Thermoform packaging machine and method
The present invention relates to a thermoform packaging machine as well as to a method for producing a skin pack, comprising the steps of preforming a skin film prior to a sealing station and subjecting it to a further forming step in the sealing station, so that the skin film can wrap around a product protruding far beyond a packaging trough.
1. A thermoform packaging machine comprising:
a bottom-film forming station including a number n of mold cavities for forming n troughs into a bottom film;
a top-film forming station including n evacuable first domes for forming n lids into a top skin film, wherein each first dome is enclosed by a clamping surface and has a first height, the first height defined by the maximum depth of a hollow in said first domes relative to the plane of the clamping surface, wherein the top-film forming station includes a first heating element to heat the top skin film to a temperature between 100° C. and 140° C.; and
a sealing station configured for sealing the n lids with the n troughs associated therewith, wherein the sealing station includes a sealing-tool upper part comprising n heatable and evacuable second domes having a second height, wherein the sealing station includes a second heating element to heat the top skin film to a temperature between 170° C. and 220° C.;
wherein the second domes are configured for allowing the top skin film to be brought into contact with the respective second dome from inside;
wherein the first height is at least 80% of the second height;
wherein n is larger than or equal to two.
2. The thermoform packaging machine according to claim 1 , wherein the second height is at least 60 mm.
3. The thermoform packaging machine according to claim 1 further comprising a top-film conveyor having conveying members disposed on both sides of the top skin film to advance the lids from the top-film forming station into the sealing station.
4. The thermoform packaging machine according to claim 1 , wherein the mold cavities have a cavity depth, and wherein the second height of the second domes in the sealing-tool upper part is at least five times as large as the cavity depth.
5. The thermoform packaging machine according to claim 1 ,
wherein the n mold cavities in the bottom-film forming station each have an opening length in a direction parallel to a production direction of the bottom film and an opening width in a direction transverse to the production direction of the bottom film;
wherein the n first domes in the top-film forming tool upper part each have a first opening length in a direction parallel to a production direction of the top film and a first opening width in a direction transverse to the production direction of the top film; and
wherein the first opening length and the first opening width of the first domes amounting each to a value between 80% and 95% of the opening length and opening width, respectively, of the mold cavity, so that the molded lids will have dimensions that are larger than those of a product to be packed, when they are supplied to the sealing station.
6. The thermoform packaging machine according to claim 1 , wherein said top skin film does not appreciably shrink upon application of heat.