37 is not necessarily required, and the gas supply device 5 may be configured only by the high pressure regulating unit 36.

The gas supply device 5 can be variously modified. FIG. 3 shows a gas supply device 5B according to a second embodiment. Parts and components similar to those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. An injection device 3B according to the embodiment is provided with two gas introduction ports, that is, first and second gas introduction ports 30a and 30b. The gas supply device 5B according to the second embodiment introduces a gas into the first and second gas introduction ports 30a and 30b.

As in the first embodiment, the gas supply device 5B according to the second embodiment is also provided with the high pressure regulating unit 36 and the low pressure regulating unit 37, but these are completely separated into two systems from upstream. That is, gas cylinders 33a and 33b are separately provided corresponding to the high pressure regulating unit 36 and the low pressure regulating unit 37, and the respective supply source pressure gauges 47a and 47b are provided. A pipeline from the high pressure regulating unit 36 and a pipeline from the low pressure regulating unit 37 are connected to the first gas introduction port 30a and the second gas introduction port 30b, respectively.

However, a bypass pipe 52 is provided midway between the pipeline from the high pressure regulating unit 36 and the pipeline from the low pressure regulating unit 37, and a bypass on-off valve 53 is provided in the bypass pipe 52. A first on-off valve 54 is provided downstream of the bypass pipe 52 in the pipeline from the high pressure regulating unit 36, and a second on-off valve 55 is provided downstream of the bypass pipe 52 in the pipeline from the low pressure regulating unit 37.

The gas supply device 5B according to the second embodiment can be operated by various methods. When the gas supply device 5B is operated with the bypass on-off valve 53 normally closed in the molding cycle, a high pressure gas is normally introduced into the heating cylinder 18 only from the first gas introduction port 30a, and a low pressure gas is normally introduced into the heating cylinder 18 only from the second gas introduction port 30b. In the metering process 61, the controller 31 opens the high pressure-side on-off valve 44 and the first on-off valve 54 to supply a high pressure gas. In other processes, the controller 31 closes the on-off valves 44 and 54 and opens the low pressure-side on-off valve 45 and the second on-off valve 55 to supply a low pressure gas.

When the gas supply device 5B is operated with the bypass on-off valve 53 normally open, a high pressure gas and a low pressure gas can be supplied to both the first and second gas introduction ports 30a and 30b. That is, when the high pressure-side on-off valve 44 is opened and the low pressure-side on-off valve 45 is closed, a high pressure gas is supplied, and when the high pressure-side on-off valve 44 is closed and the low pressure-side on-off valve 45 is opened, a low pressure gas is supplied. Depending on an opened or closed state of the first and second on-off valves 54 and 55, the gas can be introduced into both of the first and second gas introduction ports 30a and 30b at the same time or introduced into any one of the first and second gas introduction ports 30a and 30b. In the injection molding machine 1, since the screw 19 moves in an axial direction during the metering process, the gas introduction ports 30a and 30b may deviate from the starvation section 24 depending on the configuration and position of the screw 19 and the arrangement of the gas introduction ports 30a and 30b. Even in such a case, by arranging the gas introduction ports 30a and 30b apart from each other in the axial direction and selecting one of the first and second on-off valves 54 and 55 to be opened according to the screw position, it is possible to continue to supply the gas to an appropriate position of the starvation section 24.

In the present embodiment, various modifications are possible. Instead of using the bypass on-off valve 53 in a normally opened state, the bypass on-off valve 53 may be eliminated and the bypass pipe 52 may be used. Or, instead of using the bypass on-off valve 53 in a normally closed state, the bypass pipe 52 may be eliminated. In the case the bypass pipe 52 is eliminated, the first and second on-off valves 54 and 55 may be eliminated.

FIG. 4 shows a gas supply device 5C according to a third embodiment. Parts and components similar to those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the gas supply device 5C according to the third embodiment, the high pressure regulating unit 36 includes a syringe 56 driven by a high pressure piston, and is connected downstream of the low pressure regulating unit 37. The syringe 56 can store a sufficient amount of low pressure gas, and when the piston is driven, the syringe 56 is compressed to supply a high pressure gas. That is, the syringe 56 is a pressure increasing mechanism for increasing a pressure of a gas. Therefore, in the metering process 61, the controller 31 may supply the high pressure gas by driving the syringe 56 to increase the pressure of the gas after closing the low pressure-side on-off valve 45.

The gas pressure control means of the pressure increasing mechanism is not particularly limited, and for example, the pressure may be calculated and controlled from a driving force of the piston and a cross-sectional area of the piston, or the pressure may be feedback-controlled by attaching a pressure gauge downstream of the piston.

FIG. 5 shows a gas supply device SD according to a fourth embodiment. Parts and components similar to those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. The gas supply device SD according to the fourth embodiment includes a nitrogen gas generator 80 as a gas supply source and a booster pump 81 for compressing a gas. A pressure reducing valve 83 with an automatic pressure regulating function is provided in a pipeline from the gas supply source. The pressure reducing valve 83 can change a set pressure according to a command from the controller 31 (see FIG. 1). A pressure gauge 84, a check valve 85, and an on-off valve 86 are provided downstream of the pressure reducing valve 83, and are connected to the gas introduction port 30. In the metering process, the gas is supplied at a high pressure in the pressure reducing valve 83 with an automatic pressure regulating function, and in other processes, the gas is supplied at a low pressure.

When the operation is performed by the gas supply device 5C according to the third embodiment or the gas supply device SD according to the fourth embodiment, it is also possible to supply the gas with three or more stages of pressure such as high pressure, medium pressure, and low pressure. FIG. 8 shows a change in each data in a foam molding method in which a gas is supplied by changing a gas pressure in three stages. That is, a pressure increasing period includes a pressure increasing period 71a in which the gas pressure 68 is a medium pressure, and a pressure increasing period 71b in which the gas pressure 68 is a high pressure. The gas pressure 68 is switched from the low pressure to the medium pressure at a timing 69a prior to the metering process 61. Next, after the metering process 61 is started, the pressure of the gas is switched from the medium pressure to the high pressure at a timing 69b. When the high pressure is switched to the low pressure at a timing denoted by reference numeral 70 slightly before the metering process 61 is completed, the gas pressure 68 thereafter gradually changes to the low pressure. Further, the gas pressure 68 may be smoothly increased or decreased. That is, the pressure may be gradually increased during the metering process 61. In the first and second embodiments, a modification is also possible in which a pressure increasing mechanism is provided in the high pressure regulating unit 36, and the pressure is adjusted in three or more stages during the metering process 61.

The injection molding machine 1 according to the present embodiment and the foam molding method according to the present embodiment can be variously modified. For example, the pipeline from the gas supply device 5 is described as being directly connected to the gas introduction port 30, but a small volume buffer may be provided in the vicinity of the gas introduction port 30. The buffer serves as a cushion to prevent a rapid change in gas pressure. However, in order to obtain a maximum effect in the present invention, it is desirable to provide the buffer between the high pressure-side check valve 41 and the high pressure-side on-off valve 44 of the high pressure regulating unit 36. This is because, if the buffer is provided downstream of the high pressure-side on-off valve 44, that is, in the vicinity of the gas introduction port 30, when the pressure is switched to a high pressure or a low pressure, it takes time to switch the pressure due to a buffering action of the buffer. On the other hand, when the buffer is provided in the high pressure regulating unit 36, it is possible to prevent a pressure decrease in the high pressure regulating unit 36 immediately after the high pressure-side on-off valve 44 is opened and the pressure is switched from the low pressure to the high pressure, and to rapidly increase the pressure in the heating cylinder 18.

For example, in the gas supply device 5A according to the first embodiment, as described above, the low pressure-side check valve 42 may be omitted, or the check valves 41 and 42 may be omitted instead of omitting the low pressure-side check valve 42.

The gas supply device 5A shown in FIG. 2 and the gas supply device 5C shown in FIG. 4 may be combined with the injection device 3B having a configuration in which two gas introduction ports are provided, as shown in FIG. 3. In this case, the pipe from the gas supply device is branched into two to reach each of the two gas introduction ports. In the gas supply device 5B shown in FIG. 3, the bypass on-off valve 53 may not be provided.

In the foam molding method, it has been described that the pressure of the gas is increased to a high pressure prior to the metering process 61, but the pressure of the gas may be increased simultaneously with the start of the metering process 61 or with a delay from the start of the metering process 61. The pressure increasing period 71 in which the pressure of the gas increases in the molding cycle may at least partially overlap with the metering process 61. In the processes other than the metering process 61, it has been described that the gas is set to a low pressure, that is, the pressure of the gas is reduced, but the supply of the gas may be stopped. When the pressure is excessively decreased, the gas dissolved in the resin during the pressure increasing period 71 in the heating cylinder 18 is separated and starts to foam, and thus the pressure of the gas needs to be maintained to such an extent that foaming does not occur.

Although the invention made by the present inventors is specifically described based on the embodiment, it is needless to say that the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the scope of the invention. A plurality of examples described above may be implemented in combination as appropriate.

Here, features of the embodiments of the gas supply device, the injection molding machine, and the foam molding method according to the present invention described above will be briefly summarized and listed [1] to [26] below:

- [1]

A gas supply device (5) provided in an injection device (3), the injection device including a heating cylinder (18) having a gas introduction port (30) and a screw (19) provided to be drivable in the heating cylinder (18), the gas supply device (5) including:

- a gas supply source (102); and
- a gas pressure regulating unit (34) configured to regulate a pressure of a gas from the gas supply source (102) and supply the gas to the gas introduction port (30),
- in which the gas pressure regulating unit (34) is configured to change a gas pressure in a molding cycle and to cause a pressure increasing period in which the gas pressure increases to at least partially overlap with a metering process.
- [2]

The gas supply device (5) according to [1], in which the gas pressure regulating unit (34) is configured to reduce the gas pressure at a specified time before, at the time of, or after a specified time from completion of the metering process of the molding cycle.

- [3]

The gas supply device (5) according to [1] or [2], in which the gas pressure regulating unit (