Semi-finished product transport device for moving thermoplastic plastic sheets in a thermoforming machine and method for forming thermoplastic plastic sheets into molded parts

Abstract

Semi-finished product transport device for moving thermoplastic sheets in a thermoforming machine for forming parts, comprising at least one forming station with a heating device and a transport device (2), characterized in that the semi-finished product transport device has two mechanically independent, opposing connections (5), each of which is connected by second struts (8) to one of the two sides of the transport device (2), wherein the connections (5) hold grippers (3) by means of carriages (6, 10) and fixed points (9), which grip a plastic sheet (1) on two opposite longitudinal sides, wherein the connections (5) are designed such that second carriages (10) move away from the fixed point (9) faster than first carriages (6) in the same time units, and wherein the carriages (6, 10) are power-driven and movable by means of drives (4, 11, 12), wherein the connections (5) are designed as threaded rods.which have threads with different pitches in different sections.

Description

[0001] The invention relates to a semi-finished product transport device for moving thermoplastic plastic sheets in a thermoforming machine and a method for forming thermoplastic plastic sheets. State of the art

[0002] Prior art includes semi-finished product transport systems that receive blanks in the form of thermoplastic sheets and transport them to a combined heating and forming station. The blanks are fed directly from the stack into the heating and forming station. After the molded part has cooled, the semi-finished product transport system picks it up and transports it to a delivery point. Heating and forming are performed sequentially, with heating being fully completed before the forming process begins. This results in a total cycle time in which the heating and forming processes each contribute a separate amount to the overall cycle time.

[0003] Document DE 10 2016 012 425 A1 discloses a device and a method for stretching and / or forming and / or laminating a film element, as well as a laminating station and system for laminating a component. To further develop conventional devices for stretching and / or forming and / or laminating a film element, the invention proposes a device for stretching and / or forming and / or laminating a film element with a support frame for clamping the film element relative to a forming tool or a component to be laminated, and with grippers for gripping the film element, which are movably mounted relative to the support frame. The device is characterized in that the grippers are arranged to be multiaxially adjustable relative to the support frame in order to adapt the film element more precisely to a contour of the forming tool or the component to be laminated.

[0004] Document US 5,207,963 discloses a method for forming a carpet blank with a plastic backing into a desired shape for the production of carpets for motor vehicle interiors, where the required carpet linings are typically not flat but have a curved contour because they must follow the contours of the passenger compartment. The method uses a portable frame assembly with an open rack and flexible retaining clips. The retaining clips suspend a carpet blank with a plastic backing within the rack. The frame assembly has a set of wheels, allowing it to be easily transported between workstations such as a heating zone and a forming zone. The flexible retaining clips maintain constant tension on the carpet during the forming zone to produce a high-quality formed carpet.

[0005] Document US 10,000,005 B2 discloses a vacuum forming process and a vacuum forming device for an object with a cover bonded to the surface of a substrate. The vacuum forming device includes a cover clamping device for receiving the cover. The cover clamping device comprises a rectangular outer frame that is tiltably mounted relative to a pair of support elements extending in the transverse direction. The outer frame is configured by a pair of frame elements extending in the longitudinal direction and a pair of frame elements extending in the transverse direction. Longitudinally extending guide rods are arranged and attached to the frame members. Each of the guide rods extends through the corresponding ends of the frame members. The guide rods allow the frame members to move parallel to each other in a plane.Each of the frame parts corresponds to a support device. Threaded rods extending in the longitudinal direction are supported by and attached to the frame part. Task

[0006] The invention is based on the objective of proposing both an improved semi-finished product transport device and a possibility in which the total time for a work cycle for the deformation of plastic sheets is reduced.

[0007] According to the invention, this problem is solved by the measures specified in the characterizing portion of claim 1 and in dependent claim 7. Further preferred embodiments of the invention result from the remaining features mentioned in dependent claims 2 to 6. Example of implementation

[0008] A semi-finished product transport system is proposed that receives thermoplastic sheets and transports them to a preheating station, and then to a forming station. By using a preheating station, the plastic sheet requires less time for further heating in the forming station and can be quickly formed and cooled there.

[0009] To ensure uniform heating in the preheating station, the semi-finished product transport device is designed to apply tensile forces to the heated plastic sheet in two orthogonal directions, so that the plastic sheet is not clamped in a rigid frame. This prevents deformation that could cause waves to form in the plastic sheet or that the sheet would buckle under the influence of gravity and thus be heated unevenly.

[0010] Furthermore, the plastic sheet, in its clamped state, is transferred to a clamping frame in the forming station and can be formed there while clamped. Further details of the invention are described below with reference to the schematic drawings. These show: Fig. 1 The inventive semi-finished product transport device in a first embodiment, in which the semi-finished product transport device is designed in two parts. Each part is attached to a double transport device 2 by means of second struts 8, the transport device 2 being known from the prior art for transporting plastic sheets 1 or plastic film. The semi-finished product transport device has a connection 5 which is attached to the transport device 2 by means of second struts 8 and which also carries grippers 3 by means of first struts 7. Carriages 6, 10 are slidably arranged on the connections 5. Furthermore, the semi-finished product transport device has second and third drives 11, 12 with, for example, motors and threaded rods, which rotate relative to the carriages 6, 10 by means of torque supports (not shown) and thereby move the carriages 6, 10 axially. A fixed point 9 is rigidly arranged on the connection 5.The drives 11, 12 can have different gradients or be moved at different speeds to ensure that the plastic plate 1 is stretched. The reference symbols from Fig. 1 will be in the Fig. 2 and Fig. 3 not necessarily repeated if the figures have identical components.

[0011] Fig. Figure 2 shows another advantageous embodiment of the semi-finished product transport device, which is also designed in two parts. Second and third drives 11, 12 space the carriages 6 and carriages 10 apart, respectively. This movement can, for example, be force-controlled. e.g. by means of pneumatic cylinders which are subjected to an advantageous pressure stage.

[0012] Fig.3 Alternatively, in a more compact design, the connections 5 have threads and first drives 4. On areas facing the ends of the connections 5, the threads have larger pitches than in the middle areas of the connections 5. This allows the carriages 10 to move axially faster than the carriages 6, ensuring that the expanding plastic sheet 1 is always kept taut. The two transport devices 2 are also spaced apart to ensure that the expanding plastic sheet 1 is kept taut in this dimension as well.

[0013] It is inventively provided that the semi-finished product transport device for moving thermoplastic plastic sheets in a thermoforming machine for forming into molded parts, comprising at least one forming station with a heating device and a transport device 2, is designed such that the semi-finished product transport device has two mechanically independent opposing connections 5, each of which is connected by second struts 8 to one of the two sides of the transport device 2, wherein the connections 5 hold grippers 3 by means of carriages 6, 10 and fixed points 9, which pick up a plastic sheet 1 on two opposite longitudinal sides, wherein the carriages 6, 10 are power-driven and movable by means of drives 4, 11, 12.The connections 5 are to be designed such that second carriages 10 move away from the fixed point 9 faster in the same time units than first carriages 6, wherein the connections 5 are designed as threaded rods which have threads with different pitches in different sections.

[0014] The grippers 3 are advantageously connected to carriages 6, 9, 10 via first struts 7. The connections 5 are to be connected to the transport device 2 via second struts 8. The transport device 2 is advantageously designed as at least two parallel units, the units having synchronized drives for moving the semi-finished product transport device. Alternatively, it is equally advantageous if drives 11, 12 cooperate with the connections 5, and the drives 11, 12 have threads with different pitches. Furthermore, it is advantageous if the drives 11, 12 are driven at different speeds. The first and second carriages 6, 10 are advantageously axially movable, and the at least one fixed point 9 is arranged in a fixed position on the connection 5.

[0015] The inventive method for forming thermoplastic sheets into molded parts, in which thermoplastic sheets are transported for heating, the preheated thermoplastic sheets are fully heated in the molding station and formed into molded parts, and the molded parts are then ejected from the molding station, is designed such that a semi-finished product transport device picks up the thermoplastic sheets by means of grippers 3 arranged at the two connections 5 of the semi-finished product transport device and, during and after heating, the grippers 3 are spaced apart from each other by means of the spacing of carriages 6, 9, 10 also arranged on the semi-finished product transport device and by the spacing of parts of the transport device 2 from each other, wherein the first carriages 6 and the second carriages 10 are each spaced apart from each other by means of a drive 4, 11, 12. Reference symbol list 1 plastic sheet 2 Transport equipment 3 grippers 4 First drive 5 connection 6 First car 7 First abutment 8 Second strut 9 Fixed point 10 Second car 11 Second drive 12 Third drive

Claims

Semi-finished product transport device for moving thermoplastic sheets in a thermoforming machine for forming parts, comprising at least one forming station with a heating device and a transport device (2), characterized in that the semi-finished product transport device has two mechanically independent, opposing connections (5), each of which is connected by second struts (8) to one of the two sides of the transport device (2), wherein the connections (5) hold grippers (3) by means of carriages (6, 10) and fixed points (9), which grip a plastic sheet (1) on two opposite longitudinal sides, wherein the connections (5) are designed such that second carriages (10) move away from the fixed point (9) faster than first carriages (6) in the same time units, and wherein the carriages (6, 10) are power-driven and movable by means of drives (4, 11, 12), wherein the connections (5) are designed as threaded rods.which have threads with different pitches in different sections. Semi-finished product transport device according to claim 1, characterized in that the grippers (3) are connected to carriages (6, 9, 10) via first struts (7). Semi-finished product transport device according to claim 1, characterized in that the transport device (2) has synchronized drives for moving the connections (5) of the semi-finished product transport device. Semi-finished product transport device according to claim 1, characterized in that drives (11, 12) cooperate with the connections (5), and that the drives (11, 12) have threads with different pitches. Semi-finished product transport device according to claim 1, characterized in that the drives (11, 12) are driven at different speeds. Semi-finished product transport device according to claim 1, characterized in that the first and second carriages (6, 10) are axially movable and the at least one fixed point (9) is arranged in a fixed position on the connection (5). Method for forming thermoplastic sheets into molded parts, carried out by means of a device according to claim 1, in which thermoplastic sheets are transported for heating, the preheated thermoplastic sheets are fully heated in the molding station and formed into molded parts, and the molded parts are then ejected from the molding station, characterized in that a semi-finished product transport device receives the thermoplastic sheets by means of grippers (3) arranged on the two connections (5) of the semi-finished product transport device and, during and after heating, the grippers (3) are spaced apart from each other by means of the spacing of carriages (6, 9, 10) also arranged on the semi-finished product transport device and by the spacing of the two connections (5) from each other, wherein the first carriages (6) and the second carriages (10) are each spaced apart from each other by means of a drive (4, 11, 12).

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