JP2020203456A - Injection molding apparatus - Google Patents

Abstract

To provide an injection molding apparatus provided with cooling means capable of satisfactorily suppressing localized overheating of a nozzle body internally installed with a resin channel in which a molten resin is pressure-fed, and capable of easily and surely being arranged in a cylindrical space that surrounds the nozzle body in the hot-runner system injection molding apparatus.SOLUTION: An injection molding apparatus 1 comprises: a nozzle body 2 in which a channel 3 of a molten resin is installed therein; a valve stem 6 which advances/retreats along an axial direction of the nozzle body 2 along a central axis of the channel 3 in the nozzle body 2, and opens/closes a gate g that opens in a tip side of the nozzle body 2; a heater h which is wound around an outer circumferential surface of the nozzle body 2; and a shell body 8 which surrounds the nozzle body 2 via a cylindrical space S between itself and the outer circumferential surface of the nozzle body 2. An air duct 20 is inserted into the space S from a base end side Sa in the space S. A discharge port positioning on a tip end side 21 of the air duct 20 is opened at a tip end side in the outer circumferential surface of the nozzle body 2.SELECTED DRAWING: Figure 1

Description

The present invention relates to an injection molding apparatus of a hot runner type, which can easily and surely suppress overheating of a nozzle body.

For example, a ball that moves up and down due to the pressure of the molten resin is accommodated in the cavity of the nozzle portion that communicates with the cavity of the mold via the gate to prevent the backflow of the molten resin and to be formed on the inner peripheral surface of the cavity. In a hot runner unit provided with a check valve that forms a resin passage that becomes a passage for molten resin when the ball descends and closes the gate located at the lower end of the cavity, the nozzle is cooled along the entire length of the nozzle. Therefore, a hot runner unit including a cooling means including a stainless steel pipe for blowing a compressed gas such as compressed air from a plurality of places has been proposed (see, for example, FIGS. 1 and 2 of Patent Document 1).

However, in the hot runner type injection molding apparatus, the nozzle to which the molten resin is pumped is heated and kept warm by a band heater wound around the outer peripheral surface thereof, and is near the inner peripheral surface in the resin flow path in the nozzle. , And shear heating based on the difference in flow velocity of the molten resin between the vicinity of the surface of the pulp stem that advances and retreats along the central portion of the flow path along the axial direction and the vicinity of the middle of these. In particular, in the case of a nozzle elongated along the axial direction, the vicinity of the nozzle tip on the tip side of the nozzle and the vicinity of the base end side of the nozzle are in contact with the cavity insert, the cavity plate, etc. so as to transfer heat. At the intermediate position in the axial direction of the nozzle, overheating is likely to occur. As a result, there is a risk that the molded resin product may cause product defects such as resin burning.
Moreover, in the case of the hot runner unit of Patent Document 1, what kind of arrangement structure and piping are specifically provided for the cooling means including the air tank, timer, solenoid valve, and stainless steel tube with respect to the hot runner type injection molding device. There is no disclosure as to whether or not it is worn depending on the mode.

Japanese Patent No. 3805198 (pages 1 to 11, FIGS. 1 to 3)

The present invention solves the problems described in the background art and can reliably suppress local overheating of the nozzle body in which the resin flow path through which the molten resin is pumped is provided in the hot runner type injection molding apparatus. Another object of the present invention is to provide an injection molding apparatus provided with a cooling means that can be easily and surely arranged in a cylindrical space surrounding the nozzle body.

Means for Solving Problems and Effects of Invention

In the present invention, in order to solve the above problems, a blower pipe having an outlet opening on the tip end side of the nozzle body is piped along the outer peripheral surface of the nozzle body, and air discharged on the tip end side of the nozzle body and the like are discharged. The idea was to cool the cylindrical space surrounding the nozzle body to a predetermined temperature range by stirring the atmospheric gas that stays in the space between the nozzle body and the outer shell.
That is, the injection molding apparatus (claim 1) of the present invention has a nozzle body in which a flow path of molten resin is internally provided along the axial direction, and the nozzle along the central axis of the flow path in the nozzle body. Between the valve stem that moves forward and backward along the axial direction of the main body and opens and closes the gate that opens to the tip side of the nozzle body, the heater wound around the outer peripheral surface of the nozzle body, and the outer peripheral surface of the nozzle body. An injection molding device including an outer shell that surrounds the nozzle body via a cylindrical space, and a blower tube is inserted into the space from the proximal end side in the cylindrical space, and the blower tube It is characterized in that the discharge port located at the tip is opened on the tip side of the outer peripheral surface of the nozzle body.

According to the injection molding apparatus, the following effects (1) and (2) can be obtained.
(1) Most of the nozzle body in the axial direction is surrounded by the cylindrical space, and the discharge port located on the tip end side of the blower pipe inserted into the space from the base end side is the nozzle body. Since the opening is on the tip end side of the outer peripheral surface of the space, the atmospheric gas in the space is agitated by air or the like discharged from the discharge port. As a result, the cold gas near the inner wall surface of the outer body and the heated gas near the nozzle body are agitated, so that overheating in the intermediate portion of the nozzle body can be prevented, and thus resin burning caused by this can be prevented. It is possible to effectively suppress product defects such as.
(2) Since the discharge port located on the tip end side of the blower pipe inserted from the base end side in the cylindrical space is piped so as to open on the tip end side on the outer peripheral surface of the nozzle body, the structure is simple. It can be easily attached to existing injection molding equipment.

The outer shell includes both a manifold plate and a cavity nesting.
Further, the heater is, for example, a band heater, and a plurality of heaters may be wound apart from each other, or may be in a single form long in the axial direction.
Further, the blower pipe is made of, for example, a metal pipe such as copper, a copper alloy (brass or the like), or stainless steel, and has an outer diameter of about 3 mm or less and a wall thickness of about 1 mm or less.

Further, one or two or more of the blower pipes are piped along the axial direction in the cylindrical space.
Further, the tip portion having the discharge port of the blower pipe is fixed (joined) to the outer peripheral surface of the ring metal fitting wound around the tip end side of the nozzle body by brazing or the like.
Further, on the base end side of the nozzle body in the cylindrical space, a wiring groove for exhausting an atmosphere containing compressed gas (compressed air or compressed nitrogen gas) released into the space to the outside is opened. There is.
In addition, for example, a piston of an air cylinder is connected to the base end side of the valve stem.

The present invention also includes an injection molding apparatus (claim 2) in which the tip end side of the blower pipe is joined to a ring metal fitting attached to the outer peripheral surface on the tip end side of the nozzle body.
According to this, the effects (1) and (2) can be obtained more reliably.
The ring metal fitting has a form in which a pair of flanges extending in the radial direction from both ends of a C-shaped ring body are tightened with bolts and nuts so as to make surface contact with each other, or has a closed ring body on the outside thereof. This includes a form in which the tip of a bolt (set screw screw) penetrating from the center side is abutted against the outer peripheral surface of the nozzle body.

Further, the present invention also includes an injection molding apparatus (claim 3) in which the length of the nozzle body in the axial direction is 10 times or more the outer diameter thereof.
According to this, the effect (1) can be easily and surely obtained even in an elongated nozzle body in which it is difficult to remove heat from the intermediate portion in the axial direction.

The present invention also includes an injection molding device (claim 4) in which the outer diameter of the blower pipe is 3 mm or less.
According to this, the above-mentioned simple piping structure can be easily arranged along the axial direction of the nozzle body in the cylindrical space, so that the effect (2) can be surely obtained. Can be done.
A gap of 3 to 5 mm is usually arranged between the outer surface of the band heater wound around the outer peripheral surface of the nozzle body and the inner wall surface of the cylindrical space.

Further, the present invention also includes an injection molding apparatus (claim 5) in which the intermediate portion of the blower pipe is piped in parallel along the outer peripheral surface of the nozzle body.
According to this, the effects (1) and (2) can be easily obtained.
The "parallel shape" means that the intermediate portion of the blower pipe has a linear shape parallel to the axial direction of the nozzle body, and the intermediate portion has the same spacing along the outer peripheral surface of the nozzle body. It also includes a spiral-shaped form in which the entire circumference is loose from about half a circumference to about one circumference.
Further, the intermediate portion of the blower pipe may be fixed to the outer peripheral surface of the nozzle body via the same ring fitting.

In addition, in the present invention, the timing of blowing air or nitrogen gas from the outlet of the blower pipe into the cylindrical space is the same as the time zone in which the valve stem is retracted and the gate is opened. The injection molding apparatus (claim 6) is also included, which is set based on a time zone or is a time zone equal to or higher than a predetermined temperature detected by a temperature sensor arranged in an axially intermediate portion of the nozzle body. Is done.
According to this, the timing (time) for blowing air or the like from the outlet of the blower pipe into the cylindrical space is the same as the time zone for retracting the valve stem and opening the gate. It is set based on the time zone, or it is set as a time zone of a predetermined temperature or higher detected by a temperature sensor arranged in the middle portion in the axial direction of the nozzle body. Therefore, overheating in the intermediate portion of the nozzle body can be effectively suppressed by a relatively small amount of air or the like. Therefore, the effect (1) can be obtained more efficiently.

The released gas is either compressed air or compressed nitrogen gas, and in the former case, the same air tank as the compressed air used for the air cylinder for advancing and retreating the valve stem may be shared. ..
Further, if the timing is the same or the timing is used as a reference, the solenoid valve of the conduit for discharging the compressed air from the cylinder chamber of the air cylinder and the solenoid valve for air supply on the base end side of the blower pipe are used. Is linked via a relay circuit or the like.

(A) is a cross-sectional view showing one form of an injection molding device according to the present invention, (B) is an external view showing a nozzle body of the injection molding device, and (C) is a tip side of a blower pipe on the tip side of the nozzle body. The perspective view which shows the ring metal fitting which fixes. The schematic graph which shows the temperature change at the time of operation of the injection molding apparatus of an Example according to this invention, and the injection molding apparatus of a comparative example. (A) to (C) are schematic views showing the mounting mode to the nozzle body on the tip side of the blower pipe, and (D) is a schematic view showing the mounting mode to the nozzle body in the intermediate portion of the blower pipe.

Hereinafter, embodiments for carrying out the present invention will be described.
FIG. 1A is a cross-sectional view showing a form of the injection molding apparatus 1 according to the present invention, and FIG. 1B is an external view showing a nozzle body 2 of the injection molding apparatus 1. In these drawings, the lower part in the drawing is referred to as the tip end side, and the upper part in the drawing is referred to as the base end side.
As shown in FIGS. 1A and 1B, the injection molding apparatus 1 has a nozzle body 2 having a cylindrical shape as a whole and having a flow path 3 of molten resin internally provided along the axial direction, and the nozzle body. The gate g at the tip of the nozzle tip 4 attached to the tip side of the nozzle body 2 is opened and closed by moving forward and backward (advancing and retreating) toward the tip side along the central axis of the flow path 3 in 2. A cylindrical space S is provided between the valve stem 6 to be formed, four (plural) band heaters (heaters) h wound around the outer peripheral surface of the nozzle body 2, and the outer peripheral surface of the nozzle body 2. An outer shell 8 that surrounds the nozzle body 2 is provided.

The outer shell 8 is composed of a cavity nesting on the distal end side and a cavity plate on the proximal end side. Further, the nozzle body 2 has an elongated shape whose axial length is 10 times or more that of its outer diameter d. Further, the gap between the outer surface of the band heater h and the inner wall surface of the space S along the radial direction is 3 to 5 mm.
As shown in FIG. 1A, the gate g that opens on the tip end side of the nozzle tip 4 is arranged in a through hole H that is formed on the tip end surface of the cavity insert of the outer shell 8 and communicates with the cavity. ing.

Further, the disk-shaped flange 5 projecting radially from the base end side of the nozzle body 2 is fixed to the manifold 10 adjacent to the base end side, and penetrates through the manifold 10 including a corner portion that bends at a right angle. The flow path 3a of the molten resin (not shown) communicates with the flow path 3 in the nozzle body 2. A nozzle backup ring 11 for positioning the nozzle body 2 is sandwiched between the flange 5 of the nozzle body 2 and the manifold plate 9 that surrounds the manifold 10 with a certain gap.

Further, a manifold back plate 12 is arranged on the base end side of the manifold 10 and the manifold plate 9, and a cylindrical cylinder is formed in a cylindrical recess 13 that opens on the front end side surface of the back plate 12. The material 14 is fitted. In the cylinder chamber C surrounded by the cylinder material 14 and the ceiling surface of the recess 13, a substantially disk-shaped piston 15 is slidably arranged in the vertical direction in the drawing. A base end portion of the valve stem 6 is connected to the central portion of the piston 15. That is, the base end side of the valve stem 6 penetrates the manifold 10 so as to be able to advance and retreat in the vicinity of the corner portion of the flow path 3a of the manifold 10.

The air supply hole 16 and the exhaust hole 17 communicate with each other in the cylinder chamber C, and when compressed air is supplied into the cylinder chamber C from the air supply hole 16, the valve stem 6 advances toward the tip side together with the piston 15. , The tip 7 of the valve stem 6 closes the gate g. On the other hand, when the compressed air in the cylinder chamber C is discharged from the exhaust hole 17, the valve stem 6 retracts to the proximal end side together with the piston 15, and the tip portion 7 of the valve stem 6 opens the gate g. , The molten resin can be injected into the cavity.

Further, as shown in FIG. 1A, an elongated wiring groove Sa extending in the lateral direction in the drawing is formed between the base end side of the outer shell 8 and the tip end side of the manifold plate 9, and the wiring is formed. The groove Sa penetrates the proximal end side 26 of the elongated blower pipe 20 which is piped along both the outer peripheral surface and the axial direction of the nozzle body 2. The blower pipe 20 is made by bending a metal pipe made of a copper alloy such as brass, and has an outer diameter of 3 mm or less and an inner diameter of 1 mm or less. The tip end side 21 of the blower pipe 20 is bent at a substantially right angle along the radial direction of the nozzle body 2 and brazed to the outer surface of the ring metal fitting 23 which is wound and fixed to the outer peripheral surface on the tip end side of the blower pipe 20 ( Joined) r.

The ring metal fitting 23 is made of, for example, a stainless steel plate, has a C-shape as a whole, and has a pair of flanges 24 extending in the radial direction from both ends in the circumferential direction, as shown in FIG. 1 (C). The above-mentioned fixing is achieved by passing bolts through the through holes 25 opened for each of the flanges 24 and screw-joining nuts (none of which are shown).
Further, as shown in FIG. 1B, the plurality (4) of the band heaters h are ring metal fittings 30 fixed to the outer peripheral surface of the nozzle body 2 by set screw screws n at both ends in the axial direction thereof. The position is fixed by. Of these, temperature sensors s1 to s4 are individually arranged for each ring metal fitting 30 on the tip side.
The lead wires on the power supply side of each band heater h and the lead wires of the temperature sensors s1 to s4 (none of which are shown) are wired so as to be energized to the outside through the wiring groove Sa.

In addition, as shown in FIG. 1A, the solenoid valve 19 is located in the middle of the exhaust pipe 18 communicating with the exhaust hole 17, and the solenoid valve 27 is also located on the proximal end side 26 of the blower pipe 20. Have been placed. The solenoid valves 19 and 27 can be interlocked with each other by, for example, a relay circuit 28. That is, the solenoid valve 19 is opened, the compressed air in the cylinder chamber C is discharged from the exhaust pipe 18 through the exhaust hole 17, the valve stem 6 is retracted, the gate g is opened, and the molten resin is formed. Injection is started. At the same time, the solenoid valve 27 is opened through the relay circuit 28.
The base end side 26 of the blower pipe 20 and the air supply hole 16 of the cylinder chamber C may be connected to the same air tank that stores compressed air (not shown).

As a result, as shown by the solid arrow in FIG. 1 (A), the compressed air is pumped into the blower pipe 20 from the base end side 26, and in the cylindrical space S from the discharge port of the tip end side 21. At room temperature, compressed air is released. The compressed air flows through the space S from the tip end side toward the base end side while stirring the atmosphere in the space S, and then from the wiring groove Sa as shown by a broken line arrow in the figure. It is discharged to the outside. During this period, the compressed air is agitated between the heated air on the outer peripheral surface side around the nozzle body 2 and the cold air on the inner wall surface side of the outer body 8 in the axial direction of the nozzle body 2. Since the intermediate position is cooled, overheating in the vicinity of the intermediate position can be suppressed. As a result, it is possible to prevent defects such as resin burning in the product molded by the molten resin injected from the gate g into the cavity.

A method of using the injection molding apparatus 1 having the above-described configuration will be described below.
As shown in FIG. 1A, the valve stem 6 is advanced to close the gate g, and the valve stem 6 is inserted into the flow path 3 of the nozzle body 2 through the flow path 3a in the manifold 10. The molten resin (not shown) is pumped and filled. At the same time, each band heater h is energized, and the nozzle body 2 is heated and kept warm in a temperature range of, for example, about 200 ° C.
First, in order to perform the first injection molding (1st injection), the solenoid valve 19 of the exhaust pipe 18 is opened, the compressed air in the cylinder chamber C is discharged to the outside from the exhaust hole 17, and the valve is discharged together with the piston 15. The gate g is opened by retracting the stem 6. As a result, the molten resin retained in the flow path 3 begins to be injected into a cavity (not shown) through the gate g.

At the same time as the opening operation of the solenoid valve 19, the solenoid valve 27 on the base end side 26 of the blower pipe 20 opens through the relay circuit 28, so that compressed air is pressure-fed from the base end side 26 of the blower pipe 20 to the tip end side 21. It is sequentially discharged from the discharge port to the tip side of the space S.
During this period, as shown in the injection time t1 on the left end side of the graph of FIG. 2, if the temperature change indicated by the temperature sensors s2 and s3 set at the intermediate position of the nozzle body 2 is shown by a solid line, the injection time of the molten resin is shown. Although the temperature starts to rise with the lapse of time, it is suppressed by the gentle temperature rise curve shown by the solid line because it is cooled by the compressed air discharged from the blower pipe 20. The cooling action is generated by agitating the cold air in contact with the inner wall surface of the outer body (cavity nesting and cavity plate) 8 constituting the space S.

When the injection time t1 into the cavity ends, the valve stem 6 advances, the gate g is closed, the solenoid valves 19 and 27 are also closed, and the supply of compressed air into the blower pipe 20 is stopped. , The cooling time t2 of the molten resin injected / filled in the cavity. At this time, the temperature draws a gentle temperature drop curve.
Next, the mold is opened, the molded resin product is taken out from the cavity, and then the mold opening / mold closing time t3 for closing the mold is passed, and the first injection molding (1st injection) is completed. At this time, for example, as shown by the solid line in the graph of FIG. 2, the temperature gradually drops to around the initial 200 ° C.
After that, as shown by the solid line in the graph of FIG. 2, the same temperature curve curve as described above is drawn in the second to fourth injection molding (2nd injection to 4th injection), and the molded resin is formed. There will be no product defects such as resin burning in the product.

On the other hand, when the injection molding of the comparative example in which the first to fourth injection moldings (1st injection to 4th injection) are performed under the same conditions as described above without supplying the compressed air to the blower pipe 20 is performed. As shown by the broken line in the graph of FIG. 2, as the number of injections increases, the temperature detected by the temperature sensors s2 and s3 gradually rises to the high temperature range.
As a result, especially after the second to third injection molding (2nd, 3rd injection), product defects such as resin burning are remarkably likely to occur in the molded resin product.
According to the above-described embodiment, it has been found that the above-mentioned effects (1) and (2) can be surely obtained when the injection molding apparatus 1 including the blower pipe 20 and the like as described above is used.

FIG. 3A shows a form in which the tip end side 21 of the blower pipe 20 is further bent so that its discharge port faces the base end side of the space S.
Further, FIG. 3B shows a form in which the tip end side 21 of the blower pipe 20 is brazed to the outer peripheral surface of the ring metal fitting 30, and FIG. 3C shows the tip end side 21 being released. A form in which bending is further applied so that the outlet faces the base end side of the space S is shown. The position of the ring metal fitting 30 is fixed by a set screw screw n.
Further, FIG. 3D shows a form in which the ring metal fitting 30 is fixed at an intermediate position excluding the band heater h of the blower pipe 20, and the intermediate portion of the blower pipe 20 is brazed to the outer peripheral surface thereof. .. The form may be provided at one location, but by providing two or more locations, overheating in the intermediate portion of the nozzle body 2 can be more reliably suppressed.

The present invention is not limited to the forms described above.
For example, compressed nitrogen gas may be pumped to the blower pipe 20.
Further, as shown in FIG. 1A, the timer T is formed in the relay circuit 28 so that the timing of blowing the compressed air from the blower pipe 20 is from the middle of the injection period t1 to the middle of the cooling period t2. May be arranged and shifted in time. Such timing is particularly recommended in the first and second injection moldings (1st, 2nd injection) shown in the graph of FIG.

Further, at least one of the temperature sensors s2 and s3 arranged in the intermediate portion in the axial direction of the nozzle body 2 opens the solenoid valve 27 according to the time zone when the temperature becomes a predetermined temperature or higher, and the blower pipe 20 is used. Compressed air may be blown out.
In addition, in the injection molding apparatus 1, a plurality of flow paths 3a are point-symmetrically branched in the manifold 10, and the nozzle body 2, the nozzle tip 4, and the valve are located downstream of each flow path 3a. It is a multi-piece type in which a stem 6, a gate g, and the like are arranged. However, the injection molding apparatus of the present invention may be in the form of injection molding into a single cavity.

According to the present invention, in a hot runner type injection molding apparatus, local overheating of a nozzle body having a resin flow path for pumping molten resin can be reliably suppressed, and a cylindrical shape surrounding the nozzle body. It is possible to reliably provide an injection molding apparatus provided with a cooling means that can be easily and surely arranged in the space of.

1 ……………… Injection molding device 2 ……………… Nozzle body 3 ……………… Flow path 6 ……………… Valve stem 8 ……………… Outer body 20 ………… Blower pipe 21… ……… Tip side of blower pipe 23, 30… Ring metal fittings S …………… Space g …………… Gate h …………… Band heater (heater)
d ……………… Diameter of nozzle body

Claims (6)

A nozzle body (2) in which a molten resin flow path (3) is provided along the axial direction, and
A gate (g) that moves forward and backward along the central axis of the flow path (3) in the nozzle body (2) along the axial direction of the nozzle body (2) and opens to the tip side of the nozzle body (2). ) And the valve stem (6)
The heater (h) wound around the outer peripheral surface of the nozzle body (2) and
An injection molding apparatus (1) including an outer shell (8) surrounding the nozzle body (2) via a cylindrical space (S) between the nozzle body (2) and the outer peripheral surface. ,
A blower pipe (20) is inserted into the space (S) from the base end side (Sa) in the cylindrical space (S), and a discharge port located on the tip end side (21) of the blower pipe (20) is provided. An opening is formed on the tip side of the outer peripheral surface of the nozzle body (2).
An injection molding apparatus (1). The tip side (21) of the blower pipe (20) is joined (r) to the ring metal fittings (23, 30) attached to the outer peripheral surface on the tip side of the nozzle body (2).
The injection molding apparatus (1) according to claim 1. The length of the nozzle body (2) in the axial direction is 10 times or more the outer diameter thereof.
The injection molding apparatus (1) according to claim 1 or 2. The outer diameter of the blower pipe (20) is 3 mm or less.
The injection molding apparatus (1) according to any one of claims 1 to 3, wherein the injection molding apparatus (1) is characterized in that. The intermediate portion of the blower pipe (20) is piped in parallel along the outer peripheral surface of the nozzle body (2).
The injection molding apparatus (1) according to any one of claims 1 to 4, wherein the injection molding apparatus (1) is characterized in that. The timing at which air or nitrogen gas is blown into the cylindrical space (S) from the discharge port of the blower pipe (20) is a time zone in which the valve stem (6) is retracted and the gate (g) is opened. It is the same as t1), or it is set based on the time zone (t1), or it is detected by the temperature sensor (s2, s3) arranged in the middle portion in the axial direction of the nozzle body (2). It is a time zone above a predetermined temperature,
The injection molding apparatus (1) according to any one of claims 1 to 5, wherein the injection molding apparatus (1) is characterized in that.

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