JP2000202879A - Screw type injection molding machine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent the backflow of a molten resin during injection and pressure-holding, and to reduce the molten resin stagnation portion. SOLUTION: A torpedo 7 arranged in a cylinder head 4 is advanced and retracted in an axial direction by a torpedo linear driving means 16. The torpedo 7 includes an axially penetrating reservoir 6 having a large-diameter portion 6a and a small-diameter portion 6b and having a pressure receiving portion 7b due to a step in a communicating portion between the large-diameter portion 6a and the large-diameter portion 6a. A screw head 3 having substantially the same diameter is slidably fitted in the circumferential direction and the axial direction. At the time of injection and pressure holding, in addition to the acting force of the torpedo linear drive means 16, the pressure receiving portion 7 b of the reservoir 6 receives the pressure of the molten resin to cause the sealing portion 7 c of the torpedo 7 to move the conical inner wall surface of the cylinder head 4. A pressing force for pressing against 4a is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw type injection molding apparatus capable of realizing ultra-precision molding without variation in the amount of resin to be injected and filled.

[0002]

2. Description of the Related Art An example of a conventional screw type injection molding apparatus capable of precision molding will be described.

As shown in FIG. 5, a heating cylinder 101 having a cylinder head 104 removably fixed to a tip thereof by a plurality of fixing means such as a plurality of bolts 117, and a rotatable and axially reciprocating inside the heating cylinder 101. A screw 102 is provided, and an injection nozzle 105 is provided at the tip of a cylinder head 104. A band heater 1 is provided on outer wall surfaces of the heating cylinder 101 and the cylinder head 104.
A heating means such as 18 is provided.

[0004] A torpedo 107 is slidably disposed in the cylindrical portion 104b of the cylinder head 104 in the axial direction.
4 for a torpedo consisting of a lever 110 pivotally attached to a support member 109 protruding from the base member 4 via a pivot 109a, and a linear motion actuator 111 having a rod 115 for rotating the lever 110 in directions indicated by arrows and counter-arrows. It is advanced and retracted in the axial direction by the linear driving means 116.

[0005] The torpedo 107 has a through hole 107b penetrating in the axial direction in which a screw head 103 having the same diameter as the screw 102 is slidably inserted in the circumferential and axial directions.
A sealing portion 107c protruding from a portion surrounding the opening edge of the through hole 107b in the conical tip surface, and a plurality of axially extending outer walls formed on the outer wall surface at intervals in the circumferential direction It has a groove 108a and a plurality of rear end grooves 108b corresponding to the outer wall grooves 108a formed on the conical rear end surface.

In this conventional screw-type injection molding apparatus, the torpedo 107 is retracted during the plasticizing step, and the conical inner wall surface 10 of the seal portion 107c and the cylinder head 104 are formed.
Gap S ₀ occurs 4a and are spaced apart, end groove 108b and the outer wall groove 108a molten resin from the screw groove 102a side
Flow to the reservoir 106 for metering. Then, at the end of the plasticization, the torpedo 107 is advanced, and the seal portion 107c is brought into contact with the inner wall surface 104a, thereby preventing the molten resin from flowing backward during injection and pressure holding.

[0007]

In the above prior art,
The seal portion 107c of the torpedo 107 is moved by the action of the torpedo
By pressing against the conical inner wall surface 104a of No. 4
This prevents the molten resin in the reservoir 106 from flowing back to the outer wall groove 108a. That is, the force for pressing the seal portion 107c of the torpedo 107 against the inner wall surface 104a of the cylinder head is given only by the torpedo linear drive means 116. For this reason, when the pressing force is low, the torpedo 107 retreats due to the pressure of the molten resin in the reservoir 106 during injection and pressure holding, and the seal portion 107c of the torpedo 107 and the inner wall surface 1 of the cylinder head 1
There is a possibility that a molten resin flows back to the outer wall groove 108a of the torpedo 107 through the gap and the amount of molten resin injected into the mold cavity via the injection nozzle 105 varies.

The amount of forward and backward movement of the screw 102 is set to be large or small according to molding conditions. However, the screw 102 such that the screw groove 102a does not move rearward of the rear end groove 108b of the through hole 107b of the torpedo 107.
When molding is performed with the moving amount of the screw groove 102a,
Always moves back and forth in the through-hole 107b. In this case, the molten resin in the screw groove 102a can not move into the reservoir 106 through the outer wall groove 108a and the gap S ₀ through end groove 108b. That is, the molten resin in the screw groove 102a is not discharged during operation. Then, the molten resin in the screw groove 102a thermally decomposes and degrades, and causes defects such as discoloration and burning of the resin. As a result, there is a problem that the quality and quality of the molded product are varied and defective.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to reliably prevent a backflow of a molten resin at the time of injection and pressure-holding, and at the same time, to prevent the molten resin from being retained. An object is to realize a small screw type injection molding apparatus.

[0010]

In order to achieve the above-mentioned object, a screw type injection molding apparatus according to the present invention comprises a heating cylinder having a cylinder head detachably fixed to a tip end thereof, and a cylinder head and the heating cylinder. Heating means for heating each, a screw disposed rotatably and axially retractable in the heating cylinder, and a bottom of a foremost part of a screw groove integrally provided at a tip end of the screw. A screw head having substantially the same outer diameter as the diameter, a torpedo having a conical tip end disposed slidably in the axial direction within the cylinder head, and a torpedo straight line for moving the torpedo forward and backward in the axial direction A screw-type injection molding device provided with a driving means, wherein the torpedo is fitted with the screw head slidably in a circumferential direction and an axial direction. An axially penetrating reservoir comprising a large-diameter portion on the end side and a small-diameter portion on the distal end side and having a pressure-receiving portion due to a step in the communicating portion between them, and an opening peripheral edge of the small-diameter portion on the conical distal end surface are taken. A seal portion provided at a surrounding portion, and a plurality of axially extending outer wall grooves formed on an outer wall surface at intervals in a circumferential direction, and retracting the torpedo to form a conical shape of the cylinder head. When the seal portion is separated from the inner wall surface, the reservoir and the screw groove at the distal end of the screw are configured to communicate with each other, and further, the torpedo is driven forward by the torpedo linear drive means. In addition to the pressing force for pressing the seal portion against the conical inner wall surface of the cylinder head, the pressure generated by the molten resin applied to the pressure receiving portion during injection and pressure holding is increased. Is characterized in that said are pressing force on conical inner wall surface of the cylinder head is pressed against the sealing portion is configured such that.

Further, it is assumed that the outer wall groove is formed in a spiral shape.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings.

As shown in FIGS. 1 to 3, the screw type injection molding apparatus according to the present embodiment comprises a heating cylinder 1 having a cylinder head 4 which is removably fixed to the tip by a plurality of fixing means such as a plurality of bolts 17. A band heater 18 provided on the outer wall surfaces of the cylinder head 4 and the heating cylinder 1 as heating means for heating the cylinder head 4 and the heating cylinder 1, respectively;
A screw 2 disposed rotatably and axially movable in a heating cylinder 1, an injection nozzle 5 disposed at a tip of a cylinder head 4, and a cylindrical portion 4b of the cylinder head 4.
A torpedo 7 is provided inside the slidably slidable in the axial direction, and a torpedo linear drive means 16 for moving the torpedo 7 in the axial direction is provided.

The torpedo 7 comprises a large-diameter portion 6a on the rear end side and a small-diameter portion 6b on the distal end side into which the screw head 3 is slidably fitted in the circumferential direction and the axial direction. An axially penetrating reservoir 6 having a pressure receiving portion 7b, and a seal portion 7c provided at a portion surrounding the opening edge of the small diameter portion 6b on the conical tip surface, and an outer peripheral side surrounding the seal portion 7c Is provided with a flow path forming surface on which a gap is generated when the seal portion 7c is brought into contact with the conical inner wall surface 4a of the cylinder head 4. The outer wall surface of the torpedo 7 has a plurality of outer wall grooves 8a extending in a plurality of axial directions at intervals in the circumferential direction.
The front end side of each outer wall groove 8a is open to the flow path forming surface 7a, and the rear end side of the screw 2 is formed by a rear end groove 8b provided on the conical rear end surface of the torpedo 7. It communicates with the screw groove 2a at the tip. However, while being open to the flow path forming surface 7a, the rear end side is communicated with the screw groove 2a at the front end of the screw 2 by the rear end groove 8b provided on the conical rear end surface of the torpedo 7. If this is satisfied, the outer wall groove formed on the outer wall surface of the torpedo 7 is not limited to a linear shape, but may be a spiral shape or any other shape.

Further, an engagement hole 8c into which one end side of a lever 10 of the torpedo linear drive means 16 described later is formed in an appropriate portion of the outer wall surface of the torpedo 7 other than the outer wall groove 8a.

Here, an example of the torpedo linear drive means 16 will be described.

As shown in FIG. 1 and FIG.
A pivot 9 is attached to a support member 9 protruding from the cylinder head 4.
a one end of which is inserted into an engagement hole 8c of the torpedo 7,
The other end is connected to a rod 15 which is rotatably connected to a bracket 14 fixed to the outer wall of the heating cylinder 1 via a pin 13 so as to be rotatable through a linear motion actuator 11.
2 are connected. For this reason, when the linear motion actuator 11 is operated in the direction in which the rod 15 is protruded, the lever 10 rotates in the direction of the arrow shown in FIG.
When the rod 15 is operated in the direction in which the rod 15 is retracted, the lever 10 rotates in the direction of the arrow shown in FIG. 2 and the torpedo 7 moves forward.

Since the moving distance of the torpedo 7 by the forward or backward movement is about 0.3 mm to 2 mm, the size of the linear actuator 11 may be small.

Next, the operation will be described.

In the plasticizing step, as shown in FIG. 1, the linear actuator 11 is operated in the direction in which the rod 15 is protruded, and the lever 10 is rotated in the direction of the arrow, so that the torpedo 7 is retracted. Is separated from the conical inner wall surface 4a of the cylinder head 4 so that the screw groove 2a and the reservoir 6 communicate with each other via the rear end groove 8b, the outer wall groove 8a, and the gap S. Then, the screw 2 is rotated.

Next, when the resin is charged from a hopper (not shown), the charged resin is kneaded and melted while being transferred to the front by the rotating screw 2, and is sequentially formed in the rear end groove 8.
b, the screw 2 is stored in the reservoir 6 through the outer wall groove 8a and the gap S, and retreats while rotating by the resin pressure with the increase of the molten resin stored in the reservoir 6,
When the molten resin stored in the reservoir 6 reaches a predetermined amount, the screw 2 is stopped.

At this time, at the same time as the screw 2 stops, the linear actuator 11 is operated in the direction of pulling the rod 15 and the lever 10 is rotated in the direction of the arrow to advance the torpedo 7, and the torpedo 7 The seal portion 7c is brought into contact with the conical inner wall surface 4a of the cylinder head 4. That is, the resin flow path is closed. As a result, at the same time as the end of the plasticizing step, the flow path of the molten resin stored in the reservoir 6 toward the outer wall groove 8a and the screw groove 2a is closed. In this case, since the molten resin does not flow toward the reservoir 6 from the screw groove 2a until the injection / pressure-holding step is started, the resin density in the reservoir 6 immediately before the injection / pressure-holding step is started. Stability is maintained.

At the time of injection and pressure holding, as shown in FIG. 2, the screw 2 is moved forward with the sealing portion 7c at the tip end surface of the torpedo 7 in contact with the conical inner wall surface 4a of the cylinder head 4. Then, the molten resin stored in the reservoir 6 is injected and filled into the cavity of a mold (not shown) which has been clamped through the injection nozzle 5.

In this case, since the pressure of the molten resin in the reservoir 6 is received by the pressure receiving portion 7b and a force in the direction of moving the torpedo 7 forward is applied, the sealing portion 7c of the torpedo 7 is fixed to the conical inner wall surface of the cylinder head 4. The pressing force applied to 4a is obtained by adding the pressing force due to the pressure of the molten resin received by the pressure receiving portion 7b to the acting force of the torpedo linear drive means 16, and the backflow of the molten resin from the reservoir 6 side to the screw 2 side is ensured. Is prevented.

Next, a description will be given of an operation in the case where plasticization is performed so that the relative position between the rear end groove 8b of the torpedo 7 and the screw groove 2a at the front end of the screw 2 becomes constant in the plasticizing step.

FIG. 4A shows a state at the time of completion of the injection / pressure-holding step.
First, by rotating the lever 10 in the direction of the arrow as shown in FIG. 4B to retract the torpedo 7, the seal portion 7c of the torpedo 7 is separated from the conical inner wall surface 4a of the cylinder head 4. The resin flow path is opened, and the screw 2 is retracted to a predetermined position.

After the above-described process, the process proceeds to the plasticizing process. As shown in FIG. 4C, the screw 2 rotates in the axial direction while stopped at the predetermined position, and the rotating screw is rotated. The melted resin kneaded and melted by the step 2 is sequentially filled with the rear end groove 8b, the outer wall groove 8a and the gap S of the torpedo 7.
And stored in the reservoir 6. When the amount of the molten resin stored in the reservoir 6 reaches a predetermined amount, the torpedo 7 is advanced by rotating the lever 10 in the direction of the arrow as shown in FIG. After contacting the conical inner wall surface 4a of the cylinder head 4,
Stop screw 2 rotation.

Next, in the state shown in FIG. 4D, the screw 2 is advanced, so that the reservoir 6 is inserted into the cavity of a mold clamped (not shown) through the injection nozzle 5.
The molten resin stored in the container is injected and filled.

In this case, since the pressure of the molten resin in the reservoir 6 is received by the pressure receiving portion 7b and a force in the direction of moving the torpedo 7 forward is applied, the sealing portion 7c of the torpedo 7 is fixed to the conical inner wall surface of the cylinder head 4. The pressing force applied to 4a is obtained by adding the pressing force due to the pressure of the molten resin received by the pressure receiving portion 7b to the acting force of the torpedo linear drive means 16, and the backflow of the molten resin from the reservoir 6 side to the screw 2 side is ensured. Is prevented.

[0030]

Since the present invention is configured as described above, the following effects can be obtained.

[0031] The backflow of the molten resin from the reservoir to the screw groove during the injection and pressure-holding step can be reliably prevented, and the staying portion of the molten resin is reduced.

In the plasticizing step, the molten resin flows as a thin layer into the reservoir only through the outer wall groove formed on the outer wall surface of the torpedo, so that the state of the molten resin passing through the outer wall groove is precisely controlled. Thus, the state of the molten resin stored in the reservoir becomes uniform.

Further, from the time when the plasticizing step is completed,
Since the molten resin does not flow from the screw groove toward the reservoir until the injection / holding step is started, the resin density in the reservoir immediately before the start of the injection / holding step is stabilized.

As a result, the quality of the molded product is stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of a main part during a plasticizing step, showing a screw-type injection molding apparatus according to one embodiment.

FIG. 2 is a schematic partial cross-sectional view of a main part of the screw injection molding apparatus shown in FIG. 1 during an injection / holding process.

FIG. 3 is a plan view showing an example of a torpedo in a screw-type injection molding apparatus according to the present invention.

FIG. 4 shows a screw type injection molding apparatus shown in FIG.
It is explanatory drawing in the case of performing a plasticization process, without changing the relative position of a screw groove and the back end groove of a torpedo.

FIG. 5 shows an example of a conventional screw injection molding apparatus,
FIG. 3 is a schematic partial cross-sectional view of a main part during a plasticizing step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Screw 2a Screw groove 3 Screw head 4 Cylinder head 4a Conical inner wall surface 4b Cylindrical part 4c Bolt hole 5 Injection nozzle 6 Reservoir 6a Large diameter part 6b Small diameter part 7 Torpedo 7a Flow path forming surface 7b Pressure receiving part 7c Seal portion 8a Outer wall groove 8b Rear end groove 8c Engagement hole 9 Support member 9a Axis 10 Lever 11 Linear actuator 12 Pin 15 Rod 16 Linear drive means for torpedo 17 Bolt 18 Band heater

Claims (2)

[Claims] 1. A heating cylinder (1) having a cylinder head (4) removably fixed to a distal end portion, heating means (18) for heating the cylinder head and the heating cylinder, respectively, and the heating cylinder. A screw (2) disposed rotatably and axially retractable in the inside,
A screw head (3) having an outer diameter substantially the same as the outer diameter of the bottom surface of the foremost part of the screw groove (2a) integrally provided at the tip end of the screw; and a slidable axially inside the cylinder head. A screw-type injection molding apparatus provided with a torpedo (7) having a conical tip surface and a torpedo linear drive means (16) for moving the torpedo forward and backward in the axial direction, wherein the torpedo comprises: Large diameter portion (6a) on the rear end side where the screw head is slidably fitted in the circumferential direction and the axial direction.
An axially penetrating reservoir (6) having a pressure-receiving portion (7b) formed by a step in a communicating portion between the small-diameter portion (6b) on the distal end side and an opening of the small-diameter portion on the conical distal end surface; A seal portion (7c) provided at a portion surrounding the peripheral edge; and a plurality of axially extending outer wall grooves (8) formed on the outer wall surface at intervals in the circumferential direction.
a) wherein the reservoir is communicated with the screw groove at the tip of the screw when the seal portion is separated from the conical inner wall surface (4a) of the cylinder head by retracting the torpedo. In addition to the pressing force that pushes the seal portion against the conical inner wall surface of the cylinder head by advancing the torpedo by the torpedo linear drive means,
Screw-type injection molding characterized in that a pressing force for pressing the seal portion is applied to a conical inner wall surface of the cylinder head due to a molten resin pressure applied to the pressure receiving portion during injection and pressure holding. apparatus. 2. The screw-type injection molding apparatus according to claim 1, wherein the outer wall groove is formed in a spiral shape.