Injection device

Abstract

To provide an injection device that satisfactorily curbs leaking of molding resin in a molten state from a gap between an inner peripheral surface of a cylinder in a base end part of the cylinder and an outer peripheral surface of a plunger inserted into an interior space of the cylinder.SOLUTION: An injection device comprises: a cylinder in which an ejection port for injecting molding resin in a molten state is formed in a distal end part thereof; a plunger slidably inserted into an interior space of the cylinder from a base end part of the cylinder; and a seal ring formed of high melting point resin being resin having a melting point higher than that of the molding resin and attached to a ring groove formed in an outer peripheral surface of a distal end part of the plunger. The seal ring is formed such that breadth is smaller than breadth of the ring groove and an inner peripheral length is longer than a peripheral length of a bottom of the ring groove.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an injection apparatus, and particularly to a plunger-type injection apparatus. Background Art

[0002] An injection molding machine (injection molding apparatus) that manufactures a resin molded product of a predetermined shape by injecting molten molding resin into a cavity of a mold and then solidifying the resin inside the cavity is known in the art.

[0003] Patent Document 1 discloses a pre-plasticization type injection molding apparatus including: an injection cylinder having an injection port for injecting molten molding resin formed at a distal end portion thereof, and a resin discharge path formed at a proximal end portion thereof for discharging molding resin remaining in an internal space to the outside; an injection plunger inserted into the internal space from the proximal end portion of the injection cylinder; and a seal ring made of a high-melting-point resin having a higher melting point than the molding resin, the seal ring being liquid-tightly and slidably fitted onto the injection plunger and fixed to the proximal end portion of the injection cylinder. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2009-39943 Summary of the Invention Problems to be Solved by the Invention

[0005] One example of an injection molding machine's injection device is a plunger-type injection device, which injects molten molding resin supplied to the internal space of a cylinder (barrel) by advancing a plunger slidably inserted into the cylinder's internal space. In a plunger-type injection device, in order to prevent poor sliding of the plunger relative to the cylinder, it is necessary to provide a certain amount of gap between the inner circumferential surface of the cylinder at the base end of the cylinder and the outer circumferential surface of the plunger inserted into the internal space of the cylinder. As a result, molten molding resin may leak from this gap.

[0006] Leakage of molten molding resin can cause the following problems: • The amount of molding resin injected into the mold cavity decreases due to the injection device, which may lead to a decrease in raw material yield and the occurrence of short shots. • Leaked molding resin is discarded, resulting in wasted raw materials. • The removal of molding resin requires stopping production, which may lead to a decrease in productivity. • Because the leaked molding resin and injection equipment are at high temperatures, the removal work of the molding resin described above may carry the risk of injury or illness to workers, such as burns or heatstroke. Leaked molding resin may carbonize if left unattended for an extended period.

[0007] Therefore, in order to prevent leakage of the molding resin, it is conceivable to install a seal ring on the sliding surface between the inner surface of the cylinder and the outer surface of the plunger. However, even if a seal ring is installed on the sliding surface, the following problems remain. • Molding resin that accumulates in the gap between the inner surface of the cylinder at the base end and the outer surface of the plunger inserted into the internal space of the cylinder may remain there for a long time without being discharged to the outside and may deteriorate. Therefore, if deteriorated molding resin is unintentionally injected into the cavity at a time such as after mold replacement, there is a risk that the deteriorated molding resin will mix into the molded resin product, leading to product defects. To prevent product defects caused by the deterioration of the molding resin mentioned above, it is essential to periodically remove the molding resin accumulated in this gap. Although the frequency of removing the molding resin can be reduced by installing a seal ring on the sliding part, it is difficult to eliminate the frequency entirely.

[0008] Therefore, there is a need for a technology that can more reliably suppress the leakage of molten molding resin from the gap between the inner circumferential surface of the cylinder at the base end of the cylinder and the outer circumferential surface of the plunger inserted into the internal space of the cylinder.

[0009] This disclosure was made to solve such problems and aims to provide an injection molding device that effectively suppresses leakage of molten molding resin from the gap between the inner circumferential surface of the cylinder at the base end of the cylinder and the outer circumferential surface of the plunger inserted into the internal space of the cylinder. [Means for solving the problem]

[0010] An injection apparatus according to one embodiment includes a cylinder with an injection port formed at its tip for injecting molten molding resin, a plunger slidably inserted into the internal space of the cylinder from the base end of the cylinder, and a seal ring made of a high-melting-point resin, which has a higher melting point than the molding resin, and attached to a ring groove formed on the outer circumferential surface of the tip of the plunger, wherein the seal ring has a width smaller than the width of the ring groove and an inner circumference longer than the circumference of the bottom of the ring groove. [Effects of the Invention]

[0011] This disclosure provides an injection molding device that effectively suppresses leakage of molten molding resin from the gap between the inner circumferential surface of the cylinder at the base end of the cylinder and the outer circumferential surface of the plunger inserted into the internal space of the cylinder. [Brief explanation of the drawing]

[0012] [Figure 1]This is a schematic cross-sectional view showing the injection device according to Embodiment 1. [Figure 2] Figure 1 is a magnified view of a portion of the injection device shown. [Figure 3] This figure shows the verification results of the example. [Modes for carrying out the invention]

[0013] Embodiment 1 Embodiments of this disclosure will be described below with reference to the drawings. However, this disclosure is not limited to the embodiments described below. Also, for clarity, the following description and drawings have been simplified as appropriate. What is shown in the drawings is only a part of the whole, and there are actually many other components that are not shown. In the following description, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] First, Figure 1 is a schematic cross-sectional view showing an injection molding apparatus according to Embodiment 1. The injection molding apparatus 1 shown in Figure 1, when combined with a mold clamping device (not shown), constitutes an injection molding machine. An injection molding machine is a device that solidifies a molten molding resin R to produce a resin molded product of a predetermined shape. The mold clamping device can be of any type; for example, a fixed platen to which a fixed mold is attached is fixed on the bed B. In addition, a movable platen to which a movable mold is attached is provided on the bed B so as to be movable in the mold opening and closing direction on a guide provided thereon. The mold cavity is formed when the fixed mold and the movable mold are clamped together.

[0015] In the following description, "molding resin" refers to the resin material used in the injection device 1 according to this embodiment, and is mainly a thermoplastic resin. Pellet-shaped molding resin R refers to the resin material in a solid state when used in the injection device 1. Molten molding resin R refers to the resin material that has become fluid by being held above the glass transition temperature or melting point. "Resin molded product" refers to an article molded into a predetermined shape by solidifying the molten molding resin R.

[0016] As shown in FIG. 1, the injection device 1 is mounted on a bed B. The injection device 1 includes a base 11, an intermediate support 12, and a rear support 13 as support sections. Further, the injection device 1 includes a barrel 21, a plunger 22, and a screw 23 as an injection section. Further, the injection device 1 includes a first drive means 31, a second drive means 32, a third drive means 33, and a rotation drive means 34 as a drive section. Hereinafter, the details of the injection device 1 will be described, with the distal end side of the injection device 1 (the left side in FIG. 1) defined as the front and the proximal end side of the injection device 1 (the right side in FIG. 1) defined as the rear.

[0017] The injection device 1 supplies molten molding resin R into the internal space S1 of the barrel 21 by rotation of the screw 23, which is rotatably disposed in the internal space S2 of the plunger 22 inserted into the internal space S1 of the barrel 21, and advances the plunger 22 and the screw 23 relative to the barrel 21 to inject the molten molding resin R supplied into the internal space S1 into a cavity of a mold. The molding resin R is, for example, polypropylene (PP). The melting point of PP is approximately 110°C to 170°C.

[0018] [Support Section] The base 11 is provided so as to be movable in the front-rear direction relative to the bed B by the first drive means 31. The intermediate support 12 is mounted on the proximal end portion of the base 11. The intermediate support 12 is provided so as to be movable in the front-rear direction relative to the base 11 by the second drive means 32. The intermediate support 12 is a member that supports the plunger 22. The rear support 13 is mounted on the proximal end portion of the intermediate support 12. The rear support 13 is provided so as to be movable in the front-rear direction relative to the intermediate support 12 by the third drive means 33. The rear support 13 is a member that supports the rotation drive means 34. Further, the barrel 21 is fixed to the distal end portion of the base 11.

[0019] [Injection Section] The barrel 21 is a specific example of a cylinder. The barrel 21 is a substantially cylindrical member extending in the front-rear direction. The barrel 21 incorporates first heating means 21a such as a plurality of cartridge heaters extending in the circumferential direction. The first heating means 21a heats the molding resin R supplied into the internal space S1. Further, an injection port 21c for injecting the molten molding resin R is formed in the cylinder head 21b, which is the tip end portion of the barrel 21. The injection port 21c is formed at the tip of the cylinder head 21b. A nozzle 211 is attached to the tip of the cylinder head 21b. The nozzle 211 has an opening / closing mechanism 211a such as a shutoff valve that closes the injection port 21c. The injection port 21c communicates with a cavity of a mold via the nozzle 211. The base end of the barrel 21 is open. A plunger 22 is slidably disposed in the internal space S1. Since the inner diameter of the barrel 21 is slightly larger than the outer diameter of the plunger 22, a gap CL1 is formed between the inner circumferential surface 21s of the barrel 21 at the base end portion of the barrel 21 and the outer circumferential surface 22s of the plunger 22 inserted into the internal space S1.

[0020] The plunger 22 is a substantially cylindrical member extending in the front-rear direction. The plunger 22 is slidably inserted into the internal space S1 from the base end portion of the barrel 21. The plunger 22 is a member for pushing out the molten molding resin R supplied into the internal space S1 to inject it from the injection port 21c. The plunger 22 incorporates second heating means 22a such as a plurality of cartridge heaters extending in the circumferential direction. The second heating means 22a heats the molding resin R supplied into the internal space S2. Further, a discharge port 22c for discharging the molten molding resin R is formed in the plunger head 22b, which is the tip end portion of the plunger 22. The discharge port 22c is formed at the tip of the plunger head 22b. The discharge port 22c has a tapered shape whose diameter decreases toward the tip.

[0021] At least one ring groove 22d is formed on the outer circumferential surface 22s of the plunger head 22b. A seal ring 40, which is a component that prevents molten molding resin R from leaking from the gap CL1, is attached to the ring groove 22d. Preferably, multiple ring grooves 22d are provided on the outer circumferential surface 22s of the plunger head 22b so as to be spaced apart from each other in the front-rear direction. By attaching a seal ring 40 to each of the multiple ring grooves 22d, leakage of molten molding resin R from the gap CL1 when the injection device 1 performs an injection operation can be further suppressed. The ring grooves 22d only need to be provided on the sliding portion of the outer circumferential surface 22s of the plunger 22 that slides against the inner circumferential surface 21s, and their position in the front-rear direction is not particularly limited as long as it does not interfere with the sealing force of the seal ring 40. In the injection device 1 shown in Figure 1, three ring grooves 22d are provided on the outer circumferential surface 22s of the tip of the plunger head 22b so as to be spaced apart from each other in the front-rear direction. A sealing ring 40 is fitted into each ring groove 22d.

[0022] The seal ring 40 is a ring-shaped component. The seal ring 40 is made of a high-melting-point resin, which has a higher melting point than the molding resin R. By maintaining the temperature of the molten molding resin R filling the internal space S1 at a temperature higher than the melting point of the molding resin R and lower than the melting point of the high-melting-point resin (more preferably lower than the continuous use temperature of the high-melting-point resin), the seal ring 40 will not melt even if the molten molding resin R comes into contact with it. The high-melting-point resin is, for example, polyetheretherketone (PEEK). The melting point of PEEK is 334°C (typical value), and its continuous use temperature is 250°C (according to UL796B).

[0023] A hopper 231 is attached to the base end of the plunger 22. The hopper 231 is a funnel-shaped member for supplying pelletized molding resin R to the plunger 22. An inlet 231a for introducing pelletized molding resin R is formed on the upper surface of the hopper 231. The lower end of the hopper 231 forms a material supply passage 231b. The material supply passage 231b communicates with the internal space S2. The base end of the plunger 22 is open. A screw 23 is rotatably arranged in the internal space S2.

[0024] The screw 23 is a component with helical vanes 23a formed on its outer surface. The screw 23 is inserted into the internal space S1 from the base end of the plunger 22. The screw 23 is a component for supplying molten molding resin R to the internal space S1 by melting the pellet-shaped molding resin R supplied to the internal space S2 and discharging the molten molding resin R from the discharge port 22c. The screw 23 has a backflow prevention mechanism 23b, such as a check ring, at its tip. The base end of the screw 23 is rotatably supported by the rear support portion 13 via the output shaft 34d.

[0025] [Drive unit] The first drive means 31 moves the base 11 in the front-rear direction. The first drive means 31 includes an electric motor 31a and a ball screw 31b including a ball screw shaft and a ball screw nut. The ball screw shaft of the ball screw 31b is rotatably supported on the bed B by bearings 61 and 62. The ball screw nut of the ball screw 31b is fixed to the base 11 in a non-rotatable manner. When the electric motor 31a rotates forward or backward, the ball screw shaft of the ball screw 31b rotates forward or backward. As a result, the base 11 moves back and forth along with the ball screw nut of the ball screw 31b that is screwed onto the ball screw shaft. As the base 11 moves, the intermediate support part 12, the rear support part 13, the injection part, the second drive means 32, the third drive means 33, and the rotation drive means 34 move in the front-rear direction. Note that the first drive means 31 can be omitted if it is not necessary to move the base 11.

[0026] The second drive means 32 moves the plunger 22 together with the screw 23 in the front-rear direction. The second drive means 32 includes an electric motor 32a and a ball screw 32b including a ball screw shaft and a ball screw nut. The ball screw shaft of the ball screw 32b is rotatably supported on the base 11 by bearings 63 and 64. The ball screw nut of the ball screw 32b is fixed non-rotatably to the intermediate support part 12. When the electric motor 32a rotates forward or backward, the ball screw shaft of the ball screw 32b rotates forward or backward. As a result, the intermediate support part 12 reciprocates in the front-rear direction together with the ball screw nut of the ball screw 32b that is screwed onto the ball screw shaft. As the intermediate support part 12 moves, the rear support part 13, the plunger 22, the screw 23, the third drive means 33, and the rotation drive means 34 move in the front-rear direction.

[0027] The third drive means 33 moves the screw 23 in the front-rear direction. The third drive means 33 includes an electric motor 33a and a ball screw 33b including a ball screw shaft and a ball screw nut. The ball screw shaft of the ball screw 33b is rotatably supported on the intermediate support portion 12 by bearings 65 and 66. The ball screw nut of the ball screw 33b is fixed non-rotatably to the rear support portion 13. When the electric motor 33a rotates forward or backward, the ball screw shaft of the ball screw 33b rotates forward or backward. As a result, the rear support portion 13 reciprocates in the front-rear direction together with the ball screw nut of the ball screw 33b that is screwed onto the ball screw shaft. As the rear support portion 13 moves, the screw 23 and the rotation drive means 34 move in the front-rear direction.

[0028] The rotational drive means 34 rotates the screw 23. The rotational drive means 34 includes an electric motor 34a, an output pulley 34c fixed to the output shaft 34b of the electric motor 34a, an input pulley 34e fixed to the output shaft 34d connected to the base end of the screw 23, and a transmission belt (not shown) wrapped between the output pulley 34c and the input pulley 34e. The rotational driving force of the electric motor is transmitted to the output shaft via the drive force transmission mechanism, which includes the output pulley 34c, the input pulley 34e, and the transmission belt, causing the screw 23 to rotate. The drive force transmission mechanism may include a reduction gear or the like instead of the output pulley 34c, the input pulley 34e, and the transmission belt.

[0029] In the injection device 1 described above, when pellet-shaped molding resin R is supplied from the input port 231a to the internal space S3 of the hopper 231, the molding resin R slides down through the material supply path 231b and moves into the internal space S2 of the plunger 22. When the screw 23 is rotated by the rotational drive means 34, the molding resin R that has moved to the internal space S2 moves along the helical groove of the screw 23 toward the discharge port 22c, and mechanical energy (friction between the molding resins R, shear by the inner surface of the plunger 22 and the screw 23) is applied to the molding resin R. As a result, the temperature of the molding resin R rises and it melts. The injection device 1 supplies the molten molding resin R to the internal space S1 by rotating the screw 23, and also advances the plunger 22 and screw 23 relative to the barrel 21 to inject the molten molding resin R supplied to the internal space S1 from the injection port 21c.

[0030] Next, Figure 2 is a partially enlarged view of the injection device 1 shown in Figure 1. Figure 2 is an enlarged cross-sectional view of the area around one seal ring 40 (the seal ring 40 located on the foremost side) in the injection device 1. One of the features of the injection device 1 according to this embodiment is the sealing structure in which the gap CL1 is sealed by the seal ring 40. Therefore, the sealing structure of the injection device 1 will be described in detail with reference to Figure 2.

[0031] The seal ring 40 is attached to the ring groove 22d such that its outer peripheral surface 40a abuts against its inner peripheral surface 21s and at least a portion of its rear end surface 40b abuts against the rear wall surface 22f of the ring groove 22d. Furthermore, the seal ring 40 has a width W1 smaller than the width W2 of the ring groove 22d, and its inner circumference (the circumferential length of the inner peripheral surface 40c of the seal ring 40) is longer than the circumference of the bottom 22e of the ring groove 22d (the circumferential length of the bottom 22e). As a result, when the injection device 1 performs an injection operation, the molten molding resin R supplied to the internal space S1 is guided into the gap CL2 between the seal ring 40 and the ring groove 22d. When the molten molding resin R fills the gap CL2 in this manner, pressure P from the molten molding resin R moving from the seal ring 40 toward the wall surface 22f and pressure P from the molten molding resin R moving from the seal ring 40 toward the inner circumferential surface 21s are applied to the seal ring 40. The pressure P from the molten molding resin R moving from the seal ring 40 toward the wall surface 22f increases the adhesion force of the seal ring 40 to the barrel 21, and the pressure P from the molten molding resin R moving from the seal ring 40 toward the inner circumferential surface 21s increases the adhesion force of the seal ring 40 to the plunger 22. Therefore, because the width W1 of the seal ring 40 is smaller than the width W2 of the ring groove 22d, and the inner circumference of the seal ring 40 is longer than the circumference of the bottom 22e, the sealing force of the seal ring 40 is improved. As a result, leakage of the molten molding resin R from the gap CL1 is suppressed.

[0032] Here, if the width W1 is too small, the contact area between the inner circumferential surface 21s and the outer circumferential surface 40a will be small, which may result in insufficient sealing force from the seal ring 40. On the other hand, if the width W1 is too large, the contact area between the inner circumferential surface 21s and the outer circumferential surface 40a will be large, which may increase the sliding resistance of the plunger 22. Also, if the gap CL2 is too small, the seal ring 40 will not receive pressure P easily, which may result in insufficient sealing force from the seal ring 40. On the other hand, if the gap CL2 is too large, the seal ring 40 will behave within the ring groove 22d, which may result in insufficient sealing force from the seal ring 40 or even complete sealing failure. Furthermore, the adhesion force of the seal ring 40 to the barrel 21 and the plunger 22 increases as the pressure P increases due to the reaction force of the pressure P. Therefore, the sealing force from the seal ring 40 changes according to the pressure P.

[0033] (Examples) The injection apparatus 1 will be described in more detail below with reference to an example. However, the example is not limited to this disclosure. In this example, the injection apparatus 1, which has the following apparatus conditions, was subjected to injection operation under the following injection conditions, with the nozzle 211 having an opening / closing mechanism 211a replaced with a throttling nozzle. In this example, PP was used as the molding resin R, and PEEK was used as the high-melting-point resin.

[0034] [Equipment conditions] • Barrel 21 inner diameter: 105.0 mm • Outer diameter of plunger 22: 104.9 mm • Quantity of seal rings 40: 3 • Width W1 of seal ring 40 relative to a 1.0mm gap CL2: 4.0mm, 6.0mm, 6.5mm, 6.8mm, 7.0mm • Distance of gap CL2 relative to width W1 of 6.0 mm: 1.0 mm, 0.4 mm, 0.2 mm, 0.08 mm [Injection conditions] • Temperature of internal space S1 (all zones): 220℃ • Plunger 22 forward starting position: 430mm • Plunger 22 forward stop position: 30mm • Injection pressure (pressure in internal space S1): 160 MPa

[0035] Then, the following leak tests were conducted to verify the relationship between the width W1 and the amount of molding resin R leaked, and the relationship between the distance of the gap CL2 and the amount of molding resin R leaked. The amount of molding resin R leaked refers to the amount of molding resin R that leaked to the outside from the gap CL1 when the injection device 1 performed the injection operation. The distance of the gap CL2 is the distance between the front end face 40d of the seal ring 40 attached to the ring groove 22d and the rear wall surface 22g of the ring groove 22d, and is the difference between the width W1 and the width W2.

[0036] [Leak testing methods] 1. The injection operation of the injection device 1 was started under hydrostatic pressure generated by setting the aperture nozzle aperture to "fully closed," and then the injection operation was stopped. The device conditions and injection conditions of the injection device 1 in step 1 are as described above. 2. The amount of change in the position of the plunger 22 was measured based on the starting position of the plunger 22 when the injection operation began and the stopping position of the plunger 22 when the injection operation stopped. 3. The forward speed (mm / s) of the plunger 22 was calculated from the amount of change in the position of the plunger 22 measured in step 2. 4. Using the specific gravity of the molding resin R, the forward speed of the plunger 22 calculated in step 3 was converted to the leakage rate (g / s).

[0037] [Verification Results] Figure 3 shows the verification results. Graph G1, shown at the top of Figure 3, represents the relationship between the width W1 of the seal ring 40 and the amount of molding resin R leakage when the gap CL2 distance is 1.0 mm. As shown in Graph G1, when the width W1 is between 4.0 and 6.5 mm, the amount of leakage decreases as the width W1 increases, and when the width W1 is between 6.5 and 7.0 mm, the amount of leakage is zero. Graph G2, shown at the bottom of Figure 3, represents the relationship between the gap CL2 distance and the amount of molding resin R leakage when the width W1 of the seal ring 40 is 6.0 mm. As shown in Graph G2, when the gap CL2 distance is between 1.0 and 0.2 mm, the amount of leakage decreases as the gap CL2 distance decreases, but when the gap CL2 distance is 0.08 mm, the amount of leakage increases compared to when the gap CL2 distance is 0.2 mm.

[0038] From the verification results shown in Figure 3, it is particularly preferable that the width W1 is 6.5 to 7.0 mm when the gap CL2 is 1.0 mm. Also, from the above verification results, it is particularly preferable that the gap CL2 is 0.2 mm when the width W1 is 6.0 mm. In this way, the injection device 1 can significantly reduce leakage by adjusting at least one of the width W1 relative to the width W2 and the gap CL2 relative to the width W2. Therefore, according to the injection device 1 of this embodiment, it is possible to effectively suppress leakage of molten molding resin R from the gap CL1.

[0039] Here, for example, if the pressure P is excessively large, the seal ring 40, which is subjected to the pressure P, will be excessively pressed against the barrel 21, which can lead to wear of the seal ring 40, galling between the inner circumferential surface 21s and the outer circumferential surface 22s, and an increase in the sliding resistance of the plunger 22. In contrast, in the injection device 1 according to this embodiment, a suitable pressure P can be obtained by adjusting at least one of the width W1 relative to the width W2 and the gap CL2 relative to the width W2, thereby suppressing excessive pressing of the seal ring 40, which is subjected to the pressure P, against the barrel 21. As a result, wear of the seal ring 40, galling between the inner circumferential surface 21s and the outer circumferential surface 22s, and an increase in the sliding resistance of the plunger 22 are suppressed.

[0040] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0041] 1 Injection device 1 11 Base 12 Intermediate support section 13 Rear support section 21 Barrel 21a First heating means 21b Cylinder head 21c Injection port 21s Inner surface 22 Plunger 22a Second heating means 22b Plunger head 22c Outlet 22s Outer surface 22d Ring groove 22e Bottom 22f, 22g Wall surface 23 Screw 23a Blade 23b Backflow prevention mechanism 31 First driving means 31a Electric motor 31b Ball screw 32 Second driving means 32a Electric motor 32b Ball screw 33 Third driving means 33a Electric motor 33b Ball screw 34 Rotary drive means 34a Electric motor 34b, 34d Output shaft 34c output pulley, 34e input pulley 40 Seal ring 40a Outer surface 40b, 40d End surface 40c Inner surface 61-66 Bearings 211 Nozzle 211a Opening / Closing Mechanism 231 Hopper 231a Inlet 231b Material supply path B Bed CL1, CL2 Gap G1, G2 Graph P Pressure R Molding resin S1, S2, S3 Internal space W1, W2 Width

Claims

1. A cylinder with an injection port formed at its tip for injecting molten molding resin, A plunger is slidably inserted into the internal space of the cylinder from the base end of the cylinder, It has a seal ring that is made of a high-melting-point resin, which has a higher melting point than the aforementioned molding resin, and is attached to a ring groove formed on the outer circumferential surface of the tip of the plunger, Multiple ring grooves are provided on the outer circumferential surface of the tip of the plunger, spaced apart from each other, and the seal ring is attached to each ring groove. Each seal ring in the injection device has a width smaller than the width of the ring groove and an inner circumference longer than the circumference of the bottom of the ring groove.

2. The injection apparatus according to claim 1, wherein with respect to each seal ring, at least one of the width of the seal ring relative to the width of the ring groove and the distance between the ring groove and the seal ring relative to the width of the ring groove is adjusted.

3. With respect to each seal ring, the width of the seal ring is 6.0 to 7.0 mm and the distance between the ring groove and the seal ring is 1.0 mm, or The injection device according to claim 1, wherein the width of the seal ring is 6.0 mm and the distance between the ring groove and the seal ring is 0.08 to 1.0 mm.

4. With respect to each seal ring, the width of the seal ring is 6.5 to 7.0 mm and the distance between the ring groove and the seal ring is 1.0 mm, or The injection device according to claim 3, wherein the width of the seal ring is 6.0 mm and the distance between the ring groove and the seal ring is 0.2 mm.

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