Method for making a package in sheet material
Described herein is a method for making a package comprising at least one sheet of packaging material including at least one layer of paper, which is shaped so as to present a hollow portion surrounded by a perimetral portion. The hollow portion of the shaped sheet has a ratio between depth and width higher than 0.39, preferably between 1:1.8 and 1:2.5.
1 . A method for making a package in sheet material, the method comprising the steps of:
providing a sheet ( 100 ) of packaging material, comprising at least one layer of paper;
providing a mould ( 20 ) comprising a mould cavity ( 22 ) delimited by a forming surface ( 22 A) and having a supporting surface ( 24 ) that surrounds the mould cavity ( 22 ),
wherein the forming surface ( 22 A) has a top edge ( 22 B) extending along a pre-set closed path (K);
positioning the sheet ( 100 ) over the mould cavity ( 22 ) and resting on the supporting surface ( 24 );
driving a withholding member ( 26 ) to press against the supporting surface ( 24 ) a portion of the sheet ( 100 ) resting on the supporting surface ( 24 ) itself;
while the withholding member ( 26 ) presses the sheet ( 100 ) against the supporting surface ( 24 ), driving a forming member ( 28 ) provided with an operating surface ( 28 A) having a shape complementary to that of the forming surface ( 22 A) of the mould cavity ( 22 ) to push the sheet ( 100 ) into the mould cavity ( 22 ) and bring the sheet ( 100 ) into contact with the forming surface ( 22 A) of the mould cavity ( 20 ), at the end of the action of the forming member on the sheet there being formed a hollow portion ( 102 ) surrounded by a perimetral portion ( 104 ) that extends along a predefined profile (K 1 ) corresponding to the pre-set path (K),
wherein the forming surface ( 22 A) of the mould cavity ( 22 ) and the operating surface ( 28 A) of the forming member ( 28 ) are configured for providing a region of the hollow portion ( 102 ), extending along the predefined profile (K 1 ), that defines, with the perimetral portion ( 104 ), an angle (q) equal to or greater than 90°; and
operating a pressure member ( 32 ) to press the perimetral portion ( 104 ) of the first sheet ( 100 ) against a contrast surface ( 34 ) so as to subject the perimetral portion ( 104 ) of the first sheet ( 100 ) to an action of stretching along a path parallel to the predefined profile (K 1 ), wherein provided in the pressure member ( 32 ) or in the contrast surface ( 34 ) is an annular groove ( 34 B) that extends in a direction parallel to the predefined profile (K 1 ) of the perimetral portion ( 104 ) pressed between the pressure member ( 32 ) and the contrast surface ( 34 ), and provided on the contrast surface ( 34 ) or on the pressure member ( 32 ) is an annular relief ( 32 B) having a complementary shape that is to penetrate into the annular groove ( 34 B), the method comprising, via said annular relief ( 32 B), pushing the perimetral portion ( 104 ) of the sheet ( 100 ) into said annular groove ( 34 B) so as to exert an action of stretching of the perimetral portion ( 104 ) in a direction transverse to the predefined profile (K 1 ).
2 . The method according to claim 1 , wherein the pressure exerted by the withholding member ( 26 ) is such that, following upon the action of the forming member ( 28 ), the sheet ( 100 ) moves into the mould cavity ( 22 ) and comes to cover the forming surface ( 22 A) as a result of two combined actions, which are i) sliding of the sheet ( 100 ) with respect to the withholding member ( 26 ), and ii) deformation by stretching of the sheet ( 100 ), and wherein obtained on the perimetral portion ( 104 ) of the formed sheet are a series of folds ( 108 ) identified by respective lines of folding of the sheet that are oriented in a direction transverse to the predefined profile (K 1 ), and wherein also obtained on the hollow portion ( 102 ) are a series of folds identified by respective lines of folding of the sheet oriented in a direction transverse to the predefined profile (K 1 ), limitedly to a region along the predefined profile (K 1 ), in the proximity of the perimetral portion ( 104 ).
3 . The method according to claim 1 , wherein the forming surface ( 22 A) and/or the supporting surface ( 24 ) of the mould ( 20 ) are heated to a pre-set temperature.
4 . The method according to claim 3 , wherein the pre-set temperature is between 60° C. and 100° C.
5 . The method according to claim 1 , wherein the forming member ( 28 ) is heated to a pre-set temperature.
6 . The method according to claim 5 , wherein the pre-set temperature is between 20° C. and 60° C.
7 . The method according to claim 1 , which further includes driving the forming member ( 28 ) to press the sheet ( 100 ) against the forming surface ( 22 A) by exerting a total force higher than 3000 N.
8 . The method according to claim 7 , wherein the total force is at least equal to 7000 N.
9 . The method according to claim 1 , wherein the withholding member ( 26 ) is heated to a pre-set temperature.
10 . The method according to claim 9 , wherein the pre-set temperature is between 20° C. and 60° C.
11 . The method according to claim 1 , wherein said pressure member ( 32 ) operates after the forming member ( 28 ).
12 . The method according to claim 1 , wherein provided in the supporting surface ( 24 ) of the mould ( 20 ) or in the withholding member ( 26 ) are a series of grooves ( 26 B) distributed around the mould cavity ( 22 ) and oriented in directions transverse to the pre-set profile (K), and provided on the withholding member ( 26 ) or on the supporting surface ( 24 ) are a series of reliefs ( 26 B) complementary to the grooves ( 24 B), the method comprising pressing via the reliefs ( 26 B) the sheet ( 100 ) into the grooves ( 24 B) so as to exert an action of stretching of the perimetral portion ( 104 ) along a path parallel to the predefined profile (K).
13 . The method according to claim 1 , further comprising:
inserting at least one product into the hollow portion ( 102 );
providing a second sheet ( 200 ) of packaging material;
heat-sealing the second sheet ( 200 ) to the first sheet ( 100 ) that has been formed and contains the at least one product in the hollow portion ( 102 ).
14 . The method according to claim 13 ,
wherein heat-sealing the second sheet ( 200 ) to the first sheet ( 100 ) includes:
providing a supporting member ( 42 ) and positioning the first sheet ( 100 ) in a condition where the perimetral portion ( 104 ) rests on the supporting member ( 42 );
operating a heat-sealing member ( 44 ) to press a corresponding portion ( 204 ) of the second sheet ( 200 ) against the perimetral portion ( 104 ) of the first sheet and heating the corresponding portion ( 204 ) of the second sheet ( 200 ) and/or the perimetral portion ( 104 ) of the first sheet ( 100 ) to bring about fixing between the two portions.
15 . The method according to claim 14 , wherein said pressure member is said heat-sealing member ( 44 ) and said contrast surface is defined by said supporting member ( 42 ).
16 . The method according to claim 15 , wherein the supporting member ( 42 ) is compliant and wherein the heat-sealing member ( 44 ) presses the second sheet and the perimetral portion of the sheet against the compliant supporting member so that, where there is a variation of thickness on the perimetral portion ( 104 ) of the sheet created by the presence of folds ( 108 ), an action of stretching of the perimetral portion ( 104 ) is brought about along a path parallel to the predefined profile (K 1 ) and/or in a direction transverse thereto.
17 . The method according to claim 16 , wherein the supporting member ( 42 ) is made of compliant material.
18 . The method according to claim 17 , wherein the compliant material has a hardness of not less than 60 SH.
19 . The method according to claim 1 , wherein the first sheet ( 100 ) or both the first sheet ( 100 ) and the second sheet ( 200 ) comprises/comprise a layer of extensible paper.
20 . The method according to claim 1 , wherein the forming surface ( 22 A) of the mould cavity ( 22 ) and the operating surface ( 28 A) of the forming member ( 28 ) are configured for providing a region of the hollow portion ( 102 ), extending along the predefined profile (K 1 ), that defines, with the perimetral portion ( 104 ), an angle (q) equal to or greater than 90°.
21 . The method according to claim 20 , wherein the angle (q) is comprised between 90° and 95°.
22 . The method according to claim 1 , wherein providing a sheet ( 100 ) includes providing a sheet having a total useful area for forming a given number of hollow portions surrounded by corresponding perimetral portions, and wherein the sheet ( 100 ) has a series of cuts configured to identify a number of distinct regions of the sheet, equal to the given number, on which to form respective hollow portions surrounded by perimetral portions and which are connected to the remaining parts of the sheet only by narrow connection portions positioned around the individual regions.
23 . A package obtained via a method according to claim 1 , wherein the hollow portion ( 102 ) of the sheet ( 100 ) formed has a ratio between depth and width higher than 0.39.
24 . Package according to claim 23 , wherein the folds of the sheet present on the hollow portion ( 102 ) project from the outer surface of the hollow portion ( 102 ) by a stretch (H) of less than or equal to 0.2 mm.
25 . The package according to claim 23 , wherein the folds of the sheet present on the perimetral portion ( 104 ) project from the plane of the perimetral portion ( 104 ) by a stretch of less than or equal to 0.2 mm.
26 . The package according to claim 23 , wherein the perimetral portion ( 104 ) defines an angle (q) with the region of the hollow portion ( 102 ) extending along the predefined profile (K 1 ) that is equal to or greater than 90°.
27 . The package according to claim 26 , wherein the angle (q) is comprised between 90° and 95°.
28 . A package obtained via a method according to claim 23 , wherein the ratio between depth and width is between 1:1.8 and 1:2.5.
29 . The method according to claim 1 , wherein the angle (q) is comprised between 90° and 180°.