Injection molding apparatus

Abstract

The present invention provides an injection molding apparatus that can quickly heat the end of a manifold to which a hot runner bush is connected to an injection molding temperature, and can also reduce the amount of heat required. [Solution] The injection molding apparatus of the present invention comprises a fixed mold provided with a hot runner bush, a sprue for connecting the nozzle of an injection molding machine, a manifold disposed on the fixed mold and having a hot runner, a drive unit having a drive unit body and a leg integrally provided at the lower end of the drive unit body, the leg being fixed on the manifold and to which the upper end of a valve pin that opens and closes the lower end gate of the resin passage in the hot runner bush is connected, and a sheath heater disposed between the leg of the drive unit and the outer peripheral edge of the manifold on the surface on which the drive unit is disposed of the manifold.

Description

Technical Field

[0001] The present invention relates to an injection molding apparatus.

Background Art

[0002] An injection molding apparatus includes a manifold disposed with an appropriate gap on a fixed mold and having a hot runner formed therein, and a hot runner bushing connected to an end of the manifold and communicating a lower end thereof with a cavity formed between the fixed mold and a movable mold. A heater for heating and maintaining the molten resin flowing through the hot runner is disposed along the hot runner.

[0003] As an injection molding apparatus, in Patent Document 1, in a hot runner mold in which a runner communicating a sprue to which a nozzle of an injection molding machine body is connected and a plurality of cavities is formed in a manifold having a heater, the manifold is composed of a pair of manifold members and a traverse manifold member straddling these two manifold members. The traverse manifold member has a primary runner branched from the sprue toward the two manifold members and a heater positioned along the primary runner. Each of the manifold members has a secondary runner branched from the primary runner along the arrangement direction of the two manifold members, a tertiary runner branched from the secondary runners in a direction intersecting the arrangement direction of the two manifold members and communicating with the cavities respectively, and a heater positioned along the secondary runners and the tertiary runners. A hot runner mold apparatus is disclosed in which the heater of the manifold member is provided commonly for a group of tertiary runners branched from the same position of the secondary runner and separately for a group of tertiary runners having different branching positions.

[0004] And, the above hot runner mold apparatus uses a sheathed heater as a heater, and the sheathed heater is used by being fitted into a groove formed on the surface of the hot runner.

[0005] Furthermore, in the hot runner mold apparatus described above, a valve consisting of a needle pin for opening and closing the gate is incorporated into the bush so as to be movable in the vertical direction. This valve is incorporated into the fixed mounting plate and connected to a fluid pressure cylinder device, and is configured to be driven by the fluid pressure cylinder device. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-24087 [Overview of the project] [Problems that the invention aims to solve]

[0007] On the other hand, when injection molding is performed using the hot runner mold device described above, the nozzle of the injection molding machine is connected to a sprue attached to the fixed mounting plate, and molten resin is injected into the runner of the manifold under pressure. However, when this molten resin is injected, a large amount of pressure is applied to the fixed mounting plate from the injection molding machine towards the manifold.

[0008] Furthermore, while molten resin is being injected into the manifold runner through the sprue from the nozzle of the injection molding machine, the valve inside the hot runner bush has its tip inserted into the gate, maintaining a closed gate position, and the valve is restricted from moving any further downward.

[0009] Therefore, the pressure applied from the injection molding machine to the fixed mounting plate is transmitted to the valve via a fluid pressure cylinder fixed to the fixed mounting plate. However, as mentioned above, the valve is restricted from moving any further downwards, which could damage the valve.

[0010] Therefore, a spacer is placed between the manifold section (the tip of the manifold) where the hot runner bushing is located and the fixed mounting plate to prevent the pressure applied to the fixed mounting plate from being transmitted to the valve.

[0011] The spacers interposed between the fixed mounting plate and the tip of the manifold are arranged on the tip of the manifold so that the spacing between the spacers is as wide as possible, in order to distribute and receive as much stress as possible that is applied from the fixed mounting plate to the tip of the manifold. They are usually arranged on the outer edge of the surface of the tip of the manifold facing the fixed mounting plate.

[0012] Therefore, the spacer is positioned either overlapping the sheath heater located on the surface of the tip of the manifold, or closer to the outer edge of the tip of the manifold than the sheath heater.

[0013] If the above-mentioned spacer is positioned above the sheathed heater, the heat from the sheathed heater located on the surface of the manifold will be more easily dissipated through the spacer towards the fixed mounting plate.

[0014] Furthermore, since heat is dissipated from the outer surface of the manifold, the manifold becomes more difficult to heat as you approach its outer edge. If the sheathed heater is positioned further away from the outer edge of the manifold than the spacer, the outer edge of the manifold will be further separated from the sheathed heater, making it even more difficult to heat with the heater, and heat will also be dissipated by the spacer.

[0015] Therefore, if the spacer is positioned above the sheath heater, or closer to the outer edge of the manifold than the sheath heater, the heating of the manifold portion where the bush is installed becomes uneven, resulting in the problem of unstable temperature of the molten resin flowing through the manifold runner.

[0016] The present invention provides an injection molding apparatus that can heat the manifold portion to which the hot runner bush is connected almost uniformly and stably maintain the temperature of the molten resin flowing through the runner of the manifold at a desired temperature. [Means for solving the problem]

[0017] The injection molding apparatus of the present invention is A fixed mold equipped with a hot runner bush for supplying molten resin to the cavity, A sprue for connecting the nozzle of an injection molding machine, A manifold disposed on the above-mentioned fixed mold and having a hot runner formed from the sprue toward the hot runner bush, A drive unit having a drive unit body and a leg portion integrally provided at the lower end of the drive unit body, the leg portion being fixed on the manifold, and the upper end of a valve pin that opens and closes the lower end gate of the resin passage in the hot runner bush being connected to the drive unit, The manifold is characterized in that, on the mounting surface of the drive unit, it has a sheathed heater disposed between the legs of the drive unit and the outer peripheral edge of the manifold. [Effects of the Invention]

[0018] In the injection molding apparatus of the present invention, a sheathed heater is provided between the legs of the drive unit and the outer edge of the manifold on the mounting surface of the drive unit in the manifold, and the portion of the manifold closer to the outer edge of the manifold than the legs of the drive unit is heated by the sheathed heater.

[0019] In other words, the injection molding apparatus of the present invention heats the manifold with a sheath heater at a position close to the outer edge of the manifold, which is less likely to be heated, so that the connection part with the hot runner bush and the manifold portion in the vicinity thereof can be heated sufficiently and uniformly throughout, and the temperature of the molten resin flowing through the runner of the manifold can be stably maintained at the desired temperature.

[0020] Furthermore, the injection molding apparatus of the present invention heats the entire manifold by a sheath heater from a position close to the outer edge of the manifold, and even if heat is dissipated through the legs of the drive unit located inside the sheath heater (in the direction away from the outer edge of the manifold), the effect of heat dissipation from the legs can be minimized because the entire manifold is sufficiently heated, and the connection portion with the hot runner bush and the manifold portion in the vicinity thereof can be heated sufficiently and uniformly throughout.

[0021] When a sprue is provided on the manifold and the manifold is positioned at a distance from the fixed mounting plate, there is generally no stress that brings the drive unit and the manifold portion facing it into close proximity. Therefore, there is no need to interpose a spacer between them, and space for the sheath heater can be secured on the manifold's mounting surface for the drive unit, closer to the outer edge than the legs of the drive unit. This space can be used to position the sheath heater on the manifold portion closer to the outer edge than the legs of the drive unit. Consequently, the connection portion with the hot runner bush and the surrounding manifold portion can be heated sufficiently and uniformly throughout.

[0022] In the above injection molding apparatus, a connecting convex portion for connecting a hot runner bushing is provided protruding from the lower surface of the manifold. When the upper end portion of the hot runner bushing is screwed and integrated with the connecting convex portion, in the manifold, while protruding the connecting convex portion for connecting the hot runner bushing, the other portions of the manifold do not need to have an increased thickness, and the thickness of the manifold can be made thinner. As a result, the reduction of the amount of heat for heating the entire manifold can be achieved more effectively, and the heating time required for the manifold to reach a state where injection molding is possible can be shortened.

Brief Description of the Drawings

[0023] [Figure 1] Vertical sectional front view of a part of the injection molding apparatus. [Figure 2] Simplified plan view of the injection molding apparatus. [Figure 3] Simplified bottom view of the injection molding apparatus. [Figure 4] Cross-sectional view of the sheathed heater. [Figure 5] Vertical sectional view of the arrangement portion of the sheathed heater. [Figure 6] Vertical sectional view showing a state where a heat insulating sheet is disposed on the outer peripheral surface of the manifold.

Embodiments for Carrying Out the Invention

[0024] An example of the injection molding apparatus of the present invention will be described based on the drawings. In FIG. 1, the injection molding apparatus is configured such that a fixed mold 1 and a movable mold 2 are arranged facing each other vertically, and a cavity 3 for obtaining a molded product is formed between the opposing surfaces of the fixed mold 1 and the movable mold 2. A manifold 4 formed in a block shape having a certain width, a certain height, and a long length is disposed on the fixed mold 1, and is fixed to the fixed mold 1 by bolts or the like.

[0025] The manifold 4 has a sprue bush 50 projecting upwards to which a nozzle 27 for supplying molten resin from an injection molding machine is connected, with the sprue 5 located inside the sprue bush 50. The manifold 4 is formed by multiple block-shaped sections extending radially in a planar direction from the location where the sprue 5 is installed. In the manifold 4, the block-shaped sections extending radially from the sprue 5 may be branched as needed. The manifold 4 does not have to be formed radially from the sprue 5. The sprue bush 50 may be integrally provided on the fixed-side mounting plate K of the injection molding machine.

[0026] Inside the manifold 4, there is a hot runner 6 that branches off from the lower end of the sprue 5 and whose tip reaches the tip 4a of each branched manifold section, serving as a passage for molten resin. A hot runner bush 7 is connected to the tip 4a of each manifold section.

[0027] A connecting projection 41 is provided on the lower surface of the manifold 4, and a hot runner bush 7 is connected and integrated with this connecting projection 41. Specifically, the hot runner bush 7 provided at each tip 4a of the manifold 4 is positioned with its upper part protruding towards the gap 20 between the fixed mold 1 and the manifold 4, and is disposed in a mounting hole 23 provided in the fixed mold 1. A reduced-diameter portion 7a, which has a reduced outer diameter, is provided on the upper end of the hot runner bush 7, protruding upward, and a threaded portion 7b is engraved on the outer surface of the reduced-diameter portion 7a. The hot runner bush 7 is attached to the manifold 4 by screwing the reduced-diameter portion 7a of the hot runner bush 7 into the threaded hole 41a of the connecting projection 41 that protrudes from the lower surface of the manifold 4.

[0028] In this manner, a connecting projection 41 is formed on the lower surface of the manifold 4, and the reduced diameter portion 7a of the hot runner bush 7 is connected to this connecting projection 41. In conventional manifolds, the overall thickness of the manifold was increased to form screw holes for connecting the hot runner bush. However, in the above injection molding apparatus, the connecting projection 41 is formed only in the manifold portion to which the hot runner bush 7 is connected, while the other manifold portions only need to have the thickness necessary to accommodate the hot runner 6 and the sheath heater described later, thus reducing the overall volume of the hot runner. Consequently, the amount of heat required to heat the entire hot runner to a temperature suitable for injection molding can be reduced, leading to energy savings, and the time required to heat the entire hot runner to a temperature suitable for injection molding can also be shortened.

[0029] Furthermore, the hot runner bush 7 is equipped with a band heater 25 on its outer surface, and is configured to maintain a good melt state by heating the molten resin that is filled into the cavity 3 from the hot runner 6 through the resin passage 8 inside the hot runner bush 7 with the band heater 25.

[0030] A hot runner bushing 7 is attached to the connecting projection 41 of the manifold 4, and a drive device 15 such as a fluid pressure cylinder (e.g., a hydraulic cylinder, an air cylinder) is installed on each of the tip portions 4a of the manifold 4.

[0031] The drive unit 15 comprises a drive unit body 151 that houses a cylinder tube and a drive unit such as a piston disposed within the cylinder tube, and a plurality of legs 152 provided on the lower surface of the drive unit body 151. The drive unit 15 is installed by fixing the legs 152 to the upper surface of the tip portion 4a of the manifold. In this specification, the case in which the legs 152 are integrally provided at the four corners of the rectangular bottom surface of the drive unit body 151 is shown, but the specification is not limited to this.

[0032] The upper end of the valve pin 14, which is inserted into the resin passage 8 of the hot runner bush 7, is connected to the drive unit body 151. The drive unit 15 moves the valve pin 14 inserted into the resin passage 8 of the hot runner bush 7 up and down, and the valve pin 14 opens and closes the lower end gate of the resin passage 8, which is open toward the cavity 3.

[0033] The drive unit 15 is spaced apart from the fixed mounting plate K of the injection molding machine, and is not connected to the fixed mounting plate K; it is disconnected. Since the drive unit 15 does not receive the pressing force from the fixed mounting plate K directed toward the manifold 4 when connecting the nozzle of the injection molding machine to the sprue bush 50, there is no need to provide a spacer on the upper surface of the tip portion 4a of the manifold 4 to receive the above pressing force from the injection molding machine. On the upper surface of the tip portion 4a of the manifold 4, a space can be formed for providing a sheath heater, which will be described later, outside the fixed portion that fixes the legs 152 of the drive unit 15 (in the direction closer to the outer peripheral edge of the tip portion 4a of the manifold 4).

[0034] The tips of each hot runner 6, which radiate from the sprue 5, are connected to the upper end openings of the resin passages 8 within the hot runner bushes 7 located at the tip 4a of each manifold 4.

[0035] Therefore, the molten resin injected into the sprue 5 from the nozzle 27 of the injection molding machine is divided and flows into each hot runner 6 in each manifold 4 that extends radially from the lower end of the sprue 5, and is then fed through these hot runners 6 into the resin passages 8 of the corresponding hot runner bushes 7.

[0036] As shown in Figures 2 and 3, each tip 4a of the manifold 4, which extends radially from the sprue 5 with the sprue 5 at its center, is provided with a flange portion 18 having bolt insertion holes 19 at the lower ends of both sides. These flange portions 18 are installed on the upper surface of the fixed mold 1, and bolts 17 are screwed through the bolt insertion holes 19 into screw holes (not shown) provided in the fixed mold 1, thereby fixing the manifold 4 on the fixed mold 1 in a mounting state with a certain gap 20 between the lower surface of the manifold 4 and the upper surface of the fixed mold 1.

[0037] Furthermore, as shown in Figures 2, 3, and 5, sheathed heaters 9 are provided on the surface (upper and lower surfaces) of the manifold 4. Specifically, grooves 4b for providing the sheathed heaters 9 are recessed in each of the upper and lower surfaces of the manifold 4, and the sheathed heaters 9 are fitted into these grooves 4b, provided and fixed in place. As shown in Figure 4, the sheathed heater 9 comprises a metal pipe 91 of a certain length, a spiral nichrome wire 92 provided inside the metal pipe 91, terminal pins 93, 93 electrically connected to both ends of the nichrome wire 92, and an insulating member 94 (for example, a powder such as magnesia) interposed between the nichrome wire 92 and the metal pipe 91 to electrically insulate the nichrome wire 92 from the metal pipe 91. The sheathed heater 9 is configured such that a DC power supply is connected to the terminal pins 93, 93 at both ends, and electricity is passed through the nichrome wire 92, causing the nichrome wire 92 to heat up and transfer heat to the metal pipe 91 through the insulating member 94, causing the metal pipe 91 to become hot. The sheathed heater 9 has a heating section 9a where the nichrome wire 92 is arranged and generates heat when electricity is passed through it, and non-heating sections 9b, 9b at both ends where the nichrome wire 92 is not arranged.

[0038] The groove 4b for arranging the sheathed heater 9 has a width dimension that is the same as or slightly narrower than the diameter of the sheathed heater 9. When the sheathed heater 9 is arranged in the groove 4b, at least a portion of the outer surface of the sheathed heater 9 is in close contact with the inner surface of the groove 4b, so that the heat from the sheathed heater 9 is smoothly transferred to the manifold 4.

[0039] Multiple grooves 4b are formed on the upper and lower surfaces of the manifold 4. A groove 4b is formed for each sheathed heater 9, and one sheathed heater 9 is installed in each groove 4b. The grooves 4b are formed on the upper and lower surfaces of the manifold 4 so that they have the same shape when viewed from above. When the grooves 4b formed on the surface of the manifold 4 are projected onto the back surface, grooves 4b of the same shape are also formed on the back surface of the manifold 4. The multiple grooves 4b are arranged so that the molten synthetic resin flowing through the hot runner 6 of the manifold 4 is heated and maintained at a generally uniform temperature. Note that the grooves 4b do not necessarily need to be formed on the upper and lower surfaces of the manifold 4 so that they have the same shape when viewed from above.

[0040] The groove 4b is configured as a single groove with a curved section, and both ends 4b1, 4b1 of the groove 4b open on the same side surface of the manifold 4 with a small gap between them. One sheathed heater 9 is disposed in each groove 4b, and the sheathed heater 9 is fitted and fixed along the groove 4b in a curved state as needed. The non-heating portions 9b at both ends of the sheathed heater 9 are drawn out from the same outer surface 4c of the manifold 4 through both ends 4b1, 4b1 of the groove 4b along their entire length, and only the heating portion 9a of the sheathed heater 9 is disposed in the groove 4b. That is, the heating portion 9a of the sheathed heater 9 reaches the outer surface 4c of the manifold 4 from which the non-heating portions 9b at both ends of the sheathed heater 9 are drawn out, and only the heating portion 9a of the sheathed heater 9 is disposed on the manifold 4. Therefore, the sheathed heaters 9 arranged on the upper and lower surfaces of the manifold 4 can effectively heat the manifold 4.

[0041] Furthermore, the tip portion 4a of the manifold 4 to which the hot runner bush 7 is connected is connected to the flange portion 18 and bolt 17 for fixing the manifold 4 onto the fixed mold 1, the hot runner bush 7, and the leg portion 152 for fixing the drive unit 15 to the manifold 4. Through these, heat from the manifold 4 can easily escape to the outside, making it a part that is easily cooled.

[0042] Therefore, a portion of the sheathed heater 9 is curved to form a curved section 9c, and the curved section 9c and the extended sections 9d extending from both ends of the curved section 9c are bent to form a roughly U-shape in plan view, and this planar U-shaped sheathed heater 9 is arranged in the part of the manifold 4 that includes the tip section 4a.

[0043] More specifically, the curved portion 9c of the sheathed heater 9 is positioned on the upper and lower surfaces of the manifold 4 on the sprue 5 side of the connection point between the manifold 4 and the hot runner bush 7 (connection projection 41 protruding from the lower surface of the manifold 4).

[0044] Furthermore, extensions 9d, 9d of the sheath heater 9 are arranged on the upper and lower surfaces of the tip portion 4a of the manifold 4, between the outer peripheral edges 4a1 on both sides of the tip portion 4a of the manifold 4 and the legs 152 of the drive unit 15 that are opposite to them. Note that the position of the "legs 152 of the drive unit 15" on the lower surface of the tip portion 4a of the manifold is the position obtained by projecting the legs 152 of the drive unit 15 onto the lower surface of the tip portion 4a of the manifold.

[0045] The extensions 9d, 9d of the sheath heater 9 pass to the side of the legs 152 of the drive unit 15 and are positioned outside the legs 152 of the drive unit 15 (in a direction closer to the outer peripheral edge 4a1 of the tip 4a of the manifold 4). The tip 4a of the manifold 4 becomes more difficult to heat as you approach the outer peripheral edge due to heat dissipation from its outer peripheral end face, but since the sheath heater 9 is positioned close to the outer peripheral edge of the tip 4a of the manifold 4, the entire tip 4a of the manifold can be sufficiently heated and maintained at a uniform temperature. The tip 4a of the manifold is sufficiently heated throughout, and the legs 152 and connecting protrusions 41 of the drive unit 15 are connected inward from the sheath heater 9 (in a direction away from the outer peripheral edge 4a1 of the tip 4a of the manifold 4). Since the portion of the manifold to which the legs 152 of the drive unit 15 and the hot runner bush 7 are connected is sufficiently heated, the effect of heat dissipation from the legs 152 of the drive unit 15 and the hot runner bush 7 is largely negligible, and the tip 4a of the manifold 4 is sufficiently and generally uniformly heated.

[0046] The extensions 9d, 9d of the sheathed heater 9 are arranged so that their tips (non-heating parts 9b) extend out from the tip surface 4d of the manifold 4, passing outside the legs 152 and connecting protrusions 41 of the drive unit 15. The heating part 9a of the sheathed heater 9 reaches the tip surface 4d of the manifold 4. Since the heating part 9a of the sheathed heater 9 is arranged up to the tip surface 4d of the manifold 4, the tip surface 4a of the manifold 4 can be sufficiently heated without surrounding the tip side of the manifold 4 with sheathed heaters. Note that on the upper surface of the manifold 4, "connecting protrusions 41" refers to the portion of the connecting protrusions 41 projected onto the upper surface of the manifold 4.

[0047] The above describes a case where the curved portion 9c of the sheathed heater 9 is positioned on the upper and lower surfaces of the manifold 4 on the sprue 5 side of the connection portion between the manifold 4 and the hot runner bush 7 (connecting projection 41 protruding from the lower surface of the manifold 4). However, the curved portion 9c of the sheathed heater 9 may also be positioned on the upper and lower surfaces of the tip portion 4a of the manifold 4, between the tip edge 4a2 of the manifold 4 and the leg portion 152 of the drive unit 15 facing this tip edge 4a2. The extension portions 9d, 9d of the sheathed heater 9 are positioned in the same manner as described above. The extension portions 9d, 9d of the sheathed heater 9 are positioned so that their tip portions (non-heating portions 9b) extend out from any end face (preferably the same end face) of the manifold 4, passing outside the leg portion 152 of the drive unit 15 and the connecting projection 41.

[0048] Furthermore, it is preferable that the manifold 4 of the injection molding apparatus is covered with a heat-shielding coating. The proportion of the surface area of ​​the manifold 4 covered with the heat-shielding coating is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. By covering the surface of the manifold 4 with a heat-shielding coating, the dissipation of heat from the manifold 4 heated by the sheath heater 9 can be suppressed, and the manifold 4 can be stably maintained at the desired temperature.

[0049] A heat-reflective coating can be formed on the surface of the manifold 4 by applying a heat-reflective paint containing a binder component, a white pigment such as titanium dioxide, and a heat-reflective component such as hollow glass balloons to the surface of the manifold 4 and allowing it to dry or harden. The binder component should be selected to not be altered by the heat of the manifold 4.

[0050] Furthermore, as shown in Figure 6, it is preferable that the surface of the manifold 4 of the injection molding apparatus is covered with a heat-shielding sheet B. The proportion of the surface area of ​​the manifold 4 covered with the heat-shielding sheet B is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. By covering the surface of the manifold 4 with the heat-shielding sheet B, the dissipation of heat from the manifold 4 heated by the sheath heater 9 can be suppressed, and the manifold 4 can be stably maintained at the desired temperature.

[0051] The heat-shielding sheet is not particularly limited as long as it can block heat without being altered by the heat of the manifold 4, and examples include metal sheets. It is preferable that the heat-shielding sheet B has an uneven surface. For example, it is preferable that the heat-shielding sheet has multiple linear recesses B1 formed in parallel on one surface of the sheet body, and multiple linear recesses extending in parallel in a direction perpendicular to these recesses B1. By using a heat-shielding sheet B with an uneven surface, and covering the surface of the manifold 4 with the heat-shielding sheet B while forming an air layer C between the heat-shielding sheet B and the surface of the manifold 4, the heat insulation effect of the air layer C and the heat-shielding sheet B can be achieved, and the heat dissipation from the manifold 4 can be suppressed more effectively.

[0052] Next, the procedure for using the injection molding apparatus will be explained. When starting injection molding using the injection molding apparatus, the manifold 4 is heated by the sheath heater 9 until it reaches a temperature suitable for injection molding.

[0053] Sheathed heaters 9 are provided on the upper and lower surfaces of the manifold 4, and the manifold 4 is heated by the sheathed heaters 9 from above and below, so the manifold 4 is effectively heated by the sheathed heaters 9.

[0054] Furthermore, as mentioned above, the tip 4a of the manifold 4 is a part that is easily cooled. However, by arranging the sheath heater 9 between the outer peripheral edges 4a1, 4a1 on both sides of the tip 4a of the manifold 4 and the legs 152, 152 of the drive unit 15 that face these outer peripheral edges 4a1, 4a1, the tip 4a of the manifold 4 is heated from its outer peripheral edge, so that the entire tip 4a of the manifold 4 can be sufficiently heated and maintained at a uniform desired temperature.

[0055] In the sheathed heater 9 located at the tip 4a of the manifold 4, the distance between the extensions 9d on both sides can be narrowed, thereby reducing the width of the tip 4a of the manifold 4. This reduces the volume of the manifold 4, leading to energy savings and a reduction in heating time by decreasing the amount of heat required to heat the tip 4a of the manifold 4.

[0056] In this way, the injection molding apparatus can effectively heat the tip 4a of the manifold 4, thereby shortening the heating time required to reach a temperature suitable for injection molding, and improving the production efficiency of molded products.

[0057] Before initiating injection molding, the entire manifold 4 is heated by a sheath heater 9 to a temperature approximately equal to the melting temperature of the molten resin injected from the nozzle 27 of the injection molding machine, and this temperature is maintained. Then, the molten resin is injected from the nozzle 27 of the injection molding machine into the sprue 5 and divided into the hot runners 6 in each manifold 4 that radiate from the lower end of the sprue 5.

[0058] The manifold 4 is equipped with temperature sensors (not shown) in each area where sheath heaters 9 are installed, and the temperature of the manifold is monitored by these temperature sensors. When the temperature of the manifold rises above a predetermined temperature, the voltage applied to the sheath heaters 9 is reduced, while when the temperature of the manifold falls below a predetermined temperature, the voltage applied to the sheath heaters 9 is increased to control the heating temperature of the manifold by the sheath heaters 9, adjusting it to a temperature at which the molten resin flowing through the hot runner 6 of the manifold 4 is in a good melt state.

[0059] Then, the molten resin flowing through the hot runner 6 of the manifold 4 is supplied into the resin passage 8 of the hot runner bush 7, and the valve pin 14 is moved upward by the drive device 15, thereby opening the lower end gate of the hot runner bush 7, and the molten resin is filled into the cavity 3 through this lower end gate to form the molded product. [Explanation of Symbols]

[0060] 1 Fixed mold 2. Moving mold 3 Cavities 4a Tip of the manifold 4D manifold tip surface 5 Sprue 6 Hot Runner 7 Hot Runner Bushings 9a Heat-generating part 9b Non-heating part 9c curved section 9d extension part 9. Sheathed heater 15 Drive unit 41 Connecting protrusion 41a Screw hole

Claims

1. A fixed mold equipped with a hot runner bush for supplying molten resin to the cavity, A sprue for connecting the nozzle of an injection molding machine, A manifold disposed on the above-mentioned fixed mold and having a hot runner formed from the sprue toward the hot runner bush, A drive unit having a drive unit body and a leg portion integrally provided at the lower end of the drive unit body, the leg portion being fixed on the manifold, and the upper end of a valve pin that opens and closes the lower end gate of the resin passage in the hot runner bush being connected to the drive unit, An injection molding apparatus characterized in that, on the surface in which the drive unit is arranged in the manifold, a sheathed heater is disposed between the legs of the drive unit and the outer peripheral edge of the manifold.

2. The injection molding apparatus according to claim 1, characterized in that the sprue is provided on the manifold, and the manifold is arranged spaced apart from the fixed mounting plate.

3. The injection molding apparatus according to claim 1 or 2, characterized in that a connecting projection for connecting the hot runner bush is provided on the lower surface of the manifold, and the upper end of the hot runner bush is screwed and integrated with the connecting projection.

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