JPS6239089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermoforming apparatus for thermoplastic synthetic resin sheets. In addition, in this specification, the sheet means
It means a thermoplastic synthetic resin sheet.

Generally, sheet thermoforming equipment combines a heater and a pair of molds such as pressure forming or vacuum forming. In conventional equipment, the heater and mold are all arranged in a plane. The sheet pulled out from the raw roll is horizontally transferred from the heater to between the molds by means of chains, belts, etc. that hold both side edges of the sheet.

However, when the sheet is heated and softened in a heater, it sags downward significantly, and the sheet cannot be transferred from the heater to the mold unless the mold is opened very wide. The above disadvantages have become a problem. The sagging of the sheet mentioned above is caused by the elongation of the softened sheet due to its own weight, and this elongation causes the thickness of the sheet to become uneven in the width direction, resulting in uneven wall thickness of the molded product. This can cause molding defects. These drawbacks of conventional equipment become more significant as the width of the sheet to be thermoformed increases; therefore, the sheet width that can be thermoformed using conventional equipment is at most 1 m.
Only up to a point. In addition, in conventional equipment, the sheet is heated and softened by heating the required area of the sheet at once in a heater for a certain period of time, then transferring it to the mold, and then processing the required area of the subsequent sheet until the molding is completed. This is done by repeating heating for a certain period of time. Therefore, microscopically, heating and forming are done in a batch manner, and it is especially difficult to maintain uniformity when the sheet area to be heated becomes large, and the center inevitably becomes hotter than the periphery. This makes it more difficult to obtain large molded products.

On the other hand, recently, in order to obtain a molded product having a staggered concavo-convex shape on both sides as shown in FIG. A pair of planted molds 3a,
3b is beginning to be used. The forming pins 1a and 1b of the forming molds 3a and 3b are arranged alternately, and the sheet 4 which has been softened by heating is
is elongated by the forming pins 1a and 1b to form a molded product as shown in FIG.

The above-mentioned mold is not one that molds a heat-softened sheet in close contact with the wall surface like a normal mold, but the desired molded product can be obtained by properly positioning the molding pins 1a and 1b. Since compressed air and vacuum means are not required, the manufacturing cost of the mold is extremely low. However, the forming pins 1a and 1b
In order to stretch the sheet 4 in this process, the homogeneity of the sheet is required to be more softened than in ordinary pressure forming or vacuum forming.

By the way, similar to conventional thermoforming equipment, when the heating device and the mold shown in FIG. Non-uniformity in thickness is a major cause of sheet tearing during molding and of molded products having extremely thin wall portions. Therefore, when using a mold as shown in Figure 2, the target sheet width is subject to greater restrictions than when using pressure forming or vacuum forming, making it extremely difficult to form large molded products. It is becoming difficult.

The present invention solves the above-mentioned conventional drawbacks,
In sheet thermoforming, it prevents uneven thickness in the width direction of the sheet due to elongation due to the sheet's own weight during heating and softening, and works well regardless of the target sheet width no matter what mold is used. The purpose is to make it possible to obtain molded products with high quality.

That is, in the present invention, if the sheet is heated and softened while being continuously transferred from the top to the bottom and molded at the bottom, the softened sheet sag will simply occur in the direction of sheet transfer, and the molding die will be removed. The opening/closing width of the sheet can be kept constant, and the elongation due to sagging of the sheet is compensated for by the sagging that occurs at the top. This was achieved by focusing on this.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to drawings showing one embodiment of the present invention.

3 shows the state immediately before molding, and FIG. 4 shows the state immediately after molding, and FIG. 4 is an enlarged sectional view of the mold.

The sheet 4 is pulled out from the raw fabric roll 5,
This device is transported almost vertically from the top to the bottom of the device, and the transport is accomplished by a transport means 6 such as a chain or belt that rotates while holding both side edges of the sheet 4. It is.

From above, a pair of heaters 7a,
7b and molds 3a and 3b are placed in sequence. The molds 3a and 3b have molding pins 1a and 1b similar to those shown in FIG. 2 embedded in substrates 2a and 2b, and are moved forward and backward by hydraulic devices 8a and 8b. . The hydraulic units 8a and 8b are attached to support plates 10a and 10b fixed to the transfer frame 9, and the moving frame 9 is moved up and down within the base frame 11 by hydraulic units 8c and 8d provided below. It is configured to be movable.

The molds 3a and 3b descend from the upper position shown in FIG.
After being cooled until it can maintain a certain shape, it enters the open state shown in FIG. 4, returns to the upper position shown in FIG. 3, and repeats the same operation thereafter. That is, the forming molds 3a and 3b move forward with the aid of the hydraulic machines 8a and 8b while descending at the same speed as the sheet 4, sandwich and elongate the sheet 4, and then descend together with the sheet 4, so that the sheet 4 is cooled. When the molding is completed, it retreats and rises, and the same operation is repeated again for the sheet 4 that is subsequently transported.

Here, the timing at which the molds 3a, 3b are opened and returned to the upper position is the timing when the molds 3a, 3b are returned to the upper position.
The sheet 4 sandwiched between the molds 3b and formed into a predetermined shape may be cooled to an extent that the shape can be maintained at any time.
In order to improve efficiency by shortening and speeding up and down reciprocation of the sheet 4, it is preferable to provide forced cooling means for the sheet 4 sandwiched between the molds 3a and 3b. In addition, only the portion of the sheet 4 held between the molds 3a and 3b can be sufficiently cooled in a short time, and the return time from the lower position of the molds 3a and 3b to the upper position and the transport speed of the sheet 4 are By appropriately adjusting the relationship, it is also possible to make the entire sheet 4 a molded product having a continuous uneven shape.
That is, by aligning the upper end of the previously formed uneven shape with the lower end of the subsequently formed uneven shape, it is possible to obtain a series of long molded products. Heat-retaining bellows cylindrical body 1 installed between the lower ends of the heaters 7a, 7b and the upper end of the moving frame 9
2 is particularly effective in such a case, since the sheets subsequently transferred from between the molding machines 7a and 7b are This is to prevent 4 from being cooled by direct contact with the outside air and becoming difficult to mold.

As mentioned above, in the apparatus of the present invention, it is preferable to provide forced cooling means for cooling the sheet 4 as quickly as possible after the sheet 4 is sandwiched between the molds 3a and 3b and formed into a certain shape. In the case of pressure-forming or vacuum-forming molds, this forced cooling means is relatively easy to use, such as by passing a refrigerant through the mold itself, since the entire sheet 4 is in close contact with the inner surface of the mold. It is possible to achieve quick cooling easily. However, as used in this example,
In the case of molds 3a and 3b as shown in Fig. 2, only the tips of the molding pins 1a and 1b contact the sheet 4, and most parts of the sheet 4 do not contact the molds 3a and 3b. Therefore, rapid cooling is difficult with the above-mentioned forced cooling means, and special measures must be taken. This will be explained with reference to FIG.

A large number of nozzle holes 13 are provided in each of the substrates 2a and 2b.
a, 13b are drilled. Each nozzle hole 1
3a, 13b are other forming molds 3a, 3b forming a pair.
The molding pins 1a and 1b face the tips of the molding pins 1a and 1b. The back surfaces of the substrates 2a and 2b are covered with covers 14a and 14b with a certain space between them. cover 14a,
Supply ports 15a and 15b to which flexible hoses (not shown) are connected are formed in 14b. Water is sent from the supply ports 15a and 15b, and the supplied water flows through each nozzle hole 13.
The liquid is ejected into the molds 3a and 3b via a and 13b.

In this way, the sheet 4 that has been stretched out by the forming pins 1a and 1b of both forming molds 3a and 3b is in an unstable state in which most parts maintain a constant shape only by the tension. However, water and cold air ejected from each nozzle hole 13a, 13b first hit the portion of the sheet 4 that is in close contact with the forming pins 1a, 1b, and are then slowly diffused. This allows rapid cooling without deforming the sheet 4. In particular, when water is used for cooling, it is preferable to eject water in the form of a mist in order to reliably prevent deformation of the sheet 4 due to the ejection pressure. Even when cooling with water, in the present invention, the sheet 4 is transported vertically, so the jetted water falls directly downward and accumulates in the molded recesses. There is no need to cool the subsequent unformed sheet. The receivers 16a and 16b shown in FIGS. 3 and 4 are for collecting falling water when cooling the sheet 4 with water, and return the falling water to the molds 3a and 3b. It is also possible to use the sequential order by sending .

Next, the advantages of the present invention will be explained.

First, according to the present invention, there is an advantage that even when a heated and softened sheet is stretched under its own weight, the thickness of the sheet hardly changes, and a good molded product can be obtained regardless of the sheet width. This will be explained with reference to FIG. 6. Since the sheet 4 is held substantially vertically, the sagging of the sheet 4 due to softening occurs as a downward shift of the sheet 4 around the center. Therefore, if point A shifts to point A', then A
Since the point B is refilled at a different position, there is almost no change in the wall thickness as a whole. In the present invention, since the sheet 4 is heated and softened while being continuously transported, such displacement of the sheet 4 occurs continuously, and except for a small area at the start and end of molding, it always occurs. It is possible to form a sheet 4 having a constant thickness and being softened by heating.

Second, since the sheet is heated by the heater while being transported at a constant speed, as long as the temperature in the width direction of the heater is constant, even if there is some variation in the temperature of the sheet in the transport direction, the sheet can be transported out of the heater. The heated sheet is in a certain heated softening state. Therefore, it is easy to adjust the temperature of the heater, and in combination with the above-mentioned uniform wall thickness, it is easy to obtain a good molded product.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a molded product, Fig. 2 is a sectional view showing an example of a mold, Figs. 3 and 4 are sectional views showing an embodiment of the present invention, and Fig. 5 is a sectional view showing an example of the mold. FIG. 6, an enlarged sectional view of the mold, is an explanatory diagram of the effects of the present invention. 3a, 3b: mold, 4: sheet, 5: raw roll, 6: transport means, 7a, 7b: heater.

Claims (1)

[Claims] 1 A heater that heats and softens the sheet, a pair of molds that are opened and closed with the sheet softened by the heater in between, and a sheet that is pulled out from the raw roll and held at both side edges and removed from the heater. It consists of a transfer means for transferring the sheet between molds, and the transfer means is arranged to continuously transfer the sheet almost vertically from the top to the bottom, and a number of nozzle holes are drilled in the upper part and the lower part of the heater. Each mold is provided facing the sheet, and the mold is lowered in a closed state in synchronization with the conveying speed of the sheet, and water is jetted into the mold through each nozzle hole, so that the sheet is A continuous thermoforming device characterized in that it is configured to be cooled until it can maintain a certain shape, then return to an open state, return to an upper position, and repeat the same operation.