JPH1148348A - Vibratory compression filling method and evacuation valve device used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a bridging phenomenon in a granule conveying pipe and a cavity from occurring by vertically pulsating a back pressure in a foam molding die and conveying a granule while causing the expansion and shrinkage of a foamed bead to fill the die with the foamed bead. SOLUTION: A foamed bead is packed into a foam molding die by vertically pulsating its back pressure and conveying the foamed bead while causing the expansion and shrinkage of the foamed bead. Consequently, the pulsation of the internal back pressure of a cavity occurs, resulting in the repeated volumetric change of the foamed bead synchronized to its pulsation and thus a bridging phenomenon hardly occurs. The pulsation width of the back pressure is accepted as adequate, provided that its difference in pressure is at such a low level as 0.2-2.0 kg/cm<2> . An evacuation valve device for controlling the back pressure is equipped with a reactivation valve 4 for adjusting air evacuation, a diaphragm valve 51 for converting a pressure signal 51a to a control signal 52a and an air operating four-way valve 52 for transferring a pressurized air 41a for ON/OFF operation control to a reactivating cylinder 41 for a reactivation valve 4 by a control signal from the diaphragm valve 51. This evacuation valve device is arranged in an evacuation path from the chamber of a molding machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a foam molding machine, in which foam beads, which are pre-pressurized raw materials, are fed into a mold cavity from a foam bead compression tank of a foam molding machine, filled and then reduced to atmospheric pressure or minus pressure. The present invention relates to a method for compressing and filling foam beads in a foam molding machine for expanding a foam bead by means of a foam molding machine and improving the degree of filling, and an improvement in an exhaust valve device used in the method.

[0002]

2. Description of the Related Art Conventionally, in a molding apparatus used for a foam molding method of a foam molded product made of expanded polystyrene resin or the like, first, as shown in an illustration of FIG. 3, a cavity 1 in which a foam product is filled and molded is formed. As shown, a male-type convex inside 11 and a female-type concave inside 12
Are arranged to face each other. The insides 11 and 12 are provided with countless vent holes so that the heating steam can pass therethrough. In addition, these inside 11, 1
On the back side of 2, to supply utilities such as steam,
Alternatively, chambers 13 and 14 for discharging are formed. In such a foam molding apparatus, expandable raw material beads preliminarily foamed (hereinafter simply referred to as foam beads)
After filling into the cavity 1, heating steam is introduced from the chambers 13 and 14, and the foam beads are heated and fused to produce a foam molded article having a predetermined shape.

[0003] In such a molding method, in order to fill the foamed beads into the cavity 1, foamed beads as a pre-foamed raw material are temporarily stored in a compression tank 2 as illustrated in FIG. In the molding process, the cavity 1 in the mold is passed through the granulating pipe 3 connected to the bottom.
Sent to.

[0004] In this case, the compression tank 2 is set at 0.1 to 5.0.
and pressurized to about kg / cm ^2, to provide a differential pressure between the compression tank 2 to the cavity 1 slightly reduced pressure, the inside diameter 25m
An airflow flowing from the supply tank 2 toward the cavity 1 is formed in the granule sending pipe 3 of about m. Then, along with the flow of the air current, foamed beads preliminarily foamed into a substantially spherical or dumpling shape having a diameter of 1 to 8 mmφ are fed into the cavity and filled. Note that a filler 31 is provided on the cavity 1 side of the granulation pipe 3, and pressurized air is introduced into the filler 31 to promote filling of the expanded beads.

After that, if the pressure in the cavity 1 is reduced to the atmospheric pressure, the expanded beads are reduced in pressure from the compressed state in the limited volume in the cavity 1, so that the beads expand and deform to fill the gap. At the same time, since the air between the beads is excluded, the advantage that the degree of filling is improved is obtained. Such a method is called a so-called compression filling method.

[0006] In such an apparatus for feeding foam beads, an intermittent supply device 21 is provided at the outlet of the supply tank 2 so that the foam beads do not cause a bridging phenomenon in the feed pipe to block the pipe. It is common to have. This intermittent supply device 21 makes a disk 22 provided with a plurality of opening holes 23 around it come into contact with an inlet opening 32 connected to the granulation pipe 3, as exemplified in FIGS. By rotating 22, the supply path to the inlet opening 32 is repeatedly opened, closed, opened, and closed, and the flow of the foamed beads is intermittently repeated with the flow of air. The intention is that even if the bridging phenomenon starts to occur somewhere, the bridging phenomenon will not be increased by the intermittent vibrations or shocks.

By the way, there are foamed beads made of polyolefin as a raw material in addition to polystyrene as a resin type of foamed beads. In the case of foamed beads made of this polyolefin, the structure is soft and the coefficient of friction is so high that it is sticky. Therefore, there is a problem that a bridging phenomenon easily occurs even in a slightly bent place in the granulation pipe 3.

Further, in the process of filling the cavity 1 with the foam beads, a bridging phenomenon may occur at a place where the foam beads are hard to go around such as a bent portion or a thin portion in the mold, and as a result, Insufficient filling may occur and insufficient molding may result in poor shape. The intermittent supply device 21 has not been able to achieve a sufficient effect against such insufficient filling.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to simultaneously solve the bridging phenomenon in the granulating pipe and the cavity in the compression filling method as described above. Novel method of vibrating and compressing foam beads, which can act on both the foam beads inside and the foam beads in the process of being filled in the cavity at the same time to reduce the occurrence of the bridging phenomenon, and the exhaust valve device used therefor I will provide a.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a vibration compression filling method of the present invention provides a back pressure having a predetermined pressure difference from a compression tank for storing expanded beads in a compressed state. A method for feeding and filling the expanded beads with the expanded beads, wherein the back pressure of the expanded mold is pulsated up and down, and the expanded beads are sent while expanding and contracting, and filled. It is characterized by the following. Vibration compression filling method.

In the vibration compression filling method of the present invention, the maximum value of the pulsating back pressure is set to be equal to the pressurizing pressure of the compression tank, and the feeding and filling of the expanded beads are performed intermittently. Can be embodied.

Further, an exhaust valve device used in the vibration compression-filling method of the present invention made to solve the above-mentioned problem is an exhaust valve device for controlling the back pressure of the foaming mold in the vibration compression-fill method. A return valve for adjusting exhaust gas, a diaphragm valve for converting a control signal by a pressure signal, and an air operated four-way for transmitting pressurized air for opening and closing control to the return valve by a control signal for the diaphragm valve. And a valve.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. First, the vibration compression filling method of the present invention will be described. A plastic foam bead such as polyolefin is stored in a compressed state of about 0.1 to 5.0 kg / cm ^{2 in} a compressed state from a compression tank 2 (FIG. 3) having a predetermined pressure difference. For example, the compression filling method is based on sending and filling the foam beads into the foam molding die of the cavity 1 (FIG. 3) to which a back pressure is applied with a pressure difference of about 0.2 kg / cm ² . Things. The pressurized pressure of the compression tank 2 is
Preferably it is 0.3 to 3.0 kg / cm ² , more preferably 0.3 to 3.0 kg / cm ² .
The range of 3 to 1.5 kg / cm ² is preferable because the load on the device can be reduced. The back pressure can be adjusted to a predetermined value by controlling the amount of exhaust by an exhaust valve device (not shown) arranged in an exhaust path from the chambers 13 and 14 of the molding machine.

Focusing on the state of the expanded beads, conventionally, expanded beads having a compressed volume corresponding to the pressurized state in the compression tank 2 are filled in the cavity 1 and slightly depressurized. Therefore, although the volume slightly expanded, the effect of the change in volume during the granulation process and the filling process with the granulation pipe was little or very little.

However, the features of the present invention are as follows:
The point is that the back pressure of the foam molding die is pulsated up and down, and the foam beads are sent and filled while expanding and contracting. That is, in the present invention, the pressure value a of the compression tank does not change in both the granulating process and the filling process as illustrated in FIG. 1, but the back pressure b in the cavity pulsates. The volume change is repeated in synchronization. As a result, the gap between the foamed beads is promoted, and a remarkable advantage that a bridging phenomenon that sticks to each other is hardly caused is obtained. In this case, the pulsation width of the pressure value of the back pressure b to be pulsated can be appropriately set according to the situation.
Within the range of ^{2 to} 2.0 kg / cm ² , or 0.2 to
A low level pressure difference, in the range of 0.8 kg / cm ² suffices.

In this vibration compression filling method, the pressure value of the pulsating back pressure b may be an appropriate value between a preset pressure value a of the compression tank and the atmospheric pressure. It is preferable that the repeated maximum value b1 of the back pressure b is set to be equal to the set pressure value a of the compression tank.

In this case, the feeding and filling of the expanded beads are interrupted when the back pressure b becomes maximum, and the feeding and filling are resumed and proceed when the back pressure is lowered. ,
Granulation and filling can be performed intermittently. And
As a result, the conventional intermittent supply device 2 described above can be used.
1 (FIG. 3) can be expected, and according to the present invention, the advantage that the intermittent supply device 21 can be omitted can be obtained. The period of the pulsation of the present invention is preferably 2 to 5 times, preferably about 3 times per second, in order to effectively generate vibration due to the pulsation.

Next, the exhaust valve device of the present invention will be described. This exhaust valve device is an exhaust valve device that controls the back pressure of the foaming mold in the vibration compression filling method,
As illustrated in FIG. 2, a return valve 4 for adjusting exhaust gas,
A diaphragm valve 51 that converts a pressure signal 51a into a control signal 52a, and an air operated four-way valve that transmits pressurized air 41a for opening and closing control to a reversing cylinder 41 of the reversing valve 4 according to a control signal 52a of the diaphragm valve 51. 52.

A general exhaust valve device often employs a diaphragm pressure adjusting method using a three-way valve or a single-acting valve 6 based on a simple direct-acting method illustrated in FIG. 5, in which the control pressure changes slowly. However, it is not suitable when the control pressure is pulsated in a short period as in the case of the present invention, and the return valve 4 having the return cylinder 41 of the present invention is applied. As a result, a predetermined pressure-time curve can be faithfully realized, and high control accuracy can be obtained.

[0020]

The method of vibrating and compressing expanded beads according to the present invention is configured as described above, and thus the expanded beads in the feeding pipe and the expanded foam in the process of filling the cavity are formed. By acting on both of the beads at the same time, it is possible to prevent the bridging phenomenon, and it is also possible to omit the intermittent supply device. Further, according to the exhaust valve device used in the vibration compression filling method, there is an excellent effect that preferable high control accuracy can be obtained. Therefore, the present invention has a very large industrial value as a vibration compression filling method of foam beads and its exhaust valve device which has solved the conventional problems.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between tank pressure and back pressure in the present invention.

FIG. 2 is a flow chart of a main part of the exhaust valve device of the present invention.

FIG. 3 is an illustration for explaining a conventional foaming bead feeding and filling operation.

FIG. 4 is a main part plan view showing a disk of a conventional intermittent supply device.

FIG. 5 is a flowchart of a main part of a conventional single-acting valve device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity 2 Compression tank 3 Granulation pipe 4 Release valve 21 Intermittent supply device 51 Diaphragm valve 52 Air operated four-way valve

Claims (3)

[Claims] 1. A method for feeding foam beads into a foaming mold to which a back pressure of a predetermined pressure difference is applied from a compression tank storing foam beads in a pressurized and compressed state, wherein the foam beads are filled. A vibratory compression filling method characterized by pulsating the back pressure of a molding die up and down, sending and filling the expanded beads while expanding and contracting the beads. 2. The vibration compression according to claim 1, wherein the maximum value of the pulsating back pressure is set to be equal to the pressure of the compression tank so that the foaming beads are intermittently fed and filled. Filling method. 3. An exhaust valve device for controlling a back pressure of a foaming mold in the vibration compression / filling method according to claim 1 or 2, wherein a return valve for adjusting exhaust and a control signal by a pressure signal. An exhaust valve device comprising: a diaphragm valve for converting; and an air operated four-way valve for transmitting pressurized air for opening / closing control to the return valve in accordance with a control signal of the diaphragm valve.