The invention relates to a snap cap for closing a receptacle, said snap cap having a deck, which in use covers an end of the receptacle, and furthermore having a circumferential skirt extending from the deck and having a free end remote from the deck, the circumferential skirt having an inner side on which a snap bead is formed to attach the snap cap to an end ridge of the receptacle, the deck having an outer ring shaped zone which extends radially from an outer periphery of the deck and the deck having radially inward from the outer ring shaped zone an elevated ring shaped or circular zone which is elevated with respect to the outer ring shaped zone.

Such snap caps are known, for example for capping coffee cans containing ground coffee, and are made of thermoplastic materials.

In the current times a goal is producing more sustainable products. In the case of plastic snap caps, one way of producing in a more sustainable way is to reduce the amount of material used for producing. In general this will lead to reduced wall thicknesses. The snap cap is placed on the receptacle in an automated capping line. The caps are fed to the capping line in stacks and are then destacked and placed in a line on a conveyor track, wherein the caps push each other forward. Thin-walled caps cause more failures in such a capping line than conventional caps.

The present invention has for an object to provide a thin-walled snap cap which overcomes the problems in the capping lines.

This object is achieved by a snap cap according to the preamble of claim 1, wherein at the outer periphery of the deck a peripheral rim is formed which protrudes from the deck and which has a free end, wherein the free end of the peripheral rim is elevated with respect to the outer ring shaped zone.

Usually snap caps are provided to the capping line in stacks of caps, after which they are destacked an placed in line. The free end of the skirt of an upper cap rests on the outer ring shaped zone of the lower cap. Advantageously the peripheral rim provides a radial retainment of the free end of the skirt of the upper cap, whereby is prevented that the skirt of the upper cap slides of the deck of the lower cap. This prevents failures in feeding the caps to the capping line. Moreover, the elevation provided by the peripheral rim also reduces the tendency of one cap sliding over an adjacent cap while the caps push against each other when they are conveyed in the capping line.

The peripheral rim has an advantageous effect on the rigidity of the cap. Thereby the cap has in general has a reduced tendency to deform when it is pushed forward in a capping line where caps are arranged in a line wherein the one cap pushes the other cap in the conveying direction. However, the peripheral rim itself is flexible and can deform when in line and pushing against another peripheral rim in the line. Thereby the skirts of consecutive caps in the line can engage each other, which provides the caps in the line the same behaviour as conventional snap caps, when pushed forward in the capping line.

In an embodiment of the cap the peripheral rim has a conical radially inward facing surface. This conical surface that faces inwardly in the radial direction guides the free end of the skirt of the cap above to the surface of the outer ring shaped zone. Thus the free end of the skirt of the cap above is maintained well in position, whereby the stack of caps remains straight upwardly and stable.

In a further embodiment the peripheral skirt has a recess at the free end, which recess has a smaller outer diameter than the inner diameter of the inwardly facing surface of the peripheral rim. The recess at the free end of the skirt and the inwardly facing surface of the peripheral rim cooperate and improve the stability of the stacked caps.

In an embodiment the peripheral rim flares radially outward with respect to the circumferential skirt. The flaring peripheral rim does not only provide the conical radially inward facing surface, but also reduces the tendency of one cap sliding over an adjacent cap while the caps push against each other when they are conveyed in the capping line. Moreover, it provides an increase in rigidity of the cap whilst a minimal use of additional material is used. Advantageously the flaring rim is flexible, such that it can be pushed inward locally when in line with other caps in the capping line, such that skirts of consecutive caps can engage each other and the caps thereby behave the same in the line as conventional caps without such a rim.

In an embodiment the elevated ring shaped or circular zone has an outer diameter which is adapted to substantially mate with a bottom side of a receptacle thereby facilitating stacking of capped receptacles. Stacking of capped receptacles is useful during transport, storage or display in a store. In an embodiment the deck has said elevated ring shaped zone, and has a recessed central circular zone which is on a level below the outer ring shaped zone. The recessed central circular zone provides additional rigidity to the cap, which reduces deformation and the risk that such deformation causes the caps in the capping line to slide over each other and jam the line.

The snap cap according to the invention is made by an injection moulding process of a thermoplastic material, preferably a PE. A suitable material was found to be a blend of HDPE and LDPE. The deck may have a thickness within a range 0,3 - 0,7 mm, preferably within a range 0,4 mm - 0,6 mm, preferably about 0,5 mm. The skirt may have a thickness within a range 0,3 - 0,7 mm, preferably within a range 0,4 mm - 0,6 mm. Of course the thickness of the skirt is larger at the snap bead and does not have to fall within this range.

The cap may have a diameter within a range of 70 mm - 160 mm, depending on the particular receptacle it is combined with. In a particular embodiment the skirt has an outer diameter of about 130 mm, which leads to a weight of the cap of about 8,3 g. In another particular embodiment the skirt has an outer diameter of about 99 mm, which leads to a weight of about 5,5 g. These snap caps may be considered lightweight. Also particular embodiments having other diameters are foreseen, such as 153 mm or 70 mm.

The invention also relates to an assembly of a receptacle having an upper end ridge near an open upper end of the receptacle and a snap cap as described in the above.

The invention furthermore relates to a method for capping a receptacle with a snap cap as described in the above, wherein:

- the snap caps are provided to a capping line in a stack;

- the snap caps are destacked and placed one after the other in a conveying line, in which the caps push against each other in a radial direction; and

- the snap caps are taken individually from the conveying line and placed on the receptacle.

The invention also relates to a capped receptacle, wherein the recepticle is capped with a snap cap of the type as described in the above.

The invention also relates to a stack of such capped receptacles. The invention will be elucidated in the following description with reference to the drawings, in which:

Fig. 1 shows a cross section of a snap cap according to the invention,

Fig. 2 shows a detail of the cross section of Fig. 1,

Fig. 3 illustrates in cross section a stack of caps of Fig.1 ,

Fig. 4 illustrates caps of Fig. 1 arranged in line in a capping line,

Fig. 5 illustrates in cross section how capped receptacles are stacked, and

Fig. 6 illustrates in isometric view the stacking of capped receptacles.

Fig. 1 shows a snap cap 1 for placement over an open upper end of a receptacle. The receptacle is generally a cylindrical receptacle with a closed bottom and an open upper end. The snap cap 1 has a deck 2, which in use covers the open upper end of the receptacle. The snap cap 1 furthermore has a circumferential skirt 3 extending from the deck 2 and having a free end 31 remote from the deck 2. The circumferential skirt 3 has an inner side 3A on which a circumferential snap bead 5 is formed to attach the snap cap 1 to an upper end ridge of the receptacle. In case of a cylindrical receptacle, the skirt 3 can also be substantially cylindrical as is the case in the embodiment shown in Fig. 1.

The deck 2 has an outer ring shaped zone 21 which extends radially from an outer periphery of the deck. The deck furthermore has, radially inward from the outer ring shaped zone 21, an elevated ring shaped zone 22, which is elevated with respect to the outer ring shaped zone 21. The deck 2 has a recessed central circular zone 23 which is on a level below the outer ring shaped zone 21. The height transitions between the zones 21 , 22 and 23 provide the cap with a higher rigidity. In a possible embodiment, which is not shown in the figures, the recessed circular zone 23 may be omitted, whereby instead of an elevated ring shaped zone 21 the cap has an elevated circular shaped zone.

At the outer periphery of the deck 2 a peripheral rim 24 is formed which protrudes from the deck 2 and which has a free end 24A (cf. Fig. 2). The free end 24A of the peripheral rim 24 is elevated with respect to the outer ring shaped zone 21. In other words the free end 24A of the peripheral rim 24 is spaced apart from the surface of the rings shaped zone 21 in an axial direction of the snap cap 1. The peripheral rim 24 extends in a direction away from the skirt 3; i.e. if the skirt 3 is extending downward, which is the case during normal use, when placed on a receptacle, the peripheral rim 24 extends upwardly, albeit not under an angle of 180° (in line) with respect the skirt 3, but a smaller angle. The peripheral rim 24 flares radially outward with respect to the circumferential skirt 3. The peripheral rim 24 has a conical radially inward facing surface 24B (cf. Fig. 2).

At the free end 31, which during normal use is the lower end, the peripheral skirt 3 has a recess 32, which recess 32 has a smaller outer diameter than the inner diameter of the inwardly facing surface 24B of the peripheral rim 24. In the embodiment shown in the figures the recess 32 has a chamfering shape.

In Fig. 3 a stack of snap caps 1 is illustrated. Usually snap caps 1 are provided to the capping line in such stacks of caps 1 , after which they are destacked an placed in line (cf. Fig. 4). The free end 31 of the skirt 3 of an upper cap rests on the outer ring shaped zone 21 of the lower positioned cap 1. Advantageously the peripheral rim 24 provides a radial retainment of the free end 31 of the skirt 3 of the upper cap 1 , whereby is prevented that the skirt 3 of the upper cap 1 slides of the deck 2 of the lower cap 1. This prevents failures in feeding the caps 1 to the capping line.

The conical surface 25B that faces inwardly in the radial direction guides the free end 31 of the skirt 1 of the cap 1 positioned on top of it to the surface of the outer ring shaped zone 21. Thus the free end 31 of the skirt 3 of the cap 1 above is maintained well in position, whereby the stack remains straight upwardly and stable. The recess 32 at the free end 31 of the skirt 3 and the inwardly facing surface 24B of the peripheral rim 23 cooperate and improve the stability of the stacked caps 1.

The peripheral rim 24 is flexible. When the caps 1 are destacked an placed in line to be conveyed one after the other, the skirts 3 of consecutive caps 1 are pushed against each other. In the cap 1 according to the invention the peripheral rim 24 can be deformed inwardly due to its flexibility, such that the skirts 3 can indeed engage each other. This is illustrated in Fig. 4 and indicated by an arrow. The caps 1 are moved by a endless conveying element 6 underneath a plate 7.

The snap cap 1 is placed over an open upper end of a receptacle 8 as is shown in Figs 5 and 6. The deck 2 covers the open upper end of the receptacle 8. The snap bead 5 formed on the inner side of the skirt 3 attaches the snap cap 1 to an upper end ridge 82 of the receptacle 8. The elevated ring shaped zone 21 has an outer diameter which is adapted to substantially mate with a bottom end ridge 81 of a receptacle 8 thereby facilitating stacking of capped receptacles (cf. Figs 5 and 6). Stacking of capped receptacles is useful during transport, storage or display in a store.

The snap cap 1 according to the invention is made by an injection moulding process of a thermoplastic material, preferably a PE, e.g. a blend of a HDPE and a LDPE. The deck 2 may have a thickness within a range 0,4 mm - 0,6 mm, preferably about 0,5 mm. The skirt 3 may have a thickness within a range 0,4 mm - 0,6 mm.

The cap 1 may have a diameter within a range of 80 mm - 140 mm, depending on the particular receptacle it is combined with. In the particular embodiment shown in the figures, the skirt 3 has an outer diameter of about 130 mm, which leads to a weight of the cap 1 of about 8,3 g, which may be considered lightweight.