JPH0532276Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is a method for controlling the wall thickness of a sheet material such as a synthetic resin sheet or film when vacuum forming the sheet material. This invention relates to a thickness control device.

[Prior Art] As is well known, the thickness of a vacuum-formed product made of a synthetic resin sheet or film can be adjusted to a desired thickness.
For example, in order to meet the demand for a uniform wall thickness regardless of the uneven shape, a desired part of a heat-softened sheet material may be heated to make it easier to thin the heat-softened sheet material during vacuum forming, or a desired part of a heat-softened sheet material may be heated. The thickness of the molded product is controlled by cooling the parts so that they are less likely to become thin during vacuum forming.

Conventional methods for controlling the wall thickness of such molded products include (a) a masking method, (b) a heater control method, (c) a plug assist method, and (d) an air heating/cooling method. In addition, to briefly describe each thickness control method, in the masking method (a), as shown in FIG. 6, between the sheet material 30 and the heater 31,
By placing the shielding plate 32 locally for a certain period of time,
This is a method of controlling heating of a portion that is likely to become thin during vacuum forming by blocking infrared rays 33 from the heater 31 to the sheet material 30.

Furthermore, as shown in FIG. 7, the (b) heater control method uses infrared rays by locally adjusting the voltage of the heater 36 for heating the sheet material 35.
This is a method of reducing the amount of No. 7 generated and controlling heating of parts that tend to become thinner during vacuum forming.

In addition, in the above-mentioned (c) plug assist method, a sheet material 42 heated and softened by a heater in the previous step is placed between a vacuum forming mold 40 and a plug 41 above it, as shown in FIG. After lowering the plug 41 to pre-tension the sheet material 42 as shown in FIG.
This is a method of adjusting the uneven thickness of the vacuum-formed product 43 by pre-tensioning the sheet material 42 by the plug 41 in a molding method in which finishing is performed in a vacuum by raising the pressure.

In addition, in the air heating/cooling method (d), as shown in FIG. 11, controlled air such as heated air or cooling air is partially applied to the sheet material 45 heated and softened by a heater in the previous step from an air nozzle 46. This is a method of adjusting the uneven thickness of a vacuum-formed product by spraying the material and partially heating or cooling a desired portion of the sheet material 45, that is, a thickness control portion.

[Problems to be solved by the invention] The conventional wall thickness control method described above has the following problems. namely (a) masking method;
(b) In the heater control method, since the ambient temperature rises while the sheet materials 30 and 35 are being heated and softened, the sheet materials 30 and 35 are
It is difficult to perform accurate temperature control on the wall thickness control portion of 0.35.

In addition, in the above (c) plug assist method, the plug 41
Since the plug 41 contacts the surface of the sheet material 42 during pre-tensioning of the sheet material 42, the molded product 43
Appearance is affected.

Furthermore, the air heating/cooling method (d) is commonly used as a method for controlling the wall thickness of vacuum-formed products, but since the control air from the air nozzle 46 is diffused as shown by the arrows in FIG. , the heating or cooling effect is halved, and it is difficult to locally heat or cool only the necessary portion, that is, the thickness control portion of the sheet material 45.

The purpose of the present invention is to solve the problems in the prior art as described above, to be able to locally heat or cool the thickness control part of the sheet material, to accurately control the temperature of the control part, and to form An object of the present invention is to provide a wall thickness control device for vacuum forming that hardly affects the appearance of a product.

[Means for Solving the Problems] The wall thickness control device for vacuum forming of the present invention that solves the above-mentioned problems blows control air at a predetermined temperature to the thickness control portion of a sheet material such as a synthetic resin sheet or film. It is equipped with an air supply pipe and an air recovery pipe that recovers the blown out control air.

[Function] According to the above means, the thickness control portion of the sheet material is heated or cooled by jetting control air at a predetermined temperature from the air supply pipe to the thickness control portion of the sheet material. The control air is then recovered through the air recovery pipe, reducing diffusion to the surroundings.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In FIG. 2, which schematically shows the vacuum forming machine, the vacuum forming machine 1 includes a clamping device 3 for clamping a sheet material 2 such as a thermoplastic synthetic resin sheet or film in a stretched state, and a clamping device 3 below the clamping device 3. The installed lifting cylinder 5, a mold 7 attached to the upper end of the cylinder 5 via a mold mounting table 6, and an intake port 8 of the mold 7 are communicated with each other via an intake pipe 9 and a vacuum tank 10. A vacuum pump 11 is provided, and a pair of upper and lower infrared heaters 13 are arranged on the sides of the clamp device 3 and are moved upward and downward of the sheet material 2 when the sheet material 2 is heated.

In the vacuum forming machine 1, a wall thickness control device 15 is arranged above the sheet material 2. Note that the thickness control device 15 is provided so as to be movable horizontally and vertically via a moving means (not shown), and is movable to a position facing the thickness control portion of the sheet material 2 and from above the sheet material 2. It is now possible to move away and move to a retreat position.

Next, the wall thickness control device 15 will be described in detail with reference to FIG. 1, which shows a sectional view thereof. This wall thickness control device 15 has a substantially cylindrical double inner and outer pipe structure. The inner pipe is set as an air supply pipe 16 with its tip end serving as a nozzle 17, and the outer pipe is set as an air recovery pipe 1.
It is set to 8. Note that the tips of the air supply pipe 16 and the air recovery pipe 18 are bent downward.

The base end of the air supply pipe 16 is connected to an air supply source 20 that can supply control air A adjusted to a predetermined temperature, and the control air A is supplied to the nozzle 1 at the tip.
It erupts from 7.

Further, the base end of the air recovery pipe 18 is connected to the air recovery pipe 1
8 and the air supply pipe 16, an air intake source 21 for recovering the control air A;
It is connected to the. The distal end of the recovery pipe 18 is expanded to a large diameter as a hood 19, and surrounds the nozzle 17 of the air supply pipe 16. In addition,
The end of the hood 19 of the air recovery pipe 18 projects slightly beyond the end of the nozzle 17 of the air supply pipe 16.

In the vacuum forming machine 1 equipped with the thickness control device 15 described above, in order to form the sheet material 2 under vacuum, first the sheet material 2 is is clamped in an expanded state by the clamping device 3.

Next, the heater 13 is moved and positioned above and below the sheet material 2. In this state, the sheet material 2 is heated and softened by the heater 13. This state is shown in FIG.

After the sheet material 2 is heated and softened, the heater 13 is moved to the standby position.

Thereafter, the thickness control device 15 is moved to the standby position, and the nozzle 17 of the air supply pipe 16 is directed toward the thickness control portion of the sheet material 2. This state is shown in FIGS. 1 and 4.

In this state, as shown in FIG. 1, control air A at a predetermined temperature supplied from the air supply source 20 through the air supply pipe 16
The liquid is ejected from the nozzle 17 of No. 6 toward the thickness control portion of the sheet material 2. As a result, the thickness control portion of the sheet material 2 is controlled to a predetermined temperature, that is, heated or cooled. Specifically, if you want the wall thickness control part to become thinner easily during vacuum forming (described later), it is heated to raise the temperature of that part, and if you want to make it less likely to become thinner during vacuum forming, it is cooled to raise the temperature of that part. Can be lowered. This controls the wall thickness of the molded product.

The control air A is then recovered through the air recovery pipe 18 by the suction action of the air intake source 21. Note that the flow of control air A is indicated by arrows in FIG.

Therefore, the control air A ejected from the nozzle 17 of the air supply pipe 16 is recovered from the hood 19 of the air recovery pipe 18 without diffusing into the surrounding area. Therefore, the thickness control portion of the sheet material 2 can be locally heated or cooled, and the temperature control can be performed with high precision.

Furthermore, unlike the conventional plug assist method, the wall thickness control device 15 does not pretension the sheet material 2, so that the wall thickness can be controlled with almost no effect on the appearance of the molded product. In addition, in controlling the wall thickness, it is desirable that the hood 19 of the air recovery pipe 18 be opposed to the sheet material 2 with a slight gap therebetween.

Furthermore, in this example, the air intake source 21 is connected to the air recovery pipe 18 to actively recover the control air A, so that the diffusion of the control air A from the gap between the sheet material 2 and the air recovery pipe 18 is prevented. The heating and cooling effects of the control air A can be maximized.

When the processing by the wall thickness control device 15 is completed as described above, the device 15 is moved to the standby position, and the mold 7 is raised by extending the lifting cylinder 5. At the same time, the sheet material 2 is vacuum formed by the vacuum pump 11. Note that the state in which the mold 7 is in the middle of rising is the fifth stage.
As shown in the figure.

Thereafter, the lifting cylinder 5 is shortened, the mold 7 is returned to the standby position, the mold is released, and the molded product is taken out from the clamp device 3.

Note that by forming the air supply pipe 16 from a material with low thermal conductivity, temperature changes in the control air A fed into the air supply pipe 16 can be prevented. Alternatively, the air intake source 21 in the embodiment described above may be eliminated, and the control air A may be discharged to the outside through the air recovery pipe 18 using the air supply function of the air supply source.

[Effects of the invention] According to the wall thickness control device for vacuum forming of the present invention, it is possible to locally heat or cool the thickness control portion of the sheet material during vacuum forming, and to precisely control the temperature of that portion. can. Furthermore, unlike the conventional plug-assist method in which sheet materials are pre-stretched, wall thickness can be controlled with almost no effect on the appearance of the molded product.

[Brief explanation of the drawing]

Figures 1 to 5 show an embodiment of the present invention.
Fig. 1 is a sectional view of the wall thickness control device, Fig. 2 is a side view schematically showing the vacuum forming machine, Fig. 3 is a side view showing the heating state of the sheet material, and Fig. 4 is the wall thickness control state. FIG. 5 is a side view showing a state in the middle of vacuum forming. Figures 6 to 11 show conventional examples; Figure 6 is a cross-sectional view showing the masking method, Figure 7 is a cross-sectional view showing the heater control method, and Figures 8 to 10 are the molding process of the plug assist method. FIG. 11 is a cross-sectional view showing the air heating/cooling method. 2...Sheet material, 16...Air supply pipe, 18...
...Air recovery pipe.

Claims (1)

[Scope of utility model registration request] Wall thickness in vacuum forming, which is equipped with an air supply pipe that blows out control air at a predetermined temperature to the wall thickness control portion of a sheet material such as a synthetic resin sheet or film, and an air recovery tube that collects the control air that has been ejected. Control device.