EP3109017B1 - Deep draw packaging machine with film stamp - Google Patents

Description

The invention relates to a thermoforming packaging machine according to the preamble of claim 1 and to a method having the features of claim 6.

From the DE 198 41 415 A1 is known a foil punch, which is suitable to cut plastic films by means of a knife and a counter knife. In this case, a linear actuator is provided with a linear actuator; and by means of an articulated lever arrangement in conjunction with a stretch lever arrangement, which together comprise a plurality of mechanical levers, it is achieved that effective forces can rapidly increase for cutting the film and the flattening of the forces at the end of the punching stroke. The advantage here is that the film punch is to be suitable to be able to cut different thicknesses of films reliably, without the need for complicated adjustment of the knife are necessary.

From the prior art is a foil punch type FS 08 from the house of the applicant (see Fig. 1 ), which has a pneumatic cylinder as a hoist drive and cuts through a film web by means of crushing knife and counter-pressure bar. In order to keep the load or the wear of the crushing knives as low as possible when in contact with the counter-pressure strip, but at the same time be able to cut through thick films, the counter-pressure bar is designed with a fine adjustment to the back pressure bar to the final position with an accuracy of at least 0.02 mm of the crusher blade.

As the running time increases, the cutting edge of the crimping knife becomes duller and the counterpressure strip or the crimping knife should be readjusted in order to ensure reliable and qualitatively good cutting of the film. When using such a foil punch on thermoforming packaging machine, the crushing knife and possibly also the counter-pressure bar are often replaced in format changes and then the counter-pressure bar or the crusher must be readjusted. This is carried out in a first test phase while the thermoforming packaging machine is running and requires a certain amount of effort until the cut or the severing of the film is precisely set.

The loading of the crimping knife by the contact with the counter-pressure bar during each cutting or squeezing operation can be very high, as in a time-force diagram according to FIG Fig. 2 shown. In order to be able to produce this diagram in such a way, pressure measuring sensors in the area of the fine adjustment device were provided in an experimental arrangement in order to detect the load on the counter pressure bar or the crush meter. The diagram shows that after the cutting of the film at time t _2, the force continues to rise, as the pneumatic cylinder with its executable by the applied pressure force presses the crimping knife and the counter-pressure bar against each other. This force F1 is in this case shown by way of example more than twice as high as necessary for the separation process. However, a fundamental reduction in the compressed air supply of the pneumatic cylinder is not desirable, as with a halving of the pressure, for example, is accompanied by a reduction in the speed of the lifting drive and this reduces the cycle performance of the film punch. At the same time, the reduced speed at which the crimping knife strikes the film has a negative impact on the quality of cut when the film is cut.

Object of the present invention is to improve a thermoforming packaging machine with a foil punch in terms of extending the life of the tools and to facilitate the adjustment of the tools to each other when changing the tools.

This object is achieved by a thermoforming packaging machine with the features of claim 1 or by a method for operating such a thermoforming packaging machine with the features of claim 6. Advantageous developments of the invention are specified in the dependent claims.

The thermoforming packaging machine according to the invention comprises a control and a foil punch, which has a lever mechanism, an upper tool part and a lower tool part, wherein at least the upper tool part or the lower tool part are movable by means of the lever mechanism so as to approximate the upper tool part and the lower tool part. The thermoforming packaging machine according to the invention is characterized in that the film die has a servo drive and a measuring unit is provided which is configured to detect the contact between the tool top and the tool bottom. Taking into account this contact position of the movable tool, for example by a calibration process, the for the punching process most suitable end position or end position of the movable tool and thus the position of both tools to each other determined in the controller and approached or positioned in the subsequent punching operations. Due to the exact end position of the movable tool, there is no unnecessarily higher force or load on the crusher.

Preferably, the controller is connected to the measuring unit and the position of the upper tool part and the lower tool part in the working position can be calculated by means of the controller. This supports a fully automated calibration mode. In addition, it is optionally also provided to perform the lower position or the open tool position changeable by the operator and to be able to store in programs to reduce unnecessary lifting movements, for example, at low packing depths.

In an advantageous embodiment, the measuring unit is a controller of the servo drive, so that based on a current consumption over time, namely during the calibration movement of the movable tool, the working position can be detected and evaluated. Because at the point where the tools come into contact, the power consumption increases sharply and it can have more characteristic features.

Alternatively, the measuring unit is a pressure measuring sensor or a structure-borne sound or vibration measuring sensor in order to detect the pressure force between the upper tool part and the lower tool part. The structure-borne sound or vibration measurement sensor are preferably suitable for detecting the meeting of the two tools by the sudden impact and for detecting the vibration generated thereby.

Preferably, the servo drive comprises a servomotor with regulator and a spindle, preferably a ball screw, in order to position the movable tool at high speed with high accuracy at the same time.

A method according to the invention for determining the working position, in particular of the lower die part of the foil punch, is characterized in that the lower tool part and the upper die part are approximated and the contact of the tools is determined by means of an evaluation of data of the measuring unit by means of the control.

Preferably, the measuring unit is a controller for a servomotor of the servo drive and based on the current consumption of the servo motor, the force profile of the force acting on the movable tool is detected. Thus, based on the current profile over time with simultaneous detection of the position of the tools to one another, a suitable position, namely an end position, can be determined automatically in the controller.

Alternatively, the measuring unit is a pressure measuring sensor and there is a force measurement on a tool.

Preferably, the controller calculates an end position for the movable tool, so that during punching no (substantially) higher than the forces necessary for the punching process are generated to extend the life of the tools.

Fig. 1

eine Schnittansicht einer Folienstanze gemäß dem Stand der Technik,

Fig. 2

ein Zeit-Kraft-Diagramm der herkömmlichen und einer erfindungsgemäßen Folienstanze,

Fig. 3

eine schematische Seitenansicht einer erfindungsgemäßen Tiefziehverpackungsmaschine,

Fig. 4

eine Schnittansicht einer erfindungsgemäßen Folienstanze in Produktionsrichtung in einer Grundstellung,

Fig. 5

eine Schnittansicht der Folienstanze in einer teilgeschlossenen Stellung und

Fig. 6

eine Schnittansicht der Folienstanze in einer Endstellung,

In the following, an advantageous embodiment of the thermoforming packaging machine according to the invention and the method according to the invention is explained in more detail with reference to a drawing. In detail show:

Fig. 1

a sectional view of a foil punch according to the prior art,

Fig. 2

a time-force diagram of the conventional and a foil punch according to the invention,

Fig. 3

a schematic side view of a thermoforming packaging machine according to the invention,

Fig. 4

a sectional view of a foil punch according to the invention in the production direction in a basic position,

Fig. 5

a sectional view of the foil punch in a partially closed position and

Fig. 6

a sectional view of the foil punch in an end position,

Corresponding components are consistently provided in the figures with the same reference numerals.

Fig. 1 shows in a sectional view of a foil punch 1 according to the prior art with a lever mechanism 2 in order to move a tool lower part 3 vertically upward can. As a drive for the lever mechanism 2 is a pneumatic cylinder 4. The lever mechanism 2 transmits the movement of a piston of the pneumatic cylinder 4 on the lower tool part 3. The design of the lever mechanism 2, the stroke and the force of the lower tool part 3 are fixed. The lower tool part 3 is in Fig. 1 shown in its maximum upper position. In this case, a counter-pressure bar 6 of the lower tool part 3 is in contact with a knife 7a of a tool upper part 7. In order to adjust the compressive force exerted by the counter-pressure bar 6 on the knife 7a, the foil punch 1 setting wheels 8 to the knife 7a with a Accuracy of a few 1/100 millimeters in height and thus to be able to adjust relative to the counter-pressure bar 6 of the tool part 3. Due to the constant contact of the knife 7a on the back pressure bar 6 after cutting through a film, the cutting edge of the blade 7a blunts and the blade 7a has to be adjusted downwards in order to be able to maintain a good punching or cutting result. Incorrect settings can greatly affect the lifetime of the Messer 7a and counterpressure 6 bar.

In Fig. 2 is the force curve of the pressure force F, which is exerted by the counter-pressure bar 6 on the knife 7a, using a time-force diagram in a solid line on the example of the foil punch 1 from Fig. 1 shown. At time t0, the lower tool part 3 is in the lower basic position, in which the pneumatic cylinder 4 is fully retracted. The pneumatic cylinder 4 is then pressurized and moves the lower tool part 3 up to the film to be separated. At t1, the counter-pressure strip 6 of the lower tool part 3 strikes the foil and presses it with a force F1 against the knife 7a. t2 represents the moment of penetration or penetration and thus the cutting through of the film. Subsequently, the knife 7a is in contact with the counter-pressure strip 6 and the force F rises to a maximum value F2 which is generated by the pneumatic cylinder 4 and its compressed air supply and is also influenced by the upper end position of the pneumatic cylinder. At t3, the punching process is completed and the pressure of the pneumatic cylinder 4 is eliminated and thus also decreases the pressure force F to t4. From the time t4, the lower tool part 3 and the counter-pressure bar 6 away from the knife 7a and moves back to the normal position.

As can be seen from the diagram, the force F1 required to separate the film is less than half the maximum force F2 with which the counterpressure strip 6 still acts on the knife 7a after the separation process. In direct comparison to Prior art, the force curve according to the invention as a dash-dot line L is located. How this force curve is achieved will be explained in more detail with reference to the following figures.

Fig. 3 shows a schematic side view of a thermoforming packaging machine 10 according to the invention. The thermoforming packaging machine 10 has a forming station 11, a sealing station 12, a cross-cutting device in the form of a film punch 1 and a longitudinal cutting device 13, which are arranged in this order in a production direction R on a machine frame 14. On the input side is located on the machine frame 14, a feed roller 15, from which a film web 16 is withdrawn. In the region of the sealing station 12, a material reservoir 17 is provided, from which a cover film 18 is pulled off. On the output side, a discharge device 19 in the form of a conveyor belt is provided on the thermoforming packaging machine 10, with which finished, individualized packages 20 are transported away. Furthermore, the thermoforming packaging machine 10 has a feed device which grips the film web 16 and transports it further per main working cycle in the production direction R. The feed device can be designed, for example, by clamp chains arranged on both sides.

In the illustrated embodiment, the forming station 11 is formed as a thermoforming station in which troughs 21 are formed into the film web 16 by deep drawing. In this case, the forming station 11 may be formed such that in the direction perpendicular to the production direction R a plurality of wells 21 are formed side by side. In the production direction R behind the forming station 11, an insertion path 22 is provided in which the troughs 21 formed in the film web 16 are filled with products 23.

The cross-cutting device 1 is formed as a film punch, which cuts through the film web 16 and the cover film 18 in a direction transverse to the direction of production R between adjacent wells 21. In this case, the film lance 1 works in such a way that the film web 16 is not separated over the entire width, but is not severed at least in an edge region. This allows a controlled onward transport by the feed device.

The longitudinal cutting device 13 is formed in the illustrated embodiment as a knife assembly with a plurality of rotating circular blades, with which the film web 16 and the cover sheet 18 between adjacent troughs 21 and at the lateral edge of the film web 16 are severed, so that behind the longitudinal cutting device 13 individualized packages 20 are present.

The thermoforming packaging machine 10 also has a controller 26. It has the task to control the running in the thermoforming packaging machine 10 processes and monitor. A display device 27 with controls 28 serves to visualize or influence the process flows in the thermoforming packaging machine 10 for or by an operator.

Based on the following figures, the foil punch 1 and its function are explained in detail.

Fig. 4 shows a sectional view of the film punch 1 according to the invention in the production direction R in a basic position, in which the lower tool part 3 is in its lower position. As a drive for the lever mechanism 2, a servo motor 29 is provided which transmits the torque via a belt drive 30 to a spindle 31, preferably a ball screw, and thus converts the motor rotation into a linear movement. The spindle 31 lifts a carriage 32, which is guided on a vertical guide 33 at. Alternatively, a servo linear drive is also conceivable instead of the servomotor 29, the belt drive 30 and the spindle 31. The servomotor 29 with belt drive 30 and spindle 31 is referred to as a servo drive 50. In this case, the servo drive 50 also includes a controller 51 for the servo motor 29, wherein the controller 51 is connected to the controller 26. Alternatively, instead of the belt transmission 30, a gear transmission may be provided. The servo drive 50 further includes an incremental encoder or an absolute encoder on the spindle 31, preferably for detecting the linear movement of the spindle 31st

As the carriage 32 moves upwards (see FIG. FIG. 5 ) On both sides of the guide 33 each have a toggle lever 34 by means of a lever connection 35 which connects the carriage 32 with the toggle 34, actuated and spread. The knee lever spread causes a movement of a lifting plate 36 vertically upward, since the two toggle 34 are rotatably mounted respectively with a lower lever member 37 on a frame 39 and with an upper lever member 38 on the lifting plate 36. The lifting plate 36 is guided vertically over rollers 40 by means of the guide 33. Fig. 6 Shortly before this end position, the carriage 32 makes a lifting movement H1, for example of 20 mm, while doing the lifting plate 36 only a stroke H2 in the same direction, for example, by 1 mm ,

Fig. 6 further shows the controller 51 for the servo motor 29, wherein the controller 51 is connected to the controller 26. The controller 51 detects the motor current of the servomotor 29 and passes this information to the controller 26 on. The motor current is approximately proportional to the compressive force F, which in Fig. 2 shown in the diagram.

Alternatively or additionally, the pressure force can also be detected via at least one pressure sensor 42 as a measuring unit, which is arranged in the force flow of the lever mechanism 2, the upper tool part 7 and the lower tool part 3, for example as in Fig. 6 shown between the lower end of a holder 43 for the upper tool part 7 and a receiving part 44 of the frame 39 for the holder 43. It can also be two pressure sensors 42 symmetrically right and left provided on the holders 43.

In a further alternative embodiment of the measuring unit, a vibration sensor 45 or structure-borne sound sensor can be provided on the tool upper part 7 in order to detect the contact or impact of the lower tool part 3 or the counterpressure rail 6 on the upper tool part 7 or of the knife 7a.

To determine the working position, the lower tool part 3 as in the FIGS. 4 to 6 shown moved up to the tool upper part 7. The movement speed can be lower and thus gentler than during the other production process. In a particularly advantageous embodiment of the method, no film web 16 is present in this process, so that the lower tool part 3 can be moved without executing a cutting force on the upper tool part 7.

In all cases, the controller 26 determines based on the determined data of the measuring unit 41, 42 or 45, the end or contact position as a working position of the lower tool part 3 and the carriage 32, which corresponds to a specific position of the servo motor 29 and the spindle 31. The controller 26 positions the tool base 3 for the punching process in the working position, but not further. This results in a force curve L, see Fig. 2 , shown as a dashed-dotted line L in direct comparison to an embodiment according to the prior art. He has the advantage over the prior art, that the maximum force is barely higher than that for the cutting of the foil care.

The spindle 31 may optionally (see Fig. 6 ) have a housing 60 with a degree of protection IP 65, in which case preferably a pressure compensation device 61 may be provided in the form of a lead out into the environment line. Such a design is particularly hygienic, since the housing 60 is then carried out both dustproof and can be cleaned with jet water.

Instead of a spindle 31, the servo drive 50 may have a connecting rod drive.

In a variant, the knife 7a may be provided on the tool lower part 3 and the counter-pressure strip 6 on the tool upper part 7.

Ideally, the method according to the invention is carried out regularly, e.g. weekly, daily or at every machine start. For subsequent operation, the foil punch 1 is then always set optional, regardless of any wear of the blade 7a. In this way, the cutting tools of the foil punch must be manually readjusted or replaced much less frequently than in the prior art, which considerably improves the operation of the foil punch 1 and the entire packaging machine.

Claims (9)

1. A thermoform packaging machine (10), comprising a controller (26) and a film punch (1), which includes a lever mechanism (2), a tool upper part (7) and a tool lower part (3), wherein at least the tool upper part (7) or the tool lower part (3) are movable by means of the lever mechanism (2) such that the tool upper part (7) and the tool lower part (3) approach each other, characterized in that the film punch (1) comprises a servo drive (50) and that a measuring unit (51, 42, 45) is provided, which is configured to detect a contact between the tool upper part (7) and the tool lower part (3).
2. The thermoform packaging machine according to claim 1, characterized in that the controller (26) is connected to the measuring unit (51, 42, 45), and that the position of the tool upper part (7) and/or of the tool lower part (3) at a working position can be calculated by means of the controller (26).
3. The thermoform packaging machine according to one of the preceding claims, characterized in that the measuring unit is a governor (51) of the servo drive (50).
4. The thermoform packaging machine according to one of the claims 1 or 2, characterized in that the measuring unit is a pressure sensor (42) or an impact-sound or vibration sensor (45).
5. The thermoform packaging machine according to one of the preceding claims, characterized in that the servo drive (50) comprises a servomotor (29), a governor (51) and a spindle (31), preferably a ball screw.
6. A method of determining the working position of a movable tool lower part (3) or a movable tool upper part (7) of a thermoform packaging machine (10) comprising a controller (26) and a film punch (1), wherein the film punch (1) comprises the tool lower part (3) and the tool upper part (7), which are moved by a lifting mechanism (2) and which approach each other during this movement, characterized in that, as the tool lower part (3) and the tool upper part (7) approach each other, a contact between the tool lower and tool upper parts (3, 7) is detected by means of the controller (26) on the basis of an evaluation of data of the measuring unit (51, 42, 45).
7. The method according to claim 6, characterized in that the measuring unit is a governor (51) for a servomotor (29) of a servo drive (50) of the film punch (1), and that, on the basis of the current consumption of the servomotor (29), the force progression of the force acting on the movable tool (3, 7) is detected.
8. The method according to claim 6, characterized in that the measuring unit is a pressure sensor (42) and that a measurement of force is carried out at the tool lower or tool upper part (3, 7).
9. The method according to one of the claims 6 to 8, characterized in that the controller (26) determines an end position for the movable tool lower or tool upper part (3, 7).

Images