Device and method of sealing packages

Abstract

A device for sealing packages comprises a sealing bar (1, 2). It is the object of the present invention to provide a sealing bar which solves the problems of lacking evenness of the sealing bar due to manufacturing tolerances. Advantageously, the quality of the sealing seam shall be enhanced. This object is solved by a compressible, heat conducting material (5) provided on the sealing bar (1, 2).

Description

The present invention refers to a device and method of sealing packages.

For instance, in the field of packages for medical aseptic goods, validation of the packaging processes is required by the qualification department. The validation is to ensure that the process having the same parameters always leads to the same result. Among other things, this pertains to the packaging machine itself. One component to be validated is the sealing bar. In order to assure the reproducibility of a sealing seam, the real process parameters of sealing time, sealing pressure and sealing temperature must agree with the input requirements.

In a prepared concept of pulse sealing, where a wire is heated by an electric current pulse, the validation of the sealing time is possible just like that. Moreover, the sealing pressure can also be indirectly measured via a diaphragm exerting the pressure. However, the sealing temperature can not be adjusted. The sealing temperature results from the sealing time, the remaining heat of the previous sealing operation, the ambient temperature, the electric resistance of the wire and the applied voltage. Direct presetting of the sealing temperature is not possible, since the small mass of the wire and the shortness of the sealing time do neither allow a measurement of the heating process nor a feedback control thereof. Therefore, sealing methods have been developed, which can be validated.

In such a thermo-controlled (TC) method, a solid aluminium profile is continuously heated. The significant higher mass and the thermal buffer capacity being involved therewith can feedback control the sealing temperature with sufficient accuracy due to time mitigation. For common package material of high quality, which is manually inserted into the machine without crinkles, this method creates acceptable sealing results. Using cheaper package materials, sealing by means of a continuously heated sealing bar will be difficult due to the limited time frame of the process. If the product shall be packed by an automatic conveyor belt chamber machine, for instance, unavoidable crinkles in the sealing area result in a package which is not properly sealed. Since the heat must pass through all web layers during sealing on one side, either the upper layers get too hot and flow away or the lower layers are insufficiently heated, whereby the crinkles are not sealed through.

An obvious solution as also used by the pulse sealing method is the use of a second sealing bar. The poach is heated both above and below.

The realization of a reliable device for sealing above and below is, however, difficult with two sealing bars of aluminium, for instance. The sealing bars must be accurately aligned to each other to be flush with each other when webs having a thickness of 100 μm or less are used, since the sealing pressure is not uniformly applied. In addition to the thermal deformation during operation, the sealing bars are formed concave or convex caused by the manufacture thereof so that gaps of 0.1 to 0.3 mm are created. This is not allowable in particular during sealing medical products.

It is the object of the present invention to provide a sealing bar which solves the above-mentioned problems caused by manufacturing tolerances. Advantageously, the quality of the sealing seam shall be improved.

This object is solved by the device according to claim 1. The object is also solved by the method according to claim 12. Further developments of the invention are indicated in the respective dependent claims.

By means of the sealing bar according to the invention, the manufacturing tolerances and the thermal deformations can be compensated for during the sealing operation by a metal meshwork provided at the sealing face. In addition to the desired flexibility for compensating for tolerances and tilting, the metallic material enables good heat conduction for optimum sealing. For instance, this is indispensable and required by law, respectively, for medical products to be packed. Since manufacturing of sealing bars does not need high demands in dimensional accuracy due to the following integration of the metal meshwork, the manufacturing of the sealing bars is considerably cheaper.

Further features and advantages of the invention are disclosed in the description of embodiments together with the enclosed drawings. In the Figures show:

FIG. 1 a schematic overall view of a packaging machine embodied by a chamber machine;

FIG. 2 a schematic cross-section view of a station for sealing above/below;

FIG. 3a a cross-sectional view of an upper and a lower sealing bar in a home position before sealing;

FIG. 3b a cross-section view of an upper and a lower sealing bar in a sealing position;

FIG. 3c a cross-sectional view of an upper and a lower sealing bar in the home position after sealing;

FIG. 4a a cross-sectional view of an upper sealing bar tilted about the Z-axis, and a lower sealing bar in a home position;

FIG. 4b a cross-sectional view of an upper sealing bar tilted about the Z-axis, and a lower sealing bar in a sealing position;

FIG. 5a a cross-sectional view of an uneven upper sealing bar and a lower sealing bar in a home position;

FIG. 5b a cross-sectional view of an uneven upper sealing bar and a lower sealing bar in a sealing position;

FIG. 6a a side view of an upper sealing bar tilted about the X-axis, and a lower sealing bar in a home position;

FIG. 6b a side view of an upper sealing bar tilted about the X-axis, and a lower sealing bar in a sealing position;

FIG. 7a a side view of an uneven upper sealing bar and a lower sealing bar in a home position;

FIG. 7b a side view of an uneven upper sealing bar and a lower sealing bar in a sealing position.

In the following, a first preferred embodiment of the present invention is described with reference to the figures on the basis of an example of a chamber machine.

FIG. 1 shows a chamber machine 10 having a housing 11, a chamber bottom 12 and a lid 13. In the lid 13, there is a sealing member 15 cooperating with a counter-pressure member 14 by closing the lid 13. In this manner, a poach can be sealed, for instance. The sealing member 15 and the counter-pressure member 14 are described in more detail in FIGS. 2 to 7. The sealing member 15 corresponds to the first sealing bar 1, and the counter-pressure member corresponds to a counter-bearing and a second sealing bar 2, respectively.

FIG. 2 shows a cross-sectional view of the upper first sealing bar 1 having a first heating device 3 and the lower, second sealing bar 2 having a second heating device 4. The heating devices 3, 4 extend in the shape of heating rods and tubular heating elements, respectively, over the entire length of the sealing bars 1, 2, and in the depicted example, they are provided in the sealing bars 1, 2. By using of two heated sealing bars 1, 2, the heat introduction is effected on both sides, which is particularly advantageous for reliable sealing of thick webs.

In the enlarged view of FIG. 2, there is shown the lower, second sealing bar 2. On the upper side thereof, there is a compressible elastic material 5 in the shape of a metal meshwork 5 extending over the entire sealing face 9. In this manner, an optimum sealing operation is achieved with constant sealing pressure irrespective of unevenness or form tolerances of the metal sealing bars 1, 2. Above the metal meshwork 5, there is a retaining strip 6, for instance a Teflon strip, which also extends over the entire sealing face 9 of the sealing bar. The strip prevents the sealing bar from adhering on the package material and on the used web, respectively. Additionally, the strip 6 retains the metal meshwork in the desired form on the sealing bar. The strip 6 can be fixed on the sealing bar by gluing, for instance.

The metal meshwork 5 can compensate for a plurality of form deviations and, hence, continuously provides a constant sealing pressure for ensuring the optimum quality of the sealing seams. It can be used in a woven form, for instance, i.e. with longitudinal and transverse fibres. Moreover, other embodiments such as fabric like steel wool are conceivable.

With reference to the FIGS. 3 to 7, the operation of the device and method according to the present invention is described as follows.

FIG. 3a shows a cross-sectional view of the first sealing bar 1 and the second sealing bar 2 provided with the metal meshwork 5 in the home position, wherein both sealing bars are provided with the heating devices 3, 4, as it is already shown in FIG. 2. Between those sealing bars 1, 2, there is a package material 7 in the shape of a poach having a top web and a bottom web, for instance, which are sealed to each other during the sealing operation, as it is shown in FIG. 3b. At the same time, a sealing seam 8 is created. FIG. 3c shows both sealing bars 1, 2 in the initial position and in the home position, respectively, and the created sealing seam 8. The sealing bars 1, 2 can be formed with a T-shaped cross-section, for instance. In this manner, the bars are stronger and apply a constant heat introduction into the package material to be sealed, thereby enhancing the quality of the sealing seam 8.

FIGS. 4a, 4b show like FIGS. 3a, b the first and the second sealing bars 1, 2 in the home and sealing positions. The first sealing bar 1 is tilted about the longitudinal axis thereof relative to the second sealing bar 2, i.e. about the Z-axis. FIG. 4b shows how the metal meshwork 5 compensates for the tilting of the first sealing bar 1 during the sealing operation.

FIGS. 5a, 5b show like in FIGS. 4a, b the first and the second sealing bar 1, 2 in the home and sealing positions, respectively. The first sealing bar 1 is unevenly formed due to manufacturing tolerances, for instance. FIG. 5b shows how the metal meshwork 5 compensates for the unevenness of the first sealing bar 1 during the sealing operation.

FIG. 6a shows a side view of the first and the second sealing bars 1, 2. The first sealing bar 1 is tilted in a vertical plane relative to the second sealing bar 2, i.e. about the X-axis.

FIG. 6b shows how the metal meshwork 5 compensates for the tilting of the first sealing bar 1.

FIG. 7a shows a side view of the first and the second sealing bars 1, 2. The first sealing bar 1 is unevenly formed due to form tolerances, for instance. FIG. 7b shows how the metal meshwork 5 compensates for the unevenness of the first sealing bar 1.

The present invention is not limited to the use of the metal meshwork. Instead of it, the use of other heat conducting materials such as specifically adapted plastics having heat conducting fillers or ceramics with good heat conductance such as aluminium nitride are conceivable.

The sealing bars are not limited to the T-shaped cross-sectional form. Any forms and shapes such as rectangle or triangular forms of the sealing bars are conceivable.

Instead of a Teflon strip on the sealing bar, other components having anti-adhesive materials are conceivable. Instead of a strip, which is glued on the ceiling bar, other fixing mechanism such as rivets or clips are conceivable.

The invention is not limited to the use in chamber machines, either. The device according to the present invention can be incorporated in any packaging machine such as a deep drawing machine, a thermo former or a chamber machine, where a sealing operation is carried out.

The individual features of the disclosed embodiment can be freely combined with each other.

Claims

1-17. (canceled)

18. A device for sealing of packages, comprising a first sealing bar having a sealing face and a compressible, heat conducting material provided on the sealing bar at the sealing face.

19. The device according to claim 18, wherein the material is elastic.

20. The device according to claim 18, wherein the material comprises a metal meshwork.

21. The device according to claim 18, further comprising a counter-bearing.

22. The device according to claim 18, further comprising a second sealing bar that is provided as a counter-bearing, wherein a sealing operation is performed therebetween.

23. The device according to claim 22, wherein each of the first sealing bar and the second sealing bar comprises a contact face adapted to receive a package material therebetween.

24. The device according to claim 22, wherein said second also comprises a compressible, heat conducting material.

25. The device according to claim 18, wherein the compressible, heat conducting material extends over the entire sealing face.

26. The device according to claim 18, wherein the compressible, heat conducting material has a side opposite to the sealing bar, and further comprising a strip on the side of the compressible, heat conducting material.

27. The device according to claim 26, wherein the strip comprises Teflon.

28. The device according to claim 18, wherein the first sealing bar comprises a heating device.

29. The device according to claim 22, wherein at least one of the first sealing bar and the second sealing bar comprises a heating device

30. A method of sealing packages, said method comprising: pressing a first sealing bar to a counter-bearing; and providing a compressible, heat conducting material on the first sealing bar.

31. The method according to claim 30, further comprising forming the counter-bearing with a second sealing bar.

32. The method according to claim 31, further comprising receiving a web between the first sealing bar and the second sealing bar.

33. The method according to claim 32, further comprising sealing the web over an entire surface of the sealing bar with a constant pressure.

34. The method according to claim 30, further comprising compensating for tilting and/or manufacturing tolerances of the sealing bars with the compressible, heat conducting material.

35. The method according to claim 30, further comprising provinding an elastic metal meshwork for the material.