JP2808053B2 - Feedback-type foam molding method and foam molding system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam molding method and a foam molding method in which foaming thermoplastic resin particles as a raw material are pre-foamed and then foam-molded. The present invention relates to a feedback-type foam molding method and a foam molding system for controlling a basis weight by performing the method.

[0002]

2. Description of the Related Art Conventionally, in the field of foam molding, a predetermined amount of foamable thermoplastic resin particles is used as a raw material and heated and expanded in a container with a heating medium such as steam to pre-expand the resulting pre-expanded particles. After being appropriately cured, the mixture is filled in a foam molding machine and subjected to foam molding.

[0003] The pre-expansion ratio of the pre-expanded particles has a great influence on the quality of a foam molded article to be obtained later. Therefore, the pre-expansion ratio must be maintained at an optimum value. However, in the prefoaming apparatus, since the foaming ratio varies depending on various conditions such as temperature rise, the prefoaming ratio always fluctuates even under the prefoaming conditions set in advance to obtain the optimal prefoaming ratio. At present, the basis weight fluctuates due to this, and the quality of the obtained foamed molded product is uneven.

[0004]

The problem to be solved by the present invention is to control the basis weight by always using the pre-expanded particles having the optimum pre-expansion ratio, and to obtain a foam molded product with less variation in quality. It is to provide a foam molding method and a system thereof.

[0005]

Thus, according to the invention of claim 1 of the present application, "the raw expandable thermoplastic resin particles are pre-expanded, and the obtained pre-expanded particles are subjected to foam molding to obtain a predetermined foamed thermoplastic resin particle. A foam molding method for molding into a foam molded article,
The weight of the foamed molded article is measured, and based on the specific gravity of the foamed molded article obtained from the measured value, good or bad of the basis weight is determined. In the case of a defective, the specific gravity of the pre-expanded particles is changed by changing the preliminary expansion ratio. And a feedback-type foam molding method for controlling a foamed product having an appropriate basis weight.

The method of the present invention is characterized in that the basis weight is managed by feedback controlling the pre-expansion ratio using the weight of a so-called foam molded article as a parameter. The fact that the weight of the foam molded article molded into a constant shape by the foam molding machine (3) fluctuates means that the weight per unit area fluctuates. This change in the basis weight is caused by a change in the weight of the pre-expanded particles to be filled in the foaming molding machine (3), which indicates that the specific gravity of the pre-expanded particles is fluctuating. The specific gravity of the pre-expanded particles is due to the expansion ratio during pre-expansion. As an example, if the pre-expansion ratio is small, the specific gravity of the pre-expanded particles becomes large, whereby the volume becomes small, so that the weight per unit area becomes large, and the expansion ratio during foam molding is suppressed, so that the specific gravity of the foam molded article becomes large. That is, the specific gravity of the expanded molded article is in a relationship proportional to the specific gravity of the pre-expanded particles, and by measuring the weight of the expanded molded article, it is possible to check the specific gravity of the pre-expanded particles and adjust the pre-expansion ratio. it can.

[0007] In the method of the present invention, by setting in advance the appropriate weight (or specific gravity) range of the foam molded article with respect to the appropriate basis weight and the optimal range of the corresponding pre-expansion ratio, the foam molding is performed. The preliminary expansion ratio can be feedback-controlled based on the measured weight value of the product.

According to claim 2 of the present application, a pre-expansion device (21) for pre-expanding raw material expandable thermoplastic resin particles is provided as an apparatus for performing the method of the present invention. (3) for foaming the pre-expanded particles obtained in (1) by heating and foaming into foamed articles, and a transfer device (8) for sequentially transporting the foamed articles obtained by the foaming machine (3) to predetermined locations. Wherein the preliminary foaming device (21) includes a foaming ratio variable means (28) that can be set to a predetermined preliminary foaming ratio,
Weight measuring means (4) for measuring the weight of the foam molded article transferred from the foam molding machine (3), and comparing the measured weight value obtained by the weight measuring means (4) with a predetermined value. A pre-foaming control section (9) comprising a signal processing means (12) for outputting to the foaming magnification varying means (28) of the pre-foaming device (21) based on the comparison result to change the preliminary foaming magnification. Foam molding system (1) ".

The prefoaming device (21) provided in the foam molding system (1) of the present invention is provided with a foaming ratio changing means (28) so that the prefoaming ratio can be appropriately changed. As the changing means (28), various types such as a type in which the pre-foaming operation time by the heating medium is adjusted and a type in which the amount of the raw material expandable thermoplastic resin particles is adjusted can be used. The former type is provided with a level switch (29) for detecting the upper height of the pre-expanded particles that expand and expand in the pre-expansion tank, thereby controlling the supply of the heating medium (Japanese Utility Model Publication No. 55-55). -42909). The expansion ratio changing means (28)
Is configured to be controllable by an output signal from a preliminary foaming control unit (9) described later.

As the foam molding machine (3) used in the foam molding system of the present invention, those known in the art can be used as they are. Usually, a curing tank is used between the foam molding machine (3) and the preliminary foam molding apparatus (21), but the use of the curing tank (22) is also preferable in the system of the present invention. However, at the time of this use, in the present invention, since the pre-expansion ratio is feedback-controlled by the weight of the foam molded article as described later, the curing conditions and molding conditions until the pre-expanded particles become the foam molded article are kept constant. There is a need. Therefore, in the apparatus of the present invention, it is preferable to use the curing tank (22) and the foam molding machine (3) as a set. Further, in the system of the present invention, a plurality of foam molding machines (3) may be used. In this case, it is preferable that the curing tank (22) and a transfer device (8) described later are also used in correspondence with each foam molding machine (3).

As the transfer device (8) used in the system of the present invention, a transfer device comprising a so-called two-chain conveyor known in the art can be used.

The prefoaming control section (9) provided in the system of the present invention mainly comprises a weight measuring means (4) and a signal processing means (12). The weight measuring means (4) is not limited as long as it can measure the net weight of the foam molded article obtained by the foam molding machine (3) and can output the measured value to the signal processing means (12) described later. Of the form. As a preferred example, there can be cited one having a measuring part which can protrude and enter from the transfer path of the transfer device (8). In this case, for example, a load cell (43) can be used as the measuring unit. The weight measuring means (4) may be provided immediately after the foam molding machine (3), or may be set via a dryer during this time. The weight measuring means (4) may be configured to measure each foam molded article, or may be configured to perform a sampling test for each predetermined number.

The signal processing means (12) includes an input setting section (14) capable of setting a predetermined value in advance, a predetermined value set in the input setting section (14) and the weight measuring means (4).
(15) that compares the measured value with the output value of the pre-expansion device (21) based on the result of the comparator (15). And an operating means (13).
As the predetermined value set in the input setting unit (14), an appropriate weight (or specific gravity) range of the foam molded article corresponding to the appropriate range of the basis weight is selected. A calibration curve indicating the relationship between the pre-expansion ratio and the weight of the foam molded article is built in between the comparator (16) and the magnification changing operation means (13). Calculation and magnification change operation means (1
A magnification adjustment unit for outputting the data in 3) may be provided.

[0014]

According to the method described in claim 1 of the present application, after a predetermined amount of the pre-expanded particles is subjected to foam molding, the weight of the obtained foam molded article is measured. Is larger than the predetermined value, the preliminary expansion ratio is increased based on the result. As a result, the volume of the pre-expanded particles increases, the specific gravity decreases, the amount supplied to the foam molding decreases, and the so-called basis weight decreases, so that a foam molded article having an appropriate expansion ratio can be obtained. On the other hand, if the weight measurement value is lower than the predetermined value, the pre-expansion ratio is reduced based on the result, whereby the volume of the pre-expanded particles is reduced and the specific gravity is increased. Then, the amount supplied to the foam molding is increased, and the weight per unit area is increased, so that a foam molded article having an appropriate expansion ratio is obtained.

According to the foam molding system of claim 2 of the present application, the pre-expanded particles pre-expanded at a certain expansion ratio are:
After filling the foam molding machine (3) with a predetermined amount and subjecting it to foam molding, the foam molding machine (3) is taken out of the foam molding machine (3) and transferred by the transfer device (8). In this transfer process, the weight of the molded article is measured by the weight measuring means (4). The weight measurement value measured by the weight measuring means (4) is compared with a predetermined value set in the signal processing unit (12). As a result, when the measured weight value exceeds a predetermined value, a signal is output from the signal processing unit (12) to the expansion ratio changing unit (28) of the preliminary expansion device (21) so as to increase the expansion ratio. After the pre-expansion ratio is increased, the pre-expanded particles have a lower specific gravity, an increased volume, and a reduced amount of the pre-expanded particles to be filled in the expansion molding machine, thereby reducing the basis weight. As a result, the expansion ratio is corrected to an appropriate range, and a foamed product having an appropriate specific gravity is formed.
If the measured weight value is lower than the predetermined value, a signal is output from the signal processing section (12) to the expansion ratio changing means (28) of the preliminary expansion device (21) so as to reduce the expansion ratio. The pre-expanded particles after the pre-expansion ratio has been reduced have a higher specific gravity, a reduced volume, and an increased amount of filling in the foaming molding machine (3), thereby increasing the basis weight. As a result, the expansion ratio is corrected to an appropriate range, and a foamed product having an appropriate specific gravity is formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments, but the present invention is not limited thereto. Embodiment 1 FIG. 1 is a structural explanatory view of an example of a foam molding system for carrying out the method of the present invention. Foam molding system (1)
Is a pre-expanded particle supply section (2), a vertical foam molding machine (3), a weighing machine (4), a dryer (5), a packing section (6),
Storage / shipping section (7), transfer conveyor (8) installed from the vicinity of the vertical foam molding machine (3) to the storage / shipping section (7), feedback control section (9), and system control section (10)
Mainly consisting of

The pre-expanded particle supply section (2) is provided with a pre-expanded particle production machine (2) for pre-expanding the raw material expandable resin particles.
1), a curing tank (22) for storing the pre-expanded particles, a filler (not shown) for filling a predetermined amount of the pre-expanded particles sent from the curing tank (22) into a vertical foam molding machine (3). 22) and a pre-expanded particle supply control section (2A) for controlling the supply of the pre-expanded particles to a vertical foam molding machine (3) to be described later.

The pre-expanded particle production machine (21) is shown in FIG.
As shown in the figure, a cylindrical container (23), a stirring member (24) provided in the container, and a perforated member provided in the lower portion of the container, through which steam passes but does not pass through the raw material expandable thermoplastic resin particles. A plate (25), a steam supply means (26) for supplying steam to a steam chamber provided below the perforated plate (25), and a material provided above the cylindrical container (23) to measure the raw material to a fixed amount. Hopper (27) to be supplied as supply and expansion ratio changing means (28) for adjusting the pre-expansion ratio in the cylindrical container (23)
It is composed of

Although the expansion ratio changing means (28) is not shown in detail, the height thereof can be adjusted on the side surface of the cylindrical container (23). A level switch (29) can be output to the steam supply means (26) so as to stop the supply of steam when the particles rise to a certain level, and the position of the level switch (29) is changed to change the position of the level switch (29). The expansion ratio of foaming can be adjusted.

The curing tank (22) has an upper part connected to a particle supply line (a) and a lower part connected to a particle feed line (b). The particle supply line (a) is connected from the curing tank (22) to a pre-expanded particle manufacturing machine (21) through a flow path opening / closing valve (not shown) and a particle sending means in this order, and each particle sending line (b). ) Are respectively connected to fillers (not shown) via sending means (not shown).

A curing level switch (not shown) is provided in each of the curing tanks (22). When the supplied pre-expanded particles reach the level switch setting position, a signal is sent from the curing level switch to each particle. The output is output to a flow path opening / closing valve (not shown) provided in the supply line (a), and the supply of particles is stopped based on the output. Therefore, the storage amount of the pre-expanded particles can be adjusted by the setting position of the curing level switch. It is configured as follows.

The vertical foaming molding machine (3) is a commonly used known one, and its outline is shown in FIG. 3, as shown in FIG. Is fixed to the lower surface of the movable platen (33) so as to face the convex lower mold (32), and the lift cylinder (36) fixed to the upper center of the top platen (35). The movable platen (33) is supported so as to be able to move up and down. The lifting cylinder (36)
The movable platen (33) is lowered to form a downward concave mold cavity in a state where the concave upper mold (34) covers the fixed convex lower mold (32), and expandable thermoplastic resin particles are contained in these mold cavity. And heated to expand and expand to form a foam molded article (37). After the completion of the foam molding, the movable platen (33) is raised by the elevating cylinder (36) to open the mold, and then the foamed molded product (3) is pushed by the extrusion pin (38) which enters from the upper part of the concave upper mold (34).
7) is configured so that it can be dropped with its opening facing downward. Each of the foam molding machines (3) is controlled by a molding control unit (101) provided in a system control unit (10) described later.

The transfer conveyor (8) is constituted by arranging two endless chain conveyors in parallel. The drive of each of the chain conveyors is controlled by a conveyor drive unit (81).

The weighing scale (4) forms a part of a feedback control section (9) described later (see FIG. 4), and has a cylinder rod (4) of a driving cylinder (41) driven upward.
2) Receiving pan (44) via load cell (43) at the tip
When the drive cylinder (41) is driven while the foamed product is placed on the tray (44), the foamed product is lifted from the transfer conveyor, whereby the weight of the foamed product is reduced. What is measured. The weighing scale (4) is electrically connected from the load cell (43) to a comparing section (11), which will be described later, via an amplifier so that a signal can be output every weight measurement.

As shown in FIG. 4, the feedback control section (9) includes the weighing scale (4), the comparison section (11), the signal processing section (12), and the preliminary expansion ratio adjustment section (13). It is composed of The comparing unit (11) includes an input setting unit (1).
4) and a comparator (15), and the input setting section (14) can store and set, as a predetermined value, an appropriate weight range of the foam molded product corresponding to the appropriate range of the basis weight.
The comparator (15) compares a predetermined value stored in the input setting section (14) with the weighed weight value actually measured by the weighing scale (4). In the signal processing unit (12), if the comparison result in the comparison unit (11) exceeds the predetermined value or is less than the predetermined value, the preliminary expansion ratio adjustment unit (13)
In order to change the pre-expansion ratio to an appropriate pre-expansion ratio via the above, the expansion ratio changing means (28) in the pre-expanded particle manufacturing machine (21) is operated. Pre-expansion ratio adjustment unit (1
3) has a built-in calibration curve showing the relationship between the pre-expansion ratio and the weight of the foam molded article.

The packing section (6) is connected to a not-shown piling section, a not-shown pool line for pooling blocks carried out of the piling section, and a tip end of the pool line, and transfers the blocks by a predetermined number. A packing transfer table (not shown) to be mounted, a chassis (not shown) for arranging the transferred block group at the center of the table, a packing unit (not shown) for packing the block group arranged at the center, and a transfer unit, It mainly comprises a pile and packing control section (61) for controlling the drive of the chassis and the packing means in a certain order.

The storage / shipment section (7) is connected to the storage transfer table (not shown) for transferring the block group packed in the packaging section (6) by a predetermined number, and the storage transfer table. And a plurality of storage lines (not shown). The storage transfer table is provided with storage operation means (not shown) for distributing the transferred packing block group to an intended storage line and then sending out the storage block group. The storage operation means is driven by a storage management unit (71). It is configured to be controllable.

The system control unit (10) has a molding control unit (101) that can set a series of molding conditions for the vertical foam molding machine (3) and drives it according to these conditions. 2A), a pile / packing control unit (61), a storage management unit (71), a conveyor driving unit (8)
1) and can be driven and controlled based on a preset program.
Further, an emergency interruption operation by the feedback control unit (9) is configured to be possible.

The above system configuration is an example, and another system configuration example shown in FIG. 5 can be given. That is, the configuration of FIG. 1 is basically the same as that of FIG. 1 except that the steps from foam molding to packing are performed in a plurality of lines. Therefore, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. In such a case, in each line, the curing tank (22) and the vertical foam molding machine (3) are different. It is necessary to provide a pair, and although not shown, it is necessary that feedback control is also provided independently for each line.

A series of operations of the foam molding system (1) of the present invention will be described with reference to FIGS. First, in the comparison unit (11) of the feedback control unit (9), an appropriate weight range is set in the input setting unit (14) in advance.
On the other hand, the level switch (29) of the expansion ratio changing means (28) is set to a predetermined level so that the intended expansion ratio is achieved, and the pre-expanded particle supply control section (2A)
Setting, molding condition setting in the molding control unit (101) and piling / setting in the piling / packaging control unit (61).
The setting of the packing condition is performed when the system control unit (10) reads the program.

First, pre-expanded particles are produced by a pre-expanded particle production machine (21). The pre-expanded particles are level switched (2
It is prepared at a predetermined pre-expansion ratio determined by the level of 9). The pre-expanded particle supply control unit (2A) opens a flow path opening / closing valve (not shown) of the particle supply line (a) and drives a particle sending means (not shown) to move the pre-expanded particle production machine (21) from the curing tank (22). ) Is filled with pre-expanded particles. Next, when the upper end of the pre-expanded particles stored in the curing tank (22) reaches the curing level switch setting position, a flow path (not shown) of the particle supply line (a) based on the output from the curing level switch. The on-off valve is closed, and this signal causes the control unit (2A) to close the particle sending means (not shown).
Next, when the molding control unit (101) is operated based on a command from the system control unit (10), the pre-expanded particle supply control unit (2A) sends a particle sending means (not shown) of the particle delivery line (b). It is turned on, and a predetermined amount of pre-expanded particles is filled into the mold of the foam molding machine (3) through a filler. When the filling of a predetermined amount into the mold is completed, the control section (2A) turns off the particle sending means (not shown) of the particle sending pipe (b) and simultaneously, the not shown of the particle supply pipe (a). The flow opening / closing valve is opened, and the granulating means (not shown) is turned on to supply the pre-expanded particles. This replenishment is performed until the curing level switch set position is reached as described above, and thereafter the above operation is repeated.

In the foam molding machine (3), a molding control section (101)
The foam molding is performed based on the instruction. After the completion of the foam molding, the foam molded article is taken out on the transfer conveyor (8) based on a command from the system control unit (10). Next, the foam molded article transferred by the transfer conveyor (8) is placed on a tray (44) rising from the lower part thereof at the setting position of the weighing scale (4), lifted from the transfer conveyor (8) surface, and loaded. The weight is measured by (43).

Here, the weight measurement value measured by the weighing scale (4) is immediately output to the comparison unit (11). And the comparison unit (1
In 1), the measured weight value is compared with a predetermined value preset in the input setting section (14) through the comparator (15). As a result, when the weight measurement value is included in the predetermined value, the weight measurement value is sent to the next step as it is, but when the weight measurement value is less than the predetermined value or exceeds the predetermined value, the feedback control unit (9) work. That is, when the weight measurement value is less than the predetermined value, the signal processing unit (12) uses the calibration curve built in the preliminary expansion ratio adjustment unit (13) to
The degree of magnification change to the appropriate prefoaming ratio is calculated, and the expansion ratio changing means (2) is set so as to lower the level switch (29) in the pre-expanded particle manufacturing machine (21) according to the degree of magnification change.
The operation is commanded in 8), and feedback control is performed. As a result of this feedback control, the pre-expanded particles thereafter are reduced in pre-expansion ratio to become pre-expanded particles having a large specific gravity. It shows the proper weight. On the other hand, when the weight measurement value exceeds a predetermined value, the signal processing unit (12) in the feedback control unit (9) performs the preliminary expansion ratio adjustment unit (13).
The degree of change in the magnification to the appropriate pre-expansion ratio is calculated from the calibration curve built in the apparatus, and the expansion ratio is increased so that the level switch (29) in the pre-expanded particle production machine (21) is raised in accordance with the degree of change in the ratio The operation is instructed to the changing means (28),
Feedback control is performed. As a result of this feedback control, the pre-expanded particles thereafter are increased in pre-expansion ratio to become pre-expanded particles having a small specific gravity, and the foam molded article formed by using the pre-expanded particles as a raw material similarly has a low specific gravity, It shows the proper weight. In this way, the feedback control is performed based on the measured weight value, the pre-expansion ratio of the pre-expanded particles is corrected to an appropriate ratio, and a foam molded article having a predetermined appropriate weight is sent to the next step.

The foam molded articles having a certain appropriate weight are sequentially dried in the dryer (5) and then transferred to the packing section (6). In the packing section (6), the block bodies piled by a predetermined number are pooled in a pool line (not shown), and then collected and packed by a chassis (not shown) in a predetermined number at the center of a packing table (not shown). This operation is performed by a piling / packing control unit (61) operated via the system control unit (10).

The packed block group is transferred to the storage / shipment unit (7), and the storage operation unit (not shown) is operated by the storage management unit (71) operated via the system control unit (10). A predetermined number of packing blocks are transferred to a storage transfer table (not shown), and are sorted and stored on storage lines (not shown).

By a series of system controls including the feedback control described above, foam molding is performed by adjusting the pre-expansion ratio of the pre-expanded particles, filling the pre-expanded particles, foam molding, quality control of the foam molded product, packing, and storage. Up to now, it will be performed orderly by the consistent operation.

[0037]

According to the present invention, since the pre-expansion ratio is changed and the specific gravity is adjusted based on the weight of the foam molded product to be foam-molded, feedback control is performed so that the proper basis weight is always maintained. As a result, a good quality foam molded article can be constantly obtained. In addition, since the above-mentioned feedback control is included in a series of system controls, the process from adjustment of the pre-expansion ratio of pre-expanded particles to filling of pre-expanded particles, foam molding, quality control of foam molded products, packing, and storage are integrated. The proper operation can be performed by the operation performed.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of an example of a foam molding system for implementing a method of the present invention.

FIG. 2 is a configuration explanatory view of an example of a pre-expanded particle manufacturing machine used in the system of FIG.

FIG. 3 is a configuration explanatory view of an example of a vertical foam molding machine used in the system of FIG. 1;

FIG. 4 is a configuration explanatory diagram of an example of a feedback control unit in the system of FIG. 1;

FIG. 5 is a schematic view of a line configuration in another example of the foam molding system of the present invention.

[Explanation of symbols]

(1) ... foam molding system (2) ... pre-expanded particle supply section (3) ... vertical foam molding machine (4) ... weight scale (5) ... dryer (6) ... packing section (7) ... storage and shipping section (9) ... feedback control unit (10) ... system control unit (11) ... comparison unit (12) ... signal processing unit (13) ... preliminary expansion ratio adjustment unit (14) ... input setting unit (15) ... comparator (21 ) Pre-expanded particle manufacturing machine (22) Curing tank (23) Cylindrical container (28) Expansion ratio changing means (29) Level switch (61) Piling / packing control unit (71) Storage management unit (81)… Conveyor drive

Claims (2)

(57) [Claims] 1. A foam molding method in which raw material expandable thermoplastic resin particles are pre-foamed, and the obtained pre-foamed particles are subjected to foam molding to form a predetermined foam molded product. Is measured, based on the specific gravity of the foam molded product obtained from the measured value, to determine the good or bad of the basis weight, if defective, adjust the specific gravity of the pre-expanded particles by changing the pre-expansion magnification, A feedback-type foam molding method that controls so as to obtain a foam molded article having a basis weight. 2. A pre-expansion device for pre-expanding expandable thermoplastic resin particles as a raw material, a foam molding machine for heating and foaming the pre-expanded particles obtained by the pre-expansion device to form a foam molded article, and the foam molding machine. And a transfer device for sequentially transferring the foam molded article obtained in the step (a) to a predetermined place, wherein the preliminary foaming device includes a foaming ratio variable means capable of setting a predetermined preliminary foaming ratio, Weight measuring means for measuring the weight of the foam molded article transferred from the machine, and comparing the weight measured value obtained by the weight measuring means with a predetermined value set in advance, and based on the comparison result, the expansion ratio of the pre-foaming device A foam molding system comprising a prefoaming control section comprising a signal processing means for outputting to a variable means and changing a prefoaming ratio.