JPH0242336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection molding machine that is capable of accurately injecting a small volume of synthetic resin or the like.

(Problems of the Prior Art to be Solved by the Invention) Conventionally, the injection amount of a screw in-line injection molding machine is determined by the product of the cross-sectional area of the screw and the stroke. However, it is impossible to arbitrarily reduce the cross-sectional area of the screw due to conditions such as groove depth and mechanical strength, so if the injection amount is small,
There was a problem in that the stroke of the screw was inevitably short, and extremely high precision control was required to improve injection accuracy with a short stroke.

On the other hand, the conventional screw plastic molding machine plasticizes the material in the heating cylinder with a screw, and then plasticizes the material in the heating cylinder through a supply pipe that is perpendicular or oblique to the screw axis.
After feeding into the material storage chamber at the tip of the injection cylinder,
It uses a plunger for injection, and the injection amount is determined by the product of the plunger's cross-sectional area and stroke. Therefore, if the injection amount is small, the stroke can be lengthened by reducing the plunger's cross-sectional area to improve injection accuracy. However, when material is supplied into the tip of the injection cylinder, the material is supplied from the nozzle side to the plunger side as the plunger retreats, so the material that enters the injection cylinder first is injected later. This tends to cause material to stagnate on the injection plunger side, and also creates corners at the connection between the supply pipe and the injection cylinder where it is difficult for material to flow, resulting in material stagnation. For this reason, if the material stays for a long time, it may cause the material to burn.
There were also problems such as difficulty in changing colors (materials).

(Object of the Invention) This invention was devised in order to solve the above-mentioned conventional problems, and the material storage chamber and the screw are arranged concentrically, and the injection plunger fitted into the material storage chamber is arranged as a plunger on a different level. The combined structure of the plunger type injection method and the screw type plasticizing method, which consists of a part and a guide part, and a resin discharge passage is provided in the stepped part of the injection cylinder, prevents material from stagnation, and also prevents the injection plunger from stagnation. By making the diameter smaller, the stroke required for injecting a small volume of material is lengthened to improve metering accuracy and injection accuracy, and to ensure that leaked resin is discharged from between the injection cylinder and the injection plunger. The purpose is to prevent resin from solidifying and clogging.

(Structure of the Invention) The injection molding machine of this invention is equipped with a nozzle,
Further, a heating cylinder in which a screw is fitted concentrically with the material storage chamber is provided to the injection cylinder in which the material storage chamber is formed so as to be movable back and forth in the direction of the screw axis, and the tip of the heating cylinder is provided with the The injection plunger of an injection molding machine in which an injection plunger inserted into a material storage chamber of an injection cylinder is arranged in series is composed of a plunger part and a guide part at different levels, and a passage for discharging leaked resin is provided in the different level part of the injection cylinder. It is characterized by

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. In the drawing, reference numeral 1 denotes an injection cylinder, into which an injection plunger 2 composed of a plunger part 2a and a guide part 2b of different levels is slidably fitted. By retracting the plunger 2, a material storage chamber 3 having an inner diameter approximately equal to that of the plunger portion 2a is formed. A passage 5 for discharging leaked resin is bored in the part. The injection cylinder 1 is supported by left and right supports 7 provided on a frame 6 via tie bars 8.

9 is a plasticizing cylinder, and a screw 10 which will be described later
The plasticizing cylinder 9 has a hole 11 with an inner diameter approximately equal to that of the plasticizing cylinder 9, and the plasticizing cylinder 9 has the cylindrical injection plunger 2 provided with a material passage 12 and a material passage 13 continuous with the material passage 12 at the tip thereof. A cylindrical valve component 14 is installed concentrically with the hole 11. 1
Reference numeral 5 denotes a cylinder heating heater attached to the outer periphery of the injection cylinder 1 and the plasticizing cylinder 9. Reference numeral 16 denotes a water-cooled cylinder for cooling the plasticizing cylinder, and a cylindrical housing 17 is attached to the water-cooled cylinder 16. The housing 17 has a bearing retainer 1 at one end thereof.
A hollow shaft 20 is rotatably mounted via a bearing 21 by a hydraulic motor 19 mounted via a
A proximal end portion of a screw 10 inserted into the plasticizing cylinder 9 is attached to the hollow shaft 20. Thus, the screw 10 is rotatably supported by the housing 17 via the hollow shaft 20 and the bearing 21, and is configured to be rotatable within the plasticizing cylinder 9 by driving the hydraulic motor 19.

A cylinder tube of a double-rod type hydraulic cylinder 22 for injection along the screw axis direction is attached to the left and right sides of the housing 17, and the tip of the piston rod of the hydraulic cylinder 22 is connected to the support 7 and the cylinder tube of the cylinder tube. Similarly, it is attached to left and right supports 23 provided on the frame 6. Thus, while supporting the injection plunger 2, the plasticizing cylinder 9 is supported by the supports 7 and 23 via the hydraulic cylinder 22, and is controlled relative to the injection cylinder 1 by operating the hydraulic cylinder 22 by the switching valve 24. The structure is such that it can move forward and backward in the direction of the screw axis.

In the material passage 13 of the valve component 14, there is a ball 25 which can be seated and closed on the screw 10 side.
A check valve 27 for preventing backflow is provided, which includes a protrusion 26 on the opposite side of the screw 10 to prevent it from falling off and to distribute the material. Thus, the material storage chamber 3 and the groove 28 around the screw 10 are connected by the material passages 12 and 13 via the check valve 27, and when the material pressure on the screw 10 side is high, the check valve 27 opens and communicates. Conversely, when the material pressure on the opposite side of the screw 10 is high (during injection), the check valve 27 is closed and shut off.

Incidentally, 29 is a hopper, which communicates with a material supply port (not shown) provided in the plasticizing cylinder 9 and the water-cooling cylinder 16.

(Function) When the screw 10 is driven by the hydraulic motor 19, the molding material supplied from the hopper 29 is heated and melted by the heater 15, kneaded, and sent through the groove 28 to the tip of the screw. 27 is opened and the material is fed into the material storage chamber 3. The injection plunger 2 is moved back to the right in the figure by the material pressure by the amount of material fed in this manner, and the material is stored in the material storage chamber 3.

When a predetermined amount of material is stored, the control switching valve of the hydraulic motor 19 is closed by a limit switch (not shown) or the like that detects the amount of retreat of the injection plunger 2, the rotation of the screw 10 is stopped, and metering is completed.

Next, when the switching valve 24 is operated from the neutral position to the right position in the drawing by an electric signal to start injection, the cylinder tube of the hydraulic cylinder 22 moves to the left in the drawing, causing the injection plunger 2 to move forward. Therefore, when the material storage chamber 3 is pressurized, the check valve 27 is closed, and the injection plunger 2 moves further forward, the molding material in the material storage chamber 3 is injected into a mold (not shown).

A very small portion of the resin injected at this time flows out from the sliding surface between the injection cylinder 1 and the plunger part 2a of the injection plunger 2 to the guide part 2b side, but this resin flows out from the sliding surface of the injection cylinder 1 and the plunger part 2a of the injection plunger 2. The leaked resin is reliably discharged from the leakage resin discharge passage 5 to the outside and does not stagnate and solidify.

When the injection is completed, the mold side is cooled and released, and at the same time, the screw 10 starts measuring (plasticizing, kneading, extruding) work, and in the above process, the material storage chamber 3
supplies molding materials to

(Effect of the invention) As mentioned above, this invention is concentric with the screw,
In addition, since injection is performed using an independent injection plunger, the diameter of the plunger can be made arbitrarily small regardless of the screw diameter, so even with a small amount of injection, a certain amount of injection stroke can be achieved, improving metering accuracy and injection. Accuracy can be improved, and since plasticization and kneading can be performed using a large-diameter screw as in the past, the plasticization rate is high and the molding efficiency is also higher than in the case of a small-diameter screw. Also, unlike a screw-on plastic molding machine, it uses a first-in, first-out system, and there are no corners in the material passageway where material flows easily, so there is no accumulation of material that can cause burns. Further, since the leaked resin from the sliding surfaces of the injection cylinder and the injection plunger can be reliably discharged, the leaked resin does not solidify and impede the sliding movement of the injection plunger.

Therefore, it is possible to easily adapt to the size of the product, maintain the quality of the product very well, and improve molding efficiency.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a plan sectional view and a front view showing an embodiment of the present invention. 1... Injection cylinder, 2... Injection plunger,
2a...Plunger part, 2b...Guide part, 3...
...Material storage chamber, 4...Nozzle, 5...Leaked resin discharge passage, 6...Frame, 7, 23...Support, 8...Tie bar, 9...Plasticizing cylinder, 1
0... Skrill (groove...23), 12, 13...
Material passage, 15...Cylinder heating heater, 16
...Water-cooled cylinder, 17...Housing, 19...
...Hydraulic motor, 20...Hollow shaft, 21...Bearing,
22...Hydraulic cylinder, 24...Switching valve, 27...
...Check valve.

Claims (1)

[Claims] 1. A heating cylinder in which a screw is fitted concentrically with the material storage chamber is provided on an injection cylinder to which a nozzle is attached and a material storage chamber is formed so as to be movable back and forth in the axis direction of the screw, and the heating cylinder The injection plunger of the injection molding machine has an injection plunger inserted into the material storage chamber of the injection cylinder connected to the tip of the injection cylinder. An injection molding machine characterized by having a passage for use.