Resin injection molding method that allows position of insert to be adjusted according to thickness of insert

Abstract

To provide a resin injection molding method that can cope with any variation in a thickness of an insert, even if the thickness of the insert is thinner or thicker than a resin layer integrally molded with the insert.SOLUTION: In order to prevent an insert 12 fitted onto a core pin 13 from moving from its position, and also to prevent the insert 12 from being displaced by a resin pressure when molten resin 4 is injected into a cavity 5, a plurality of types of coil compression springs 18 having different repulsive forces are prepared in advance after calculating a required torque. From among the plurality of types of coil compression springs 18, an appropriate coil compression spring 18 is selected and arranged on a disk-shaped fixed plate 14 to which the insert 12 is fitted.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a resin injection molding method that can mold a resin layer firmly and precisely integrally with an insert, even if the thickness of the insert varies, i.e., the insert is sometimes thinner and sometimes thicker than the resin layer that is molded integrally with the insert, by adjusting the position of the insert during molding, without crushing the insert, without producing burrs in the molded resin layer, and without risk of mold wear. [Background technology]

[0002] The conventional resin injection molding method has been used without any consideration of variations in the thickness of the insert, such as being thinner or thicker than the resin layer molded integrally with the insert.

[0003] In light of the current situation, we conducted a retrospective search to determine whether prior patent documents disclosed a resin injection molding method that can mold a resin layer firmly and precisely into an insert even when the thickness of the insert varies, by adjusting the position of the insert and molding it, without crushing the insert, causing burrs in the molded resin layer, or wearing out the mold, but we were unable to find a single prior patent document. Summary of the Invention [Problem to be solved by the invention]

[0004] Figure 6 is a schematic longitudinal cross-sectional view of a key part showing the state in which, in a conventionally widely used resin injection molding method, when the insert is thinner than the resin layer to be molded integrally with the insert, the thin insert is inserted into a core pin protruding from the fixed mold, and then a movable mold is clamped to the fixed mold, molten resin is injected into the cavity, and a resin layer is molded integrally around the outer periphery of the insert. That is, as shown in FIG. 6, when an insert 63 inserted into a core pin 62 fixed to a fixed mold 61 is thinner than a resin layer 64 to be molded integrally with the outer periphery of the insert 63, even if a movable mold 65 is clamped to the fixed mold 61, molten resin 67 is injected into a cavity 66, and the molten resin 67 is solidified to mold the resin layer 64 integrally with the outer periphery of the insert 63, a part of the resin layer 64 becomes a coating portion 68 that covers the insert 63 and becomes a burr, preventing the insert 63 from fulfilling its function. Furthermore, the burr-like coating portion 68 comes into contact with a front end surface 69 of the fixed mold 61, and as the molten resin 67 solidifies, there is a problem that the insert 63 is crushed or damaged, or the front end surface 69 of the fixed mold 61 is worn. 6 shows the state before the mold is clamped and the molten resin 67 injected into the cavity 66 is solidified to form the resin layer 64, but since the shape of the resin layer 64 molded by solidifying the molten resin 67 is exactly the same as the shape of the molten resin 67 shown in the figure, for convenience of explanation, Figure 6 has been described as also showing the state after the layer 64 has been formed and before the mold is opened. Also in the figure, 70 is a sprue that injects the molten resin 67 into the cavity 66 from a hopper (not shown).

[0005] Also, Figure 7 is a schematic longitudinal cross-sectional view of a key part showing the state in which, in a conventionally widely used resin injection molding method, when the insert is thicker than the resin layer to be molded integrally with the insert, the thick insert is inserted into a core pin protruding from the fixed mold, and then the movable mold is clamped to the fixed mold, and molten resin is injected into the cavity to mold the resin layer integrally around the outer periphery of the insert. That is, as shown in FIG. 7, when an insert 73 inserted into a core pin 72 fixed to a fixed mold 71 is thicker than a resin layer 74 to be molded integrally with the outer periphery of the insert 73, even if a movable mold 75 is clamped to the fixed mold 71, molten resin 77 is injected into a cavity 76, and the molten resin 77 is solidified to mold the resin layer 74 integrally with the outer periphery of the insert 73, part of the resin layer 74 becomes a protrusion 78, which is crushed during molding, so that the protrusion 78 comes into contact with a front end surface 79 of the fixed mold 71, and as the molten resin 77 solidifies, the insert 73 is crushed or damaged, or the front end surface 79 of the fixed mold 71 is worn. 7 shows the state before the mold is clamped and the molten resin 77 injected into the cavity 76 is solidified to form the resin layer 74, but since the shape of the resin layer 74 molded by solidifying the molten resin 77 is exactly the same as the shape of the molten resin 77 shown in the figure, for convenience of explanation, Figure 7 has been described as also showing the state after the resin layer 74 has been formed and before the mold is opened. Also in the figure, 80 denotes a sprue that injects the molten resin 77 into the cavity 76 from a hopper (not shown).

[0006] The present invention has been made to solve the above-mentioned problems, and even if there is variation in the thickness of the insert, that is, the insert may be thinner or thicker than the resin layer molded integrally with the insert, the rear end face of the insert inserted into the core pin does not come into contact with the fixed mold, but rather the rear end face is formed to come into contact with the front end face of a disk-shaped fixed plate that fixes the base end of the core pin into which the insert is inserted and is inserted into a concave guide hole, and any of a plurality of types of coil compression springs, prepared in advance with calculated torque, is detachably attached to the spring insertion shaft of the disk-shaped fixed plate. When the insert is thin, the disk-shaped fixed plate advances while sliding within the guide hole, and when the insert is thick, the disk-shaped fixed plate retreats while sliding within the guide hole, and the disk-shaped fixed plate is fixed so that it does not move even due to the resin pressure of the molten resin injected into the cavity due to the repulsive force of the coil compression spring, so that even when a thin insert is molded, the insert does not get burrs, and even when a thick insert is molded, the insert does not come into contact with the fixed mold, so there is no risk of the fixed mold being crushed or worn out. [Means for solving the problem]

[0007] The present invention solves the above problem by adopting a means in which, even if the thickness of the insert varies, that is, the insert is sometimes thinner and sometimes thicker than the resin layer molded integrally with the insert, the rear end face of the insert inserted into the core pin does not abut against the fixed mold, but is formed so that the rear end face abuts against the front end face of a disk-shaped fixed plate that fixes the base end of the core pin into which the insert is inserted and is inserted into a concave guide hole, while one of several types of coil compression springs, prepared in advance with calculated torque, is detachably attached to the spring insertion shaft of the disk-shaped fixed plate, so that when the insert is thin, the disk-shaped fixed plate advances while sliding within the guide hole, and when the insert is thick, the disk-shaped fixed plate retreats while sliding within the guide hole, adjusting the position of the insert together with the disk-shaped fixed plate, and molding is performed while fixing the disk-shaped fixed plate so that it does not move due to the repulsive force of the coil compression spring, even when the resin pressure of the molten resin injected into the cavity is applied. [Effects of the Invention]

[0008] According to the present invention having the above configuration, even if the thickness of the insert varies, being either thin or thick, the rear end surface of the insert inserted into the core pin does not come into contact with the fixed mold, but is formed so that the rear end surface comes into contact with the front end surface of the disk-shaped fixed plate that fixes the base end of the core pin into which the insert is inserted and is inserted into the concave guide hole, while any of a plurality of types of coil compression springs, the torque of which is calculated in advance, is detachably attached to the spring insertion shaft of the disk-shaped fixed plate, so that the position of the disk-shaped fixed plate on which the insert is set can be freely adjusted, and the disk-shaped fixed plate can be molded while being fixed so that it does not move due to the resin pressure of the molten resin injected into the cavity, by the repulsive force of the coil compression spring. Therefore, even if a thin insert is molded, the insert will not be covered with burrs, and even if a thick insert is molded, the insert will not come into contact with the fixed mold, so there is no risk of the fixed mold being crushed or worn, which is an excellent effect. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing the state before the fixed mold and the movable mold are clamped together after the insert is inserted into the core pin in the resin injection molding method of the present invention using a thin insert. FIG. [Figure 2] 1 is a schematic cross-sectional view showing a state in which a movable mold is clamped to a fixed mold in a resin injection molding method of the present invention using a thin insert. [Figure 3] FIG. 1 is a perspective view, seen from the rear side, of a molded product molded by the resin injection molding method of the present invention using a thin insert. [Figure 4] 1 is a schematic cross-sectional view showing a state in which a movable mold is clamped to a fixed mold in a resin injection molding method of the present invention using a thick insert. [Figure 5] FIG. 1 is a perspective view, seen from the rear side, of a molded product molded by the resin injection molding method of the present invention using a thick insert. [Figure 6] This is a schematic vertical cross-sectional view of the main parts showing the state in which, in a conventionally widely used resin injection molding method, when the thickness of the insert is thinner than the resin layer to be molded integrally with the insert, a movable mold is clamped to a fixed mold, molten resin is injected into the cavity, and a resin layer is molded integrally around the outer periphery of the insert. [Figure 7] This is a schematic longitudinal cross-sectional view of the main parts showing the state in which, in a conventionally widely used resin injection molding method, when the thickness of the insert is thicker than the resin layer to be molded integrally with the insert, a movable mold is clamped to a fixed mold, molten resin is injected into the cavity, and a resin layer is molded integrally around the outer periphery of the insert. [Example]

[0010] The resin injection molding method of the present invention will be described in detail with reference to the drawings. Figures 1 and 2 are schematic cross-sectional views showing an embodiment of the resin injection molding method of the present invention using a thin insert. Figure 1 shows the state before the fixed mold and movable mold are clamped, and Figure 2 shows the state after the movable mold is clamped to the fixed mold. In Figure 1, the fixed mold 1 and movable mold 2 are shown in the state before clamping, and the fixed mold 1 is fixed integrally to the front surface of the fixed mold mounting frame 3. As shown in Figure 2, the fixed mold mounting frame 3 is configured so that molten resin 4 can be injected into a cavity 5 from a hopper (not shown) via a sprue 6 and a runner 7.

[0011] A concave guide hole 9 is recessed in the front end surface 8 where the fixed mold 1 contacts the movable mold 2, with an opening 10 facing toward the movable mold 2, and a core pin 13 for inserting a thin insert 12 with an insertion hole 11 therethrough is inserted into the guide hole 9. The outer surface 15 of a disk-shaped fixed plate 14 having a protruding core pin 13 protruding toward the movable mold 2 is inserted into the guide hole 9 so that the outer surface 15 can move while sliding against the inner wall surface 16 of the guide hole 9, and the thin insert 12 is inserted into the core pin 13 so that the rear end surface 17 of the thin insert 12 inserted into the core pin 13 abuts only against the disk-shaped fixed plate 14 without abutting against the fixed mold 1.

[0012] The coil compression spring 18 adjusts the position of the disk-shaped fixing plate 14 inserted into the guide hole 9 and also adjusts the position of the insert 12. To prevent the disk-shaped fixing plate 14, which fixes the thin insert 12, from sliding against the inner wall surface 16 of the guide hole 9 due to the resin pressure when the molten resin 4 is injected into the cavity 5, the torque of the coil compression spring 18 is calculated in advance, and multiple types of coil compression springs 18 with different repulsive forces (spring forces) are prepared.A predetermined coil compression spring 18 corresponding to the resin pressure is appropriately selected, and the selected coil compression spring 18 is detachably inserted into a spring insertion shaft 19 protruding from the center of the rear end wall surface of the disk-shaped fixing plate 14, with its tip pressed against the disk-shaped fixing plate 14 and its rear end pressed against the rear end wall surface 20 of the guide hole 9. The torque of the coil compression spring 18 is calculated and set based on the area of ​​the molded product, the injection pressure of the molten resin, and the like.

[0013] In other words, when the disk-shaped fixed plate 14 with the thin insert 12 set in the fixed mold 1 is first inserted into the guide hole 9 in a springy state, the disk-shaped fixed plate 14 is fixed in that position without moving, and then the coil pusher spring 18 has a calculated torque so that the disk-shaped fixed plate 14 does not move back even when the movable mold 2 is clamped to the fixed mold 1 and the resin pressure of the molten resin 4 injected into the cavity 5 occurs.

[0014] On the other hand, the movable mold 2 that is clamped to the fixed mold 1 is formed with a long recess 21 that receives the tip end of the core pin 13 of the fixed mold 1 and a cavity forming recess 22 for forming the cavity 5.

[0015] When a thin insert 12 is set in the fixed mold 1 having the above-described configuration, the front portion of the disk-shaped fixed plate 14, to which the base end of the core pin 13 with the thin insert 12 inserted therein is fixed, protrudes slightly from the front end surface 8 of the fixed mold 1 toward the movable mold 2 through the guide hole 9 to form a protrusion 23, and the rear side of the cavity 5 is set with an annular protrusion 24 protruding rearward so as to surround the outer peripheral surface of the protrusion 23 of the disk-shaped fixed plate 14.

[0016] After the thin insert 12 has been set, molten resin 4 is injected into the cavity 5. The molten resin 4 injected into the annular protrusion 24 of the cavity 5 comes into contact with the front end surface 8 of the fixed mold 1. However, even if the protrusion 23 of the disk-shaped fixed plate 14 is pressed by the resin pressure of the molten resin 4 against the concave inner peripheral wall surface 25 of the annular protrusion 24 of the cavity 5, the repulsive force of the coil compression spring 18 prevents the disk-shaped fixed plate 14 with the thin insert 12 set therein from moving rearward. In this state, the molten resin 4 solidifies, and when the mold is opened, a molded product 29 is obtained, as shown in FIG. 3, in which a resin layer 26 is integrally formed around the outer periphery of the thin insert 12. To produce the final product, the sprue 6 and runner 7 of the molded product 29 are cut and removed.

[0017] As shown in Figure 3, the molded product 29 of the thin insert 12 molded as described above has the outer periphery of the thin insert 12 integrally molded with the resin layer 26, the front side of the thin insert 12 and the resin layer 26 formed flush, and the rear side of the thin insert 12 and the resin layer 26 has an annular protrusion 24 protruding from the outer periphery of the resin layer 26, surrounding the thin insert 12 and integrally molded. Although the annular protrusion 24 surrounds the thin insert 12, it does not cover the thin insert 12 and therefore does not form a burr. Furthermore, since the thin insert 12 does not come into contact with the fixed mold 1 at all, there is no risk of the insert 12 being crushed during molding, or the fixed mold 1 being worn down due to the contact pressure of the insert 12.

[0018] When replacing the coil compression spring 18, the disk-shaped fixing plate 14 to which the core pin 13 is fixed is pulled out from the guide hole 9, the coil compression spring 18 that has been used until now is removed, and a new coil compression spring 18 is inserted into the spring insertion shaft 19 to replace it.

[0019] Fig. 4 is a schematic cross-sectional view showing an embodiment of the resin injection molding method of the present invention using a thick insert, showing the movable mold clamped to the fixed mold. Although the drawing corresponding to Fig. 1 is omitted, the only difference from Fig. 1 is that the thin insert 12 becomes the thick insert 31 and the shape of the cavity 32 is designed to accommodate the thick insert 31. Other components are identical to those in Fig. 1, so in Fig. 4, the same reference numerals as in Fig. 2 are used for components other than the thick insert 31, cavity 32, and associated components, and the explanation of the components will be omitted without further explanation.

[0020] When a thick insert 31 is inserted into the core pin 13 of the fixed mold 1 having the above-described configuration, the front part of the disk-shaped fixed plate 14 to which the thick insert 31 is attached is set back slightly inward from the front end face 8 of the fixed mold 1 through the guide hole 9 to form a recessed portion 33, and the rear side of the cavity 32 is set with an annular protrusion 34 protruding rearward so that the recessed portion 33 of the disk-shaped fixed plate 14 is embedded.

[0021] After the thick insert 31 has been set, molten resin 4 is injected into the cavity 32, and the molten resin 4 on the outer periphery 35 of the annular protrusion 34 of the cavity 32 comes into contact with the front end surface 8 of the fixed mold 1. However, even if the recessed portion 33 of the disk-shaped fixed plate 14 is pressed by the resin pressure of the molten resin 4 on the annular protrusion 34 of the cavity 32, the repulsive force of the coil compression spring 18 prevents the disk-shaped fixed plate 14 with the thick insert 31 set therein from moving rearward. In this state, the molten resin 4 solidifies, and when it is removed from the mold, a molded product 37 is obtained, as shown in Figure 5, in which a resin layer 36 is integrally formed on the outer periphery of the thick insert 31.

[0022] 5, the molded product 37 of the thick insert 31 molded as described above has the outer periphery of the thick insert 31 integrally molded with the resin layer 36, the front side surfaces of the thick insert 31 and the resin layer 36 are flush with each other, and the rear side of the thick insert 31 and the resin layer 36 are integrally molded flush with the annular protrusion 34 of the resin layer 36, and an annular outer edge 38 having a height lower than that of the annular protrusion 34 is integrally formed with the outer periphery of the annular protrusion 34. Since the annular protrusion 34 is not covered by the thick insert 31, no flash is formed. Furthermore, since the thick insert 31 does not contact the fixed mold 1 at all, there is no risk of the insert 31 being crushed during molding, or of the fixed mold 1 being worn by the contact pressure of the insert 31. To produce a final product, the sprue 6 and runner 7 of the molded product 37 are cut and removed to produce the final product. [Explanation of symbols]

[0023] 1 fixed mold, 2 movable mold, 3 fixed mold mounting frame, 4 molten resin, 5 Cavity, 6 Sprue, 7 Runner, 8 Front end surface, 9 Concave guide hole, 10 Opening, 11 Insertion hole, 12 Thin insert, 13 Core pin, 14 Disk-shaped fixing plate, 15 Outer surface, 16 Inner wall surface, 17 Rear end surface, 18 Coil compression spring, 19 Spring insertion shaft, 20 Rear end wall surface, 21 Long recess, 22 Cavity-forming recess, 23 Protruding portion, 24 Annular protruding portion, 25 Inner wall surface, 26 Resin layer, 29 Molded product, 31 Thick insert, 32 Cavity, 33 Recessed portion, 34 Annular protruding portion, 35 Outer periphery, 36 Resin layer, 37 Molded product, 38 Annular outer edge portion.

Claims

[Claim 1] A resin injection molding method characterized by the following: even if the thickness of the insert varies, that is, the insert may be thinner or thicker than the resin layer molded integrally with the insert, the rear end surface of the insert inserted into the core pin does not abut against the fixed mold, but is formed so that the rear end surface abuts against the front end surface of a disk-shaped fixed plate that fixes the base end of the core pin into which the insert is inserted and is inserted into a concave guide hole, while one of several types of coil compression springs, prepared in advance with calculated torque, is detachably attached to the spring insertion shaft of the disk-shaped fixed plate, so that when the insert is thin, the disk-shaped fixed plate advances while sliding within the guide hole, and when the insert is thick, the disk-shaped fixed plate retreats while sliding within the guide hole, adjusting the position of the insert together with the disk-shaped fixed plate, and molding is performed while fixing the disk-shaped fixed plate so that it does not move due to the resin pressure of the molten resin injected into the cavity due to the repulsive force of the coil compression spring.

Images