DE1180118B - Device for carrying out a process for vacuum deformation of foils in sheet or web form made of thermoplastic material - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Cl .:

Number: File number: Registration date: Display day:

German class: 39 a2 -17/02

1180118
T17358 X / 39 a2
October 19, 1959
October 22, 1964

In the main patent application are a method and an apparatus for vacuum forming of Foils in sheet or web form made of thermoplastic material by means of an above the sheet or the path arranged evacuable tool described. After the main patent application the film to be deformed is to be heated outside of the molding tool until, as a result of the A sack-like sag occurs due to the film's own weight; in this state the film is placed under the Deforming tool guided, whereupon the molding tool and the film through a shock-like vertical Relative movement with the formation of an air cushion for an airtight seal of the mold cavity are moved against each other.

The invention represents an improvement and further development of the subject matter of the main patent application For the subject of the main patent application, it is essential that the film made of thermoplastic material is heated so far that it is in the entire area of the to deforming surface almost completely loses its elastic properties and reaches the limit of plasticity Is brought into a state in which it no longer has any significant elasticity of its own. For this, it is essential that the entire area of the film to be deformed is appropriately set local heating is subjected.

The invention is therefore based on the object of the horizontally suspended film to be heated Heat supplied in the form of infrared rays in their local intensity distribution for generation the largest possible, even sack-like sag while maintaining transportability to regulate the slide.

It is already known that the local intensity distribution of infrared rays for heating the im Thermoforming process to be deformed plastic film thereby to regulate that over the entire radiator surface distributed infrared lamps or other radiator elements partly switched on and partly switched on according to the desired intensity distribution stay off. This known type of local intensity control by switching it on or off of individual emitters or emitter groups is by far not precise and fine enough to detect the to regulate the precise and safe formation of a sack-like sag and the proper Ensure the deformation process after the main patent application. The invention therefore proposes to solve the problem posed, a device for carrying out a method for vacuum forming of foils in sheet or web form made of thermoplastic material

Addition to registration: T14382 X / 39 a—
Interpretation document 1126 589

Applicant:
AIf ons Thiel, Mainz, Raimundistr. 11

Named as inventor:
Alfons Thiel, Mainz

Claimed priority:

V. St. v. America November 4th 1958
(771864)

to build the heating device from a plurality of infrared radiators, which are within one of the total effective range the heater housing surrounding the heating device can be displaced relative to one another in a plane parallel to the suspension of the film are stored.

Due to the displaceable mounting of radiator elements, in particular tubular infrared radiators, all desired forms of intensity distribution can be set practically with absolute precision. In particular, the disturbances of the intensity distribution occurring at the edge can also be identified compensate by simply adjusting the mutual distance between the radiator elements. The intensity distribution can be adjusted so precisely by empirical readjustment that even slight differences can be compensated in the beam properties of the individual radiator elements. the Device according to the invention has the advantage that it is much simpler than that known radiant heating surfaces. Above all, the heating device according to the invention does not become special Effort for electrical switches, etc. required. The heating device according to the invention can in be constructed particularly simple embodiment of tubular infrared radiators, which are in extend their length over the entire length or the entire width of the radiator housing and transversely to are mounted displaceably in their longitudinal direction within the radiator housing.

If at least one heater housing is above and at least one heater housing is below the

409 708/398

heating foil is used, it is particularly advantageous within the scope of the invention to use the tubular Radiators of the upper radiator housing with their longitudinal direction transverse to the longitudinal direction of the radiators in the lower To lay the emitter housing.

In order to use infrared rays of greater wavelengths when the film is heated in several stages in the first heating stages than in the last heating stage, the tubular infrared heater can be used in the last Heating level must be heated up more than in the heating levels arranged in front of it. This achieves that the infrared rays of greater wavelength, which have a greater penetration into the material have to warm up the film from the inside, while the outer surfaces are secured against overheating are. Only then should the outer surfaces be softened for the final heating-up, see above that very soon the sack-like sag can develop in the last heating stage. Some embodiments of the invention are shown in the drawing, for example.

F i g. Fig. 1 shows a vacuum forming apparatus with a single stage heater according to the invention; F i g. 2 shows the in FIG. 5 used heating device according to the invention without the actual deformation device in perspective view; F i g. 3 shows a partial representation of the displaceable Storage of heating elements;

F i g. 4 shows a vacuum forming device with a two-stage heating device according to the invention. According to FIG. 1, the deformation device 1 can be constructed in the same or a similar manner as this in A b b. 6 of the main patent application is indicated. Below the mold 1 is also in In this example, a clamping frame 21 is mounted so that it can be pivoted downward about an axis 2 in order to be able to with Transport of the sack-like sagging belt 2 made of plastic, for example polyvinyl chloride, polyethylene Od. Like. To release the path of movement for this tape 2 completely. This is even more important than it is at the process according to the main patent application and the present invention essentially depends on the plastic strip 2 to be deformed as uniformly and as possible in the area to be deformed to be heated to such an extent that it almost completely loses its elastic properties and its residual elasticity just enough to prevent the sagging tape from tearing. The invention is based on the finding that the temperature resistance of a molded plastic article is at the temperature at which the molding of this article was carried out. It is therefore the method according to the invention is based on the object of the plastic strip 2 to be deformed Bring the highest possible temperature and deform at the highest possible temperature. A deterrent of parts of the heated belt 2, for example by contact with the tenter frame 21, would lead to the fact that not only the deformation itself would be called into question and under certain circumstances the sagging band 2 could tear, but it is above all in any case the temperature resistance of the products made from such quenched tape parts are greatly reduced.

To solve the problem, the plastic tape before deforming to the temperature that has just been reached is still permissible for the strip material to be heated, according to the invention a regulation of the Proposed local intensity distribution of the infrared rays used for heating. To do this, in Direction of travel of the strip 2 immediately in front of the molding tool 1 in the direction shown in FIG. 1 shown example an infrared radiator heating device 14 acting from above and below is provided. This infrared heater 14 consists of a radiator housing 101 arranged above the belt 2 and a

ίο heater housing arranged below the belt 102. Each of these radiator housings 101 and 102 contains a plurality of tubular ones known per se Heating elements 103, which are operated with electrical current, as taken from any conventional lighting network can be.

In the embodiment of the invention shown, the heating elements 103 are arranged in the upper radiator housing 101 transversely to the direction of travel of the strip 2 and extend over the entire width of the radiator housing 101. In the lower radiator housing 102, however, the heating elements 103 are arranged and extend along the direction of travel of the strip 2 extending over the entire length of the radiator housing 102. As in particular FIG. 2 shows, the outer heating elements 103 α are arranged more closely than the inner heating elements 103 A in order to compensate for edge losses of the radiator housing 101 and 102, respectively. This gives the possibility of setting the heating elements 103 at such a mutual distance within a horizontal plane in such a way that the intensity distribution of the infrared radiation on the surface of the irradiated strip becomes such that it allows the greatest possible sagging of the strip and the highest possible heating temperature of the material . However, apart from the above-mentioned narrower arrangement of the outer heating elements 103 α, no general rule for the heating element arrangement can be established; rather, the most favorable setting of the heating elements 103 can be determined by a person skilled in the art immediately before the entire system is started up by the fact that the stationary belt takes into account the desired Duration of the feed intervals a uniform, symmetrical sag of the material is generated. Such a uniform sag, which is as large as possible, indicates that the temperature is practically the same over the entire irradiated surface.

This empirical setting of the irradiation intensity is therefore inevitable because the setting that occurs local temperature distribution largely also on the thickness of the plastic tape 2 and the Type of plastic material is dependent.

The setting of each heating element 103 transversely to its longitudinal direction within the radiator housing 101 and 102 is made possible according to the invention, for example, by mounting the heating elements 103, as shown in FIG. 3 is shown. In this example shown, the heating elements 103 are with their front connection caps 104 or 105 between each two connected to electrical voltage and contact strips 106 clamped. These strips 106 are designed to be resilient over their entire length or resiliently mounted, so that a mere displacement of the end-face connection caps 104 and 105 is sufficient, to move the heating elements 103 transversely to their longitudinal direction and at the same time the electrical Ensure connection.

In the example of FIG. 4, a multi-stage heating device 14 is provided, namely in this specific example a two-stage heating device, but more than two stages can also be provided. The different heating stages follow one another directly, but they are designed independently of one another. In the example of FIG. 4, the two heating stages 111 and 211 are constructed from the same components as were explained in connection with FIGS. 1 to 3. The arrangement here is such that the tubular heating elements 103 in the upper radiator housing 101 of the last heating stage 111 extend transversely to the direction of travel of the strip 2 and in the lower radiator housing 102 of the last stage 111 extend along the direction of travel of the strip. In the preceding heating stage 211 , the reverse arrangement is made, that is, the tubular heating elements 203 extend in the upper radiator housing 201 along the direction of travel of the strip 2 and in the lower radiator housing 202 transversely to the direction of travel of the strip 2.

In the present case, the two stages are regulated in such a way that the temperature in the second stage 111 is noticeably higher than in the first stage 211 . As a result, the infrared radiation of the first heating stage 211 is given a considerably longer wavelength in order to initially heat the plastic strip more intensely in its inner material than on its surface. As a result, the plastic strip is heated to a relatively large extent from the inside, without the outer material areas, which significantly influence the sag resistance of the strip, being significantly softened. The plastic band can therefore absorb the relatively large amount of heat supplied to it without the material sagging. As in the case of the second stage 111, the amount of heat supplied in this way can be regulated in its local distribution so that the heated area of the strip assumes the temperature as uniformly as possible. The preheating in the first stage 211 can be controlled in such a manner that the tape 211 leaves this preheating stage in a state that is at ground just prior to the formation of a bag-like slack. This sack-like sag is then formed in the second heating stage 111 , in which infrared radiation of shorter wavelength is used, the effect of which then extends essentially to the belt surfaces. In order to ensure correct transport of the strip from the first stage 211 to the second heating stage 111 , a guide roller 212 can be provided which extends transversely over the entire strip width and is rotatably mounted between the two heating devices 111 and 211 . This guide roller can be formed on its surface with low thermal conductivity. In addition, the preheated film is not quenched because the belt surfaces are kept relatively cool and there is no great difference in temperature between the surface of the belt 2 and the surface of the roller 212 .

In addition to the illustrated embodiments of the invention, there are further embodiments conceivable without departing from the essence of the invention.

Claims (5)

Patent claims: 1. Device for carrying out a method for vacuum deformation of foils in Sheet or sheet form made of thermoplastic material by means of an above the sheet or the evacuable tool arranged on the web, in which the film to be deformed outside of the mold is heated so far that, according to the weight of the film, a sack-like sag occurs and the film in this state under the deformation tool is guided and in which the molding tool and the film through a shock-like vertical Relative movement with the formation of an air cushion for the airtight closure of the mold cavity are moved against each other, according to patent application T 14382 X / 39 a, the the horizontally suspended film to be heated, heat supplied in the form of infrared rays in their local intensity distribution to generate as large a uniform as possible bag-like sag is regulated while maintaining the transportability of the film, characterized in that the heating device consists of a plurality of infrared radiators is constructed, which delimit the total area of action of the heating device within a Radiator housing against each other in a plane parallel to the suspension of the film are slidably mounted. 2. Apparatus according to claim 1, characterized in that the heating device consists of tubular infrared emitters is constructed, which extends in its length over the entire length or the entire width of the radiator housing and extend transversely to its longitudinal direction within of the emitter housing are stored. 3. Apparatus according to claim 2 with at least one radiator housing above and at least one heater housing below the film to be heated, characterized in that that the tubular radiators of the upper radiator housing with their longitudinal direction transverse to Longitudinal direction of the radiators are laid in the lower radiator housing. 4. Device according to one of claims 1 to 3, characterized in that for multi-stage Heating the film above and, if necessary, below the film one of the number the number of heater housings of the same structure corresponding to the heating stages is, whereby the radiators in each individual radiator housing are independent of the radiators of others Emitter housing are mutually displaceable. 5. Apparatus according to claim 4, characterized in that for generating longer wave Radiation in the first heating stage or the tubular infrared heater in the last Heating level are heated up more than in the heating levels arranged in front of it. References considered: British Patent No. 569,340. 1 sheet of drawings 409 708/398 10.64 © Bundesdruckerei Berlin