Patent Application
20230278270
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2022-031201 filed on Mar. 1, 2022, the contents of which are incorporated herein by reference.
The present disclosure relates to an injection molding machine for foam molding for molding a foam molded product by injecting an inert gas into an injection material, and a method for molding the foam molded product.
An injection molding machine for foam molding for obtaining a foam molded product using a physical foaming agent, that is, a gas, is generally configured as follows, for example, as disclosed in JP2014-200937A. That is, an injection device of the injection molding machine includes a heating cylinder and a screw. An inside of the heating cylinder is divided into a plurality of sections according to a shape of the screw. The inside of the heating cylinder includes, from upstream to downstream, a first compression and measurement section, a starvation section, and a second compression and measurement section. The heating cylinder is provided with a gas injection port so as to correspond to the starvation section. The gas is supplied by a gas supply device including a gas cylinder or the like. A gas flow path of the gas supply device is coupled to the gas injection port.
A resin is fed from upstream to downstream in the heating cylinder by the screw and is melted. The resin is kneaded in the first compression and measurement section. Then, a pressure of the resin decreases in the starvation section, and a gas such as nitrogen and carbon dioxide is injected. The resin into which the gas is injected is kneaded and compressed in the second compression and measurement section. The resin is measured and is injected into a mold to obtain a foam molded product.
In the injection molding machine for foam molding, a so-called gas leakage may occur in which, after a measuring step is completed, a part of gas injected into the heating cylinder flows back through the heating cylinder and leaks from upstream of the heating cylinder.
Other problems and novel features will become apparent from description of the present description and the accompanying drawings.
Illustrative aspects of the present disclosure relate to an injection molding machine having a following configuration. That is, the injection molding machine includes: a heating cylinder provided with a gas injection port; a screw; a gas supply device configured to supply a gas to the gas injection port; and a control device. A valve mechanism is provided in a gas flow path of the gas supply device. The control device is configured to control the valve mechanism to be closed at least once in a molding cycle, and to be kept in an open state at least in a measuring step.
According to the present disclosure, it is possible to prevent gas leakage in which the gas flows backward in the heating cylinder by opening and closing the gas flow path to the gas injection port.
Hereinafter, specific illustrative embodiments will be described in detail with reference to the drawings. The present disclosure is not limited to the following illustrative embodiments. In order to clarify description, following description and drawings are simplified as appropriate. In the drawings, the same elements are denoted by the same reference signs, and repeated description thereof is omitted as necessary. Hatching may be omitted to avoid complicating the drawings.
The present illustrative embodiment will be described.
{Injection Molding Machine}
As shown in
{Injection Device}
The injection device 3 according to the present illustrative embodiment is supplied with a gas by the gas supply device 5 (which will be described later), and a resin into which the gas is kneaded and mixed, that is, a resin containing a physical foaming agent is measured. Therefore, when the mixture is injected, a foam molded product is obtained. That is, the injection device 3 for foam molding is provided.
The injection device 3 includes a heating cylinder 17, a screw 18 housed in the heating cylinder 17 as shown in
As shown in
A resin pressure sensor 30 is embedded in the heating cylinder 17 in association with the gas injection port 28. That is, the resin pressure sensor 30 is embedded in the vicinity of the gas injection port 28 and is configured to detect a resin pressure in the starvation section 26. The detected resin pressure is sent to the controller 4.
{Gas Supply Device}
The gas supply device 5 according to the present illustrative embodiment includes a gas cylinder 32 as a gas supply source, a pressure reducing valve 34, and an on-off valve 35. A primary gas pipe 36 is coupled to the gas cylinder 32, and a relatively high-pressure primary gas is supplied to the primary gas pipe 36. The pressure reducing valve 34 is coupled between the primary gas pipe 36 and the secondary gas pipe 37. The pressure reducing valve 34 is configured to reduce a pressure of the gas having a primary pressure to a secondary pressure suitable for supplying the gas to the resin. The on-off valve 35 is provided in the secondary gas pipe 37. The on-off valve 35 is coupled to the gas injection port 28. The on-off valve 35 is configured to open and close a gas flow path of the secondary gas pipe 37. When the gas flow path is opened, the gas having the secondary pressure is supplied from the gas injection port 28 into the heating cylinder 17. When the gas flow path is closed, the supply of the gas is stopped.
In the gas supply device 5, a gas pressure gauge 39 is provided in the secondary gas pipe 37 and is configured to detect the secondary pressure of the gas. That is, the pressure of the gas supplied from the gas injection port 28 is substantially detected. The gas pressure gauge 39 and the on-off valve 35 are coupled to the controller 4. The secondary pressure is transmitted to the controller 4, and the controller 4 is configured to control opening and closing of the on-off valve 35. As will be described next, in the present illustrative embodiment, the on-off valve 35 is controlled so as to be closed at least once in a molding cycle and to be in an open state in a measuring step.
{Method for Molding Foam Molded Product}
A method for molding a foam molded product, which is performed by the injection molding machine 1 according to the present illustrative embodiment, will be described. In
In the molding cycle performed in the injection molding machine 1, a mold clamping step is first performed. That is, the mold clamping device 2 (see
A cooling step is performed to wait for solidification of the resin filled in the molds 13 and 14. At the same time as start of the cooling step or after the cooling step, the measuring step is performed. That is, the screw 18 is rotated to melt the resin and to perform a measurement. At this time, since the gas is supplied from the gas injection port 28 (see
Next, control over the on-off valve 35 of the gas supply device 5 will be described. The on-off valve 35 is operated in synchronization with the molding cycle of the injection molding machine 1 described above. Specifically, as shown in
When the on-off valve 35 is opened, the gas is inevitably supplied from the gas injection port 28 (see
{Other Illustrative embodiments of Method for Molding Foam Molded Product}
Various modifications can be made to the method for molding a foam molded product. For example, a timing at which the on-off valve 35 is opened has been described as being earlier than the measuring step by the specified preceding time. However, a timing at which the on-off valve 35 is opened may be used as a start timing of the measuring step. A timing at which the on-off valve 35 is closed has been described as being a timing delayed by the specified delay time from completion of the measuring step. However, the on-off valve 35 may be closed at a timing of the completion of the measuring step. Further, the timings of opening and closing the on-off valve 35 may be synchronized with the steps themselves in the molding cycle.
{Method for Determining Specified Delay Time, and the Like}
The specified preceding time and the specified delay time have been described as being set in advance in the controller 4 by an engineer. These times or the steps synchronized with the opening and closing of the on-off valve 35 may be freely determined by an engineer, or may be determined by preliminary preparation in which the molding cycle is repeated in a state where the on-off valve 35 is opened. This will be described. In the preliminary preparation, in the injection molding machine 1 according to the present illustrative embodiment shown in
Here, an appropriate range of the gas pressure is considered.
On the other hand, it can be seen that the gas pressure does not increase so much in the injecting step and the pressure holding step. That is, even when the on-off valve 35 (see
As has been described above, the timings of opening and closing the on-off valve 35 and the step synchronized with the opening and closing of the on-off valve 35 can be determined based on a fluctuation in the gas pressure in the molding cycle. Alternatively, they may be determined based on a fluctuation in the resin pressure. For example, in
Incidentally, the graph of the gas pressure 41 and the resin pressure 42 shown in
{Injection Molding Machine According to Second Illustrative Embodiment}
In the above description, it is assumed that the timing at which the on-off valve 35 is closed is after a specified delay time from the completion of the measuring step, or is synchronized with steps such as the measuring step and the cooling step. However, the on-off valve 35 may be closed by determining a timing for each molding cycle based on the gas pressure measured by the gas pressure gauge 39 or based on the resin pressure measured by the resin pressure sensor 30.
In the injection molding machine 1A according to the second illustrative embodiment, three setting values are stored in a controller 4A. That is, an appropriate gas pressure range, an appropriate resin pressure range, and a specified holding time are stored. The injection molding machine 1A according to the second illustrative embodiment can determine a closing timing of the on-off valve 35 from two methods. A first method is a method of determination based on the gas pressure. When the measuring step is completed in the molding cycle, the controller 4A monitors the gas pressure detected by the gas pressure gauge 39. When the gas pressure reaches the appropriate gas pressure range, the on-off valve 35 is closed. Alternatively, the on-off valve 35 is closed when the gas pressure reaches the appropriate gas pressure range and when the specified holding time elapses.
A second method is a method of determination based on the resin pressure. When the measuring step is completed in the molding cycle, the controller 4A monitors the resin pressure detected by the resin pressure sensor 30. When the resin pressure reaches the appropriate resin pressure range, the on-off valve 35 is closed. Alternatively, the on-off valve 35 is closed when the resin pressure reaches the appropriate resin pressure range and when the specified holding time elapses.
The timing at which the on-off valve 35 is opened has been explained as being, for example, earlier than the start of the measuring step by the specified preceding time. The specified preceding time may be adjusted for each molding cycle. For example, the gas pressure or the resin pressure is detected at the start timing of the measuring step, and when the gas pressure or the resin pressure deviates from the appropriate range, the specified preceding time may be adjusted based on a magnitude of the deviation. For example, when the gas pressure does not reach the appropriate range at the start of the measuring step, the specified preceding time may be adjusted to be long in next and subsequent molding cycles so that the gas pressure falls within the appropriate range.
{Injection Molding Machine According to Third Illustrative Embodiment}
In the injection molding machine 1 according to the present illustrative embodiment, the apparatus itself may be modified.
Although the invention made by the present inventors is specifically described based on the illustrative embodiments, it is needless to say that the present invention is not limited to the illustrative embodiments described above, and various modifications can be made without departing from the scope of the invention. For example, although the supply of the gas is controlled by the on-off valve 35 or the injection valve 51, the check valve may be controlled by a pressure difference between upstream and downstream of the check valve. In
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-031201 | Mar 2022 | JP | national |
