FOLDING BELT FOR A DEVICE FOR FOLDING FOLDING-BOX BLANKS

Abstract

The invention relates to a folding belt, which can be used, for example, in a folding machine. By means of an improved profile of the folding belt, the quality of the folding is improved and, in particular, undesired fishtailing is reduced.

Claims

1. Folding belt for use in a device for folding folding-box blanks that are flat in the initial state, the folding belt having a front and a back, the back of the folding belt being provided with a profile that forms a bearing surface for a relevant side flap, is sawtooth-shaped in the longitudinal section with regard to the longitudinal extension of the folding belt, and comprises at least one apex and has a minimum, and the bearing surface being between the leading minimum and the following apex, characterized in that the profile comprising at least one curved portion when viewed in cross section, characterized in that the tangents at the start and end of the curved portion enclose an angle of 90 or less and at least of 30, in that the tangent at the start of the curved portion and the toothed belt enclose an angle between 5 and 45, and in that a length of the bearing surface is approximately equal to a length of the side flap to be folded.

2. (canceled)

3. Folding belt according to claim 1, characterized in that the tangent at the start of the curved portion extends in parallel with a toothed belt of the folding belt.

4. (canceled)

5. Folding belt according to claim 1, characterized in that the curved portion has the shape of a circular segment, of an elliptical segment or of another polynomial of the second order.

6. Folding belt according to claim 1, characterized in that a polygon having at least three straight lines is brought into close proximity to the curved portion (51).

7. Folding belt according to claim 1, characterized in that the profile, when viewed in the longitudinal section, forms an oblique rear surface between the apex and the following minimum.

8. Folding belt according to claim 1, characterized in that the folding belt, when seen in the longitudinal direction, comprises a plurality of apexes and associated minima, in that each portion of the profile that begins with a minimum, comprises an apex and ends at the adjacent minimum forms a sawtooth.

9. Folding belt according to claim 1, characterized in that the distance between two adjacent minima is greater than the dimensions of the folding-box blanks, measured in the direction in parallel with the folding lines.

10. Folding belt according to claim 1, characterized in that the apex of each sawtooth is, with regard to the direction of movement of the folding belt, at a distance from the previous minimum that is at least equal to the distance from the minimum following the apex in the direction of movement.

11. Folding belt according to claim 1, characterized in that on the back of the folding belt, the profile consists of a flexible material.

12. Folding belt according to claim 11, characterized in that the profile through supports at least one strip that is made of a flexible material and is upright relative to the back, the free narrow end of which strip facing away from the folding belt forms the bearing surface.

13. Folding belt according to claim 12, characterized in that the strips are arranged so as to be undulating or meandering in the longitudinal direction of the folding belt.

14. Folding belt according to claim 1, characterized in that the folding belt is symmetrical in cross section.

15. Folding belt according to claim 1, characterized in that the flat belt is a toothed belt.

16. Folding belt according to claim 1, characterized in that the distance between two adjacent minima is equal to the dimensions of the folding-box blanks, measured in the direction in parallel with the folding lines.

17. Folding belt according to claim 1, characterized in that the distance between two adjacent minima is smaller than the dimensions of the folding-box blanks, measured in the direction in parallel with the folding lines.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the subject matter of the invention are shown in the drawings, in which:

[0030] FIG. 1 shows FIG. 2 of DE 39 08 981 A1 (prior art),

[0031] FIG. 2 shows FIG. 11 of DE 39 08 981 A1 (prior art),

[0032] FIG. 3 shows FIG. 4 of DE 39 08 981 A1 (prior art),

[0033] FIGS. 4 and 5 are cross sections of folding belts according to the invention,

[0034] FIG. 6 is an isometric and simplified illustration of a folding process in three different steps (I, II and III),

[0035] FIG. 7 is sections, belonging to step I, along lines A-A and B-B,

[0036] FIG. 8 is sections, belonging to step II, along lines A-A and B-B,

[0037] FIG. 9 is sections, belonging to step III, along lines A-A and B-B, and

[0038] FIG. 10 is an isometric and simplified illustration of a folding process comprising folding two folding-box blanks in each step.

DESCRIPTION OF THE EMBODIMENTS

[0039] Like reference signs are used throughout for like components.

[0040] As is already known from DE 39 08 981 A1, a folding machine comprises two continuous folding belts 13, which, in their general extension, begin at the side underneath a guideway 5 and end at the side above the guideway 5. The two folding belts 13, only one of which is shown in FIG. 1, are mirror-symmetric with respect to the longitudinal axis of the folding machine.

[0041] The folding belt 13 on the left side of the folding machine, viewed in the direction of movement of the folding-box blanks 2, runs around two pulleys 15 and 16, which are rotatably mounted on axes 17 and 18 of the base frame. One of the pulleys 15 or 16 is coupled to a drive device in order to move the folding belt 13 synchronously with the toothed belts (not shown) responsible for feeding the folding-box blanks. The axes 17 and 18 extend mutually in parallel and at an angle of 45 relative to the plane defined by the guideways 5. The orientation of the axes 17 and 18 is such that they point downwards in the direction of the plane of symmetry of the folding machine 1.

[0042] In the direction of transport of the folding-box blanks 2, even more pairs of folding belts (not shown) according to the invention may be arranged behind the folding belt 13. These folding belts extend substantially as a continuation of the folding belt 13 and continue the folding movement. This process and the arrangement of the folding belts is described in detail in DE 39 08 981 A1.

[0043] Due to the arrangement of the total of four or more folding belts, a tight side is produced on each of the folding belts 13, which side runs in the direction of the transport movement of the folding-box blanks 2 and interacts with the folding-box blank 2, while a slack side runs back in the opposite direction without touching the folding-box blank 2. The direction of the transport movement and of the tight side is shown in FIGS. 3, 6 and 10 by an arrow 48.

[0044] FIG. 2 shows a configuration in which the following folding belt 14 is crossed by way of example. In the case of the following folded belt 14 (according to FIG. 11 of DE 39 08 981 A1), the same profile is used; only the axes 21, 22 are oriented differently. The axis 21 is arranged vertically next to the guideway 5, whereas the axis 22 of the return roller 22 located further upstream is above the guideway 5. The relevant return roller 22 is moved, relative to the folding line 31, to the center of the folding machine 1 so that the pressure can be applied to the left folding belt 14 on the right of the folding line 31. The height of the axis 22 above the guideway 5 corresponds to the radius of the return roller 22 in addition to the height of the apex 42 above the front 38 of the toothed belt.

[0045] In this arrangement, the first folding belt 13 raises the side flap 28 vertically, because the contact points between the bearing surface according to the invention of the folding belt and the side flap 28 moves upwards along an ascending helix. At the same time, the contact surface rolls over the side flap 28 without any appreciable relative movement between the bearing surface according to the invention of the folding belt and the side flap 28. This protects the (printed) side flap 28 and prevents signs of abrasion on the side flap 28.

[0046] The second folding belt 14 then bends (as can be clearly seen in FIG. 2) the side flap 28 towards the central piece 27.

[0047] The longitudinal profile 19 on the back of the folding belts 13, 14 will be explained below with reference to FIG. 3. In the longitudinal section or the side view of the folding belts 13, 14, the profile is sawtooth-shaped and is located on the back of a toothed belt 40, which therefore ensures the positive and thus slip-free movement of the folding belts 13, 14.

[0048] The toothed side of the toothed belt 40 is referred to as the front 38. The sawtooth-shaped profile 19 is arranged on the back of the toothed belt 40. Said profile consists, in the longitudinal section, of a comparatively minimally inclined bearing surface 39 and a greatly inclined rear surface 41. An apex 42 of the profile is between the bearing surface 39 and the rear surface 41 in each case, while the rear surface 41 and the bearing surface 39 are delimited at the other two ends by two minima 43. This profile design is arranged multiple times along the folding belts 13, 14, the distance between two minima 43 corresponding to the distance from center to center of two consecutive folding-box blanks 2, which comprise, when viewed in the direction of transport of the folding-box blanks 2, the maximum dimensions that can be processed on the folding machine 1.

[0049] FIG. 4a is a section through the folding belts 13, 14 according to the invention along the line A-A in FIG. 3.

[0050] A profile 19 according to the invention is formed on the back of the toothed belt 40. Said profile is made from a flexible and resilient material. Closed-pore plastics foams, such as polyurethane, have proven to be suitable materials.

[0051] A new feature of this profile 19 is that it comprises a curved portion 51, which in this embodiment begins at the highest point of the profile 19 and then transitions into a curved line that slopes to the right in FIG. 4a. The point at the greatest distance from the toothed belt 40 is referred to as the highest point of the profile 19.

[0052] Two parameters of the curved portion 51 according to the invention are the tangent 53 at the start and the tangent 55 at the end of the curved portion 51.

[0053] In this example, the tangents 53 and 55 at the start and end of the portion 51 enclose an angle of approximately 90. The angle enclosed by the tangents 53 and 55 corresponds approximately to the folding angle that is brought about by a folding belt 13, 14.

[0054] A third parameter of the curved portion 51 according to the invention is the angle between the tangent 53 at the start and the plane spanned by the toothed belt 40. In the embodiment shown in FIG. 4a, the tangent 53 at the start of the curved portion 51 extends in parallel with the toothed belt 40. In FIG. 4a, the plane in which the toothed belt 40 extends is shown by a line 57.

[0055] In this embodiment, the curved portion 51 has the shape of an arc.

[0056] The overall height H of the profile 19 and a height H.sub.51 of the curved portion 51 are shown in FIG. 4a. In this embodiment, H=H.sub.51. In addition, a height H.sub.51 of the curved portion 51 is shown.

[0057] Correspondingly, an overall width B of the profile 19 and a width B.sub.51 of the curved portion 51 are shown in FIG. 4a.

[0058] A radius of the curved portion 51 is equal to the overall height H and a width B of the folding belt.

[0059] FIG. 4b is the section through the profile 19 in the region along the line B-B. The significant difference is the height greater height of the profile 19. The wedge shape, which can be seen in the side view of the folding belt 13, 14 (see FIG. 3), of the bearing surface 39 is achieved by the height of the profile 19 linearly increasing from the minimum 43 to the apex 42.

[0060] FIGS. 5a and 5b show a further embodiment of a profile 19 according to the invention.

[0061] In this embodiment, the curved portion does not extend over the entire width of the toothed belt 40. The tangents 53 and 55 enclose an angle of .sub.1 of approximately 45.

[0062] The curved portion is elliptical, the profile 19 being curved at the highest point to a lesser extent than in the region of the tangent 55. Here, too, the height of the profile 19 continuously increases.

[0063] However, it is also possible to design the curved portion 51 as a parabola or another curved line, preferably in the form of a polynomial of the second order.

[0064] In this embodiment, the height H.sub.51 of the curved portion 51 is less than the overall height H. H:H.sub.51 is approximately equal to 4:3.

[0065] In this embodiment, the width B.sub.51 of the curved portion 51 is also less than the width B of the folding belt. B:B.sub.51 is approximately equal to 4:3.

[0066] The process of folding a side flap 28 is shown in the following in combination with FIG. 6. In this case, three folding belts 13 are arranged one behind the other on each side. None of the folding belts 13 is crossed.

[0067] The side flaps 28 are folded by 180 in three steps I, II and III corresponding to three folding belts 13.I, 13.II and 13.III on each side. So as not to overload the drawing, not all of the parts are provided with reference signs, but instead reference is made to the other drawings.

[0068] In step I, the unfolded side flap 28 is folded by an angle of approximately 60. This is achieved by first folding belts 13.I according to the invention. The pulley 16 arranged further behind is raised relative to the front pulley 15. So that the bearing surface 39 of the folding belt rests against the entire length of the side flap 28, the minimum 34 of the folding belt 13 is behind the apex 42 in the running direction.

[0069] In step II, the side flaps 28 are further folded up to an angle of approximately 120. This is achieved by second folding belts 13.II according to the invention. The pulley 16 arranged further behind is raised relative to the front pulley 15 and is moved in the direction of the plane of symmetry.

[0070] Folding is carried out in a similar manner in step III.

[0071] In the case of the folding belts 13.II and 13.III used in steps II and III, the minima 43 of the folding belts 13 are arranged in the running direction behind the apex 42.

[0072] FIG. 7 is partial sections through a folding-box blank and the folding belt 13 according to the invention in two intersection planes A-A and B-B during the first step I (see FIG. 6) by way of illustration.

[0073] FIG. 8 is partial sections through a folding-box blank and the folding belt 13 according to the invention in two intersection planes A-A and B-B during the second step II (see FIG. 6) by way of illustration.

[0074] FIG. 9 is partial sections through a folding-box blank and the folding belt 13 according to the invention in two intersection planes A-A and B-B during the third step III (see FIG. 6) by way of illustration.

[0075] FIG. 10 shows the simultaneous folding of a plurality of folding-box blanks in one step (multi-box method).

[0076] As can be seen by comparing FIGS. 6 and 10, the significant difference is that in each of the three steps, two folding-box blanks are folded.

[0077] Correspondingly, the folded belts 13 used in the process have the sawtooth profile shown in the lower part of FIG. 10. The distance between two minima or two apexes corresponds approximately to the length or the distance S between the front edges of the folding-box blanks.