JP2000218664A - Screw type injection molding machine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reliably prevent backflow of a molten resin during injection and pressure-holding, and to add secondary materials such as fibers reliably and easily. 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 is a pressure receiving section 7
b comprising an axially penetrating reservoir 6 having
A screw head 3 having substantially the same diameter as the bottom surface of the screw groove 2a is slidably fitted in the large diameter portion 6a 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 7b receives the pressure of the molten resin and generates a pressing force for pressing the seal portion 7c of the torpedo 7 against the conical inner wall surface 4a. I do. While the molten resin flows through the outer wall groove 8a of the torpedo 7, the plunger 21
The auxiliary material such as fibers is formed by the through holes 4 of the cylinder head 4.
c.

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 including a lever 110 pivotally attached to a support member 109 protruding from the base member 4 via a pivot 109a, and a fluid pressure cylinder 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.
A gap S ₀ occurs 4a and are spaced apart, the reservoir 10 molten resin through the outer wall groove 108a from the screw groove 102a side
Flow measurement is performed to 6. Then, at the end of plasticization, the torpedo 107 is advanced, and the seal portion 107c is brought into contact with the conical 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, the pressure of the molten resin in the reservoir 106 during injection and pressure-holding causes the torpedo 10
7, the gap is formed between the seal portion 107c of the torpedo 107 and the inner wall surface 104a of the cylinder head, and the molten resin flows back into the outer wall groove 108a of the torpedo 107 through the gap to form a mold through the injection nozzle 105. The amount of the molten resin injected into the cavity may vary.

The amount of forward and backward movement of the screw 102 is set to be large or small according to the molding conditions, but the screw groove 102a at the tip end is formed in the through hole 107b of the torpedo 107.
When molding is performed with the amount of movement of the screw 102 so as not to move backward from the rear end groove 108b, 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 rear end groove 108b, an outer wall groove 108a and the gap S _0. That is, the molten resin in the screw groove 102a is not discharged during operation. Then, the screw groove 102
The molten resin (a) thermally decomposes and degrades, causing 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 the molten resin from flowing backward during injection and pressure-holding, and to prevent the molten resin from being retained. It is an object of the present invention to realize a screw-type injection molding apparatus that can add and knead auxiliary materials such as pulp fiber, glass fiber, various powders, wood powder, and the like to a molten resin reliably and easily. Is what you do.

[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 surface outer diameter of a screw groove integrally provided at a tip end of the screw. A screw head having the same outer diameter, a torpedo having a conical tip end disposed slidably in the axial direction within the cylinder head, and a torpedo linear drive means for moving the torpedo forward and backward in the axial direction. A screw-type injection molding apparatus, wherein the torpedo is a rear end side on which the screw head is slidably fitted in a circumferential direction and an axial direction. An axially penetrating reservoir comprising a diameter portion and a small diameter portion on the distal end side and having a pressure receiving portion due to a step in a communicating portion between the two, and a portion surrounding the opening edge of the small diameter portion on the conical tip surface. And a plurality of axially extending outer wall grooves formed on the outer wall surface at intervals in the circumferential direction, and the torpedo is retracted from the conical inner wall surface of the cylinder head. The reservoir is configured to communicate with the screw groove at the tip of the screw when the seal portion is separated, and the torpedo is driven forward by the torpedo linear drive means to advance the cylinder. In addition to the pressing force for pressing the seal portion against the conical inner wall surface of the head, the pressure is caused by the molten resin pressure applied to the pressure receiving portion during injection and pressure holding. A pressing force for pressing the seal portion against the conical inner wall surface of the cylinder head, and at least one through hole penetrating the cylinder head; a hopper communicating with the through hole; A sub-material supply device including a pushing member for supplying a sub-material from the hopper through the through hole to the outer wall groove of the torpedo is provided.

[0011]

In the plasticizing step, the molten resin flowing from the screw groove to the reservoir flows in a thin layer in each outer wall groove of the torpedo, and the molten resin flowing in this way is supplied from the hopper. Pulp fiber, glass fiber,
Sub-materials such as various powders, wood flour, etc. are press-fitted by the pushing members.

The molten resin passing through each outer wall groove flows in contact with the inner wall of the cylinder head. Therefore, by controlling the amount of heating of a heater or the like wound around the outer periphery of the cylinder head, the temperature condition of the molten resin can be controlled. Extremely precise control enables a uniform and stable molten state.

Further, when the molten resin flows through the outer wall groove having a narrow flow path cross-sectional area, a shear stress due to a velocity gradient between the molten resin and the outer wall groove acts on the molten resin. The mixed material is subjected to the mixing and kneading action, so that the molten resin obtained by uniformly mixing and kneading the auxiliary material is transferred to the reservoir.

As a result, in the molten resin stored in the reservoir, auxiliary materials such as pulp fiber, glass fiber, various powders, wood flour and the like are surely added and mixed, and the molten state is stable.

At the time of injection and pressure holding, in addition to the external pressing force of the torpedo linear driving means, the pressure of the molten resin applied to the pressure receiving portion of the torpedo is used to enhance the backflow prevention function and the like by the torpedo, thereby clamping the mold. Variation in the amount of resin injected into the mold can be prevented.

[0016] By preventing backflow of the measured molten resin, temperature conditions and the like are precisely controlled, and by injecting and mixing a stable state of the molten resin by surely adding and mixing fibers and other auxiliary materials. High quality without defects such as sink marks
Moreover, it is possible to stably mold a molded article whose physical properties have been greatly improved by using auxiliary materials such as fibers.

[0017]

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 bolts 17 or the like. 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 in a heating cylinder 1 so as to be rotatable and movable in an axial direction, and a screw head having an outer diameter substantially the same as the outer diameter of the bottom surface of a screw groove 2a integrally provided at the tip of the screw 2. 3, an injection nozzle 5 disposed at the tip of the cylinder head 4, and a torpedo 7 disposed slidably in the axial direction within the cylindrical portion 4b of the cylinder head 4.
And a torpedo linear drive means 16 for moving the torpedo 7 in the axial direction.

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

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 via a pin 12 to a rod 15 which is extended and contracted by a fluid pressure cylinder 11 rotatably pivotally connected via a pin 13 to a bracket 14 fixed to the outer wall of the heating cylinder 1. For this reason, the fluid pressure cylinder 11
When the lever 10 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. 1 and the torpedo 7 is retracted. Conversely, when the rod 15 is operated in the retracting direction, the lever 10 is moved in the direction of the arrow shown in FIG. And the torpedo 7 moves forward.

Since the moving distance of the torpedo 7 by the advance or retreat is about 0.3 mm to 2 mm, the size of the fluid pressure cylinder 11 may be small.

The cylinder head 4 is provided with a through hole 4c in its cylindrical portion 4b. The through hole 4c penetrates through the cylindrical portion 4b of the cylinder head 4 radially outward from the outer wall groove 8a of the torpedo 7. To open on the outer wall surface of the cylinder head 4.

The pot 20 is brought into contact with the through hole 4c.
A plunger 21 serving as a pushing member is slidably fitted in the pot 20. The plunger 21 penetrates through the bottom wall of the hopper 22 and fits into the pot 20. The plunger 21 supplies auxiliary materials supplied from the hopper 22 such as pulp fibers, glass fibers, various powders, and wood powder from the drive cylinder 23. By the protruding plunger 21, the pot 20 passes through the through hole 4c,
The outer wall groove 8a is configured to be pressed into the flowing molten resin.

If necessary, a heating means such as a band heater may be provided outside the pot 20.

The auxiliary material supplied by the plunger 21 is introduced into the flow of the molten resin in the process of flowing the molten resin through the outer wall groove 8a toward the reservoir 6 in the plasticizing step, and the molten resin flows through the outer wall groove. When the molten resin is mixed and kneaded in the flow path, the molten resin and the auxiliary materials are uniformly mixed and kneaded in the reservoir 6.
Is accumulated in

Next, the operation will be described.

In the plasticizing step, as shown in FIG. 1, the hydraulic cylinder 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, whereby 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.

Then, when a resin is charged from a hopper (not shown), the charged resin is kneaded and melted while being transferred forward 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 amount of the molten resin stored in the reservoir 6 reaches a predetermined amount, the screw 2 is stopped.

On the other hand, auxiliary materials such as pulp fiber, glass fiber, various granular materials, and wood powder supplied from the hopper 22 are added to the molten resin flowing through the outer wall groove 8a as described above.
When the molten resin is stored in the reservoir, mixing and mixing given to the molten resin when the molten resin flows through the outer wall groove 8a.
By the kneading action, the added auxiliary material is in a state of being sufficiently kneaded.

As a result, while the molten resin flows through each outer wall groove 8a toward the reservoir 6, the molten resin comes into contact with the cylinder head 4 and is precisely controlled in temperature, and becomes a uniform molten state.
When the molten resin is stored in the reservoir 6, auxiliary materials such as fibers are added and kneaded, and a stable resin state is obtained.

At the same time as the screw 2 stops, the hydraulic cylinder 11 is operated in the direction of pulling in the rod 15 and the lever 10 is rotated in the direction of the arrow to advance the torpedo 7, and the sealing portion 7c at the tip end surface of the torpedo 7
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. Also,
The press-fitting of the sub-material by the plunger 21 is performed only during the plasticizing process, and the sub-material is not injected in the injection and pressure-holding process.

At the time of injection and pressure holding, as shown in FIG. 2, the screw 2 is moved forward with the sealing portion 7c on 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.

By preventing the backflow of the molten resin, the amount of the resin injected into the mold does not vary, and as described above, the molten state of the molten resin is stabilized, and the secondary material is added without fail. However, since this can be uniformly mixed and kneaded with the molten resin and injection can be performed in a good state, a high-quality molded product having high strength and having no defects such as sink marks can be formed stably.

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 in the plasticizing step is constant.

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 is rotated 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
And stored in the reservoir 6. In each outer wall groove 8a of the torpedo 7, auxiliary material such as fiber supplied from the hopper 22 is introduced by the plunger 21 through the through hole 4c.
The molten resin flowing toward the reservoir 6 in the outer wall groove 8a is added and kneaded. When the amount of the molten resin stored in the reservoir 6 reaches a predetermined amount, as shown in FIG.
The torpedo 7 is advanced by rotating the lever 10 in the direction of the arrow to bring the seal portion 7c into contact with the conical inner wall surface 4a of the cylinder head 4, and then the screw 2
Stop the rotation of.

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.

In the above embodiment, the rear groove 8b is formed in the torpedo 7, but when the torpedo 7 is retracted, a gap is formed between the rear end surface and the front end surface of the heating cylinder 1. 7, the rear end groove 8b is not necessarily formed.

[0042]

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

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 into the reservoir as a thin layer 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.

Sub-materials such as pulp fiber, glass fiber, various powders, and wood powder are reliably and easily added to the molten resin flowing through the outer wall grooves from the through holes, and uniformly mixed and kneaded with the molten resin. .

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, a high-quality and high-strength molded article free from defects such as sink marks and reliably added with auxiliary materials such as fibers can be formed.

[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]

 Reference Signs List 1 heating cylinder 2 screw 2a screw groove 3 screw head 4 cylinder head 4a conical inner wall surface 4b cylindrical portion 4c through hole 5 injection nozzle 6 reservoir 6a large diameter portion 6b small diameter portion 7 torpedo 7a flow path forming surface 7b pressure receiving portion 7c Seal portion 8a Outer wall groove 8b Rear end groove 8c Engagement hole 9 Support member 9a Axis 10 Lever 11 Fluid pressure cylinder 12, 13 Pin 14 Bracket 15 Rod 16 Linear drive means for torpedo 17 Bolt 18 Band heater 20 Pot 21 Plunger 22 Hopper 23 Drive cylinder

Claims (1)

[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 equal to the outer diameter of the bottom surface of the screw groove (2a) integrally provided at the tip of the screw, and slidably disposed in the cylinder head in the axial direction. The torpedo (7) with a conical tip
A screw-type injection molding apparatus provided with a torpedo linear drive means (16) for moving the torpedo in an axial direction, wherein the torpedo is slidably fitted in the screw head in a circumferential direction and an axial direction. Large diameter part (6a) on the rear end side
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), and when the torpedo is retracted to separate the seal portion from the conical inner wall surface (4a) of the cylinder head, the reservoir and the screw groove at the tip of the screw are communicated. 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, At least one through hole (4c) configured to apply a pressing force for pressing the seal portion to the conical inner wall surface of the cylinder head due to the pressure of the molten resin applied to the pressure receiving portion, and penetrating the cylinder head ) And a hopper (22) communicating with the through hole.
And a pushing member (21) for supplying an auxiliary material from the hopper to the outer wall groove of the torpedo via the through hole.
A screw-type injection molding apparatus, wherein a sub-material supply apparatus comprising: