JP2006142520A - Preplasticizing type injection device and discharge method of leaking resin therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discharge the molten resin getting over a plunger head 102A and leaking to a plunger stem part 102B side. <P>SOLUTION: A rotary drive part 108 is provided to a plunger driving part 105 along with an advance and retreat drive part 116 and a spiral groove 104 is further provided to the plunger stem part 102B while the molten resin, which gets over the plunger head 102A leaking to the plunger stem part 102B side, is discharged by the screw feed action by the spiral groove 104 caused by the rotation of an injection plunger 102. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pre-plastic injection device, and more particularly to discharge of molten resin that has passed over the plunger head of an injection plunger and leaked to the rear plunger shaft side.

As described in JP-A No. 2004-167740, the pre-plastic injection device is configured with a plasticizing part and an injection part separately, and sends the molten resin plasticized by the plasticizing part to the injection part. When the molten resin is stored in the injection part, that is, when the measurement of the molten resin is completed, the injection plunger is advanced to inject the molten resin into the mold.
JP 2004-167740 A

  By the way, since the above-mentioned injection plunger slides in the injection cylinder, it is necessary to provide a clearance between the outer peripheral surface of the plunger head and the inner surface of the injection cylinder. Therefore, the molten resin gets over the plunger head and leaks little by little to the plunger shaft part located behind the plunger head. The leaked molten resin is accumulated by increasing the amount by repeating injection and metering.

  When the molten resin accumulated on the plunger shaft side is solidified and carbonized, there is a problem that the sliding resistance of the injection plunger is increased and pressure loss is caused in the injection process.

  In order to solve the above-described problems, the present invention provides a pre-plastic injection device capable of discharging molten resin that has passed over the plunger head and leaked to the plunger shaft side, and a method for discharging the leaked resin in this device. It is an object.

In order to achieve the above object, the present invention includes a screw that rotates in a heating cylinder, a plasticizing portion that plasticizes a resin material, an injection plunger that advances and retreats in the injection cylinder, and a backflow prevention valve. Injection that is connected to the plasticizing portion and stores molten resin sent from the plasticizing portion in an injection chamber formed in front of the injection plunger, and injects the molten resin into the mold by the advancement of the injection plunger. A pre-plastic injection device comprising:
A drive unit that rotates the injection plunger, and a spiral groove formed in a plunger shaft portion that is located behind the plunger head of the injection plunger, and has leaked to the plunger shaft side over the plunger head The molten resin can be discharged through the spiral groove by the rotation of the injection plunger.

  Further, the present invention for achieving the above object is a method for discharging a leaked resin in the above-described pre-plastic injection device, wherein the injection plunger is set for a predetermined time before injecting the molten resin in the injection chamber. And the leaked molten resin is discharged.

  In addition, in the method for discharging the leaked resin in the above-described pre-plastic injection device, after injecting the molten resin in the injection chamber, the injection plunger is rotated for a predetermined time, and the leaked molten resin is discharged. In addition, the injection plunger may be rotated at least during a measuring step of storing the molten resin in the injection chamber, and the leaked molten resin may be discharged.

  Since the present invention is configured as described above, the molten resin that has passed over the plunger head and leaked to the plunger shaft side can be more reliably discharged, and the injected plunger slides due to solidification and carbonization of the leaked molten resin. The effect that the increase in resistance can be suppressed and the generation of pressure loss in the injection process can be suppressed can be obtained.

  An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 10 is a plasticizing part and 100 is an injection part. The plasticizing unit 10 includes a heating cylinder 11 having a heater (not shown) on the outer periphery, and a screw 12 provided in the heating cylinder 11 so as to be rotatable only. The screw 12 is disposed at the rear end of the heating cylinder 11. The screw drive unit 13 is rotated. Near the rear end of the heating cylinder 11, a hopper 14 for supplying a resin material is provided. The plasticizing unit 10 plasticizes the resin material supplied from the hopper 14 and discharges it as a molten resin from the resin passage 15 at the tip of the heating cylinder 11.

  The injection unit 100 includes an injection cylinder 101 having a nozzle 30 at the tip, and an injection plunger 102 provided in the injection cylinder 101 so as to be able to advance and retract and rotate. The resin passage 15 is connected to a position near the tip of the injection cylinder 101 via the backflow prevention valve 20, and the molten resin is sent to the injection chamber 103 formed by the inner surface of the injection cylinder 101 and the tip of the injection plunger 102. .

  The injection plunger 102 has a plunger head 102A and a plunger shaft portion 102B. As described above, the plunger head 102A forms a clearance between its outer peripheral surface and the inner surface of the injection cylinder 101, and the injection plunger 102 injects. The cylinder 101 is configured to be slidable.

  The plunger shaft portion 102B is not simply a shaft shape thinner than the plunger head 102A like the plunger shaft portion of the injection plunger in the conventional pre-plastic injection device, but the outer diameter is made equal to the outer diameter of the plunger head 102A, A spiral groove 104 is provided.

  The rear end of the injection plunger 102 is rotatably attached to an intermediate plate 106 constituting the plunger drive unit 105 via a bearing 107, and is rotationally driven by an electric servo motor or a stepping motor attached to the intermediate plate 106. It is connected to the unit 108 and is rotated.

  The intermediate plate 106 is slidably attached to a plurality of guide bars 111 provided in parallel with the injection plunger 102 between a front plate 109 and a rear plate 110 provided integrally with the injection cylinder 101. Yes.

  Two ball screws 112 extending backward (to the right in FIG. 1) parallel to the guide bar 111 are attached and fixed to the intermediate plate 106, and the rear plate 110 is screwed to the ball screws 112 so as to be reversibly rotatable. A ball nut 113 is attached by a bearing 114 so as to be rotatable only. A timing pulley 115 is provided at the right end of the ball nut 113 in FIG. 1, and the ball nut 113 is connected to the ball nut 113 through the timing pulley 117 and the timing belt 118 by an advance / retreat drive unit 116 including an electric servo motor attached to the rear plate 110. A reverse rotation is applied to advance and retract the intermediate plate 106 to advance and retract the injection plunger 102.

  The screw drive unit 13 of the plasticizing unit 10 and the advance / retreat drive unit 116 of the injection unit 100 are controlled by the control unit 40 to rotate the screw 12 and move the injection plunger 102 in the same manner as in the conventional pre-plastic injection device. Advance and retreat. The operation of the rotation drive unit 108 is similarly controlled by the control unit 40 to rotate the injection plunger 102 at a predetermined speed and timing. In addition, although illustration is abbreviate | omitted, the control part 40 is comprised so that the opening and closing of the backflow prevention valve 20 may also be controlled.

  Next, the operation of this apparatus will be described. The screw drive unit 13 of the plasticizing unit 10 is controlled in operation by the control unit 40, rotates the screw 12 at a predetermined speed, takes the resin material from the hopper 14 into the heating cylinder 11, and plasticizes the resin material. The molten resin is discharged from the resin passage 15 at the tip of the heating cylinder 11. The molten resin discharged into the resin passage 15 is sent to the injection chamber 103 through the backflow prevention valve 20 placed in an open state.

  At this time, the rotation drive unit 108 of the injection unit 100 is in a stopped state, and only the advance / retreat drive unit 116 is in an operating state. The molten resin sent to the injection chamber 103 presses the injection plunger 102 backward (rightward in FIG. 1) by the pressure. The force that pushes the injection plunger 102 backward acts on the advancing / retreating drive unit 116 via the intermediate plate 106, the ball screw 112, the ball nut 113, the timing pulley 115, the timing belt 118, and the timing pulley 117. The advancing / retreating drive unit 116 is controlled in rotational torque by the control unit 40, applies a predetermined back pressure to the injection plunger 102, rotates the ball nut 113 so that the pressure in the injection chamber 103 becomes a predetermined value, and rotates the ball screw 112. And the injection plunger 102 is retracted together with the intermediate plate 106.

  Thus, when the injection plunger 102 is retracted by a predetermined amount and a predetermined amount of molten resin is stored in the injection chamber 103 and the so-called metering process is completed, the backflow prevention valve 20 is closed by the control unit 40 and the process proceeds to the injection process.

  As described above, since there is a clearance between the inner surface of the injection cylinder 101 and the outer peripheral surface of the plunger head 102A of the injection plunger 102, the molten resin in the injection chamber 103 gets over the plunger head 102A during the metering step. As indicated by the arrow A, leakage occurs slightly toward the rear plunger shaft portion 102B.

  Therefore, in the present invention, before moving to the injection process, the rotation driving unit 108 is operated by the control unit 40 for a predetermined time, and the injection plunger 102 is rotated at a predetermined speed. By the rotation of the injection plunger 102, the spiral groove 104 provided in the plunger shaft portion 102B is rotated, and the molten resin leaked to the plunger shaft portion 102B side by the so-called screw feeding action is moved away from the plunger head 102A. Move to.

  After the molten resin leaked to the plunger shaft 102B side is moved rearward, the injection process is started. That is, the controller 40 rotates the advance / retreat drive unit 116 at a predetermined speed, rotates the ball nut 113 via the timing pulley 117, the timing belt 118, and the timing pulley 115, and advances the ball screw 112 (leftward in FIG. 1). The injection plunger 102 is advanced through the intermediate plate 106, and the molten resin in the injection chamber 103 is injected and filled from the nozzle 30 into a mold (not shown).

  When this injection process is completed, the backflow prevention valve 20 is opened again, and the molten resin is supplied again from the plasticizing section 10 into the injection chamber 103. Thereafter, the above operation is repeated.

  The leakage resin discharging step of rotating the injection plunger 102 and moving the molten resin leaked to the plunger shaft portion 102B rearward is performed for each molding cycle or at a rate of once every several molding cycles. You may make it perform. In any case, since the discharging process of the leaked resin is repeatedly performed, the leaked resin is sequentially moved rearward and finally discharged out of the injection cylinder 101. Therefore, the leaked resin does not stay on the plunger shaft 102B side for a long time to solidify and carbonize, and the increase in sliding resistance of the injection plunger and the accompanying pressure loss in the injection process can be suppressed.

  The leakage of the molten resin to the plunger shaft portion 102B occurs not only in the metering step described above but also in the injection step, but this is moved backward by the rotation of the injection plunger 102 in the next cycle and discharged.

  In the above-described embodiment, the example in which the leakage resin discharging step is performed before the injection step is shown, but the present invention is not limited to this, and the leakage resin discharging step is performed after the injection step or weighing. You may make it carry out in all or one part in a process.

  The present invention can be applied to all pre-plastic injection devices.

BRIEF DESCRIPTION OF THE DRAWINGS The principal part schematic diagram which shows one Embodiment of the pre-plastic injection apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plasticization part 11 Heating cylinder 12 Screw 13 Screw drive part 14 Hopper 15 Resin passage 20 Backflow prevention valve 30 Nozzle 40 Control part 100 Injection part 101 Injection cylinder 102 Injection plunger 102A Plunger head 102B Plunger shaft part 103 Injection chamber 104 Helical shape Groove 105 Plunger drive unit 106 Intermediate plate 107, 114 Bearing 108 Rotation drive unit 109 Front plate 110 Rear plate 111 Guide bar 112 Ball screw 113 Ball nut 115, 117 Timing pulley 116 Advance / retreat drive unit 118 Timing belt

Claims (4)

A plasticizing part having a screw rotating in a heating cylinder and plasticizing a resin raw material;
It has an injection plunger that advances and retreats in the injection cylinder and is connected to the plasticizing part via a backflow prevention valve, and stores the molten resin sent from the plasticizing part in an injection chamber formed in front of the injection plunger, An injection part for injecting this molten resin into the mold by the advance of the injection plunger;
In a pre-plastic injection device equipped with
A drive unit that rotates the injection plunger, and a spiral groove formed in a plunger shaft portion that is located behind the plunger head of the injection plunger, and has leaked to the plunger shaft side over the plunger head A pre-plastic injection device characterized in that molten resin can be discharged through the spiral groove by rotation of the injection plunger.   The method for discharging leaked resin in the pre-plastic injection device according to claim 1, wherein the injection plunger is rotated for a predetermined time before injecting the molten resin in the injection chamber, and the leaked molten material is discharged. A method for discharging a leaked resin in a pre-plastic injection device, wherein the resin is discharged.   A method for discharging a leaked resin in the pre-plastic injection device according to claim 1, wherein after the molten resin in the injection chamber is injected, the injection plunger is rotated for a predetermined time, and the leaked molten resin is injected. A method for discharging a leaked resin in a pre-plastic injection device, wherein the resin is discharged. The method for discharging leaked resin in the pre-plastic injection device according to claim 1, wherein the injection plunger is rotated at least during a measuring step of storing the molten resin in the injection chamber, and the leaked molten resin is discharged. A method for discharging a leaked resin in a pre-plastic injection device, characterized in that the resin is discharged.

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