JP4835225B2 - Injection device for plunger type injection molding machine - Google Patents

Description

  The present invention relates to an injection device of a plunger type injection molding machine that injects a molten resin plasticized and sent by a plasticizing device with an injection plunger.

  As a plasticizer for a plunger type injection molding machine, a screw preplasticizer type plasticizer is often used practically. Therefore, a plunger type injection molding machine that injects a molten resin plasticized by a screwprepula type plasticizer. Is described below. In the screw pre-plasticizer, a plasticizing screw is provided in a plasticizing chamber, and a communication passage with a check valve that connects the plasticizing chamber and the injection chamber is provided between the plasticizing device and the injection device. . First, the raw material resin supplied from the hopper to the plasticizing chamber is kneaded and melted by rotation of the plasticizing screw and heating of the plasticizing chamber (hereinafter referred to as plasticization), and the plasticized resin is communicated with the communication path. Through the injection chamber. At this time, the retraction amount of the injection plunger that retreats with the pressure feeding is detected, and the plasticization amount of the resin is measured. Next, the injection plunger moves forward, and the molten resin in the injection chamber is injected into the mold cavity.

  In such an injection plunger type injection device, the plunger shaft of the injection plunger has a smaller diameter than the plunger head so that the injection plunger does not bite the injection cylinder during forward and backward movement. A step is formed between the two. A gap is secured between the plunger head and the inner wall of the injection cylinder. For this reason, during the injection operation of filling the mold with molten resin at high pressure, the molten resin leaks from the gap between the plunger head and the cylinder inner wall, and the gap between the plunger head and the injection cylinder inner wall, and the plunger shaft It collects in a gap between the inner wall of the injection cylinder. During a long injection operation, this leaked resin (hereinafter referred to as leaked resin) is pushed by the step portion of the plunger head and pushed backward along the plunger shaft, and the rear portion of the injection cylinder or The resin is eventually discharged from a resin discharge port provided in the vicinity of the rear end. At this time, if the leaked resin is not smoothly discharged, the accumulated leaked resin becomes a weir and hinders the backward movement of the injection plunger, which hinders the weighing process.

Therefore, a plunger type injection molding machine provided with a discharge mechanism for discharging the leaked resin out of the injection cylinder has been proposed. For example, there has been proposed one in which a resin drain hole 16 is provided directly in the injection cylinder and a sleeve 19 for scraping off the leaked resin around the plunger shaft is provided immediately after the resin drain hole (see, for example, Patent Document 1).
JP-A-9-85787

  As described above, conventionally, the molten resin leaks from the gap between the plunger head and the inner wall of the cylinder and accumulates in the gap between the plunger shaft and the inner wall of the injection cylinder. Met. However, the leakage resin corresponding to the gap between the plunger head and the cylinder inner wall cannot be scraped off, and the remaining leakage resin is solidified by friction between the plunger head and the cylinder and is fixed to the inner wall of the cylinder. The resin fixed at the time of the next injection molding is naturally peeled off little by little, and part of it is mixed into the molten resin in the injection chamber, and finally into the molded product.

  The present invention has been made in view of the above problems of the conventional plunger type injection molding machine, and is an injection of a plunger type injection molding machine that forcibly scrapes off the resin fixed in the gap between the plunger head and the inner wall of the cylinder. An object is to provide an apparatus.

The present invention made to solve the problems includes an injection cylinder, a plunger head that is fitted in the injection cylinder so as to be capable of moving forward and backward in the axial direction, and extends from the plunger head to one axial direction of the plunger head. A plunger shaft, and an injection driving device for injecting the molten resin in the injection cylinder to the other axial side by the plunger head by moving the plunger shaft to the other axial side, and the plunger head includes: Chi lifting projection of hemispherical on the outer peripheral surface of one axial side to the inner wall and the sliding contact of the injection cylinder, the plunger head includes a rotating mechanism for rotating about the central axis of the plunger head, a plurality of the projections the When the protrusions formed in a spiral shape on the outer peripheral surface of the plunger head are grouped into one group, It is an injection device of the plunger-type injection molding machine, characterized in being formed at an interval.

  Since the plunger head has a projection that slides on the inner wall of the injection cylinder on the outer periphery on one side in the axial direction, the resin accumulated in the gap between the plunger head and the cylinder inner wall can be forcibly scraped off by the projection.

  Since the rotation mechanism for rotating the plunger head around the axis of the plunger head is provided, the plunger head not only advances and retreats but also rotates around the axis. As a result, the scraping efficiency of the resin by the protrusion is improved.

Since the protrusions are spirally connected, the resin accumulated in the gap between the plunger head and the cylinder inner wall is scraped off by the spiral protrusions, and the scraped resin can be discharged out of the cylinder through the groove between the spiral protrusions. it can.

The injection device of the above-described plunger-type injection molding machine may include a flange extending in the radial direction from the outer peripheral surface of the plunger shaft.

  Since the flange extending in the radial direction from the outer peripheral surface of the plunger shaft is provided, the resin scraped off by the protrusion is prevented from reaching the drive unit that drives the plunger through the plunger shaft. As a result, the resin is not caught in the drive unit, and malfunction of the drive unit can be prevented.

  Since the protrusion on one side in the axial direction of the plunger head has a protrusion that slides on the inner wall of the injection cylinder, the resin accumulated in the gap between the plunger head and the inner wall of the cylinder can be divided by the protrusion and forcibly scraped off.

  The best mode for carrying out the present invention will be described below with reference to the drawings. 1 is an overall view showing a plunger-type injection molding machine of the best mode for carrying out the present invention in a partial cross-section, FIG. 2 is a side view showing a main part of FIG. 1 in a partial cross-section, and FIG. FIG. 4 is a schematic cross-sectional view of a main part of FIG. 1, FIG. 4 is a schematic view showing a process of forming a protrusion on the plunger head, and FIG.

  As shown in FIG. 1, a plunger-type injection molding machine 1 of the best mode for carrying out the present invention includes a plasticizing device 2 and an injection device 3, and is provided in a plasticizing cylinder 20 of the plasticizing device 2. The formed plasticizing chamber 12 and the injection chamber 13 formed in the injection cylinder 20 of the injection device 3 are communicated with each other by the communication path 11. A check device 22 having a built-in hydraulic piston is connected to the rear end of the plasticizing cylinder 20, and a rotary drive device 23 such as a hydraulic motor is connected to the check device. The rear end of the plasticizing screw 21 provided in the plasticizing chamber 12 is coupled to the hydraulic piston of the check device 22, and the hydraulic piston is further coupled to the hydraulic motor of the rotational drive device 23, so that the plasticizing screw 21 is plasticized. The cylinder 20 is rotatable and can be advanced and retracted.

  A frame 41 of the injection driving device 40 is connected to the rear end portion of the injection cylinder 30. An injection hydraulic cylinder 34 is fixed in the frame 41, and an injection piston 35 is attached therein so as to be able to advance and retreat. An injection plunger 31 provided with a plunger head 31a inserted into the injection cylinder 30 and a plunger shaft 31b extending from the rear end of the plunger head 31a is fixed to the tip of the connecting rod at the rear end. The connecting rod 33 is fixed to the tip of the ram 35a of the injection piston 35, and the injection plunger 31 rotates and moves forward and backward in the injection cylinder 30.

  The resin put in from the hopper 24 is plasticized by the heat of the band heater of the plasticizing cylinder 20 (not shown) and the rotation of the plasticizing screw 21 and sent forward. At this time, if the hydraulic pressure of the hydraulic oil of the check device 22 is released to make the plasticizing screw 21 retractable, the plasticizing screw 21 is retracted by the reaction force of the molten resin to be sent and the communication passage 11 is released. The The molten resin that has passed through the communication path 11 is sent to the injection cylinder 30 to retract the injection plunger 31. The position of the retreating injection plunger 31 is measured by a position detector 37 such as a linear encoder, and the molten resin is measured. When the metering is completed, the injection is performed by moving the injection piston 35 of the injection hydraulic cylinder 34 forward. At this time, the plasticizing screw 21 is advanced by the thrust of the check device 22 to close the communication path 11, that is, check.

  As shown in FIGS. 2 and 3, the diameter of the plunger head 31a is larger than the diameter of the plunger shaft 31b, and the difference in diameter between the inner diameter of the inner wall 30a of the injection cylinder 30 and the outer diameter of the plunger head 31a is about 0.1 mm. A certain degree of clearance is secured.

  A wart-like projection 31c is provided on the outer periphery of the rear portion of the plunger head 31a. Therefore, the resin accumulated in the gap between the inner wall 30a of the injection cylinder 30 and the plunger head 31a can be divided and scraped off as the plunger 30 is advanced and retracted and rotated by the injection driving device 40 and the rotary motor 32.

  The protrusion 31c of the present embodiment is hemispherical, and a plurality of protrusions 31c are formed on the outer periphery of the rear end side of the plunger head 31a. The plurality of protrusions 31c are formed in a threaded manner on the outer peripheral surface of the plunger head 31a. That is, the plurality of protrusions 31c are formed in a spiral shape. Furthermore, when these spiral protrusions 31c are formed as one group, a plurality of groups are formed at intervals in the axial direction of the plunger head 31a. With this configuration, when the plunger head 31a is retracted, the plunger head 31a is rotated to discharge the resin to the rear portion of the injection cylinder 30 through the groove-like space between the spirally connected projections 31c. be able to.

  The scraped resin is discharged to the outside from the resin discharge port 51 of the frame 41. Near the rear end of the plunger shaft 31b, a flange 31d is provided to prevent the scraped resin from entering the sliding portion of the rotary motor 32.

  The shape of the protrusion 31c is preferably a hemispherical shape. In the case of a hemispherical projection, the projection 31c is in sliding contact with the inner wall 30a of the injection cylinder 30 at a point, so that the friction coefficient can be reduced and galling is unlikely to occur. Therefore, as shown in FIG. The gap between the inner wall 30a can be made as close to zero as possible. As a result, the resin scraping efficiency is improved. The range in which the protrusion 31c is provided is preferably 5 to 20% of the total length of the plunger head 31a from the rear end 31d of the plunger head 31a when the protrusion 31c is in sliding contact with the inner wall 30a of the injection cylinder 30 as shown in FIG. 3A. . If it is provided in a wider range, resistance due to friction between the protrusion 31c and the injection cylinder inner wall 30a increases, and the load on the injection drive device 40 increases. Conversely, if it is provided in a narrower range, the resin scraping efficiency is lowered. As shown in FIG. 3B, when the height of the tip of the protrusion 31c is equal to the outer periphery of the plunger head 31a, it is better to set the protrusion provision range to 50% or more in order to increase the resin scraping efficiency.

  For example, as shown in FIG. 4, the protrusion 31c may be provided by embedding a sphere in the outer periphery of the half plunger head 31a. The protrusions wear with long-term operation, but can be replaced with new balls to maintain the scraping performance. The material of the sphere is preferably the same material as the plunger head, for example, SUS. By making the expansion coefficient the same, the fixation of the sphere to the plunger head can be ensured.

  The protrusion may be a thread-like protrusion 31c 'as shown in FIG. As the plunger 30 advances and retreats and rotates, the resin accumulated on the inner wall 30a of the injection cylinder 30 is divided and scraped off and easily discharged.

  The present invention is very likely to be widely used for manufacturing plastic parts in the automobile industry, the electric / electronic industry, and the like.

It is a whole view shown with a partial cross section of a plunger type injection molding machine provided with the injection apparatus of this invention. It is a side view which shows the principal part of the injection device of this invention in a partial cross section. It is principal part sectional drawing of the injection apparatus of this invention. It is a schematic diagram which shows the process of forming protrusion in a plunger head. It is a side view of the plunger which shows the deformation | transformation aspect of protrusion.

Explanation of symbols

1 ·············· Plunger type injection molding machine 3 ·············································· Injection chamber 30 31 ··········· Injection plunger 31a ··· Plunger head 31b ··· Plunger shaft 31c, 31c '· · · Projection 31d · · · 鍔 32 ··· Rotation Mechanism (rotary motor)
40 ・ ・ ・ ・ ・ ・ Injection drive

Claims (3)

An injection cylinder, a plunger head inserted into the injection cylinder so as to be capable of moving back and forth in the axial direction, a plunger shaft extending from the plunger head to one axial direction of the plunger head, and the plunger shaft on the other axial side An injection driving device for injecting the molten resin in the injection cylinder to the other side in the axial direction by the plunger head by moving to
Said plunger head, Chi lifting the projection of hemispherical inner wall in sliding contact with the injection cylinder on the outer circumferential surface of the one axial side,
A rotation mechanism for rotating the plunger head around the axis of the plunger head;
A plurality of the protrusions are formed in a spiral shape on the outer peripheral surface of the plunger head, and the protrusions connected in a spiral shape are formed as a group, and are formed at intervals in the plunger axis direction. An injection device for a plunger type injection molding machine. The injection device for a plunger-type injection molding machine according to claim 1 , further comprising a flange extending in a radial direction from an outer peripheral surface of the plunger shaft. An injection cylinder, a plunger head inserted into the injection cylinder so as to be capable of moving back and forth in the axial direction, a plunger shaft extending from the plunger head to one axial direction of the plunger head, and the plunger shaft on the other axial side An injection driving device for injecting the molten resin in the injection cylinder to the other side in the axial direction by the plunger head by moving to
The plunger head has a protrusion that slides in contact with the inner wall of the injection cylinder on an outer peripheral surface on one axial side of the plunger head, and includes a flange that extends in a radial direction from the outer peripheral surface of the plunger shaft. Injection machine for molding machines.

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