JPS62122729A - Injection molding machine - Google Patents

Abstract

PURPOSE:To make the flow of material smooth and uniform by setting a plunger to be possible to travel forward and backward and to rotate under such a condition that a path for material is being set between the inner surface of a barrel and the outer surface of the plunger, by setting and connecting a material-supplying device under pressure at an inlet of the material set in the rear side of the barrel and by setting a mechanism for preventing a back current in a flow pass. CONSTITUTION:A plunger 24, whose outer diameter is smaller than the inner diameter of a barrel and which has a mechanism for preventing a back current consisting of a check ring 23 and a ball near the top edge, in the barrel 22 and a path for the material 70 is set between the inner surface of the barrel 22 and the outer surface of the plunger 24. A screw 29 for discharging the leaked material is set in the rear side of a cavity 25 of the plunger 24. While the plunger 24 is being placed at the utmost front end and being rotated, a material is loaded in a stuffer 27 and is pressed down by means of a stuffer plunger 30. The material thereby passes through the outer surface part of the plunger 24 and successively stored in the barrel 22. By controlling the oil pressure in the side room of the rod end of the injection cylinder 72, a back pressure can be applied on the material. A known resin material in the plunger 24 can be homogenized by rotating the plunger.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding machine, and in particular to a BMC (BulkModel).
Glass am
The present invention relates to an injection molding machine suitably used for molding materials containing.

[Prior art] Molding materials made by mixing glass fiber with synthetic resins such as unsaturated polyester have various compositions and compositions depending on the application and molding method.
There are properties.

The mechanical properties of a molded product have a strong correlation with the condition of the glass fibers in the molded product; the longer the fiber length and the less bent the better.
Mechanical strength is improved.

The length of the glass fiber in a molded product is not only related to the length of the raw glass fiber, but also to the molding method, and it is important to use a molding method that minimizes breakage as much as possible. It is necessary to improve one's physical characteristics.

Plunger type molding machines have less breakage and bending of glass fibers than screw type molding machines.However, despite these advantages, plunger type molding machines are rarely used in practice. This is due to the following structural drawbacks. Figure 2.3 shows the general structure of the plunger type.

Figure 2 is a schematic configuration diagram of a conventional plunger type injection molding machine, and shows a molding time of 4 m! 1 includes a stuffer 3 and a barrel 4 connected by an elbow 2, and a plunger 6 of a supply cylinder 5 is fitted into the inner hole of the stuffer 3 so as to be able to reciprocate. Further, the plunger 8 of the injection cylinder 7 is fitted into the inner hole of the barrel 4, and the stuffer 3 is fitted into the inner hole of the barrel 4.
The material supply port 9 is opened in the middle of the inner hole near the nozzle 10. 11 is a check valve for preventing material backflow. With this configuration, when the material 12 is introduced into the stuffer 3 and the plunger 6 of the supply cylinder 5 is advanced, the material 12 is supplied into the barrel 4 from the material supply port 9 through the elbow 2. The check valve 11 restricts backflow. Then, by advancing the plunger 8 of the injection cylinder 7, the material 1 in the barrel 4 is
2 can be injected into the mold from the nozzle 10.

Further, FIG. 3 is a schematic configuration diagram showing another example of a conventional plunger type injection molding machine, and the same reference numerals as those in FIG. 2 have the same structure, so a description thereof will be omitted. In this example, the material supply port 9A from the stuffer 3
It differs from the example shown in FIG. 2 in that it opens at the end of the barrel 4A on the side opposite to the nozzle 10 and that there is no check valve 11. By advancing the plunger 6, the material 1 is
2 is supplied into the barrel 4A, and injection is performed by advancing the plunger 8, which is the same as the example shown in FIG.

[Problems to be Solved by the Invention] However, in the conventional molding apparatus shown in FIG. There is an advantage that back pressure can be applied by the injection cylinder 7 and metering is easy and stable, but on the other hand, the material 12 that entered the inner hole of the barrel 4 from the material supply port 9 first is directed toward the plunger 8, The material 12 that entered later is directed toward the nozzle 10, and the material 12 that entered first comes out later during injection, so there is a disadvantage that the material 12 tends to stay. Furthermore, since the seal portion of the plunger 8 passes through the material supply port 9 during injection, the seal portion is likely to be damaged.

Furthermore, in the device shown in FIG. 3, the material supply port 9A is provided closer to the plunger 8, and the material 12 is supplied by retracting the plunger 8 for each shot, so the material 12 that entered first is However, since no back pressure is applied, the metering of the supplied material 12 becomes unstable.
It also has the disadvantage of easily entraining air.

[Means for Solving the Problems] The present invention has been made in view of these points, and it is an object of the present invention to provide a plunger type molding machine that does not have the above-mentioned drawbacks.

In order to achieve the above object, the present invention provides a material passage in the barrel between the inner circumferential surface of the barrel and the outer circumferential surface of the plunger, and provides a plunger so as to be movable back and forth and rotatable, thereby pressing the material. A supply device is connected to the material inlet provided on the rear side of the barrel, and a material backflow prevention mechanism is provided in the material flow path.

In addition, in the present invention, a screw portion for preventing material retention may be provided on the material inlet side portion of the plunger.

[Operation] When the stuffer plunger for material supply is advanced while the plunger located at the front in the barrel of the injection cylinder is rotated, the material is measured and the material at the material supply opening and the outer periphery of the plunger is moved forward. The material is supplied to the tip inside the barrel of the injection cylinder through a passage and a backflow prevention mechanism, and at this time, back pressure is applied by pressurization of the material press supply device. Metering ends when the plunger retreats and the desired amount of BMC etc. accumulates in front of the barrel.After that, when the plunger of the injection cylinder is moved forward, the material is injected from the nozzle, but in this case, the material enters the material path first. Things come out first. Additionally, the rotation of the plunger makes the flow of material extremely smooth and uniform.

Further, the screw for preventing material stagnation has functions such as smoothing the material transfer, homogenizing the material around the plunger, and preventing short circuits in the material flow path.

[Example] FIG. 1 is a schematic vertical sectional view showing an example of an injection molding machine according to the present invention. In the figure, a cylindrical barrel 22 has a nozzle 21 at its tip and a relatively low-temperature heater at its outer periphery. It is arranged in such a way that it can be easily accessed.

62 is a column, 63 is a column nut, 64 is a machine base on the mold clamping device side, 65 is a machine base on the injection device side, 6
Reference numeral 6 denotes a block that is slidably provided on the machine base 65 in the [ direction. On the block 66, the barrel 22 is fixed in the front, and the motor holding member 67 is slidably provided in the rear. installed. 68 is a cylinder for moving the block 66 fixed to the fixed plate 60, 69 is a piston rod, and the tip of the piston rod 69 is attached to the block 66.
The nozzle 21 can be brought into contact with the stationary mold 61 or retracted to the state shown in the figure by the operation of the cylinder 68.

Inside the barrel 22, a plunger 24, which has an outer diameter smaller than the inner diameter of the barrel 22 and has a backflow prevention +h mechanism consisting of a check ring 23, a pawl, etc. near the tip, is provided so as to be movable forward and backward and rotatable. Ta. And barrel 22
A material passage 7 between the inner peripheral surface and the outer peripheral surface of the plunger 24
0 was set.

A shaft of a rotary drive device such as a hydraulic motor 35 fixed to the motor holding member 67 is connected to the rear of the plunger 24 via a bearing portion 71 within the motor holding member 67 .

Further, an injection cylinder 72 and a piston rod 73 are attached between the barrel 22 and the lower side of the motor holding member 67.

A convex portion 25 in contact with the inner circumferential surface of the barrel 22 is provided at the center of the plunger 24. In addition, the convex portion 2 of the plunger 24
A screw 29 for discharging leakage material was provided on the rear side of 5. This screw 29 connects the outer peripheral surface of the convex portion 25 and the barrel 2.
This is for smoothly discharging leaked material rearward from the clearance portion between the inner circumferential surfaces of the barrel 22 to the rear of the barrel 22, and is provided in the opposite thread direction to the rotating direction of the plunger 24.

A stuffer 27 is provided perpendicularly to the material inlet 28 on the rear side of the barrel 22, and the stuffer 27 is provided with a stuffer plunger 30 for pushing down the material. Reference numeral 31 is an inlet provided on the side surface of the stuffer 27 for supplying material. 74 is a cylinder for the stuffer plunger 30;
It is vertically attached to a portion of the barrel 22 facing upward.

75 is a piston rod, and 76 is a connecting member.

In the apparatus shown in FIG. 1, with the plunger 24 positioned at its forward limit and rotating at, for example, 25 to 50 rpm, a material such as BMO is charged into the stuffer 27, and the stuffer plunger Press the material down at 30. The material is then sent forward through the outer periphery of the plunger 24, passes through the check ring 23, and is sequentially collected in the barrel 22 in front of the plunger 24. Of course,
During this metering process, the plunger 24 gradually retreats. In addition, when using BMC as the material, the temperature of the material is set to 40 to 60°C, and the temperature of the injection mold is set to about 1
The temperature was 60° C., and the pressure applied by the stuffer plunger 30 was, for example, several kg/cm'' to 140 kg/crn'.

At this time, back pressure can be applied to the material by controlling the hydraulic pressure in the rod end side chamber of the injection cylinder 72 connected to the rear of the plunger 24. Note that back pressure can also be applied to the material by friction between the outer peripheral surface of the convex portion 25 of the retreating plunger 24 and the inner peripheral surface of the barrel 22.

Rotation of the plunger 24 homogenizes the known resin material of the plunger 24 and prevents shorting of the material flow path. Also, due to the pressing action of the stuffer plunger 30 and the rotating action of the plunger 24, the material is transferred to the plunger 2.
The material is pushed in such a way that it does not pass through only the material passage 70 on the upper side of the plunger 24, but also goes around the material passage 70 on the lower side of the plunger 24, and the material is also pushed from the lower side of the plunger 24 to the upper side, and from the upper side. Since the material is fed while going around to the lower side, even the parts where the material does not flow easily or the material does not stay in the barrel 22, and is smoothly transferred all around the inside of the barrel 22.

When a desired amount of material has accumulated at the tip of the barrel 22, the rotation of the plunger 24 is slowed down, and the injection cylinder 72 is activated to advance the plunger 24 and inject the material into the mold.

In addition, in the apparatus of the present invention, if the material BMC is pushed into the barrel 22 only by the pressing action of the stuffer plunger 30 without rotating the plunger 24, most of the material remains in a part of the barrel 22, The feeding was not smooth and the weighing conditions were extremely poor. Moreover, even if the pressing force by the stuffer plunger 30 was made very large, the metering performance of the BMC was still poor.

However, as in the present invention, the plunger 24 is
If the BMC is pushed in with the stuffer plunger 30 while rotating at a relatively low speed such as ~150 rpm, B
The MC was fed completely inside the barrel 22, and the metering operation was performed smoothly, reliably, and easily.

When BMC is injection molded using the device of the present invention, and when BMC is injection molded using the device using a conventional screw,
Comparing the impact strength of molded products obtained by injection molding, the conventional model had an impact strength of 8 kg-crm/crn', whereas the impact strength of the molded product obtained using the apparatus of the present invention was 13 kg-crm/crn'.
kg-cm/crrf. In addition, if another material is used, the conventional one can produce 11 kg-cra/am'
However, the value obtained using the apparatus of the present invention was 18 kg-cm/cm'.

As described above, the reason why the impact strength of the present invention is significantly improved is that when the BMC is fed into the barrel 22, unlike the case using a conventional screw, the rotation of the plunger 24 causes the glass fibers to This is because it is very unlikely to break, bend, or fall apart.

4 to 7 are sectional views of essential parts showing an injection molding machine according to a modification of the embodiment shown in FIG. 1.

In the embodiment shown in FIG. 4, in the state shown in FIG. 1, the portion of the plunger 24 located below the material supply port 28, that is, the portion immediately in front of the convex portion 25, has a screw for one pitch, for example. 26 were established. This screw 26 part is
Although it is not necessarily necessary to provide it, it acts to prevent material retention depending on the viscosity of the resin used.

When this screw 26 is provided, by rotating the plunger 24, the material can be pushed forward by the screw 26, and even if the material is particularly difficult to flow, it can be prevented from stagnation. Furthermore, it becomes possible to homogenize the resin material around the plunger 24, and it is possible to further prevent short circuits in the flow path of the material, such as passing only through areas where it is easy to flow.

In the embodiment of FIG. 5, the screw 29 shown in FIG.
is omitted, and the convex portion 25 is extended rearward. In the embodiment shown in FIG. 5, the structure can be simplified by omitting the screw 29.

The embodiment shown in FIG. 6 differs from the embodiment shown in FIG. 5 in that the screw 26 provided on a part of the plunger 24 at the material inlet 28 is formed into a helical protuberance 32.

Since the screw 26 as shown in FIG. 5 has an acute-angled (almost right-angled) edge at its tip, there is a risk of damaging the glass Fa fibers contained in the resin material. On the other hand, the sixth
In the illustrated embodiment, since the gentle protuberances 32 are provided, there is little risk that the glass fibers will be damaged by contact between the glass fibers contained in the resin material and the sharp edges.

In addition.

The height h of this spiral protrusion 32 is determined by the ratio h/H of the distance H between the outer circumferential surface of the plunger 24 and the inner circumferential surface of the barrel 22 of 0.9.
This spiral protuberance 3 preferably has a height of 5 or less.
2 can also be provided in other parts of the plunger 24.

The embodiment shown in FIG. 7 differs from the embodiments shown in FIGS. 5 and 6 in that the screw 26 and the helical protuberance 32 are omitted, and that a fluid passage 33 is provided in the plunger 24.

In the embodiment shown in FIG. 7, by passing cooling water or the like into the fluid flow path 33, it is possible to adjust the temperature of the resin material flowing into the barrel 22.

By controlling the temperature in this way, overheating can be prevented, and at the same time, the friction between the souffle 26 and the material can be controlled, and the material feeding ability can be improved.

According to the embodiment shown in FIG. 7, the stirring action of the material inside the barrel 22 near the material inlet is smaller than in FIGS. 5 and 6, but the rotation of the plunger 24 and the stuffer plunger 30 are The material transfer action is performed by pressing. Furthermore, finishing work on the outer surface of the plunger 24 can be simplified by omitting the screw 26 and the spiral protrusion 32.

FIG. 8.9 is a sectional view showing the overall structure of an injection molding machine according to a different embodiment of the present invention. This embodiment is of a so-called double barrel type, and the barrel 22 has a fixed barrel 22A on the front end side and a movable barrel 22B on the rear end side.
It is composed of. The fixed barrel 22A is a movable pro,
It is fixed to a fixed wall 34 fixed on the wall 66A,
A nozzle 21 is provided at its tip. Movable barrel 2
2B has an outer diameter that allows it to slide on the inner surface of the fixed barrel 22A. The movable barrel 22B is integrally fixed and attached to a support portion 38 fixed to a movable block 66B slidably provided on the movable block 66A. 66C is a guide plate. Further, an injection cylinder 42A is provided in the support part 38, and a piston 42 in the injection cylinder 42A is connected to the fixed wall 33 through a piston rod 43.
The supporting part 38 and the movable barrel 22B can be moved in the axial direction with respect to the fixed wall 34 and the fixed barrel 22A by the action of the injection cylinder 42A.

In this embodiment, a hydraulic motor 35 is installed at the rear end of the plunger 24 as a plunger rotation device, and this hydraulic motor 35 is fixed to a movable wall 36 slidably provided on a movable block 66B. ing. Movable wall 36
has a hydraulic cylinder 37, the piston rod 37A of which is connected to the rear end surface of the support portion 38 of the movable barrel 22B. Therefore, by moving the piston rod 37A in and out, the distance between the movable wall 36 and the support part 38 can be changed, and the plunger 24 can be moved back and forth.

The distal end side of the movable barrel 22B is a sloped surface 39 shaped like a forest. On the other hand, an enlarged head 40 is formed at the tip of the plunger 24 , and a truncated conical slope 41 on the rear side of the enlarged head 40 engages with the slope 39 . Therefore, when the piston row 37A is operated to protrude, the plunger 24 moves backward, and the slopes 39 and 41 are brought into close contact with each other to prevent the material in the fixed barrel 22A from flowing back. Further, when the piston rod 2 door 37A is retracted, the plunger 24 moves forward, and communication is established between the inside of the movable barrel 22B and the inside of the fixed barrel 22A.

In this embodiment, first, at the time of measurement, hydraulic pressure is supplied to the chamber on the rod end side of the cylinder 37, and as shown in FIG. At the same time, hydraulic motor 3
5 and rotates the plunger 24, the resin is kneaded and supplied into the fixed barrel 22A through the movable barrel 22B. Material resin is fixed barrel 22
When stored in A, the movable barrel 2 is moved by the pressure of the resin.
2B, after the desired resin material is stored in the fixed barrel 22A in which the plunger 24 retreats while keeping the slopes 39 and 41 separated, the hydraulic circuit of the cylinder 37 is then freed to eliminate the hydraulic pressure; Hydraulic pressure is introduced into the chamber on the left side of the ram 42 provided in the support part 38. Then, the plunger 24 retreats, the slopes 39, 41 abut, and the check portion closes. Since the ram 42 and the fixed wall 34 are connected by the rod 43, the support part 38 moves to the left in the figure, and the movable barrel 22B moves to the fixed barrel 22A.
The resin in the fixed barrel 22A is injected. Alternatively, pressure oil may be supplied to the chamber on the head end side of the cylinder 37 to forcibly retreat the plunger 24 to bring it into contact with the slopes 39, 41, and then inject.

Note that the rear end side of the plunger 24 may be provided with a convex portion 25 and a screw 29 as shown in FIG.
As shown in the figure, only the convex portion 25 may be provided.

FIGS. 10 to 12 show an embodiment in which the backflow prevention mechanism is modified in a double/Herel type injection molding machine.

In the embodiment shown in FIG. 10, the tip of the movable barrel 22B is tapered, and a slope 44 shaped like a trap is formed on the back side of the tip. On the other hand, the tip end surface of the plunger 24 is tapered to form a conical slope 45, and the fixed barrel 2
Prevents backflow of resin material within 2A.

In the embodiment shown in FIG. 11, the distal end portion of the movable barrel 22B is extended to provide a narrow passageway 46 in the axial direction of the movable barrel 22B. Then, a pole housing chamber 47 having a slightly enlarged inner diameter is provided in the middle of this narrow diameter passage 46, and a check pole 48 is inserted into this pole housing chamber 47. When the check pole 48 is in contact with the rear wall surface of the storage chamber 47, communication between the fixed barrel 22A and the movable barrel 22B is cut off, and backflow of the resin material in the fixed barrel 22A is prevented. Note that there is a groove 4 in the front wall of the pole storage chamber 47.
9 is bored, and when the check pawl 48 is pressed against the front wall surface of the pole storage chamber 47, communication between the inside of the movable barrel 22B and the fixed barrel 22A is established through this groove 4.
It is secured through 9.

In the embodiment shown in FIG. 12, an on-off valve 50 is provided in the middle of a passage 46 formed at the tip of the movable barrel 22B. This on-off valve 50 is operated from outside the barrel, and can be opened and closed at desired times. Therefore, during the metering process, this on-off valve 50 is opened to establish communication between the inside of the movable barrel 22B and the inside of the fixed barrel 22A, and during the injection process, it is closed and the inside of the fixed barrel 22A is opened.
Prevent backflow of resin material inside.

13 and 14 are cross-sectional views showing the structure of an injection molding machine according to still another embodiment of the present invention, in which the backflow prevention mechanism is connected to the material inlet section 2 from the stuffer 27 to the barrel 22.
8 is shown.

In the embodiment shown in FIG. 13, a pole accommodating chamber 51 is provided in the material entrance portion 28, and a check pole 52 is inserted into this pole accommodating chamber 51.

When the check pole 52 comes into contact with the wall surface on the stuffer 27 side, backflow of material from the barrel 22 to the stuffer 27 is prevented. In addition, the barrel 22 of the pole storage chamber 51
A groove is formed on the side wall surface, and when the check pawl 52 is in contact with the wall surface on the barrel 22 side, the stuffer 2
The inside of 7 and the inside of barrel 22 are brought into communication through this groove.

In the embodiment shown in FIG. 14, the barrel 22 and the stuffer 27' are separate bodies, and the barrel 22 is rotatable around its axis by a predetermined angle.

The stuffer 27 has a cylindrical portion 53 coaxial with the barrel 22, and the inner circumferential surface of the cylindrical portion 53 slides on the outer circumferential surface of the barrel 22 via a seal member 53a. A rack 54 is provided on the outer peripheral surface of the barrel 22, and a pinion gear 55 that meshes with the rack 54 is rotationally driven by a motor 56.

As shown in FIG. 15, when the opening 57 of the barrel 22 is in the upper position, material is fed into the barrel 22 through the lower end opening 58 of the stuffer 27. As shown in FIG. By rotating the barrel 22 by, for example, 45 inches, the opening 58 is closed by the side surface of the barrel 22, as shown in FIG.
This prevents the resin material in the stuffer 2 from flowing back into the stuffer 27.

Note that even in the double barrel type shown in FIGS. 8 to 12, the material inlet 28 is closed as shown in FIGS. 13 and 14.
A backflow prevention mechanism may be installed.

Further, in the embodiments shown in FIGS. 8 to 14, the plunger 24 may be provided with the screw 26 and the spiral protuberance 32 described above.

The injection molding machine of the present invention has a structure in which the plunger 24 is supported on its base side in a cantilever manner. Therefore, an eccentric load is applied due to the stuffer pressure, which may cause wear and galling to the root support portion of the plunger 24. In order to prevent this phenomenon, it is preferable to adopt a metering method in which the rotation of the plunger 24 is first started so that the material flows uniformly around the plunger 24, and then pressurization of the stuffer is started.

Furthermore, in the injection molding machine of the present invention, the following measures can be taken to prevent the 24 stop positions of the plunger at the end of the metering process from shifting due to the residual pressure of the resin.

(2) A method of reducing the pressure of the stuffer plunger to 0 several to several tens of millimeters before the metering stroke (specifically, for example, the following methods (1) to (2)).

■　■ Method of reducing the pressure in stages.

■ In method (■), the pressure is reduced in one step by feeding back the metering speed.

(2) In the method (2), the measurement end time is predicted from the measurement speed, and the pressure is reduced rapidly or in stages a predetermined period of time in advance.

■ Instead of reducing the pressure, the plunger rotational speed is suddenly or stepwise reduced.

(Incidentally, the methods of ■ to ■ above and the method of method).

■ A method of applying back pressure to the plunger at the end of measurement, or just before the end of measurement, to prevent the plunger from retreating further from the measurement position.

■ Adjust the pressure applied to the stuffer plunger according to the height of the material in the stuffer to compensate for consolidation phenomena. In other words, when the height of the material inside the stuffer is high (a large amount), the pressure is increased, and conversely, when the height of the material inside the stuffer is low (the amount is large)
When the amount is small), lower the pressure.

In each of the above embodiments, an example was shown in which the injection molding machine according to the present invention is used to mold resin such as BMC, but it goes without saying that it can also be used for injection molding of various other plastic materials.

[Effects] As is clear from the above description, in the present invention, since the structure as described in the claims is adopted, fibers are less likely to be cut or bent even when molding resin containing glass fibers, etc. Not only can the plunger-type injection molding machine have the characteristics of less separation, but the material supplied from the material supply device is injected in the order in which it is supplied without switching back and forth, which prevents material from stagnation. Since the backflow of the material is restricted by the action of the backflow prevention mechanism, the injection amount is stabilized. When metering the material, by controlling the rotation speed of the plunger, the pressing force and the back pressure of the stuffer plunger, the metering of the material is extremely stable and the entrainment of air into the barrel is reduced. Further, since the seal portion of the plunger does not pass through the material supply port when the injection plunger moves back and forth, it will not be damaged.

Furthermore, in the present invention, if a screw is provided at the material inlet from the stuffer to prevent material from stagnation, the rotation of the plunger can transfer the material more smoothly without stagnation in areas where it is difficult to flow. As well as being able to
It becomes possible to homogenize the material around the plunger, and it is possible to further prevent short circuits in the material flow path where the material passes only through areas where it easily flows.

If a screw for discharging leaked material is provided at the rear of the convex portion of the plunger, the material leaking from the clearance portion of the convex portion can be smoothly discharged to the outside.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, and FIGS. 2 and 3 are schematic sectional views of a conventional plunger type injection molding machine. FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are sectional views of essential parts showing modifications of the embodiment device of FIG. 1, respectively. FIG. 8 is a longitudinal sectional view of the double barrel type embodiment device, and FIG. 9 is a sectional view taken along the line IX--IX in FIG. 8. 10, 11, and 12 are sectional views of essential parts showing a modification of the embodiment device of FIG. 8. Figures 13 and 14
The figure is a sectional view of a main part of an apparatus according to a further different embodiment. 15 and 16 are cross-sectional views showing the operation of the embodiment device of FIG. 14. 21... Nozzle, 22... Barrel, 22
A...Fixed barrel, 22B...Movable barrel. 23...Check ring, 24...Plunger, 2
6.29...Screw, 27...Staffer 30
...Stuffer plunger, 35...Hydraulic motor, 37.68.74...Cylinder, 39.41...Slanted surface, 40...Enlarged head, 42
A, 72... Injection cylinder, 60... Fixed plate, 61... Fixed mold, 7
0...Material passage.

Claims (2)

[Claims] (1) A material passage is provided in the barrel between the inner circumferential surface of the barrel and the outer circumferential surface of the plunger, the plunger is provided so as to be movable back and forth and rotatable, and the material pressing and feeding device is provided on the rear side of the barrel. An injection molding machine characterized in that a material backflow prevention mechanism is provided in a material flow path and is connected to a material inlet. (2) The injection molding machine according to claim 1, wherein a screw portion for preventing material retention is provided on the material inlet side portion of the plunger.