Thermoform packaging machine and method

Abstract

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.

Claims

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.

Description

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) In the following, an advantageous embodiment of the present invention will be explained in more detail making reference to a drawing. The individual figures show:

(2) FIG. 1 is a schematic side view of a thermoform packaging machine according to one embodiment of the present invention;

(3) FIG. 2A is a schematic view of a bottom-film forming station according to one embodiment of the present invention;

(4) FIG. 2B is a top view of a forming-tool lower part according to one embodiment of the present invention;

(5) FIG. 3A is a schematic side view of a top-film forming station according to one embodiment of the present invention;

(6) FIG. 3B is a top view of a top-film forming tool upper part according to one embodiment of the present invention;

(7) FIG. 4A is a schematic side view of a sealing station at a closed position according to one embodiment of the present invention;

(8) FIG. 4B is a view from below a sealing-tool upper part according to one embodiment of the present invention;

(9) FIG. 5 is a schematic side view of the sealing station according to FIG. 4A after application of the skin film in the dome; and

(10) FIG. 6 is a schematic side view of the sealing station according to FIG. 4A after application of the skin film to the product and the trough.

(11) Like components are provided with like reference numerals throughout the figures.

DETAILED DESCRIPTION OF THE INVENTION

(12) The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. For purposes of clarity in illustrating the characteristics of the present invention, proportional relationships of the elements have not necessarily been maintained in the drawing figures.

(13) The following detailed description of the invention references specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The present invention is defined by the appended claims and the description is, therefore, not to be taken in a limiting sense and shall not limit the scope of equivalents to which such claims are entitled.

(14) FIG. 1 shows a thermoform packaging machine 1 according to one embodiment of the present invention in a schematic side view, with a production direction R. In the production direction R, a plurality of work stations, such as a bottom-film forming station 2, a top-film forming station 3, a sealing station 4, a cross cutting station 5 and a longitudinal cutting station 6, can be provided in succession. In the following, the mode of operation of the thermoform packaging machine 1 according to one embodiment of the present invention will be explained in more detail.

(15) A bottom film/foil 7, configured, for example, as a hard film made of plastic, can be unwound from a first film roll 8 and grasped on both sides thereof by a clamp chain, which is not shown in detail, and conveyed into the bottom-film forming station 2. In the bottom-film forming station 2, the bottom film 7 may be heated and two troughs 9, which, relative to the drawing plane, are shown as arranged one behind the other and thus in two lanes (i.e., side by side when seen in the production direction R), are formed into the bottom film 7. Along an infeed line 10, which is arranged between the bottom-film forming station 2 and the sealing station 4, products 50 are placed into the troughs 9, the products 50 having a height of more than 50 mm.

(16) A top film 11, configured as a skin film, can be unwound from a second film roll 12 and conveyed by means of a top-film conveying unit 13, which may be arranged on both sides, into the top-film forming station 3, where it can be heated to a first temperature of approximately 120 C., for example, so as to form therein two lids 14, which, relative to the drawing plane, are arranged one behind the other and thus in two lanes. During the conveying movement of the lids 14 by means of the top-film conveying unit 13 towards the sealing station 4, the lids 14 are moved closer to the troughs 9 and the bottom film 7 and, in the course of this movement, they may be pulled over the products 50 without any pressure being applied to the products 50, since the lids 14 are formed such that their dimensions are larger than the dimensions of the products 50.

(17) The top-film conveying unit 13, for example, in the form of two clamp chains 13 arranged on both sides of the top film 11, may fulfill here, on the one hand, the function of precisely positioning the lids 14 above and onto the products 50 and may be moved in synchronism with the clamp chain for the bottom film 7. On the other hand, the top-film conveying unit 13 may fulfill the function of laterally holding the skin film 11 and the lids 14, respectively, during the conveying movement and in the interior of the sealing tool 4. A distortion of and wrinkle formation in the skin film 11, which may be caused by possibly occurring transverse stresses within the skin film 11, can be prevented in this way.

(18) In the sealing station 4, the lids 14 may be forming, after the formation of a chamber 15 through a sealing-tool upper part 16 and a sealing-tool lower part 17, by means of a vacuum generated between the lids 14 and the domes 18, which are shown in more detail in FIG. 3A, onto the inner wall of the domes 18 in the sealing-tool upper part 16, and heated to a skin temperature of approximately 180 C., for example, so that they will have an adequate elasticity for the subsequent skinning process. At the same time, a further vacuum is applied in the interior of the package 19, viz. between the lids 14 and the troughs 9. Through this vacuum and by venting the sealing-tool upper part 16 to ambient pressure, the elastic lid 14 will fit snugly to the product 50 as well as to the trough 9, the skin film 11, i.e., the lids 14, and the trough 9 establishing a large-area, air-tight sealing during this skinning process. This package 19 can be referred to as skin pack, since the product 50 placed on or rather in the trough 9 is sealed in an air-tight manner onto the bottom film 7 or trough 9 by means of a film 11 which wraps tightly around the product 50, similar to a second skin.

(19) While moving on in the production direction R, the packages 19 conveyed side by side on two lanes may be separated from one another by means of the cross cutting station 5 and the longitudinal cutting station 6 and conveyed out of the thermoform packaging machine 1 via a conveyor belt 20.

(20) In FIG. 2A, the bottom-film forming station 2 is shown in more detail. It can comprise a forming-tool upper part 21 located above the bottom film 7 and may be configured as a heating plate for heating the bottom film 7, prior to the forming step, to a temperature that is required for such forming. A forming-tool lower part 22 movable in the direction of the arrow and arranged below the bottom film 7 comprises two mold cavities 23 in which the heated bottom film 7 can be formed into troughs 9 by means of a vacuum from below and/or pressurized air from above. The trough 9 and the mold cavity 23 have a trough/cavity depth T oriented perpendicular to the bottom film 7. In addition, the trough 9 itself has, after the forming process, a trough edge 25.

(21) FIG. 2B shows the forming-tool lower part 22 with the two mold cavities 23 in a top view. The two mold cavities 23 may each have an upwardly directed opening 24, each of the openings 24 having, in turn, an opening length L extending parallel to the conveying direction R and an opening width B extending transversely thereto.

(22) Referring to FIG. 3A, the top-film forming station 3 will be explained in more detail. The top-film forming station 3 can comprise a top-film forming tool lower part 26 configured as a heating plate and a top-film forming tool upper part 27 movable in the direction of the arrow and comprising two domes 28 and a clamping surface 29 for clamping the skin film 11 between the top-film forming tool lower part 26 and the top-film forming tool upper part 27. The domes 28 have a first height D1 defined by the maximum depth of a hollow 35 relative to the plane of the clamping surface 29 and an inner wall 30. When the top-film forming station 3 is at a closed operating position, the skin film 11 can be clamped between the top-film forming tool lower part 26 and the top-film forming tool upper part 27, heated by the top-film forming tool lower part 26 and drawn into the domes 28 by means of a vacuum. After opening of the top-film forming station 3, a lid 14 has been formed in the skin film 11.

(23) FIG. 3B shows, from below, a sectional view of the clamping surface 29 of the top-film forming tool upper part 27. The two domes 28 can each be provided with an opening 28a having, in turn, an opening length L1 extending parallel to the conveying direction R1 of the skin film and an opening width B1 extending transversely thereto. These dimensions correspond to a very large extent to the complementary dimensions of the lids 14, since shrinking effects may occur. The skin film 11 is conveyed via a top-film conveying unit 13 shown in FIG. 3A in the form of clamp chains 13 arranged on both sides.

(24) FIGS. 4A and 4B show the sealing station 4 in a condition in which the sealing-tool upper part 16 and the sealing-tool lower part 17 are closed, the products 50 being enclosed by the lids 14 and the troughs 9 and the lids 14 as well as the troughs 9 being circumferentially clamped in position between the sealing-tool upper part 16 and the sealing-tool lower part 17. In the defined chamber 15 the lids 14 may be sucked onto the inner wall 32 of the dome 18 of the sealing-tool upper part 16 through a vacuum V applied to the sealing-tool upper part 16, and fit then to the inner wall 32. The sealing-tool upper part 16 can comprise a heating 33 by means of which the lids 14 are heated to the skin temperature.

(25) Analogously to FIG. 3B, the sealing-tool upper part 16 may comprise, like the top-film forming tool upper part 27, two domes 18 having an opening length L2 extending parallel to the production direction R and an opening width B2 extending transversely thereto as well as a second height D2. This can be seen in FIG. 4B, in which the domes 18 are shown from below. Reference numeral 31 stands here for the opening 18 of each dome 18. Each of the three dimensions L2, B2 and D2 of the domes 18 of the sealing-tool upper part 16 exceeds the dimensions L1, B1 and D1 of the domes 28 of the top-film forming tool upper part 27 by approximately 5% to 20% in size. One of the reasons for this is that it can be advantageous to provide a distance A between two lids 14 following one another in the conveying direction R, so that the sealing-tool upper part 16 can be moved to its closed position, as shown in FIG. 4A, without a lid 14 located directly upstream of the sealing station 4 being excessively negatively influenced by radiation heat of the sealing-tool upper part 16, even though, at this position, the lid 14 has already been pulled over the product 50 to a very large extent.

(26) FIG. 5 shows the phase in which the lids 14 contact the domes 18 from inside and are heated by means of the heating 33 to a second temperature, i.e., the so-called skin temperature, whereas the space between the troughs 9 and the lids 14 is evacuated by means of a vacuum V.

(27) FIG. 6 shows the situation after venting of the sealing-tool upper part 16 and after the lids 14, i.e., the skin film 11, have/has been applied to the product 50 and to the trough 9.

(28) From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting.

(29) The constructions and methods described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms having and including and similar terms as used in the foregoing specification are used in the sense of optional or may include and not as required. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.