JP3706180B2 - Method and apparatus for molding foamed plastic products - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for molding a foamed plastic product that can supply heated steam for foam molding in a short period of time and can perform stable and efficient production.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a method for molding a foamed plastic product such as a packaging box material, a method of heating and foaming a bead foaming material filled in a mold with heating steam supplied through a steam valve is widely known. In this case, the supply steam pressure is usually adjusted by adjusting the opening of the steam valve by feeding back the pressure value detected in the primary side of the drain discharge valve or in the molding chamber.
[0003]
However, since the drain discharge valve or molding chamber for measuring pressure is located far from the steam valve, the responsiveness is poor. Even if the steam valve is controlled based on the fed back signal, the inside of the mold is already predetermined. It is necessary to adjust the pressure value by lowering the pressure value again, and after reaching this pressure value, the pressure value can be reached only after many times. There was a problem that it took. In addition, the waveform that feeds back the pressure value detected by the drain discharge valve or molding chamber is wavy, so it is difficult to control accurately in a short time and it is necessary to change the steam supply amount quickly. However, there was a problem that it was impossible to adjust to a stable state.
[0004]
[Problems to be solved by the invention]
The present invention solves the conventional problems as described above, and provides a foamed plastic product capable of stable and efficient production by supplying heated steam for foam molding by adjusting the pressure in a short time by feedback control. The present invention has been completed for the purpose of providing a molding method and apparatus.
[0005]
[Means for Solving the Problems]
The present invention, which has been made to solve the above-mentioned problems, is a method for molding a foamed plastic product in which a foamed bead raw material filled in a mold is heated and heated by a steam supplied through a steam valve. Steam is supplied while feedback-controlling the steam valve based on the pressure value detected by the first detector provided in the inlet side of the drain discharge valve or in the molding chamber until the first set pressure value, From the primary set pressure value to the final set pressure value, primary steam is supplied so that the steam valve is feedback-controlled based on the pressure value detected by the second detector provided on the outlet side of the steam valve. A first aspect of the present invention is a method for molding a foamed plastic product, wherein the control method using the steam valve is switched before and after a set pressure value. A molding apparatus for carrying out the method for molding a foamed plastic product according to the first aspect of the invention, wherein the bead foaming material filled in the mold is heated by the heating steam supplied through the steam valve (2). In the molding equipment for foamed plastic products to be foamed, the steam valve (2) is controlled based on the signal from the first detector (5) provided on the inlet side of the drain discharge valve (3) or in the molding chamber (4). A first feedback circuit (6) to be controlled is provided, and steam is generated based on a signal from a second detector (7) provided on the outlet side of the steam valve (2) separately from the first feedback circuit (6). A second feedback circuit (8) for controlling the valve (2) is provided to switch the first feedback circuit (6) and the second feedback circuit (8) before and after the first set pressure value. 9) It is characterized by being switchable by The molding apparatus of the foamed plastic product is intended to be the second invention.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In the figure, 1 is a molding die comprising a pair of movable molds that can be contacted and separated, and a stationary mold, 2 is a steam valve for supplying steam for heating into the molding mold 1, 3 is a drain discharge valve, and 4 is a molding. The above-described configuration is basically the same as that of a conventional molding apparatus for this kind of foamed plastic product.
[0007]
In the present invention, a first detector 5 for measuring the vapor pressure supplied into the drain discharge valve 3 or the molding chamber 4 is provided, and a signal output from the first detector 5 is provided. Is provided with a first feedback circuit 6 for controlling the steam valve 2. On the other hand, a second detector 7 is provided on the outlet side of the steam valve 2 separately from the first feedback circuit 6, and the steam valve 2 is controlled based on a signal output from the second detector 7. A second feedback circuit 8 is provided. The first feedback circuit 6 and the second feedback circuit 8 are configured to be switchable by a switching valve 9 composed of a three-way valve.
[0008]
Reference numeral 10 denotes a diaphragm for controlling the steam valve 2 by balancing the air pressure signal for setting the pressure and the fed back signal.
In the above example, a three-way valve is used as the switching valve 9. However, as shown in FIG. 2, when the orifice 11 for restricting the flow rate is provided in the first feedback circuit 6, the three-way valve is used. Alternatively, a simple on / off type valve may be used.
[0009]
Next, the molding process of the present invention will be described. The conventional foaming plastic product is formed by heating and foaming the bead foaming material filled in the mold 1 with the steam for heating supplied through the steam valve 2. It is basically the same as the method.
In the present invention, at the beginning of molding, the first feedback circuit 6 performs the first set pressure value (based on the pressure value detected by the drain detector 3 or the first detector 5 provided in the molding chamber 4. Steam is supplied while performing feedback control up to P1), then the switching valve 9 is switched, and based on the pressure value detected by the second detector 7 provided on the outlet side of the steam valve 2, the second feedback circuit 8 Steam is supplied while performing feedback control up to the final set pressure value (P2).
[0010]
In this case, as shown in FIG. 3, the first set pressure value (P1) is set to a value that is, for example, about 20% smaller than the final set pressure value (P2), and from the beginning of molding to T1 time. The heating steam is supplied in a large amount by the control of the first feedback circuit 6 and then is quickly converged to the final set pressure value by the control of the second feedback circuit 8 until the time T2. This is based on the characteristic that the pressure value detected by the second detector 7 provided on the outlet side of the steam valve 2 is less wavy and can be delicately controlled stably. The value can be appropriately selected according to heating conditions based on empirical rules.
In the present invention, the convergence to the final set pressure value can be performed quickly and accurately compared to the case where feedback control is performed by taking a signal only from the conventional drain discharge valve (see the broken line in the graph), and the efficiency is improved. Production can be achieved.
[0011]
【The invention's effect】
As apparent from the above description, the first invention, the heating steam for foam molding was fed by regulating the short time by switching the control method by the steam valve before and after the primary set pressure value This is a method for molding foamed plastic products that can be stably and efficiently produced. On the other hand, the second invention can implement the method of the first invention with simple equipment, as well as assembly work and maintenance work. Is a molding apparatus that can be easily performed.
Therefore, the present invention contributes greatly to the development of the industry as a molding method and apparatus for foamed plastic products that eliminates the conventional problems.
[Brief description of the drawings]
FIG. 1 is a schematic view of piping showing an embodiment of the present invention.
FIG. 2 is a schematic view of piping showing another embodiment.
FIG. 3 is a graph showing a pressure regulating process of the steam valve.
[Explanation of symbols]
2 Steam valve 3 Drain discharge valve 4 Molding chamber 5 First detector 6 First feedback circuit 7 Second detector 8 Second feedback circuit 9 Switching valve

Claims (2)

In a method for molding a foamed plastic product in which a bead foaming material filled in a mold is heated with steam for heating supplied through a steam valve , the inlet side of the drain discharge valve from the initial molding to the first set pressure value. , or first on the basis of the pressure value detected by the detector to supply steam while feedback controlling the steam valve, then the steam to a final set pressure value from the primary set pressure value provided in the molding chamber The control method by the steam valve is switched before and after the first set pressure value so as to supply steam while performing feedback control of the steam valve based on the pressure value detected by the second detector provided on the outlet side of the valve. A method for molding a foamed plastic product. A molding apparatus for performing the method for molding a foamed plastic product according to claim 1, wherein the foamed foam material is heated and foamed by heating steam supplied through a steam valve (2). In the molding apparatus for foamed plastic products, the steam valve (2) is controlled based on the signal from the first detector (5) provided on the inlet side of the drain discharge valve (3) or in the molding chamber (4). 1 and a steam valve (2) based on the signal of the second detector (7) provided on the outlet side of the steam valve (2) separately from the first feedback circuit (6). ) Is provided to control the first feedback circuit (6) and the second feedback circuit (8) before and after the first set pressure value by a switching valve (9). Foam plastic characterized by being freely switchable Molding apparatus of tick products.

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