EP0737156A1

EP0737156A1 - Plastic snap closure with a warranty seal and method for its production

Info

Publication number: EP0737156A1
Application number: EP95934035A
Authority: EP
Inventors: Udo Bösl; Kelvin Pitman
Original assignee: Crown Cork AG
Current assignee: Crown Cork AG
Priority date: 1994-11-02
Filing date: 1995-10-23
Publication date: 1996-10-16
Anticipated expiration: 2015-10-23
Also published as: HUT74809A; CN1138313A; CO4440650A1; CA2178648A1; IL115695A0; WO1996014252A1; HU9601692D0; ATE174293T1; AU3649395A; EP0737156B1; DE59504488D1; AU693606B2; MX9602564A; US5836468A; ZA959238B; JPH09511206A; ES2125662T3; IL115695A; RU2125530C1; KR960706435A

Abstract

PCT No. PCT/CH95/00248 Sec. 371 Date Jun. 14, 1996 Sec. 102(e) Date Jun. 14, 1996 PCT Filed Oct. 23, 1995 PCT Pub. No. WO96/14252 PCT Pub. Date May 17, 1996The plastic snap closure possesses a snapping means (3) on the inside surface of the cap wall (2), said snapping means being able to be snapped over a bead on the container mouth. In order to display initial opening of the closure, approximately vertical weakened zones (4) are provided on the lower edge of the closure cap. The cap wall (2) will tear on initial opening of the snap closure in the area of at least one of these weakened zones (4).

Description

Plastic snap lock with guarantee and process for its manufacture

The invention relates to a plastic snap closure according to the features in the preamble of claim 1 and a method for its production. Snap closures of this type are used for closing containers which have a circumferential bead on the outside of their approximately cylindrical mouth region. A main area of application is the closure of beverage bottles, e.g. Beer or mineral water bottles.

Containers of this type are often closed with metal crown caps, which are attached with the aid of suitable folding devices. When the container is closed, the folded cap wall engages over the bead at the mouth of the container. Such a closure is opened by bending the cap wall sideways using a conventional cap lifter. This leads to a plastic deformation of the cap wall, the metallic crown cap can therefore no longer be reliably closed after the container has been opened for the first time.

EP-21 036 has therefore already proposed using a sealing capsule made of synthetic resin instead of the metallic crown cap, which can be snapped onto the container mouth. For this purpose, the synthetic resin cap has a projecting collar on its inner circumference, which, when the container is closed, engages over the bead at the container mouth in order to seal the bottle in a sealed manner. The closure is also opened here with a conventional cap lifter; since the closure cap is made of elastic material, it can be in contrast to the Remove the metallic crown cap from the container mouth without plastic deformation of the cap wall. When opened, the cap wall is only elastically expanded and then takes on its original shape again. The closure cap can therefore be used repeatedly and the quality of the sealing of the closure is not adversely affected even after repeated opening and closing.

Apart from their qualities with regard to the sealing of the container, closure caps are often required to indicate the first opening of the container in the most obvious way possible and thus to fulfill a guarantee function. EP-21 036 proposes to reduce the thickness of the cap wall in its lower region, so that it is deformed at this point by the gripping tooth of the cap lifter when the container is opened. This deformation indicates that the container has been opened for the first time. The quality and reliability of this guarantee function depends to a large extent on the design of the cap lifter used. A cap lifter with a narrow gripping tooth, e.g. in the case of the cap lifters contained in pocket knives leads to a significant violation of the lower edge of the cap wall. As a rule, however, the cap lifters used to open metallic crown caps have a rather wide gripping tooth, with which the plastic cap described in EP-21036 can be removed from a container without obviously damaging the cap wall. The deformation of the cap wall caused by the gripping tooth can largely recede after opening, so that the guarantee function is not reliably guaranteed.

It is an object of the invention to improve the guarantee function of the known snap locks and to create a plastic snap lock which is the first Open reliably and clearly visible.

This object is achieved according to the invention by a plastic snap lock with the features of claim 1 and a method for its production with the features of claims 9 or 11.

On the inner surface of the cap wall protruding latching means are arranged along the circumference and can be snapped over a bead on the container mouth. The radial thickness of these locking means reaches a maximum in an annular locking area of the cap wall. During assembly, the sealing cap is pressed onto the container mouth in the axial direction. The cap wall is expanded elastically and the locking means of the closure cap slide over the bead at the container mouth. As soon as the annular latching area and thus the thickest point of the latching means has overcome the bead, the closure cap snaps onto the container mouth. Below the latching area, the cap wall has at least three, approximately vertically extending weakening zones distributed over the circumference, in which the strength of the cap wall is reduced. As a rule, the weakening zones are reduced by at least partially reducing the wall thickness, e.g. formed by perforation or by vertical notches.

To remove the cap from the container mouth, a lifting tool must be attached to the lower edge of the cap. The resulting load on the cap wall causes the cap wall to tear in the area of at least one of the weakening zones. This tearing causes permanent damage to the cap wall, which clearly shows the first time the cap is opened.

The quality of the snap lock in terms of its tightness is primarily due to the strength of the other Depending on the inner surface of the cap wall protruding locking means. In order to ensure the original quality of the seal even when the container is closed again after it has been opened for the first time, the strength of the cap wall in the annular latching area must not be impaired. For this reason, the vertically extending weakening zones are arranged below the locking area, so that the strength of the locking area is not impaired even if the cap wall tears in the area of one or more weakening zones.

The cap lifters which are also customary for opening metal crown caps and whose gripping tooth engages on one side of the cap wall are preferably used to open the snap closure. The cap wall must tear when the snap closure is opened for the first time, regardless of where the cap lifter is attached to the circumference of the cap. To ensure this, at least three vertically running weakening zones are required, which are arranged distributed over the circumference. However, a larger number of weakening zones is preferably used.

The greatest forces act when opening the snap closure at the lower edge of the cap wall. Tearing in the area of the weakened zones is therefore favored if these extend to the lower edge of the cap wall.

The tearing of the cap wall in the area of a weakening zone is particularly evident when the cap wall has a smooth outer surface in the area of the weakening zone. This can e.g. can be achieved if the weakening zones are formed by depressions provided on the inner surface of the cap wall.

The cap wall tears in the area of the weakened zones even with slight force. Without affecting the guarantee function, the snap closure can therefore be designed in such a way that it can be removed from the mouth of the container with relatively little effort. In a preferred embodiment variant, a plurality of latching elements which are arranged along the circumference on the inner surface of the cap wall and which are separated from one another by spacings are used as latching means. This configuration has the advantage over a circumferential locking bead that the cap wall in the space between successive locking elements is more elastic and flexible. This results in a reduction in the force required to lift the snap lock.

A further improvement is obtained if the weakening zones are arranged in the space between successive locking elements. The weakened zones are thus located in an area of the cap wall that is not reinforced by locking elements provided on the inner surface. Since these areas are particularly stretched when the snap fastener is opened, the tearing of the cap wall is further promoted by the weakening zones arranged in this area.

To open the snap lock it is preferred to use a cap lifter which can also be used to remove metal crown caps. Cap lifters of this type have a gripping tooth which engages under the lower edge of the cap wall at one point on the circumference and a support surface which is connected to the gripping tooth and which lies against the outside of the cap base and serves as an abutment. In most cap lifters, the distance between the gripping tooth and the support surface is matched to the relatively flat metal crown caps and is generally about 12-15 mm. In a preferred embodiment variant, the height of the closure cap is therefore a maximum of only 12, so that the closure with a Cap lifter of the type mentioned can be opened.

Special requirements are placed on the strength of the cap wall. When opening, the cap wall should tear in the area of the vertical weakening zones. This is achieved by forces acting on the lower edge of the cap in the radial direction. On the other hand, the simultaneous compression of the cap wall in the axial direction is undesirable, since the vertical force component is primarily required to lift the closure cap. In order to keep the axial compression of the cap wall as small as possible, the cap wall is preferably designed in such a way that its outer surface has a plurality of ribs arranged radially outward and distributed over the circumference. These ribs increase the axial load capacity of the cap wall. Since the load caused by a cap lifter is greatest at the lower edge of the cap, the ribs are preferably designed so that they extend to the lower edge of the cap. At the same time, this has the advantage that the contact surface available for the gripping tooth of the cap lifter at the lower edge of the cap increases in the area of the ribs. The attachment of ribs on the cap wall leads to an increase in the wall thickness in the area of these ribs. The vertical weakening zones, in the area of which the smallest possible wall thickness is sought, are therefore preferably arranged in the space between successive ribs.

A second possibility for improving the axial loading capacity of the cap wall consists in forming the lower region of the cap wall, which is provided with weakening zones, from two concentric ring elements. The cap wall in its lower area, which is provided with weakening zones, consists of an inner support ring and a guarantee ring which is arranged concentrically to the support ring and surrounds the support ring. The approximately vertical weakening zones are provided on the outer guarantee ring. This is achieved. that when opening for the first time, the outer guarantee ring is primarily destroyed and the more stable support ring absorbs the vertical lifting forces of the cap lifter. The concentric rings are therefore preferably designed in such a way that only the outer guarantee ring has weakening zones, while the inner support ring is not weakened by weakening zones and therefore has a much higher strength.

In order to ensure that the outer guarantee ring is actually destroyed when the closure is opened for the first time, a snap closure of this type is preferably designed in such a way that the guarantee ring extends downward beyond the lower edge of the support ring. The principles for the design of the weakening zones which have already been explained above also apply in the event that these are attached to a guarantee ring of the type just described. Here, too, the weakening zone is preferably formed by a recess provided on the inner surface of the guarantee ring, the guarantee ring having a smooth outer surface in the region of the weakening zones. This has the advantage that the tearing is immediately recognizable from the outside.

When dimensioning the guarantee ring and the inner support ring, the different functions of these wall elements must be taken into account. The size ratios are preferably selected such that the radial thickness of the guarantee ring is smaller than the radial thickness of the support ring.

The connection between the individual wall elements can also be designed differently. In this context, wall elements are three elements, namely the support ring, the guarantee ring surrounding the support ring and the upper part of the cap wall, which in this context can also be regarded as a third ring element and is referred to below as the wall ring. When designing the Connections, in turn, the function of the individual elements must be taken into account. The support ring must transmit the forces of the cap lifter acting in the axial direction to the upper wall ring (on which the latching elements of the snap lock are arranged). The support ring is therefore preferably designed as a direct extension of the upper wall ring, so that the support ring forms a continuous wall section together with the upper wall ring. Slightly different diameters of the support ring and wall ring are of course still possible, in particular the outer diameter of the support ring is preferably somewhat reduced compared to that of the wall ring in order to make room for the outer guarantee ring.

The outer guarantee ring can also be connected to the upper wall ring of the cap wall in the same way as the support ring. As an alternative to this, the guarantee ring can also be connected to the rest of the cap wall only by a plurality of elastic webs distributed over the circumference. The "rest of the cap wall" means the wall ring and the adjoining support ring. The connection by means of webs further increases the radial mobility of the guarantee ring, so that when the closure is opened for the first time by the cap lifter it is pressed more easily outward and the vertical weakening zones thus tear more quickly.

If the guarantee ring is connected to the rest of the cap wall by means of webs, these webs can also take on a guarantee function: the connecting webs are designed in such a way that individual ones of these webs tear off when they are opened for the first time. In order to enable tearing off, a guarantee ring is required, the inside diameter of which is larger than the maximum outside diameter of the rest of the cap wall. The webs are preferably arranged between the inner surface of the guarantee ring and the outer surface of the support ring. The force required to tear off the guarantee ring is determined by the number and thickness of the webs.

The weakened zones are preferably designed in such a way that the tearing of the cap wall is clearly visible, particularly in its lower area. According to a variant already described above, the weakening zone is preferably designed such that the outer surface of the cap wall has a smooth surface. A crack is particularly easy to see on the smooth outer surface. The cap wall tears particularly easily when it is broken through in the upper region of the weakened zone, so that there is a tearable web between the break-through locations and the lower edge of the cap wall. A smooth outer surface is again preferred in the area of the web, since a crack is then particularly easily recognizable.

Particularly efficient and cost-effective production is achieved if the snap closure is made in one piece from plastic.

In addition to the initial assembly of the snap closure already mentioned at the beginning by snapping the closure cap onto the container mouth, other assembly methods are also conceivable in which the closure cap is deformed by external heat and brought into its final shape after being placed on the container mouth. This deformation can be achieved either by using a heat-shrinkable plastic, or by external force. For example, an electrically heated assembly pliers could be used, which .; the cap wall deformed when placed on the container mouth. The weakening zones can also be retrofitted in this way.

A simple variant for producing the above The described snap lock consists of casting the entire snap lock together with the vertically running weakening zones in one operation. Depending on the shape of the desired weakening zones, however, it can be advantageous to add the weakening zones only afterwards. For this purpose, a closure is first produced in a casting process with a cap base, a cylindrical cap wall adjoining it and with locking means protruding along the circumference on the inner surface of the cap wall. Then, in a further work step, at least three approximately vertically running weakening zones are attached in the lower region of the cap wall. The weakening zones can be attached, for example, with the aid of a cutting tool by cutting or milling. Alternatively, it is also possible to apply the weakening zones by subsequent hot forming or by melting, for example using a heated tool. The weakening zones can be attached before but also after the closure cap has been placed on the container mouth.

In an alternative method for producing a snap closure, a closure cap is first produced in a casting process, the cap wall of which has a plurality of slots which extend vertically upward from its lower edge. These slots are at least partially closed again by deforming the cap wall and / or by filling plastic material, so that a weakening zone of the cap wall remains in the area of the slots. The plastic material filled into the slots can be, for example, a liquid or pasty adhesive, which then dries and hardens. However, it can also be a thermoplastic which is filled into the slots when heated and solidifies again when it cools down. The reopening of the slots during the assembly of the snap lock can be prevented in this embodiment. that the slots are closed only after the snap lock has been installed.

The invention is explained in more detail below on the basis of exemplary embodiments. Show it:

1 shows the view of a snap lock according to the invention from below.

FIG. 2 shows an illustration of the sectional plane A-A in FIG. 1,

FIG. 3 shows the sectional view of a container mouth closed by a snap lock with a cap lifter attached,

FIG. 4 shows the state of the arrangement shown in FIG. 3 after the snap lock has been raised,

FIG. 5 shows the perspective illustration of a snap closure after the first opening,

FIG. 6 shows the side view of a snap lock with a preferred alternative for designing the weakening zones,

FIG. 7 shows a snap closure placed on a container mouth with radially projecting ribs on the outer surface of the cap wall,

FIG. 8 the bottom view of the closure cap shown in FIG. 7,

FIG. 9 shows the edge region of a snap lock, the cap wall of which consists of a support ring and a guarantee ring in the lower region, 10 shows a snap lock with a guarantee ring, which is connected by webs to the rest of the cap wall, and

Figure 11 is a bottom view of the snap closure shown in Figure 10.

FIG. 1 shows a snap closure according to the invention from below, with a view of the inner surface of the cap base 1. On the inner surface of the cap wall 2, several latching elements 3 are arranged distributed over the circumference, which engage a bulge on the mouth of the container when the snap closure is fitted. The vertically extending weakening zones 4 are formed by notches 13 on the inner surface of the cap wall 2, which are arranged in the space between latching elements 3 which take place on top of one another.

FIG. 2 shows a sectional illustration of the snap closure according to FIG. 1, the sectional plane runs along the plane A-A shown in FIG. 1. The notches 13 are provided on the inner surface of the cap wall 2, so that the cap wall has a smooth outer surface 17 in the region of the weakening zones 4. The tearing of the cap wall can therefore be seen particularly well from the outside. The notches 13 extend to the lower edge 14 of the cap wall 2.

Figure 3 shows the sectional view of a container mouth with a snap lock attached. The locking elements 3 reach behind a bead 5 of the container mouth. The ring-shaped locking area 6, in which the radial thickness of the locking elements 3 reaches its maximum 7, is particularly important for the fastening of the closure cap on the container mouth. A weakening of the cap wall 2 in the area of the annular locking area 6 would greatly reduce the quality of the seal that can be achieved. The weakening zones 4 formed by notches 13 are therefore below the annular latching area. Reichs 6 of the cap wall 2 arranged.

A cap lifter 10 is also shown in FIG. 3, in a position as it is attached to the snap closure for opening the container. The gripping tooth 9 of the cap lifter engages under the lower edge of the closure cap at one point. The gripping tooth 9 is connected to a contact surface 18 of the cap lifter, which rests on the outside of the cap bottom 1. Since the distance 19 between the gripping tooth 9 and the contact surface 18 is usually between 12 and 15 mm in conventional cap lifters which are also suitable for opening metal crown caps, the plastic snap closures are also preferably designed such that their height 12 is a maximum of 12 mm. Furthermore, it is advantageous for the opening by means of a cap lifter if there is a distance 8 between the inner surface of the cap wall and the outer surface of the container neck, so that the gripping tooth 9 of the cap lifter can reach behind the lower edge of the cap wall as much as possible.

If the cap lifter 10 shown in FIG. 3 is moved in the direction of the arrow 11, the gripping tooth 9 is simultaneously pressed against the underside of the cap wall, which ultimately leads to the snap closure being lifted off the container mouth on one side. An arrangement which is in this state is shown in FIG. At the point where the gripping tooth 9 lies against the cap wall, this was pressed outwards when it was opened. The cap wall was torn in the area of the weakening zone 4 in the vicinity of the gripping tooth 9, so that the first opening of the snap lock is immediately apparent. In the example shown in FIGS. 3 and 4, the gripping tooth 9 of the cap lifter lies precisely against the cap wall 2 in the area of a weakening zone 4. However, the cap wall is so easily torn in the area of the weakened zones 4 that it also tears in the area of the closest weakened zones if the gripper tooth is placed in the middle between two neighboring weakening zones.

FIG. 5 shows the perspective illustration of a snap lock after the first opening. The cap wall 2 is torn open in the region of two vertical weakening zones 4a. Such a picture is obtained when the cap lifter is placed between these two weakening zones 4a when the closure is opened. The cracks in the cap wall are unmistakable and ensure a reliable guarantee function.

FIG. 6 shows the side view of an alternative embodiment of a snap lock, in which the cap wall is broken through in the upper region of the weakening zones. Below the breakthrough points 15 there is in each case a tearable web 16. This variant has the advantage that the part of the cap wall to be torn is concentrated on the web 16 and thus on the lower edge region of the cap wall. Since the load occurring at the bottom of the cap wall when opening is greatest, the webs 16 tear particularly quickly. A further improvement could be achieved by additionally reducing the radial thickness of the webs 16. This is advantageously achieved by an additional notch on the inner surface of the cap wall, so that the cap wall in the region of the web 16 still has a smooth outer surface.

FIG. 7 shows a snap closure placed on a container mouth, the cap wall of which has a plurality of ribs which are distributed over the circumference and project radially outwards. In the left half of FIG. 7, the exterior view of the snap lock is shown, in the right half a sectional view. With the elongated, approximately vertically extending ribs 20 on the outer surface of the cap wall an increased resilience of the cap wall in axial direction 27 reached. Since the ribs 20 extend to the lower edge of the cap wall, the area of attack available for attaching a cap lifter is increased at the same time. This can also be seen from FIG. 8, in which the closure cap according to FIG. 7 is shown in a view from below. The vertically extending weakening zones 4 are each arranged in an intermediate space between two adjacent ribs 20. The weakened zones 4 are formed by indentations on the inner surface of the cap wall. In the space between adjacent ribs 20, the cap wall has a smooth outer surface, so that the tearing in of a weakening zone can be easily recognized from the outside.

FIG. 9 shows the sectional view of the edge region of a closure cap, the cap wall of which consists in its lower region, provided with weakening zones 4b, of a support ring 21 and a guarantee ring 22 surrounding the support ring and arranged concentrically to the latter. The weakening zones 4b are provided on the outer guarantee ring 22. These are formed by notches 13a on the inner surface of the guarantee, so that the guarantee ring maintains a smooth outer surface in the area of the weakening zones and the tearing of a weakening zone is easily recognizable. The guarantee ring 22 extends beyond the lower edge of the support ring 21 downwards. This ensures that the guarantee ring 22 can still be gripped by a conventional cap lifter, which usually engages on the inner edge of the support ring 21 (see also FIG. 3). The radial thickness 24 of the guarantee ring 22 is substantially smaller than the radial thickness 25 of the support ring 21. This takes into account the fact that the guarantee ring 22 should be as fragile as possible, whereas the inner support ring 21 should transmit the lifting force exerted by a cap lifter and therefore needs some strength. In addition to the inner support ring 21 and the outer guarantee ring 22, the cap wall of this snap closure also has an upper wall area, which is basically also an annular section, which is referred to below as the wall ring 26. The cap wall thus basically consists of three ring elements which are interconnected. The support ring 21 shown in FIG. 9 represents a direct continuation of the upper wall ring 26, the two ring elements have the same inner diameter. The outer guarantee ring 22 is separated from the inner support ring 21 by a likewise annular space 28. If the entire closure cap is cast in one piece from plastic, this annular space 28 is necessary for manufacturing reasons. The outer diameter of the wall ring 26 assumes the outer diameter of the guarantee ring 22 at its lower end, so that the guarantee ring is also (like the support ring 21) connected at the end face to the upper wall ring.

FIG. 10 shows an alternative embodiment for a snap lock with support ring 21a and guarantee ring 22a. Here, the inside diameter of the guarantee ring 22a is larger than the maximum outside diameter of the rest of the cap wall. The guarantee ring 22a is connected to the rest of the cap wall only by a plurality of elastic webs 23 distributed over the circumference. The expression "rest of the cap wall" at this point stands for the inner support ring 21a and the upper wall ring 26. In the example shown, the webs 23 are arranged between the inner surface of the guarantee ring 22a and the outer surface of the support ring 21a.

Finally, FIG. 11 shows the bottom view of a snap closure according to FIG. 10. It should be noted that in this exemplary embodiment the same number of webs 23 and vertical weakening zones 4c of the guarantee ring 22a are provided, a connecting web 23 being arranged in each case between two vertical weakening zones 4c.

Claims

Claims:

1. Plastic snap closure for containers with an approximately cylindrical mouth area, with a cap base (1) and an adjoining cap wall (2), on the inner surface of which protrudes along the circumference and can be snapped onto the inside of the container by means of a bead (5) ), whose radial thickness in a ring-shaped latching area (6) of the cap wall reaches a maximum (7), characterized in that the vertically extending weakening zones (4) are arranged below the latching area (6).

2. Snap lock according to claim 1, characterized in that the weakening zones (4) extend to the lower edge (14) of the cap wall (2).

3. Snap lock according to one of claims 1 or 2, characterized in that the weakening zones (4) are formed by recesses (13) provided on the inner surface of the cap wall (2) and the cap wall (2) in the region of the weakening zones (4) has smooth outer surface.

4. Snap lock according to one of claims 1 to 3, characterized in that the latching means are a plurality of latching elements (3) arranged on the inner surface of the cap wall along the circumference and separated by spacings.

5. Snap lock according to claim 4, characterized in that the weakening zones (4) are arranged in the space between successive latching elements (3).

6. Snap lock according to one of claims 1 to 5, characterized in that the cap wall (2) in the upper region of the weakening zones (4) is broken, so that there is a respective between the breakthrough points (15) and the lower edge of the cap wall tearable web (16) is located.

7. tendon p closure according to one of claims 1 to 6, characterized in that the outer surface of the cap wall has a plurality of radially outwardly extending ribs (20) which are distributed over the circumference and extend to the lower edge of the cap.

8. Snap lock according to one of claims 1 or 2, characterized in that the cap wall in its lower, with weakening zones (4b, 4c) provided area of an inner support ring (21) and a surrounding the support ring, arranged concentrically to this guarantee (22), and that the weakening zones are provided on the guarantee ring (22).

9. Snap lock according to claim 8, characterized in that the guarantee ring (22) extends downward beyond the lower edge of the support ring (21).

10. Snap lock according to one of claims 8 or 9, characterized in that the weakening zones (4) are formed by recesses (13a) provided on the inner surface of the guarantee ring (22) and the guarantee ring has a smooth exterior in the region of the weakening zones ¬ surface (17a).

11. Snap lock according to one of claims 8 to 10, characterized in that the radial thickness (24) of the guarantee ring is smaller than the radial thickness (25) of the support ring.

12. Snap lock according to one of claims 8 to 11, characterized in that the guarantee ring (22a) is connected to the rest of the cap wall only by a plurality of elastic webs (23) arranged distributed over the circumference.

13. Snap lock according to one of claims 8 to 12, characterized in that the inside diameter of the guarantee ring (22a) is larger than the maximum outside diameter of the rest of the cap wall.

14. Snap lock according to one of claims 1 to 13, characterized in that the height 12 of the closure cap is a maximum of 12 mm, so that it can be removed from a container mouth with a cap lifter which can also be used for removing metal crown caps.

15. A method for producing a snap closure according to one of claims 1 to 14, characterized in that firstly in a casting process, a closure with a cap base (1), an adjoining, cylindrical cap wall (2) and along the inner surface of the cap wall the circumferential protruding means (3) is manufactured and that at least three approximately vertically extending weakening zones are then attached in the lower region of the cap wall.

16. The method according to claim 15, characterized in that the vertical weakening zones (4) are attached with the aid of a cutting tool by cutting or milling and / or hot forming or melting.

17. A method for producing a snap lock according to one of claims 1 to 16, characterized in that a closure is first used in a casting process a cap base (1) and a cylindrical cap wall (2) with locking means on its inner surface, the cap wall having a plurality of slots which extend vertically upwards from its lower edge, and that the slots are formed by deforming the cap wall and / or the filling of plastic material is at least partially closed again, so that a weakening zone of the cap wall remains in the area of the slots.

18. The method according to claim 17, characterized in that the slots are closed only after the assembly of the snap closure.

19. The method according to any one of claims 17 or 18, characterized in that for closing the slots, a liquid or pasty filling material is filled into the slots, which hardens after some time.