Apparatus and method for producing containers from paper material or paper-like material, and container

Abstract

An apparatus for producing containers from paper or paper-like material. The container has a lateral surface made of a wound sheet-like segment, of which segment edges arranged on longitudinal sides overlap and form a region of overlap, and a pan-like termination element. The lateral surface and the termination element are connected to one another in an essentially liquid-tight manner by a skirt, and at least one pressing ram is provided for pressing and sealing the skirt, the pressing ram subjecting the skirt to essentially radially directed pressure. The pressing ram has a radially projecting protrusion in a portion provided for the purpose of acting on a boundary portion of the region of overlap of the lateral surface of the skirt.

Claims

1. An apparatus for producing a container of sheet material, the container including a sheet segment wound about a longitudinal axis of the container to form a lateral wall of the container having segment edges disposed along opposite longitudinally extending sides of the sheet segment in overlapping relation with one another to form an overlap region of the container, and a pan-shaped termination element connected to the lateral wall in a liquid-tight manner by a skirt, the segment edges adjacent one end of the container each forming part of the skirt, one of the segment edges at the skirt being an inner segment edge located inwardly from and covered by the other segment edge at the skirt, the other segment edge being an outer segment edge, the outer segment edge being disposed radially outwardly from the inner segment edge to form a step on the skirt which forms part of a boundary portion of the overlap region of the container, the apparatus comprising at least one pressing ram disposed and configured to press and seal the skirt of the container, the pressing ram having first and second spaced-apart terminal edges and a pressing surface extending between and interconnecting the first and second terminal edges, the pressing surface being disposed to apply radially-directed pressure to the skirt of the container, the pressing surface having a single protrusion projecting radially outwardly beyond an entire remaining portion of the pressing surface disposed between the first and second terminal edges of the pressing ram such that the protrusion applies a pressure to the boundary portion of the overlap region of the container which is greater than pressure applied to the skirt by the entire remaining portion of the pressing surface.

2. The apparatus according to claim 1, wherein the pressing ram is oriented on a radially inner side of the skirt.

3. The apparatus according to claim 2, wherein the protrusion has a radially oriented outer surface having a convex curvature.

4. The apparatus according to claim 1, wherein the protrusion projects radially beyond the entire remaining portion of the pressing surface by an amount between 0.5 and 1.5 times a thickness of the sheet segment forming the lateral wall of the container.

5. The apparatus according to claim 1, wherein the protrusion projects radially beyond the entire remaining portion of the pressing surface by an amount substantially equal to a thickness of the sheet segment forming the lateral wall of the container.

6. The apparatus according to claim 1, wherein the protrusion has a width extending in a circumferential direction of the pressing surface by an amount between 0.25 and 0.75 times a width of the overlap region extending along a circumferential direction of the container.

7. The apparatus according to claim 1, wherein the protrusion has a width extending in a circumferential direction of the pressing surface by an amount of 0.5 times a width of the overlap region extending along a circumferential direction of the container.

8. The apparatus according to claim 1, wherein the protrusion is disposed circumferentially relative to the overlap region so as to apply pressure to only one of the segment edges in the overlap region at the skirt.

9. The apparatus according to claim 8, wherein the protrusion is disposed symmetrically relative to a periphery of the overlap region.

10. The apparatus according to claim 8, wherein the protrusion is disposed symmetrically relative to the one segment edge, the one segment edge butting against an outer side of the termination element.

11. The apparatus according to claim 1, wherein the protrusion is disposed circumferentially relative to the overlap region to apply pressure to only the inner segment edge, the inner segment edge butting against an outer surface of the termination element.

12. The apparatus according to claim 1, further including a counterpart disposed opposite the pressing ram and the skirt is disposed between the pressing ram and the counterpart, the counterpart comprising a depression disposed to accommodate the overlap region at the skirt.

13. The apparatus according to claim 12, wherein a width of the depression in a circumferential direction of the pressing surface is 0.5 to 1.5 times a width of the overlap region.

14. The apparatus according to claim 12, wherein a depth of the depression is 0.75 to 1.25 times a thickness of the sheet segment.

15. The apparatus according to claim 12, wherein a depth of the depression is substantially equal to a thickness of the sheet segment.

16. An apparatus for producing a container of sheet material, the container including a sheet segment wound about a longitudinal axis of the container to form a lateral wall of the container having segment edges disposed along opposite longitudinally extending sides of the sheet segment in overlapping relation with one another to form an overlap region of the container, and a pan-shaped termination element connected to the lateral wall in a liquid-tight manner by a skirt, the segment edges adjacent one end of the container each forming part of the skirt, one of the segment edges at the skirt being an inner segment edge located inwardly from and covered by the other segment edge at the skirt, the other segment edge being an outer segment edge, the outer segment edge being disposed radially outwardly from the inner segment edge to form a step on the skirt, the apparatus comprising at least one pressing ram disposed and configured to press and seal the skirt of the container, the pressing ram comprising first and second spaced-apart terminal edges and a pressing surface extending between and interconnecting the first and second terminal edges, the pressing surface being disposed to apply radially-directed pressure to the skirt of the container, the pressing surface including a single protrusion projecting radially outwardly beyond an entire remaining portion of the pressing surface disposed between the first and second terminal edges of the pressing ram such that the protrusion applies a pressure to the step of the skirt of the container which is greater than pressure applied to the skirt by the entire remaining portion of the pressing surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention can be gathered from the claims and from the following description of preferred embodiments of the invention in conjunction with the drawings. Individual features of the different embodiments illustrated can be combined with one another in any desired manner here without departing from the framework of the invention. In the drawings:

(2) FIG. 1 shows a side view of a cup according to the invention,

(3) FIG. 1a shows a partial sectional view taken along section plane B-B in FIG. 1,

(4) FIG. 2 shows a plan view of a first embodiment of a sheet-like segment for forming a lateral surface by winding action,

(5) FIG. 3 shows a second embodiment of a sheet-like segment for forming a lateral surface by winding action,

(6) FIG. 4 shows a partial view taken along section plane A-A in FIG. 1 with a pressing ram according to the prior art prior to the skirt being subjected to pressing action,

(7) FIG. 5 shows a partial view taken along section plane A-A from FIG. 1 with a pressing ram according to the invention prior to the skirt being subjected to pressing action,

(8) FIG. 5a shows a partial view of the pressing ram from FIG. 5, as seen obliquely from above,

(9) FIG. 5b shows a partial view of the pressing ram from FIG. 5 with terminal edges,

(10) FIG. 6 shows the sectional view from FIG. 5 once the skirt has been subjected to pressing action, and therefore in the state in which the skirt is positioned on the completed cup,

(11) FIG. 7 shows the sectional view from FIG. 6, dashed lines depicting a counterpart which butts against the outer side of the skirt,

(12) FIG. 8 shows the sectional view from FIG. 6, depicting a counterpart according to a further embodiment of the invention, and

(13) FIG. 9 shows a sectional view of a further embodiment of the container, with a section plane positioned along section plane A-A in FIG. 1.

DETAILED DESCRIPTION

(14) The illustration of FIG. 1 shows a side view of a container according to the invention, which in this case is designed in the form of a cup 10. The cup 10 has a frustoconical lateral surface 12, which is provided with a so-called rolled rim 14 on its upper periphery. The lateral surface 12 is formed by virtue of a sheet-like segment being wound, as is illustrated for example in FIG. 2 and FIG. 3. The longitudinal edges of this segment are positioned one above the other during the winding operation to form a region of overlap 16. Following the winding operation, the lateral surface 12 has a frustoconical shape.

(15) At its lower end, the cup 10 is provided with a termination element in the form of a base 18. The base 18 is of approximately pan-like configuration. The base 18 is formed from a for example disc-like paper segment, of which the peripheries are folded downwards through 90°, or somewhat more than 90°, and thus form a base collar 24 which projects approximately vertically downwards from a base plate 22, see FIG. 1a.

(16) The lower end of the lateral surface 12 is folded over through 180° around said collar 24 of the base 18. The base collar 24 and the lateral surface 12, which is folded over around the base collar 24, are then first of all heated up by means of hot air and are subsequently pressed together. The paper material of the base 18 and of the lateral surface 12 is provided at least on one side with a plastic coating, for example polyethylene. The thermoplastic coating is heated and, when the lateral surface 12 and base 18 are subjected to pressing action, the lateral surface 12 and base 18 are then sealed to one another in the region of the so-called skirt 20. This takes place in that the heated polyethylene coatings, or coatings made of some other suitable thermoplastic material, are fused together and thus connect the lateral surface 12 and the base 18 to one another in an essentially liquid-tight manner in the region of the base collar 24, or more specifically in the region of the skirt 20.

(17) FIG. 1a shows a partial sectional view taken along section plane B-B from FIG. 1. The section plane B-B is positioned here in the region of overlap 16, that is to say in which the lateral surface 12 comprises two material layers located one upon the other. It can clearly be seen that the base 18 has the baseplate 22 and the base collar 24, which projects approximately vertically downwards from the baseplate 22. The lower end of the lateral surface 12 has been folded around the base collar 24. In the region of the overlap 16, two material layers of the sheet-like segment, from which the lateral surface 12 is formed, are located one above the other both on the inner side and on the outer side of the base collar 24.

(18) FIG. 2 shows a plan view of a first embodiment of a sheet-like segment 26 for a cup 10. The segment 26 is wound onto a conical or frustoconical mandrel to give the frustoconical lateral surface 12. The segment 26 has a first side edge 28 and a second side edge 30. The segment 26 is wound to form an overlap, and therefore the first side edge 28 then passes into the position 28′, which is depicted by dashed lines in FIG. 2. At its lower end in FIG. 2, the side edge 30 merges into a bevel 32. The bevel 32 serves to space apart circumferentially from one another the part of the segment edge resting on the inner side of the base collar 24 and the part resting on the outer side of the base collar 24. The lateral surface 26 is folded over around the lower end of the base collar 24 here approximately in the region of the dashed line 34.

(19) The illustration of FIG. 3 shows a further embodiment of a segment 36 for a cup according to the invention. A first side edge 38 here has a bevel 40 at its upper end, and a second side edge 42 is provided with a recessed corner 44 at its lower end. The recessed corner 44 serves to space apart circumferentially from one another, when the lower end of the lateral surface is being folded over, the part of the segment edge resting on the inner side of the base collar 24 and the part resting on the outer side of the base collar 24. Similarly, the bevelled end 40 of the first side edge 38 also provides for the rolled rim 14 to be readily formed in the region of overlap.

(20) Instead of a rolled rim 14 being formed, it is also possible for the upper end of the lateral surface 12 to be folded over around a collar of a lid. This is done in the case of containers according to the invention which are designed in the form of cans. A lid would then be inserted into the lateral surface in the same way as the base 18, but precisely the other way up, in which case the lid collar then projects upwards from a lid plate and the upper end of the lateral surface would then be folded through 180° around said lid collar, and the lid collar and the upper folded-over end of the lateral surface would then be pressed and sealed to form a skirt.

(21) The illustration of FIG. 4 shows a partial view taken along section plane A-A in FIG. 1 prior to the skirt 20 being subjected to pressing action. The section plane A-A is illustrated in the region of overlap 16. The lateral surface 12, see also FIG. 1a, has had its lower end folded around the end of the base collar 24. The second segment edge 30 rests on an outer side of the base collar 24 and then runs by way of the bevel 32, not visible in FIG. 4, circumferentially to the right. On the inner side, the second segment edge 30, on account of the bevel 32, then butts against the inner side of the base collar 24 in a circumferentially spaced-apart state from the other part of the second segment edge 30.

(22) The first segment edge 28, on the outer side of the base collar 24, is spaced apart radially from the base collar 24, and it is also the case on the inner side of the base collar 24 that the first segment edge 28 is spaced apart from the base collar 24. Both on the inner side and the outer side of the base collar 24, that region of the segment which adjoins the first segment edge 28 has a step-like region 46, 48. This region 46 on the outer side of the base collar 24 and also the region 48 on the inner side of the base collar 24 are each arranged in the region of the second segment edge 30 and also belong to the region of overlap. The region of overlap 16 terminates in FIG. 4, on the one hand, at the first segment edge 28 and, on the other hand, at the second segment edge 30. However, a boundary portion of the region of overlap includes the step-like region 46 and the cavity 50 in front of the second segment edge 30, that is to say in other words the boundary portion ends at the point or the line at which the step-like region 46 terminates and the segment rests again on the outer side of the base collar 24.

(23) It can clearly be seen in the illustration of FIG. 4 that, in the step-like region 46, there is the cavity 50 located in front of the second segment edge 30. This cavity 50 has an approximately triangular cross section and is produced by the step-like region 46.

(24) FIG. 4 shows the state of the skirt 20 in the region of the overlap 16 prior to being pressed and sealed. It should be stated here that, prior to the pressing operation, the cavity 50 is in connection with the interior of the cup 10, since the second segment edge 30 extends into the interior of the cup 10. During the pressing operation, the attempt is made either to push this cavity 50 together or to fill it completely with sealing material, that is to say the molten PE coating of the material of the lateral surface 12 and/or of the base 18. If this does not succeed, then the cavity 50 constitutes a potential leakage point, via which liquid can then pass out of the interior of the cup 10 into the region of the skirt 20.

(25) On the inner side of the base collar 24, there is likewise an approximately triangular cavity 52 located in front of the inner segment edge 30, 32. This cavity is less critical since it is located on the inner side of the skirt 20 and, in the pressed and sealed state of the skirt 20, consequently is not in connection with the interior of the cup 10. In the non-pressed state of FIG. 4, however, the cavities 50, 52 merge into one another since they are located in front of the inner segment edge 30, 32 which has been folded around the lower periphery of the base collar 24, cf. also FIG. 1a.

(26) FIG. 4 shows a conventional pressing ram 54 on the radially inner side of the skirt 20. This conventional pressing ram 54 is moved radially outwards, that is to say downwards in FIG. 4, in order to press and to seal the skirt 20. It is usual to provide a plurality of circle-segment-shaped pressing rams 54 which, arranged on the inner side of the skirt 20, are then moved radially outwards. However, it is difficult for the skirt 20 to be formed in a liquid-tight manner.

(27) FIG. 5 shows an illustration of the lateral surface 12 and of the base collar 24, in the region of the skirt 20, which corresponds to the illustration from FIG. 4. The lateral surface 12 and the base collar 24 will therefore not be explained anew.

(28) Instead of the pressing ram 54, however, part of a pressing ram 56 according to the invention is illustrated here. This pressing ram 56 has a radially outwardly projecting protrusion 58, which projects radially outwards in relation to the rest of the pressing surface 60 of the pressing ram 56. Further, as shown in FIG. 5b, the pressing ram 56 has spaced-apart terminal edges 56a and 56b, between which the pressing surface 60 extends.

(29) This protrusion 58 is arranged, and dimensioned, such that it applies an increased pressure to the overlap 16 in its boundary portion, namely in the region of the cavity 50 in front of the second segment edge 30 on the outer side of the base collar 24. This makes it possible to ensure, once the skirt 20 has been pressed and sealed, that the cavity 50 is significantly smaller than in the case of conventional cups and is always completely filled with sealing material.

(30) The illustration of FIG. 6 shows the state once the skirt has been subjected to pressing action. As has already been explained, the skirt 20 is heated up, for example subjected to the action of hot air from the underside, in the not-yet-pressed state of FIG. 5. The pressing ram 56 then subjects the skirt to a radially outwardly directed pressure, which is symbolized in FIG. 6 by means of the arrow 62. It should be stated here that the pressing ram 56, or a plurality of pressing rams 56, applies, or apply, a radially outwardly directed pressure over the entire circumference of the skirt. On account of the protrusion 58 of the pressing ram 56, which projects radially outwards beyond the rest of the pressing surface 60 of the pressing ram 56, the pressure in the region of the protrusion 58, and thus in the region of the cavity 50 and in the boundary portion of the region of overlap, is nevertheless greater than in the region of the rest of the pressing surface 60. For clarification purposes, the arrow 62 has depicted alongside it in the circumferential direction somewhat shorter arrows 64, which are intended to symbolize the reduced pressure in the region of the rest of the pressing surface 60 of the pressing ram 56.

(31) FIG. 6 shows the already definitively pressed and sealed state of the skirt 20. It can clearly be seen that the cavity 50 in front of the inner segment edge 30 on the outer side of the base collar 24 is completely filled with sealing material, this being illustrated by black ink in FIG. 6. In contrast, on the inner side of the base collar 24, the cavity 52 in front of the segment edge 30, in the region of the bevel 32, is not completely filled with sealing material, since here only the lower pressure has been applied radially outwards. As has already been mentioned, however, this cavity 52 is not critical as far as the sealing of the cup is concerned.

(32) On account of the increased pressure in the region of the protrusion 58, the skirt 20 has a depression 66 on its inner side. The dimensions of the depression 66 correspond approximately to the dimensions of the protrusion 58.

(33) The pressing ram 56 and thus the pressing surface 60 usually have a height which corresponds to the height of the skirt on the inner side of the skirt 20. In order to increase the pressure, the pressing surface 60 may also be designed in the form of one or more strips, see FIG. 5a. These strips can then each have a protrusion 58, which projects in the radial direction and performs the function of the protrusion 58 of the pressing ram 56 in FIG. 6, as is illustrated in FIG. 5a. If appropriate, it may also be sufficient then for just one of the strips to be provided with a protrusion.

(34) The illustration of FIG. 7 shows the cup in the region of the skirt 20 with the pressing ram 56 in the already pressed state of FIG. 6. The pressing ram 56 and skirt 20 will therefore not be explained anew.

(35) On the outer side of the skirt 20, a counterpart 70 is arranged opposite the pressing ram 56. The counterpart 70 has a concave shaping, wherein the radius of this concave shaping corresponds approximately to the outer radius of the skirt 20. When the skirt 20 is subjected to pressing action, this counterpart 70 absorbs the pressure applied by the pressing ram 56.

(36) The illustration of FIG. 8 shows the arrangement of FIG. 7, the counterpart 70 being replaced by a counterpart 72 which, on its side which is directed towards the skirt 20, has a depression 74. The depression 74 is approximately as wide as the region of overlap 16 on the outer side of the skirt 20, said outer side being located at the bottom in FIG. 8. As a result of the depression 74, the region of overlap 16 can be accommodated in the counterpart 72 and the increased pressure in the region of the arrow 62 can be concentrated on the region of the cavity 50.

(37) The depression 74 has rounded side edges, and this therefore avoids damage to the outer side of the skirt 20. The depression 74 has a depth which corresponds approximately to the material thickness of the segment 26 for producing the outer lateral surface 12. This can achieve reliable pressing and sealing in the region of the cavity 50 without there being any risk of the material of the lateral surface 12 being damaged by excessive pressure in the region of the overlap 16.

(38) The illustration of FIG. 9 shows a further embodiment of a container according to the invention. The illustration of FIG. 9 here constitutes a partial sectional view corresponding to FIG. 4, the section plane having been positioned in this through the skirt 20 in the same way as section plane A-A in FIG. 1. The pressing ram 56 has already been explained and has the protrusion 58.

(39) In contrast to the lateral surface 12 from FIG. 4, the lateral surface 74 from FIG. 9 is formed from a segment of which the second segment edge 30 is provided with a sealing strip 76. The sealing strip 76 consists of a sealable thermoplastic, for example of polyethylene. The sealing strip 76 is folded around the second segment edge 30, and therefore the sealing strip thus extends some way along the region of overlap 16, on either side of the segment edge 30. Providing the sealing strip 76 means that, when the skirt 20 is subjected to pressing action, there is additional thermoplastic material available in order for the cavity 50 in front of the inner segment edge 30, which rests on the outer side of the base collar 24, to be completely filled with sealing material, that is to say in this case polyethylene. The provision of the sealing strip 76 thus makes it possible to provide for even more reliable sealing of the skirt 20 in relation to the interior of the container according to the invention.

(40) Since that part of the second segment edge 30 which rests on the outer side of the base collar 24 extends from the skirt 20 into the interior of the container, the sealing strip 76 can prevent the open, cut edge along the segment edge 30 from coming into contact with liquid within the container. The sealing strip 76 is therefore used preferably in cans made of paper material, or paper-like material, which are intended to be filled, as cups, with liquid over a relatively long period of time. In the case of a can, rather than being connected just to the base collar 24 by means of the skirt 20, the lateral surface 74, as has already been explained in the introduction, would likewise be connected in a liquid-tight manner to a pan-like lid by means of a further skirt. It is also the case in the region of the skirt which connects the lateral surface 74 to the lid that the inner segment edge 30 is then provided with the sealing strip 76, in order also to achieve a particularly liquid-tight design of the skirt in the region of the lid.