JPS61137717A - Injection molding machine - Google Patents

Abstract

PURPOSE:To enable to smoothly drive a needle pin with a small driving force by a structure wherein the rear end of the needle pin is axially slidably fitted into a hole, which is provided within a valve body and communicated with the interior of a cylinder. CONSTITUTION:The rear length of a recessed part 54a, to which the fork 15a of a lever 15 arranged in the rear portion of a needle pin 54 at its both sides, is formed longer than the pin 54. In addition, the pin 54 is made so as to have the same thickness throughout the whole length. A hole is bored at the fitting center of the valve body 55 to a cylinder 7 so as to extend the pin 54 into the cylinder 7 by inserting the rear end of the pin 54 in order to reach said rear end into molten resin 6 in the cylinder 7. Due to the structure as described above, the resultant load applied to the needle pin 54 can be reduced by means of the pressure of resin at injection. Further, because consequenty the driving force of the pin can be reduced, the load on the abutting surfaces 54b and 15b or 54c and 15c of the pin and lever becomes smaller, resulting in enabling to prevent the respective abutting surfaces from damaging.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection molding machine, and particularly to an injection molding machine that can efficiently open, close, or narrow a molten resin passage.

(Prior art) In conventional injection molding machines, resin pressure is applied only to the front end of the needle bin, which controls the opening, closing, or throttling of the molten resin passage in the nozzle. Therefore, when driving the needle bin, a considerably large drive is required. It requires strength. the result,
This has had various problems, such as the need to increase the size of the drive source.

For example, a patent application filed in 1983-9 prior to the present invention
Taking the invention of No. 1856 as an example, this will be explained with reference to the drawings. Fig. 4 is an overall view including the hydraulic circuit of the injection molding machine, Fig. 5 is a detailed view of the nozzle portion, and Figs. 6 and 7.
The figure shows a detailed view of the lever and needle pin.

In FIG. 4, the raw material resin is supplied to a hopper 9 and falls into the cylinder 7, where it is heated by a heater (not shown) and at the same time is melted and plasticized by the rotation of the screw 8 driven by the hydraulic motor 12, and is moved forward of the screw 8. It is sent and stored as molten resin 6.

On the other hand, the solenoid b of the directional control valve 32 is energized, and the hydraulic inflow source 31 is connected to the directional control valve 32 and the proportional electromagnetic flow rate adjustment valve 33.
By sending pressure oil to the head side of the injection cylinder 11 through the injection ram 1o, the screw 8 is advanced to the left in the figure, and the molten resin 6 at the tip of the screw 8 is transferred to the valve body 5.
, and is injected into the molded product cavity 22 through the resin passage of the nozzle 3.

The hydraulic motor shaft L2a is spline-coupled inside the injection ram 10, and can freely slide in the axial direction between the two. In addition, 1 is a stationary side mold, 2 is a movable side mold, 13 is a position detection metal fitting, 14 is a squeegee position sensor, 34 is an electromagnetic relief valve, 35 is an oil pressure sensor, and 30 is a controller.

Next, in FIG. 5, 3a is a nozzle hole, 3b is a resin passage, 5a is a resin passage and is a plurality of holes on the circumference, 23 is a pin, 24 is a bolt, and 25 is an aperture. Now, in FIG. 5, the valve body 5 is attached to the cylinder 7 with bolts 24, and the nozzle 3 is screwed into the valve body 5. The needle pin 4 is slidably fitted into the valve body 5, has a tip forming a diaphragm 25 between it and the nozzle 3, and is connected to a lever 15 at the rear. As shown in FIGS. 6 and 7, the connecting portion of the needle pin 4 and the lever 15 is such that the concave portion 4a of the needle pin 4 and the two prongs 15a of the lever fit together, and the needle pin 4 is moved back and forth in the axial direction by the lever 15. It can be moved. The lever 15 rotates around a pin 23 fixed to the valve body 5.

On the other hand, in FIG. 4, the bracket 20 is attached to the cylinder 7 and rotatably supports the hydraulic cylinder 18 by a trunnion 19. The trunnion 19 protrudes to both sides at the longitudinal center of the hydraulic cylinder 18, and is generally used as a trunnion type hydraulic cylinder. Further, the connecting fitting 17 is attached to the rond of the hydraulic cylinder 18, and the lever 15 is connected to the pin 16.
The position sensor 21 detects the daily stroke position of the hydraulic cylinder.

Further, the pressure oil from the hydraulic inflow source 31 is branched and communicated with a servo valve 36, and the servo valve 36 controls the amount of oil flowing into the hydraulic cylinder 18. , controls the movement of the needle pin 4 via the lever 15. The opening degree of the diaphragm 25 shown in FIG. 5 changes depending on the position of the needle pin 4. Further, the position of the needle pin 4 is detected by detecting the stroke position of the hydraulic cylinder 18 that moves the needle pin 4 with a position sensor 21. Therefore, the opening degree of the throttle 25 at the tip of the needle pin 4 is detected by the position sensor 21, and the throttle opening degree is feedback-controlled by the servo valve 36.

Now, in FIG. 5, since the resin passage is constricted by the throttle 25, when the molten resin passes through the throttle 25 during injection, shear heat generation occurs due to the high-speed flow, and the resin temperature rises. This temperature increase volume can be freely controlled by changing the opening degree of the aperture 25.

If the above configuration is adopted, the load applied to the needle pin 4 during injection will be too large. That is, in FIG. 5, the resin pressure during injection acts on the needle pin 4 from the left, creating a load that tends to move the needle pin to the right. For example, when the diameter d of the needle pin is IC11 and the resin pressure p at the time of injection is 1500 kg/needle bin 4 is moved by the lever 15, the contact surfaces 4b and 15b of both will slide while receiving the load. If you slide it under such a heavy load, there is a risk that the sliding surface will get scuffed.
Practical application becomes difficult. Also, if the load is large, cylinder 1
8. Size of pin 16.23 and other drive system parts,
It is necessary to increase the strength, resulting in disadvantages such as high cost and increased installation space.

(Problems to be Solved by the Invention) According to the present invention, the force for driving the needle pin is increased because resin pressure is applied only in one direction of the needle pin, especially in the nozzle part of the conventional injection molding machine. (This paper focuses on the problem of having to increase the size of the drive source because of the need to do so, and attempts to solve this problem.

(Means for Solving the Problems) Therefore, the present invention provides an injection molding machine in which the rear end of a needle pin that is driven by an external force and opens, closes, or narrows a molten resin passage is connected to a cylinder provided in a valve body. This is a means for solving the problem by fitting a hole that communicates with the inside so that it can slide in the axial direction.

(Function) By employing such a means, substantially equal resin pressure acts on the needle pin at its tip and rear end portions, and the needle pin is smoothly driven with a small driving force.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention, and FIG. 1 is a detailed view of the nozzle part, in which 3 is a nozzle, 3a
is a nozzle hole, 3b is a molten resin passage, 6 is a molten resin, 7 is a cylinder, 15 is a lever, 15a is a two-pronged lever, 16
and 23 are pins, 24 are bolts, and 25 are apertures, which are the same as the conventional example introduced earlier.

Next, focusing on the points different from the conventional example, 54 is a needle pin applied to the present invention, one embodiment is shown in FIG. 2, and FIG. 3 shows another embodiment. It shows. First, the needle pin 54 shown in FIG. 2 is provided with concave portions 54a on both sides of its rear portion to fit with the two prongs 15a of the lever I5. And needle pin 54
The rear length of the concave portion 54a is longer than that of the needle pin mentioned in the conventional example. Also, this needle pin 5
4 is formed to have the same thickness over the entire length, that is, it has the same diameter (φdl''φ,
2). In the needle pin 54 shown in FIG. 3, the rear end diameter φdt of the pin 54 is smaller than the diameter φd1 of the other portions.

The present invention allows these needle pins 54 to be used in an injection molding machine, and for this purpose, a hole is bored in the center of the valve body 55 where it fits into the cylinder 7, as shown in FIG. The rear end of the needle pin 54 is inserted into the hole and extended into the cylinder 7, so that the rear end reaches the molten resin 6 inside the cylinder 7.

In the above configuration, its operation will be explained. In FIG. 1, if the resin pressure in front of the needle pin 54 is Pl, and the resin pressure in the rear is P:, the resultant load F of the resin pressure acting on the needle pin is It can be obtained using the formula below.

During injection, the molten resin flows from the F2 side to the Pl side, so P > P, but since the difference between P and P is small, the composite load F is also small. For example, d,=d,
=1cm, R=1500kg/cat, F2
= 1600kg/cat = 1178-1
257= −79kg ・−1−−−・・・・−・・
(3) Since F2 has become negative, the needle pin is pushed forward (toward Pi) by the resin pressure, but its absolute value is 79k.
g is only 6.7% of the combined load of 1178 kg in the conventional example (1).

Furthermore, if dl > d as shown in Figure 3, then F2
can be brought close to 0. For example, d,=1cm,
Since the values of Pl and F2 change depending on the degree of completeness of the mold during injection, the injection speed, etc., F2 cannot always be set to 0.

(Effects of the Invention) As described in detail above, in the present invention, the composite load acting on the needle pin due to the resin pressure during injection can be significantly reduced compared to the conventional one. Also that needle pin l! l! The force can be significantly reduced, and the contact surface of the needle pin and lever (54b and 15b, or 54c and 15 in Fig. 1)
Since the load c) is reduced, damage to each contact surface can be prevented, and the size and strength of each part of the drive system can be reduced, making it possible to reduce costs and save installation space.

[Brief explanation of the drawing]

FIG. 1 is an enlarged side sectional view of the nozzle part of an injection molding machine showing an embodiment of the present invention, FIG. 2 is a partial perspective view of a needle pin applied to the nozzle part, and FIG. 3 is a partial perspective view of the needle pin and other parts of the nozzle part. FIG. 4 is a partial perspective view showing an embodiment of fJ!, which includes a conventional injection molding machine and its hydraulic circuit diagram. Q sectional view, FIG. 5 is a partially enlarged side sectional view of the nozzle section of the same machine, FIG. 6 is a partial perspective view of the lever applied to the nozzle section, and FIG. 7 is a partial perspective view of the needle bin applied to the nozzle section. FIG. Explanation of main parts of the figure 3 - Nozzle 6 - Molten resin 7 - Cylinder 54 - Two dollar pin Patent applicant Mitsubishi Heavy Industries, Ltd. Figure 4 Figure 5

Claims (1)

[Claims] The rear end of the needle pin, which is driven by an external force to open, close, or throttle the molten resin passage, is fitted into a hole that communicates with the cylinder provided in the valve body so as to be able to slide in the axial direction. Injection molding machine.