machining or other processes. The outlet component 24 has the same number of melting holes 29 on the same axis as the melting holes 29 provided in the upstream component. Each melting hole 29 is provided in a tapered shape with the inner diameter decreasing from the upstream side to the downstream side, so as to create a smooth tapered shape that is continuous with the melting holes 29 of the inlet component 21 and the first and second central components 22 and 23.

[0043] As shown in Figure 3, the outlet component 24 is equipped with a stepped, reduced-diameter locking portion 298 at the outlet-side opening of the melting hole 29. This locking portion 298 abuts against the outlet-side end 71 of the inner tube 7, which will be described later, and prevents the inner tube 7 from sliding toward the outlet side of the melting hole 29.

[0044] As shown in Figures 3 and 9, the nozzle holder component 25 is a component having the same external dimensions as the inlet component 21 and the first and second central components 22 and 23 described above, and is formed by machining or other processes using SUS304. The nozzle holder component 25 has a circular recess 251 for accommodating the outlet component 24, and has a lower flange portion 252 on its outer circumference. The lower flange portion 252 is provided with fastening screw holes 28 and heater insertion holes 27, which are connected to the fastening holes 26 and heater insertion holes 27 provided in the inlet component 21 and the first and second central components 22 and 23, respectively, and are arranged alternately in the circumferential direction and penetrate through in the axial direction. The fastening screw holes 28 are provided with female threads that can be screwed into the tip of a bolt (not shown) inserted through the fastening holes 26 of the inlet component 21 and the first and second central components 22 and 23.

[0045] Downstream of the lower flange portion 252, a cone portion 253 is provided, which has an inner diameter that gradually decreases and a nozzle engagement hole 255 at its lower end for connecting the nozzle 5. The nozzle engagement hole 255 is provided with an internal thread, which is configured to engage with an external thread provided on the outer circumferential surface of the base end of the nozzle 5. The nozzle 5 has a discharge port 53 at its tapered tip for discharging resin. The lower flange portion 252 houses the outlet component 24 and connects to other components 21-23, thereby forming a resin reservoir space inside the cone portion 253 for storing molten resin.

[0046] As described above, the melting pot body 20 is composed of an inlet part 21, a first central part 22, a second central part 23, an outlet part 24, and a nozzle holder part 25 arranged in a row from the axial upstream side. The entire assembly is integrated by inserting eight bolts (not shown) into eight fastening holes 26 and screwing them into fastening screw holes 28.

[0047] The integrated melting body 20 has a plurality of melting holes 29 formed by penetrating the inlet part 21, the first central part 22, the second central part 23, and the outlet part 24. An inner tube 7 with excellent wear resistance is inserted and disposed on the inner surface of these melting holes 29. As described above, the melting holes 29 have a tapered shape in which the inner diameter decreases from the inlet to the outlet. As shown in Figures 10 and 11, the inner tube 7 is a tapered tube with a circular cross-section and has a tapered shape that smoothly decreases in diameter from the inlet end 72 to the outlet end 71, following the inner surface of the melting hole 29. The inner tube 7 is press-fitted into the melting hole 29, and the inner surface of the melting hole 29 and the outer surface of the inner tube 7 are in sufficient contact. The outlet end 71 of the inner tube 7 abuts against the locking part 298 (Figure 3) of the outlet part 24, restricting its movement toward the outlet.

[0048] In this example, the inner tube 7 is made of SUS304 stainless steel. The inner tube 7 can also be made of metals other than stainless steel or other materials, but austenitic stainless steel is preferred because it combines corrosion resistance, wear resistance, and an appropriate coefficient of thermal expansion. In this example, in order to further improve wear resistance, a hardened layer is provided on the surface of the inner tube 7, in which fine nitride compound particles formed by gas nitriding are dispersed.

[0049] [heater] Next, as shown in Figures 3 and 13, the melting body 20 in this example has multiple heater insertion holes 27 extending radially outward from the area where the melting holes 29 are located, with the aforementioned heater insertion holes 27 penetrating axially. The heater insertion holes 27 penetrate from the upper end to the lower end of the melting body 20, passing through all of the inlet component 21, the first central component 22, the second central component 23, and the outlet component 24, so that all components can be heated by the heater 6. As shown in Figure 13, the heater 6, which consists of a rod-shaped heater, is inserted into the heater insertion hole 27.

[0050] As shown in Figure 12, the heater 6 is a type of cartridge heater, comprising a round rod-shaped heating element 61, lead wires 62 and 63 for supplying power to the heating element 61, and a heater base 65 that covers these connections. The heating element 61 has a structure in which a heating coil is wound around a rod-shaped ceramic core, and its outer circumference is covered with a metal tube via an insulating material. The heater base 65 has a configuration in which the lead wires 62 and 63 are connected to both ends of the heating coil of the heating element 61, respectively, and covers them in an insulated state, while also leading out the lead wires 62 and 63 in a direction perpendicular to the axial direction of the heating element 61.

[0051] While a heater 6 with a built-in temperature sensor could also be used, in this example, as will be described later, a configuration in which multiple thermocouples are separately placed on the melting body 20 is adopted, so a heater 6 without a built-in temperature sensor is used.

[0052] The heating element 61 of the heater 6 is designed with the maximum outer diameter possible for insertion into the heater insertion hole 27 provided in the melting pot body 20. In actual installation, thermal conductive grease or the like is placed in the small gap between the outer surface of the heating element 61 and the inner surface of the heater insertion hole 27 to improve heat transfer performance between the two.

[0053] The heater base 65 of the heater 6 has a larger diameter than the heating element 61 and is configured so that a portion of it fits within the counterbore 275 of the heater insertion hole 27 of the melting vessel body 20. This configuration restricts the placement of the heating element 61. In this example, the heating element 61 has a length that is almost the same as the total length of the melting vessel body 20. When viewed from a direction perpendicular to the axial direction, the heating element 61 is positioned in an axial location that faces an area of ​​more than 90% of the total length of the melting hole 29.

[0054] In other words, the heating element 61 of the heater 6 is positioned to face all of the inlet component 21, the first central component 22, the second central component 23, and the outlet component 24 when viewed from a direction perpendicular to the axial direction, and is configured to efficiently heat all of these components. In particular, the inlet component 21, which has a cylindrical tip piece 212 at the upstream end of the melting machine body 20, can also be sufficiently heated, and the resin pellets can be properly heated before being inserted into the melting hole 29.

[0055] In this example, eight heater insertion holes 27 are provided evenly in the circumferential direction, and eight heaters 6 are evenly arranged. This configuration allows almost the entire melting body 20, from the upstream to the downstream side, to be heated evenly from the outer circumference.

[0056] The lead wires 62 and 63 of each heater 6 are connected to a heater control device (not shown) for temperature control. In this example, multiple thermocouples are provided for temperature measurement of each part necessary for temperature control. Specifically, thermocouple insertion holes (not shown) are provided on the side of the first central component 22, the second central component 23, and the nozzle holder component 25 of the melting furnace body 20, and thermocouples are placed there to acquire temperature information.

[0057] [Insulation material] As shown in Figure 13, the outer periphery of the melting vessel body 20 is surrounded by an insulating material 8. The insulating material 8 is constructed by combining separate parts that are divided in the axial direction, and the overall shape is roughly cylindrical. Specifically, the insulating material 8 is composed of the first to sixth insulating materials 81 to 86 connected in the axial direction. In this example, the insulating material 8 is made of calcium silicate and is formed by machining.

[0058] As shown in Figures 13 and 14, the first insulation material 81 has an annular shape and its lower surface 810 has a bolt counterbore portion 811 for accommodating the bolt heads of bolts inserted into fastening holes 26 to integrate the melting vessel body 20, and a heater counterbore portion 812 for accommodating the heater base 65 and lead wires 62 and 62 of the heater 6. In Figure 13, a cross-section of the entire melting vessel 2 is shown at a position corresponding to the cross-section of line AA in Figure 14, and the first insulation material 81 is shown in a state cut along the cut surface passing through the heater counterbore portion 812. The first insulation material 81 is arranged to surround the outer circumference of the cylindrical tip piece 212 of the inlet part 21 of the melting vessel body 20, and is designed to provide a heat retention effect near the cylindrical tip piece 212 where unmelted resin pellets are present during operation.

[0059] As shown in Figure 13, the second insulation material 82 has an annular shape facing the outer circumference of the upper flange portion 215 of the inlet component 21 and a part of the outer circumference of the first central component 22. The third insulation material 83 has an annular shape facing a part of the outer circumference of the first central component 22 and a part of the outer circumference of the second central component 23. The fourth insulation material 84 has an annular shape facing a part of the outer circumference of the second central component 23. The fifth insulation material 85 has an annular shape facing a part of the outer circumference of the second central component 23 and the outer circumference of the lower flange portion 252 of the nozzle holder component 25.

[0060] As shown in Figure 13, the sixth heat insulating material 86 has an annular shape that faces the outer circumference of the cone portion 253 of the nozzle holder component 25, and its inner circumferential surface is provided in a conical shape corresponding to the shape of the cone portion 253.

[0061] Thus, the insulation material 8, formed by combining the first to sixth insulation materials 81 to 86 in the axial direction, has an outer shape that is approximately cylindrical and is configured to cover almost the entire outer surface of the melting vessel body 20, except for the portion where the nozzle 5 protrudes. It is also possible to provide holes in the insulation material 8, for example, for passing thermocouple lead wires, as appropriate.

[0062] [Cover component] As shown in Figure 13, the melting vessel body 20 is surrounded by the aforementioned heat insulating material 8, and the outside of the heat insulating material 8 is further surrounded by a cover member 9. The cover member 9 has a cylindrical side cover 92 that covers the sides of the melting vessel body 20, a top cover 91 that covers the top surface of the melting vessel body 20, and a bottom cover 93 that covers the bottom surface of the melting vessel body 20. All of these are made of aluminum alloy material.

[0063] The side cover 92 has eight notches 926 in the circumferential direction on its axial upper end surface for guiding the lead wires 62 of the heater 6, and a total of eight screw holes (not shown) on the upper end surface between these notches 926 for connecting to the top cover 91. Similarly, the lower end surface of the side cover 92 has eight screw holes (not shown) for connecting to the bottom cover 93.

[0064] The top cover 91 is made of an annular plate, and its inner diameter is set to correspond to the outer diameter of the cylinder 10 connected to the melting body 20, while its outer diameter is set to match that of the side cover 92. The top cover 91 has a total of eight screw holes (not shown) located opposite the screw holes provided on the upper end surface of the side cover 92. The top cover 91 is fastened to the side cover 92 by screws 98, as shown in Figure 13.

[0065] The bottom cover 93 is made of an annular plate, and its inner diameter is set to correspond to the outer diameter of the nozzle holder component 25 at the opposite position, while its outer diameter is set to match that of the side cover 92. The bottom cover 93 has a total of eight screw holes (not shown) at positions opposite to the screw holes provided on the lower end surface of the side cover 92. The bottom cover 93 is fastened to the side cover 92 by screws 98, as shown in Figure 13.

[0066] As shown in Figure 13, the melting furnace 2 is connected to the cylinder 10 by fixing the outer circumferential surface 213 of the cylindrical tip piece 212 of the inlet part 21 to the inner circumferential surface of the lower end of the cylinder 10. Specifically, a male thread (not shown) is provided on the outer circumferential surface 213 of the cylindrical tip piece 212, and a female thread (not shown) is provided on the inner circumferential surface of the lower end of the cylinder 10, and the two are fixed together by screwing them securely.

[0067] Furthermore, as shown in Figures 1 and 2, cooling fins 55 are provided on the upstream side of the melting vessel 2, surrounding the outer surface of the cylinder 10. These cooling fins 55 suppress heat transfer from the melting vessel 2 to the upper part of the cylinder 10 and are made of aluminum fin material. Note that these cooling fins 55 can be changed to other configurations as needed.

[0068] [Operation] Next, the operation of the plunger-type injection molding machine 1 in this example will be explained. First, the motor 45 of the drive unit 4 is driven to retract (raise) the plunger 3, creating sufficient space inside the cylinder 10. In this state, resin pellets are supplied from the pellet hopper 14. A sufficient amount of resin pellets is supplied to fill the cylinder 10 and fill at least partway up the supply pipe 13.

[0069] At this point, the heater 6 built into the melting pot 2 is energized by the heater control device, and the melting pot body 20 heats up to the melting temperature of the resin pellets. Subsequently, the temperature of the melting pot body 20 is controlled by the heater control device based on measured temperature data taken from the thermocouple.

[0070] After the melting body 20 reaches the appropriate temperature, the motor 45 is driven to advance the plunger 3. This causes the resin pellets pushed by the pressing surface 32 of the plunger 3 to move forward and are sequentially fed into the melting hole 29 (inner tube 7) of the melting body 2. As the resin pellets move through the melting hole 29, they receive heat from the melting body 20 and become completely molten by the time they reach the outlet, and then proceed to enter the cone portion 253 of the nozzle holder component 25. The molten resin filled in the cone portion 253 is injected into the mold (not shown) from the discharge port 53 of the nozzle 5 under the pressure generated by the advancement of the plunger 3.

[0071] The plunger-type injection molding machine 1 in this example, which operates in this manner, has a melting vessel 2 with the configuration described above. The melting vessel 2 is equipped with an inner tube 7 on the inner surface of the melting hole 29 of the melting vessel body 20. The inner tube 7 has superior wear resistance to the tellurium copper that constitutes part of the melting vessel body 20. Therefore, even when melting a resin containing a hard filler, for example, wear of the melting hole 29 can be suppressed, and the lifespan of the resin melting vessel 2 can be significantly improved.

[0072] Furthermore, the melting pot body 20 in this example is constructed by connecting multiple parts 21 to 25 in the axial direction. This eliminates the need to machine the entire length of the melting hole 29 at once, allowing the machining length to be shortened to the length of each individual part. This significantly improves machinability.

[0073] Furthermore, it becomes possible to change the material of each of the multiple parts 21 to 25, making it possible to select the optimal material according to the part. This is based on the important premise that by ensuring the wear resistance of the inner surface of the molten hole 29 with the inner tube 7 described above, it becomes unnecessary to guarantee the wear resistance characteristics of the melting body itself. In this example, the inlet parts 21 located at the upstream and downstream ends have surfaces that come into contact with resin pellets or molten resin and Exit part 24 and The nozzle holder component 25 is made of the same SUS304 as the inner tube 7, and its wear resistance and strength are enhanced. The other components, namely the first central component 22 and the second central component 23 teeth It is constructed of tellurium copper, maximizing its thermal conductivity. By adopting this configuration, a melting pot body 20 can be obtained that has excellent wear resistance while ensuring thermal conductivity.

[0074] Furthermore, the inlet component 21 is integrally provided with a cylindrical tip piece 212 that is erected axially from the outer circumference of the inlet surface 211. As a result, the inlet surface 211 and the inner surface of the cylindrical tip piece 212 are connected without any gaps, ensuring that the resin pellets pressed by the plunger 3 at the inlet side of the melting furnace 2 are reliably received, and problems such as resin leakage can be reliably prevented.

[0075] Furthermore, the melting vessel body 20 in this example has a central projection 214 that protrudes upstream without having a melting hole 29 on the axial center. This is expected to have the effect of smoothly straightening the flow of the pressed resin pellets from the center to the outer circumference.

[0076] Furthermore, in this example, the melting vessel 2 is provided with multiple heater insertion holes 27 in the melting vessel body 20, and the heating elements 61 of the rod-shaped heater 6 are inserted into these heater insertion holes 27. With this configuration, heat can be directly transferred from inside the melting vessel body 20, and the melting vessel body 20 can be heated efficiently. In addition, the heating elements 61 are positioned in opposing axial positions in a region of more than 90% of the total length of the melting hole when viewed from a direction perpendicular to the axial direction. As a result, most of the heat emitted from the heating elements 61 of the heater 6 can be transferred to the inner surface of the melting hole 29 simply by moving axially. This also allows the melting vessel body 20 to be heated efficiently and stably.

[0077] Furthermore, the outer periphery of the melting vessel body 20 is surrounded by the insulating material 8. This suppresses the heat emitted from the heater 6 from escaping to the outside through the outer periphery of the melting vessel body 20, thereby enabling more efficient heating. In this example, the outer periphery of the cone section 253 is also covered with the insulating material 8, which also suppresses the heat from escaping to the outside from the cone section 253.

[0078] (Example 2) As shown in Figure 15, this example adopts a configuration in which the melting body 202 has melting holes 29 on the axis and does not have the central projection 214 as in Example 1. The other configurations are the same as in Example 1. In this case, although the rectification effect of the central projection 214 cannot be obtained, the total opening area of ​​the melting holes 29 through which the resin pellets pass can be made larger than in Example 1, and the flow rate of the molten resin can be increased. The suitability of the rectification effect and the increase in flow rate differs depending on the type of resin being processed, so the configuration of Example 2 may be effective instead of Example 1 in some cases.

[0079] (Example 3) This example, as shown in Figure 16, is an example in which a different locking portion 299 is provided in the melting hole 29 of the melting machine body 203 compared to Example 1. The inner tube 7 has a large-diameter portion 78 formed near the inlet side, and an inner tube-side locking portion 789 is provided, which is formed from the axial outlet end face of the large-diameter portion 78. The inner tube 7 is then pressed into the melting hole 29, and the locking portion 299 of the melting hole 29 and the inner tube-side locking portion 789 are brought into contact. The other configurations are the same as in Example 1. In this case, a configuration can be obtained in which the inner tube 7 exists along the entire length of the inner surface of the melting hole 29, enabling a smoother resin flow. Other effects similar to those in Example 1 can be obtained.

[0080] (Example 4) This example, as shown in Figure 17, features a different shape for the melting hole 29 of the melting machine body 204 and the inner tube 7 compared to Example 1. The melting hole 29 has an inlet straight section 291, a smaller diameter outlet straight section 293, and a relatively abruptly tapered intermediate section 292 connecting them. The inner tube 7 follows the shape of the melting hole 29, having an inlet straight section 741, an outlet straight section 743, and an intermediate tapered section 742. The inner tube 7 is press-fitted into the melting hole 29, ensuring a tight seal between the two. The other configurations are the same as in Example 1. In this case, the contact portion between the intermediate tapered section 292 of the melting hole 29 and the intermediate tapered section 742 of the inner tube 7 exhibits the same effect as the locking portion described above, and the extensive use of straight sections improves dimensional accuracy during manufacturing. Other effects similar to those in Example 1 can be obtained.

[0081] (Example 5) This example, as shown in Figure 18, features a different shape for the melting hole 29 of the melting machine body 205 and the inner tube 7 compared to Example 1. The melting hole 29 has a shape consisting of an inlet straight section 295 and a smoothly tapering section 296. The inner tube 7 follows the shape of the melting hole 29, having an inlet straight section 751 and a tapered section 752. The inner tube 7 is then press-fitted into the melting hole 29, ensuring a tight seal between the two. The other configurations are the same as in Example 1. In this case, the processing accuracy of the inlet straight section 751 during manufacturing can be improved, further enhancing the seal with the melting hole 29. Other effects similar to those in Example 1 can be obtained.

[0082] (Other aspects) In Examples 1 to 5, the melting machine body 2, 202 to 205 was shown to be constructed by connecting multiple parts, but it is also possible to change this to be constructed with a single part. In addition, a rod-shaped heater was used as the heater for heating the melting machine body 2, 202 to 205, but it is also possible to change this to a heater that surrounds the melting machine body 2, 202 to 205 from the outer surface. [Explanation of Symbols]

[0083] 1. Plunger-type injection molding machine 10 cylinders 2. Resin melting vessel 20 Melting machine body 3 Plungers 4 Drive Unit 5 nozzles 6 Heaters 7 Inner tube 8. Insulation 9 Cover component

Claims

1. A resin melter incorporated into a plunger-type injection molding machine, The resin melter has a melter body having multiple melting holes that penetrate in the axial direction, arranged at intervals on multiple concentric circles centered on the axis of the resin melter. The melting vessel body is constructed by connecting two or more separate parts with different wear resistances in the axial direction. A resin melting vessel, wherein an inner tube made of a metal material having better wear resistance than the least wear-resistant component constituting the melting vessel body is disposed in a plurality of melting holes formed through all of the aforementioned components.

2. The resin melting vessel according to Claim 1, wherein the inner tube is made of austenitic stainless steel, the inlet component located furthest upstream among the components in the melting vessel body is made of austenitic stainless steel, and the other components include components made of copper or a copper alloy.

3. The resin melter according to claim 1, wherein the melting hole has a tapered shape in which the inner diameter decreases from the inlet to the outlet, and the inner tube has a tapered shape that conforms to the inner surface of the melting hole.

4. The resin melter according to claim 1, wherein the melting hole of the melting body is provided with a locking portion that abuts the inner tube in the axial direction to prevent the inner tube from shifting position toward the outlet side within the melting hole.

5. The resin melting apparatus according to claim 1, wherein the melting apparatus body integrally includes a cylindrical tip piece erected axially from the outer circumference of the inlet surface, which is the axial end surface from which the inlet of the melting hole is opened.

6. The resin melter according to claim 1, wherein a central projection is provided on the axis of the melting body that protrudes upstream without having the melting hole.

7. It comprises at least a cylinder with a pellet supply port, a plunger arranged to move axially back and forth within the cylinder, a drive unit for moving the plunger, a resin melter for melting resin pellets supplied from the pellet supply port, and a nozzle for discharging the molten resin. The plunger-type injection molding machine comprises a resin melter according to any one of claims 1 to 6.

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