JP3028243U - Backflow prevention nozzle of injection molding machine - Google Patents

Abstract

(57) Abstract: A conventional nozzle that prevents a reverse flow of a molten resin at the time of compression in injection compression molding has a resin reservoir having a large volume formed in a resin passage. Resin leakage occurred at the nozzle holes and the mold cavity surface. Further, when a coil spring and its valve receiving member are provided along with the ball for preventing the backflow, the flow resistance of the molten resin increases and the color change resin change occurs. SOLUTION: The backflow prevention mechanism is composed of a ball, a valve seat, and a valve chamber, and the ratio of the diameter of the resin passage to the distance from the center position of the closed state of the ball to the boundary between the resin passage and the nozzle hole is 1 to. It was set to 2.5.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 The present invention relates to a backflow prevention nozzle which is preferably used for injection molding of synthetic resin, particularly for injection compression molding.

[0002]

[Prior art]

 The backflow prevention nozzle shown in FIG. 2 is based on the conventional technique, and the male screw of the nozzle tip 2 is screwed to the female screw provided at the tip of the nozzle body 1. Therefore, the ratio R of the diameter d of the resin passage to the distance L from the center position of the ball in the closed state to the boundary between the resin passage and the nozzle hole is as large as 3.6. On the other hand, Japanese Utility Model Laid-Open Publication No. 6-68810 discloses a prior art in which a coil spring is added to a structure similar to that of the present invention.

[0003]

[Problems to be solved by the device]

 However, when the ratio R exceeds 2.5, a large-volume resin pool is formed in the resin passage 8 in front of the ball 3, and the resin compression amount increases during injection compression, and when the nozzle is separated from the mold, the nozzle is moved. Resin leaks from the holes. Also, when molding is performed while the nozzle is pressed without being separated from the mold at the end of injection compression, resin leakage occurs due to backflow of the compressed resin on the cavity surface of the mold when the movable mold is opened. . Further, the coil spring and the valve receiving member thereof in the publicly known technique of Japanese Utility Model Laid-Open No. 6-68810 are not necessary in the injection compression molding as in the present invention, but rather the flow resistance of the molten resin is increased by the coil spring and the valve receiving member, and the color is changed. This causes defective resin replacement.

[0004]

[Means for Solving the Problems]

 Therefore, a nozzle main body having a resin flow path in the shaft center, a valve seat at the end of the resin flow path, and a male screw on the outer periphery on the same side as the valve seat, and a nozzle body screwed to the male screw. A valve chamber having a female screw that communicates with the resin flow path, a nozzle chip having a nozzle hole that communicates with the resin chamber from the valve chamber to the outside, and a valve chip that is loosely fitted into the valve chamber and does not open. It is composed of balls that are in a closed state in close contact with the valve seat, and the ratio of the diameter of the resin passage to the distance from the center position of the closed state of the ball to the boundary between the resin passage and the nozzle hole is set to 1 to 2.5. Of.

[0005]

[Embodiment of device]

 Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a backflow prevention nozzle according to the present invention, and FIG. 2 is a sectional view of a conventional backflow prevention nozzle, and the same reference numerals are given to members having the same or the same purpose. Reference numeral 1 denotes a nozzle main body, which is provided with a resin flow passage 6 through which a molten resin supplied from a heating cylinder (not shown) is passed through the shaft center, and a male screw 9 for screwing to the heating cylinder at one end outer circumference. Have. In FIG. 1 of the present invention, a male screw 11 for screwing the nozzle tip 2 is provided at the other end of the nozzle body 1, and a valve seat 5 for closely contacting the ball 3 is provided at the end face. On the other hand, in FIG. 2 of the conventional example, a female screw for screwing the nozzle tip 2 is provided at the other end of the nozzle body 1, and a valve seat 5 for closely contacting the ball 3 is provided at the back of the female screw.

The nozzle tip 2 is screwed to the nozzle body 1 to form a nozzle 15, and the tip is pressed against a mold (not shown). The resin flow path 6 of the nozzle body 1 communicates with the valve chamber 4 of the nozzle tip 2, and the valve chamber 4 in the nozzle tip 2 communicates with the nozzle hole 7 via the resin passage 8. The valve chamber 4 is composed of three arcuate cross-section grooves provided on the inner wall at equal intervals and a guide portion 14 which is a convex portion between the arcuate grooves. The guide portion 14 has a step portion for loosely fitting and guiding the ball 3 in the axial direction, and for stopping the ball 3 in a predetermined stroke shorter than the length of the valve chamber in an open state separated from the valve seat 5. The resin passage 8 smoothly communicating with the valve chamber 4 has an inner diameter d, and is smoothly reduced in diameter to communicate with the nozzle hole 7.

If the distance from the center of the closed state of the ball 3 to the boundary between the nozzle hole 7 and the resin passage 8 is L, the ratio R to the inner diameter d of the resin passage 8 is L = 24 mm in the embodiment of the present invention. , D = 11 mm, R = L / d = 2.2. If R is preferably in the range of 1 to 2.5, the resin pool in front of the ball 3 can be substantially reduced and the problem of resin leakage can be avoided.

Reference numeral 10 denotes a thermocouple hole, which is for inserting a thermocouple into the hole to detect the temperature of the nozzle. Based on the temperature signal detected by the thermocouple, the band heater 13 and a controller (not shown) perform closed loop control so that the nozzle temperature reaches a set value.

Next, the operation will be described. After the tip of the nozzle tip is pressed against the mold, the molten resin is filled into the mold through the nozzle hole. At this time, the ball 3 moves from the closed state shown in the figure to the open state (left side in the figure) by the flow pressure of the molten resin until it stops at the step portion of the guide portion 14. In the open state, the molten resin passes through the gap between the opened valve seat 5 and the outer circumference of the ball 3 and the arcuate groove of the valve chamber 4, and flows into the nozzle hole 7 through the resin passage 8. In the injection compression molding, the movable mold of the mold is separated from the fixed mold by a slight distance along with the injection filling, or is separated in advance prior to the injection filling. Therefore, the movable mold, which is separated at a predetermined time after injection filling, is pressed toward the fixed mold by a mold clamping device (not shown), and the molten resin in the mold cavity is compression-molded. At this time, the molten resin flows back from the mold cavity to the nozzle, but the ball 3 moves to the right due to the pressure of the flowing resin, and the ball 3 comes into close contact with the valve seat 5 and is closed. Therefore, backflow of the compressed molten resin is prevented, and the compression process can be performed very effectively.

[0010]

[Effect of device]

 With the simple structure as described above, resin leakage at the nozzle tip and cavity surface is prevented, and backflow is prevented, so injection compression molding can be performed with high accuracy, and the ball is located at the center of the nozzle hole. In addition, since it is provided close to the tip of the nozzle, it has the effect of preventing the stringing phenomenon of the molten resin from the tip of the nozzle.

[Brief description of drawings]

1A is a vertical sectional view of a nozzle showing an embodiment of the present invention, and FIG. 1B is a sectional view taken along the line AA in FIG.

FIG. 2 is a vertical cross-sectional view showing a conventional example of a backflow prevention nozzle.

[Explanation of symbols]

 1 Nozzle Main Body 2 Nozzle Tip 3 Ball 4 Valve Chamber 5 Valve Seat 6 Resin Flow Path 7 Nozzle Hole 8 Resin Passage 9 Male Screw 10 Thermocouple 11 Male Screw 12 Female Screw 13 Band Heater 14 Guide Part 15 Nozzle

Claims (2)

[Scope of utility model registration request] 1. A backflow prevention nozzle which is an injection molding machine nozzle that opens during injection filling and closes during injection compression, and has a resin flow path at its axis and a valve seat at the end of the resin flow path. A nozzle body having a male screw thread on the same outer periphery as the valve seat, a valve chamber having a female thread screwed with the male screw thread of the nozzle body and communicating with the resin flow path, and a resin passage from the valve chamber. A backflow prevention nozzle including a nozzle tip having a nozzle hole communicating with the outside through the ball and a ball that is loosely fitted in the valve chamber and is in an open state and is in close contact with the valve seat. 2. The ratio of the diameter of the resin passage to the distance from the center position of the ball in the closed state to the boundary between the resin passage and the nozzle hole is 1 to 2.5. Backflow prevention nozzle.