JPH08290466A - Mold for molding sheet - Google Patents

Abstract

PURPOSE: To make the temperature of an entire mold stable and uniform and to improve the yield of products remarkably by forming cooling water passages which independently cool every line of mold lines which are formed by molds arranged perpendicularly to the transfer direction of a thermoplastic sheet in a substrate part. CONSTITUTION: A mold 1 for molding a sheet has a mold part 10 in which numbers of molds having a cavity of the same shape 1a-1f, 2a-2f, 3a-3f, 4a-4f, 5a-5f, 6a-6f, 7a-7f are arranged to form a lattice in which they meet at right angles on a plane and a substrate part which supports and fixes the mold part 10. In the substrate part, cooling water passages without a branch 51a-51b, 52a-52b,... 57a-57b for independently cooling every line of mold lines which are formed by molds 1a-1f, 2a 2f, 3a-3f, 4a-4f, 5a-5f, 6a-6f, 7a-7f arranged perpendicularly to the transfer direction of a thermoplastic sheet which is supplied to the mold part 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet molding die used for simultaneously forming a plurality of container-like plastic molded articles from a sheet by so-called vacuum forming, pressure forming, etc. It relates to a cooling structure.

[0002]

2. Description of the Related Art A general vacuum forming process which has been generally carried out, that is, from the delivery of a plastic sheet to the production of a vacuum-formed plastic container product by heating, forming, and trimming the delivered sheet. A series of steps of is shown in FIG.

In FIG. 4, a delivery device 110 delivers a plastic sheet 112 wound around a delivery roll 111. The unwound plastic sheet 112 enters the sheet heating device 120 through several guide rolls, and is heated by a heating unit such as a heater 121 to be a softened molten sheet. Next, the thus softened / melted sheet enters the multi-cavity forming apparatus 130, where it is suction-adhered to all the cavities of the vacuum forming die 131 at the same time (and then cooled), and a plurality of three-dimensional sheets are formed. Molded into a typical container shape. Of course, a plurality of cavities of the vacuum molding die 131 exist in the depth of the drawing. Note that reference numeral 133 indicates an assist plug.

The molded container group thus molded enters the trimming device 140 in the next step, where the molded container is
By the pair of trimming cutter upper blade 141a and trimming cutter lower blade 141b arranged above and below the sheet,
The plastic containers 142 are manufactured by trimming each row toward the depth of the drawing. The trimmed plastic containers 142 are stacked one after another and stored, while the remaining unnecessary sheet scrap is
It is discharged into a scrap container (not shown).

In such a series of steps, the molding apparatus 1
Attention is paid to the vicinity of the vacuum forming die 131 of 30. The position on the most upstream side of the vacuum forming die 131, that is, the position closest to the hot (heating) zone of the sheet heating device 120 is set as the point (a), and the most downstream position closest to the trimming device 140 is set at the (b). In order to explain the subject of the present application in an easy-to-understand manner, the state of FIG. 4 is slightly different from that of the molding apparatus 130. It is assumed that there is no play between the trimming device 140 and the trimming cutter upper and lower blades 141a and 141b, which are arranged in close contact with the trimming device 140 (the molding 2 in the state of FIG. 4). There is play for each piece).

The operation of the trimming device 140 in the next step is performed as follows. That is, the trimming of the molded container is performed by using the trimming cutter upper blade 141a and the trimming cutter lower blade 141b.
It is performed in a state in which the sheet is temporarily stopped for a residence time of t ₁ sec for each row of the molded bodies 31 arranged in the width direction.
Immediately after that, the molded product to be trimmed in the next row has the trimming cutter upper and lower blades 141 at a speed V (cm / sec).
a, 141b.

Under such a circumstance, the molded body on the hot zone side of the vacuum molding die, that is, the molded body formed by the die row at the top upstream of the sheet flow, is on the trimming cutter upper and lower blades 141a, 141b. Until ((a)
(Moving from (b) to (b)), if there are N rows of molds, the required time T is T = (L / V + Nt ₁ ). That is, those in the most downstream row of the compacts vacuum-molded by the vacuum molding die 131 are trimmed almost immediately after the molding, and those in the most upstream row are trimmed at about the above T time. It will be trimmed.

During this period, the sheet preheated by the sheet heating device 120 is gradually pulled out from the hot zone of the heating device 120 and comes onto the vacuum forming die 131, and the entire surface of the vacuum forming die 131 is heated. When the sheet is covered, the sheet is stopped (the stop time is t ₂ hours (usually t ₂ > t ₁ )) and sucked into the cavity to be molded. Therefore, comparing the temperatures of the sheets at points (a) and (b) during vacuum forming, the temperature at point (a) is higher than at point (b). The point (a) is better for the degree of adhesion to the cavity. On the other hand, the molded body formed at the point (a) has a larger shrinkage deformation due to cooling than the molded body formed at the point (b), and the amount of deformation until the trimming cutter upper and lower blades 141a and 141b are applied is ( The molded body molded at point (a) is larger than that at point (b).

In actual forming, the speed at which the formed sheet is transferred toward the trimming cutter so that the upstream side and the downstream side of the sheet heated in the hot zone do not cause a temperature difference due to the cooling during the transfer. It is transferred onto the mold 131 at a speed V ₂ much faster than V ₂ .

On the other hand, during the time t ₂ required for forming, the sheet formed by the hot zone and the mold is stopped,
Downstream from the mold, the sheet to which the molded body is attached is transported in the trimming cutter direction at an average speed V _av = L / T. Therefore, the sheet length t ₂ × V _av transferred at V _av for at least t ₂ hours between the mold and the trimming cutter.
Play length needs to be maintained.

Under these circumstances, the length of the play portion of the sheet becomes shortest immediately after the completion of molding, and the length L / V from the completion of molding.
It becomes the longest after ₂ hours.

In any case, between the most upstream-side molded body row and the most downstream-side molded body row, there is no choice but to make a difference of the residence time in the play portion by the T time as described above. The amount of deformation due to shrinkage remains the same for the molded body molded at the point (a) than that for the molded body at the point (b).

For such a molding imbalance,
If the cooling process of the sheet is a stable steady state, there is no particular problem if the shape design of the molded body is performed in advance by taking measures such as taking a large margin for trimming.

[0014]

However, in the actual operation, the vacuum forming die 1 is heated by the heat energy transferred from the heated sheet of the vacuum forming die 131.
A temperature gradient is generated in the longitudinal direction of 31, and the amount of heat stored is relatively different between the upstream side and the downstream side of the vacuum forming die 131, and a temperature difference occurs in the longitudinal direction of the vacuum forming die 131.

Further, the central portion of the vacuum forming die 131 has a smaller heat radiation area than the end portions around the die, and the thermal energy stored therein is larger than that of the surrounding area. In addition, the heating sheet itself to be molded causes a difference in the amount of heat transferred to the mold with time mainly due to uneven thickness.

Due to the above-mentioned reasons, it is extremely difficult to form a stable sheet cooling process in a steady state in vacuum forming using a multi-cavity vacuum forming die. . As a result, the molded body is inevitably deformed and the product yield does not necessarily increase.

The present invention was devised in view of such circumstances, and an object thereof is to make it possible to stabilize and uniformize the temperature of the entire molding die very easily in an actual molding operation. As a result, it is intended to provide a sheet molding die capable of improving the product yield.

[0018]

In order to solve such a problem, the present invention has a structure in which a large number of molds having cavities of the same shape are arranged so as to form a lattice orthogonal to each other on a plane. In a sheet-molding mold having a mold part and a substrate part for supporting the mold part and fixing the mold part, the substrate part has a direction relative to a transfer direction of a thermoplastic sheet provided for the mold part. Mold row formed by a plurality of molds arranged in a direction orthogonal to
It is configured such that a cooling water flow path without branching for independent cooling is formed for each row.

Further, as a preferred embodiment of the present invention, the cooling water passage formed in the substrate portion has two cooling water inlets near the center of the mold row, and the cooling water is provided at both ends of the mold row. It is configured so as to have a form of a two-series flow path having an outlet.

In a preferred aspect of the present invention, the substrate portion further comprises a contact molding means for molding a thermoplastic sheet, which is molded by the mold, in the mold cavity so that the thermoplastic sheet is closely bonded to the mold cavity. It is configured to include knockout means for peeling the sheet after being crushed from the cavity.

In a preferred embodiment of the present invention, the knockout means has a cooling water flow path for cooling the knockout means, and the cooling water flow paths for cooling the knockout means are arranged in parallel in parallel with the transfer direction of the thermoplastic sheet. Each of the mold rows formed by the above is a flow path that goes around the circumference of the mold row, and is a flow path that is isolated from any of the cooling water flow paths of the mold row. It is configured to be arranged in the gap.

Further, as a preferred embodiment of the present invention, the mold rows formed in parallel in parallel with the transition direction of the thermoplastic sheet are configured to be odd rows.

[0023]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a plan view of a sheet molding die of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a sectional view taken along the line BB of FIG. is there.

The sheet molding die 1 of the present invention is used by being incorporated into the above-described general process of vacuum forming, and is a softened molten sheet (heated by being heated by a sheet heating device from the left side of FIG. 1). A plastic sheet) is conveyed, and the conveyed softened / melted sheet is molded into a plurality of three-dimensional container shapes by the sheet molding die 1 of the present invention.

As shown in FIG. 1, the sheet molding die 1 of the present invention thus used has a plurality of three-dimensionally fused sheets (thermoplastic sheets) conveyed onto the molding die 1. The mold unit 10 is provided for molding into various container shapes, and the mold unit 10 includes a large number of molds 1a to 1f, 2a to 2f, 3a having cavities of the same shape.
~ 3f, 4a-4f, 5a-5f, 6a-6f, 7a-
7f are arranged and formed so as to form a lattice that is orthogonal on a plane.

That is, in the embodiment shown in FIG. 1, as an arrangement of the same cavities, 1 to 7 columns are arranged in the vertical direction in the drawing (perpendicular to the transfer direction (C) of the thermoplastic sheet provided to the mold part). In the present invention, the direction is referred to as the "column" direction, and in the lateral direction, 1 to 5 rows (the direction parallel to the transfer direction (C) of the thermoplastic sheet provided to the mold portion is the "row" direction in the present invention). And) are arranged so as to form a lattice.

A large number of molds 1a to 1f, 2a to 2f, 3a to 3f, 4a to form the mold portion 10 as described above.
4f, 5a to 5f, 6a to 6f, and 7a to 7f are fixed to the plate-shaped substrate portion 20 (FIGS. 2 and 3).

Further, the substrate section 20 is provided with a mold row formed by a plurality of molds arranged in a direction orthogonal to the transfer direction (C) (FIG. 1) of the thermoplastic sheet supplied to the mold section 10. Is formed in each row independently of each other to form a cooling water flow path without branching. As a result, the cooling for each row is arbitrarily performed, and the temperature of the entire mold unit 10 can be arbitrarily adjusted.

In this embodiment, seven mold rows are used to form the mold section 10. Therefore, as a basic idea, seven independent rows of cooling water flow paths are formed in each row. -ing As a more preferable embodiment of the cooling water flow path, as shown in FIGS. 1 and 2, cooling water inlets are provided at two locations near the center of the mold row for each mold row (for example, in FIG. 2). 52a _IN , 52 shown
b _IN ) and cooling water outlets (for example, 52a _OUT , 52 shown in FIG. 2) at both ends of the mold row for each row.
b _OUT ). As a result, the heat energy concentratedly stored in the center of the mold portion 10 can be forcibly released to the outside, and the temperature of the entire mold portion 10 can be easily made uniform.

The form of the two-series flow path thus constructed will be described in more detail below.

In order to facilitate understanding of the form of the two-series flow path, the description will be made focusing on the second mold row shown in FIG. In FIG. 2, two cooling water flow paths 52a and 52b are formed in the base plate portion 20 substantially directly below the second mold row and extend from the center of the mold row toward both ends. Has been done. On the other hand, below the substrate portion 20, cooling water supply pipes 62a and 62b for supplying cooling water to the cooling water flow paths 52a and 52b are installed, respectively. The cooling water supply pipes 62a and 62b are provided at the center of the substrate portion 20.
Locations 52a _IN , 52b _IN (these are the cooling water flow paths 52a
And 52b, which corresponds to the substantially central end portion). Thereby, the cooling water supply pipes 62a and 62b
The cooling water (in the direction of the arrow α) supplied from each of the cooling water flow paths 52a _IN and 52b _{IN at} the substantially central portion of the substrate portion 20 flows into the cooling water flow paths 52a and 52b, respectively.
After the cooling of each mold is completed from the center of 2a, 52b toward both ends, the mold is discharged (arrow (β) direction).

That is, in the example of FIG. 2, one cooling water passage 52a is formed for cooling the molds 2c, 2b, 2a, and the other cooling water passage 52b is formed in the mold 2.
It is formed for cooling d and 2f. In addition, the respective molds 2a, 2 of the cooling water flow paths 52a, 52b.
At locations located at the bottom of b, 2c, 2d, and 2f, a ring-shaped cooling path 52 is provided in order to increase the cooling efficiency as shown in the figure.
It is preferable to provide a'and 52b '. Such ring-shaped cooling passages 52a ′ and 52b ′ basically have a form associated with the main line of one row of the cooling water passages 52a and 52b, and are not called branching of the cooling water passages. That is, in the present invention, as long as the cooling water flow passage has the original function of independently cooling each mold row, even if there is a slight change or addition of the flow passage of the present invention, It is defined as a cooling water flow path which does not deviate from the technical idea, that is, a cooling water flow path which is isolated from the cooling water paths of other mold rows and has no branch.

As described above, the cooling water flow path of the two series flow paths as shown in FIG. 2 is formed in the substrate portion 20 for each mold row. In FIG. 1, the installation position of the cooling water flow path, which is arranged for each mold row, is shown by a dotted line. That is, the second-line cooling water flow paths in the first row are 51a and 51b, and
The second series cooling water flow passages in the second row are 52a and 52b, the second series cooling water flow passages in the third row are 53a and 53b, and the second series cooling water flow passages in the fourth row are 54a and 54b. The second-line cooling water flow paths in the fifth row are 55a and 55b, and are in the second row in the sixth row.
The series cooling water passages are indicated by 56a and 56b, and the second series cooling water passages in the seventh row are indicated by 57a and 57b. When the number of mold rows is odd as shown in the drawing (five rows are illustrated in this embodiment), in order to uniformly cool the entire mold portion 10,
It is preferable that the two series cooling water flow paths are alternately arranged in each row.

In all of these, as described above, the cooling water supply pipe is installed in the lower portion of the substrate portion 20 so that the cooling water flows from the central portion of the mold row toward both ends. Needless to say (in FIG. 3, only one side of the substrate portion 20 is visible, but the cooling water supply pipes 61b, 62b, 63b, 64b, 65b,
66b and 67b are installed).

Further, in the pipe, for example, near the inlet of the cooling water supply pipe, a flow rate adjusting valve for adjusting the flow rate of the cooling water flow passage of the two series flow passage is attached,
The cooling conditions of the mold can be finely adjusted for each flow path. Such adjustment is performed by, for example, installing a thermocouple on the outlet side of the cooling water flow path and measuring the cooling water temperature at the die outlet, adjusting the flow rate based on this temperature data, and cooling the die. It is preferable to make it uniform. Although the flow rate adjustment based on the temperature data can be performed manually, it is usually desirable to use automatic control using a computer or the like in order to save labor.

Although the control accuracy of the mold temperature may be slightly inferior, the two series are stopped, and the cooling water flow path formed in the substrate section is made into a communication flow path communicating to both ends of the mold row. One inlet for cooling water may be provided near the center of the mold row, and outlets for cooling water (throttle valves for adjusting the flow rate as necessary) may be provided at both ends of the mold row.

Furthermore, one end of the communication passage is used as an inlet for cooling water and the other end is used as an outlet for cooling water, and cooling water passages are arranged so that the inlets and outlets of the cooling water alternate between adjacent mold rows. Even with the provided mold, when a container having a relatively simple shape is molded, the shape of the molded container is stable and well aligned.

Although not shown in the drawing, the substrate portion 20 is usually provided with a contact molding means for closely bonding and molding a thermoplastic sheet shaped by the mold into the mold cavity. It is connected. The close contact forming means is a forming means including a piping system for performing vacuum forming and pressure forming, particularly vacuum and pressure forming. Here, the vacuum forming is a method of easily forming a thermoplastic sheet by using one of a female mold and a male mold and heat and atmospheric pressure, and specifically, a heat-softened sheet and a metal sheet. This is a method in which a vacuum is applied between the mold and the sheet, and the sheet is brought into close contact with the mold. Normally, vacuum molding is a female mold (cavity molding)
However, it is defined by a broad concept including the case of using a male mold (drape molding) and the case of using a moving male plug (plug assist molding). Pneumatic molding is
This is a molding method in which a sheet is clamped between a male mold and a board, and compressed air is blown from the board to press the sheet against the molding surface of the female mold. Hydraulic pressure or mechanical pressure may be used instead of compressed air. Pressure forming and vacuum forming can also be used together.

In addition to such contact molding means, further, the substrate portion 20 is provided with knockout means for peeling and detaching the sheet after being shaped by the mold from the cavity. It is common.

In the embodiment shown in FIGS. 1 to 3, a knockout plate 80 as a knockout means is formed. The knockout plate 80 has a honeycomb-like plate shape in which the contour of each mold cavity in FIG. 1 (actually, about 0.3 mm outward from the contour) is punched out from a single plate. Knock back plate 4
0 (FIGS. 2 and 3). Then, by the vertical movement of the knock back plate 40, the knock-out plate 8
The zero acts to push the molded sheet out of the cavity. The knockout plate 80 can be replaced with a knockout pin, but if, for example, the sheet molded product (molded product) has a portion having an inverse taper for fitting with the lid, the release resistance is extremely high. Since it becomes large, it is better to use the knockout plate 80 in order to realize reliable release and prevent accidents such as pin breakage.

The knockout means of the knockout plate 80 as described above also accumulates heat by molding similarly to the molding section 10. Therefore, the knockout plate 80 is provided with a cooling water flow path for cooling the knockout means in order to cool the sheet flat portion (the sheet flat portion with which the knockout plate 80 abuts when protruding) other than the molded three-dimensional form. Is desirable.

The cooling water flow path for cooling the knockout means is
Each of the mold rows formed in parallel in parallel with the transfer direction of the thermoplastic sheet is a flow path that goes around its periphery and is isolated from any of the cooling water flow paths of the mold row. A separate flow path is provided in the gap between the mold groups of the mold section.

That is, in FIG. 1, one row of the die groups 1a, 2a, 3a, 4a, 5a, 6a, 7a in the first row is set to one.
In the periphery of the unit, a cooling water flow path for the mold row entering from 81 _IN and exiting from 81 _out is formed in the knockout plate 80 so as to surround the one unit. Similarly, the die groups 1c and 2 in the third row
A cooling water flow path of the mold row that enters from 82 _IN and that exits from 82 _out surrounds 1 unit of each row of c, 3c, 4c, 5c, 6c, and 7c as one unit. It is formed in the knockout plate 80. Mold group 1f, 2f, 3f, 4f, 5 in the 5th row
A cooling water flow path for the mold row that enters from 83 _IN and exits from 83 _out is also formed in the knockout plate 80 around the area where one row of f, 6f, and 7f is one unit.
As can be seen from such a relationship, in order to cool the knockout plate 80 more uniformly, it is preferable that the number of rows of the mold is set to an odd number of rows.

In this way, the knockout plate 8
By cooling 0, the remaining sheet plane portion other than the three-dimensionally molded portion (becomes a scrap portion)
Is also cooled at the same time during molding, and the influence of sheet shrinkage during the punching step of the next step is extremely small. Therefore, the punched product has extremely uniform dimensions regardless of the rows and columns of each mold, and the product yield can be further improved. Also, the shot cycle can be increased, and the productivity is also remarkably improved.

The present invention will be described in more detail below by showing specific examples.

(Specific Example) Three types of molds as shown below were prepared. That is, a mold in which a mold column cooling water flow path including two series flow paths of the present invention and a knockout plate cooling water flow path that makes one turn for each mold row are arranged (referred to as "the present mold 1"). Mold row cooling water flow channel (where outlet and inlet are alternately changed for each row) having one end of the communication channel of the present invention as an inlet of cooling water and the other end as an outlet, and knockout plate cooling similar to the above-mentioned die A mold having a water flow path (referred to as “the mold 2 of the present invention”) and one end of the first mold row as a cooling water inlet and the other end of the final mold row as a cooling water outlet. A conventional mold (referred to as "comparative mold 1") of the type in which the mold is cooled in one continuous cooling water channel and the knockout plate is similarly cooled in one continuous cooling water channel was prepared.

A container having the same shape was molded from a sheet by using such three types of molds. In order to fit a lid formed by injection molding into the container, a reverse taper portion of 7.5% with respect to the vertical is formed on the upper end of the container over a length of 45 mm.

700 containers were molded using each of the above molds. Outlet water temperature is 22 ℃ + 1 ℃ for cooling during molding
The amount of cooling water was adjusted so that

Trimming cut mistakes for each molded product,
Three items were evaluated: improper fitting (lid removed) and overfitting (difficult to remove after attaching lid).

The results are shown in Table 1 below.

[0052]

[Table 1]

[0053]

The effect of the present invention is clear from the above results. That is, according to the present invention, a mold part in which a large number of molds having the same shape of cavities are arranged so as to form a lattice that is orthogonal on a plane, and a mold part for supporting the mold part and fixing the mold part A sheet forming die having a base plate portion, and the base plate portion is formed by a plurality of metal molds arranged in a direction orthogonal to a transfer direction of the thermoplastic sheet provided to the mold portion. A cooling water flow path without branches is formed for cooling the mold rows independently for each row. Therefore, the sheet molding die of the present invention can easily adjust the temperature for each mold row, and can extremely easily stabilize and equalize the temperature of the entire sheet molding die in the molding operation. As a result, the product yield can be significantly improved. Further, the shot cycle is increased and the productivity is remarkably improved.

[Brief description of drawings]

FIG. 1 is a plan view of a sheet molding die of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

3 is a cross-sectional view taken along the line BB of FIG.

FIG. 4 is a diagram showing a schematic process of vacuum forming generally performed.

[Explanation of symbols]

1 ... Sheet forming mold 1a to 1f, 2a to 2f, 3a to 3f, 4a to 4f, 5
a-5f, 6a-6f, 7a-7f ... Mold 10 ... Mold part 20 ... Substrate 51a, 51b, 52a, 52b, 53a, 53b, 5
4a, 54b, 55a, 55b, 56a, 56b, 57
a, 57b ... Cooling water flow path 80 ... Knockout means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B29L 22:00

Claims (5)

[Claims] 1. A mold part, in which a large number of molds having cavities of the same shape are arranged so as to form a lattice orthogonal to each other on a plane, and a mold part for supporting the mold part and fixing the mold part. A sheet forming die having a substrate part, wherein the substrate part is formed by a plurality of molds arranged in a direction orthogonal to a transfer direction of a thermoplastic sheet provided to the mold part. A sheet-forming mold, wherein a cooling water flow path without branching is formed for cooling each row independently. 2. The cooling water flow path formed in the substrate portion,
The sheet molding die according to claim 1, wherein the sheet molding die is provided with two cooling water inlets near the center of the die row, and two series flow passages having cooling water outlets at both ends of the die row. 3. The substrate section further comprises a contact molding means for closely bonding a thermoplastic sheet shaped by the mold into a mold cavity for molding, and the shaped sheet after molding. The sheet molding die according to claim 1 or 2, further comprising a knockout means for peeling from the cavity. 4. The knockout means includes a cooling water flow path for cooling the knockout means, and the cooling water flow path for cooling the knockout means is formed in parallel in parallel with the transfer direction of the thermoplastic sheet. Each of the rows is a flow path that goes around the circumference and is arranged in the gap part of the mold group of the mold part as a flow path that is isolated from any of the cooling water flow paths of the mold row. The sheet molding die according to claim 3. 5. The mold rows formed in parallel in parallel with the transition direction of the thermoplastic sheet are odd rows.
The sheet molding die described in.