WO2014083467A1

WO2014083467A1 - A thermoforming machine with a moving tilting bed

Info

Publication number: WO2014083467A1
Application number: PCT/IB2013/060109
Authority: WO
Inventors: Dario GOTTI
Original assignee: Wm Wrapping Machinery Sa
Priority date: 2012-11-28
Filing date: 2013-11-13
Publication date: 2014-06-05
Also published as: ITMI20122022A1

Abstract

A thermoforming machine with a moving tilting bed (4), comprising a forming station consisting of a lower mold nest (3) and a fixed upper mold nest; the lower mold nest is supported by a moving bed which has a closure position, in which the molding of the workpieces is performed, and an ejection position for the molded pieces; the bed is movable linearly and is rotatable about its axis. The moving tilting bed is directly controlled by a movement mechanism (8) which causes it to perform the vertical movement, by means of a simple crank/connecting-rod system (9, 10). The rotary/translatory movement of the tilting bed is controlled by two gearmotors (11, 12), with an absolute encoder, which are managed by a PLC program. In the case of anomalous operation of the electronics, namely should there be any displacement between the programmed vertical position and the associated rotation, a mechanical safety device consisting of a cam and cam follower intervenes.

Description

Title: "A THERMOFORMING MACHINE WITH A MOVING TILTING BED"

DESCRIPTION

The present invention relates to a thermoforming machine with a moving tilting bed.

In particular, the present invention relates to a press, in particular for the production of plastic articles, in which the parts are thermoformed between two mold nests: an upper mold nest, fastened to the fixed bed, and a lower mold nest, fastened to the moving bed.

The moving bed has at least two operating positions: a position for molding the parts and a position for ejecting said parts .

The machines of this type have the problem of moving the moving bed with a sufficient rapidity and precision from the molding position into the ejection position and vice versa.

In the ejection position, in fact, the moving bed is inclined and lowered with respect to the molding position.

The movement of the moving bed is performed by a mechanism consisting of a system of cam-operated levers.

The patent US-4565513 describes a machine provided with a mechanism of this type.

EP-1982822 describes a device for moving the moving bed of a press which is substantially improved compared to the previously known systems. The moving bed is actuated by a cam system which effects the vertical movement and corresponding tilting thereof, performing a rotary/translational movement which is subject to ,a well-defined movement pattern.

According to a further evolution of the movement system, the vertical translational movement, namely upward and downward movement, of the moving bed has been rendered independent of the rotary movement of the said moving bed, therefore making the combination of the two movements more flexible. A cam assembly with the associated levers moves a first moving bed which is guided along the shoulders of the press, by means of prismatic guides or columns. The moving tilting bed is hinged on the first moving bed which has, fixed thereon, a gearmotor which controls the rotation of the latter.

The task of the present invention is to provide a thermoforming machine, with a moving tilting bed, which is substantially improved compared to- the thermoforming ^{' ""}ma^'dhiries^'-of the cited prior art.

In connection with this task, an object of the invention is to provide a thermoforming machine with a moving tilting bed having a system for moving the mold-carrying moving bed which is substantially simplified compared to the systems of the known type and is made with a substantially smaller number of parts.

A further purpose of the invention is to provide a machine which requires a reduced amount of maintenance compared to the machines of the known type.

Yet another purpose is to provide a machine which allows a greater freedom in the positioning of the mold-carrying moving tilting bed, together with a greater versatility during the production process.

Another ' purpose ' bf the " present ^*" invention"^~ is - to provide^' a machine which, owing to its particular constructional features, is able to ensure the maximum degree of reliability and safety during use.

These and other objects, which will emerge more clearly below, are achieved by a thermoforming machine with a moving tilting bed, comprising a forming station consisting of a lower mold nest and a fixed upper mold nest; said lower mold nest being supported by a moving bed; said moving bed having at least one closure position, in which the molding of the workpieces is performed, and at least one ejection position for the molded pieces; said moving bed being movable .linearly and rotating about its axis; said machine being characterized in that it comprises a movement mechanism which acts directly on said moving bed and linearly moves said moving bed between said closure position and said ejection position.

Further characteristic features and advantages will emerge more clearly from the description of preferred, but non-exclusive, embodiments of the invention illustrated by way of a non-limiting example in the accompanying drawings in which: - ·< . ^■■^■

Figure 1 is a partially sectioned front elevation view of the thermoforming machine with moving tilting bed according to the present invention, shown in the position where the mold is closed;

Figure 2 is a side elevation view, sectioned along the cross- sectional plane II-II of Figure 1, showing the apparatus in the position where the mold is closed;

Figures 3-7 are views similar to that of Figure 2, showing in sequence the movement of the tilting bed from the closed position to the ejection position.

With reference to the said figures, the thermoforming machine with a mold-carrying moving tilting bed according to the invention, denoted overall by the reference number 1, comprises a forming station 2 consisting of a lower mold nest 3, supported by a moving - bed 4 ,·- and - a · fixed upper- mold "nest .-_.§·;.- -attached to the columns 6 of the press 1.

The moving bed 4 has a closure position, visible in Figures 1 and 2, in which molding of the workpieces is performed, and a position for ejection of the molded pieces, visible in Figure 7.

Figures 2-7 s,how in sequence the movement of the moving bed 4 from the initial position where the mold is closed to the final ejection position.

The moving bed 4 moves in a vertical direction and is able to rotate about a horizontal axis of rotation 7.

The movement of the moving bed 4 in the vertical direction is performed by a movement mechanism 8 consisting of a pair of rods 9 connected to respective cranks 10 which are driven by a first gearmotor 11.

Advantageously, the two driving rods 9 exert the force for closing the press directly on the mold-carrying tilting moving bed 4 and not on the intermediate moving bed, as instead occurs in conventional presses.

The rotational movement of the moving bed 4 about the horizontal axis 7 is controlled by a second gearmotor 12.

The rotary/translatory movement of the moving bed 4 is therefore controlled by the two gearmotors 11 and 12, with an absolute encoder, which are managed by a PLC program.

In the case of anomalous operation of the electronics, namely should there be any displacement between the pre-programmed vertical position of the mold-carrying moving bed 4 and the associated rotation, impacts or breakages or the like might arise.

In order to overcome this drawback a mechanical safety device, denoted overall by the reference number 13, is provided, said device consisting of a cam-follower member 16 and a cam 15.

The cam-follower member 16 consists of a plate which is integral with the moving bed 4 and supports a first roller 14 and a second roller 18.

The cam 15 comprises an arcuate profile which is interrupted by a vertical guide 20.

During normal operation of the machine 1, the first roller 14 is distanced from the profile of the cam 15 and never touches it. By way of example, the distance of the first roller 14 from the surface of the profile of the cam 15 is about one millimeter.

The second roller 18 engages with the vertical guide 20, in the mold closed position, exclusively in order to center the lower mold nest 3 on the upper mold nest 5 during the molding stage, thus eliminating the play which is created in the mechanism and in the gearmotor which performs rotation of the lower moving bed 4.

During normal operation of the machine, the mechanical safety device does not intervene; however, should there be a problem due to displacement, the PLC detects the different position of the moving bed in relation to the correct position and sets the machine to the alarm condition, stopping it completely.

In this situation the first roller 14 comes into contact with the surface of the cam 15, preventing impacts between the moving parts of the bed/mold and the fixed parts.

The small distance between the first roller 14 and the surface of the cam 15 results in an extremely, small travel movement of the first roller 14 and therefore a very gentle impact between the moving parts .

It has essentially been shown how the invention achieves the predefined task and objects by providing a thermoforming machine with a mechanism for moving the tilting moving bed which is greatly simplified from a structural point of view, helping significantly to achieve a reduction in the number of parts and the time needed for assembly of the machine.

Moreover, the machine is lighter and requires a smaller amount of maintenance compared to the conventional machines.

Unlike the systems where the vertical movement of the mold carrier is controlled by means of a cam assembly, the present invention allows a greater degree of freedom with regards to positioning of the mold-carrying moving tilting bed and a greater versatility during the production process.

The mechanical safety process ensures that any electronic malfunction cannot cause any structural damage.

The machine according to the invention may be subject to numerous modifications and variations, all falling within the scope of the inventive idea; moreover, all the details may be replaced by other technically equivalent elements.

Obviously the materials used, as well as the dimensions, may be of any nature depending on the requirements and the state of the art.

Claims

1. A thermoforming machine with a moving tilting bed, comprising a forming station consisting of a lower mold nest and a fixed upper mold nest; said lower mold nest being supported by a moving bed; said moving bed having at least a closure position, in which the molding of the workpieces is performed, and at least an ejection position for the molded pieces; said moving bed being movable linearly and rotatable about its own axis; said machine being characterized in that it comprises a movement mechanism which acts directly on said moving bed and linearly moves said moving bed between said closure position and said ejection position.

2. Machine according to claim 1, characterized in that said movement mechanism comprises a pair of rods connected to respective cranks which are driven by a first gearmotor.

3. Machine according to claim 2, characterized in that said rods are connected to said moving bed without any intermediate elements and exert a closing force directly on said moving bed.

4. Machine according to one or more of the preceding claims, characterized in that it comprises a second gearmotor adapted to rotate said moving bed about said axis.

5. Machine according to one or more of the preceding claims, characterized in that it comprises an electronic control unit adapted to control said first and second gearmotors and said bed movable linearly and rotating about said axis.

6. Machine according to one or more of the preceding claims, characterized in that it comprises a mechanical safety device adapted to intervene in case ^'1' of malfunction, such as a displacement between the linear position of the moving bed and the rotation of said moving bed.

7. Machine according to claim 6, characterized in that said mechanical safety device comprises a cam-follower member associated with said moving bed, and a cam integral with a fixed part of said machine.

8. Machine according to claim 7, characterized in that said cam-follower member is integral with said moving . bed and comprises a first roller and a second roller.

9. Machine according to claim 7, characterized in that, during normal operation of said machine, said first roller is distanced from said cam and never touches it; said second roller engaging with a guide formed in said cam, at least in the mold closing position, .in order to center said lower mold nest on said upper mold nest.

10. Machine according to claim 9, characterized in that said first roller is at a minimum distance from said cam and, during normal operation of said machine, said mechanical safety device does not intervene; in the case of a malfunction, when said moving bed is not located in a programmed position, said electronic control unit stops operation of the machine and said first roller comes into contact with said cam, thus preventing damage to the moving parts and the fixed parts of said machine; said distance of said first roller from said cam being small enough to limit the impact effects between the moving parts.