Device and method of sealing packages

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;

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