ES2367482T3 - THERMOCONFORMING INSTALLATION FOR THE PRODUCTION OF MOLDED BODIES FROM A PLASTIC SHEET, AS WELL AS PROCEDURE FOR THEIR PRODUCTION. - Google Patents

Abstract

Installation (1) of thermoforming for the production of molded bodies from a plastic sheet (50), such as cups, containers, lids, food containers or the like, with a transformation station that presents a tool (20) of two-part forming, in which the two-part forming tool (20) has an upper tool table (28) that can be set in an adjustable manner with an upper tool (30) with pre-stretching means (92) mounted in a manner movable therein and a mobile lower tool table (32) with a lower tool (34) with cavities, the mobile lower tool table (32) being guided by a guiding unit (42) and being able to move by means of a drive unit with respect to the upper tool table (28) to and from it, in which the upper tool table (28) has a first drive unit (26) associated therewith to place the m that upper tool (28) in position with respect to the upper dead center of the lower tool table (32) in correspondence with the molded body to be produced in each case, and in which the tool table (28) upper has a second drive unit (88) associated therewith to drive the prestressing means (92) movably mounted on the upper tool, characterized in that the second drive unit (88) acts through a rod (100 ) of thrust, a rocker lever (102) and a pressure rod (106) on the prestressing means (92) in the upper tool (30), preferably by means of a support point B0 of the rocker lever (104) displaceably designed (142).

Description

The present invention relates to a thermoforming installation for the production of molded bodies from a plastic sheet, such as glasses, containers, lids, food containers or the like, with a transformation station presenting a forming tool for two parts, according to the preamble of claim 1, as well as to a process for the production of such molded bodies according to the preamble of claim 6.

Thermoforming facilities have been disclosed in practice in different variants and embodiments. In this regard for the production of articles or molded bodies in the form of a container from a thermoplastic plastic a two-part forming tool is used. One half of the mold, the so-called upper tool, is fixed to the upper tool table and connected with it as a rule so that it can be fixed in an adjustable way with the frame or frame of the thermoforming installation, so that the upper tool It can be adjusted to the molded body that will be produced in each case. The other half of the mold, the so-called lower tool, can be guided mobilely in the frame or frame of the thermoforming installation.

To shape the molded bodies the mold halves, that is the upper tool and the lower tool, are in a closed position facing each other. Between the upper tool and the lower tool is a plastic sheet with preheated frequency and therefore can be deformed in a plastic way, which is fed in most cases in the form of a sheet band from a roller of Feeding rhythmically.

In the deep drawing operation the plastic sheet is hooked between the upper tool and the lower tool and is thus fixed in place. The plastic sheet is then introduced through the means of prestressing the upper tool into the cavities of the lower tool, while the edge of the molded body to be generated is still fastened between the upper tool and the lower tool. By generating a negative pressure in the cavities or by introducing air, the sheet rests on the internal walls of the cavities in the lower tool and thus adopts the desired shape.

After sufficient cooling of the plastic sheet by contact with the surface of the optionally cooled tool optionally the separation of the molded bodies with respect to the plastic sheet occurs. For this, the lower tool moves upwards approximately the value of the sheet thickness. Corresponding cutting edges of the two-part forming tool in this case cut each of the molded bodies from the sheet web. The remaining reticule is often fed rhythmically to a winding unit.

To extract the molded bodies from the cavities the lower tool then moves away from the upper tool and is pivoted about its longitudinal axis such that the lower tool points to a stacking unit and thus the molded bodies can be transferred to the stacking unit.

Examples of thermoforming facilities discussed above, known in practice are described for example in US 6,135,756 or DE 33 46 628 A1.

These known thermoforming installations, however, have the essential economic disadvantage that only reduced duty cycle frequencies, for example up to about 30 duty cycles per minute, can be performed with them. Higher duty cycle frequencies are not possible without damaging moving parts. However, these low work cycle frequencies are no longer acceptable in view of the high prevailing price pressure.

The drives used in the thermoforming facilities known for the prestressing means disposed in a mobile manner in the upper tool are additionally disadvantageous, because with them only low duty cycle frequencies can also be carried out, for example up to about 30 duty cycles per minute. . In addition, in the known thermoforming installations, the lack of precision in the adjustment capacity or the adaptability of the upper tool with respect to the molded bodies to be produced is disadvantageous.

The thermoforming installation described in DE 33 46 628 A1 operates in detail with a two-part forming tool, the upper tool being made such that it is fixed to the frame and the lower tool in a mobile manner. The lower tool is oriented for closing or opening in a combined lifting and pivoting movement towards the upper tool and away from it and at the same time towards a stacking unit and again oriented away from it towards the upper tool. The lifting and pivoting movement of the lower tool is generated by an articulated lever-lever disc mechanism. The lower tool will therefore move vertically and simultaneously pivot with respect to its own longitudinal axis.

The combination that is used in the thermoforming installation known from DE 33 46 628 A1 of an articulated cam disc mechanism in connection with a cam disc drive is configured in a very complex manner. In this regard, the cam disc drive already has as such the systematic disadvantage that only limited forces can be transmitted with it. In addition, with a cam disk drive, high duty cycle frequencies cannot be performed. In addition, cam disc drives tend to wear out quickly, so maintenance of them often must be performed, which increases the operating costs of such a thermoforming installation unacceptably. In addition, the thermoforming installation discussed in this case according to DE 33 46 628 A1 with its complex articulated lever mechanism presents a group of parts that in the same way, conditioned by the system, only allows low working cycle frequencies.

From DE 33 46 628 A1 no more detailed information can be derived for the configuration of the drive of the prestressing means. Therefore, it must be assumed that the drive of the prestressing means not discussed further in this document does not allow higher work cycle frequencies, such as the drive for the lower tool, whose work cycle frequency has already been previously determined to be too high. low.

The thermoforming installation according to US 6,135,756 also presents in detail a two part forming tool. The guiding unit is also combined in this case with the drive unit of the lower tool table or the lower tool and generates a combined lifting and pivoting movement of the lower tool by means of a cam-crank mechanism. , there are two cam-crank disc mechanisms arranged in each case on the external front sides of the lower tool. In this respect, the lower tool has on its external sides in each case three plugs, which run in the associated groove curves fixed to the frame. These groove curves have an extremely complex geometry and are designed so that the lower tool when opening the forming tool can move from the upper tool down and pivot, to orient it towards a stacking unit and be able to swing it again from it. Since the complex geometry of the groove curves is not suitable for transmitting the forces necessary to separate the molded bodies formed with respect to the plastic sheet, additional cam discs are provided, with which the forces necessary for this will be transmitted. However, the separation operation that can be achieved with this remains the cutting or crushing. You can't talk about a print.

Regardless of this, with the groove curve guides that can be adjusted to each other only very hard and geometrically complex, the high work cycle frequencies required today are ruled out.

The drive of the prestressing means is described in US 6,135,756 as a combination of toothed rod and toothed wheel. With this, the high working cycle frequencies required for the economic operation of a modern thermoforming installation cannot be realized. Because in order to achieve a high repeatable work cycle frequency in a durable way, not only high work cycle frequencies are necessary during the closing and opening of the forming tool, but the lifting movement of the prestressing means must also be increased in parallel to it at least to the same extent, so that the prestressing means can be operated at the same rate, as the forming tool.

In addition, by practice, drives of the prestressing means have been disclosed, in which the prestressing means are actuated by means of ball screws. With the ball screws of this type, the high required duty cycle frequencies cannot be achieved. In addition, the ball screws are too expensive, need maintenance and have as an additional disadvantage long inactive periods.

An additional drive unit for an auxiliary stretching means for the mechanical forming of a sheet

or heated plastic plate is disclosed in EP 1 046 489 A2.

Document US 4,565,513 A further discloses a thermoforming installation, in which the lower table is operated by means of a cranked lever drive to open and close, as well as to expel molded bodies.

Document DE 199 48 768 C1 finally discloses a thermoforming installation for the production of molded bodies from a plastic sheet according to the preambles of independent claims 1 and

6. The device described in this document for forming and stamping containers from a thermoplastic plastic sheet has a two part forming tool with an upper and a lower tool table.

Starting from the state of the art mentioned above, the objective of the present invention is to improve the known thermoforming facilities in such a way that essentially higher working cycle frequencies can be achieved and thereby enabling economic operation of such improved thermoforming facilities. . Furthermore, the objective of the present invention is to propose an economical process for the production of molded bodies from a plastic sheet.

This objective is solved with respect to the device by means of the features of claim 1.

With respect to the procedure, the objective is solved by the features of claim 6.

According to the invention, a thermoforming installation is proposed for the production of molded bodies from a plastic sheet, such as glasses, containers, lids, food containers or the like, with a transformation station presenting a two-way forming tool. parts In this case, the two-part forming tool has an upper tool table that can be set in an adjustable way with a top tool with pre-stretching means movably mounted thereon and a mobile bottom tool table with a bottom tool with cavities The mobile lower tool table is guided in this case by means of a guiding unit and can be moved by means of a drive unit with respect to the upper tool table to and from it.

In this case, it is foreseen for the first time that the upper tool table has a first drive unit associated therewith to place the upper tool table in position with respect to the upper dead center of the lower tool table in correspondence with the molded body to be produced in each case, and that the upper tool table has a second drive unit associated therewith to drive the prestressing means movably mounted on the upper tool, the second drive unit acting through of a push-pull rod, a rocker lever and a pressure rod on the prestressing means in the upper tool, preferably by means of a pivotally designed pivoting lever support point.

With respect to the drives of the prestressing means known by the prior art, the decoupling according to the invention of the actuation of the prestressing means, correspondingly providing a separate drive for it, as well as an additional separate drive for regulating or adjusting The superior tool with respect to the molded bodies that are to be produced before their final fixation before the start of the respective production process, offers the advantage that these two drives can be optimized independently of each other. Therefore, a drive as suitable as possible to regulate can be provided.

or adjust the upper tool once before the start of the respective production process, which then advantageously does not necessarily have to perform at the same time also the high work cycle frequencies required during the actuation of the prestressing means, but can be selected especially with regard to the precision and repeatability of an exact regulation of the upper tool table. Accordingly, the drive of the separate prestressing means can be selected with respect to the high duty cycle frequency required and optimized accordingly.

Although a separate optimization of this type of separate drives obviously increases the number of parts, on the other hand, it offers the incalculable advantage that both drives can be maintained in themselves with a construction as simple as possible and that they can finally return to Set up economically.

As the second drive unit acts through the push rod, the rocker lever and the pressure rod on the prestressing means in the upper tool, an especially simple constructive solution is obtained. In this regard, in a particularly preferred manner, it is provided that the rocker lever has a displaceably designed support point, so that its lever arms and thus their force ratios can be adjusted to the respective application case. The operation of the prestressing means through a push rod, a tilting lever and a pressure rod makes it possible to arrange the second drive outside the area of the upper tool in particular advantageously not directly thereon, so that when using a hydraulic drive, an insignificant outlet that cannot always be completely discarded from hydraulic oil is no longer important, because it cannot advantageously drip onto the strip of foil. Furthermore, additionally advantageously, the second drive for the prestressing means in the transmission of its actuating forces through a push rod, a tilting lever and a pressure rod to the prestressing means can be arranged laterally with respect to the upper tool table in such a way that the second drive with the upper tool table does not move with it and therefore with respect thereto, so that the second drive exclusively controls the movement of the prestressing means and by both particularly advantageously it can be optimized with respect to high work cycle frequencies.

Additionally, it is advantageous that the offset of the support point can be used to adjust a variable path of the prestressing means. The displacement of the support point advantageously results in a constant travel of the drive and a continuous adaptation of the path of the prestressing means, so that the upper dead center of the prestressing means remains constant and the lower dead center can be adapted according to the molded body height or product.

Embodiments and additional advantageous aspects of the present invention are the subject of the dependent claims.

In a preferred embodiment of the thermoforming installation according to the invention, the first drive unit for positioning the upper tool table is configured as an electric servomotor. This offers the advantage of an exact regulation capacity, being able to freely select its speed profile. Thus, fast feed movements can be achieved to overcome large adjustment paths and especially slow and precise feed movements for exact positioning of the upper tool table in the millimeter or even centimeter range according to the desired accuracy. In addition, electric servo motors are available in the market in any necessary design variant.

According to a further preferred embodiment of the thermoforming system according to the invention, it is provided that this first drive unit through a synchronization shaft act in conjunction with, for example, endless screws / wheels arranged thereon through two spindles of associated adjustment, which in turn act on the upper tool table so that it can move in its horizontal orientation vertically up and down, so that the upper tool table can be adjusted to the molded body to be produced in each case . With this, the above-mentioned advantage of a freely selectable speed profile of an advantageous servo motor can be advantageously, synergistically and optimally translated in both large feed movements and small or precise regulation movements.

In a further preferred embodiment of the thermoforming installation according to the invention, the second drive unit of the upper tool table has a hydraulic drive or a crank drive actuated by means of an electric servomotor to drive the prestressing means. In both cases, especially high duty cycle frequencies can be achieved. These high work cycle frequencies can amount to at least 40 cycles, 50 cycles or more cycles. Thus, with a hydraulic actuation of the prestressing means, forces of the prestressing means of at least 40 kN can also be advantageously obtained with a working travel of at least 120 mm and a displaced mass of at least 200 kg, increasing the time to cover the 120 mm working path less than 200 ms.

In a further preferred embodiment of the thermoforming installation according to the invention, the prestressing means can be operated by means of the second drive device such that a travel of at least 120 mm or more can be made in less than 300 ms, preferably less than 200 ms. Thus, duty cycle frequencies of more than 60 cycles per minute can be obtained advantageously, so that with a thermoforming installation according to the invention, which for example provides a crank drive for a linearly guided lower tool table, in total high work cycle frequencies that until now were not considered realizable can be achieved.

The above objective is solved with respect to the process by means of the features of claim 6. In this regard, a process for the production of molded bodies from a plastic sheet, such as glasses, containers, lids, containers, is proposed for the first time. for food or the like, with a thermoforming installation according to the preamble of claim 1, which has the following steps: a) feeding a plastic sheet into the two part forming tool by means of a chain transport, b) tensioning the plastic sheet in the area of the forming tool, c) closing the forming tool by guiding the mobile lower tool table by means of the guiding unit and actuating it by means of the drive unit in such a way that it move with respect to the upper tool table towards it, d) produce the molded bodies with the forming tool ce Rotate, e) open the forming tool by guiding the mobile lower tool table by means of the guiding unit and by actuating it by means of the drive unit so that it moves with respect to the upper tool table from the same, and f) ejecting the molded bodies optionally towards a stacking unit, being provided for the first time to place the upper tool table by means of a first drive unit associated thereto in its position with respect to the upper dead center of the lower tool table in correspondence with the molded body to be produced in each case, and that the prestressing means movably mounted on the upper tool can be operated by means of a second drive unit, the drive unit acting through of a push-pull rod, a rocker lever and a pressure rod on the prestressing means in the tool lie upper preferably by means of a pivotally designed pivoting lever support point.

The advantages related to this have been discussed previously with respect to the device.

Additional advantageous embodiments of the process are discussed in the dependent claims.

The invention is explained in detail below with exemplary embodiments by means of the figures of the drawings. Sample:

Figure 1 a top view of an embodiment of a thermoforming installation according to the invention Figure 2 a side view of the exemplary embodiment represented in Figure 1 of a thermoforming installation according to the invention; Figure 3 shows a detailed view of the drive shown from the side for pivoting the rail-guide arrangement of the variant shown in Figures 1 and 2 of a thermoforming installation according to the invention; Figure 4 a section along the line X-X of Figure 3; Figure 5 the variant shown in Figures 1 to 4 in an operating arrangement in an inclined position; 6 shows a schematically simplified sketch of an exemplary embodiment of a drive according to the invention for the operation of the prestressing means in the thermoforming installation according to the invention according to Figs. 1 to 5; Figure 7 a schematically simplified sketch of an exemplary embodiment that clarifies how the drive shown in Figure 6 can be configured; Figure 8 an alternative embodiment of the actuation of the prestressing means according to the invention of the thermoforming installation according to Figures 1 to 5; 9 shows a further variant of the alternatives shown in FIGS. 6 to 8 of the drives of the prestressing means according to the invention, with the prestressing means in the stop position; Figure 10 shows the embodiment shown in Figure 9 of a drive of the prestressing means, with the prestressing means in the unfolded state; and Figure 11 an additional alternative mechanism structure to the variants shown in Figures 6 to 10 of the drives of the prestressing means.

An exemplary embodiment of one according to thermoforming installation 1 according to the invention is shown in FIG. 1 in a view from the front. The mobile building modules of the thermoforming system 1 are arranged in a frame 2. The frame 2 can be constructed, for example, in the form of steel plate shell plates, annealed without tension. A crossbar 4 arranged below, that is to the ground, joins the frame plates 2 and at the same time serves as a bed for the bearings of the crankshaft drive 6. The crankshaft drive 6 is driven in the variant represented in this case through an electric servomotor 8. Its driving force is driven by a belt 10 and pulleys 12 and 14, which can be best seen in particular in Figure 2 in the side view. The crankshaft drive 6 is mounted, in the variant shown in this case, symmetrically on both sides in relatively short lever arms 16, the lever arms 16 being articulated on their part to a support 18 fixed on the cross member 4.

In figure 1 as well as in figure 2, the two-part forming tool 20 of the transformation station of the thermoforming installation 1 in a closed state is shown approximately in the middle of the drawing. A crossbar 24 that can be recognized at the top of the drawing of Figure 1 and Figure 2 joins the two frame plates 2 above the two-part forming tool 20 and serves as the basis for a drive 26 to regulate the table 28 of the upper tool with the upper tool 30 fixed therein. The drive 26 for regulating the upper tool table 28 can be configured, for example, as a precision elevator with compensation of the play between threads. A lower tool table 32 carries the lower tool 34 and by means of correspondingly configured linear guides 36 is disposed between the pivoting guide rails 38 of the pivoting guide rails arrangement 40 (see Figures 3 and 4) of the guiding unit 42. Ejecting cylinders 44 and upper connecting rod bearings 46 are fixed on the lower side or on the base of the lower tool table 32.

Between the upper tool 30 and the lower tool 34 of the forming tool 20 shown closed in Figures 1 and 2 a chain transport 48 is shown, by means of which the plastic sheet 50 is fed to the forming tool 20 of two parts and is transported to another place after the forming and stamping of the molded bodies no longer represented in this case, the plastic sheet 50 being tensioned with correspondingly suitable means in the area of the two part forming tool 20 preferably bidirectionally flat.

The upper tool table 28 is guided in linear guides 52 correspondingly configured between the frame plates 2. The lower tool 34 may, for example, have a screw surface of 490 mm x 1040 mm. Thus, for example, four rows with eight cavities each can be achieved for 32 molded bodies with a molded body diameter of approximately 75 mm. This implies a total stamping length of all the edges to be stamped 7640 mm, which makes a total stamping force of approximately 400 kN necessary.

The upper tool 30 is fixed, for example, through spacers not shown in more detail to the upper tool table 28. Guide rails not shown in more detail facilitate the assembly of the tools. A compensation 54 of the play between threads serves to compensate the play for example in the precise lifting drive 26 of the upper tool table 28. The linear guides 36 for the lower tool table 32 have an adjustment without play and guarantee an exact guidance of the lower tool 34. The linear guides 52 of the upper tool table 28 have adjustable slide guides without play not shown in more detail.

The ejection drives 44 arranged below the lower tool table 32 for the ejection elements 56 that can be recognized in Figure 2 in a partial section, have two pneumatic cylinders with a travel limitation.

The connecting rod 58 driven by the crankshaft drive 6, which can also be called a crank for the lifting drive of the lower tool table 32, is configured in the variant represented in this case in the form of a triangle or in the form of a Y. connecting rod 58 is articulated with a first connecting rod section 60 to the eccentric shaft section 62 of the crankshaft drive 6. The two arms 64 directed upwards in Figures 1 and 2 of the Y-shaped connecting rod 58 are articulated to the connecting rod bearings 46 of the lower tool table 32. These two upper connecting rod bearings 46 are arranged in this case if possible so that both a flexion of the lower tool table 32 and its own weight can be kept as small as possible. The connecting rod 58 configured in a Y-shape has only one bearing advantageously in the lower connecting rod section 60 in this case, so that a crank mechanism is sufficient.

As explained above, the crankshaft drive 6 is present with a double support in a flexural resistant embodiment. The main bearings in this regard may be divided for easier assembly. The crankshaft drive 6 is centrally mounted on the lever arms 16, which form a double oscillating handle type. This is in turn mounted with its right side by means of the bearing support 18 on the crossbar 4. On the left side of this double oscillating handle the stamping drive 64 acts. The stamping drive 64 is composed, for example, of a hydraulic cylinder and an associated hydraulic installation, which through the hydraulic cylinder generates an impact-type stamping path, which through the double 16 oscillating handle, the crankshaft drive 6, the connecting rod 58, the bearings 46, is transmitted to the lower tool table 32 and thus to the lower tool 34.

The drive of the crankshaft drive 6, as already mentioned above, can present as a lifting drive a servomotor 8, which through mechanisms, toothed belts, toothed chain drives or the like acts with little play on the crankshaft drive 6 . The closing and opening of the two-part forming tool 20 then corresponds in each case to a rotation of 160 ° in the crankshaft.

The pivot levers 38 already represented in Figures 1 and 2 for the pivotal housing of the lower tool table 32 have, for example, the pivot lever side guides 66 shown in more detail in Figure 3 in this case. , configured as pulleys for direction change. The lateral guides 66, configured for example as pulleys for change of direction, of the pivot lever 38 run on reinforced rails not shown in more detail and can be adjusted without play for the exact guidance of the lower tool 34.

As a drive for pivoting the pivoting guide rails 38 of the arrangement 40 of pivoting guiding rails, a crank 68 is provided on both sides of the lower tool table 32. As a drive 70 for the generation of the pivoting movement of the tool 34 Lower, through the pivoting guide rails 38, a crank pivot drive 68 can be provided, which acts on the two guide rails 38, which, for example, is driven by a reducing servomotor 72 and a synchronous shaft 74. These details are represented in more detail in Figure 4, which shows a section along the line X-X of Figure 3.

To limit the pivotal movement inside the frame or frame 2, a pivot lever stop 76 is provided, as shown in Fig. 3. This stop 76 for the pivot lever 38 can be adjusted for exact positioning of the tool. 32 lower.

The drive 84 for the adjustment of the upper tool table 28, which for example can be configured as a precise drive, serves not only for example for the adjustment of the stamping path, but can also be used to start or stop the path of stamping. Two threaded spindles 78 that can barely be recognized in Figures 1 and 2 are driven, for example, by helical gears 80 through a synchronous shaft 82 by means of a reduction motor 84.

In the variant represented in this case according to Figures 1 to 5, two compensations 54 of the play between threads configured for example as pneumatic bellows cylinders can pull, through traction rods not shown in more detail, from the tool table 28 upper up, to compensate for the lateral play between the spindle and the nut. As shown in more detail in Figure 2, a pre-stretched unit of 86 is provided. The pre-stretching unit 86 has, among other things, in the variant represented in this case, a drive 88 of the prestressing means configured as a servomotor, which is connected through a planetary roller spindle mechanism and a non-toothed belt drive shown in more detail in Figure 2, whose nut is connected through releasable couplings with the prestressing plate 90 and the prestressing means 92 disposed therein. In this case, the drive of the prestressing means can also have a highly dynamic servomotor 88.

In the alternative variant shown in more detail in Figure 1 of the actuation of the prestressing means of the prestressing unit 86, it can have a bracket 94, which as a drive of the prestressing means carries a hydraulic cylinder 96. The hydraulic cylinder 96 travels with the bracket 94 with respect to the upper tool table 28 resting on it linearly. The distance between the hydraulic cylinder 96 with respect to the upper tool table 28 thus remains constant. The hydraulic cylinder 96 is enclosed by a housing 98, so that even in case of slight leaks, hydraulic oil cannot escape. A push rod 100 is articulated to the hydraulic cylinder 96, as shown in Figure 1, and with its opposite end to the hydraulic cylinder 96 is articulated to the right end in the variant represented in this case of a tilting lever 102. The rocker lever 102 is pivotally held by means of a support 104. The support 104 in turn acts through a suitable bearing support on the upper tool table 28. At the left end of the rocker lever 102 is articulated the prestressing rod 106, which is connected with the prestressing plate 90 and the prestressing means 92 disposed therein. The hydraulic cylinder 96 for actuating the prestressing means 92 may have a servo control, which contains a programmable control for the travel of the cylinder 96. The necessary hydraulic equipment can be arranged at the base of the machine. The prestressing rod 106 may be connected through a flexible coupling with the prestressing plate 90 in the upper tool 30. The housing 98 for the hydraulic cylinder 96 not only serves to collect possible leaks, but can also carry the servo control and also contain sensors or the like, to communicate the occurrence of possible leaks and have means to divert them. The same applies to hydraulic lines.

As shown in FIG. 2, a stacking unit 108 can be associated with the thermoforming installation I according to the invention, which receives, stacks and carries the finished molded bodies after their expulsion from the cavities of the lower tool 34. The stacking unit 108 may, for example, have a rake 110 for carrying the ejected molded bodies.

The reference numbers used in the previous explanation of Figures 1 to 5 are used analogously in the following explanation of Figures 6 to 11 for the same elements or parts that act identically or similarly, to simplify the description.

An additional variant of the drives 88 of the prestressing means already explained in Figures 1 to 5 is shown in Fig. 6. A crank mechanism 140 acts through a push-pull rod 100 on a tilting lever 102, which in this case in figure 6 is represented in a simplified way with dots and stripes, to illustrate second different positions, specifically a position when carrying out the work path and thus the descent of the prestressing means 92 and the return path, that is to say raising the prestressing means 92 arranged by the prestressing plate 90. In this case, the rocker lever 102, which tilts with respect to a support point on the support 104, which in the variant represented in this case is transversely displaceable, as indicated by arrow 142, acts on the prestressing rod 106, which is articulated to the pre-stretching plate 90. By moving the bearing support point 104 transversely to an imaginary horizontal line 144, the path 146 can be advantageously varied and, on the contrary, the path 148 of the drive of the prestressing means constant. In this case, the downward-oriented work path, the prestressing means 92 with the additional arrow 150 and the corresponding return path with the arrow 152 are indicated.

In FIG. 7, a possible embodiment of a drive 88 of the prestressing means on the drive side is shown in more detail in a schematic and simplified manner in a sketch. The crank mechanism 140 is supported on the housing side by means of a bearing 154. A mechanism 156 and a clutch-brake combination link the crank mechanism 140 with a motor 160.

An alternative additional embodiment of a drive 88 of the prestressing means is shown in a schematic and simplified sketch in Figure 8. The construction in terms of the mechanism is essentially identical to that explained in Figure 6. Instead of the crank mechanism 140 shown in Figure 6, a hydraulic cylinder 162 is provided in Figure 8, as is also the case with the hydraulic pre-stretching cylinder 96 explained in Figures 1 to 5. The displacement of the support point is indicated again by arrow 142. For the displacement of the support point 104, an electric motor 164 is provided in this sketch according to figure 8 and a spindle 166 for adjustment.

In Figure 9, another variant of a drive 88 of the prestressing means is shown schematically. For the power generation, a cylinder 96 or 162 of hydraulic pre-stretching is used again. This is connected at point A with the push-pull rod 100. The push-pull rod 100 is articulated on its part at point B to the rocker lever 102. The rocker lever 102 is articulated at its point at point C to the prestressing rod 106. The prestressing rod 106 is joined in turn at point D with the prestress plate 90 in an articulated manner. The prestressing means 92 are articulated to the prestressing plate 90, which in turn are mounted in a linearly movable manner in the upper tool 30. The upper tool 30 is fixed on the upper tool table 28. The rocker lever 102 is mounted with rotating movement around the point B0 in the bearing 104.

In the drive 88 of the prestressing means shown in Figure 9, the hydraulic cylinder 96 or 162 is arranged upstream or downstream of the upper tool 30. An alternative arrangement of the cylinder 96 or 162 is also possible next to the tool 30. The prestressing means 92 are shown in Figure 9 in the stop position. Accordingly, the prestressing means 92 are shown in the schematic sketch according to Figure 10 in the deployed position. Moreover, the representation according to figure 10 is equal to the variant shown in figure 9 of an exemplary embodiment of a drive 88 of the prestressing means.

A further alternative embodiment of a drive 88 of the prestressed means is shown in Figure 11. This resembles the variant shown in Figures 9 and 10, although it shows an alternative lever mechanism. In this case, the elongated holes B and C are provided with elongated holes, which allow an axial displacement of these articulation points, so that the hydraulic cylinder 96 or 162 can be articulated directly to the tilting lever 102 at point B, of so that the push-pull rod 100 can be dispensed with. In the same way, the prestressing rod 106 can be dispensed with, matching the previous articulation points C and D at a common articulation point C, in which the rocker lever 102 is directly connected with a correspondingly designed shoulder or support 168 with pre-stretched plate 90.

As explained above, in order to form the molded bodies, for example in the form of a vessel, the heated plastic sheet 50 is introduced, with the aid of the prestressing means 92, mounted in a straight line in the upper tool 30, in the shaping holes or cavities of the lower tool 34. By generating, for example, an overpressure in the upper tool 30, the sheet rests on the walls of the shaping holes or cavities. The prestressing means 92 again in this case return to their stop position (see Figure 9) in the upper tool 30 (see arrows 150 or 152 in Figures 6 and 8).

In order to achieve the shortest possible time for shaping the molded bodies, a drive 88 of the prestressing means with a high dynamic is proposed. For a cycle of movement of the prestressing means 92 (downward movement 150 and movement 153 returning to the initial position) a duration of a maximum of 300 ms, preferably a maximum of 250 ms, and especially a maximum of 200 ms, is particularly preferred. . Furthermore, actuation 88 of the prestressing means explained in Figures 6 to 11 can generate the necessary forces to prestress the plastic sheet 50. The sum of the forces acting on the individual prestressing means 92 can amount to 50,000 N. according to the embodiment.

Accordingly, the previously explained embodiment of a drive 88 of the prestressing means is provided with a hydraulic cylinder 96 or 162 for the generation of the necessary forces. The prestressing means 92 are firmly connected, in the representations according to Figures 9 to 11, by means of a prestressing rod 170, with a bridge or the so-called prestressing plate 90. The printing rods 190 run in a straight line guided in bushings 172 of the upper tool guide 30, so that the entire pre-stretching unit 86 can move vertically.

The actuation of the prestressing means 92 occurs as explained above with the aid of the hydraulic cylinder 96 or 162, as shown in Figures 1 to 5, in firm connection with a bracket 94, in turn carried by the table 28 top tool. The linear movement of the piston rod 174 is transmitted through the push-pull rod 100 or coupling with the swivel joints A and B first to the rocker lever 102. The rocker lever 102, as explained above, is pivotally supported at point B0 with respect to the upper tool table 28. The prestressing rod 106 or coupling with the swivel joints C and D finally transmits the movement of the rocker lever 102 to the prestressing unit 86.

The mechanism schematically represented in Figures 6 to 11 can be varied in many ways. In an exemplary variant, the movement of the rocker lever 102 can be transmitted through a bolt and a slide to the prestressing unit 86. Similarly, the cylinder 96 or 162, alternatively to the firm connection with the bracket 94, can be articulated only with respect to the bracket 94 and thus be pivotally secured.

An additional advantage of the drive 88 of the hydraulic prestressing means is the high forces that can be generated therewith with very good dynamics. In this case there is no risk of thermal overload.

The present invention thus provides for the first time in an advantageous manner a thermoforming installation for the production of molded bodies from a plastic sheet, such as glasses, containers, lids, food containers or the like, with a transformation station having a two part forming tool. The two-part forming tool has an upper tool table that can be set in an adjustable way, with an upper tool with prestressing means movably mounted thereon, and a mobile lower tool table with a lower tool with cavities. The mobile lower tool table is guided by means of a guiding unit and can be moved by means of a drive unit with respect to the upper tool table to and from it. In this case, the upper tool table according to the invention presents for the first time a first drive unit associated therewith to place the upper tool table in position with respect to the upper dead center of the lower tool table in correspondence with the molded body to be produced in each case. The upper tool table also presents for the first time a second drive unit associated therewith to drive the prestressing means movably mounted on the upper tool. The present invention also proposes for the first time an economical process for the production of molded bodies from a plastic sheet.

Whenever a hydraulic drive is provided for the prestressing means, it can be advantageously provided as a so-called servo control with linear amplification so that both its travel and its velocity profile are independently controlled from one another and thus can be predetermined.

With the thermoforming system according to the invention, plastic sheets of PP, PS, PE, PET, ABS or PVC can be processed. The plastic sheet fed to the thermoforming plant as a sheet strip can in this case have a sheet bandwidth of at least 250 mm to 750 mm with a sheet band thickness of at least 0.3 mm to 4 mm . The available shaping surface between the upper and lower tools amounts to at least 700 mm x 450 mm. The maximum closing force amounts to at least 400 kN with a maximum cutting length of at least 8400 mm.

List of reference numbers

1 thermoforming installation 2 frame or frame 4 lower cross member 6 crankshaft drive 8 electric servomotor 10 belt 12 pulley 14 pulley 16 lever arm 18 bearing support 20 two part forming tool 22 24 upper cross member 26 upper tool drive adjustment 28 upper tool table 30 upper tool 32 lower tool table 34 lower tool 36 linear guide of lower tool table 38 pivoting guide rails 40 arrangement of guide rails 42 guide unit 44 eject drive 46 connecting rod bearings 48 conveying bearings chain 50 plastic sheet 52 linear guide of upper tool table 54 compensation of the play between threads 56 ejection element 58 connecting rod 60 first connecting rod section 62 eccentric shaft section 64 stamping drive 66 pivot lever side guide

68 crank pivot drive 70 pivot drive 72 reducer servo motor 74 synchronous shaft 76 pivot lever stop 78 threaded spindle 80 helical gear 82 synchronous shaft 84 reduction motor 86 pre-stretching unit 88 prestressing means drive 90 prestressing plate 92 medium prestressing 94 bracket for actuating the prestressing means 96 hydraulic prestressing cylinder 98 housing 100 push rod 102 tilting lever 104 tilting lever support 106 prestressing rod 108 stacking unit 110 rake

140 crank mechanism 142 support point displacement 144 imaginary horizontal line 146 variable travel 148 constant travel

150 work tour 152 return 154 bearing 156 mechanism

5 158 clutch-brake combination 160 engine 162 hydraulic cylinder 164 electric motor 166 spindle adjustment

10 168 shoulder or bearing 170 prestressing rod 172 slide guide 174 piston rod

fifteen

Claims (7)

1. Installation (1) of thermoforming for the production of molded bodies from a sheet

(fifty)

 of plastic, such as glasses, containers, lids, food containers or the like, with a transformation station presenting a two-part forming tool (20),

in which the two-part forming tool (20) has an upper tool table (28) that can be set in an adjustable manner with an upper tool (30) with prestressing means (92) movably mounted thereon and a mobile bottom tool table (32) with a tool

(3. 4)

 bottom with cavities,

the mobile lower tool table (32) being guided by means of a guiding unit (42) and being able to move by means of a drive unit with respect to the upper tool table (28) to and from it, wherein the upper tool table (28) has a first drive unit (26) associated therewith to place the upper tool table (28) in position with respect to the upper dead center of the table (32) of lower tool in correspondence with the molded body to be produced in each case, and wherein the upper tool table (28) has a second drive unit (88) associated therewith to drive the prestressing means (92) movably mounted on the upper tool, characterized in that the second drive unit (88) acts through a push-pull rod (100), a tilting lever (102) and a pressure rod (106) on the prestressing means (92) in the tool ( 30) upper, preferably by means of a support point B0 of the swivel lever (104) movably designed (142). 2. Thermoforming installation (1) according to claim 1, characterized in that the first unit (26) drive to place the upper tool table is an electric servomotor (84).

3.

Installation (1) of thermoforming according to claim 1 or 2, characterized in that the first drive unit (26) driven by a synchronization shaft (82) with endless screws / wheels disposed thereon acts together with two spindles (78 ) of adjustment, which in turn act on the upper tool table (28) such that it can move in its horizontal orientation vertically up and down, so that the upper tool table (28) can be adjusted to the body molded that will occur in each case.

Four.

Installation (1) of thermoforming according to one of claims 1 to 3, characterized in that the second drive unit (88) of the upper tool table (28) for actuating the prestressing means (92) has a drive (96, 162 ) hydraulic or a crank drive (140) driven by means of an electric servomotor (160).

5.

Thermoforming installation (1) according to one of claims 1 to 4, characterized in that the prestressing means (92) by means of the second drive unit (88) can be operated in such a way that a path (146) can be made to the minus 120 mm in less than 300 ms, preferably less than 200 ms.

6.

Procedure for the production of molded bodies from a plastic sheet, such as glasses, containers, lids, food containers or the like, by means of a thermoforming installation (1), with the following steps:

- providing a thermoforming installation (1) according to the preamble of claim 1; -feeding a plastic sheet (50) in the two part forming tool (20) by means of a chain transport (48); - Stretch the plastic sheet (50) in the area of the forming tool (20); -close the forming tool (20) guiding the mobile lower tool table (32) by means of the guiding unit (42) and operating it by means of the drive unit in such a way that it moves with respect to the upper tool table (28) towards it, -produce the molded bodies with the closed forming tool (20), -open the forming tool (20) guiding the mobile lower tool table (32) by means of the guiding unit (42) and actuating it by means of the drive unit such that it moves relative to the upper tool table (28) therefrom, 5 - push the molded bodies optionally towards a stacking unit, - placing the upper tool table (28) by means of a first drive unit (26) associated therewith in its position with respect to the upper dead center of the table (32) of lower tool in correspondence with the molded body to be produced in each case, and 10 -acting the prestressing means (92) movably mounted on the tool (30) upper by means of a second drive unit (88), characterized because -the second drive unit (88) acts through a push-pull rod (100), a tilting lever (102) and a pressure rod (106) on the means (92) of 15 prestressed in the upper tool (30), preferably by means of a support point B0 of the swivel lever (104) movably designed (142). Method according to claim 6, characterized in that the prestressing means (92) is operated by means of the second drive unit (88) such that a path (146) of at least 120 mm is made in less than 300 ms, preferably less than 200 ms. twenty