CN110775325B

CN110775325B - Method and apparatus for handling blanks made of packaging material

Info

Publication number: CN110775325B
Application number: CN201910663702.0A
Authority: CN
Inventors: F·奥伯舍尔普; B·罗斯勒
Original assignee: Focke and Co GmbH and Co KG
Current assignee: Focke and Co GmbH and Co KG
Priority date: 2018-07-25
Filing date: 2019-07-23
Publication date: 2023-04-18
Anticipated expiration: 2039-07-23
Also published as: EP3599088A3; DE102018005838A1; EP3599088A2; CN110775325A

Abstract

The invention relates to a method and a device for handling blanks (33, 36) made of packaging material, said blanks (33, 36) being provided with a camber (31), characterized in that the blanks (33, 36) are moved along a blank track (39) through a deformation station (34, 38), said camber (31) being produced during the movement of the blanks (33, 36) along the blank track (39) in the deformation station (34, 38).

Description

Method and apparatus for handling blanks made of packaging material

Technical Field

The present invention relates to a method for handling blanks made of packaging material.

The invention also relates to a corresponding device.

Background

Shoulder boxes for cigarettes (Kappenschachtel) are known in practice, which are provided with one or more arched walls. Typically in shoulder boxes such arches are provided on large area walls, such as the upper lid wall and/or the lower base wall. The lid wall is usually provided with a convex dome shape and/or the bottom wall with a concave dome shape. For example, in order to improve the stack formation of the packages, in particular for further processing in the packaging machine. The appearance of the package can also be improved in this way.

As is known, such arches are provided on the wall of a blank made of packaging material for a shoulder box by means of a punch which presses onto the blank. The punch is usually used here together with the die. In addition, sometimes heat and/or steam supply is also used. Typically, the blank is pressed into the die by a punch and held briefly to provide the dome shape.

A disadvantage of the known solutions for providing an arch in the wall of a blank made of packaging material is that the method is time-consuming, since the blank has to be left for a period of time in order to provide the arch (possibly under the additional action of heat and/or steam) by means of a punch and a die.

Disclosure of Invention

On this basis, the object on which the invention is based is to improve a method and a device of the type mentioned at the outset, in particular with regard to faster production and/or lower energy consumption. The invention should not be limited to applications relating to the production of shoulder boxes.

A method according to the invention for handling blanks made of packaging material for solving the stated task is characterized in that the blanks are provided with an arch and are moved along a blank path through a deformation station, the arch being created during the movement of the blanks along the blank path in the deformation station. According to the invention, the at least partially arched blank is conveyed in the deflection station after the deformation station along an at least partially curved transport path to maintain the curvature radius of the blank, the direction of curvature of the transport path corresponding to the direction of the arch of the blank.

It has been shown that this way of manufacturing works more quickly, since the blank does not need to be stationary in order to provide the camber. The supply of heat and/or steam can also be dispensed with, thus saving energy.

In a preferred embodiment of the invention, it is provided that, in order to provide the dome shape, the blank is guided around the curved surface of the pressure-rigid body, whereby bending stresses are induced in the blank which lead to permanent plastic deformation of the blank in the form of the dome shape.

One particular feature may be that the at least partially arched blank is conveyed in the deflection station after the deformation station along a curved transport path, the direction of curvature of which corresponds to the direction of the arch of the blank. Maintaining the bend radius of the blank has been shown to be a good way of supplying the blank to subsequent processing. This solution is particularly advantageous over the straight-line further transport of partially arched blanks, since this can lead to a reduction in the camber.

Preferably, the radius of the curved transport path at least partially corresponds to the radius of the at least partially arched blank. In this way it is ensured that the camber of the blank does not decrease or disappear.

In a preferred embodiment of the method, it can be provided that the curved transport paths intersect in such a way that the at least partially arched blank is transported after the deflection station essentially in the same transport direction as in the deformation station. In this way, the material flow can be maintained as a whole in the process.

In a preferred embodiment of the invention, it can be provided that the length of the transport path in the deflection station is greater than the length of the blank in the transport direction. In this way, the blank is prevented from colliding with itself.

Furthermore, it can be provided that the at least partially arched blank is transported in a curved transport path with a maintained direction of movement.

Preferably, the arched blanks are transported along a straight transport path after the deflection station.

One particular feature can be that the at least partially arched blank is guided during transport at least partially by the lateral guide in the region of the laterally opposite edges of the blank, in particular in the region of the edge of the blank oriented in the transport direction, in a curved transport path and/or in a linear transport path. This measure may help to suppress the disappearance of the dome.

Preferably, the at least partially arched blank is transported along the at least partially curved transport path and/or along the lateral guide in a stress-free manner without external forces acting on the blank which could damage the arch.

In a preferred embodiment of the method, it can be provided that the blank is provided with a two-dimensional curvature in the deformation station and that the three-dimensional curvature of the blank is then produced by folding the side walls of the blank.

Another method according to the invention, which can also be a development of the above-described solution, provides that the at least one first side wall is folded by an angle of >90 ° relative to the wall and is subsequently folded back such that this angle is ≦ 90 ° and that after this the at least one second side wall is folded by an angle of >90 ° relative to the wall.

The so-called "over-folding" of the side walls reduces the material-related return force of the blank and thus suppresses the risk of unfolding of the blank.

Preferably, this is done in that two first side walls are arranged on opposite sides of the wall and folded back together and two second side walls are arranged on the other opposite sides of the wall and folded together. In this way collision of adjacent first and second side walls is avoided. Most preferably the side walls are provided on different sides of the rectangular wall.

The device for handling blanks made of packaging material for solving the initially mentioned task or for carrying out the method is configured for providing the blanks with an arch shape and has a deformation station through which the blanks can be moved along a blank path, the deformation station being configured for imposing an arch shape on the blanks by plastic deformation during the movement of the blanks along the blank path, a deflection station being provided after the deformation station, the deflection station being configured for conveying the arched blanks along a curved transport path to maintain a bending radius of the blanks, the direction of curvature of the transport path corresponding at least partially to the direction of the arch shape of the blanks.

In a preferred embodiment of the invention, it is provided that at least two cooperating rollers are provided in the deformation station, which are positioned on different sides of the blank path and between which the (preferably unfolded) blank can be moved in such a way that bending stresses are generated in the blank for providing the arch on at least one wall of the blank.

In a preferred embodiment of the device, it can be provided that one of the rollers, i.e. the mold roller, has a pressure-elastic surface and the other roller, i.e. the mold roller, has a pressure-rigid surface.

Furthermore, it can be provided that the distance between the rollers is adjustable, preferably by supporting the forming rollers with a lever system, the pressing force between the rollers being adjustable to influence the apparent degree of arching of the blank.

In a preferred embodiment of the invention, it can be provided that the rollers can be moved away from one another.

Furthermore, it can be provided that a deflection station is provided after the deformation station, which deflection station is designed to convey the arched blanks along a curved transport path, the direction of curvature of which corresponds at least partially to the direction of the arch of the blanks.

The distance between the rollers and the position or adjustment of the end stops can be achieved mechanically, pneumatically or electrically. Furthermore, this may be integrated into the control system.

Another device according to the invention (which can also be a development of the above-described device) provides that the device comprises at least one mechanism for folding at least one first side wall by an angle of >90 ° relative to the wall, and that the device comprises at least one mechanism for subsequently folding back the at least one first side wall such that the angle is ≦ 90 °, and that the device comprises a mechanism for thereafter folding at least one second side wall by an angle of >90 ° relative to the wall.

Drawings

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The attached drawings are as follows:

figure 1 shows the structure of a shoulder box in a spatial view;

fig. 2 shows a closed shoulder box in a spatial view;

FIG. 3 shows a vertical cross-sectional view of the shoulder box along section line III-III in FIG. 2;

fig. 4 shows a schematic view of a manufacturing or corresponding apparatus of a shoulder box;

fig. 5 shows a device part in a side view corresponding to arrow V in fig. 4;

fig. 6 shows an enlarged detail of the apparatus in region VI of fig. 5;

fig. 7 shows an enlarged detail of the apparatus in region VII of fig. 6;

FIG. 8 shows an enlarged detail view of the apparatus in region VIII of FIG. 7;

figure 9 shows an enlarged detail of the apparatus in the area IX of figure 5;

FIG. 10 shows a vertical cross-sectional view of a portion of the apparatus along section line X-X in FIG. 6;

FIG. 11 shows a vertical cross-sectional view of a portion of the apparatus along section line XI-XI in FIG. 9;

FIG. 12 shows a vertical cross-sectional view of a portion of the apparatus taken along section line XII-XII in FIG. 9; and is

Figure 13 shows a cross-sectional view of a part of the apparatus along the section line XIII-XIII in figure 6.

Detailed Description

The invention will be described with reference to a shoulder box for tobacco products and an apparatus for manufacturing such a shoulder box. It will be appreciated that the invention may also be used with other types of packaging, and even outside the tobacco processing industry.

The package 10 shown in fig. 2 essentially comprises four parts according to fig. 1 and 3, namely a bottom part 11, a frame 12, a cover part 13 and an outer wrapper 14.

The bottom 11 of the package 10 has five walls, namely a large-area bottom wall 15 constituting the underside of the package 10 and four narrow side walls 16 folded at 90 ° with respect to the bottom wall 15.

The frame 12 has four narrow side walls 17 which extend on the inside and circumferentially along the side walls 16 of the bottom 11. The frame 12 projects above the bottom 11 and constitutes a shoulder for the cover 13. The frame 12 is fixed to the base 11 by gluing. In the present case by a surrounding glue line 18. Two adjacent side walls 17 are connected by an adhesive strip 19 to close the frame 12.

The lid portion 13 of the package 10 has five walls, namely one large-area lid wall 20 constituting the upper side of the package 10 and four narrow side walls 21 folded at 90 ° with respect to the lid wall 20. The side walls 21 enclose the frame 12 when the package 10 is closed (fig. 3).

The base part 11 and the cover part 13 are connected to each other by an outer envelope 14. The outer wrapper 14, like the above-described components of the package 10, is made from a one-piece blank 22 having in longitudinal direction, in succession, a bottom laminate 23, a side laminate 24, a lid laminate 25 and a side laminate 26. The corner laminates 27, 28 are arranged on the side laminates 24, 26 transversely to the longitudinal direction of the blank 22, and the

further side laminates

29, 30 are arranged on the cover laminate 25. The individual walls of the outer jacket 14 are delimited from one another by fold lines along which they are folded as shown in fig. 2 and 3. This mainly means that the side laminates 24, 26, 29, 30 are folded at 90 ° with respect to the cover laminate 25 and the bottom laminate 23 is folded at 90 ° with respect to the side laminate 24. The corner laminations 27, 28 are used to join the side laminations 24, 26, 29, 30.

One particular feature of the package 10 is that the lid wall 20 has a concave arch 31, i.e. is outwardly arched. In addition, the bottom wall 15 has a convex dome 31 oriented inwardly or inwardly of the package 10. In both cases, the arch 31 extends over substantially the entire lid wall 20 and bottom wall 15. It is also conceivable, however, for the arch 31 to extend only over part of these walls. Since the invention is not limited to use with shoulder boxes, it is of course also conceivable within the scope of the invention that other walls, only a single wall or more than two walls may be provided with the arch 31.

The production of the package 10 is explained below, in particular with regard to the provision of the dome 31:

a single blank 33 for the bottom 11 is taken from the first blank magazine 32 and provided with the arch 31 in the first deforming station 34. In a subsequent station the side walls 16 of the bottom 11 are erected. This may be accomplished by stamping the blank 33. The erected blank 33 is then pushed out and fed to the frame 12, which may be punched into the erected base 11. The unit thus formed, comprising the base 11 and the frame 12, is then pushed into the turret 35 and subsequently combined with the cover 13. The blanks 36 for the cover 13 are taken from a second blank magazine 37 and provided with the arches 31 in a second deforming station 38. Thereafter, the blank 36 is erected and fed to the unit comprising the base 11 and the frame 12 (fig. 5). The individual stations and method steps described above, with the exception of the deformation stations 34, 38, are known from the applications EP 3299158 A1 and EP 3299159 A1 of the applicant, to which reference is made for a complete disclosure.

The blanks 36 are fed individually and spaced apart from one another along a blank track 39 to a deforming station 38. In the illustrated embodiment, the blank 36 is handled unfolded. It is contemplated that the blank 36 may be handled with partial folding. The transport of the blanks 36 along the blank path 39 in the region of the deformation station 38 preferably takes place continuously.

The term "continuous" is used in the context of the present application to distinguish from "metronomic" or "step-wise" transport. If the speed and/or acceleration is not constant, continuous transport is still considered as long as the blanks do not stop.

In the deformation station 38, two rollers are arranged on different sides of the blank track 39, i.e. a moulding roller 40 is arranged on one side of the blank track 39 and a forming roller 41 is arranged on the other side of the blank track 39. The mold roll has a pressure-resilient surface and the mold roll 41 has a pressure-rigid or substantially pressure-rigid surface. The two rollers bear against one another with pressure, so that the blank 36 guided through between the rollers is plastically deformed by the rollers during movement to form the desired arch 31. Fig. 8 shows how forming roller 41 presses blank 36 with its pressure rigid surface into the pressure elastic surface of mold roller 40, thereby creating dome 31 on blank 36. The pressure-elastic surface of the mold roll 40 can be formed by a jacket 42 of the mold roll 40, which is made of a corresponding material, such as Zellvulkolan.

The distance and pressure between the rolls can be adjusted. In the present case, the forming roller 41 is supported on a lever system 43 which enables a variable feed to the moulding roller 40. In this way the pressing force between the two rollers can be adjusted, so that the degree or depth of the arch 31 can be influenced. Corresponding mounting of the mold roll is of course also conceivable (additionally or alternatively).

The forming roller 41 is supported on one end of a lever 44 of a lever system 43, which is pivotable about a bearing 45. An adjustment unit 46 acts on the other end of the lever 44 to control the change in the pressing force and the apparent degree of the arch 31 by pivoting the lever 44. Furthermore, this end of the lever 44 can also be assigned an (adjustable) end stop 47, which limits the pivoting.

The feed of the forming roll 41 to the moulding roll 40 and the adjustment of the end stop 47 can be effected mechanically, pneumatically or electrically. Furthermore, the feed and end stops 47 may also be part of the control system.

Furthermore, the adjustability of the forming roller 41 (pivoting to one side and thus reducing the pressure) can be used to protect the pressure-elastic surface of the mold roller 40, since it can be deformed on the surface under long rest conditions and continuous pressure loads.

In addition, the diameter of the forming roller 41 can be selected to be so small that at maximum feed, a limit is not exceeded at which the blank 36 will be damaged (e.g., delaminated).

After the deformation station 38, the blank 36 provided with the arch 31 is guided through a deflection station 48 before the side walls 21 are folded. The blanks 36 are held at least partially or in sections by lateral guides 49 on opposite side edges oriented parallel to the blank transport direction and are conveyed with a constant bending radius to maintain the curvature 31.

One particular feature of the deflection station 48 is that the blanks 36 are conveyed along a curved transport path 50, the direction of curvature of the transport path 50 corresponding to the direction of the arch 31 of the blank 36.

According to the illustration in fig. 7, after the deformation station 38 the transport path 50 is first oriented downward and then extends around the deflection roller 51 until the transport path 50 finally intersects and transitions into a straight section, to which a pair of transport rollers 52 adjoins. Lateral guides 49 are also present in the region of this straight section.

The arrangement or extension of the lateral guide 49 is shown in fig. 7. Lateral guides 49 extend above and below the transport path 50 on both sides to hold the opposite side edges of the blank 36 from above and below. On the circumference of the deflection roller 51, the blank 36 is held by an endless belt 53, which is guided by a plurality of deflection rollers 54.

One special feature is that the at least partially arched blank 36 is conveyed essentially stress-free, i.e. not only via the deflection station 48 but also in the region of the lateral guide 49. This can be ensured by a corresponding extension of the transport path 50 or by a corresponding distance of the lateral guide 49.

After the deflection station 48 or the deflection rollers 51, the blanks 36 are conveyed in the same direction as after the deformation station 38 or when supplied from the blank magazine 37.

In order for the blanks 36 not to intersect in the deflection station 48, the length of the blank 36 cannot be greater than the transport path 50 in the region of the deflection rollers 51.

After the transport path 50, the arched blank 36 is fed to a folding shaft 55, in which the blank 36 is pre-folded by means of a punch 56 (fig. 10). Where the side walls 21 of the blank 36 are folded by about 90 deg. and thus the two-dimensional curvature of the blank 36 becomes a three-dimensional arch 31.

In the region of the folding shaft 55, the pre-folded blank 36 is then pressed by means of a punch 56 between two adjacent drivers 57 of a conveyor belt 58 and is transported away laterally by means of the conveyor belt as a conveyor.

The above-described process of providing the arches 31 on the blanks 36 is carried out correspondingly on the blanks 33 in the deformation station 34.

The blank 36 for the cover 13 is also subjected to another special treatment before being combined with the base 11 and the frame 12. This involves handling in a device 59 for over-folding the folded edge that transitions to the side wall 21 of the blank 36.

In a first station 60 of the device 59, the side walls 21 extending in the transport direction of the blank 36 are pressed into the interior of the cover 13 by a rotating folding mechanism 61 and are folded over by more than 90 °. By this "over-folding" of the side walls 21, the material-dependent return force of the blank 36 is reduced and the folded side walls 21 are prevented from springing back.

In the next station 62 of the device 59, the same procedure is carried out for the other two side walls 21, i.e. the side walls 21 oriented transversely to the transport direction. However, for this purpose, the already folded side wall 21 is first moved back into the 90 ° position by the restoring mechanism 63, so that the two other side walls 21 do not "collide" with the already "folded-over" side wall 21 when they are "folded over". In order to "over-fold" the two further side walls 21, two further folding mechanisms 64 are provided, which are pivotably arranged below the conveyor belt 58. In the present case, the backward movement of the two further side walls 21 is no longer possible, but can be provided.

The folding mechanism 61 is disposed laterally on both sides of the transport path for the blank 36 and is driven in rotation, the folding noses 65 of the folding mechanism 61 coming into contact with the side wall 21 and pivoting the latter during further rotation.

The resetting mechanisms 63 are in the present case configured as hook-like mechanisms, which can be pivoted back and forth about an axis 66. The free end of the mechanism is moved from the inside onto the side wall 21 in order to fold it back.

The folding mechanism 64 is constructed substantially identically to the return mechanism 63, but here presses the free end of the side wall 21 towards the inside of the cover 13 in order to over-fold the side wall 21 or the blank 36.

List of reference numerals

10. Package (I)

11. Bottom part

12. Frame structure

13. Cover part

14. Outer sheath

15. Bottom wall (bottom)

16. Side wall (bottom)

17. Side wall (frame)

18. Glue mark

19. Adhesive strip

20. Cover wall (cover)

21. Side wall (cover)

22. Blank (outer cover)

23. Bottom laminate

24. Side lamination

25. Cover lamination

26. Side lamination

27. Corner lamination

28. Corner lamination

29. Side lamination

30. Side lamination

31. Arch shape

32. Blank member library (bottom)

33. Blank (bottom)

34. Deformation station (bottom)

35. Turret

36. Blank (cover)

37. Blank library (cover)

38. Deformation station (cover)

39. Blank rail

40. Mold roller

41. Forming roller

42. Protective sleeve

43. Lever system

44. Lever

45. Bearing assembly

46. Adjusting unit

47. End stop

48. Deflection station

49. Lateral guiding device

50. Transport route

51. Deflection roller

52. Conveying roller

53. Circulating belt

54. Deflection roller

55. Folding shaft

56. Punch head

57. Belt driving device

58. Conveyor belt

59. Device for measuring the position of a moving object

60. Station

61. Folding mechanism

62. Station

63. Resetting mechanism

64. Folding mechanism

65. Folding nose

66. Axial line

Claims

1. A method for handling blanks (33, 36) made of packaging material, wherein the blanks (33, 36) are provided with an arch (31), and wherein the blanks (33, 36) are moved along a blank track (39) through a deformation station (34, 38), which arch (31) is created during the movement of the blanks (33, 36) along the blank track (39) in the deformation station (34, 38), characterized in that the at least partially arched blanks (33, 36) are transported after the deformation station (34, 38) in a deflection station (48) along an at least partially curved transport path (50) for maintaining the bending radius of the blanks, which transport path (50) has a bending direction corresponding to the direction of the arch (31) of the blanks (33, 36).

2. Method according to claim 1, characterized in that for the purpose of imparting the arch, the blank (33, 36) is guided around a curved surface of a pressure-rigid body, whereby bending stresses are induced in the blank (33, 36) which lead to a permanent plastic deformation of the blank (33, 36) in the form of an arch (31).

3. Method according to claim 1 or 2, characterized in that the radius of the at least partially curved transport path (50) at least partially corresponds to the radius of the at least partially arched blank (33, 36).

4. Method according to claim 1, characterized in that the at least partially curved transport paths (50) intersect in such a way that the at least partially arched blanks (33, 36) are transported after the deflection station (48) substantially in the same transport direction as in the deformation station (34, 38).

5. Method according to claim 4, characterized in that the length of the at least partially curved transport path (50) in the deflection station (48) is greater than the length of the blanks (33, 36) in the transport direction.

6. Method according to claim 4, characterized in that the at least partially arched blanks (33, 36) are transported in the at least partially curved transport path (50) with a direction of movement maintained.

7. A method as claimed in claim 3, characterized in that the at least partially arched blanks (33, 36) are conveyed along a straight transport path after the deflection station (48).

8. Method according to claim 6, characterized in that the at least partially arched blanks (33, 36) are guided during transport at least partially by lateral guide means (49) in the at least partially curved transport path (50) in the region of laterally opposite edges of the blanks (33, 36), i.e. in the region of edges of the blanks (33, 36) oriented in the transport direction.

9. Method according to claim 7, characterized in that the at least partially arched blanks (33, 36) are guided during transport at least partially by lateral guide means (49) in the region of laterally opposite edges of the blanks (33, 36) in the linear transport path, i.e. in the region of edges of the blanks (33, 36) oriented in the transport direction.

10. Method according to claim 8 or 9, characterized in that the at least partially arched blanks (33, 36) are transported along the at least partially curved transport path (50) and/or along the lateral guide (49) without external forces acting on the blanks (33, 36) that disrupt the arch (31).

11. Method according to claim 1, characterized in that the at least partially arched blank (33, 36) is provided with a two-dimensional arch in a deformation station (34, 38) and that thereafter the three-dimensional arch of the blank (33, 36) is produced by folding the side walls (16, 21) of the blank (33, 36), i.e. by folding the side walls oriented longitudinally and/or transversely to the transport direction of the blank (33, 36).

12. Method according to claim 1, characterized in that the blank (33, 36) is provided with a concave and/or convex arch in a deformation station (34, 38).

13. Method according to claim 1 or 2, the blank (36) having a wall (20) and side walls (21) provided on the wall (20), which side walls are folded with respect to the wall (20) to form at least part of the package (10), characterized in that at least one first one of the side walls (21) is folded with respect to the wall (20) by an angle >90 ° and subsequently folded back such that the angle ≦ 90 °, and after this at least one second one of the side walls (21) is folded with respect to the wall (20) by an angle >90 °.

14. A method as claimed in claim 13, characterized in that two first ones of the side walls (21) are provided on opposite sides of said wall (20) and folded back together, and two second ones of the side walls (21) are provided on the other opposite sides of the wall (20) and folded together.

15. A device for handling blanks (33, 36) made of packaging material, which device is configured for providing the blanks (33, 36) with an arch (31), and which device has a deformation station (34, 38) through which the blanks (33, 36) can be moved along a blank track (39), which deformation station (34, 38) is configured for imposing the arch (31) on the blanks (33, 36) by plastic deformation during the movement of the blanks (33, 36) along the blank track (39), characterized in that a deflection station (48) is provided after the deformation station (34, 38), which deflection station is configured for conveying the arched blanks (33, 36) along a curved transport path (50) for maintaining the bending radius of the blanks, the bending direction of the transport path (50) at least partially corresponding to the direction of the arch (31) of the blanks (33, 36).

16. Apparatus according to claim 15, characterized in that at least two mutually cooperating rollers are provided in the deformation station (34, 38), which rollers are positioned on different sides of the blank track (39) and between which the blank (33, 36) can be moved in such a way that bending stresses are generated in the blank (33, 36) for adding the arch (31) to at least one wall of the blank (33, 36).

17. The apparatus according to claim 16, characterized in that one of said rolls, the moulding roll (40), has a pressure elastic surface and the other roll, the forming roll (41), has a pressure rigid surface.

18. A device according to claim 17, characterised in that the distance between the rollers can be adjusted by supporting the forming roller (41) with a lever system (43), wherein the pressing force between the rollers can be adjusted to influence the apparent degree of the camber (31) of the blanks (33, 36).

19. The apparatus of claim 18, wherein the rollers are movable away from each other.