Method for producing a package

Abstract

A method for producing a package which has a formed part with a product cavity, and a lidding film covering the product cavity. According to the method, a seam is defined, the seam is divided into sections, a pull-off force for pulling the lidding film from the formed part at least for a first section is determined, and the lidding film is sealed to the formed part. The sealing temperature for the first section is selected based on the pull-off force.

Claims

1. A method for producing a package comprising a formed part having at least one product cavity, and a lidding film covering the at least one product cavity, wherein the lidding film is to be pulled off from the formed part in a pull-off direction, wherein the method comprises the steps of: (a) defining a seam to be produced, along which the lidding film is to be sealed to the formed part around the at least one product cavity; (b) dividing the seam to be produced into a plurality of sections, which comprise a first section, a second section, and a third section, wherein the first section, the second section and the third section are arranged one behind the other in the pull-off direction, wherein the first section is a tear-open section, in which the lidding film is to be separated first from the formed part to open the package, wherein the second section is a pull-off section, in which the lidding film is to be pulled away in the pull-off direction from the first section toward the third section to open the package; wherein the third section is an end section, which is arranged behind the first and the second sections with respect to the pull-off direction, and in which the lidding film remains connected to the formed part for the longest period of time during opening of the package; (c) determining, at least for the first section of the plurality of sections, a first pull-off force for pulling the lidding film from the formed part; (d) sealing the lidding film to the formed part along the seam by means of a sealing device with a first sealing temperature in the first section and a second sealing temperature in the second section, wherein the first and the second sealing temperatures are different, wherein at least the first sealing temperature for the first section is selected based on the first pull-off force determined according to step (c); and wherein a third sealing temperature for the third section differs from the first sealing temperature and/or second sealing temperature.

2. The method according to claim 1, wherein step (c) comprises determining a pull-off force for pulling the lidding film from the formed part for each section of the plurality of sections.

3. The method according to claim 1, wherein step (d) comprises the step of: setting sealing temperatures of the sealing device for each section of the plurality of sections, wherein at least the first sealing temperature for the first section is set based on the first pull-off force determined according to step (c).

4. The method according to claim 1, wherein the first pull-off force for the first section and/or a second pull-off force for the second section is between 2 N and 20 N.

5. The method according to claim 1, wherein a third pull-off force for the third section is more than 15 N.

6. The method according to claim 1, wherein determining at least the first pull-off force according to step (c) comprises the step of defining a maximum first pull-off force.

7. The method according to claim 1, wherein determining at least the first pull-off force according to step (c) comprises the step of defining a minimum pull-off force.

8. The method according to claim 7, wherein determining at least the first pull-off force according to step (c) further comprises the steps of determining a second pull-off force for the second section and defining a minimum second pull-off force for the second section.

9. The method according to claim 1, wherein the seam around the at least one product cavity has a length which is between 25 mm and 600 mm.

10. The method according to claim 1, wherein the sealing device comprises a sealing contour, which is divided into a plurality of segments, wherein at least a first segment of the plurality of segments is assigned to the first section of the seam and at least a second segment of the plurality of segments is assigned to the second section of the seam, and step (d) comprises the step of heating the plurality of segments in accordance with the first and second sealing temperatures.

11. The method according to claim 10, wherein the plurality of segments of the sealing contour comprises at least four segments.

12. The method according to claim 10, wherein the sealing device comprises a plurality of heating elements, wherein one heating element of the plurality of heating elements is assigned to each segment of the plurality of segments, wherein the step of heating the plurality of segments is performed by means of the plurality of heating elements.

13. The method according to claim 1, wherein the sections of the plurality of sections of the seam are arranged adjacent to each other and continuously along the seam, wherein the sealing according to step (d) is performed along the entire seam around the at least one product cavity.

14. A method for producing a package comprising a formed part having at least one product cavity, and a lidding film covering the at least one product cavity, wherein the method comprises the steps of: (a) defining a seam to be produced, along which the lidding film is to be sealed to the formed part around the at least one product cavity; (b) dividing the seam to be produced into a plurality of sections, which comprise at least a first section and a second section of the plurality of sections; (c) determining, at least for the first section of the plurality of sections, a first pull-off force for pulling the lidding film from the formed part; (d) sealing the lidding film to the formed part along the seam by means of a sealing device with a first sealing temperature in the first section and a second sealing temperature in the second section, wherein the first and the second sealing temperatures are different, and wherein at least the first sealing temperature for the first section is selected based on the first pull-off force determined according to step (c); wherein step (b) comprises the steps of: (b1) determining a reference curve, which is characteristic of a change in a reference pull-off force of a reference package versus a separation length in the pull-off direction; (b2) determining the plurality of sections on the basis of the reference curve and dividing the seam into the plurality of sections correspondingly.

15. The method according to claim 14, wherein step (c) comprises the steps of: (c1) defining an area of the reference curve, in which the reference pull-off force lies outside a tolerance range; (c2) determining the first section of the plurality of sections of the seam, which corresponds to the area in which the reference pull-off force lies outside the tolerance range; and (c3) determining the first pull-off force for the first section of the seam determined according to step (c2), such that the first pull-off force of the first section lies within the tolerance range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a perspective view of an embodiment of a sealing device for producing a package;

(2) FIG. 2 shows a schematic cross-sectional view of part of the sealing device according to FIG. 1;

(3) FIG. 3 shows a schematic top view of the sealing device according to FIG. 1;

(4) FIGS. 4a and 4b show perspective views of an exemplary embodiment of a package with and without a lidding film;

(5) FIG. 5 shows a top view of a formed part of the package according to FIG. 4;

(6) FIG. 6 shows schematically a reference curve of a pull-off force; and

(7) FIG. 7 shows a top view of the formed part of the package according to FIG. 4; and

(8) FIGS. 8a and 8b show flow charts of a method for producing the package.

DETAILED DESCRIPTION

(9) FIG. 1 shows a perspective view of an embodiment of a sealing device 2. The sealing device 2 comprises a sealing contour 4, which is configured to come in contact with a lidding film of a package to be sealed (see FIG. 4). For heat-sealing the lidding film to a formed part of the package to be sealed, the sealing device 2 comprises a heater 6, which heats the sealing contour 4 and is thus in thermally conductive contact with the sealing contour 4. The heater 6 can be connected by means of an insulating body 8 of the sealing device 2 to a housing 10 of the sealing device 2. The insulating body 8 insulates the housing 10, the components accommodated therein, and the rest of the sealing device 2 thermally from the heater 6, so that the heat it generates is conducted effectively to the sealing contour 4.

(10) A control unit 12 for the open-loop and/or closed-loop control of the sealing device 2 can be accommodated in the housing 10, for example. The control unit 12 is connected to the heater 6. The control unit 12 and the heater 6 can be supplied with power and possibly other control signals by way of a terminal 13. It is also conceivable that the control unit 12 could be provided outside the housing 10 and that the control signals could be transmitted to the heater 6 over an appropriate line connected to the terminal 13 or wirelessly.

(11) As shown in FIG. 1, the sealing contour 4 is substantially ring-shaped and encloses a central area 14, where the sealing device 2 does not have a sealing contour 4. The sealing contour 4 preferably has a shape which corresponds substantially to the shape of the seam to be produced (see FIGS. 3-5), as a result of which the heat input from the sealing device 2 can be effectively directed and concentrated to the area of the desired seam. The sealing contour 4 can project beyond other components and areas, in particular beyond the central area 14. In the embodiment shown, this is achieved in that the sealing contour 4 comprises a protective layer 16, which protects the heater 6 and is made of a material having good thermal conductivity. The sealing contour 4, however, can also be configured as an integral part of the heater 6, which then has a corresponding profile.

(12) The sealing device 2 may further comprise at least one suction opening 18 for drawing up the lidding film, thereby enabling the sealing device 2 to arrange the lidding film on the formed part prior to sealing. Here, the sealing device 2 comprises a plurality of such suction openings 18, which are connected to a source of negative pressure, such as a vacuum pump, by way of an appropriate connector 20 on the housing 10 and which are arranged within the sealing contour 4 in the central area 14 of the sealing device 2.

(13) In one embodiment, the sealing device 2 may be configured to seal a plurality of packages or one package having a plurality of product cavities and seams at the same time. In this case, the sealing device 2 comprises a plurality of sealing contours 4 corresponding to the number of product cavities, as indicated in FIG. 1 by the housings 10′ and 10″ shown in broken line by way of example, on each of which a sealing contour and a heater configured analogously to that of the previously described sealing device 2 are provided.

(14) FIGS. 2 and 3 show details of the sealing device 2, in particular of the heater 6. The sealing device 2, namely the heater 6 of the sealing device, preferably comprises a plurality of heating elements 22 for heating the sealing contour 4. The sealing device 2 may further comprise a plurality of sensor elements 24, which are preferably configured to detect the temperature of the heating elements 22 and/or of the sealing contour 4. The plurality of heating elements 22 and the plurality of sensor elements 24 can be configured as strip conductors, respectively, but may also be formed by wires. The plurality of heating elements 22 and the plurality of sensor elements 24 may be applied to a carrier substrate 26. For example, the strip conductors could be printed on a side of the carrier substrate 26 facing the lidding film, i.e., the side of the carrier substrate 26 facing away from the insulating body 8. The carrier substrate 26 is preferably made of ceramic material. As a result, a highly dynamic heater 6 with effective local control is provided. The protective layer 16 can cover the plurality of heating elements 22 and the plurality of sensor elements 24 to protect them from wear, as shown in FIG. 2. In the top view according to FIG. 3, the sealing contour 4 and protective layer 16 are shown only partially, in dashed line, so that the heating elements 22 can be seen more clearly.

(15) In the embodiment according to FIG. 2, the heating elements 22 of the plurality of heating elements 22 are formed separately from the sensor elements 24 of the plurality of sensor elements 24, e.g., by separate wires, strip conductors, or sensors.

(16) In the embodiment according to FIG. 3, one heating element 22 and one sensor element 24 are configured as an integral unit, here, for example, as a single strip conductor. That is, each of the plurality of heating elements 22 is combined with one of the plurality of sensor elements 24 in an integral element. This can be achieved, for example, in that the plurality of heating elements 22 are electrical resistance heaters. Consequently, their resistance changes as a function of temperature, the temperature thus being detectable on the basis of the resistance of the heating element 22. Unless otherwise described, either of the two embodiments can be used as desired and combined with any of the other features of the sealing device 2 described herein.

(17) As can be seen from a consideration of FIGS. 1 and 3 together, the sealing contour 4 is divided into a plurality of segments 28. In the exemplary embodiment shown in FIG. 3, the plurality of segments 28 comprises eight segments 28a, 28b, 28c, 28d, 28e, 28f, 28g, 28h. The sealing contour 4 does not have to be divided structurally into segments 28a-h. For example, the sealing contour 4 can, as shown, be divided “imaginary” into the segments 28a-h in correspondence with the arrangement of the plurality of heating elements 22, so that each segment 28a-h comprises one heating element 22 of the plurality of heating elements 22 and preferably one sensor element 24 of the plurality of sensor elements 24. The segments 28a-h preferably are arranged directly adjacent to each other and continuously along the sealing contour 4. Each heating element 22 heats a corresponding segment 28a-h of the sealing contour 4 assigned to it, and each sensor element 24 monitors a corresponding segment 28a-h of the sealing contour 4 assigned to it, in particular its temperature. As a result, each segment 28a-h of the plurality of segments 28 can be actuated and monitored individually.

(18) FIGS. 4a and 4b show perspective views of a package 30, which can be produced by means of the sealing device 2 and method described herein. The package 30 comprises a formed part 32, in which a product cavity 34 has been formed, and a lidding film 36, which is sealed to the formed part 32. For the sake of illustration and clarity, the lidding film 32 is shown only in FIG. 4b, whereas, in FIG. 4a, it has been omitted to reveal the features underneath. The formed part 32 can be an injection-molded part, as used, for example, for the packaging of contact lenses, or it may be a blister pack, as used, for example, for the packaging of pharmaceutical products. The product cavity 34 is preferably configured as a pocket in the formed part 32 and preferably receives a product and/or a fluid (not shown). The formed part 32 preferably comprises a flange 38, which surrounds the product cavity 34 and contacts the lidding film 36.

(19) The lidding film 36 is sealed to the formed part 32 along a seam 40, which surrounds the product cavity 34. For this purpose, the flange 38 may provide a sealing surface, on which the seam 40 is formed.

(20) The lidding film 36 comprises a first, free area 41, which is not connected to the formed part 32, and which is also called a tear-open tab 41. The tear-open tab 41 can be gripped by a user to pull the lidding film 36 away from the formed part 32. A pull-off direction, in which the lidding film 36 is to be pulled to open the package 30, is indicated in FIG. 4b by the arrow X. The pull-off direction X extends from the tear-open tab 41 toward an end section 43 of the lidding film 36. The end section 43 is the section which remains connected to the formed part 32 for the longest period of time when the package 30 is being opened, or it can even be permanently connected to the formed part 32.

(21) FIG. 5 shows a top view of the formed part 32 of the package 30, wherein, for the sake of illustrating the seam 40 surrounding the product cavity 34, the lidding film 36, which is sealed to the formed part 32 along the seam 40, is not shown. The seam 40 completely surrounds the product cavity 34 to seal off the product cavity 34 in a leak-proof fashion. As can be derived from FIGS. 3 and 5 in combination, the seam 40 and the sealing contour 4 of the sealing device 2 preferably have corresponding shapes.

(22) For the sake of a better understanding, the division of the plurality of segments 28 of the sealing contour 4, which contacts the lidding film 36 to form the seam 40, is also indicated in FIG. 5. As can be seen, the seam 40 can be divided into a plurality of sections A1, A2, A3 (see FIG. 7), to each of which one or more segments 28a-h of the sealing contour 4 can be assigned.

(23) FIG. 6 shows by way of example a force-displacement diagram for the pull-off force F required to pull the lidding film 36 from the formed part 32, wherein the displacement corresponds to the separation length L also indicated in FIG. 7. A conventional pull-off force or peel force curve, as described above, has an initial peak 44, a plateau 46, and a final peak 48. As shown in FIG. 7, the separation length L is preferably defined to be parallel to the pull-off direction X.

(24) The pull-off force curve according to FIG. 6 can be considered a reference curve of a reference package. The reference package can correspond to the package of FIG. 4, wherein the lidding film 36 has been sealed to the formed part 32 along the sealing contour 4 by the use of initial sealing parameters, in particular by the use of a uniform sealing temperature.

(25) FIG. 6 also shows a minimum force F.sub.min and a maximum force F.sub.max. The minimum force F.sub.min corresponds to a predetermined pull-off force necessary for a sufficiently strong bond of the lidding film 36 to the formed part 32, in particular to provide a sufficiently leak tight seam 40. The maximum force F.sub.max corresponds to a predetermined pull-off force up to which it is possible to remove the lidding film 36 easily from the formed part 32. It can be derived from the diagram that the initial peak 44 and the final peak 48 exceed the maximum force F.sub.max.

(26) With the method described herein, it is now possible to effectively reduce the pull-off force in areas in which it lies outside of a desired tolerance range, e.g. in the area of the initial peak 44 and of the final peak 48, without simultaneously having the effect of lowering the pull-off force in other areas, such as the area of the plateau 46, below the minimum force F.sub.min.

(27) A method according to an embodiment of the present disclosure is described below with reference to FIGS. 6-8.

(28) First, the seam 40 to be produced and in particular its course around the product cavity 34 and its geometric configuration are defined in step (a), as can be seen for example, in FIGS. 4, 5, and 7. Then the seam 40 to be produced is divided in step (b) into a plurality of sections A1, A2, and A3, which comprise at least a first section A1 and a second section A2 and, in this embodiment, also a third section A3 (see FIG. 7). Dividing the seam 40 into sections A1, A2, and A3 can, for example, be carried out based on empirical values, on the layout of the seam 40, or on a feedback control/optimization process by the control unit 12.

(29) In a preferred embodiment, dividing the seam 40 to be produced according to step (b) is performed on the basis of a reference curve like the one shown in FIG. 6. The reference curve corresponds to a characteristic course of a reference pull-off force of a reference package versus the distance of displacement L (i.e. the separation length) in the pull-off direction X. For this purpose, the reference curve of the reference package may first be determined in step (b1).

(30) Then, the plurality of sections A1, A2, A3 is determined based on the reference curve, and the seam 40 is divided into the plurality of sections A1, A2, A3 (step (b2)). In particular, boundaries between the sections A1, A2, A3 can be defined on the basis of the diagram of the reference curve. For example, a first length L.sub.1 of the separation length L is determined in such a way that the initial peak 44 lies between the starting point L.sub.0, at which the lidding film is first separated from the formed part, and the first length L.sub.1. A second length L.sub.2 can be selected in such a way that the plateau 46 lies between the first and second lengths L.sub.1, L.sub.2. Finally, a third length L.sub.3 can be determined in such a way that the final peak 48 lies between the second and third lengths L.sub.2, L.sub.3. As shown in FIG. 7, the first, second and third lengths L.sub.1, L.sub.2, L.sub.3 can then be transferred to the package 30 and seam 40. In this way, the sections A1, A2, and A3 of the seam 40 are defined in accordance with those areas of the pull-off force on which different requirements are imposed.

(31) As shown seen in FIG. 7, the lengths L.sub.1, L.sub.2, and L.sub.3 can be transferred to the package 30 in the pull-off direction X to determine in this way the sections A1, A2, and A3 of the seam 40. The first section A1 of the seam 40 therefore corresponds to the first length L.sub.1 of the separation length, the second section A2 of the seam 40 corresponds to the second length L.sub.2 of the separation length, and the third section A3 of the seam 40 corresponds to the third length L.sub.3 of the separation length. The first, the second, and the third sections A1, A2, A3 are arranged one behind the other in the pull-off direction X.

(32) From FIGS. 4 and 7 in combination, it can be seen that the first section A1 in this exemplary embodiment is a tear-open section, in which the lidding film 36 is separated first from the formed part 32 to open the package 30 and in the area of which the lidding film 36 preferably comprises the tear-open tab 41. The second section A2 is a pull-off section, in which the lidding film 36 is to be pulled off in the pull-off direction X toward the third section A3. Here, the second section A2 comprises two subsections, i.e. a left and a right section, of the seam 40, which are connected to each other by the first and third sections A1, A3. The third section A3 is an end section, which remains connected to the formed part 32 for the longest period of time during the opening of the package 30, or it could even be permanently connected to the formed part 32.

(33) According to step (c), a pull-off force F for pulling the lidding film 36 from the formed part 32 is determined for at least one section of the plurality of sections A1, A2, A3, wherein at least a first pull-off force F is determined for the first section A1. A pull-off force is preferably determined for each section, i.e., also a second pull-off force F for the section A2 and a third pull-off force for the third section A3.

(34) For this purpose it is possible, according to step (c), to specify in advance a nominal pull-off force and to store it in the system, which can then be used by the control unit 12. Step (c), however, can also comprise the step of defining the maximum pull-off force F.sub.max. In addition or as an alternative, step (c) can comprise the step of defining the minimum pull-off force F.sub.min. In the example shown in FIGS. 6 and 7, step (c) comprises defining of a maximum first pull-off force for the first section A1 and a minimum second pull-off force for the second section A2, as previously described.

(35) The step of determining the pull-off force for at least one section according to step (c) can also be carried out on the basis of the reference curve (FIG. 6), as shown in FIG. 8b. Step (c) therefore preferably comprises the steps of defining of an area of the reference curve in which the reference pull-off force lies outside a tolerance range (step (c1)) and of determining the section of the plurality of sections A1, A2, A3 of the seam 40 which corresponds to the area in which the reference pull-off force lies outside the tolerance range (step (c2)). For the section determined according to step (c2), a pull-off force which lies within the tolerance range is then determined in step (c3).

(36) For example, the tolerance range can be defined between the minimum and the maximum pull-off forces F.sub.min, F.sub.max (see FIG. 6), and the area of the reference curve lying outside this tolerance range would be the area of the initial peak 44. The first section A1 would be determined accordingly in step (c2), because it corresponds to the area in which the pull-off force comprises the initial peak 44. According to step (c3), a pull-off force is then defined between the minimum and the maximum pull-off forces F.sub.min, F.sub.max for the first section A1.

(37) Now, the lidding film 36 can be sealed to the formed part 32 according to step (d). To do so, sealing temperatures of the sealing device 2 are set. At least for the first section A1 for which the pull-off force has been previously determined according to step (c), the sealing temperature is adjusted based on the pull-off force determined according to step (c). In the present example, therefore, the sealing temperature for the first section A1 is set lower than the sealing temperature of the first section of the reference package in order to obtain a lower sealing strength and thus a lower pull-off force in the first section A1, which preferably lies below the predetermined maximum pull-off force. Because the sealing temperature at least of the first section A1 is changed, the first sealing temperature for the first section A1 and a second sealing temperature for the second section A2 differ from each other. If, in this example, the second sealing temperature in the second section A2 would be decreased as well, there would be the danger of the pull-off force in the second section A2 falling below the minimum pull-off force F.sub.min.

(38) It can be seen in FIG. 7 that at least a first segment 28a of the sealing contour 4 is assigned to the first section A1, and at least a second segment 28b of the sealing contour 4 is assigned to the second section A2. In addition, the segment 28h may also be assigned to the first section A1, and the segments 28c, f, g may also be assigned to the second section A2. The segments 28d and 28e are assigned here to the third section A3.

(39) Because the sealing temperature can be set individually in each segment 28a-h by means of the plurality of heating elements 22 (see FIG. 3) as described above, setting the sealing temperature of the sealing device 2 comprises the step of setting the sealing temperature of each segment 28a-h. Consequently, each section A1, A2, A3 of the seam 40 can be sealed with an individual sealing temperature as desired.

(40) Once the appropriate settings of the sealing device 2 have been made, the lidding film 36 can be sealed to the formed part 32 along the seam 40 according to step (d). For this purpose, the plurality of segments 28 of the sealing contour 4 are heated in accordance with the set sealing temperatures and brought into contact with the lidding film 36 to seal the lidding film 36 to the formed part 32, thereby forming the seam 40. As a result, the package 30 is produced, the lidding film 36 of which can be separated from the formed part 32 with the desired pull-off force in the pull-off direction X, wherein the pull-off force in the pull-off direction X is adjusted as desired in such a way that a sufficiently strong bond is obtained and the package is easy to open at the same time.