JPH0489220A - Nozzle device - Google Patents

Abstract

PURPOSE:To carry out forcible feeding, discontinuing and back-flowing of molten resin and gas in the given period by installing a nozzle device provided with a path for the molten resin and gas, an operating valve at the end opening of a gas path, and a needle valve slidable in the axial direction and a backflow valve inside the operating valve. CONSTITUTION:A nozzle device is composed of an outer shell section and a valve section, and the outer shell section consists of a nozzle main body 4 and a nozzle end 5, while the valve section consists of an operating valve 6 slidable to the nozzle main body 4, a needle valve 7 slidable to the operating valve 6, a gas forcible feeding path 9 opened at the end inside the operating valve 6 through a backflow valve 10 and a gas backflow path 11 starting from a nozzle end 5 and communicated with the rear section of the backflow valve 10. A hollow section is formed in molten resin by gas, and then the backflow path 11 is opened for the required time and gas only is backflowed to control the gas in the hollow section 4 by set pressure. Residual distortion of a resin layer around the hollow section 4 is removed by said arrangement to eliminate the defective product quality.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nozzle device used in a method for compressing a molten resin and a gas body into a mold cavity to obtain a molded body having a hollow portion formed by the gas body. The present invention relates to a nozzle device having a structure that allows press-injected molten resin and gas to flow back to their respective supply sources at set times.

[Prior Art] A nozzle device for pressurizing molten resin and gas into a mold cavity is disclosed in Japanese Patent Laid-Open No. 51-119063, in which a needle valve that is slid by the force of an external drive mechanism opens and closes a resin passage. , discloses a nozzle device in which a gas passage of a non-return valve bone is provided in the core of a needle valve. (
Fig. 3) The nozzle device disclosed in Japanese Patent Application Laid-Open No. 51-119063 has the following features: (a) Passages for the molten resin and the gas are provided independently, and they are not allowed to mix with each other up to the tip of the nozzle device.

b. In the process of pressurizing the molten resin and gas into the mold cavity, do not allow the high-pressure molten resin to flow back into the gas passage.

C. Do not allow the gas to flow back into the injection cylinder while the pressure of the gas is maintained in the mold cavity.

It satisfies the following functions and is used in the method of obtaining a molded article having a hollow part.

However, due to the structure that prevents high-pressure molten resin from flowing backward or leaking into the gas passage, a backward check valve installed in the gas passage prevents the gas pressurized into the mold cavity from entering the mold cavity. It is not possible to control the pressure of the gas inside the cavity to a set pressure by discharging it to the outside.

That is, there is a problem in that the pressure of the gas confined in the space from the backflow prevention valve of the gas passage of the nozzle device to the hollow part in the mold cavity cannot be arbitrarily controlled (for example, lowered in pressure) according to settings.

More specifically, the gas body press-fitted into the core of the molten resin in the mold cavity or the hollow part formed along the thickened part of the mold cavity becomes trapped, causing the hollow part of the mold cavity to become trapped. A gas body under high pressure is retained in the tank, causing various problems.

In general, the pressure of the gas that is press-fitted into the mold cavity is: a) overcoming the resin pressure at the injection port; b) when press-fitting into the sprue runner to form a hollow part;
Allowing the molten resin to flow into the gate and cavity; C. Passing through the gate; d. Allowing the molten resin to flow into the cavity when forming a hollow part within the cavity. Factors such as the viscosity of the molten resin, the design of the mold, and the amount of molten resin filled into the cavity determine the required pressure of the gas injected into the mold cavity.

The gas that is forced into the core of the molten resin in the mold cavity will be assimilated after the hollow part is formed, or after the molten resin in the cavity has been cooled down to below the flow temperature.
Press the resin layer that includes the hollow part to prevent the occurrence of sink marks. However, when the pressure of this gas is high, residual strain is generated in the resin layer including the hollow portion. In particular, if a hollow portion is selectively formed only in a specific position of the cavity, residual strain will be concentrated at the interface between the hollow portion and the solid portion. (Figure 4) When high pressure is applied to the resin layer surrounding the hollow part and residual strain is generated in the resin layer, the following quality defects occur depending on the characteristics of the resin used.

a. Micro-crazing or whitening occurs around the hollow part. Alternatively, crazing occurs over time due to stress relaxation over time after molding.

b. The resin layer surrounding the hollow portion swells. (Figure 5) Furthermore, if an excessively pressurized gas is held in the hollow part of the mold cavity, it is necessary to release the pressure of the gas in the hollow part to atmospheric pressure before removing the molded product. It takes time to process, lengthens the molding cycle (and causes a loss of productivity).

[Problems to be Solved by the Invention] The nozzle device of the present invention has the functions necessary for the nozzle device that presses the above-mentioned molten resin and gas into the mold cavity,
Furthermore, this nozzle device has the following additional new functions.

The first purpose of the nozzle device of the present invention is to pressurize the gas after the molten resin is injected or at the same time as the molten resin, and open the gas backflow passage while maintaining the pressure of the gas. By doing this, the gas that was pressurized and sealed in the space from the backflow prevention valve of the gas injection passage of the nozzle device to the hollow part in the mold cavity is caused to flow back into the gas body backflow passage of the nozzle device, and the gas inside the mold cavity is To reduce the pressure of the gas body in the hollow part to a set pressure and maintain it at a pressure lower than the pressure of the gas body at the initial stage of press-fitting, thereby cooling the resin in the mold cavity and solving the quality defects of molded products that occur. It is in.

The second purpose of the nozzle device of the present invention is to reduce the pressure of the gas in the hollow part of the mold cavity by opening the gas backflow passage while maintaining the pressure of the gas after pressurizing the molten resin and the gas. The objective is to gradually reduce the pressure of the gas in the hollow part to approximately atmospheric pressure when the cooling and solidification of the resin in the mold cavity is completed, thereby shortening the molding cycle.

A third object of the nozzle device of the present invention is that, in a method of pressurizing a gas body after pressurizing molten resin, the injection screw of the injection cylinder is moved backward to reduce the volumetric compression of the molten resin generated by the injection resin pressure. By causing the flow to flow back into the injection cylinder, the resin pressure at the injection port for the gas body is lowered, thereby facilitating the press injection of the gas body.

[Means for Solving the Problems] The above objective is to provide an outer shell portion having a tip opening and a resin passage communicating from the rear opening of the nozzle body to the tip opening; , an operating valve having a tip opening at a position that coincides with the tip opening of the nozzle body; and an operating valve that is installed inside the operating valve so as to be slidable in the axial direction and at a position that substantially coincides with the tip openings of the nozzle body and the operating valve. a needle valve having a tip opening at the top thereof, and a gas body press-in passage opened through a check valve at the tip inside the operating valve, and a gas communicating from the tip opening of the nozzle body to the rear part of the check valve. This is achieved by a nozzle device consisting of a valve body placed inside the shell, with a body backflow passage.

[Operation] The nozzle device of the present invention is a nozzle device having a structure that has passages for molten resin and gas and can open and close each passage at set times by the force of an external drive mechanism,
A nozzle device is attached to the tip of an injection cylinder of a known injection molding machine, and when the tip of the nozzle device is pressed into contact with the inlet of a clamped mold, press-fitting a molten resin and a gas body into a mold cavity;
This is a device that enables the stopping of press-fitting and the backflow of the press-fitted molten resin and gas at a set time.

[Example] Embodiments of the present invention will be described below with reference to FIG.

The nozzle device 3 of the present invention is composed of an outer shell portion and a valve body portion.

The outer shell part consists of a nozzle body 4 and a nozzle tip 5, and the nozzle body 4 is attached to the injection cylinder 1 and receives the molten resin 2 of the injection cylinder 1 through the rear opening 8a. The nozzle tip 5 is in pressure contact with the mold 12, and the resin passage 8. Resin passage front part 8
b is connected to the cavity 14 via the nozzle tip opening 5e and the sprue bush 13 of the mold 12. The resin passage 8 is provided between the core portion of the nozzle body 4 (the sliding portion of the operating valve 6) and the outer periphery.

The valve body part is built into the nozzle body 4, and
an operating valve 6 built into the operating valve 6 so as to be slidable in the axial direction; a needle valve 7 built into the operating valve 6 so as to be slidable in the axial direction;
A gas body press-in passage 9 opens at the tip inside the operating valve 6 via the check valve lO, and a gas body backflow passage 11 communicates from the tip opening 5e of the nozzle tip 5 to the rear part of the check valve 10.
As a result, the operating valve 6 and the needle valve 7 move forward or backward to open or close the resin passage 8 or the gas passage.

In the resin passage 8, the operating valve 6 moves forward and presses the inner inner wall 5b of the nozzle tip 5 and the outer tip outer wall 6a of the operating valve 6, thereby closing the front part 8b of the resin passage, and retreats to release the pressure contact. As a result, the resin passage front portion 8b is opened.

A gas press-in passage 9 inside the operating valve 6 is opened in the front direction and connected to a connection port 9a to a gas supply source (not shown) and a lower end e through a check valve 10 that is closed in the rear direction. Due to the communication and the advancement of the operating valve 6 and needle valve 7, through the tip opening 6e of the operating valve 6 and the tip opening 5e of the nozzle tip 5,
It is connected to the cavity 14 of the mold 12.

The check valve 10 may also be provided with a spring that presses the check ball backward.

The gas backflow passage 11 is a groove or annular groove formed between the inner wall of the core of the operating valve 6 and the outer periphery of the needle valve 7, and the gas backflow passage 11 is a groove or annular groove formed between the inner wall of the core part of the operating valve 6 and the outer circumference of the needle valve 7. It is connected to the passage 9, and the gas can be recovered.

The gas backflow passage 11 is closed when the needle valve 7 moves forward and presses the inner inner wall 6b of the operating valve 6 and the tip outer wall 7a of the needle valve 7, and is opened when the needle valve 7 moves backward and releases the pressure contact. Ru.

Note that the gas backflow passage 11 may be formed inside the needle valve 7 as long as it is located at a position that is closed by the inner wall of the operating valve 6.

The operating valve 6 and the needle valve 7 have lever receiving grooves 6f and 7 into which levers 6c and 7c, which receive the force of an external drive mechanism, are inserted, respectively, at positions corresponding to the spider opening of the nozzle body 4.
Hold f and lever 6c.

The supporting points 6g and 7g of 7c move forward and backward independently by the force of an external drive mechanism. The external drive mechanism uses a known hydraulic or pneumatic actuator (not shown). The force of the external drive mechanism is transmitted to the levers 6c, 7c by connecting rods 6d, 7d and connecting pins 6h, 7h, respectively.

Next, the operation of the nozzle device of the present invention will be explained with reference to drawings of embodiments.

(1) Measuring process Refer to Fig. 2b The operating valve 6 moves forward, the tip inner wall 5b of the nozzle tip 5 and the tip outer wall 6a of the operating valve 6 come into pressure contact, and the resin flow path 8 is closed at the tip. The needle valve 7 also moves forward, and the necessary amount of resin is plasticized and metered by the injection screw 1a of the injection cylinder 1 while the inner wall 6b of the tip of the operating valve 6 and the outer wall 7a of the tip of the needle valve 7 are in pressure contact.

(2) Injection process Refer to FIG. 2a Next, as the injection cylinder 1 moves forward, the tip outer wall 5a of the nozzle tip 5 of the nozzle device 3 comes into pressure contact with the sprue bush 13 of the mold 12 under mold clamping. The actuating valve 6 retreats with the distal end outer wall 7a of the needle valve 7 in pressure contact with the distal inner wall 6b, and the distal inner wall 5b of the nozzle distal end 5 and the distal outer wall 6a of the operating valve 6 are separated, and the resin passage 8 is opened. The injection tube 1a of the injection cylinder moves forward, and the measured molten resin 2 is press-fitted into the cavity 14 via the resin passage 8 of the nozzle device, the tip opening 5e of the nozzle tip 5, and the sprue bush 13. At this time, the backflow prevention valve 10 prevents the molten resin from flowing back into the gas injection passage 9, and the gas backflow passage 11
Since this is closed, backflow to the gas backflow passage 11 is also prevented.

(3) Gas body press-in/holding step See Figure 2b. Next, while the measured molten resin is being press-fitted, the actuating valve 6 is kept in the retracted position while the needle valve 7 is in pressure contact with the needle valve 7 moving forward, and the resin passage 8 After press-fitting the molten resin, the operating valve 6 is moved forward while the needle valve 7 and the operating valve 6 are kept in pressure contact, and the resin passage 8 is closed by the tip opening 5e of the nozzle tip 5. A gaseous body is supplied from a gaseous body source. The gas body passes through the connection port 9a, the gas body press-in passage 9, the check valve 10, the lower e between the tips of the needle valve 7, the tip opening 6e of the operating valve 6, and the tip opening 5e of the nozzle tip 5, and then the metal Through the sprue bush 13 of the mold 12, the molten resin press-fitted into the cavity 14 of the mold 12 is press-fitted into the core part or the core part of the increased thickness part, while forming a hollow part with a gaseous body. The molten resin is forced toward the flow end of the cavity 14, and the resin around the hollow portion is pressed against the inner wall of the cavity 14.

(4) Pressure control process for press-fitted hollow gas body Refer to Fig. 2c After the hollow portion is formed, the supply of gas body from the gas body supply source is stopped, and then, or after being left for a certain period of time, the operating valve 6 is held in the forward position, the needle valve 7 is moved backward, and the pressure contact between the inner wall 6b of the tip of the operating valve 6 and the outer wall 7a of the tip of the needle valve 7 is released. The gas press-in passage 9 of the nozzle device 3 is connected to the tip opening 6e of the actuating valve 6, the tip inner wall 6b of the actuating valve 6, and the tip outer wall 7a of the needle valve 7, with the backflow of the gas being prevented by the check valve 10. It communicates with the gas press-in passage 9 via the gap passage, the gas body backflow passage 11 on the outer periphery of the needle valve 7, and the communication passage 11a. At this time, the gas press-in passage 9 is either opened to the atmosphere outside the nozzle or connected to a low-pressure container (not shown). As the needle valve 7 moves back, the gas that had been press-fitted into the hollow part of the resin core in the cavity 14 of the mold 12 flows backward through the gas backflow passage 9.
The pressure of the gas in the hollow part of the resin core inside the cavity 14 is lowered or gradually lowered.

When the pressure of the gas body press-fitted into the hollow part of the resin core in the cavity 14 drops to the set pressure, moving the needle valve 7 forward again brings the pressure of the gas body in the mold cavity to the lowered set pressure. It can also be retained.

(5) Molded object removal process After the resin, which is press-fitted into the cavity 14 of the mold 12 and has a hollow core, solidifies in the cavity 14, the needle valve 7 is retracted again to prevent the gas backflow failure 9. The remaining gas may be released to the atmosphere from the gas source or collected in a collection vessel. Alternatively, the injection cylinder 1 is moved back to release the pressure contact between the sprue bush 13 of the mold 12 and the nozzle tip 5, and the residual pressure of the gas in the cavity 14 is released to the atmosphere.

Next, the mold clamp of the mold 12 is released, and the movable mold 12b of the mold 12 is
Open it and take out the solidified molded body.

Note that plasticizing and measuring the resin for the next molding process is performed after the molten resin 2 is press-fitted, after the operating valve 6 of the nozzle device 3 moves forward, and while the molten resin press-fitted into the mold 12 is being cooled. .

[Effects of the Invention] As explained above, the nozzle device 3 of the present invention has the following effects.

a. After a hollow part is formed by the gas by injecting the gas at the same time as the molten resin is injected or after the molten resin is injected, the air inside the mold cavity is The gas body sealed in the space up to the hollow part formed in the core of the resin is transferred to the gas body backflow passage of the nozzle device by opening the gas body backflow passage of the nozzle device for the required time. By causing the flow to flow backwards, it is possible to control the holding pressure of the gas body in the hollow part formed in the core of the resin in the mold cavity to a set pressure. After cooling the molten resin in the mold cavity to below the flow temperature, the gas backflow passage of the nozzle device is opened (thereby causing the gas to flow back, so that the molten resin
The gas does not flow back into the gas backflow passage and clog the gas backflow passage.

By controlling the pressure of the gas held in the hollow part formed in the resin core in the above-mentioned mold cavity, excessive residual strain occurring in the resin layer around the hollow part can be alleviated, and microcrazing and whitening can be prevented. It is also possible to eliminate quality defects such as crazing, or swelling of only the surface layer of a molded product that includes a hollow part.

b2 After compressing the molten resin and gas into the mold cavity and forming a hollow part in the core of the molten resin inside the mold cavity, the molten resin inside the mold cavity is poured from the backflow prevention valve of the gas body press-in passage of the nozzle device. The gas body confined in the space up to the hollow part formed in the core of the nozzle device is gradually made to flow back into the gas body backflow passage of the nozzle device by opening the gas body backflow passage of the nozzle device, and the gas body in the hollow part is Control the pressure.

As the molten resin inside the cold mold cavity cools, the pressure of the gas body in the hollow part is gradually lowered to atmospheric pressure, thereby cooling the resin around the hollow part under the excessive pressure of the gas body. - There is no solidification, and the time required to lower the pressure of the gas in the hollow part to atmospheric pressure before opening the mold and taking out the molded product can be shortened, making it possible to shorten the molding cycle.

[Brief explanation of the drawing]

FIG. 1 shows a schematic cross-sectional view of an embodiment of the nozzle device of the present invention. Fig. 2 shows the operation of the nozzle device of the present invention in each process, Fig. 2a shows the process of press-fitting the molten resin, Fig. 2b shows the process of press-fitting and holding the gas body, and Fig. 2c shows the process of press-fitting the hollow gas body. The pressure control process is shown. FIG. 3 is a schematic cross-sectional view of a known nozzle device. FIG. 4 shows the pressure of the gas body in the hollow portion formed by press-fitting the gas body, and FIG. 5 shows the swelling of the surface layer resin due to the pressure retention of the gas body. l...Injection cylinder 1a...Injection screw 2.
... Molten resin 3 ... Nozzle device 4 ... Nozzle body 5 ... Nozzle tip 5e ... Tip opening
6... Operating valve 6e... Tip opening 7...
Needle valve 7e...Tip opening 8...Resin passage 8a...Rear opening 9...Gas body press-in passage O.
... Backflow prevention valve 11... Gas backflow passage 1a...
・Connection path 2 between the gas backflow path and the press-in path... type
13... Sprue bush 4... Cavity

Claims (1)

[Claims] (1) An outer shell having a tip opening and a resin passage communicating from the rear opening of the nozzle body to the tip opening, and installed to be slidable in the axial direction and substantially aligned with the tip opening of the nozzle body. a needle valve that is installed slidably in the axial direction inside the operating valve and has a tip opening at a position that substantially coincides with the nozzle body and the tip opening of the operating valve; , and has a gas body press-in passage opened at the tip inside the operating valve via a check valve, and a gas body backflow passage communicating from the tip opening of the nozzle body to the rear part of the check valve, inside the outer shell part. A nozzle device comprising an installed valve body part.