JPS5942618B2 - Automatic opening/closing valve gate for plastic injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a nozzle for injecting molten resin into a mold in plastic injection molding, particularly a runnerless type injection molding nozzle for multi-cavity molding.

Among conventional plastic molding nozzles that mold multiple products at once, there are heat gate type and bubble gate type as runnerless injection molding nozzles that do not have sprues or runners.

Heat Gate 2 Nosuru prevents the so-called Hanatan phenomenon by raising and lowering the temperature at the tip of the gate and solidifying the gate with resin. However, there was a drawback in that it was not possible to completely prevent the natale phenomenon.

Valve gate type nozzles require a complex hydraulic power mechanism external to the nozzle to operate the needle valve that opens and closes the gate, and there is a risk of explosion if a resin that is easily decomposed by heat is used.

An internal pressure-type automatic opening/closing valve gate that does not require a power mechanism for opening and closing the needle valve outside the nozzle has been devised, but the total injection pressure, which ranges from several hundred to several thousand kg/crit, is applied to the spring and the valve gate does not require a power mechanism for opening and closing the needle valve outside the nozzle. This had the disadvantage that it required a strong spring, making the device large.

We have improved the internal pressure type automatic opening/closing valve cage by installing a piston (differential pressure piston) with slightly different areas on the front and rear surfaces to reduce the pressure applied to the front and rear surfaces of the differential pressure piston when injection pressure is applied to the resin. There are ideas for differential pressure nozzles that use differential pressure to slide a differential pressure piston to open and close a needle valve, but conventional nozzles require a high level of machining precision and cannot be operated reliably under high resin pressure. It was difficult to manufacture a small, multi-cavity, runnerless nozzle.

This invention improves the differential pressure type automatic opening/closing valve gate, and provides a mechanism to accurately support the front sliding surface of the differential pressure piston in order to maintain the front and rear sliding surfaces in coaxial positions. This system eliminates the drawbacks of the differential pressure piston valve system described above.

The details will be explained below according to the drawings.

The nozzle 20 of the embodiment of the invention shown in FIG.
It consists of

A molten resin inlet 28 passes through the rear end of the cylinder 22, and a gate 30 through which resin is injected into a mold (not shown) passes through the front end of the cylinder 22.

The differential pressure piston 24 built into the cylinder 22 can slide a short distance in the front and back direction, and as the differential pressure piston 24 moves, the needle valve 38 at the tip of the differential pressure piston opens and closes the gate 30. .

The outer diameter of the differential piston front section 46 is slightly larger than the outer diameter of the rear section 48.

The spring 26 that presses the needle valve 38 is connected to the differential pressure piston 2.
It is housed inside a quadruple cavity 62 by the outside of the central part of the cylinder 4 and the inside of the cylinder 22.

The needle valve 38 closes the gate 30 by the spring 26 when no pressure from the molten resin is applied.

An opening 52 bored at the rear of the differential pressure piston 24
The G melt resin is supplied to the gate 30 through a plurality of G melt resin flow paths 50 passing through the differential pressure piston 24 in the front-rear direction.

When the resin is press-fitted from the resin introduction port 28, a force that attempts to move the differential pressure piston 24 forward and a force that attempts to move it backward act simultaneously on the differential pressure piston 24.

Since the area of the differential pressure piston front section 460 is larger than that of the differential pressure piston rear section 48, the differential pressure between the front section 46 and the rear section 48 of the differential pressure piston 24 acts on the spring 26 and increases the pressure of the resin, causing the differential pressure piston to 24 moves rearward against the force of the spring 26, and the gate 30 forcefully opens, allowing resin to be injected into the mold.

When the pressure is reduced, the gate 30 closes automatically.

The cylinder 22 is divided into a cylinder front part 56 and a cylinder rear part 58 for ease of assembly and disassembly.
Both are connected by screws 60.

A cylindrical ring 64 is inserted into the front end of the cylinder rear part 58 and inscribed therein.

A flange projects from the front portion of the ring 64, and the rear end surface of the flange is in contact with the front end surface of the cylinder rear portion 58.

When the cylinder front section 56 is connected to the cylinder rear section 58 by the screw 60, the front end surface of the ring 64 comes into contact with the rear end surface of the cylinder rear section 56, and the ring 64 is prevented from sliding in the front-rear direction.

The inner wall of ring 64 shares a sliding surface with differential piston front 46 .

The cylinder rear part 58 is perforated with a gas vent lower part 8 that penetrates the cavity 62 and the outside.

Therefore, since the cavity 62 is maintained at atmospheric pressure, the differential pressure piston 24 always operates smoothly.

Lubricant escape grooves 70 and 72 are drilled into the outer periphery of the differential pressure piston front part 46 and rear part 48, and MoS2
By applying a lubricant made of silica, graphite, etc. to the differential pressure piston, the lubricant is released into the lubricant relief grooves 70 and 7.
2 and is supplied to the contact area little by little over a long period of time.

Although not shown in the figure, a temperature heater is installed around the nozzle 20 to maintain the resin in a molten state during operation.

A thermoelectric lamp opening 66 is provided in the front part 56 of the cylinder, and a thermoelectric lamp (not shown) is inserted into this opening to measure the temperature near the gate 30, and the nozzle 20 is controlled by a temperature control electric circuit. Controls the current of the heater installed on the outer periphery,
Precise control of the fat-bearing temperature within the nozzle is possible.

A mounting screw 54 is provided on the outer periphery of the rear portion of the cylinder 22.

A backing groove 68 is provided on the rear surface of the cylinder rear portion 58 to prevent porcelain leakage at the nozzle mounting area.

Since this nozzle can be designed to be very compact, it is possible to arrange many of them side by side in one mold.

Of course, it can also be used when molding is performed using one nozzle.

When an injection molding test of a low viscosity m-melt resin such as 6-nylon was conducted using the nozzle of this example, no sagging phenomenon was observed.

As explained above, this invention employs a valve gate system, so the valve can be opened and closed reliably and quickly.There is no Natan phenomenon, and molten resin with low viscosity can be molded. Since it is an internal pressure type automatic opening/closing valve system, no external power is required to open and close the valve, and since a differential pressure piston is used, there is no need for strong springs, the life of the needle valve and gate is long, and the valve is made of resin. Since the appropriate temperature and injection pressure can be set according to the conditions, the quality of the product is improved, and it is also safe because it also serves as an explosion prevention valve in the event that abnormal pressure is generated due to thermal decomposition of the resin.

Since the spring is not in direct contact with the resin yet, even when molding high viscosity resin, the interlocking of the spring is not hindered, the gate opens and closes reliably and quickly, and the life of the spring is long. Furthermore, the nozzle is easy to clean when changing the color or material of the resin.

Since the ring 64 is held by the above-described structure, there is less looseness than when it is fixed by screws, etc., and the sliding surface of the differential pressure piston front section 46 and the sliding surface of the differential pressure piston rear section 48 are fixed. and can be supported in precise coaxial positions.

Therefore, it is easy to improve the accuracy of machining and assembly, which ensures reliable operation of the nozzle, and is particularly effective in realizing a compact nozzle that can be used under high oil pressure.

In other words, since it is designed with an ultra-small nozzle (inner diameter of 0.5 cm to 3.0 cm), when applied to a multi-cavity injection molding machine, the mold size can be reduced and the cost reduction can be reduced to 5 f. With this function, unattended continuous operation of the molding machine is possible, and the injection capacity of the molding machine is substantially increased by 30 to 50 times, and by finely adjusting the temperature of each nozzle, it is possible to improve the quality and uniformity of the product. It has the advantages of being able to

In addition, the ring 64 can be removed, making it easy to disassemble and assemble the nozzle.
2 without changing the shape and dimensions of the piston front part 46.
It is sufficient to use differential pressure pistons 24 with different diameters and rings 64 with corresponding thicknesses.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the invention. 20... nozzle, 22... shilling, 24...
Differential pressure piston, 26... Spring, 28... Resin inlet, 30... Gate, 38... Needle valve, 46... Differential pressure piston front part, 48... Differential pressure piston rear part, 50...
・Flow path, 52...opening, 54...screw for installation,
56...Cylinder front, 58...Nlinter rear,
60...Screw, 62...Cavity, 64...Ring,
66... Thermocouple opening, 68... Backing groove,
70.72...Lubricant escape groove, 78...Gas escape opening.

Claims (1)

[Scope of Claims] 1. A plastic multi-cavity injection molding valve gate provided directly connected to a molding die without using a runner or sprue, with a resin inlet 28 at the rear end and a resin inlet port 28 at the front end connected to the mold. a sill 22 provided with a directly connected gate 30; an ellipsoidal ring 64 whose outer peripheral portion is provided in contact with the front inner wall of the sill 22; a ring 64 provided slidably in the front and rear directions within the sill 22;
A differential pressure piston 24 whose rear outer periphery is in contact with the rear inner wall of the sill 22 and whose front outer periphery is in contact with the inner wall of the ring 64; , a spring 26 that pushes the differential pressure piston 24 forward within a cavity 62 surrounded by the outer periphery of the differential pressure piston 24 and the inner wall of the sill 22; the flow path 50 for the molten resin, and the gate 30 at the sliding front position of the differential pressure piston 24.
A needle valve 38 protrudes forward from the front surface of the differential pressure piston 24 and is coupled to the needle valve 38, which causes the differential pressure piston 24 to slide rearward against the spring 26 when the pressure of the resin exceeds the specified value. It is characterized by having a front area slightly larger than the rear area of the differential pressure piston 24, and the shilling 22 has a hole 66 for a thermoelectric lamp drilled near the gate 30, and a hole 66 at the rear of the shilling 22. An automatic opening/closing valve gate for plastic injection molding, characterized by having a backing ring groove 68 dug around a resin inlet 28 at the end, and a gate 30 projecting forward in a cylindrical shape.