JPH0976285A - Injector for in-mold coating method and in-mold coating method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To improve the processing accuracy of the in-mold coating method by increasing the injection pressure in the injector and enabling minute measurement. SOLUTION: An injection cylinder 1 equipped with a coating material injection piston 3 is connected to a measuring cylinder 2 for measuring the coating material, and the injection cylinder 1 and the measuring cylinder 2 are integrally configured to be used for an in-mold coating method. Configure the injector. Since the measuring cylinder 3 and the injection cylinder 1 are integrated with the injector, the measured coating material is accurately supplied to the injection cylinder 1 without causing an error. Further, since the coating material is injected by the injection piston 2, high pressure injection is possible.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an injector suitable for injecting a coating agent in an in-mold coating method.

[0002]

2. Description of the Related Art The in-mold coating method of coating the surface of a molded product together with the molding of a molding material in a molding die is particularly suitable for a pin on the surface of the molded product in compression molding such as sheet mold compound (SMC). In recent years, attention has been paid to prevent the generation of holes, improve the surface accuracy of a coated molded article, and reduce the number of working steps. The in-mold coating method includes a pre-coating method in which a coating material is applied to the mold before supplying the molding material into the mold, and a post-coating method in which the coating material is injected into the mold after molding the molded product. is there. Then, as the injection method, a conventional method in which the mold is separated to form a space to inject a coating agent after completion of the molding, and a high pressure method in which the coating agent is injected into the mold at a high pressure without separating the mold, etc. There is. INDUSTRIAL APPLICABILITY The injector of the present invention is suitable for a high pressure injection method represented by a high pressure method, and also for a high pressure injection method in a thermoplastic resin injection molding method.

Conventionally, in the injection of the coating material in the high pressure method, an apparatus having substantially the same structure as that of injecting a resin (for example, a urethane resin raw material or a nylon resin raw material) for a molded product in a normal reaction injection molding. Was used. As shown in FIG. 12, this device incorporates a weighing device 22 in a main body B having a pump 21 for feeding a coating agent,
The coating material was injected from an injector 24 connected to the main body via a rubber hose 23. here,
The injection from the injector relies on the advance pressure of the metering piston of the metering device 22, and the injection piston 25 mounted in the injector 24 is used when the residual resin in the injector is extruded. In addition, the injector 24
Is provided with a retention portion 26 for circulating the coating agent, and cooling water is introduced to prevent gelation of the coating agent (generally a thermosetting resin) retained in the retention portion 26.

In the above conventional device, the weighing device is attached to the main body and is connected to the injector through the rubber hose, and its operation is as follows. At the time of metering shown in FIG. 13, the valve 28 provided in the return path 27 opens, and the coating agent circulates between the pump and the injector. After metering, the valve 28 is closed to stop the circulation, the injection piston 25 is retracted to advance the piston of the metering device, and the forward pressure injects the coating material into the mold 31 (FIG. 1).
4). Next, the injection piston 25 is auxiliary moved forward to extrude the coating material in the injection cylinder into the mold to complete the injection work (FIG. 15). In the figure, reference numeral 32 is a molded product, and 33 is the injected coating material.

[0005]

In the conventional apparatus, the above-mentioned coating material injection method has been the mainstream. Therefore, the upper limit of the injection pressure depends on the pressure resistance of the hose, and at most 3
The limit was about 50 kgf / square centimeter-G. 35
The upper limit injection pressure of about 0 kgf / square centimeter-G is, for example, S
This is a sufficient value for compression molding of MC and the like. However, for example, in injection molding of thermoplastic resin, at least 700 kgf /
Since an injection pressure upper limit of about square centimeter-G is required,
It was difficult to apply the conventional apparatus as it is to the injection molding of the thermoplastic resin. At first glance, this problem seems to be solved by using metallic fixed piping. However, in order to provide the above-mentioned pressure resistance to the pipe, it is necessary to use a considerably thick metal pipe, and the workability such as the detachability from the injector mold is remarkably reduced, which is not a practical solution.

Further, due to deformation of the hose due to the forward pressure of the measuring piston, an error easily occurs between the amount fed from the metering device and the amount ejected from the injector, which makes accurate metering difficult. In addition, since the hose deformation amount changes with time due to hose deterioration, the reproducibility of the injection amount was also poor. For example, in compression molding such as SMC, since there are many relatively large molded products, the change in the film thickness caused by the variation in the injection amount of the coating agent is often hardly noticeable. Further, in the compression molding of SMC, the occurrence of burrs in the molding material cannot be avoided at the time of molding, but by utilizing this, it is possible to absorb the variation in the injection amount by the coating amount on the burrs. However, for example, many thermoplastic resin injection molded products are relatively small in size, and variations in the injection amount of the coating agent directly lead to a large change in the film thickness, which results in short-coated products (on the surface to be coated). It may even be a coated molded product that could be coated only on a part. In addition, since injection molding of a thermoplastic resin hardly causes burrs of the molding material during molding, it is impossible to absorb variations in the injection quantity by the coating amount on the burrs. By the way, in the conventional device, 10c
Where the measurement in units of c is the limit, for example, 1c for in-mold coating for injection molding of thermoplastics
Measurement in units of c or less may be required.

As shown in FIGS. 12 to 15, the minimum injection amount of the conventional device is the stroke volume of the injection piston. In compression molding such as SMC, since there are many relatively large molded products, the minimum injection amount of the coating agent hardly poses a problem. However, for example, thermoplastic resin injection-molded products are often relatively small-sized products, and a considerably small injection amount is often required. At first glance, this problem seems to be solved by reducing the injection piston stroke volume of the conventional device. However, in that case, it is necessary to prepare an injector in which the coating agent chamber and the cooling water chamber exist in a portion of the mold which is considerably close to the cavity, and it is not only very difficult to manufacture in terms of shape, but also the mold is not easily manufactured. Since the coating agent chamber is located deep inside, the cooling capacity of the cooling water is insufficient,
This is not a realistic measure because there is a greater concern that the coating agent will gel in the injector.

Further, since the conventional device is to eject from the injector by the forward pressure of the metering piston,
Deformation of the hose connecting the metering unit and the injector was unavoidable, and as a result, there was a considerable time difference between the advance timing of the metering piston and the actual injection timing, resulting in low responsiveness. In compression molding such as SMC, the solidification cycle of the molding material is comparatively long, and therefore highly accurate control of the injection timing is not always required. On the other hand, for example, in the injection molding process of a thermoplastic resin, the solidification cycle of the molding material is relatively short, so that the variation of the injection timing immediately affects the coating state. For example, if the actual injection time is later than the imaged injection time, a short coat product may occur.

Further, the conventional apparatus is mainly used in such a manner that the coating agent is constantly circulated. However, since there is a resin reservoir inside the injector, the coating agent present in, for example, a hydrodynamic stagnation portion of the resin reservoir is separated from the mold. There was a risk of gelation due to the heat. Therefore, it has been essential to install the cooling mechanism in the conventional injector. In compression molding such as SMC, there are many relatively large molded products, and the mold is large accordingly, so
The demand for miniaturization of the injector was not so serious.
However, for example, in the injection molding method of a thermoplastic resin, there are many relatively small molded products, and accordingly the mold is small. For this reason, the conventional injector has difficulty in mounting (for example, in an injection molding machine, the injector mounted on the mold interferes and the door on the side opposite to the operating side does not close.) The demand for downsizing of the injector is serious. is there.

[0010]

The injector of the present invention has a metering cylinder incorporated in the injector, and by adopting a special flow path structure, high-pressure injection property, metering accuracy, small-quantity metering property, responsiveness, cooling mechanism. Has been made non-essential. That is, a coating material injection piston for ejecting the coating material in the cylinder from the coating material injection opening is mounted in an injection cylinder whose tip is the coating material injection opening, and a measuring cylinder for measuring the coating material is connected to the injection cylinder. Then
The injection cylinder and the measuring cylinder are integrally formed. A circumferential groove is formed on the peripheral wall of the injection cylinder or the injection piston, and an outlet for the coating material is provided on the injection cylinder.
A return path for the coating agent is connected to this outlet, and an axial groove or other flow path is formed between the measuring cylinder and the measuring piston.When the injection piston advances, the injection cylinder or the peripheral wall of the injection piston is formed. The groove formed in the circumferential direction communicates with the outlet, the groove communicates with the measuring cylinder, and the coating material fed to the measuring cylinder passes through the measuring cylinder and the injection cylinder to flow out from the outlet and circulate. With this configuration, the coating agent can be circulated to prevent the coating agent from hardening (claim 2). When the injection piston moves backward, the circumferential groove formed in the injection cylinder or the injection piston is closed between the outlet and the circulation of the coating agent is stopped, so that the injection amount is more accurate ( Claim 3). By configuring the metering cylinder and the injection cylinder so that they do not communicate with each other when the metering piston moves forward, even if the inside of the injection cylinder becomes negative pressure when the injection piston moves backward, the coating from the coating agent supply path to the metering cylinder is performed. The agent is prevented from being sucked and supplied into the injection cylinder, and accurate metering is ensured (Claim 4). If a check valve is installed in the coating material supply path to the measuring cylinder, backflow can be prevented, and accurate metering can be ensured even when a larger amount of coating material is injected than the capacity of the injection cylinder (claim 5).

A sixth aspect of the present invention relates to a measuring and injecting method in the in-mold coating method. A circumferential groove is formed on the peripheral wall of the injection cylinder or the injection piston, and the injection cylinder is provided with a coating material outlet.
When the injection piston is closed, the groove formed in the circumferential direction of the injection cylinder or the peripheral wall of the injection piston communicates with the outlet, and the groove communicates with the metering cylinder, and there is an axial direction between the metering cylinder and the metering piston. Grooves and other flow passages are formed so that the coating material fed to the measuring cylinder passes through the measuring cylinder and the injection cylinder and flows out from the outlet. Using an injector for the in-mold coating method configured so as not to communicate, a molding material made of a thermoplastic resin or a thermosetting resin was molded in the cavity provided in the molding die, and then obtained. The following steps (A) to (E) are continuously performed in the in-mold coating method in which the surface of the molded product is coated with a predetermined amount of coating agent in the cavity. And wherein the Ukoto. (A) The injection piston is arranged at the forward position and the metering piston is arranged at the backward position while keeping the coating agent flowing in the coating agent channel so that the coating agent does not stay in the coating agent channel A step of molding a molding material made of a thermoplastic resin or a thermosetting resin in a cavity provided in a molding die in a state where the coating material of (1) is measured. (B) A step of stopping the circulation of the coating agent and setting the internal pressure in the injector and the peripheral coating agent flow path to 0 kgf / square centimeter-G. (C) Step of retracting the injection piston. (D) A step of advancing the metering piston to supply a predetermined amount of coating material into the injection cylinder, or supplying a predetermined amount of coating material into the injection cylinder and injecting it onto the surface of the molded article in the cavity for coating. (E) A step of advancing the injection piston and injecting the coating agent supplied into the injection cylinder onto the surface of the molded article in the cavity to coat the surface.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The injector A is configured by integrally fixing a measuring section A2 having a measuring cylinder 2 below an injection section A1 having an injection cylinder 1. An injection piston 3 is attached to the injection cylinder 1, and a measuring piston 4 is attached to the measuring cylinder 2. The base end portion of the injection cylinder 1 and the tip end portion of the measuring cylinder 2 are connected by a metal feed pipe 5, and the measuring cylinder 2 is provided with a supply pipe 6 to which a coating agent is supplied from a pump. Check valve 7 is provided at the base of supply pipe 6 with the tip open.
Is installed. In the figure, reference numeral 9 is a plunger for driving an injection piston, and reference numeral 10 is a plunger for driving a measuring piston. When the injector A is attached to the mold, the tips of the injection cylinder 1 and the injection piston 3 may also serve as a part of the mold cavity. Therefore, the injection cylinder 1 and the injection piston 3 are provided with a rotation preventing mechanism. There is.

An axial groove 4a is formed on the peripheral wall of the measuring piston 4. When the metering piston 4 advances, the tip of the metering piston 4 comes into contact with the tip of the metering cylinder 2 and closes the feed pipe 5, so that the metering cylinder 2 and the injection cylinder 1 are not in communication. An annular groove 3a is formed in the circumferential wall of the injection piston 3 in the circumferential direction. The groove 3a is provided at a position corresponding to the opening of the feed pipe 5 when the injection piston 3 is moved forward, and the outflow pipe 8 is provided on the side of the injection cylinder 1 opposite to the feed pipe opening. The base end is open. With this configuration, when the injection piston 3 is in the forward position and the metering piston 4 is in the retracted position (see FIG. 2), the coating material supplied from the supply pipe 6 to the metering cylinder 2 is supplied to the groove 4a of the metering piston 4 and the supply agent. It will flow out of the injector through the delivery pipe 5, the groove 3a of the injection piston 3 and the outflow pipe 8 and the return path 11. That is, the coating agent supplied to the injector during standby does not stay in the injector but circulates, thus preventing the coating agent from hardening.

The axial groove 4a is provided on the peripheral wall of the measuring piston 4 as shown in FIG. 4, but the peripheral wall of the measuring cylinder 2 (FIG. 5), the peripheral wall of the measuring piston 4 and the measuring cylinder 2 (FIG. 4). 6) Alternatively, the groove may be formed all around and the flow path is formed as a slightly large gap 15 between the measuring piston 4 and the measuring cylinder 2 (FIG. 7).

Next, a usage example of the injector A of the above embodiment will be described. The injector A is used by connecting it to a pump for feeding the coating material to be injected with a rubber hose or the like, and the tip of the hose is connected to the supply pipe 6 provided in the measuring section A2. Here, in a state where the injection piston 3 is moved forward and the measuring piston 4 is retracted by an amount equivalent to the measuring amount, the coating material 16 is introduced into the measuring cylinder 2 by the pump 12.
Is supplied to measure the amount of coating material to be injected (FIGS. 2 and 8). At this time, the check valve 7 is open, and the coating agent circulates through the groove 4a of the metering piston and the groove 3a of the injection piston. Next, when the on-off valve 14 is closed to set the internal pressure to 0 and the circulation is stopped, the injection piston 3 is retracted (FIG. 9), and then the metering piston 4 is advanced, so that the measured amount of the coating agent 16 is injected. It is supplied into the cylinder 1. Here, the measuring cylinder 2 and the injection cylinder 1
And the feed pipe 5 is made of metal,
The measured amount is accurately supplied to the injection cylinder 1 (FIGS. 3 and 9). When the measured amount of the coating material 16 is smaller than the volume of the injection cylinder 1, the open space 13 remains in the injection cylinder (FIG. 9). That is, the coating agent is not injected by the forward pressure of the measuring piston 4.
Depending on the conditions on the molding side, the inside of the injection cylinder 1 may be in a negative pressure state when the injection piston 3 moves backward. In this case, when the metering piston 4 moves forward, the tip of the metering piston 4 contacts the tip of the metering cylinder 2 and closes the feed pipe 5,
The measuring cylinder 2 and the injection cylinder 1 are out of communication. That is, by performing the backward movement of the injection piston 3 and the forward movement of the metering piston 4 at substantially the same timing, the coating agent is sucked and supplied from the coating agent supply passage 6 of the measuring cylinder 2 into the open space 13 in the injection cylinder. Can be prevented and accurate measurement can be secured. Next, when the injection piston 3 is moved forward, the entire amount of the coating material in the injection cylinder 1 is injected into the mold 31 at high pressure, and the coating layer 33 is obtained on the surface of the molded product 32 (FIG. 10). After that, the metering piston is retracted to start the next cycle.

The injection piston 3 advances and the metering piston 4
In the standby state, the coating material supplied from the pump reaches the injection cylinder 1 from the groove 4a of the measuring piston 4 through the feed pipe 5 and the outflow pipe 8 through the groove 3a provided in the injection piston 3 to the outside of the injector. Flow to the pump side. In this coating agent circulation, the coating agent does not stay in the injector, and the coating agent does not harden even without cooling. It is not an essential requirement that the above-mentioned circulation action be obtained.

The above operation is when the amount of coating material to be metered and injected is smaller than the capacity of the injection cylinder 1 (first mode), but when a larger amount of coating material than the capacity of the injection cylinder 1 is metered and injected ( The second mode (see FIG. 11) has the following procedure. That is, when the metering piston 4 is moved backward and weighed, and then the metering piston 4 is advanced, an amount exceeding the injection cylinder volume in the metering coating material is injected and injected into the mold 31 by the advancing of the metering piston 4. Next, when the injection piston 3 is moved forward, the coating material in the injection cylinder 1 is injected and injected, so that the measured total amount is accurately injected. Here, since the check valve 7 is attached to the measuring unit, there is no possibility that the coating material flows back to the pump side even when high pressure is generated by the measuring piston 4, and unlike the external check valve, It is arranged in the immediate vicinity of the cylinder 2,
Moreover, since there is no play such as a rubber hose, it is possible to prevent an error in the amount of the coating material injected.

The injection amount is less than or equal to the capacity of the injection cylinder 1 (first
2), the pressure of the measuring piston 4 may be a pressure capable of feeding the coating material in the measuring cylinder 2 to the injection cylinder 1, and it is not necessary to obtain a high pressure. If the measuring piston 4 has a low pressure, the check valve 7 does not necessarily have to be installed. Further, the feeding pipe 5 and the feeding pipe 6 are not limited to metal pipes as long as they are rigid materials.

[0019]

EXAMPLE When the numerical values of the main parts were set as follows, extremely good injection pressure, metering performance and responsiveness could be obtained. Inner diameter of injection cylinder 1 is 6 mm, capacity of injection cylinder 1 when injection piston 3 is retracted 1.4c
c, injection pressure of the injection cylinder 1 is 4900 kg / square centimeter. The inner diameter of the feeding pipe 5 is 3 mm and the length is 70 mm. The outer diameter of the measuring piston 4 is 10 mm, the volume of the measuring cylinder 2 is 3.5 cc when the measuring piston 4 is retracted, the discharge volume is 2.5 cc as the measuring piston 4 moves forward, and the injection pressure of the measuring cylinder 2 is 720 kg / square centimeter. The specific injection pressure performance and metering performance were as follows. <First mode> Maximum injection pressure 4900 kg / cm <2> Coating material injectable volume 0-1.4 cc Measurement unit 0.1 cc (based on the fact that the retreat position of the measurement piston can be controlled in units of 1 mm) <Second mode>> Maximum injection pressure 720 kg / square centimeter Coating material injectable volume 0-2.5 cc Weighing unit 0.1 cc (Based on the fact that the retracting position of the weighing piston can be controlled in 1 mm units)

[0020]

According to the present invention, since the measuring cylinder and the injection cylinder are integrated with the injector, the distance between the measuring cylinder and the injection cylinder is close and they are connected by a metal tube instead of a rubber hose. Therefore, the measured coating agent is accurately supplied to the injection cylinder without causing an error due to deformation of rubber, and even if the amount is 1 cc or less, the coating agent in an amount exactly as the measured value is applied from the injection cylinder to the mold at high pressure. Injection can be injected. Further, since the coating material conveyed to the injection cylinder is injected by the injection piston, the injection operation is direct, and the injection is started at the same time as the piston operation, and the responsiveness is good and accurate injection timing control is possible. Good results can be obtained in the required in-mold coating. It should be noted that when injecting a larger amount of coating material than the injection cylinder capacity, injection is performed by the operation of the measuring piston, but since the feed pipe connected to the measuring cylinder is a rigid body, there is no pressure deformation, and the injection piston An accurate injection amount and good responsiveness can be obtained similarly to the injection by. Moreover, since the coating agent flow passage in the injector has a flow passage structure without a series of hydrodynamic stagnation parts, it is not always necessary to incorporate a cooling mechanism, and it is possible to prevent the injector from becoming large.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a state in which an injection piston and a metering piston according to an embodiment of the present invention are advanced.

FIG. 2 is a partially enlarged cross-sectional view of a state in which the injection piston is moved forward and the metering piston is moved backward as well.

FIG. 3 is a partially enlarged cross-sectional view of a state in which the injection piston is also retracted and the metering piston is advanced, similarly.

FIG. 4 is a cross-sectional view showing an aspect of a groove of the measuring piston.

FIG. 5 is a cross-sectional view showing an aspect of a groove of the measuring cylinder.

FIG. 6 is a cross-sectional view showing an aspect in which grooves are provided on both the measuring cylinder and the measuring piston.

FIG. 7 is a sectional view of an example in which a gap is provided between a measuring cylinder and a measuring piston to form a flow path.

FIG. 8 is a schematic view showing a weighing state.

FIG. 9 is a schematic view showing a state in which the metering piston is also moved forward to inject the coating material into the injection cylinder.

FIG. 10 is a schematic view showing a state in which the injection piston is also advanced to inject the coating material into the mold.

FIG. 11 is a schematic view in the case of injecting a coating material, which is also larger than the volume of the injection cylinder.

FIG. 12 is a schematic view showing an apparatus of a conventional example.

FIG. 13 is a schematic diagram of a state where the on-off valve is also opened.

FIG. 14 is a schematic diagram of a state of injection in which the metering piston is also advanced.

FIG. 15 is a schematic diagram of a state in which the residual coating agent is extruded by advancing the injection piston in the same manner.

[Explanation of symbols]

 A1 injection part A2 metering part 1 injection cylinder 2 metering cylinder 3 injection piston 4 metering piston 5 feed pipe 6 supply pipe 7 check valve 8 outflow pipe 9 plunger 10 plunger 11 return path 12 pump 13 open space 14 open / close valve 15 gap 16 coating Agent 31 Mold 32 Molded product 33 Coating layer

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[Procedure amendment]

[Submission date] November 21, 1995

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

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FIG.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

[Fig. 2]

[Procedure 3]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

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[Figure 3]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location B29L 9:00 31:34 (72) Inventor Takeshi Fujishiro 5-6-2 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Sanryo Engineering Plastics Co., Ltd.Technical Center (72) Inventor Kenji Ota 878 Mitsubuchi Nishinomon, Komaki City, Aichi Prefecture Konami Plant, Dainippon Paint Co., Ltd. (72) Inventor Yukio Hayashi Sawatari, Kanagawa-ku, Yokohama, Kanagawa At No. 1 2 Tsubako Yokohama Sales Co., Ltd.

Claims (6)

[Claims] 1. A coating material injection piston for ejecting the coating material in the cylinder from a coating material injection opening is mounted in an injection cylinder having a coating material injection opening at its tip, and the coating material is measured in the injection cylinder. An injector for the in-mold coating method, to which a measuring cylinder is connected, a measuring piston is attached to the measuring cylinder, and the injection cylinder and the measuring cylinder are integrally formed. 2. A circumferential groove is formed in the peripheral wall of the injection cylinder or the injection piston, and an outlet for the coating agent is provided in the injection cylinder, and a return path for the coating agent is connected to the outlet. An axial flow path is formed between the measuring cylinder and the measuring piston, and when the injection piston advances, the groove formed in the circumferential direction of the peripheral wall of the injection cylinder or the injection piston communicates with the outflow port and the groove. The in-mold coating method according to claim 1, wherein the metering cylinder is in communication, and the coating material fed to the metering cylinder is configured to pass through the metering cylinder and the injection cylinder, flow out from the outlet, and circulate. Injector 3. When the injection piston is retracted, the circumferential groove formed in the injection cylinder or the injection piston is closed between the outlet and the circulation of the coating material is stopped. Injector for in-mold coating method 4. The injector for the in-mold coating method according to claim 3, wherein the metering cylinder and the injection cylinder are configured so as not to communicate with each other when the metering piston advances. 5. The injector for the in-mold coating method according to claim 1, wherein a check valve is incorporated in the coating material supply passage to the measuring cylinder. 6. A circumferential groove is formed on the peripheral wall of the injection cylinder or the injection piston, and a coating agent outlet is provided on the injection cylinder. When the injection piston is closed, the peripheral wall of the injection cylinder or the injection piston is closed. The groove formed in the circumferential direction communicates with the outflow port, and the groove communicates with the measuring cylinder,
An axial flow path is formed between the metering cylinder and the metering piston, and the coating material fed to the metering cylinder is configured so as to pass through the metering cylinder and the injection cylinder and flow out from the outlet. A molding material made of a thermoplastic resin or a thermosetting resin was provided in a molding die using an in-mold coater injector configured so that the measuring cylinder and the injection cylinder are not in communication when the piston is advanced. An in-mold coating method in which after molding in the cavity, the surface of the obtained molded product is coated with a predetermined amount of coating agent in the cavity, and (A) the coating agent does not stay in the coating agent flow path. A state in which the injection piston is arranged in the forward position and the measuring piston is arranged in the backward position while the coating material is continuously flown in the coating material flow path to measure a predetermined amount of the coating material. A step of molding a molding material made of a thermoplastic resin or a thermosetting resin in a cavity provided in a molding die, and (B) stopping the circulation of the coating material to prevent the flow of the coating material in the injector and in the peripheral coating material channel. A step of setting the internal pressure to 0 kgf / square centimeter-G; (C) a step of retracting the injection piston; and (D) advancing the metering piston to supply a predetermined amount of coating agent into the injection cylinder, or a predetermined amount of coating. The step of supplying the agent into the injection cylinder and injecting it onto the surface of the molded article in the cavity, and (E) advancing the injection piston to inject the coating agent supplied into the injection cylinder onto the surface of the molded article in the cavity. An in-mold coating method comprising a coating step.