Mandrel and method for expanding a flat tubular foil

Abstract

A mandrel (1; 100) suspended within a sleeving device (3) for expanding a flat tubular foil into a tubular form having a round cross-section is provided, the mandrel extending along a central axis (2) of the mandrel in the foil feed direction and having an expansion portion (14) configured to change the cross-section of the tubular foil from a flat cross-section (12) to a round cross-section. The expansion portion (14) comprises a first length (20) configured to change the cross-section of the tubular foil from the flat cross-section (12) to a first polygonal cross-section defined by four corner points (22a-22d) in the foil feed direction, and a second length (30) configured to change the cross-section of the tubular foil from the first polygonal cross-section to a second polygonal cross-section defined by eight or more corner points (32a-32h).

Description

[Technical Field]

[0001] The present invention relates to a mandrel suspended within a sleeving device, a device for forming folds in a flat tubular foil, a sleeving device, and a method for expanding a flat tubular foil into a tubular form having a round cross section. [Background technology]

[0002] Mandrels suspended within sleeving devices are well known in the art. The mandrel is an expanding element for unfolding a flat tubular foil to form a sleeve having a round or circular cross-section that substantially matches the shape of a product, such as a food container, bottle, jar, bowl, or holder. Sleeving devices typically include a frame, a foil supply unit attached to the frame for supplying the tubular foil to the mandrel, a cutting unit for cutting the sleeve, and a sleeve dispenser. The mandrel can be suspended within the sleeving device from one or more foil transport rollers or wheels. The foil transport rollers are attached to the sleeving device frame and engage with rollers or wheels attached to the mandrel, and the foil or sleeve is fed between the rollers. Typically, the outer surface of the mandrel has an outer peripheral shape similar to the inner peripheral shape of the foil or sleeve.

[0003] US Patent Application Publication No. 2013 / 0118120(A1) discloses a mandrel suspended within a sleeving device for placing a sleeve around a product, such as a container. In one embodiment, the mandrel is configured to open a foil to form a sleeve, and the mandrel has a substantially cylindrical outer surface around which the foil is fed. The mandrel is suspended in a vertical position. The foil and sleeve are moved downward. According to US Patent Application Publication No. 2013 / 0118120(A1), the cylindrical outer surface of the mandrel is formed by at least two separate mandrel bodies, at least one of which is biased outward to increase the circumference of the outer surface. Using appropriate biasing elements, the circumference of the outer surface is continuously adjusted to accommodate various diameters of the foil during the process without the use of actuators. The biasing elements can include pneumatic or magnetic elements. Similar magnetic poles (repulsion) can be used to create the outwardly biased elements. If the foil perimeter decreases slightly, the outer surface perimeter moves slightly against the outward biasing force and decreases. If the foil perimeter increases, the biasing foil increases the outer surface perimeter.

[0004] The outward bias automatically adjusts the circumference of the mandrel's outer surface to the current inner circumference of the sleeve. As a result, a sleeve having a round cross section can be formed from a flat tubular foil having a flat cross section while avoiding wrinkles or creases in the sleeve. However, because the mandrel in U.S. Patent Application Publication No. 2013 / 0118120(A1) is formed by at least two separate mandrel bodies, the mandrel structure is quite complex and expensive. Summary of the Invention

[0005] There is a general need for a mandrel for expanding a flat tubular foil into a tubular form having a round cross section, which can smoothly open the foil to avoid wrinkles or creases. The foil is made of a heat-shrinkable material that shrinks as its temperature increases. After the foil is expanded by the mandrel, it is cut into individual sleeves by a cutting unit, and the sleeves are placed over a product and firmly attached to the product by increasing the temperature. Therefore, wrinkles or creases in the sleeve can prevent the sleeve from fitting properly to the product, which can lead to a lower quality product.

[0006] It is therefore an object of the present invention, starting from a mandrel such as that disclosed in U.S. Patent Application Publication No. 2013 / 0118120 A1, to provide a mandrel suspended in a sleeving device for expanding a flat tubular foil into a tubular shape with a round cross section, which mandrel can be manufactured at a relatively low cost, avoiding wrinkles or creases in the foil, and which has a simple structure.It is also an object of the present invention to provide a method for expanding a flat tubular foil into a tubular shape with a round cross section, which method can avoid wrinkles or creases in the foil.

[0007] These objects are achieved by the subject matter of independent claims 1 and 17. Advantageous further developments are presented in the dependent claims.

[0008] According to the present invention, a mandrel suspended within a sleeving device for expanding a flat tubular foil into a tubular form having a round cross-section has an expansion section extending along a central axis of the mandrel in the foil feed direction and configured to change the cross-section of the tubular foil from a flat cross-section to a round cross-section. The expansion section comprises a first length configured to change the cross-section of the tubular foil in the foil feed direction from a flat cross-section to a first polygonal cross-section defined by four corners (e.g., a rectangular or square cross-section), and a second length configured to change the cross-section of the tubular foil from the first polygonal cross-section to a second polygonal cross-section defined by eight or more corners (e.g., an octagonal cross-section).

[0009] The term "round cross-section" is not restricted or limited to "circular cross-section," but is intended to encompass "circular cross-section," "substantially circular cross-section," and "nearly circular cross-section." Additionally, the term "polygonal cross-section" is intended to encompass polygonal cross-sections with sharp corners and polygonal cross-sections with rounded or chamfered corners.

[0010] According to the present invention, the mandrel functions to open a flat tubular foil having a flat cross section (in its original state) into a tubular form having a round cross section (in its final state). The term "foil" is used to denote a continuous strip of envelope material from which sleeves are cut after being expanded by the mandrel. Furthermore, the term "flat cross section" refers to the cross section of the foil in its original state before being fed onto the mandrel. The term "round cross section" refers to the final cross section of the foil obtained by being fed onto and along the mandrel (in its final state) before being further processed, for example by being cut by a cutting unit which may be arranged behind the mandrel in the feeding direction of the tubular foil.

[0011] The mandrel according to the present invention has a flaring portion, which comprises a first length configured to change the cross-section of the tubular foil from a flat cross-section to a first polygonal cross-section defined by four corner points. That is, the first length is configured to flaring the tubular foil, deforming or changing the cross-section of the foil from its original flat state to the first polygonal cross-section. The actual structure of the first length may be any structure capable of deforming the cross-section of the foil into a polygonal cross-section defined by four corner points. Specifically, the first length may be any (first) three-dimensional structure (whether its contour is formed from closed or partially open sides) having four distinct corner regions configured to contact the tubular foil, guide the tubular foil in the feed direction, and reform the tubular foil into a tubular shape having the first polygonal cross-section along the entire length of the first length. According to the present invention, the expanding portion comprises a second length configured to transform or change the cross-section of the tubular foil from a first polygonal cross-section to a second polygonal cross-section defined by eight or more corner points. Similar to the first length, the actual structure of the second length may be any structure capable of transforming the cross-section of the foil from a first polygonal cross-section to a second polygonal cross-section defined by eight or more corner points. Specifically, the second length may be any (second) three-dimensional structure (whether its contour is formed from closed or partially open sides) with eight or more distinct corner regions configured to contact the tubular foil, guide the tubular foil in the feed direction, and reform the tubular foil into a tubular shape having the second polygonal cross-section along the entire length of the second length. The terms "transforming" and "reforming" have the same meaning in this application.

[0012] The mandrel of the present invention allows a flat tubular foil to be smoothly expanded into a tubular form having a round cross section by configuring the second length to change the cross section of the tubular foil to a second polygonal cross section defined by eight or more corner points. The second polygonal cross section of the foil defined by eight or more corner points approaches a round cross section. Therefore, the transition from the polygonal cross section defined by eight or more corner points to the round cross section is smooth and easy, wrinkles or creases in the foil are avoided, and the mandrel has a simple structure and can be manufactured at a relatively low cost.

[0013] In a preferred embodiment, the first length is configured to change the cross section of the tubular foil from a flat cross section to a rectangular cross section and then to a square cross section. Because the tubular foil has a square cross section at the end of the first length in the foil feed direction along the central axis of the mandrel, the cross section of the foil can be easily changed to a second polygonal cross section defined by eight or more corner points due to the symmetry of the square cross section.

[0014] The second length may be configured to change the cross section of the tubular foil from the first polygonal cross section to an octagonal cross section, where the octagonal shape closely approximates a round cross section, thereby providing a smooth transition from the octagonal cross section to the round cross section and avoiding wrinkles or creases.

[0015] In a preferred embodiment, the second length is further configured to change the cross-section of the tubular foil from a first octagonal cross-section to a second octagonal cross-section, where the first octagonal cross-section is a scalene octagonal cross-section and the second octagonal cross-section is an equilateral octagonal cross-section. The equilateral octagonal shape is a good compromise between simple shape and approximation to a round shape.

[0016] The expanding portion may comprise a third length following the second length, the third length configured to guide the tubular foil having the second polygonal cross-section along the feed direction without (further) changing the cross-section of the tubular foil. Specifically, the third length may be any (third) three-dimensional structure (whether its contour is formed from closed or partially open sides) having eight or more distinct corner regions configured to contact the tubular foil, guide the tubular foil in the feed direction, and reform the tubular foil into a tubular shape having the second polygonal cross-section along the entire length of the third length.

[0017] In this case, the mandrel may further include an advancement means having at least one drive wheel rotatably mounted inside the third length such that the circumferential surface of the drive wheel is flush with the outer surface of the third length. Because the circumferential surface of the drive wheel is flush with the outer surface of the third length, foil guided between the drive wheel and a servo drive wheel provided outside the mandrel can be fed onto the mandrel without wrinkling or creases in the foil. Specifically, if no foil is provided between the drive wheel and the servo drive wheel, the contact between the drive wheel and the servo drive wheel will be in a straight line.

[0018] In a preferred embodiment, the mandrel may further include a rounding portion configured to change the cross-section of the tubular foil from the second polygonal cross-section to a round cross-section. Thus, the second polygonal cross-section of the foil, which already closely approximates a round cross-section, can be changed into the final round cross-section by the rounding portion. Specifically, the rounding portion may be any three-dimensional structure having a round cross-section (whether its contour is formed from closed or partially open sides) configured to contact the tubular foil, guide the tubular foil in the feed direction, and reform the tubular foil into a round cylindrical shape.

[0019] The mandrel may be configured to change or reshape the cross-section of the tubular foil from a flat cylindrical cross-section to a round cross-section so that the tubular foil has the same circumferential length at any location along the central axis of the mandrel, i.e., without overstretching the tubular foil. The term "overstretching" refers to an increase in the circumferential length of the cross-section of the tubular foil. By keeping the circumferential length of the cross-section of the tubular foil constant along the entire length of the mandrel in the feed direction, wrinkles and creases in the foil can be avoided.

[0020] The mandrel may be configured to change the cross section of the tubular foil from a flat to a round cross section such that, if a first cross section of the foil at any first location along the central axis of the mandrel is divided into a specific number of nodes N1-Nn equidistant from one another along the periphery of the first cross section, and a second cross section of the foil at any second location along the central axis of the mandrel is divided into a specific number of nodes M1-Mn equidistant from one another along the periphery of the second cross section, the distances N1-M1, N2-M2-Nn-Mn on the tubular foil between the identically numbered nodes at the first and second locations are equal, with nodes N1 and M1 lying in a symmetry plane of the mandrel that includes the central axis of the mandrel. This avoids changes in the length of the tubular foil in the feed direction and prevents wrinkles and creases in the foil.

[0021] As outlined above, any polygonal cross section of the tubular foil may have rounded or chamfered corners. The foil is made from a flexible, heat-shrinkable material. Therefore, the corners of the foil may be rounded or chamfered instead of sharp.

[0022] In a preferred embodiment, the cross-section of the flared portion at any location along the central axis is defined by n contact points configured to contact the tubular foil, where n=4 along the first length and n≧8 along the second length, such that a polygonal chain of straight line segments connecting the n contact points defines a polygonal cross-section of the tubular foil. Thus, the n=4 contact points along the first length are provided to create a first polygonal cross-section of the tubular foil defined by four corner points, and the n≧8 contact points along the second length are provided to create a second polygonal cross-section of the tubular foil defined by eight or more corner points.

[0023] In this case, the flared portion may be formed by a wedge-shaped structure, with the first length portion and the second length portion each defined by a trapezoidal side surface tapering in the feeding direction of the tubular foil, and the n contact points being on the side edges of the trapezoidal side surface. Thus, the flared portion can be formed by an element having a surface with a relatively simple shape.

[0024] In particular, the trapezoidal sides may be connected by triangular sides, thus providing a mandrel having a circumferentially closed hollow structure and formed by elements having a simple geometric shape.

[0025] As outlined above, the expanding portion may have a three-dimensional shape defined by closed or partially open sides in the first length and / or the second length, the side edges of the sides being arranged to define distinct corner areas that are configured to correspond to corresponding corner points of the first and second polygonal cross sections of the tubular foil, respectively, while the tubular foil is fed along the first and second lengths.

[0026] In a preferred embodiment, the flared portion comprises a tip portion upstream of the first length configured to receive and guide the flat tubular foil into the first length.

[0027] There may also be provided an apparatus for forming creases in a flat tubular foil, the device comprising: a first mandrel according to any one of the above aspects; and a second mandrel according to any one of the above aspects, wherein the first mandrel and the second mandrel are arranged such that a central axis of the first mandrel and a central axis of the second mandrel coincide with each other and a tip portion of the first mandrel and a tip portion of the second mandrel are arranged facing away from each other; and the second mandrel is rotatable about the central axis of the first mandrel relative to the first mandrel such that a first length portion and a second length portion of the first mandrel do not coincide with a first length portion and a second length portion of the second mandrel.

[0028] Thus, in the above-described device, the first and second mandrels are on the same central axis, but the second mandrel is rotated approximately 180° relative to the first mandrel. That is, the device is configured so that the foil having a second polygonal cross-section leaving the first mandrel is first fed onto the second length of the second mandrel, then onto the first length of the second mandrel, and leaves the second mandrel having a flat tubular cross-section. Because the second mandrel is rotatable relative to the first mandrel, the orientation of the foil fed onto the first mandrel differs from the orientation of the foil leaving the second mandrel. By changing the orientation of the foil using the device, two additional folds can be created in the foil at the edge of the flat tubular foil leaving the second mandrel. Thus, the device can produce a foil with a total of four folds because the flat tubular foil fed onto the first mandrel already has two folds (factory folds) at the edge of the flat tubular foil extending along the foil in the feeding direction. Therefore, after the foil is cut into individual sleeves by the cutting device, the sleeves can be placed on a product having a rectangular or square cross section and shrunk. The distance between the additional folds produced by the device in the circumferential direction of the foil depends on the rotation angle of the first mandrel relative to the second mandrel. By using two mandrels according to any one of the above embodiments, foils made with four folds can be produced while avoiding wrinkles or creases.

[0029] According to a further aspect, there is provided a sleeving device for placing a sleeve around a container, the sleeving device comprising: a frame; a foil supply unit attached to the frame, the foil supply unit configured to supply a tubular foil to a mandrel according to any one of the above aspects suspended from the frame; a cutting unit for cutting the tubular foil to form a sleeve; and a sleeve dispenser.

[0030] According to the present invention, there is provided a method for expanding a flat tubular foil into a tubular form having a round cross-section, comprising feeding the tubular foil in a feed direction to change the cross-section of the tubular foil from a flat cross-section to a round cross-section, the method comprising the following steps: a first step of changing the cross-section of the tubular foil from a flat cross-section to a first polygonal cross-section defined by four corner points; and a second step of changing the cross-section of the tubular foil from the first polygonal cross-section to a second polygonal cross-section defined by eight or more corner points.

[0031] According to the method, in a first step, the cross section of the tubular foil is changed from a flat cross section to a first polygonal cross section defined by four corner points. Then, in a second step, the cross section of the tubular foil is changed from the first polygonal cross section to a second polygonal cross section defined by eight or more corner points. Thus, according to the method, after the second step, the cross section of the tubular foil has a second polygonal cross section defined by eight or more corner points. The second polygonal cross section of the foil defined by eight or more corner points is sufficiently close to a round cross section. Therefore, the transition from the polygonal cross section defined by eight or more corner points to the round cross section can be made smoothly and easily, and wrinkles or creases in the foil can be avoided.

[0032] According to a preferred embodiment, in a first step, the cross section of the tubular foil is changed from a flat cross section to a rectangular cross section and then to a square cross section. Because the tubular foil has a square cross section at the end of the first step, the cross section of the foil can be easily changed to a second polygonal cross section defined by eight or more corner points due to the symmetrical shape of the square cross section.

[0033] In a second step, the cross section of the tubular foil may be changed from the first polygonal cross section to an octagonal cross section. The octagonal shape approaches a round cross section. Therefore, the transition from the octagonal cross section to the round cross section can be made smoothly, and wrinkles or creases can be avoided.

[0034] In a preferred embodiment, in the second step, the cross section of the tubular foil is changed from a first octagonal cross section to a second octagonal cross section, where the first octagonal cross section is a scalene octagonal cross section and the second octagonal cross section is an equilateral octagonal cross section. The equilateral octagonal shape is a good compromise between a simple shape and an approximation to a round shape.

[0035] The method may further comprise a third step of guiding the tubular foil having the second polygonal cross section along the feeding direction.

[0036] In a preferred embodiment, the method further comprises a rolling step in which the cross section of the tubular foil is changed from the second polygonal cross section to a round cross section, so that the second polygonal cross section of the foil, which is already a good approximation of a round cross section, can be changed into the final round cross section in the rolling step.

[0037] The cross section of the tubular foil may be varied from a flat to a round cross section such that the circumferential length of the tubular foil remains constant. By keeping the circumferential length of the tubular foil constant, wrinkles and creases in the foil can be avoided.

[0038] In a preferred embodiment, if a first cross section of the tubular foil at any first position along the feeding direction of the tubular foil is divided into a specific number of nodes N1-Nn equidistant from one another along the periphery of the first cross section, and a second cross section of the tubular foil at any second position along the feeding direction is divided into a specific number of nodes M1-Mn equidistant from one another along the periphery of the second cross section, the cross section of the tubular foil is transformed from a flat cross section to a round cross section so that the distances N1-M1, N2-M2-Nn-Mn on the tubular foil between the identically numbered nodes at the first and second positions are equal, and the nodes N1 and M1 are located on a symmetry plane of the tubular foil that includes the central axis of the tubular foil. This prevents wrinkles and creases in the foil.

[0039] In a preferred embodiment, any polygonal cross section of the tubular foil has rounded or chamfered corners, so that the corners of the foil may be rounded or chamfered instead of sharp. [Brief explanation of the drawings]

[0040] With the aid of the accompanying figures, embodiments of the invention are explained in more detail below. [Figure 1] 1 shows a perspective view of a mandrel according to a first embodiment of the present invention; [Figure 2] 1 shows a perspective view of a flared portion of a mandrel according to a first embodiment of the present invention. [Figure 3] 3 shows a front cross-sectional view along the central axis of the expanded portion of FIG. 2 and a bottom view of the expanded portion of FIG. 2. [Figure 4a] 1A-1C show perspective views of the flared portion of the mandrel according to a first embodiment of the invention, showing different cross sections. [Figure 4b] 4b shows a front view of the expanded portion of FIG. 4a. [Figure 4c] 4b shows a side view of the flared portion of FIG. 4a. [Figure 4d] 1 shows the periphery of the tubular foil at a first position and a second position along the central axis of the tubular foil. [Figure 5a] 1 shows a perspective view of a flared portion of a mandrel according to a first embodiment of the invention, illustrating the distance between corresponding nodes in the feeding direction of the mandrel according to the first embodiment. [Figure 5b] 5b shows a front view of the expanded portion of FIG. 5a. [Figure 5c] 5b shows a side view of the flared portion of FIG. 5a. [Figure 5d] The distance between corresponding nodes on the periphery of a first cross section of the tubular foil and corresponding nodes on the periphery of a second cross section of the tubular foil is shown. [Figure 6] 1 shows a perspective view of a mandrel according to a first embodiment, disclosing a drive wheel mounted inside a third length of the mandrel. [Figure 6a] 6. An enlarged portion A of FIG. 6 is shown. [Figure 6b] An enlarged portion B of FIG. 6a is shown. [Figure 7] 3 shows a mandrel according to a second embodiment of the present invention. [Figure 8a] Shows a flared section with rounded corners. [Figure 8b] An enlarged portion A of FIG. 8a is shown. [Figure 9a] 1 shows a truncated flared section with chamfered corners. [Figure 9b] An enlarged portion A of FIG. 9a is shown. [Figure 10] 1 shows a device for forming folds in a flat tubular foil. [Figure 11] 1 shows a mandrel having a beveled tip portion.

[0041] These drawings are not intended to be limiting in any way, and it is contemplated that various embodiments of the invention may be embodied in a variety of other ways, including those not necessarily shown in the drawings. The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the invention and, together with the description, serve to explain the principles of the invention. It should be understood, however, that the invention is not limited to the precise arrangements shown. DETAILED DESCRIPTION OF THE INVENTION

[0042] The following description of embodiments of the present invention should not be used to limit the scope of the present invention. Other examples, features, aspects, embodiments, and advantages of the present invention will become apparent to those skilled in the art from the following description, which is, by way of example, one of the best modes contemplated for carrying out the invention. As will be understood, the present invention is capable of other, different, and obvious aspects without departing from the present invention. Accordingly, the drawings and the specification should be regarded as illustrative in nature and not restrictive. Various suitable ways in which the teachings herein can be combined will be readily apparent to those skilled in the art in light of the teachings herein. Such modifications and variations are intended to be within the scope of the claims.

[0043] First embodiment 1 to 6b show different (schematic) views of the mandrel 1 and the flared portion 14 of the mandrel 1 according to a first embodiment of the invention. Note that for better understanding, not all the views show all elements of the mandrel 1 or of the sleeving device 3 from which the mandrel 1 is suspended.

[0044] FIG. 1 shows a mandrel 1 for expanding a flat tubular foil into a tubular form with a round cross section, the mandrel 1 being suspended within a sleeving device 3. The sleeving device 3 includes conveying rollers 5 engaging with wheels 7 rotatably mounted on both sides of the mandrel 1. The conveying rollers 5 are connected to a drive for driving the conveying rollers 5. The foil (not shown) is supplied from a reservoir, such as a roll. The foil is provided as a flat continuous film consisting of two plastic layers connected at the corners and folded over. Thus, the foil, which has a flat cross section and two folds (factory folds) at the corners of the foil extending along the foil feed direction, is fed over the mandrel 1 from top to bottom in FIG. 1 between the conveying rollers 5 and the wheels 7.

[0045] The mandrel 1 comprises, in the feeding direction of the tubular foil, a tip portion 10 and a flared portion 14 having a first length 20, a second length 30 and a third length 40. The tip portion 10 serves to open the flat tubular foil and guide the foil towards the flared portion 14.

[0046] 2-4c show the diverging section 14 of the mandrel 1 in more detail. The diverging section 14 includes a first length 20 configured to change the cross section of the tubular foil from the flat cross section 12 to a rectangular cross section 22, which is a first polygonal cross section defined by four corner points 22a-22d. That is, the first length 20 diverges the tubular foil to have the rectangular cross section 22. The first length 20 is formed by a wedge-shaped structure and includes trapezoidal sides 24 tapering in the foil feeding direction, which are connected by triangular sides 25. The foil contacts the first length 20 at the corner points 22a-22d, which serve as contact points. However, the foil may also be supported via the trapezoidal sides 24 and the triangular sides 25. At the end of the first length 20 in the foil feeding direction, the foil has a square cross section 26.

[0047] The flaring section 14 further includes a second length 30 configured to change the cross-section of the tubular foil from the square cross-section 26 to a first octagonal cross-section, which is a second polygonal cross-section defined by eight corner points 32a-32h. Similar to the first length 20, the second length 30 includes trapezoidal sides 34 that taper in the foil feed direction and are connected by triangular sides 35. The foil contacts the second length 30 at corner points 32a-32h, which serve as contact points. The first octagonal cross-section is a scalene octagonal cross-section 32. At the end of the second length 30 in the foil feed direction, the foil has a second octagonal cross-section, which is an equilateral octagonal cross-section 36.

[0048] The flaring portion 14 further comprises a third length 40 following the second length 30, which is configured to guide the tubular foil having an equilateral octagonal cross section 36 along the foil feed direction. In the third length 40, the equilateral octagonal cross section 36 does not change and therefore remains constant.

[0049] Thus, the mandrel 1 has a circumferentially closed hollow structure. That is, the mandrel 1 has an outline formed by closed sides formed by elements with simple geometric shapes. Furthermore, the mandrel 1 is configured so that the circumferential length of the tubular foil cross section remains constant along the central axis 2. That is, the circumferential length of the flat cross section 12, the circumferential length of the rectangular cross section 22, the circumferential length of the square cross section 26, the circumferential length of the scalene octagonal cross section 32, and the circumferential length of the equilateral octagonal cross section 36 are the same. By keeping the circumferential length of the tubular foil cross section constant along the entire length of the mandrel 1 in the feed direction, wrinkles and creases in the foil can be avoided. Figure 4d schematically illustrates the periphery of the tubular foil at an arbitrary first position and an arbitrary second position along the central axis of the tubular foil. The circumferential length of the cross section at the first position is equal to the circumferential length of the cross section at the second position.

[0050] Similar to FIG. 4d, FIG. 5d schematically illustrates the periphery / cross-section of the tubular foil at an arbitrary first location and an arbitrary second location along the central axis of the tubular foil corresponding to the central axis 2 of the mandrel 1. The first cross-section of the tubular foil at the first location along the central axis 2 of the mandrel 1 is divided into a specific number of nodes N1-Nn located equidistant from one another along the periphery of the first cross-section. The second cross-section of the tubular foil at a second location along the central axis 2 of the mandrel 1 is divided into a specific number of nodes M1-Mn located equidistant from one another along the periphery of the second cross-section. The distances N1-M1, N2-M2-Nn-Mn on the tubular foil between identically numbered nodes at the first and second locations are equal, and nodes N1 and M1 lie in a symmetry plane of the mandrel 1 (not shown in FIG. 5d) that contains the central axis 2 of the mandrel 1. For convenience, nodes N1-Nn are provided only on a portion of the circumference of the first cross section at the first position, and nodes M1-Mn are provided only on a portion of the circumference of the second cross section at the second position. Figures 5a-5c show the distances N1-M1, N2-M2 to Nn-Mn, respectively, on the expanded portion 14 of the mandrel 1. By keeping the distances N1-M1 and N2-M2 to Nn-Mn equal, wrinkles or creases in the tubular foil can be avoided.

[0051] 3 shows a front cross-sectional view along the central axis 2 of the flared portion of FIG. 2 and a bottom view of the flared portion of FIG. 2. From a mechanical point of view, the height of the transition from the flat section 12 having the lay flat width LFW to the equilateral octagonal section 36 is a vertical height H 20 and vertical height H 30 and is preferably as small as possible to minimize the required operating space. The transition H occurs when the angle α between the central axis 2 and the triangular side 25 of the first length 20 is the same as the angle β between the central axis 2 and the trapezoidal side 34 of the second length 30. 20 +H 30 Experiments have shown that it is possible to determine an appropriate height for the angle α=β. In the illustrated embodiment, the angle α=β is 12°.

[0052] FIG. 6 shows the mandrel 1 according to the first embodiment, which is shown upside down. That is, in FIG. 6, the foil feed direction is from bottom to top. The mandrel 1 of FIG. 6 includes a rounding section 50 (not shown in FIG. 1) configured to change the cross section of the tubular foil from the equilateral octagonal cross section 36 to a round cross section. Furthermore, FIGS. 6-6b each show two drive wheels 9 rotatably mounted inside the third length 40 such that the circumferential surface of each drive wheel 9 is flush with the outer surface 37 of the third length 40. Because the circumferential surface of each drive wheel 9 is flush with the outer surface 37 of the third length 40, the foil guided between each drive wheel 9 and the servo drive wheel 8 provided outside the mandrel 1 can be fed onto the mandrel 1 without wrinkling or creases in the foil. Specifically, as shown in the enlarged view B of FIG. 6b, if no foil is provided between the drive wheel 9 and the servo drive wheel 8, the contact between the drive wheel 9 and the servo drive wheel 8 will be in a straight line.

[0053] Second embodiment FIG. 7 shows a mandrel 100 according to a second embodiment of the invention. In contrast to the mandrel 1 of the first embodiment, the mandrel 100 does not have a third length 40. That is, at the end of the second length 30 in the foil feed direction along the central axis of the mandrel 100, the foil has an equilateral octagonal cross section 36, which then changes to a rounded cross section by a rounding section 50. Furthermore, transport rollers 5 for suspending the mandrel 100 are provided outside the mandrel 100 in the region of the rounding section 50. In contrast, in the first embodiment as shown in FIG. 1, the transport rollers 5 are provided in the region of the first length 20.

[0054] Additionally, the first length 20 of the flared portion 14 of the mandrel 100 according to the second embodiment has a profile formed by partially open sides. That is, the first length 20 has trapezoidal sides 24 that taper in the feeding direction of the tubular foil. However, the trapezoidal sides 24 are not connected by triangular sides. This allows the weight of the mandrel 100 to be reduced. For this purpose, the mandrel 100 further includes openings 102, as shown in FIG. 7.

[0055] Further Applications and Modifications In the first embodiment, as shown in the schematic diagrams of Figures 2 and 4a-5a, the corners between the trapezoidal and triangular faces are sharp. However, as shown in Figures 8a and 8b, the corners between the trapezoidal and triangular sides 24 and 25 may alternatively be rounded instead of sharp. Of course, the corners in the second and third lengths 30 and 40 may also be rounded instead of sharp.

[0056] Alternatively, as shown in Figures 9a and 9b, the corners on first length 20, second length 30, and third length 40 may be chamfered instead of being sharp or rounded.

[0057] 10 shows a device 200 for forming folds in a flat tubular foil, comprising a first mandrel 1 according to the first embodiment and a second mandrel 1 according to the first embodiment, the first mandrel 1 and the second mandrel 1 being arranged one after the other such that the central axes of the first mandrel 1 and the second mandrel 1 coincide with each other. However, the second mandrel 1 is rotated by approximately 180° relative to the first mandrel 1. That is, the device 200 is configured such that the rounded portion 50 of the first mandrel 1 and the rounded portion 50 of the second mandrel 1 are connected. Additionally, the second mandrel 1 is rotated about its central axis relative to the first mandrel 1 so that the orientation of the foil fed onto the first mandrel 1 differs from the orientation of the foil leaving the second mandrel 1, i.e., so that the first and second lengths 20 and 30 of the first mandrel 1 do not coincide with the first and second lengths 20 and 30 of the second mandrel 1. By changing the orientation of the foil by the device 200, two additional folds can be created in the foil at the edge of the flat tubular foil leaving the second mandrel 1. Thus, because the flat tubular foil fed onto the first mandrel 1 already has two folds (factory folds) at the edge of the flat tubular foil extending along the foil in the feeding direction, the device 200 can create a foil with a total of four folds. The distance of the additional folds made by the device 200 from one another in the circumferential direction of the foil depends on the angle of rotation of the first mandrel 1 relative to the second mandrel 1 about the central axis. By using two mandrels 1 according to the first embodiment, foils made with four folds can be produced while avoiding wrinkles or creases. Note that Figure 10 does not disclose the tip portions 10 of the first and second mandrels 1.

[0058] FIG. 11 shows a modified mandrel for opening pre-cut sleeves, with a beveled tip portion 10 to prevent clogging.

[0059] In the first embodiment shown in Figure 3, the angle α = β is 12°. However, the angle α = β may be in the range of 5° to 25°, preferably in the range of 12° to 15°. However, alternatively, the angles α = β may be different from each other.

[0060] In the first embodiment, the first length 20, second length 30, and third length 40 are each three-dimensional structures contoured from closed sides (trapezoidal, triangular, and rectangular sides). However, alternatively, the three-dimensional structures may have contours formed from partially open sides, as in the second embodiment.

[0061] The first length 20 of the mandrel 100 according to the second embodiment has a profile formed from partially open sides. Alternatively, the first length 20 of the second embodiment may be formed from closed sides, as in the first embodiment. [Explanation of symbols]

[0062] 1 mandrel 2 Center axis 3 Sleeving Device 5 Conveyor roller 7 Wheels 8 servo-driven wheels 9 Drive Wheels 10 Tip part 12 Flat cross section 14 Expanded part 20 First Length 22 Rectangular cross section 22a~22d corner point 24 Trapezoidal Side 25 triangular side 26 square cross section 30 Second Length 32 Scalene octagonal cross section 32a~32h corner point 34 Trapezoidal Side 35 triangular side 36 Equilateral octagonal cross section 37 Exterior 40 Third Length 50 rounded part 100 mandrels 102 Opening 200 devices H 20 Vertical height of the first length H 30 Vertical height of the second length LFW Flat width

Claims

1. A mandrel (1; 100) suspended in a sleeving device (3) for expanding a flat tubular foil into a tubular form having a round cross section, the mandrel (1; 100) having an expanding portion (14) extending along a central axis (2) of the mandrel (1; 100) in the direction of feeding of the foil and configured to change the cross section of the tubular foil from a flat cross section (12) to a round cross section, The diverging portion (14) comprises a first length (20) configured to change the cross section of the tubular foil from the flat cross section (12) to a first polygonal cross section defined by four corner points (22a-22d) in the feeding direction of the tubular foil, and a second length (30) configured to change the cross section of the tubular foil from the first polygonal cross section to a second polygonal cross section defined by eight or more corner points (32a-32h). A mandrel (1;100).

2. 2. The mandrel (1; 100) of claim 1, wherein the first length (20) is configured to change the cross section of the tubular foil from the flat cross section (12) to a rectangular cross section (22) and then to a square cross section (26).

3. 3. The mandrel (1; 100) of claim 1 or 2, wherein the second length (30) is configured to change the cross section of the tubular foil from the first polygonal cross section to an octagonal cross section.

4. The mandrel (1;100) of any one of claims 1 to 3, wherein the second length portion (30) is further configured to change the cross-section of the tubular foil from a first octagonal cross-section to a second octagonal cross-section, the first octagonal cross-section being a scalene octagonal cross-section (32) and the second octagonal cross-section being an equilateral octagonal cross-section (36).

5. 5. The mandrel (1) according to claim 1, wherein the flaring portion (14) comprises a third length portion (40) following the second length portion (30), the third length portion (40) being configured to guide the tubular foil having the second polygonal cross section along the feeding direction.

6. 6. The mandrel (1) according to claim 5, further comprising advancing means having at least one drive wheel (9), said at least one drive wheel rotatably mounted inside said third length (40) such that the circumferential surface of said drive wheel (9) is flush with the outer surface (37) of said third length (40).

7. The mandrel (1; 100) according to any one of claims 1 to 6, further comprising a rounding portion (50) configured to change the cross section of the tubular foil from the second polygonal cross section to a round cross section.

8. 8. The mandrel (1; 100) according to any one of claims 1 to 7, wherein the mandrel (1; 100) is configured to change the cross section of the tubular foil from the flat cross section (12) to the round cross section so that the tubular foil has the same circumferential length at any position along the central axis (2) of the mandrel (1; 100).

9. When a first cross section of the tubular foil at any first position along the central axis of the mandrel is divided into a specific number of nodes N1 to Nn that are equidistant from one another along the periphery of the first cross section, and a second cross section of the tubular foil at any second position along the central axis of the mandrel is divided into the specific number of nodes M1 to Mn that are equidistant from one another along the periphery of the second cross section, 9. The mandrel (1;100) according to any one of claims 1 to 8, wherein the mandrel (1;100) is configured to change the cross section of the tubular foil from the flat cross section (12) to the round cross section such that the distances on the tubular foil between newly numbered nodes N1-M1, N2-M2 to Nn-Mn are equal, and the nodes N1 and M1 lie in a symmetry plane of the mandrel which contains the central axis (2) of the mandrel (1;100).

10. A mandrel (1; 100) according to any one of claims 1 to 9, wherein any polygonal cross section of the tubular foil has rounded or chamfered corners.

11. 11. The mandrel (1;100) according to any one of claims 1 to 10, wherein the cross-section of the flared portion (14) at any position along the central axis (2) is defined by n contact points configured to contact the tubular foil, where n=4 along the first length (20) and n≧8 along the second length (30), whereby a polygonal chain of straight line segments connecting the n contact points defines a polygonal cross-section of the tubular foil.

12. 12. The mandrel (1; 100) of claim 11, wherein the flared portion (14) is formed by a wedge-shaped structure, the first length portion (20) and the second length portion (30) are each defined by trapezoidal sides (24, 34) tapering in the feeding direction of the tubular foil, and the n contact points are on the side edges of the trapezoidal sides (24, 34).

13. 13. The mandrel (1) according to claim 12, wherein the trapezoidal sides (24) are connected by triangular sides (25).

14. The mandrel (1; 100) according to any one of claims 1 to 13, wherein the diverging portion (14) comprises a tip portion (10) upstream of the first length portion (20) configured to receive the flat tubular foil and guide it into the first length portion (20).

15. A device (200) for forming folds in a flat tubular foil, comprising a first mandrel (1; 100) according to any one of claims 1 to 13 and a second mandrel (1; 100) according to any one of claims 1 to 13, wherein the central axis (2) of the first mandrel (1; 100) and the central axis (2) of the second mandrel (1; 100) are coincident with each other and the tip portion (10) of the first mandrel (1; 100) and the tip portion (10) of the second mandrel (1; 100) are oriented opposite to each other. The first mandrel (1; 100) and the second mandrel (1; 100) are arranged so that the first length portion (20) and the second length portion (30) of the first mandrel (1; 100) do not coincide with the first length portion (20) and the second length portion (30) of the second mandrel (1; 100).

16. A sleeving device (3) for placing a sleeve around a container, the sleeving device (3) comprising: a frame; a foil supply unit attached to the frame, the foil supply unit configured to supply a tubular foil to a mandrel (1; 100) according to any one of claims 1 to 15 suspended from the frame; a cutting unit for cutting the tubular foil to form a sleeve; and a sleeve dispenser.

17. A method for expanding a flat tubular foil into a tubular form having a round cross section, the method comprising feeding the tubular foil in a feeding direction to change the cross section of the tubular foil from a flat cross section (12) to a round cross section, the method comprising: a first step of changing the cross section of the tubular foil from the flat cross section (12) to a first polygonal cross section defined by four corner points (22a-22d); a second step of changing the cross section of the tubular foil from the first polygonal cross section to a second polygonal cross section defined by eight or more corner points (32a-32h); A method comprising:

18. 18. The method of claim 17, wherein in the first step, the cross section of the tubular foil is changed from the flat cross section (12) to a rectangular cross section (22) and then to a square cross section (26).

19. 19. The method according to claim 17 or 18, wherein in the second step, the cross section of the tubular foil is changed from the first polygonal cross section to an octagonal cross section.

20. 20. The method according to any one of claims 17 to 19, wherein in the second step, the cross section of the tubular foil is changed from a first octagonal cross section to a second octagonal cross section, the first octagonal cross section being a scalene octagonal cross section (32) and the second octagonal cross section being an equilateral octagonal cross section (36).

21. 21. The method according to claim 19 or 20, further comprising a third step of guiding the tubular foil having the second polygonal cross section along the feeding direction.

22. 22. The method of any one of claims 17 to 21, further comprising a rounding step of changing the cross-section of the tubular foil from the second polygonal cross-section to a round cross-section.

23. 23. The method according to any one of claims 17 to 22, wherein the cross-section of the tubular foil is changed from the flat cross-section (12) to the round cross-section such that the circumferential length of the cross-section of the tubular foil remains constant.

24. 24. The method of claim 17, wherein a first cross-section of the tubular foil at any first position along the feeding direction of the tubular foil is divided into a certain number of nodes N1 to Nn equidistant from one another along the periphery of the first cross-section, and a second cross-section of the tubular foil at any second position along the feeding direction is divided into the certain number of nodes M1 to Mn equidistant from one another along the periphery of the second cross-section, and the cross-section of the tubular foil is changed from the flat cross-section (12) to the round cross-section such that distances N1-M1, N2-M2 to Nn-Mn on the tubular foil between identically numbered nodes at the first and second positions are equal, and node N1 and node M1 lie in a plane of symmetry of the tubular foil containing the central axis (2) of the tubular foil.

25. 25. The method according to any one of claims 17 to 24, wherein any polygonal cross section of the tubular foil has rounded or chamfered corners.

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