JPH08127051A - Preplastication type injection molding machine - Google Patents

Abstract

PURPOSE: To precisely and variably set a gap for uniformly melting a resin by further passing the resin plasticized by the screw built in the plasticizing device of a preplastication type injection molding machine through the gap between the rotating screw and a plasticizing cylinder. CONSTITUTION: Stopper members 74, 76 are threaded with the screw grooves 75 carved in the piston rod 50a extending from the piston 50 of the screw moving cylinder 3 taking charge of the forward and rearward advance of a screw 32 to position the movement of the screw moving cylinder 3. Both stopper members are connected so as to take synchronism by a timing belt 79. The teeth of a bevel gear are carved in the outer periphery of the stopper member 76 and the pinion 73 fitted to the drive shaft of a pulse motor 72 is meshed with the teeth of the bevel gear to drive the pulse motor to position the stopper members.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasticizing apparatus for a pre-plastic injection molding machine, which separates plasticizing and injection of rubber or plastic.

[0002]

2. Description of the Related Art One of the inventors has proposed the above-mentioned Jitsuko Sho 59.
-5556 discloses the idea of a basic pre-plastic injection molding machine.

The above-mentioned publication relates to plasticization of resin in an injection molding machine. The plasticizing device has a diameter of the leading end portion that is d1 and is larger than the diameter d2 of the rear flight portion, and the portion for reducing the diameter from the diameter d1 to d2 is tapered for plasticization, and the inner diameter is for plasticizing. It is composed of a plasticizing cylinder having two stages corresponding to the outer diameter of the screw and having a taper step. The screw is allowed to rotate and slightly reciprocate in the plasticizing cylinder.

At the time of plasticizing, the resin supplied from the hopper is plasticized by the screw groove of d2 part of the screw and transferred to the tip side of the screw, but external force is applied to bring the screw and the taper part of the plasticizing cylinder close to each other. , Shearing force is applied to the resin passing through the tapered portion. The resin that has been plasticized and melted in the d2 thread groove is still melted in the tapered portion and becomes a uniform plasticized state. Further, at the time of injection, the screw and the tapered portion of the plasticizing cylinder are brought into contact with each other to prevent the resin flowing back from the injection device. Since this apparatus does not have any valves for preventing backflow, it is characterized by the fact that there is almost no resin retention area peculiar to the valves and that there is no resin retention due to the self-cleaning action.

[0005]

[Problems to be Solved by the Invention] Jitsuko Sho 59-5556
Then, as described above, in the plasticization of the resin performed by the plasticizer, the resin supplied from the hopper is melted and plasticized by the screw groove of the d2 flight portion of the screw and transferred to the tip side of the screw, and the taper portion of the screw and the plasticizing cylinder A force is applied from the outside to maintain a close gap, and a shearing force is applied to the resin passing through the taper to melt the plasticized resin transferred to the screw tip more uniformly. A hydraulic cylinder is used as an actuator for adding the.

Considering the state of actual plasticization, for example, the screw back pressure on the injection device side of the resin transfer destination is zero.
In the case of kg / cm ² , the resin melted and plasticized in the screw groove of the d2 part is forced to pass through the screw and the taper part of the plasticizing cylinder, and the weight of the screw and the spline causes the screw to have a gap between the taper parts. Push in the direction to widen. However, if the screw back pressure is gradually increased, the screw back pressure acts on the tip end diameter d1 of the screw and pushes the screw at a certain point in a direction of narrowing the gap of the taper portion. Further, the hydraulic oil itself expands and contracts slightly due to the change in pressure, and it is necessary to maintain the gap of the tapered portion and change the gap in millimeters, but it was not possible to operate only the cylinder.

[0007]

Even if the plasticizer is a horizontal type and the weight of the screw, spline or the like is negligible, the above problems still exist. Therefore, as a means for solving the problem, the screw is pushed by a force stronger than the force acting on the screw by the hydraulic cylinder, and the stopper is supported by being screwed into the screw groove to position the screw and the taper of the plasticizing cylinder. Accurate and variable clearance is applied to the part. The plasticized resin passes through this gap consisting of the tapered portion of the rotating screw on one side and the tapered portion of the fixed plasticizing cylinder on the other side, and shearing force is applied.

[0008]

[Function] In order to position the plasticizing screw, the force of the hydraulic cylinder that presses against the stopper should be selected to be larger than the force that the screw receives from the resin, and a strong force presses against the stopper to stabilize the shearing force on the resin. Can exercise. In addition, if the stopper is positioned by a screw feed system and a rotary actuator whose feed rate is controllable at a rotation angle level is used, positioning can be performed in units of 1/10 mm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a pre-plastic injection molding machine. Fixed mold 11 attached to fixed plate 13 and movable plate 1
The movable die 10 attached to No. 2 shows a closed state.
When taking out a molded product with a mold clamping cylinder (not shown),
The movable platen 12 can be moved to open the movable mold 10. The injection device 2 can be operated such that the injection device 2 and the plasticizing device 1 are simultaneously moved by a shift cylinder (not shown) to press the nozzle 14 against the fixed mold 11, or the nozzle 14 is moved backward to separate the nozzle 14. The injection screw 15 is inserted into the heating cylinder 23 so as to be able to move forward and backward and rotate. A resin injection port 18 for injecting the plasticized resin from the plasticizing device 1 is provided on the side of the heating cylinder 23.

A seal ring 17 is rotatably provided on the right side of the resin injection port 18. The drive shaft 25 on the right side of the injection screw 15 is received by a bearing device 24 for receiving a thrust load, and a piston rod 27 of the injection cylinder 4 is received via a housing portion 77 of the bearing device 24.
Connected to Since the heating cylinder 23 is fixed to the injection cylinder 4, the injection screw 15 is attached to the heating cylinder 2.
It is moved relative to 3. Also bearing device 2
The shaft of No. 4 is connected to the oil motor 20, and the rotational force of the oil motor 20 is transmitted to the injection screw 15.

Inside the plasticizing cylinder 33 of the plasticizing device 1, a screw 32 having a diameter d1 at the tip 34 and a diameter d2 at the thread groove portion of the flight is inserted. A portion where the tip 34 of the screw 32 changes from d1 to d2 forms a taper portion 35, and the plasticizing cylinder 33 also has a taper step portion in that portion. The right drive shaft 30 of the screw 32 is received by a bearing device 29 for receiving a thrust load, and is connected to a piston rod 50a of the screw moving cylinder 3 via a housing portion 78 of the bearing device 29. The plasticizing cylinder 33 is fixed to the screw moving cylinder 3, and the screw 32 is moved relative to the plasticizing cylinder 33. Further, the shaft of the bearing device 29 is connected to an oil motor 31, and the rotational force of the oil motor 31 is transmitted to the screw 32.

The resin which is put into the hopper 36 of the plasticizing device 1 and plasticized by the screw 32 is injected from the tip of the plasticizing cylinder 33 through the resin passage 19 and into the injection device 2 through the resin injection port 18. Since the plasticizing device 1 and the injection device 2 are separate devices and are connected by the resin passage 19, the resin passage 19 may become long depending on the arrangement of both devices. Although not shown, the plasticizing cylinder 3
3, a band heater is wound around the resin passage 19 and the heating cylinder 23 to keep the resin in a molten state, and the temperature is adjusted.

1 and 2, the plasticizing screw 3
The positioning mechanism 2 will be described. The injection cylinder 33 and the screw moving cylinder 3 are integrally fixed. The piston 50 in the screw moving cylinder 3 has a piston rod extending in both directions, and the piston rod 50a on the right side of the drawing has its tip fixed to the housing 78. Further, the cylinder cover 80 at the right end of the screw moving cylinder 3
The thread groove 7 on the part of the piston rod 50a outside the
5,75 are provided.

A stopper member 76 is provided in the thread grooves 75, 75.
And the stopper member 74 are screwed together. Stopper member 76
Has a two-tiered disc shape, has a female screw threaded in the thread groove 75 at the center, and has a timing belt engraving on one of the outer diameters. Other outer diameters have toothing for spur gears. The width of this spur gear portion is the pinion 73 described later.
The tooth width must be at least 5 mm wider than the tooth width.

The stopper member 74 is disk-shaped and has a female screw at the center which is also screwed into the screw groove 75.
The outer diameter has an engraving for the timing belt that has the same number of teeth as the stopper member 76. For the engraving of the timing belt of both members, a play pulley is used so as not to contact the heating cylinder. A timing belt 79 is installed. A pulse motor 72 with a brake is attached to the side surface of the housing 78, and a pinion 73 is fitted on the drive shaft thereof. The pinion 73 meshes with the spur gear of the stopper member 76.

The screw 32 with respect to the plasticizing cylinder 33
At the time of injection, the taper portion 35 is attached to the plasticizing cylinder 3
3 and contact the taper portion with a gap t during plasticization.
It is necessary to take two positions, that is, keep it at. However, the movement distance X during this period is at most 5 mm. Therefore, the stopper member 76
The tooth width of the spur gear is 5m from the width of the pinion 73 as described above.
When the stopper member 76 is rotated by the drive of the pulse motor 72 and the position of the pinion 73 is displaced from that of the pinion 73, the pinion 73 is not wider than the tooth width of the spur gear. It moves along and never comes off.

Similarly, the rotary encoder 8 is fixed to the side surface of the housing 78, and the pinion 71 fitted in the rotary shaft is meshed with the rack 70 having one end fixed to the screw moving cylinder 3 side, and the plasticizing cylinder 33 The relative positional relationship of the screw 32 is detected.

Next, returning to FIG. 1, the external hydraulic circuit will be described. Of the two variable pumps 37 and 38, the variable pump 37
The riff valve 40 and the solenoid valve 6 are connected to the discharge port.
The outlet of the solenoid valve 6 is connected to each of the two ports of the oil motor 20. This is because the injection screw 15 is normally rotated when the solenoid 6a is excited, and the reverse rotation is performed when the solenoid 6b is excited. The direction of the thread groove of the injection screw 15 can be either right-hand thread or left-hand thread,
Regardless of right or left, the rotation that should proceed in the direction of the resin puddle 16 thereafter is referred to as forward rotation, the rotation away from the resin puddle 16 is referred to as reverse rotation, and the rotation that is not sufficient to distinguish the rotation direction is simply referred to as rotation. To do. The variable pump 38 has a relief valve 41 and solenoid valves 5, 7, 9 connected to the discharge port. Solenoid valve 5
The outlet is connected to the oil chambers 21 and 22 of the injection cylinder 4,
The purpose is to move the injection cylinder 4 forward and backward.

The outlet of the solenoid valve 7 is the screw moving cylinder 3
Indirectly connected to the oil chambers 26 and 28 of the
The purpose is to move the screw moving cylinder forward and backward. The pressure reducing valve 42 connected to the connection port of the oil chamber 26 holds the oil pressure in the oil chamber 26 at a set value when the pressure on the pump side is high, and the pressure on the pump side when the pressure on the pump side is lower than the set value. Is introduced into the oil chamber 26 as it is. The throttle valve 45 at the connection port of the oil chamber 28 has the function of narrowing and narrowing the passage of the operating oil, and the sequence valve 44 prevents the operating oil from passing to the oil chamber 28 when the pressure on the pump side is lower than the set value. Arrest,
When the pressure on the pump side is higher than the set value
Has the effect of introducing into.

The check valves 43 and 46 have a function of returning the hydraulic oil discharged to the tank 47 via the electromagnetic valve 7 when the volume of the oil chamber 26 or 28 is reduced. When the solenoid 9 is excited, the solenoid valve 9 changes the variable pump 38 to the oil motor 3
1 and the oil chamber 22 of the injection cylinder 4 is connected to the relief valve 39 for back pressure.

The operation will be described with reference to the operation table of FIG.
In plasticizing, the solenoids 7a and 9 on the plasticizing device 1 side are excited, and the variable pump 38 drives the oil motor 31 to rotate the screw 32. The resin charged into the hopper 36 is plasticized in the plasticizing device 1, and is sent to the injection device 2 through the resin passage 19 and the resin injection port 18 from the outlet at the tip. At this time, the hydraulic pressure from the variable pump 38 is likewise introduced into the oil chamber 28 to apply a force to the screw 32 in a direction to widen the gap of the tapered portion 35. And stopper members 74, 7
6 receives this, and the gap t of the tapered portion is maintained.
Shear stress is applied to the resin passing through the rotating tapered portion 35.

On the injection device (2) side, the solenoid 6b is excited to drive the oil motor 20 with the variable pump 37. This reverses the injection screw 15 and transfers the resin received at the resin injection port 18 to the resin reservoir 16 at the tip. The injection screw 15 is retracted by the pressure as the resin is transferred to the resin reservoir 16. The oil chamber 22 of the injection cylinder 4 is connected to the back pressure relief valve 39 through the electromagnetic valve 9 since the switching of the electromagnetic valve 9 is completed. The oil chamber 22 is contracted by the retreat of the injection screw 15, and the hydraulic oil is pushed out and passes through the relief valve 39. Therefore, the back pressure of the injection screw 15 can be adjusted by the relief valve 39.

When a certain amount of resin is accumulated in the resin reservoir 16, the position of the injection screw 15 is detected by a position sensor (not shown),
Plasticization is complete. In preparation for the next injection, the plasticizing screw 32 is retracted and the taper portion 35 is brought into contact. This operation is performed by exciting the solenoid 7b. After the contact is completed, the solenoid 7b is demagnetized.

In the next injection step, the solenoids 5a and 6a are excited. A variable pump 38 is installed in the oil chamber 22 of the injection cylinder 4.
Of the pressure oil is introduced, and the injection screw 15 is advanced. At the same time, the variable pump 37 drives the oil motor 20 to rotate the injection screw 15 in the forward direction. And plasticizing device 1
On the side, the generated resin pressure is received by the taper portion 35 to prevent backflow. Since the force generated at the tip 34 is large, there is a risk of damaging the surface of the taper portion 35. To alleviate this, the solenoid 7a is excited and the oil pressure of the variable pump 38 is also introduced into the oil chamber 28 of the screw moving cylinder 3. ing.

The mechanism for positioning the screw 32 with respect to the plasticizing cylinder 33 will be described in detail with reference to FIGS. In the injection process, the screw 32 brings the taper portion 35 into contact with the plasticizing cylinder 33, which is the position where the screw 32 is most retracted. At this time, as shown in FIG. 2, there is an X gap between the stopper members 74 and 76 and the cylinder cover 80. In the plasticizing process, the solenoid 7a of the solenoid valve 7
Is excited and hydraulic oil is introduced into the oil chamber 28, the screw 32
Moves forward, and the stopper members 74 and 76 come into contact with the cylinder cover 80 as shown in FIG. At this time, the taper portion 35
It is necessary to open a gap t between and the taper portion of the plasticizing cylinder 33.

With respect to the method of positioning both stopper members 74 and 76, the solenoid 7b of the solenoid valve 7 is excited to cause the screw 32 to retreat with a weak force due to the low pressure set by the pressure reducing valve 42, and the taper portion 35. And the plasticizing cylinder 33 are brought into contact. The rotary encoder 8 measures this time as a reference position. This position is a position that prevents the reverse flow of resin during injection. Next, the solenoid 7a is excited to move the screw 32 forward, and the position where the stopper members 74 and 76 contact the cylinder cover 80 and stop is measured by the rotary encoder 8 as well.

The above-mentioned reference position and stopper members 74 and 76
From the position where the cylinder abuts the cylinder cover 80, the current gap t
Can be calculated. Then, based on the data measured so far, a command signal to the pulse motor 72 for changing to the gap t to be set can be issued.

For example, if the angle of the taper portion 35 is 90 °, there is a relationship of t = X / √2. This calculation and the relationship between the spur gear of the stopper member 76 and the number of teeth of the pinion 73, the pitch of the thread groove 75 of the piston rod 50a, and the like are calculated by a built-in computer, and a new gap t is set from the current position. A command signal to the pulse motor 72 can be output.

This command signal can be arbitrarily set by operating the setting device from the operation panel. The pulse motor 72 is operated in an open loop, and the rotation angle proportional to the input pulse number can be accurately indicated. However, whether the set gap t is accurate or not is determined by setting a new set position again to the solenoid 7a. Can be confirmed by exciting and measuring with the rotary encoder 8.

The present invention should not be construed as being limited to the above embodiments. In the present application, the two screw moving cylinders 3 are arranged at symmetrical positions with respect to the shaft center of the screw 32. However, in the plasticizing device having a structure in which one screw moving cylinder is arranged at the shaft center of the screw 32, It is also possible to deploy such a mechanism.

Although the injection device has been described with reference to the embodiment in which the mechanism including the injection screw 15 is used, an injection piston is used, and the resin plasticized by the plasticizing device is supplied from the vicinity of the end of the heating cylinder having the nozzle. It is also possible to use it together with an injection device having a mechanism in which it is stored in front of and is injected by the injection piston.

Further, the case where the pulse motor is operated in the open loop for setting the stopper members 74 and 76 has been described, but if a small servomotor is operated in the closed loop instead, the confirmation after the setting becomes unnecessary.

[0033]

The gap t between the taper portion 35 of the screw 32 and the taper portion of the plasticizing cylinder 33 can be accurately positioned in units of 1/10 mm, and the uniformly melted resin without temperature unevenness can be injected into the injection device 2 It is effective for precise molding.

Generally, in the plasticizing device of the pre-plastic injection molding machine, the screw position does not have to be retracted for measuring, and the resin supply position is constant with respect to the screw, so that the plasticized resin state is stable. Therefore, it is not necessary to change the rotation speed of the screw during plasticization. Therefore, the pulse motor 72 does not need to change the gap t during the plasticization in which the load of the screw moving cylinder 3 is applied to the stopper members 74 and 76, and the stopper members 74 and 7 are not required at the beginning of molding.
It is possible to set a position by rotating 6 in a free state while leaving 6 some gap X. Therefore, it is sufficient to use a small-sized pulse motor 72, and once set, the pulse motor 72 remains constant during the molding process.
There is little fatigue and wear of gears.

[Brief description of drawings]

[Figure 1] Pre-plastic injection machine

[Fig. 2] State of the plasticizing device at the time of injection

[Figure 3] Operation table

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasticizing device 2 Injection device 3 Screw moving cylinder 4 Injection cylinder 8 Rotary encoder 15 Injection screw 16 Resin reservoir 18 Resin injection port 19 Resin passage 23 Heating cylinder 32 Screw 33 Plasticizing cylinder 34 Tip 35 Tapered part 50 Piston 50a Piston rod 70 Rack 72 Pulse motor 73 Pinion 74 Stopper member 75 Screw groove 76 Stopper member 80 Cylinder cover

Claims (2)

[Claims] 1. A plasticizing device for plasticizing a synthetic resin by rotating a screw rotatably and reciprocally inserted in a plasticizing cylinder and a rotatably and reciprocatingly inserted in a heating cylinder. From an injection device for injecting the synthetic resin plasticized by the injection screw into a mold from a nozzle, and a resin passage which is a passage for connecting the plasticizing device and the injection device to the plasticized synthetic resin. In the pre-plastic injection molding machine, the stopper extends in the thread groove formed on the piston rod that extends from the piston of the screw moving cylinder in the plasticizing device and is fixed to the bearing housing for receiving the thrust load of the screw. The member is screwed, and it serves as a stopper when the piston rod is drawn into the screw moving cylinder, and meshes with the teeth of the gear carved on the outer periphery of the stopper member. And the pinion driven by the motor, pre-plasticization type injection molding machine, characterized in that Naru adjustable the stopper member in any position. 2. A pre-plastic injection molding machine according to claim 1, wherein the pinion drive motor is a pulse motor.