METHOD AND DEVICE FOR FOLDING

Description

[0001] The invention relates to a method for the continuous folding of locking elements of matching plastic closures attached to the upper edge of a tamper-evident band, wherein the tamper-evident band is arranged on the cylindrical closure cap of each plastic closure. The connection is made by injection molding via webs forming hinged joints. The invention also relates to a folding device for the continuous folding of such plastic closures. The folding is achieved by pivoting the locking elements inwards.

[0002] In this patent application, the terms "top edge" or "upper rim" are understood to refer to the bottom of a plastic closure cap as the lowest reference point.

[0003] Plastic closures with a tamper-evident band are also known as tamper-evident closures. The tamper-evident function of such closures is that, upon first removal of the cap, a tamper-evident band is at least partially torn. The tamper-evident band is usually connected to the upper edge of the cylindrical cap of each plastic closure by thin tabs. Locking elements attached to the upper edge of the tamper-evident band engage with a container, such as a bottle neck, via a raised ridge. The tamper-evident band is thus fixed to the bottle neck and tears at least partially when the plastic closure is first opened. The design of the locking elements of the tamper-evident band has a significant influence on the effectiveness of the tamper-evident function.

[0004] The retention function of the warranty band is fulfilled by the locking elements, which are directed inwards into the cap. However, a plastic closure with such a warranty band can only be injection-molded in such a way that the locking elements are not yet directed into the cap, but rather point upwards as an extension of the warranty band.

[0005] After injection molding, the locking elements must therefore be folded diagonally inwards towards the bottom of the cap in a further step.

[0006] Folding machines are used for this purpose. These machines essentially consist of a circular conveyor that receives the plastic closures and a press cylinder positioned above each closure. The press cylinder, through a lifting motion, engages the locking elements and folds them inwards. During this process, the press cylinder plunges into the closure cap of the plastic closure. These folding machines require precise centering of each plastic closure relative to the press cylinder, which is positioned vertically above it and aligned with the cavity of the closure cap. Such folding machines are described, for example, in EP 1 243 520 A1 and WO 2010 / 046858 A2.

[0007] US Patent 4,613,052 A discloses a plastic closure with a circumferential inner band attached to the top edge of the warranty band, which, after injection molding, must be folded inwards in a second step. For this purpose, a folding wheel is pressed against the inner band. By rotating the plastic closure in a controlled manner around its vertical axis, the inner band is guided past the folding wheel and, after one rotation, is completely folded inwards.

[0008] The throughput rate of known folding devices is limited because the folding tool, whether a press die or a folding wheel, must be precisely aligned with each individual cap or plastic closure. If precise alignment is sacrificed in favor of higher throughput rates, this impairs the accuracy of the folding process, which can lead to quality problems with the plastic closures. Furthermore, known folding devices incur high costs due to the high tooling costs and the slow operating speed.

[0009] From DE 93 09 067 U1, a device for folding back the retaining elements of a cap warranty band is known. The device comprises a folding tool, e.g., a folding roller with a bending layer made of elastic material. A pressure element is arranged approximately parallel to the axis of the folding roller, the distance of which to the folding roller is less than the height of the cap. The bending layer of the folding tool has a working surface which, at its narrowest point, is at least as wide as the diameter of the warranty band to be processed. This working surface is pressed against the end face of the warranty band to fold back the retaining elements. Since the bending layer is made of elastic material, the working surface is elastically deformed by the pressure force. It is partially pressed into the cap and simultaneously bends the retaining elements inwards beyond the horizontal position.The optimal hardness of the bending layer depends on the folding properties of the retaining elements. To ensure that the working surface of the bending layer returns to its original shape after the folding process, the bending layer must be made of an elastic material.

[0010] Based on this prior art, the invention aims to create a method and a folding device that allows reliable folding of the locking elements of a plastic closure of the type mentioned above at high speed, and which in particular does not require precise alignment of each individual plastic closure with the folding tool.

[0011] This problem is solved by a method having the features of claim 1 and a folding device having the features of claim 7.

[0012] Surprisingly, it was found that in the plastic closures described above, the locking elements can be folded quickly and reliably by applying even pressure to the upward-facing upper edges of the locking elements of the unfolded plastic closure. The folding process is aided if the upward-facing locking elements are already slightly tilted inwards towards the vertical axis of the plastic closure by the injection molding process before folding.

[0013] Each plastic closure is continuously positioned between a pressure surface interacting with the upper edge of the locking elements and a guide surface within a folding area. Placement in the folding area is preferably achieved using a continuous conveyor.

[0014] The printing surface and the guide surface are arranged in the folding area in such a way that the upper edge of the guarantee band of each plastic closure temporarily rests against the printing surface, in particular in a ring-like manner, after the folding process.

[0015] To prevent the locking elements from interlocking with the pressure surface as the plastic closures pass through the folding area, the pressure surface is rigid, i.e., non-elastic. In technical terms, the pressure surface behaves almost like a rigid body with a non-flexible surface that does not deform under the expected loads.

[0016] The printing surface is preferably an integral part of a component. For a preferred folding device for carrying out the method, the component is a circular plate.

[0017] The printing surface preferably consists of a hard, especially metallic, material. The metallic materials can be ferrous materials, non-ferrous metals (NF metals), such as alloys based on copper and aluminum, or hard metals.

[0018] The hardness of the printing surface is greater than that of the plastic closures and has a Rockwell hardness of ≥ 50 HRC. This greater hardness has a beneficial effect on the wear behavior of the printing surface, which interacts with the locking elements of the plastic closures. Furthermore, the hardness prevents the locking elements from interlocking with the printing surface, allowing them to slide on it during the folding process. The coefficient of sliding friction (µGR) between the printing surface material and the plastic closure material is µGR ≤ 0.50, preferably µGR ≤ 0.35.

[0019] The Rockwell hardness test determines the hardness value (HRC) of a material by pressing an indenter into the material being tested with a predefined force. Rockwell hardness testing for metallic materials is performed according to EN ISO 6508-1:2016.

[0020] The coefficient of friction is determined according to DIN EN ISO 8295:2004. In standard tribological tests of plastic friction pairs, a block-shaped sample A (upper sample) is pressed onto the plate-shaped sample B (lower sample) with a defined normal force and moved back and forth in a linear oscillation on the latter. The coefficient of sliding friction is recorded over the duration of the test.

[0021] The distance (H), i.e., the minimum distance between the printing surface and the guide surface in the folding area, is equal to or slightly less than the height (h) of the plastic closure cap and the tamper-evident band. Slightly less means that the distance is at most 3% less than the height (h). The distance (H) ensures that the upper edge of the tamper-evident band of each plastic closure temporarily, at least partially, rests against the printing surface after the locking elements are folded.

[0022] The folding device for carrying out the method according to the invention requires only a drive with a drive shaft rotatable about a pivot axis, configured to rotate the pocket wheel, the guide plate, and the pressure plate in the same direction and at the same angular velocity. By means of the pocket wheel, each plastic closure is continuously moved from the inlet area into the folding area.

[0023] The drive mechanism also actuates the folding tool, which in the folding device is formed by the guide plate and the pressure plate. The guide plate has an annular guide surface lying in the plane of the plate, and the pressure plate has an annular pressure surface that is beveled relative to the plane of the plate and faces the guide surface. The beveled, annular pressure surface can be created by chamfering or bending the edge of the pressure plate. In the folding area, the guide surface interacts with the upper edge of the locking element of each plastic closure to be folded, which rests on the annular guide surface as a counter-bearing with its cap base.

[0024] A compensating coupling, e.g. a spring disc coupling or a cardan joint, between the drive shaft of the common drive and the pressure plate compensates for an angular misalignment (α) between the axis of rotation of the drive shaft and the axis of rotation of the pressure plate.

[0025] The universal joint compensates for the angular misalignment (α) between the axis of rotation of the drive shaft and the axis of rotation of the shaft connected to the pressure plate. The two shafts together form a universal joint, which enables torque transmission to the pressure plate via a shaft section bent at the angle (α). Torque transmission from the shaft to the pressure plate preferably occurs via a positive-locking shaft-hub connection, in particular a splined shaft. Alternatively, transmission via a splined shaft or keyway is possible. This preferred shaft-hub connection allows axial movement of the pressure plate along its axis of rotation, thereby preventing excessive constraints imposed by the pressure plate's guide elements.

[0026] The two axes of rotation with angular offset (α) lie in a plane that intersects the guide surface and the pressure surface in the folding area. The line of intersection between the plane and the guide surface and the line of intersection between the plane and the pressure surface are parallel to each other if the angular offset (α) between the axis of rotation of the drive shaft and the axis of rotation of the pressure plate corresponds to the angle (α) of the chamfered, annular pressure surface relative to the plane of the plate.

[0027] Guide means cause the pressure plate to rotate about its axis of rotation with a constant angular offset (α) to the axis of rotation of the drive shaft, wherein the axis of rotation is fixed in space.

[0028] In the case of a cardan shaft as a compensating coupling, the shaft connected to the pressure plate and the drive shaft can be mounted in a frame-fixed manner in order to fix the angular offset (α) (kink angle) of the cardan shaft in space.

[0029] In a preferred embodiment of the invention, the guide means comprise at least three guide rollers rotatably mounted on a frame, resting on the upper surface of the pressure plate. The guide rollers are independently height-adjustable to effect rotation of the pressure plate about its fixed axis of rotation with an angular offset relative to the fixed axis of rotation of the drive shaft. The height of the guide rollers is adjusted such that, in an entry area for the unfolded plastic closures into the pocket wheel, the distance—i.e., the minimum distance—between the annular pressure surface and the annular guide surface is greater than the height of the unfolded plastic closure. This ensures that the unfolded plastic closures can be fed into the pocket wheel without difficulty.

[0030] In the case of a cardan shaft as a compensating coupling, torque transmission from the shaft to the pressure plate by means of a positive-locking shaft-hub connection and design of the guide means as three rollers resting on the top of the pressure plate, the distance between the guide plate and the pressure plate must be maintained by at least one compression spring acting between the plates.

[0031] Due to the angular offset of the printing plate's axis of rotation, the upper edge of each locking element initially comes into contact with the annular printing surface as it enters the folding area. With further rotation of the pocket wheel, the upper edge of the plastic closure's tamper-evident band then rests against the printing surface after the folding process is complete.

[0032] In order to ensure the most uniform possible force transmission into the upper edge of the locking element of each plastic closure in the folding area, the angular offset between the axis of rotation of the drive shaft and the axis of rotation of the pressure plate corresponds to the angle of the beveled annular pressure surface relative to the plate plane.

[0033] The distance (H), i.e. the smallest distance between the annular pressure surface and the annular guide surface in the folding area, is equal to or slightly less than the height of the plastic closure cap and the warranty band.

[0034] To avoid imbalances during operation of the folding device, the guide plate and the pressure plate are preferably circular. The circular plates do not necessarily have to be designed in the manner of a disc wheel, but can have recesses between the annular pressure or guide surface and the respective axis of rotation to reduce the moving mass, thus forming, for example, a spoke-shaped structure.

[0035] The following section explains in more detail a preferred folding device for carrying out the method with reference to the figures. They show Figure 1a a perspective view of an unfolded plastic closure, Figure 1b a side view of an unfolded plastic fastener, Figure 1c a sectional view of a folded plastic closure, Figure 2a a perspective overall view of a folding device according to the invention for carrying out the method, Figure 2ba representation of the folding device according to Figure 2a with the pressure plate removed, Figure 3 a view of the folding device after Figure 2b as well as Figure 4 A cutaway side view of the folding device with an enlarged representation of the folding area.

[0036] Figures 1 ac show a plastic closure 4 which can be folded using the method and folding device according to the invention. Figures 1a, 1b show an unfolded plastic closure 4, 4.6 and Figure 1c a folded plastic closure 4, 4.7.

[0037] The plastic closure 4 has a closure cap 4.5, which is bounded by a cylindrical shell 4.5.1 and a base 4.5.2. A tamper-evident band 4.2 is connected to the upper edge of the closure cap 4.5 by thin struts (not shown).

[0038] Several locking elements 4.4 are attached to an upper edge 4.1 of the warranty band 4.2 and are interconnected via a ring 4.4.1. As can be seen in particular from Figure 1b As can be seen, the locking elements 4.4 are slightly inclined inwards towards the axis of rotation of the unfolded plastic closure 4, 4.6. The locking elements 4.4 must be folded inwards towards the plastic closure during the folding process, as shown in the sectional view. Figure 1c is shown.

[0039] From the overall view of Figures 2 a , b and 3 The basic structure of the folding device for continuously folding the locking elements 4.4 of matching plastic closures 4 is recognizable. The device comprises a rotatable pocket wheel 5, a circular guide plate 9 arranged on the underside of the pocket wheel 5, and a circular pressure plate 1 arranged on the top side of the pocket wheel 5.

[0040] A drive 6 is attached to the underside of a frame 13 of the folding device, which has a motor 6.2 with a drive shaft 6.1 rotatable about a pivot axis 11, which is arranged to rotate the pocket wheel 5, the guide plate 9 and the pressure plate 1 in the same direction and with the same angular velocity (cf. Figure 4 ).

[0041] The pressure plate 1 is connected to the drive shaft 6.1 by means of a compensating coupling 7, for example a spring-disc coupling or a universal joint, in order to compensate for an angular misalignment (α) between the axis of rotation 11 of the drive shaft 6.1 and the axis of rotation 12 of the pressure plate 1. The axes of rotation 11, 12 are fixed in space, so that the pressure plate 1 always maintains the orientation relative to the guide plate 9. Figure 4The inclined position shown is maintained. To adjust the angular offset (α) of the rotary axes 11, 12, three guide rollers 8 rolling on the top of the pressure plate 1 are arranged height-adjustable on frame-mounted bearing blocks 8.1 (see figure). Fig. 2a ).

[0042] About a best from Figure 3 The unfolded plastic closures 4, 4.6 enter the pockets 5.1 of the counterclockwise rotating pocket wheel 5 in an inlet area 3 via a visible feed 2. The feed is provided, for example, by a storage conveyor and / or a pneumatic conveyor or by gravity.

[0043] From the inlet area 3, the pocket wheel 5 transports the unfolded plastic closures 4.6 on a circular path towards the folding area 10. The plastic closures 4 rest with their cap base 4.5.2 on an annular guide surface 9.1 of the guide plate 9 (see figure). Figure 4During transport, no relative movement occurs between the plastic closures 4 and the guide plate 9 because the guide plate 9 rotates in the same direction and at the same angular velocity as the pocket wheel 5. Therefore, wear marks on the cap base 4.5.2 are effectively avoided.

[0044] Due to the angular offset (α) between the axis of rotation 11 of the drive shaft and the axis of rotation 12 of the pressure plate 1, the distance of the pressure plate 1 to the guide plate 9 in the inlet area 3 is significantly larger than in the folding area 10 (cf. Figure 4 In particular, the distance between the pressure plate 1 and the guide plate 9 in the inlet area 3 is greater than the height of the unfolded plastic closures 4, 4.6, so that these can be fed to the pocket wheel 5 in the inlet area 3 without any problems.

[0045] Along the circular conveying path towards the folding area 10, the distance between the guide plate 9 and the pressure plate 1 gradually decreases. The pressure plate 1 has a chamfer 1.2 at an angle (α) relative to the plate plane 1.3 of the pressure plate 1, which corresponds to the angular offset (α) between the axes of rotation 11, 12. The distance (H), i.e., the minimum distance between the annular pressure surface 1.1 and the annular guide surface 9.1 in the folding area 10, corresponds to the height (h) of the closure cap 4.5 of the plastic closure 4 and the tamper-evident band 4.2.

[0046] This distance (H), in conjunction with the angular offset (α), causes the upper edge 4.1 of the tamper-evident band 4.2 of each plastic closure 4 to temporarily rest against the printing surface 1.1 of the printing plate 1 in the folding area 10 after the folding has been completed. This point in time is shown in the enlarged view in Figure 4illustrated. It can be seen that the locking elements 4.4 are in Figure 1c have assumed the position shown, and as a result, the upper edge 4.1 of the warranty band 4.2 is in contact with the printing surface 1.1.

[0047] Furthermore, the enlarged view in Figure 4 It can be seen that one of the guide rollers 8 rolls above the folding area 10 on the pressure plate 1 and another, non-height-adjustable guide roller 8 rolls below the folding area 10 on the underside of the guide plate 9 and has a support function there.

[0048] The pressure plate 1 and the pressure surface 1.1 are made of a material with a high hardness that is significantly higher than that of the plastic closures 4. This high hardness has a beneficial effect on the wear behavior of the pressure surface 1.1, which interacts with the locking elements 4.4 of the plastic closures 4 during folding. The coefficient of sliding friction between the material of the pressure plate 1 and the plastic closures 4 is preferably less than 0.35. The hardness of the pressure plate 1 and the coefficient of sliding friction ensure that the locking elements 4.4 of the plastic closures 4 do not interlock or catch with the pressure surface 1.1 of the pressure plate 1, but can slide smoothly on it. This ensures a reliable folding process during the rapid passage of the plastic closures 4 through the folding area 10. Reference symbol list

[0049] 1 printing plate 1.1 Print area 1.2 bevel 1.3 plate level 2 Supply 3 Entrance area 4 plastic closure 4.1 Top edge of the warranty band 4.2 Warranty band 4.3 Upper edge of the locking element 4.4 Locking element 4.4.1 Ring locking element 4.5 Cap 4.5.1 Coat 4.5.2 Cap bottom 4.6 Plastic closure unfolded 4.7 Plastic closure folded 5 pocket wheel 5.1 Bags 6 drive 6.1 drive shaft 6.2 Motor 7 Compensating clutch 8 leadership role 8.1 bearing block 9 guide plate 9.1 Guide surface 10 Folding area 11 Pivot axis drive shaft 12 Rotary axis pressure plate 13 frame H Distance between the printing surface and the guide surface in the folding area h Height of the cap and the warranty band α Angular offset between the axis of rotation of the pressure plate and the axis of rotation of the guide plate

Claims

1. Method for continuously folding locking elements (4.4) of matching plastic closures (4) connected to an upper edge (4.1) of a tamper-evident band (4.2), wherein the tamper-evident band (4.2) is arranged on a cylindrical closure cap (4.5) of each plastic closure (4), wherein - each plastic closure (4) is continuously brought between a pressure surface (1.1) interacting with an upper edge (4.3) of the tamper-evident elements (4.4) and a guide surface (9.1) in a folding area (10) along a conveying path, wherein - the plastic closures (4) run through the folding area (10), - the pressure surface (1.1) and the guide surface (9.1) are arranged in the folding area (10) in such a manner with respect to one another that the upper edge (4.1) of the tamper-evident band (4.2) of each plastic closure (4) temporarily rests at least partially against the pressure surface (1.1) after completion of the folding process, - the distance (H), i.e. the shortest distance between the pressure surface (1.1) and the guide surface (9.1) in the folding area (10) is equal to or slightly less than the height (h) of the closure cap (4.5) of the plastic closure (4) and the tamper-evident band (4.2) and - the pressure surface (1.1) is rigid2. Method according to Claim 1, characterized in that each plastic closure (4) is continuously brought into the folding area (10) by means of a continuous conveyor which is arranged along the conveying path of the continuous conveyor.

3. Method according to Claim 1 or 2, characterized in that the pressure surface (1.1) consists of a metallic material.

4. Method according to one of Claims 1 to 3, characterized in that the pressure surface (1.1) consists of a material having a Rockwell hardness with a hardness value ≥ 50 HRC.

5. Method according to one of Claims 1 to 4, characterized in that the coefficient of sliding friction (µGR) between the material of the pressure surface and the plastic material of the plastic closure (4) is µGR ≤ 0.50, preferably µGR ≤ 0.35.

6. Method according to one of Claims 1 to 5, characterized in that the upper edge (4.1) of the tamper-evident band (4.2) of each plastic closure (4) temporarily rests in an annular manner against the pressure surface (1.1).

7. Folding device for continuously folding locking elements (4.4) of matching plastic closures (4) attached to an upper edge (4.1) of a tamper-evident band (4.2), wherein the tamper-evident band (4.2) is arranged on a cylindrical closure cap (4.5) of each plastic closure (4), characterized by - a pocket wheel (5), - a guide plate (9) arranged on a bottom side of the pocket wheel (5) having an annular guide surface (9.1) lying in the plane of the plate, - a pressure plate (1) arranged on a top side of the pocket wheel (5) having an annular pressure surface (1.1) chamfered with respect to the plane of the plate (1.3), - a drive (6) with a drive shaft (6.1) rotatable about a pivot axis (11), adapted to rotate the pocket wheel (5), the guide plate (9) and the pressure plate (1) in the same direction and at the same angular velocity, wherein the pocket wheel (5) and the guide plate (9) rotate about the axis of rotation (11) of the drive shaft, - a compensating coupling (7) between the drive shaft (6.1) and the pressure plate (1) which compensates for an angular offset (α) between the axis of rotation (11) of the drive shaft (6.1) and the axis of rotation (12) of the pressure plate (1), - guide means, adapted to bring about a rotation of the pressure plate (1) about its axis of rotation (12) with an angular offset (α) with respect to the axis of rotation (11) of the drive shaft (6.1), - an inlet area (3) for the unfolded plastic closures (4.6) into the pocket wheel (5), wherein in the inlet area (3) the distance between the annular pressure surface (1.1) and the annular guide surface (9.1) is greater than the height of the unfolded plastic closure (4.6), - a folding area (10) arranged downstream of the entry area (3) in the direction of rotation of the pocket wheel (5), wherein the annular pressure surface (1.1) and the annular guide surface (9.1) lie opposite each other in the folding area (10) such that the upper edge (4.1) of the tamper-evident band (4.2) of each plastic closure (4) temporarily rests at least partially against the pressure surface (1.1) after completion of the folding process.

8. Folding device according to Claim 7, characterized in that the distance (H) between the annular pressure surface (1.1) and the annular guide surface (9.1) in the folding area (10) is equal to or slightly less than the height (h) of the closure cap (4.5) and the tamper-evident band (4.2) of the plastic closure (4).

9. Folding device according to Claim 7 or 8, characterized in that the angular offset (α) between the axis of rotation (11) of the drive shaft (6.1) and the axis of rotation (12) of the pressure plate (1) corresponds to the angle (α) of the bevelled, annular pressure surface (1.1) with respect to the plate plane (1.3).

10. Folding device according to one of Claims 7 to 9, characterized in that the guide plate and the pressure plate are circular.

11. Folding device according to one of Claims 7 to 10, characterized in that the guide means comprise at least three guide rollers (8) resting on the top side of the pressure plate (1).