JPH0236377B2 - PURANJAASHIKISHASHUTSUSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a plunger type injection device used for resin processing.

Conventional configurations and their problems In recent years, as production sites have become more efficient, equipment size and space productivity have come to be evaluated, and the added value of equipment is compared with its dimensional size. It has become like that.

Similar requirements are also emerging for injection molding machines. However, conventionally, the injection device of an injection molding machine has generally been an in-line screw type, and a plunger type, which is advantageous in terms of space, has rarely been adopted. This was due to the fact that the injection performance of the in-line screw type was stable, whereas that of the plunger type was significantly inferior.

FIG. 1 shows a sectional view of a typical configuration of a conventional plunger type injection device.

The through hole 2 of the cylinder 1 is a hole for inserting resin,
Moreover, it fits into the plunger 3. cylinder 1
A flange 4 is screwed onto the flange 4, and a nozzle 5 is screwed onto the flange 4. The cylinder 1, flange 4, and nozzle 5 form a heating cylinder, and a heater 6 is often used as a heating means around the heating cylinder. A torpedo 7 is used in the center of the flange 4, and an orifice hole 8 is provided in a portion that supports the torpedo 7. The nozzle 5 is provided with a hole having a wall surface 9 provided so as to be separated from the convex portion 7b of the torpedo 7 by a certain distance, and the hole communicates with a nozzle hole 10.

In the above structure, the pellet-shaped resin 11 supplied to the cylinder 1 is pushed out toward the torpedo 7 by the plunger 3. Resin 12 represents the resin one cycle before the resin 11 is supplied,
The gap between the pellets is collapsed by the pressure of the plunger 3 of heat from the cylinder 1, and the vicinity of the contact surface with the cylinder 1 is in a molten state. Further, the material introduced in the previous cycle receives shear heat when passing through the orifice hole due to the pressure of the plunger 3, and is completely melted and stored between the convex portion 7b of the torpedo 7 and the nozzle wall 9.
The liquid is ejected from the nozzle hole 10 by the operation of the plunger 3.

The above configuration is a general plunger type injection device, and in some cases, there is also a configuration in which a groove is used instead of an orifice hole.

A feature of the plunger type injection device is that during the injection operation, the resin is pushed out from the orifice hole and injected from the nozzle at the same time. The role of the orifice hole is that when the viscosity of the resin passing through the orifice hole is high, the shear heat generated there increases, the temperature of the resin increases, and the viscosity decreases. The aim is to stabilize the melt viscosity with little change. However, since the mechanical energy applied to the plunger becomes thermal energy due to shear heat generation, the energy of the resin injected from the nozzle hole into the mold (not shown) changes depending on the amount of shear heat generation. As a result, injection molding conditions become unstable.

The degree of instability varies depending on the size of the molded product and variations in the cushion position (lowest position during injection of the plunger) due to variations in the amount of resin supplied, but in any case, it is likely that there is a factor causing instability. This was the reason why the plunger injection method could not be adopted.

Therefore, we first proposed a plunger injection device to solve this problem (Japanese Patent Application No. 73312/1982).
Figure 2 is a typical example.
3, cylinder 14, heater 15, torpedo 1
6. In addition to conventional components such as the nozzle 17, heat transfer fins 18 are provided. 19 is resin, 2
0 is an orifice hole, and 21 is a nozzle hole. Third
The figure is a perspective view of the heat transfer fin. Although the existence of these heat transfer fins has greatly improved, sometimes
The problem remains that resin pellets get caught between the top portion 22 of the heat transfer fin and the plunger 13, making the injection operation of the plunger unstable.

OBJECTS OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a plunger type injection device that is small in size and has stable injection performance.

Structure of the Invention The plunger type injection device of the present invention includes a heating cylinder having a through hole, a torpedo provided inside the heating cylinder, a heating means for raising the temperature of the heating cylinder, and a torpedo that enters the through hole of the heating cylinder. and a heat transfer fin provided inside the heating tube, the heat transfer fin being located between the torpedo and the plunger, and the periphery of the heat transfer fin being in close contact with the inner wall of the through hole of the application tube. The top of the fins, which are provided radially from the center toward the periphery, is inclined with respect to a plane perpendicular to the injection direction of the plunger, and the resin in the center of the heating cylinder is heated by the heat transfer fins. Since the pellets can be heated efficiently and the pellets are fed smoothly, the loss of injection energy of the plunger is reduced and stable molding is possible.

DESCRIPTION OF EMBODIMENTS Hereinafter, explanations will be given based on embodiments of the present invention. FIG. 4 is an external view of a heat transfer fin used in an embodiment of the present invention, in which the top portions 23 of the radially provided fins 22 are sharp and are inclined so that the center portion 24 is higher. There is. 24 is a cylindrical outer periphery that contacts the cylinder.

An embodiment of a plunger type injection device using the heat transfer fins described above is shown in FIG. plunger 25
can enter into the hole 26 of the cylinder 27, and a flange 28 is screwed into the cylinder 27.
A nozzle 29 is screwed onto the flange 28.
The center of the flange 28 has two convex portions 30a, 30.
A torpedo 30 having a diameter b is provided, and a plurality of holes 31 are provided in the support portion of the torpedo 30, which act as orifice holes. The interior of the nozzle 29 is provided with a hole having a wall surface 33 that separates a space 32 from the convex portion 30b of the torpedo 30, and a nozzle hole 34 that communicates with the space 33. The cylinder 27, flange 28, and nozzle 29 form a heating cylinder, and a heater 35 serving as a heating means is provided on the outer periphery of the heating cylinder. Although not shown, a thermocouple for detecting the temperature of the cylinder 27 is embedded in the cylinder 27. The inner wall surface of the cylinder 27 is provided with a step between a small diameter section 36 and a large diameter section 37, and heat transfer fins 38 shown in FIG. 3 are provided in contact with the wall surface of the large diameter section. The space 39 of the heat transfer fin 38 is larger than the pellet size, and the hole 26 of the cylinder 27, the space 39 of the heat transfer fin 38, the hole 31, the space 32, and the nozzle hole 34 are connected to each other, and the heating It forms the through hole of the cylinder.

In the above configuration, the pellet-shaped resin 40 charged into the cylinder 27 is sent downward by the action of the plunger 25. The resin 42 is the resin supplied one cycle before, and when the plunger 25 enters the hole 26 of the cylinder 27, it is compressed and the gaps between the pellets are crushed. Some of the resin is located near the heat transfer fins, and the resin added in the previous cycle is located in the space 39 of the heat transfer fins. In the space 39, the maximum distance from the heat transfer fins is much smaller than the distance from the cylinder wall surface 37 at the center of the hole 26, and the heat transfer effect is proportional to the square of the distance, so the ability to melt the resin is This prevents resin with increased solidification or high viscosity from directly entering the hole 31, and stable conditions can be obtained. Furthermore, even if the resin 40 is pressed against the heat transfer fins, the size of the space 39 is larger than the pellet size and the top portion 41 of the heat transfer fins 38 is slanted, so that the resin 40 in contact with the heat transfer fins is can be entered without difficulty. It is preferable to use a material with good heat conductivity such as aluminum or iron.

Effects of the Invention The present invention has the above-described configuration, and provides the following effects.

(1) Due to the synergistic effect of the preheating effect of the heat transfer fins and the shear heating effect of the torpedo part, uniform plasticization of the resin is possible, good injection performance is obtained, and the dimensions of the molded product are stabilized.

(2) The device is much shorter than the screw method, the configuration is simpler, and a compact and inexpensive molding machine can be obtained.

(3) The pellets are fed smoothly into the cylinder, and the injection operation of the plunger is stabilized, improving the quality of the molded product.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventional plunger type injection device, Figure 2 is a sectional view of a plunger type injection device that we proposed earlier, Figure 3 is an external view of the heat transfer fin used in Figure 2, and Fig. 4 is an external view of a heat transfer fin used in a plunger type injection device according to an embodiment of the present invention, Fig. 5a is a sectional view of a plunger type injection device using the heat transfer fin of Fig. 4, and Fig. 5b is a sectional view taken along line A-A' in FIG. 5a. 26... hole, 31... orifice hole, 32...
Space, 34... Nozzle hole, 27... Cylinder, 2
8...Flange, 29...Nozzle, 30...Torpedo, 35...Heater, 38...Heat transfer fin.

Claims (1)

[Claims] 1. A heating cylinder having a through hole, a torpedo provided inside the heating cylinder, a heating means for raising the temperature of the heating cylinder, a plunger that enters the through hole of the heating cylinder, and a through hole of the heating cylinder. and a heat transfer fin provided in the heating cylinder, the heat transfer fin being located between the torpedo and the plunger, and the periphery of the heat transfer fin being in close contact with the inner wall of the through hole of the heating cylinder,
A plunger-type injection device in which the tops of fins radially extending from the center toward the periphery are inclined with respect to a plane perpendicular to the injection direction.