GRIPPER UNIT AND STRETCHING UNIT

Abstract

The present disclosure relates to a gripper unit for a stretching unit as well as a stretching unit. The gripper unit includes a base body, a gripping jaw and at least one blade flap. The blade flap is located pivotably on the base body about a pivot axis and includes a complementary gripping jaw on one first end, the complementary gripping jaw interacting with the gripping jaw in a gripping position in order to grip a material web. In addition, the blade flap includes a neck section and a head section, wherein the neck section extends from the pivot axis to the head section, the head section forming a second end of the blade flap. The head section has an upper length (L.sub.K) measured in a direction of travel (R) of the gripper unit, which is at least 50% longer than a minimum length (L.sub.H) of the neck section.

Claims

1. A gripper unit for a stretching unit, such as a transverse direction orienter or a simultaneous stretching unit, wherein the gripper unit is configured to be guided on a guide rail, and wherein the gripper unit comprises: a base body, a gripping jaw and at least one blade flap, wherein the blade flap is located pivotably on the base body about a pivot axis in order to be pivoted from a gripping position into an open position, wherein the blade flap comprises a complementary gripping jaw on one first end, said complementary gripping jaw interacting with the gripping jaw in the gripping position to grip a material web, and wherein the blade flap comprises a neck section and a head section, wherein the neck section extends from the pivot axis to the head section, said head section forming a second end of the blade flap, and wherein the head section has a upper length L.sub.K, measured in a direction of travel of the gripper unit, said upper length L.sub.K being at least 50% longer than a minimal length L.sub.H of the neck section, measured in a direction of travel, R, of the gripper unit.

2. The gripper unit according to claim 1, wherein the gripper unit comprises multiple blade flaps, wherein the blade flaps are arranged adjacent to each other in the direction of travel of the gripper unit.

3. The gripper unit according to claim 1, wherein the length of the neck section tapers in the direction of the head section at least in regions.

4. The gripper unit according to claim 1, wherein the head section comprises a recess or a through hole, wherein the recess optionally comprises a depth amounting to at least 30%, or at least 50%, or at least 70% of the width of the head section.

5. The gripper unit according to claim 4, wherein the recess or the through hole comprises an upper edge that runs substantially parallel to an upper edge of the head section, wherein the spacing between the upper edge of the recess or the through hole and the upper edge of the head section is optionally in the range from 2 mm to 6 mm, or in the range from 2.5 mm to 5 mm, or in the range from 3 mm to 4 mm.

6. The gripper unit according to claim 1, wherein the upper length L.sub.K of the head section is in the range from 20 mm to 60 mm, or in the range from 35 mm to 55 mm, or in the range from 45 mm to 50 mm, and/or wherein the blade angle () of the head section is in a range from 0 to 80, or in a range from 30 to 75, or in a range from 45 to 65.

7. The gripper unit according to claim 1, wherein the head section comprises a larger width (B.sub.K) than the neck section, and wherein the width B.sub.K of the head section is optionally in the range from 2 mm to 6 mm.

8. The gripper unit according to claim 1, wherein the head section comprises a height H.sub.K, measured in the main extension direction of the neck section, in the range from 10 mm to 30 mm.

9. The gripper unit according to claim 1, wherein the gripper unit comprises furthermore at least one guide element, wherein said at least one guide element is arranged on the base body and is configured to guide the gripper unit on a guide rail, and wherein said at least one guide element comprises a slide element or a guide roller.

10. The gripper unit according to claim 1, wherein the base body is configured furthermore to be connected to a chain link and/or wherein the gripper unit comprises at least one chain link, wherein the base body is connected in a fixed manner to at least one chain link.

11. The gripper unit according to claim 1, wherein the blade flap comprises a stop point for a prestressed element, and wherein a prestressed element, such as a compression spring, is located between the stop point and the base body in order to prestress the blade flap in the gripping position.

12. The gripper unit according to claim 11, wherein the stop point is located in a region between the complementary gripping jaw and the pivot axis, or wherein the pivot axis is located in a region between the complementary gripping jaw and the stop point.

13. The gripper unit according to claim 1, wherein the head section is magnetized greater than the neck section and/or wherein the head section comprises at least one magnet.

14. The gripper unit according to claim 1, wherein the blade flap is made of steel, and wherein the head section comprises a lower carbon content than the neck section.

15. The gripper unit according to claim 1, wherein the head section is heat-treated.

16. The gripper unit according to claim 15, wherein the head section is hardened.

17. A stretching unit, wherein the stretching unit comprises at least one guide rail and at least one gripper unit according to claim 1, wherein the gripper unit is guided on the guide rail.

18. The stretching unit according to claim 17, wherein the stretching unit is a transverse direction orienter or a simultaneous stretching unit.

19. The stretching unit according to claim 17, wherein the stretching unit comprises at least one magnetic opening device and/or at least one magnetic closing device, said magnetic closing device comprising at least one magnet, said magnet being located in the region of said at least one guide rail in such a way that the blade flap of a gripper unit is pivoted into the open position when the gripper unit is guided past the magnetic opening device, and said magnetic closing device comprising at least one magnet, said magnet being located in the region of said at least one guide rail in such a way that the blade flap of a gripper unit is pivoted into the gripping position when the gripper unit is guided past the magnetic closing device.

20. The stretching unit according to claim 19, wherein said at least one magnet has a length (L.sub.M), measured in a direction of travel (R) of the gripper unit (100), which fulfils the condition 0.8 L.sub.KL.sub.M1.2 L.sub.K.

21. The stretching unit according to claim 19, wherein the spacing between two adjacent magnets is smaller or equal to (L.sub.ML.sub.K)/2.

22. The stretching unit according claim 17, wherein an air gap(s) between said at least one magnet and the head section of a blade flap is in the range from 1.5 mm to 5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present disclosure is explained exemplarily in more detail in the following by means of the enclosed figures.

[0058] FIG. 1 shows a schematic view of a first embodiment of a stretching unit according to an aspect of the present disclosure,

[0059] FIG. 2 shows a schematic view of a second embodiment of a stretching unit according to an aspect of the present disclosure,

[0060] FIG. 3 shows a schematic view of a gripper unit according to an aspect of the present disclosure;

[0061] FIG. 4 shows a schematic view of a blade flap according to the state of the art;

[0062] FIG. 5 shows a schematic view of a blade flap according to an aspect of the present disclosure;

[0063] FIG. 6 shows a schematic view of a further blade flap according to an aspect of the present disclosure;

[0064] FIG. 7A shows a schematic view of a blade flap comprising magnets for opening/closing;

[0065] FIG. 7B shows a graph showing the progression of the magnetic force; and

[0066] FIG. 8 shows a further graph showing the progression of the magnetic force.

DETAILED DESCRIPTION

[0067] In particular, FIG. 1 shows a stretching unit 10. This comprises an oven 14 as well as two drive systems 16.

[0068] The drive systems 16 are located mirror-symmetrically with respect to a symmetry axis S of the stretching unit 10 and extend at least in part into the oven 14. The drive systems 16 run outside of the oven 14 in an entry zone 18 as well as an exit zone 20, in which a material web 50 of the stretching unit 10 is fed and removed.

[0069] In addition to the entry zone 18 and the exit zone 20, the stretching unit shown here comprises at least three further zones 22, 24, 26.

[0070] The zones 22, 24, 26 adjoin each other so that, as seen along the usual direction of travel and drawing direction R of the stretching unit 10, the first zone 22 initially adjoins the entry zone 18, then the second zone 24, then the third zone 26, and finally the exit zone 20.

[0071] The drive systems 16 have a first spacing from each other in the first zone 22 of the stretching unit 10 which adjoins the entry zone 18, said first zone 22 also being termed the preheating zone.

[0072] In the second zone 24, also termed the stretching zone, the spacing of both drive systems 16 from each other increases until finally at the start of the third zone 26, also termed heat treatment zone, a second spacing is attained.

[0073] Each of the drive systems 16 has a guide rail 40, 42 in the known manner, on which a multitude of gripper units 100 are guided. The gripper units 100 can be moved along the guide rail 40, 42 by means of a drive of the respective drive system 16.

[0074] In FIGS. 1 and 2, only two gripper units 100 per drive system 16 are shown symbolically in each case. The stretching unit 10 comprises however a plurality of gripper units 100.

[0075] The guide rails 40, 42 of the respective drive systems 16 circle a closed path from the entry zone 18 to the exit zone 20 and back again. The guide rail section forming the forward travel extends in the intended direction of travel of the gripper units 100 between the entry zone 18 and the exit zone 20 within the oven 14.

[0076] The guide rail section that runs from the exit zone 20 to the entry zone 18 in the normal operating direction and forms the return is also located within the oven 14 in the shown embodiment. As shown in the embodiment according to FIG. 2, it can however be located outside the oven 14.

[0077] To operate the stretching unit 10, the material web 50 to be stretched, for example a plastic film, is fed into the entry zone 18 of the stretching unit 10 in the drawing direction R. To this end, the material web 50 is fastened by means of its edges running in the drawing direction R to both drive systems 16.

[0078] More specifically, the edges of the material web 50 clamped by a corresponding gripper unit 100 and thus moved by the movement of the gripper units 100 along the guide rails 40, 42 of the drive systems 16.

[0079] In the entry zone 18, the material web 50 has a width E (entry width) perpendicular to the drawing direction R that corresponds approximately to the first spacing between the drive systems 16.

[0080] The material web 50 is then guided through the first zone 22 and heated there. In the subsequent second zone 24, thus the stretching zone, the material web 50 is stretched as the spacing of the drive systems 16 is increased continuously. At the end of the second zone 24, the material web 12 has a second width A (exit width).

[0081] After completing the stretching, the material web 50 now passes through the third zone 26, in which a relaxation of the material web 50 can take place before the material web 50 is detached from the gripper units 100 in the exit zone 20 and leaves the stretching unit 10 with the width A.

[0082] For example, the stretching unit 10 is a film-spreading stretching unit or transverse direction orienter, also referred to in short as a TDO. It is also conceivable that the stretching unit 10 is a simultaneous stretching unit, in which the material web 50 can be stretched in the second zone 24, thus the stretching zone, not only in the direction transverse to the drawing direction R but also in the drawing direction R.

[0083] During the processing of the material web 50, large tensile forces act in a tensile direction above all on the gripper units 28 in the second zone 24, thus the stretching zone. The tensile direction is predominantly in a primary direction P of the gripper units 100 and to a lesser extent transverse to the primary direction P.

[0084] Furthermore, the stretching unit 10 comprises at least one magnetic opening device 30 which opens the gripper units 100 after passing through the stretching unit or the relaxation zone in a contactless manner (magnetically). Furthermore, the stretching unit comprises at least one magnetic closing device 31 which closes the gripper units 100 in a contactless manner in order to grip the material web 50.

[0085] FIG. 3 shows a schematic view of a gripper unit 100 according to an aspect of the present disclosure.

[0086] The gripper unit 100 comprises a base body 110 and a blade flap 120. The blade flap 120 is mounted pivotably (angle ) on the base body 110 about a pivot axis 122 in order to be pivoted from a gripping position (dashed representation) into an open position (solid line).

[0087] Furthermore, the gripper unit 100 comprises a guide element 140 which is used to guide the gripper unit on a guide rail 40.

[0088] A gripping jaw 114 is located additionally on the base body 110 (or designed integrally with the base body 110) which interacts with a complementary gripping jaw 124 that is part of the blade flap 120. In the gripping position, the material web 50 is clamped between the gripping jaws 114, 124.

[0089] Furthermore, the blade flap 120 comprises a neck section 126 and a head section 128. The neck section 126 extends from the pivot axis 122 to the head section 128.

[0090] To be capable of opening or closing the blade flap, magnetic opening or closing devices 30, 31 can be used which comprise at least one magnet 36. Depending on the arrangement of the magnet 36, a magnetic force F.sub.M acts on the blade flap 120, in particular its head section 128, said magnetic force F.sub.M forcing the blade flap into the gripping position (as in FIG. 3) or into the open position.

[0091] To prevent that the magnet 36 lifts the gripper unit 100 from the guide rail 40, a counter magnet 38 can be arranged which draws the gripper unit 100 to the guide rail 40.

[0092] Furthermore, a stop point 125 can be located on the blade flap (for example in the form of an ear). The stop point 125 is used to fasten a prestressed element (not shown). The prestressed element, in particular a compression spring, can be located between the stop point 125 and the base body 110 in such a way to prestress the blade flap 120 in the gripping position.

[0093] FIG. 4 shows a schematic view of a blade flap according to the state of the art. This known blade flap 120 can also be mounted about a pivot axis 122 in order to be pivoted from an open position into a gripping position. However, a neck and head section according to an aspect of the present disclosure is not provided here so that this type of blade flap cannot be opened reliably and accordingly also cannot be closed reliably by means of the magnetic opening device at high speeds.

[0094] In FIG. 5, a blade flap 120 of a gripper unit 100 according to an aspect of the present disclosure is shown. This blade flap 120 comprises a neck section 126 that extends from the pivot axis 122 to the head section 128. At one first end 121, the blade flap comprises a complementary gripping jaw 124. On the opposing second end 123, the head section 128 is located.

[0095] The head section 128 has an upper length L.sub.K (measured in a direction of travel R of the gripper unit 100) which is at least 50% longer than a minimum length L.sub.H of the neck section 126. The shown blade flap thus tapers in the neck section before it widens again in the head section.

[0096] In the example shown here, the upper length L.sub.K of the head section 128 is in the range from 20 mm to 60 mm, in particular in the range from 35 mm to 55 mm, in particular in the range from 45 mm to 50 mm.

[0097] Furthermore, the head section can comprise a height H.sub.K, measured in the main extension direction of the neck section that is in the range from 10 mm to 30 mm, or in the range from 15 mm to 25 mm, or in the range from 17 mm to 21 mm

[0098] This geometry results in a considerable increase in the magnetic force F.sub.M so that more rapid line speeds are possible with consistently high reliability when opening/closing.

[0099] Optionally, the head section 128 comprises a recess 129 or a through hole. This is described in detail in relation to FIG. 6.

[0100] As shown in FIG. 5, the stop point 125 can be in a region between the pivot axis 122 and the head section 128. It is however also possible to locate the stop point 125, as shown in FIG. 6, between the complementary gripping jaw 124 and the pivot axis 122.

[0101] FIG. 6 shows a further blade flap 120 of a gripper unit 100 according to an aspect of the present disclosure. Same elements are denoted here with the same reference signs so that a repeated description has been dispensed with.

[0102] In the blade flap 120 shown in FIG. 6, the head section 128 comprises a larger width B.sub.K than the neck section 126. The width B.sub.K of the head section 128 is optionally in the range from 2 mm to 6 mm, or in the range from 3 mm to 5.5 mm, or in the range from 4 mm to 5 mm.

[0103] A recess 129 is also introduced into the head section 128. The recess 129 comprises a depth amounting to at least 30%, or at least 50%, or at least 70% of the width B.sub.K of the head section 128.

[0104] Furthermore, the recess 129 comprises an upper edge that extends substantially parallel to an upper edge of the head section 128. The upper end of the head section is thus designed thicker. Similarly, thickened regions can be designed laterally of the recess.

[0105] The spacing between the upper edge of the recess 129 and the upper edge of the head section 128 is, for example, in the range from 2 mm to 6 mm, or in the range from 2.5 mm to 5 mm, or in the range from 3 mm to 4 mm. The laterally thickened regions can comprise a linear expansion (in the direction of travel R) that is in the range from 2 mm to 6 mm, or in the range from 2.5 mm to 5 mm, or in the range from 3 mm to 4 mm.

[0106] FIG. 7A shows the blade flap 120 from FIG. 5, which is guided past an opening device or its magnets 32, 34, 36 in the direction of travel R. Here, a magnetic force F.sub.M acts on the head section 128 of the blade flap 120.

[0107] In addition, the blade angle is drawn here, thus the angle formed by a side edge of the head section with a line parallel to the pivot axis 122. For example, the blade angle is in a range from 0 to 80, or in a range from 30 to 75, or in a range from 45 to 65.

[0108] The graph shown in FIG. 7B shows how the magnetic force F.sub.M has changed in comparison to the blade flap of the state of the art shown in FIG. 4. The solid line shows the magnetic force F.sub.M acting on the blade flap according to an aspect of the present disclosure. The dashed line shows the magnetic force F.sub.M acting on a typical blade flap of the state of the art.

[0109] Firstly, the magnetic force could be increased by 25-35%. In addition, it shows that the progression of the magnetic force in the linear expansion x, i.e. in the direction of travel R, forms an even plateau-without local peaks. Both effects result in reliable opening/closing of the blade flap according to an aspect of the present disclosure.

[0110] In FIG. 8, a further graph is shown which shows the progression of the magnetic force F.sub.M depending on the angular position a. The solid line shows the magnetic force F.sub.M acting on the blade flap according to an aspect of the present disclosure. The dashed line shows the magnetic force F.sub.M acting on a typical blade flap of the state of the art. Again, it shows here that in particular a considerably stronger magnetic force acts on the pivoted blade flap (deflection 10)

[0111] The gripper units according to aspects of the present disclosure and the stretching unit can thus be operated at high speeds and provide at the same time high reliability during contactless opening/closing of the gripper units.