WO2002002429A1

WO2002002429A1 - Cap comprising a release indicator for a container

Info

Publication number: WO2002002429A1
Application number: PCT/NL2001/000512
Authority: WO
Inventors: Louis Rinze Henricus Willemsen
Original assignee: Weasy Pack International Ltd.
Priority date: 2000-07-06
Filing date: 2001-07-05
Publication date: 2002-01-10
Also published as: EP1301413A1; US20040020889A1; AU2001271141A1

Abstract

The invention relates to a cap (1) for an airtight container such as a glass or plastic bottle or jar, which cap is suitable to be placed releasably in a closing position on a neck (6) of the container, wherein the cap is provided with visual indicating means (5) for indicating that the cap is no longer in the closing position, wherein the indicating means are adapted to be brought into an active state when the cap is arranged on the neck of the container and to be brought into the indicating state when the cap is removed. These measures have the result that the indicator only becomes active, i.e. enters into the indicating state, when this state is preceded by an active state. The fact that it has to be successively subjected to two different states makes it easier to find such an indicator; use can after all be made of indicating means which are not normally active, for instance in the stored situation, and which are only activated by arranging thereof on the neck of the container.

Description

OJ M M (->

O (_π O C l o Cπ α

F- o tx

F-

Φ d> s α

≤, pi rt

Φ

H

.

H 3 tr tr Φ F- TJ Ω F- ≤ rt Ω α 3 ft⁾ D ft⁾ F- ft⁾ CΛ ≤ F- ι-3 CΛ O F- ft⁾ ≤ 3 F-

O Φ o o 3 3 r~> O 3 t tr ft⁾ Φ ft⁾ hi φ Ω 3 H ft 3" 3 F- tr rt 3 ω 3 tr Φ 3

O Ω s: rt <i ft⁾ 3 F- Φ TJ ιQ 3 hi Ω rt α hi o F- P- Hl Φ ft⁾ -¹ Φ . ft⁾ <!

Cfl ? Φ rt Φ F- Ω 3 F- Ω hj 3 ft⁾ t F- F- ft⁾ hi Ω F- Hi rt > hi 3 3 Φ φ <! H Ω Φ Φ Ω tr ft⁾ F- Φ Φ 3 Ω 3 Φ r Ω φ Hi Φ φ ft CΛ 3

3 o Φ Φ O ft⁾ r-3 α Ω ft⁾ > hi Cfl Φ hi i£3 > o Φ ft> ιQ α ft⁾ H ft⁾ tr 3 3 o rt ft H

Φ Hi hi TJ ft tr ft rt Ω F- hi F- h-¹ Hi rt Ω F- ft⁾ rt φ Ω Φ tr o tr PJ F- 3 α 0 Φ 0 φ o F- F- Ω rt ft⁾ Hi o P rt CO F- Ω 3 to hi 0 P rt s: Ω φ <l σ φ H O rt hi hi 3 O 3 O 3 O Hi Hi ιQ tr rt rt 3 O ιQ F- Φ H rt tr O Cfl φ Φ Φ 3 O

F- tr d F- F- 3 vQ hi F- ιQ d O o tr ft⁾ ιQ hi ft rt φ 3 φ α Ω hi

Cfl φ Φ <_ι. CO s: 3 ft α co Φ 3 3^* hi O d Φ rt α ft d 3 Cfl tr 3 φ tr ft) ft⁾ TJ ft⁾ tr tr s: 3 F- 3 d hh iQ Φ 3 F- tr ft⁾ O d rt ft⁾ CO 3 hi TJ H Φ rt tr rt H tr F- F- φ tr Φ 3 TJ φ 3 F- tr Ω Φ 3 Φ rt ft Cfl ft⁾ rt ft Φ o o) O hi

3^* o O • hi Ω Ω F- ft⁾ ιQ O 3 rt F- 3 ft o ≤ ft⁾ >£i hi F- φ rt tr ft⁾ ft⁾ d F- TJ <l

Φ rt O 3" ft⁾ 3 Ω 3 to rt o α O tr F- 3 ^{^} 3 φ O 3 Φ F- F- Ω CO ιQ co rt F- ft rt ft H rV rt Φ tr to rt Cfl p. riφ rt rt Φ Cfl rt o 3 O Ω CO rt Cfl ft d tr Φ α o

Φ h-¹ - Φ F- F- Ω O F- O tr rt ft⁾ ft⁾ 3 O hh ^ hi ft⁾ F- H rt ft⁾ Φ

3 Φ Φ φ 3 to 3 ?V F- ft tr hh Φ ^ 3 Ω F- F- ft⁾ 3 3 3 tr Cfl <t Φ hi CΛ o

<! ιQ CΛ tr ft⁾ H Ω ft⁾ CO 3 ft hi ft⁾ o ft⁾ ft⁾ ft⁾ ft⁾ rt Φ Cfl F- hi rt tr

Φ TJ φ Φ O Φ φ rt ft⁾ ft⁾ Φ TJ Φ tr Φ 3 3 ft) t^r O ft! 3 ft⁾ o CO <t

H Clf hi 3 d 3 3 Hi ft⁾ hi Cfl ^* 3 3 TJ hi Φ H, h φ rt ¹ ft 3 d F-

O o Φ hj Ω φ α φ Φ ft Φ tr O O • ft⁾ F- ft ^ rt CO rt Φ F- ft⁾ . o iQ tr Ω ft)

TJ CO Φ F- h-¹ ft⁾ rt ft⁾ Hi Ω o Q^j ^■ 3 CO Ω hj tr ^■s, Φ o • <! Φ Φ tr rt

Φ rt Φ 3 0 3 tr TJ o O Ω rt ft Cfl ft⁾ ft⁾ Cfl φ tr ft⁾ hi F- F- Φ Φ rt α Φ tr 3 0 ιQ Cfl CO Φ rt hi 3 TJ ft⁾ rt tr rt rt F- TJ TJ ft F- Ω ft tr Cfl • tr tr ft⁾

3 ft⁾ Ω J φ Φ Φ α φ TJ hi Φ tr tr tr rt 3 Ω ft ft⁾ Φ rt φ o H rt

O rt Φ Φ ft⁾ α Ω Ω α hi _• ft⁾ Φ Φ H F- Φ TJ Φ 3" F- φ TJ Φ tr 3 o Ω 3- hi ft⁾ o Ω TJ Hi Ω Φ fl hi Ω <1 ft⁾ CO hi 3 Φ F- d ft⁾ φ

H O O F- H F- 3 3 rt O H O ft⁾ rt F- TJ tr Φ rV ft⁾ φ CO d Φ ft 3 rt ιQ TJ CO

O 3 Hi Cfl ft⁾ 3 rt o 3 φ hi F- t hi 0 F- rt Hi hi - tr F- Ω Ω Φ hi tr tr Φ

3 h-¹ 3 Hi ft⁾ TJ Hi 3 3 Φ Φ rt 3 F- o Φ O Φ Φ Φ Ω Φ H Φ F- Φ rt Q ft ft ιQ ft⁾ O F- tr hi Φ 0 Φ CO rt Cfl hi Hi hh hi φ CO to Ω s: TJ

Φ tr - F- 3 hj 3 Φ F- hi ft> <l Φ H TJ TJ tr hi O O 3 Cfl Φ d ft) 3 F- 3" hi hi ≤ Φ Φ 3 Φ Cfl H φ 3 ft 3 Φ H Φ Φ ft 3 hi ft⁾ ft CO a F- h-¹ rt Φ 3 Φ 0

3^J 3 ιQ Φ F- hi tr Φ Φ 3 3 Φ tr Ω F- ft⁾ α tr H o F- 3 rt F- Ω rt H tr tr Φ d 3 3 • hi φ φ ft φ Φ O 3 Ω tr Φ ^■ F- Φ <! tr ft 3 rV O φ -¹

Φ 3 TJ CO O <i Cfl O ft⁾ Ω 3 tr hi Ω Φ H Φ 3 h φ • O rt tQ F- Φ -¹ TJ rt Hi Φ rt rV φ tr rt o O F- α o 3 Ω ft⁾ Cfl o F- H tr o ft⁾ 3 3 rt φ F- h-¹ ft) Φ 3 3 ft⁾ F- Hi ι_ι. TJ d tr o Ω rt Hi 3 ^ ft⁾ ft ft⁾ CΛ Hi 3 CO tr hi (-^■ rt O 3 3 Φ cr 3 rt Cfl ft⁾ hi tQ o 3 ft ft⁾ α 3 tr rt ft rt

Hi Φ h-¹ tr TJ Ω Ω o F- ft⁾ o TJ ft hi Φ Φ tr rt F- 3 F- CΛ φ ft⁾ rt ft⁾ tr rt ft⁾ Φ Φ Φ Φ s: - α Ω Hi h-¹ Φ -¹ rt F- ft⁾ <! Ω 3 CO d ft⁾ rt ft tr Ω Φ tr

Cfl Ω 3- tr ft⁾ F- ft⁾ Φ ft⁾ 3 F- ft si 3 F- ft⁾ Φ α d tr Ω F- 3^" Φ Φ ft Φ rt ft⁾ ιQ Φ Ω Ω Φ 3 3 H CO F- Ω TJ 3 O rt F- Φ 3 rt F- Ω ι_ι. rt 3 Φ F- F-

TJ φ H ft⁾ s: O 3 F- Φ 3 Φ Φ F- 3 3 Φ Φ F- Ω ' tr Φ F- . s: Ω <i 3 TJ α TJ tr 3 Ω 3 ft⁾ TJ 3 hi O α <l ft ft hi 3 ft⁾ Ω <! F- F- tr O Φ hi ft) F- o Φ TJ rt ft⁾ ft Ω h-¹ F- Φ ft⁾ ft Φ Φ O • ft rt Φ Ω 3 Φ 3 F- Φ

3 Cfl Hi Hi O hi hi tr rt ft⁾ Ω 3 rt tr rt rt σ ft F- 3 Φ ft⁾ CL 3 rt Cfl Ω Cfl

Q. F- 3 Φ F- Φ rt F- Ω ft⁾ rt d Φ Φ rt rt 3^* ^><: tr 3 CO ft F- ft⁾ rift⁾ Φ rt X F- CO tr O Φ rt h H Ω O 3¹ Φ Φ ιQ rt F- Ω rt F- ft⁾ ft 3 rt tr Φ rt 3 Φ Ω Φ 3 F- O φ rt Φ ^• rt ft⁾ 3 ft⁾ tr 3 rt F- rt tr φ α tr ft⁾ • St 3 Hi •_^ ft 3 O rt ιQ ft Φ Φ Φ 3

Φ -- Φ rt ft⁾ TJ F- iQ rt tr Φ Φ O H iQ tr 3 rt rt tr φ ft⁾ rt hi Ω Φ F- tr tr φ 3 ft⁾ co Φ Cfl o TJ

environment in the form of nitrogen or oxygen is given the opportunity to reach the indicator.

According to another preferred embodiment the mechanical connection is formed by a limp element which is fixedly attached to the cap -on two sides and which is provided with a weakened portion at the position where the limp element makes contact with a component of the container when the cap is arranged on the container, and that the limp element is held fast at the weakened portion by the clamping between the cap and the neck of the container.

This measure also has the consequence that, when the cap is screwed on, the weakened portion of the limp element is destroyed, but that the limp element is held fast between the upper edge of the neck of the container and the cap and, as soon as the cap is unscrewed slightly, the limp element drops downward.

Other attractive preferred embodiments are stated in the remaining sub-claims . The present invention will be -elucidated hereinbelow with reference to the annexed figures, in which: figures LA-IC show partly broken-away, perspective views of a first embodiment of the invention at different stages; and figures 2A-2C show partly broken-away, perspective views of a second embodiment of the invention at different stages.

The invention is applicable in the first place to bottles with optionally carbonated soft drinks, beer and so on, but is also applicable to bottles with a different content, and to for instance glass jars which are closed by a lid.

The invention is elucidated in the following with reference to a bottle. It will be apparent that the same embodiment can also apply to glass jars. Drawn in figure 1 is a cap 1 which is manufactured for instance from plastic. Cap 1 is provided on the inner side of its skirt in the usual manner with a screw thread 2. Cap 1 can hereby be screwed onto neck 6 of a bottle. It is however not per se necessary that use be made of a screw-cap. The invention is also applicable to for instance caps arranged by means of a clamp connection or otherwise on the neck of a bottle; the invention is even applicable to crown caps, although here the use of the invention requires special provisions in respect of the visibility of the breaking of the seal.

Assuming that the cap is made from coloured plastic, a transparent window 3 is arranged in the top surface of the cap. The transparent window 3 gives a visual indication of the state of an indicator 5 arranged in an envelope 4 under window 3. Envelope^* 4 is for instance manufactured from a plastic film, which plastic film can be perforated by the upper part of the neck of a bottle when cap 1 is screwed onto such a bottle neck.

The indicator is formed by a substance which changes colour upon entry of a gas or a liquid normally to be found in the bottle. Assuming that the content of the bottle is formed by a soft drink, it is conceivable that an indicator is chosen which changes colour upon entry of carbon dioxide or water vapour and so on. The colour change of indicator 5 can then be observed through the window 3. It is also conceivable for the combination of envelope 4 and indicator 5 to be received in the "liner" which is usually present against the underside of the upper wall of a cap and which serves to provide adequate sealing. This liner is deemed as being arranged in cap 1 in the embodiment now being described.

o ≤ rt o o Cfl TJ rt ft⁾ rt o 3 to Hi hi tr hi hi rt F- tr rt F- rt Φ tr 3 Φ tr F-

O Hi F- tr hh Hi hi 3^J Cfl hi rt ft⁾ d H Φ -¹ Φ Φ hi rt -¹ O 3 tr 3 Φ ft) 3 o 3

≤: F" Φ F- Φ Φ ft⁾ tr 3 H Φ O- d Ω ft⁾ d Φ rt Co <! rt ft

Φ CΛ H rt ft ιQ hh F- 3 φ d hh p Φ Φ Φ 3 F- Φ d Hi Φ Φ rt O

<t rt tr tr tr tr Φ Hi rt CΛ hi Hi ft⁾ F- <J to CO Cfl 3 F- tr I-¹ φ ft⁾ M F¹

Φ hi 3 0 > Φ Φ rt hi CΛ F- TJ s: ft⁾ Ω tr H tr ft⁾ Cfl TJ rt Ft iQ o O ≤ φ 3 O Φ Ω •^ hi F- ft⁾ rt to ft⁾ ft i F- ft⁾ F- Ω Φ H 3 ft⁾ 3 Φ ft⁾ TJ O Φ rt £ rt J tr 3 TJ • O F- J ?T rt tr TJ 3 tr hi Cfl CΛ hi CΛ rt Φ Ω ri^¬ hi O hi hj rt φ φ Φ 3 iQ hi Φ F" CO o o Φ H F- rt φ φ d O rt ι*r Φ Cfl hi i j F- Φ H 3 rt F¹ H3 rid

Φ OD φ tr rt F- Ω >< TJ TJ 3 hi Hi TJ tr ιQ ft ft⁾ 3 Cfl Φ o Cfl Φ tr F- ι . tr ft⁾ ϋ

B Ω 0 rt a tr Φ 0 rt ft⁾ Φ H Φ H φ ft F- F¹ Ω Φ Λ •_^ F- 0 Φ ft⁾ o o rt ≤: H rt o^j hh CO CΛ F" α Ω ft⁾ O X rt tr • ft⁾ Ω O s: ft⁾ d to rt

F- 3 3 tr 3 Φ 3 F- & CΛ s: Cfl ft⁾ CΛ Φ d rt Φ ≤ F¹ O F- ft⁾ J rt F- s: F¹

3 ri^¬ φ • O F- X F- o F- F- o F- TJ ft 3 P ? F- Φ H α 3 H 3 O 0- tr £ s: Dd

0 ft⁾ F- Hi Ω Φ CΛ σ 3 3 F- CT s: rt 3 3 F- Ω F¹ ft⁾ F» TJ Φ TJ F-

Ω 3 Ω d 3 ft⁾ F- H α TJ ^■rt F¹ Ω O F- • α Hi CΛ Φ ιQ ft⁾ hi TJ rt ω

Φ rt TJ Ω H 3 3 φ o O Φ . s: F" O O O ft F- tr Φ F- CO rt Φ Φ tr tr ft⁾ TJ h O ft⁾ ft⁾ φ s: CΛ ιQ F- F- tr H H s: hi hi F- <l Φ α CΛ F- tr hj O

3 CΛ ≤ Φ F- 3 rt ιQ α 3 rt CΛ hi H CΛ 3 φ Hi α 3 ft) α rt • rt ≤

TJ F- F- hi ιQ ri^¬ Φ ft⁾ Φ ft O CO F- ft⁾ ft φ 3 σ CO ft⁾ Φ Ω tr hi tr CΛ Φ tr Φ tr ω φ α rt d ft⁾ 3 F- • tr ft⁾ 3 Φ rt hi rt F¹ φ » d Φ rt α φ α Φ tr TJ H Ω Cfl 3 O ft⁾ F- F" h-¹ F- H ft rt Ω tr Ω Φ F¹ tr o . tr ιQ tr ft⁾ Φ rt F- CO Hi TJ 3 Φ ^ fl H tr O F- F- O rt Ω Φ rt CΛ Hi TJ F- Φ £ O hh μ. CO hi O rt J ft⁾ CO φ 3 en 3 h-¹ O O Hi ft⁾ tr Φ o ω TJ ≤:

F- Cfl rt rt IV) =s 3 Φ h-¹ ft⁾ F- hh 3 3 3^* Φ rt O O Cfl Φ Λ tr CO ~j TJ

X H trj F- rt ft⁾ ^< 3 3 hi O ιQ o F- Hi O d ft⁾ O hj Φ d o F- F¹ φ Φ φ F- ~J rt O tr CΛ O rt Φ s. 3 <! O hi Ω d

TJ α d φ ri- rt ft⁾ s: H 3

Φ tr 3 Φ F- ft⁾ o rt 3 Φ 3 F- F- φ O hj rt • TJ 3 rt F- rt F- <!

CΛ o ≤; rt tr F- Cfl F¹ tr Φ tr J ft F^J O rt Φ Φ

^ rt CO Hi tr rt Φ tr ≤ tr F- rt O F- Ω F- F- 3 Ω φ CΛ Φ F" Φ 3 φ H α F¹ hj φ tr F- 0 tr φ Cfl hi tr 3 3 ft⁾ tr F- Ω h rt tr £ hi » hj iQ O o o rt 3 φ rt rt o hi ft⁾ Φ rt H Cfl tr O d ft⁾ F- Ω 3 O tr Φ TJ

3 ^ ≤ 3" tr Φ F" s: Φ 3 hi rt hh O Φ F- ft⁾ 3 3 tr Φ . £ Φ Hi tr φ Φ φ t Φ rt d φ ft⁾ H F- g O Φ 3^{^} F- H Hi Hi ¹ rt irj α α 3^{^} Ω φ hj ^1 rt α φ tr TJ hi O hj ^■ ; ω T TJ Φ ιQ F- O O Φ φ F- ft⁾ ιQ CΛ r"T rt Ω φ 4i. tr hi 3 Φ TJ Hi ft⁾ Φ 0 ft⁾ rt d Ω 3 hi F- (t Ω Φ Ω tr O F- O

Φ φ Φ Φ CΛ tr rt hi tr d hi tr F" O rt ft⁾ Λ hi CTi Φ 3 3 Hi O

CΛ tr Ω Ω hi F- Ω H hi Ω F- Φ ft⁾ 3 Φ ft⁾ hi F- tr Hi rt F- o Φ Φ Hi to rt < : r ft⁾ ft⁾ Φ ft⁾ o 3 3 rt 3 Φ 3 F- tr F- O O rt hh s: ft⁾ TJ CO Ω ft

F- H TJ J φ J 3 F¹ Φ rt φ t iQ Cfl tfl Φ Cfl h hj £ Φ 3 O ft) tr F- o- F- rt σ> ft⁾ 3 CΛ o 3 Ω hi Φ ri^¬ ft⁾ rt F- TJ d Φ 3

Φ J 3 F- hi ft⁾ F> ft⁾ TJ d rt TJ ft⁾ Cfl ft⁾ Cfl H ft⁾ hh OJ Ω F- Cπ rt 3" •_^ 3 φ Cfl

Φ o CΛ rt ri^¬ ri- ftl hi F¹ TJ F- φ 3 O hi O 3 F- Φ Φ rt hj φ 3 F-

F- CO Hi d φ hi φ rt ft⁾ α Cfl Ω ri- Ω hi hi H CΛ F- O rt 3 3 Φ Ω

3 ft⁾ CΛ O ft 3 hi Φ O Cfl F¹ Φ ft O rt Φ O rt' 3 3 3 tr <! O Φ Ω ft⁾

5t rt rt Ω Hi 3' F- 3 rt hi F" φ F- 3 d ft) Φ φ Φ hh ft⁾ ft) t rt

Λ F- rt tr H φ Φ ft⁾ rt Ω ft⁾ F- F- o F- O hi tr 3 US hi 3 A F- Ω H tr 3 O d F¹ ft⁾ Φ Φ (t hi H ft⁾ TJ Ω CΛ Hi TJ d Cfl h-¹ Cfl Φ Ω £ CΛ fr TJ o Ω F¹ ft) CTi H

Φ H Ω s: " TJ Ω TJ TJ hi d riα Ω Φ Φ ft⁾ TJ O Φ iQ to 3^* tr Φ Φ O ft⁾ ft⁾ ft⁾ ^ F¹ rt CO O Φ ft⁾ tr Cfl C hj Φ 3 Φ O cπ rt 3 o α CΛ 3 TJ ^ H 3^J rt 3 . •*» 3 d ft⁾ hh ft hi rt ri^¬ Hi Hi

F- φ rt 3 F- α ι_i- rt Φ O O Ω 3 3 hi F- ft⁾ O *. ft⁾ O rt Ω

O 3 rt o Φ ft F- d ft⁾ Hi ft⁾ rt Φ iQ O O H O • Ω hi O ft⁾ O

3 rt H 3 Ω F- 3 CO F- rt tr Φ Φ 3 3 3 Hi rt 3 Φ ft O rt fl O ft⁾ φ H φ o 3 TJ O

between the upper part 7 of the neck of the bottle and cap 1. When cap 1 is subsequently unscrewed, strip 8 will come loose as a result of its mechanical tension and hang downward. It is conceivable that the downward hanging of strip 8 is visible from outside. It is also possible here that due to the strip 8 falling away from the top side of cap 1 a text becomes visible by for instance integrating in cap 1 a foil in which are recessed the letters of the text. In the normal situation these letters are covered by strip 8, but the letters become visible when strip 8 falls away.

Here also the indicating means can be integrated into the liner, but can also be arranged separately under the liner.

Claims

1. Cap for an airtight container such as a glass or plastic bottle or jar, which cap is suitable to be placed releasably in a closing position on a neck of the container, wherein the cap is provided with visual indicating means for indicating that the cap is no longer in the closing position, characterized in that the indicating means are adapted to be brought into an active state when the cap is arranged on the neck of the container and to be brought into the indicating state when the cap is removed.

2. Cap as claimed in claim 1, characterized in that the indicating means are adapted to be brought into the active state when the cap is displaced relative to the neck of the container.

3. Cap as claimed in claim 2, characterized in that the indicating means comprise a mechanical connection which is adapted to be broken when ^'the cap is placed on the neck of the container.

4. Cap as claimed in claim 3, characterized in that the mechanical connection is arranged on the inner side of the cap, and that it is adapted to be broken by the upper edge of the neck of the container.

5. Cap as claimed in claim 3, characterized in that the mechanical connection is arranged on the underside of the skirt of the cap, and that it is adapted to be broken through by a collar extending on the outside of the neck of the container.

6. Cap as claimed in claim 3, 4 or 5, characterized in that the mechanical connection is formed by a limp element which is fixedly attached to the cap on two sides and which is provided with a weakened portion at the position where the limp element makes contact with a component of the container when the cap is arranged on the container, and that the limp element is held fast at the weakened portion by the clamping between the cap and the neck of the container.

7. Cap as claimed in claim 6, characterized in that the limp element is arranged under mechanical tension between its two attachment positions.

8. Cap as claimed in claim 3, 4 or 5, characterized in that the mechanical connection is formed by a seal of an envelope of an indicator, which seal is arranged at the position where it makes contact with a component of the container when the cap is arranged on the container, and that the component of the container covers the broken seal when the cap remains fastened on the container.

9. Cap as claimed in claim 8, characterized in that the indicator is adapted to change colour when it comes into contact with a gas or vapour present in the container.

10. Cap as claimed in claim 9, characterized in that the container is a soft drink bottle and that the indicator is adapted to change colour when it comes into contact with carbon dioxide.

11. Cap as claimed in any of the foregoing claims, characterized in that the cap is at least provided with a transparent window which is placed to show the indicator from a normal angle of view.

12. Cap as claimed in claim 11, characterized in that the window is provided with a text which is visible when the indicator changes colour.

13. Cap as claimed in any of the claims 8-12, characterized in that the indicator is irreversible.

14. Cap as claimed in any of the foregoing claims, characterized in that the indicating means are arranged in a liner for placing in the cap.