CLOSURE CAP MADE OF PLASTICS MATERIAL

Abstract: A closure cap made of plastics material for closing a container mouth (30) consists essentially of a top plate (2) and a skirt (4) extending from the edge (3) of the top plate (2). The closure cap (1) is provided with a sealing lip (5), which has a root section (6) and a sealing section (7), between which a materiel weakening (8, 9, 8) is arranged. In an improvement, the sealing section (35) has an actuating part (39), which engages the container rim (33) during capping, and a sealing part (38) which contacts a sealing surface (32) on the container mouth (30) to form the seal.

Description: CLOSURE CAP MADE OF PLASTICS MATERIAL The present invention concerns a closure cap made of plastics material with the features of the characterising clause of the independent claims. It is known to use closure caps made of plastics material for closing containers, for example bottles. A frequent field of application is beverage bottles, and in particular bottles containing carbonated beverages. The demands on tightness of the closure cap are great, especially with bottles, in which the contents are under an increased pressure. On one hand the closure cap must guarantee that no leakages occur, even in the event of increased internal pressure. On the other hand, on opening the bottle for the first time, the closure cap has to be prevented from flying off the bottle (missiling) , as soon as the thread on the closure disengages with the thread on the bottle. Many possibilities are known for obtaining a sealing effect between a closure cap and container mouth. For example, elastic sealing inserts can be inserted into the closure cap, or deformable sealing lips can be provided. In order to avoid the premature flying off (missiling) of the closure cap, it is likewise already known to design the sealing means so that during the unscrewing process the sealing effect is first of all cancelled and only then do the threads of the closure disengage with the threads of the container mouth. This allows the closure to vent any excess internal pressure before the closure threads fully disengage from the container threads. So-called "trumpet seals" are a typical form of sealing lips. In this case, a cylindrical sealing section, more or less in the form of a truncated cone, extends from a substantially cylindrical root section. When the sealing lip is inserted into a container mouth, the truncated cone-shaped sealing section is folded back towards the root section and lies against the container mouth. This creates a contact pressure and with it a sealing effect. Such trumpet seals do indeed produce satisfactory results with regard to the sealing effect. But one problem with such well-known trumpet seals consists in the fact that the application force, required when putting the closure cap on to the container mouth, is relatively large. Considerable forces are necessary to fold over the sealing section. A further disadvantage with known trumpet seals consists in the fact that the instant at which the sealing effect is cancelled during unscrewing, often cannot be precisely predicted. Depending on the tolerances of the container mouth, the contact force between the sealing section and the container mouth is greater or smaller, so that the sealing effect of the sealing section can vary as a function of the container to be closed. A further problem consists in the fact that the buckling area between the root section and the sealing section often cannot be precisely predetermined. Depending on tolerances of the container mouth to be closed, the sealing section is folded over around different buckling lines. The result of this is that the sealing section does not always seal at the same place on the container mouth. This can have a considerable influence on the sealing properties (sealing areas on container mouths are often defined precisely) and gas blow-off behaviour (the time at which the sealing effect is cancelled) depending on where the sealing section seals on the container mouth) . In addition, so-called olive seals are known. Olive seals have a sealing lip with a convex sealing section, which is designed to seal on the more or less cylindrical inner surface of a container mouth. One problem with such olive seals consists in the fact that, during the capping process (putting the closure cap on to the container mouth) the sealing part (the convex sealing face) engages first with the container mouth, in particular the inner edge of the upper rim thereof. The container mouth is often damaged in the region of this inner rim. This can result in the sealing part of the sealing lip likewise being damaged through contact with the damaged container mouth during the capping process. The consequence of this is a reduction in the sealing effect. Therefore, one aim of the present invention is to avoid the disadvantages of the known closure caps, and in particular to produce a closure cap, which requires reduced application forces when putting the closure cap on the container mouth. In addition, a precisely defined gas blow-off pressure should be able to be obtained with the closure cap according to the invention. Moreover, the closure cap is adapted to allow sealing against a precise, predefined sealing face on the container mouth. A further aim of the invention consists in producing a closure cap with a sealing lip, in which the problem of damage to the sealing zone during the capping process, due to contact with a damaged container mouth, is avoided. According to the invention, these objectives are met with a closure cap having the features of the characterising part of the independent claims. A closure cap for closing a container mouth is made of a plastics material and has a top plate and a skirt extending from the edge of the top plate. The closure cap is provided with at least one sealing lip. The sealing lip has a root section and a sealing section. The root section is connected to the closure cap and the sealing section is adapted to be pressed against a sealing surface of the container mouth. According to the invention, the sealing lip is provided with a material weakening between the root section and the sealing section. Compared with conventional sealing lips of this kind (e.g. so-called trumpet seals) the sealing section is movable in relation to the root section, i.e. it can be easily tilted. The material weakening has various advantages: The force required to tilt the sealing section is reduced. Therefore, the application forces required during the capping process are smaller. In addition, the place at which the sealing lip is buckled during the capping process can be precisely predetermined. In contrast to known trumpet seals, in which the sealing line among other things is also a function of the geometry of the container to be closed, the trumpet seal according to the invention always buckles in the region of the material weakening. The position of the sealing section when the closure is put on the container can therefore be predetermined. This results in a smaller scatter width of the gas blow-off angle. The gas blow-off angle is understood to be the angle of rotation of the closure cap at the instant when the seal disengages with the container mouth during unscrewing, allowing excess pressure to escape from the container. On account of the more precisely defined application force and the predeterminable surface, against which the sealing lip is pressed against the container, this angle of rotation is precisely defined. In a preferred embodiment of the invention, the root section is substantially cylindrical and extends from the cap top plate. The sealing section is designed more or less in the form of a truncated cone and extends from the distal end of the root section. In this embodiment the seal takes the form of a classic trumpet seal. However, alternative sealing lip arrangements are also conceivable. For example, the sealing lip, and in particular the root section thereof, may extend radially inwards from the cap skirt instead of axially downwards from the cap top plate. Advantageously, the material weakening is continuous. This means that the material weakening extends over an angular range of 360°. This results in a particularly uniform sealing behaviour over the whole circumference of the closure. Alternatively the material weakenings may only be provided in segments. Such segmented material weakenings have the advantage that a precise buckling line is defined, but in addition, looked at in the circumferential direction, zones with a smaller contact force are produced. The sealing effect is cancelled first in these zones, in response to increased internal pressure. This results in a controlled gas blow- off behaviour in the region of the material weakenings. The present invention can be realized particularly easily if the material weakening is formed as a groove on one of the surfaces of the sealing lip. A formation such as a groove is particularly beneficial from a production point of view. Advantageously, such a groove is arranged on the surface of the sealing lip turned away from the cap top plate. This arrangement is particularly advantageous with regard to the deformability of the closure cap during ejection from an injection mould. The sealing lip can be formed as an inner seal. In which case, the sealing section extends radially outwards from the root section. The material weakening is preferably arranged radially outside the cylindrical face running through the middle of the root section. The material weakening thus arranged acts as a link between root section and sealing section. Alternatively, the sealing lip can be formed as an outer seal. In this case, the sealing section extends radially inwards from the root section and the material weakening is arranged radially inside the cylindrical face running through the middle of the root section. Particularly advantageously, the material weakening is arranged on or immediately adjacent to the inner or outer face of the root section, as appropriate. In this way, a precisely defined joint is formed. The root section is usually made relatively stable and acts as a relatively undeformable buttress. If the material weakening directly adjoins the root section acting as buttress, a joint-like connection of the sealing section to the essentially immovable root section results. The degree of material weakening is deliberately adjusted so that, on the one hand the ability of the sealing section to tilt in relation to the root section is increased, but on the other hand, a sufficiently high contact force is obtained between the sealing section and a sealing face of the container mouth. Typically, the thickness of the sealing lip in the region of the material weakening is about 30 - 90 %, advantageously about 2/3 of the thickness of the sealing section. Obviously, it is also possible to provide two such sealing lips, which can seal against the inside and the outside of a container mouth. Likewise it is possible to provide material weakenings other than grooves, for example through a different choice of material, through a plastics material with a different density, or through mechanical finishing. According to an alternative embodiment of the invention a closure cap made of plasitcs material is proposed, in which the sealing lip has a root section and a sealing section, wherein the root section is joined to the closure cap and the sealing section is adapted to be pressed against a sealing face of the container mouth, when the closure is applied to the container. According to this embodiment of the invention, the sealing section is tiltable between an initial position and a sealing position. The sealing section is tiltably joined to the root section. The sealing section has a sealing part and an actuating part different from the sealing part. Initially, the actuating part of the sealing section is brought into engagement with the upper edge of the container mouth, which may be damaged. However, in the sealing position the sealing part of the sealing section is pressed against the container mouth, to form a seal. With this arrangement, the problem of the damage to the sealing face during the capping process is avoided. During the capping process the sealing section is in the initial position and it is actuating part which engages with the container mouth, not the sealing part. Therefore, damage to the container mouth can result in damage to the actuating part, but not in damage to the sealing part, which is different from the actuating part. In the course of the capping process the sealing section is tilted from its initial position towards its sealing position. When the closure cap has been put on completely, the sealing section is in the sealing position. Only at this point in time does the sealing part of the sealing section come into engagement with the container mouth, ensuring that a seal is formed between the undamaged sealing part of the sealing section and the container mouth. According to a preferred embodiment of the invention, the sealing part of the sealing section has a convex sealing face. In the sealing position, the sealing lip according to this embodiment seals in a similar way to a conventional olive seal. However, damaged parts of the sealing section are not in contact with the container mouth, owing to the tilting of the sealing section. The actuating section is used to trigger the tilting movement. The actuating section has an essentially straight or concave lead part. The lead part then merges, preferably continuously (i.e. without steps), into the sealing face of the sealing section. In the initial position the sealing section preferably extends more or less radially outwards from the root section. The root section may be provided with a supporting shoulder, which supports the sealing section more or less in its initial position, until the sealing section comes into engagement with the container mouth during the capping process and at the same time is tilted. The present invention will now be explained in more detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 - shows a cross section through a closure cap according to a first embodiment of the invention. Figure 2 - shows an enlarged representation of the sealing lip shown in Figure 1, in cross section. Figure 3 - shows a cross section through the closure cap shown in Figure 1, after it has been applied to a container mouth (represented by a dashed line) . Figures 4 to 6 - show representations of sealing lips according to alternative embodiments of the invention, in cross section. Figures 7 to 9 - show schematic, cross section representations of an alternative embodiment of a closure cap according to the invention, at various stages during the capping process. Figures 10a to 10c - show enlarged representations of the sealing lip shown in Figures 7 to 9. Figure 11 - shows a schematic representation of the effect of a supporting shoulder on the sealing lip shown in Figures 7 to 10. Referring to Figures 1 to 3, the closure cap 1 according to the invention consists of a top plate 2 and a skirt 4. The skirt 4 extends from the edge 3 of the top plate 2. The skirt 4 is provided with an internal thread 13, by means of which the closure cap 1 can be attached to a container mouth 30 (see Figure 3) . To obtain a seal between the closure cap and the container mouth, the closure cap 1 is provided with a sealing lip 5. The sealing lip 5 consists essentially of a root section 6 and a sealing section 7. The root section 6 is substantially cylindrical and extends from the inside of the top plate 2. The sealing section 7 takes the form of a truncated cone. The sealing section 7 extends from the end 10 of the root section 6 furthest away from the top plate 2. The sealing lip 5 is provided with a continuous groove 8. The groove 8 is arranged between the root section 6 and the sealing section 7. The groove 8 provides a material weakening in the sealing lip 5 and increases the tiltability of the sealing section 7 in relation to the root section 6. The groove 8 defines a joint between root section 6 and sealing section 7. In the embodiment according to Figure 1, the groove 8 is continuous and is located on the surface of the sealing lip 5, in particular in the face of the sealing section 7, turned away from the top plate 2. Moreover, the closure cap 1 is provided with additional elements well-known to the man skilled in the art. In particular, the closure cap 1 may have a guarantee band 14, with retaining elements 15, which can be brought into engagement with complimentary retaining elements on a container. In addition to the sealing lip 5 additional sealing lips 12 may be provided. The sealing lips 12 provide sealing effects on additional surface sections of a container mouth, enhancing the sealing performance of the closure cap. Figure 2 shows an enlarged representation of the sealing lip 5. The continuous groove 8 is defined on the surface of the sealing section 7 facing away from the top plate 2. The groove 8 lies in or radially outside a cylindrical plane Z, which is formed by the outer face 11 of the more or less cylindrical root section 6. Consequently the sealing section 7 can tilt relatively easily with respect to the comparatively inflexible root section 6. The thickness of the sealing section 7 is reduced in the area of the groove 8. In the area of the groove 8 the thickness d is about 0.4 mm whereas the thickness D of the remainder of the sealing section 7 is about 0.6 mm. The root section 6 has a length L of about 3.5 mm. The sealing section 7 is formed somewhat shorter, with a length 1 of 2.8 mm. The result of this is that the sealing section 7 preferably adjoins a cylindrical inner face of the container mouth 30 (see Figure 3) . In Figure 3 the closure cap is shown applied on a container mouth 30. During the capping process, the sealing section 7 comes into engagement with the upper edge of the container mouth 30 . As the closure cap is screwed-on further, the sealing section 7 swings upwards around the joint formed by the groove 8 (as shown in Figure 3) . In contrast to conventional trumpet seals, the buckling line of the sealing lip 7 can be precisely predefined. Consequently the surface area 32, in which the sealing section 7 adjoins the inner face 31 of the container mouth, can be precisely predetermined. Likewise the instant at which the sealing section 7 breaks the sealing engagement with the inner face 31 of the container mouth during unscrewing, can be predetermined. The tiltability of the sealing section 7 gives the closure cap a certain elasticity. The closure cap is made of plastics material, typically polyethylene or polypropylene. The frusto-conical sealing section 7 extends at an angle α to the screwing axis of the closure cap (see Figure 2) . The angle α is about 30° in the embodiment shown. Alternative embodiments of the invention are shown in Figures 4 to 6. Figure 4 shows a sealing lip 5 constructed similarly to that shown in Figures 1 to 3 (inner seal) , but arranged as an outer seal. The sealing section 7 extends radially inwards from the end 10 of the root section 6 furthest away from the top plate 2. A groove 8 is arranged radially within the cylindrical face Z formed through the middle 11 of the root section 6. According to the embodiment shown in Figure 5, the material weakening is provided by a groove 9, which is arranged on the surface of the sealing section 7 turned towards the top plate 2. The groove 9 is arranged outside the cylindrical face Z v formed through the middle 11 x of the root section 6 in the region of the line of intersection between the outer face 11 of the root section 6 and the adjacent surface of the sealing section 7. Figure 6 shows a similar embodiment to those shown in Figures 2 and 5. However, instead of a continuous groove, the material weakening is provided by individual recesses, which are arranged in segments. The segmentlike recesses 18 are arranged outside the cylindrical face Z through the middle of the root section 6 and define a precise buckling line. However, the contact force of the sealing section 7 against the inner face 31 of the container mouth 30 is reduced in the region of the recesses 18, in comparison with the contact force between the recesses 18. Therefore, gas blow-off (venting) occurs first in the region of the recesses 18. This allows a precisely defined venting behaviour to be obtained. The root section 6 is generally designed to be relatively stable. For this purpose, a thickness T of 1.0 mm for example is chosen. The invention can be applied to other sealing lip arrangements not shown in detail. It is essential that a material weakening leads to an uncoupling between a tiltable sealing section and a relatively stable root section. An alternative embodiment of the invention is shown schematically in Figures 7 to 11. The closure cap 1 according to this alternative embodiment, has a top plate 2 and a skirt 4, which extends from the edge 3 of the top plate 2. The closure cap has a continuous sealing lip 35. The sealing lip 35 consists of a root section 36 and a sealing section 37. The sealing section 37 is tiltably connected to the root section 36 via a joint 43 (in the same manner as previously described in relation to Figures 1 to 6. Figure 7 shows the sealing section 37 in its initial position I, at the start of the capping process . The sealing section 37 has a sealing part 38 and an actuating part 39. The actuating part 39 is provided with a lead face 40. The sealing part 38 is provided with a convex sealing face 41. During the capping process, the actuating part 39 with the lead face 40 comes into contact with the upper edge 33 of the container mouth 30. Damage B v to the upper edge 33 of the container mouth 30 can result in damage B to the lead face 40 (see enlarged representation in Figure 10a) . In its initial position I, at the instant when the closure cap 1 is put on to the container mouth 30, the sealing face 41 is not in contact with the container mouth 30, in particular with the damaged upper edge 33 of the container mouth. The sealing lip 35 is provided with a supporting shoulder 42. The supporting shoulder 42 prevents the sealing section 37 dropping down when the sealing section 37 is not yet in engagement with the container mouth 30. The supporting shoulder 42 thus ensures that during screwing on of the closure cap, the actuating part 39 comes into engagement with the container mouth. Additionally, the closure cap 1 may be provided with an outer seal 44. Figure 8 shows the closure cap 1 as the capping process continues further. As the closures cap continues to be screwed on, the sealing section 37 is tilted around the joint 43. The sealing section 37 with the lead face 40 slides over the upper edge 33 of the container mouth 30. Therefore, any damage which occurs is located in the region of the lead face 40 and consequently outside the sealing face 41. Figure 9 shows the closure cap 1 fully screwed on. The sealing section 37 is situated in a sealing position S. The sealing face 41 of the sealing part 38 lies sealingly adjacent to a sealing face 32 of the container mouth 30. The damage B (see Figure 10c in the region of the lead face 40) is situated above the sealing face 41. Therefore, the damaged portion B of the sealing section 37 does not provide the seal contact with the inside of the container mouth 30. It is obvious from Figures 9 and 10c, that the damage B does not lead to an impaired seal. Thanks to the tilting of the sealing section 37 during the capping process, the contact area between the sealing section 37 and the container mouth 30 moves during the capping process from the lead face 40 (which can be damaged as the closure cap is screwed-on) to the intact sealing face 41, which is undamaged. The stages represented Figures 7 to 9 are shown in enlarged representations in Figures 10a to 10c. Damage B" on the upper edge of the container mouth 30 (for example, caused by splintering in the case of glass or PET bottles) can lead to damage B in the region of the lead face 40. However, as the capping process progresses (see Figure 10b) , the sealing section 37 is tilted. Any further damage arises between the sealing face 41 and the lower end 45 of the sealing section 37, but the sealing face 41 remains undamaged. Figure 10c shows the sealing section 37 in its sealing position S, with the intact sealing face 41 making contact with the inside surface of the container mouth 30 to provide a good seal. The sealing face 41 is convex whilst the lead face 40 has a straight and a convex section. The convex sealing face 41 facilitates smooth unwinding of the sealing part 38 over the inner surface of the container mouth 30. The lead face has a straight section 46 adjacent to the free end 45 of the sealing section 47 (see Figure 10a) . The actuating part 39 with the straight section 46 (or with a concave section 47 which adjoins the straight section 46) is the first part of the sealing section to come into contact with the container mouth 30 (see Figure 10a). The concave section 47 merges continuously into the convex sealing face 41, to facilitate smooth unwinding of the sealing part 38 as the closure cap is applied to the container. Figure 11 illustrates the effect of the supporting shoulder 42. Before the sealing section 37 comes into engagement with the container mouth 30, the supporting shoulder 42 prevents the sealing section 37 dropping down in the direction of the arrow. The expressions convex and concave as used in this description relate to the outer shape of the sealing lip seen in a cutting plane through the central axis of the sealing cap.

Claims: CLAIMS 1. A closure cap (1) of plastics material for closing a container mouth (30), comprising a top plate (2) , a skirt extending from the edge (3) of the top plate (2) and at least one sealing lip (5), the sealing lip (5) having a root section (6) and a sealing section (7), wherein the root section (6) is joined to the closure cap (1) and the sealing section (7) is adapted to press against a sealing face (32) on the container mouth (10), characterised in that the sealing section (7) is substantially frusto- conical and extends from the end (10) of the root section (6) furthest away from the top plate (2), and the sealing lip (5) has a material weakening (8, 9, 18) between the root section (6) and the sealing section (7), such that the sealing section (7) tilts about the material weakening (8, 9, 18) as the closure cap (1) is applied to the container mouth (30) . 2. A closure cap according to claim 1, characterised in that the root section (6) is substantially cylindrical and extends from the top plate (2). 3. A closure cap according to ^ claim 1 or claim 2, characterised in that the material weakening (8,9) is continuous around the circumference of the closure cap (1) . 4. A closure cap according to any of claims 1 to 3, characterised in that the material weakening is segmented and the material weakening segments (18) are arranged at a distance to one another around the circumference of the closure. 5. A closure cap according to any of claims 1 to 3, characterised in that the material weakening takes the form of a groove (8, 9) on a surface of the sealing lip (5) . 6. A closure cap according to claim 5, characterised in that the groove (8) is arranged on the surface of the sealing lip (5) facing away from the top plate (2) . 7. A closure cap according to any of the preceding claims, characterised in that the sealing lip (5) is arranged as an inner seal, wherein the sealing section (7) extends radially outwards from the root section (6) and the material weakening (8, 9) is arranged radially outside the cylindrical face (Z) running through the middle (11) of the root section (6). 8. A closure cap according to any of the claims 1 to 6, wherein the sealing lip (5) is arranged as an outer seal, characterised in that the sealing section (7) extends radially inwards from the root section (6), and the material weakening (8, 9) is arranged within the cylindrical face (Z') running through the middle (11') of the root section (6). 9. A closure cap according to any one of the preceding claims, characterised in that, in the region of the material weakening (8, 9, 18), the sealing lip (5) has a thickness (d) of 30% to 90%, advantageously about 2/3 of the thickness (D) of the sealing section (7) . 10. A closure cap (1) of plastics material for closing a container mouth (30), comprising a top plate (2), a skirt (4) extending from the edge (3) of the top plate (2) and at least one sealing lip (35), the sealing lip (35) having a root section (36) and a sealing section (37), wherein the root section (36) is joined to the closure cap (1) and the sealing section (37) is connected to the distal end of the root section (36) and is adapted to tilt between an initial position (I) and a sealing position (S) where it presses against a sealing face (32) on the container mouth (10), characterised in that, the sealing section (37) comprises a sealing part (38) having a convex sealing face (41) and an actuating part (39) different from the sealing part (38), wherein in the initial position (I) the actuating part (39) is arranged to engage with the rim (33) of the container mouth (30) and thereafter, the sealing lip (35) tilts to its sealing position (S) and the convex sealing face (41) of the sealing part (38) presses against the sealing face (32) of the container mouth (30) . 11. A closure cap according to claim 10, characterised in that, the actuating part (39) has a lead face (40) with an essentially straight section (46) and/or a concave section (47). 12. A closure cap according to claim 10 or claim 11, characterised in that the lead face (40) merges continuously into the sealing face (41) . 13. A closure cap according to any one of claims 10 to 12, characterised in that in its initial position (I), the sealing section (37) sticks radially outwards from the root section (36) . 14. A closure cap according to any one of claims 10 to 13, characterised in that the root section (36) has a support shoulder (42), arranged to hold the sealing section (37) substantially in its initial position.

Inventors: BOSL UDO, DREYER LINO, SIMMEN ERICH, BOSL, UDO, DREYER, LINO, SIMMEN, ERICH
Applicants: BOSL UDO, CROWN CORK & SEAL TECH CORP, DREYER LINO, METAL BOX PLC, SIMMEN ERICH, BOSL, UDO, CARNAUDMETALBOX PLC, CROWN CORK & SEAL TECHNOLOGIES CORPORATION, DREYER, LINO, SIMMEN, ERICH
Application year: 2000
Main classification: B65D41
IPC codes: B65D41