Abstract:
A snap-on or screw type, tamper evident closure having first and second relatively moveable plastic parts ( 16, 18 ) which move from an initial position to a new limiting position when the closure is first opened, the new limiting position being visually distinguishable from the initial position to provide the tamper evidence. The two plastics parts are formed in mutually intimate association but have inter-engaging complimentary formations ( 22, 28, 40, 42 ) which become irreversibly disengaged on first opening of the closure.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to tamper evident closures for containers and in particular to tamper evident closures which undergo a permanent, visible change on first opening of the container. 
     Many forms of tamper evident closures for containers are known, made in plastics, metals or a combination of the two. Such closures have a part the condition and/or position of which indicates that the closure has been removed from the container, or at least an attempt to remove it from the container has been made. 
     Many of these closures have two parts which are formed separately and then assembled together after manufacture. However, closures of this kind tend to be relatively expensive, in particular because of the assembly operation. Also there is the possibility of tampering by separating the parts of the closure to overcome the tamper evidence. 
     It is also well known to provide a tamper evident closure with a portion which is partially or wholly severed from the remainder of the closure to provide the tamper evidence. Closures of this kind include those in which the free edge of the closure skirt is formed as a security ring which is attached to the remainder of the skirt by frangible bridges. The security ring breaks partially or wholly away from the closure at these bridges when the closure is first opened. A further kind of closure has relatively movable inner and outer shells, the outer shell of which has a portion formed in its crown or closure panel which is arranged to be partially or wholly severed when the shells are moved axially in relation to one another. A closure of this latter kind is disclosed in U.S. Pat. No. 4,527,701. 
     U.S. Pat. No. 5,738,231 discloses a threaded tamper indicating closure which provides an indication of initial opening by how far the closure threads onto a container neck. 
     However, the tamper evident closures discussed in the previous paragraphs have several disadvantages. For example, they may be environmentally unsatisfactory and are often unsightly and/or uncomfortable to use after they have been opened for the first time. They may also require modification of the container to which they are to be fitted. Furthermore, it may be possible for a tamperer to overcome the tamper evidence by opening the closure, breaking the frangible portion, and then reinstating the closure on the container in a substantially undetectable manner. 
     A plastics moulding technique which has been used to a limited extent in the manufacture of packaging components is commonly referred to as “sequential moulding”. In this process a plastics pre-article or “preform” is first moulded by introducing hot, possibly molten, polymer into a correspondingly shaped (and appropriately dimensioned) cavity defined by a mould, causing the polymer to conform to the mould cavity and thereafter allowing the polymer to cool and solidify. The mould cavity is then opened, leaving the preform still held on a part of the mould, and that mould part and the attached preform is used to create a new mould cavity in which the preform forms a part of the defining wall. A second hot polymer, which may differ from the first, is then introduced into and conformed to the new mould cavity, so that after cooling an article having two intimately associated parts is formed. The article is subsequently ejected, possibly after one or more additional sequential moulding operations have been performed upon it. Usually, the moulding operations are each performed by injection-moulding, with molten polymer introduced into the mould cavity at high pressure, or by compression moulding, with the second part being moulded into the shell of the preform. 
     SUMMARY OF THE INVENTION 
     The present invention is based on the realisation by the Applicants that, especially by the use of sequential moulding, a tamper evident closure can be produced from which some or all of the disadvantages of the known closures recited above are eliminated, to at least a significant degree. 
     Accordingly, the invention provides a tamper-evident closure for a container, comprising first and second plastics parts adapted to move relative to one another from an initial position to a new limiting position which is visually distinguishable from the initial position, characterised in that at least a portion of the first and second plastics parts have complimentary formations including a re-entrant section, and in the initial position the plastics parts are moulded in mutually intimate association by sequential moulding and, on first opening of the closure, the complimentary formations are adapted to disengage and thereafter cannot be re-engaged. An advantage of sequentially moulding the first and second plastic parts is that they may be provided with complimentary formations which are intimately inter-engaged in the as-moulded position, but which become disengaged, and are difficult or impossible to re-engage, once the two parts are separated for the first time. The difficulty in re-engaging the complimentary formations is enhanced by selecting a suitable shape for the complimentary formations. The invention has application to tamper evident screw and snap-on closures of the kind which are removed when it is desired to dispense product from the container. Such a closure may comprise the first and second plastic parts as relatively inner and outer closure parts respectively. 
     The closure may further include an outermost, metal part within which the inner and outer closure parts are disposed. Preferably, in the manufacture of such a closure the outer closure part is formed directly within the metal part by insert moulding, the inner closure part being subsequently formed by sequential moulding within the outer closure part. Alternatively, the inner and outer parts may be formed as a discrete component which is subsequently bonded and/or mechanically secured in the metal part. 
     “Insert moulding”, as referred to in the previous paragraph, is a form of moulding in which an article is placed into a mould as an insert, to define part of the wall of the mould cavity, hot polymer is introduced into and conformed to the mould cavity and then caused to cool and solidify. In the composite article so produced the moulded polymer is in intimate association with the insert, and may be strongly bonded to it at the interface between them. 
     The invention may also be applied to dispensing closures, that is to say closures which are held captive on the container and arranged to dispense product through a dispensing orifice which is opened and closed by relative movement between the two parts of the closure. Usually such closures have a first, body part which is attached to the container by screw or snap-on engagement. The second part is provided as a lid, which co-operates with a dispensing orifice in the body part and is usually hinged to the body part of the closure. In known closures of this type, the lid and body parts may be moulded as a single piece, with the lid and body parts connected together by a film hinge. 
     An advantage of using sequential moulding to form such hinged dispensing closures is that the film hinge may be replaced by a mechanical hinge, without the addition of the assembly operation usually inherent with use of this type of hinge. Mechanical hinges have the advantage that they are generally more robust than film hinges and thus are less likely to break. For example, the pin of the hinge may be moulded integrally with the first, body part of the closure. The lid may then be sequentially moulded with the sleeve portion of the hinge moulded integrally with the lid. 
     Use of sequential moulding to form a dispensing closure also has the advantage that different materials may be used for the body of the closure and the lid. This allows the lid to be made from a softer, more flexible material, which in turn helps the sealing performance of the closure where the lid co-operates with the dispensing orifice. Such softer materials are unsuitable for making a film hinge as they break too easily. 
     Alternatively, the outer part of the closure may be made from a harder material to provide abuse and scuff resistance and the inner part of the closure may be made from a softer material to provide a good seal both against the body and the lid. 
     This technique is particularly useful for forming a closure on a tube, such as a toothpaste tube for example. The ability to use two different materials means that the body of the closure may be made from polyethylene so that it can bond to the tube, whilst the lid may be provided in polypropylene to provide a robust mechanical hinge. 
    
    
     Several tamper evident closures embodying the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a cross section view of a first removeable closure in the as-moulded condition. 
     FIG. 2 shows a cross section view of the first closure after it has been unscrewed from the container neck. 
     FIG. 3 is a view corresponding to FIG. 1 of a second removeable closure according to the invention. 
     FIG. 4 is a view corresponding to FIG. 2 of the second closure. 
     FIGS. 5A and 5B are enlarged scrap views of the portion A ringed in FIG.  1  and show a modification of the closure of FIGS. 1 and 2, respectively before and after differential shrinkage has occurred between the closure parts. 
     FIG. 6 shows a cross section view of a hinged dispensing closure in the as-moulded condition. 
     FIG. 7 shows an exploded cross section view of the closure according to fig.6 with the lid and body portions separated to more clearly show the features of each. 
     FIG. 8 shows a plan view of the body portion of the closure shown in FIGS. 6 and 7 (with the lid removed to show the pin portion of the hinge). 
     FIGS. 9A to C show isometric views of the hinged closure of FIGS. 6 to  8 , in the as-moulded condition, opened condition and re-closed condition respectively. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring firstly to FIGS. 1 and 2, a screw closure for closing the neck of a glass or plastics container (not shown) has a generally plane closure panel or crown  10 , and a depending peripheral skirt  12  which extends to the free edge  14  of the closure. The closure is made of plastics material, and has inner and outer parts  16 ,  18  which are coextensive so as each to provide respective parts of the closure panel and the skirt. 
     A single-start, helical screw thread  19  is formed on the inner surface of the skirt of the inner closure part  16  for engagement with a complementary formation on the container neck to attach the closure releasably to the container in well known manner. When in its fully engaged position the closure forms an hermetic seal with the container neck by means of a sealing medium  20  which is positioned against the underside of the closure panel of the inner closure part. The sealing medium may be formed in situ by a moulding operation, for example by sequential moulding or as a flowed-in compound, or it may be in the form of a preformed wad which is located in position after the closure has been moulded. As a further possible alternative the sealing medium may be a flexible, downwardly extending sealing ring which is integrally moulded on the underside of the closure panel of the inner closure part. 
     The inner and outer closure parts  16 ,  18  may be formed from differing thermoplastic polymeric materials by sequential moulding. The outer part is first injection-moulded in a conventional manner, by injecting a first polymer at high pressure into a mould cavity. After the moulding has cooled and solidified the mould core, that is to say, the part of the mould which defines the interior surface of the cavity, it is substituted by a further mould core. With the interior surface of the outer part this further mould core defines a new mould cavity of corresponding shape and appropriate dimensions to the inner closure part. A second molten polymer which may differ from the first is then injected into this new mould cavity and allowed to cool and solidify to form the inner closure part, after which the composite article is ejected from the mould. For the purposes of the following description the generally cylindrical part of the interface  21  of the two parts  16 ,  18  which lies between their skirts is denoted  21 A, the generally plane part of the interface lying-between the closure panels of the parts being denoted  21 B. 
     In FIG. 1 the regions of the closure which are denoted  5 A,  5 B are shown in section taken at the cylindrical interface  21 A to reveal internal detail of the closure. From these scrap sectional views it will be understood that the closure as moulded has two sets of formations by which the inner and outer closure parts  16 ,  18  are engaged with one another. As shown in the sectional view  5 A, in a first set of these formations an inclined, outwardly projecting, substantially rigid rib  22  is moulded on the outer surface of the inner closure part. The rib is elongate and in the form of a portion of a helix. Its top and bottom ends  24 ,  26  respectively are directed transversely of the closure, i.e. perpendicularly to the closure axis XX. It will particularly be seen that the helix angle Y° of the rib, that is to say, its angle in relation to an axially directed radial plane which intersects it, is considerably less than the helix angle of the screw thread  19 . 
     The rib  22  has a depth radially of the closure such that it penetrates through part, but not all, of the wall thickness of the outer closure part in its locality. Except at its bottom end  26  it is received in a correspondingly shaped, inwardly facing groove  28  (FIG. 2) which is formed in the outer closure part by the sequential moulding operation. Because of this method of formation the rib  22  and groove  28  are in close dimensional conformity with one another and make intimate contact at the interface between them. 
     At the bottom end of the rib  22  the groove  28  is extended in both the circumferential and radial senses within the skirt of the outer closure part as an enlargement  30 . As will be understood from the drawings, this enlargement of the groove is generally rectangular as seen looking radially of the closure, its major side being directed circumferentially. It is open to the free edge  14  of the closure over a part of its length, but over the remainder of its length it is closed by a rectangular stop  32  formed where the skirt of the outer closure has its normal wall thickness. it will particularly be noted that the stop is located in alignment with the groove  28 , so as to present its transversely extending upper surface  34  for engagement by the bottom end  26  of the rib  22 . 
     Although not shown in the drawings it should be understood that the arrangement of rib  22 , complementary groove  28 , groove enlargement  30  and stop  32  is repeated on the diametrically opposite side of the closure to the arrangement shown. Thus, two of the first sets of interengaging formations are provided. 
     A second set of formations at which the closure parts  16 ,  18  engage one another is shown in the sectioned area  5 B. A thin and flexible rib  40  of helical form is moulded on the outer closure part as a downwardly and inwardly extending projection of that closure part at the interface of the closure parts where the closure panel  10  and skirt  12  meet. The rib  40  has a helix angle Z° which is of similar magnitude to, but differs slightly from, the helix angle Y° of the rib  22 . The closure shown in FIGS. 1 and 2 is about 6 cm in diameter and about 1 cm high; its rib  40  is about 0.75 mm wide, 9 mm long and 0.6 mm deep (radial depth), and its helix angles Y° and Z° are about 70° and 72° respectively. 
     The rib  40  is received in a complimentary groove  42  (FIG. 2) formed in the skirt of the inner closure part. In the same manner as the formation of the rib  22  within its groove  28 , by virtue of the sequential moulding operation by which the closure is formed the rib  40  and groove  42  are in close dimensional conformity and make intimate contact with one another at the interface between them. 
     Although only one rib  40  and complimentary groove  42  are shown in the drawings, it is to be understood that a plurality of sets of formations  40 ,  42  are provided, at a regular spacing around the closure. In the described embodiment four such sets of formations are provided. 
     The closure as moulded is as shown in FIG. 1, and in that condition is supplied to a food packer for screw-on application to a product-filled container in the normal way. Because the inner closure part  16  is inaccessible, in order to unscrew the closure for the first time the user (whether bona fide or otherwise) must turn the outer closure part in a counterclockwise direction as for a conventional screw closure. However, the plastics materials of which the inner and outer closure parts  16 ,  18  are formed are incompatible to such an extent that the bond formed between them at the interfaces  21 A,  21 B is weak or non-existent. The torque required to turn the inner closure part on the container neck is therefore greater than the torque which is required to break any bond between the closure parts and so allow the closure parts to turn relatively in relation to one another. If required, the polymeric materials of one or both of the closure parts may be modified, for example by the addition of a release agent, so as to achieve a required quality of bond between them. 
     Thus the unscrewing motion of the user initially causes the closure parts to turn in relation to one another, the ribs  22  moving along their complementary grooves  28  and causing the outer closure part to rise by cam action on the inner closure part (and the container). This relative rotational and axial movement of the closure parts continues until the bottom ends of the ribs  22  engage the upper surfaces  34  of the stops  32  to prevent further relative movement. Continued rotation of the outer closure part in the anticlockwise direction then rotates the inner closure part in the normal way until the thread  19  is disengaged from the complementary thread on the container and the closure can therefore be removed. 
     The relative movement of the closure parts described in the previous paragraph draws the ribs  40  along their complementary grooves  42 . The length of the ribs  40  is such that they are disengaged from the grooves  42  before the ribs  22  come into engagement with the stops  32 . The condition of the closure at this time is depicted in FIG.  2 . 
     As can be understood from FIG. 2, by virtue of the different helix angles of the ribs  22  and  40 , the rib  40 , after disengagement from its groove  42 , adopts a position in which it is no longer aligned with that groove. Thus, when the closure is later screwed back onto the container by turning the outer closure part in the clockwise direction, the rib  40  fails to enter the groove  42  and instead becomes compressed and distorted against the free upper surface  100  (FIG. 2) of the inner closure part. Accordingly, even though the closure may successfully reseal the container, the outer closure part is held by the rib  40  in a partially raised position on the inner closure part and the part of the skirt of the inner closure part which is still visible provides a clear visual indication that the closure has been removed and later replaced. 
     The withdrawal of the rib  40  from the groove  42  as described above is accompanied by distortion of the rib to accommodate the difference in the helix angles Y° and Z°. The rib should accordingly have a substantial degree of flexibility, and its cross-sectional dimensions are selected for that purpose. Whilst the rib  40  is shown and described as being of pure helical form, other types of formation are possible. 
     A second closure embodying the invention is shown in FIGS. 3 and 4, which show the as-moulded and operated conditions of the closure respectively. Like the first closure, the second closure is made by sequential moulding using incompatible and preferably differently coloured thermoplastics materials. Moreover, the closure arrangement is essentially as before, and the same reference numerals with primes are used to indicate corresponding features. 
     The two closures differ in that the closure of FIGS. 1 and 2 is a screw closure whereas that of FIGS. 3 and 4 is a snap-on closure, that is, it may be fitted to, and removed from, the container by purely axial movement. For that purpose the screw thread  19  of the closure of FIGS. 1 and 2 is replaced by a preferably discontinuous bead  19 ′ which projects inwardly from the inner closure part  16 ′ adjacent its free edge  14 ′. 
     The second closure has ribs  22 ′ with complimentary grooves  28 ′, and ribs  40 ′ with complementary grooves  42 ′, which essentially perform the same function as the corresponding items of the first closure. 
     The second closure is adapted for snap-on operation by selection of the helix angles of the formations, and it will be seen that the helix angle of the ribs  22 ′, which essentially determine the relative movement available between the closure parts, is zero (O°), that is to say, the ribs  22 ′ are directed axially of the closure, with no angular component. The helix angle of the ribs  40 ′ is 2°. This angle is small, but sufficient to ensure that once the ribs  40 ′ have been withdrawn from their associated grooves  42 ′, they cannot re-enter the grooves when the closure is refitted to the container. 
     In the moulding of the closures of FIGS. 1,  2  and  3 ,  4  the enlargements  30 ,  30 ′ provide access for parts of the injection-moulding tooling by which the bottom ends  26 ,  26 ′ of the ribs  22 ,  22 ′ and the top faces  34 ,  34 ′ of the stops  32 ,  32 ′ are defined and formed. 
     FIG. 4 is used to illustrate a variation of the invention in which the closure is moulded inside a metal outer shell  200 . In the manufacture of the closure the outer closure part  18 ′ is first formed within the shell by insert-moulding, the inner part  16 ′ being subsequently formed within the outer part by sequential-moulding as before. This modification, which may also be used for the closure of FIGS. 1 and 2, can provide additional rigidity and aesthetic benefit for the closure; it can also prevent the possibility that a potential tamperer may be able to remove the closure from the container when still in its as-moulded condition, by compressing the outer closure part tightly against the inner closure part during the unscrewing operation. Instead of insert-moulding the outer closure part into the shell, the closure parts may alternatively be moulded to form a discrete component by sequential-moulding, this component being subsequently bonded and/or mechanically secured in the shell. 
     A further modification, which may also be used for both closures, is illustrated in FIGS. 5A and 5B in relation to the closure of FIGS. 1 and 2. The modification is used in closures where differential shrinkage of the closure parts, in particular greater shrinkage of the inner part  16  in relation to the outer part  18 , will create a gap  50  (FIG. 5B) between the opposed surfaces of the skirts. This gap, although small, may be sufficient to allow a looseness of movement of the closure parts in relation to one another, and a resulting unsatisfactory operation of the closure. 
     In order to remove or substantially reduce such looseness, the radius on which the interface  21 A lies is locally increased at several suitable locations which are free of the formations  22 ,  28 ,  30 ,  32  and  40 ,  42 , by a distance which is the same as, or preferably slightly less than, the gap which is expected to result from the differential shrinkage. The inner closure part  16  accordingly has a plurality of raised areas which initially are located in complementary areas of the outer closure part  18 . These areas may be of any suitable shape, one such area being the rectangular land  52  shown. 
     As shown in FIG. 5B, after the inner closure part has been moulded and the closure has subsequently cooled, the raised areas of the inner closure part (e.g. the land  52 ) will adopt a position which is aligned with, or preferably slightly proud of, the surrounding surfaces  54  of the inner closure part. When the closure is operated and the closure parts move rotationally and axially in relation to one another, the raised areas will therefore move into renewed contact with the outer closure part at its surfaces  54  so as to prevent or reduce the looseness mentioned above. 
     Whilst in the described embodiments the ribs  40  and their complementary grooves  42  are formed within the skirt  12  at its intersection with the closure panel  10 , it would alternatively be possible to locate formations which are functionally equivalent to the formations  40 ,  42  wholly within the closure panel. 
     FIGS. 6 to  9  illustrate an application of the invention to a screw threaded dispensing closure  60  having a body portion  62  and a hinged lid  64 . The hinge pin  82  is formed integrally with the body portion  62  of the closure and the surrounding sleeve  84  of the hinge is formed integrally with the lid  64 . 
     The body portion  62  has a closure panel or crown  66  and a depending skirt  68  which is formed internally with a screw thread  70  for attachment to a complimentary thread on a container (not shown). On its undersurface, the closure panel  66  carries a bore seal  72  for sealing engagement with the internal surface of the neck of the container. A boss  76 , forming part of the closure panel  66  projects upwardly above the seal  72 . A dispensing orifice  78  is formed in the centre of the upstanding boss  76 , the dispensing orifice having a raised pouring lip  80 . Preferably, as shown, the boss  76  has the form of a frustocone, extending inwardly in the direction of the pouring lip  80 . This frustoconical shape assists in separating the lid  64  from the body portion  62  when the closure is first opened. 
     The body portion  62  and lid  64  of the closure are preferably formed from differing thermoplastic polymeric materials by sequential moulding. The body portion  62  is first injection moulded in a conventional manner, by injecting a first polymer at high pressure into a mould cavity. After the moulding has cooled and solidified, the upper surface of the mould, that is to say the part of the mould defining the external surface of the body, is substituted with a new mould part which defines the external surface of the lid  64 . The moulding is retained on the mould core, defining the internal features of the body portion  62 . The part of the mould cavity used to define the underside of the hinge pin  82  is moveable independently of mould core and is lowered to provide, together with the new mould part, a mould cavity which entirely surrounds the hinge pin  82 . The hinge portion of the mould cavity defines the hinge sleeve  84  which surrounds the hinge pin  82 . A second molten polymer, which may differ from the first, is then injected into the new mould cavity and allowed to cool and solidify to form the lid  64  and hinge sleeve  84 . 
     As the lid  64  is sequentially moulded around the body portion  62 , the lid is provided with an indent  86  which co-operates intimately with the poring lip  80 . Preferably, the second polymer, used for the lid, is softer and more flexible than the polymer used for the base portion. This ensures better sealing between the lid  64 , the upstanding boss  76 , the raised lip  80  of the dispensing orifice  78  and the co-operating indent  86 . 
     As shown in FIG. 9, the hinge pin  82  preferably follows the circular contour of the body portion  62 , as opposed to being a straight section. This arrangement ensures that the second polymer used to mould the lid and hinge sleeve portion (not shown in FIG. 9) can flow evenly around the hinge pin during the second stage of the moulding process, because the geometry of the cavity has a uniform cross sectional thickness. The curved hinge pin  82  has the additional benefit of producing a snap action to the hinge. Furthermore, by modification of the contour of the external surface of the hinge sleeve  84  (see FIG.  6 ), the hinge may be provided as a click hinge with a number of stable positions, separated by regions of instability. 
     A number of complimentary formations  90  which are intimately inter-engaged in the as-moulded position are provided on the body portion  62  and lid  64  of the closure  60  (as shown in FIGS. 8 and 9A to  9 C). The formations  90  in the body portion  62  and lid  64  of the closure are shaped such that when they are disengaged, on first opening of the container, they are difficult or impossible to re-engage. 
     As shown in FIG. 9A, the closure  60  is attached to a container  95  in its as-moulded configuration. The formations  90  on the body portion  62  and the lid  64  are intimately engaged. Although the closure  60  has been described as having a screw threaded engagement with the container  95 , it will readily be appreciated that the closure may be engaged on the container neck by a suitable snap fit engagement. 
     In order to open the closure for the first time, the tab  92  on the lid  64  is lifted and the formations  90  on the body portion  62  and the lid  64  are disengaged. The tab  92  may then be used to prise the lid  64  from the body portion  62 . As shown in FIG. 9B, the formations  90  on the body portion  62  are finger like, re-entrant projections. Due to their re-entrant shape, these projections will not re-align with the complimentary slots in the lid  64  when it is re-closed onto the body. Finger like projections are preferred as they can straighten slightly to allow demoulding of the body part of the closure. The projections can also flex slightly when the lid is opened, allowing them to disengage with their complimentary slots in the lid. It will be appreciated that this arrangement would not be possible if the lid and body portions of the closure where made as two independent mouldings which are subsequently assembled. 
     Finally, as shown in FIG. 9C, when the lid  64  is re-closed, it co-operates tightly with the body portion  62 , except in the region of the tab  92  where the upwardly projecting formations  90  on the body portion, prevent the tab from closing fully. The raised tab  92  provides visible tamper evidence, indicating that the closure has been opened whilst the remainder of the lid  64  ensures that the dispensing orifice  78  can be resealed. The boss  76  ensures that the raised tab  92  does not stand proud of the top of the closure, thereby reducing the chances of the tab  92  being caught or snagged once the tamper evidence has been activated. 
     Whilst injection-moulding is described above as being the moulding method used for the closure parts, if desired one or both of the closure parts may be moulded by the compression-moulding of polymer which is introduced into the mould and distributed within the mould cavity by a plunger. 
     Advantageously, the visual distinction between the as-moulded and operated conditions of the closure (i.e. as FIGS. 1 and 2 or FIGS. 9A and 9C) is enhanced by moulding the two closure parts from plastics materials having different colours, although other methods of achieving the same objective are possible. For example, the two parts of the closure may be made from the same colour material with the finger-like projections being arranged to form a textual message. Initially, when the inter-engaged projections are intimately engaged, the text will not be apparent as the surface of the projections will appear to form part of the top surface of the closure. However, once the projections are disengaged, the text will become readily apparent due to the exposed textual message. 
     It will be appreciated that in certain arrangements, the finger-like projections do not need to extend through the complimentary formations on the tab, for example, but may be provided so that they end in blind slots within the tab. In this arrangement, once the finger-like projections are disengaged from their complimentary formations, the tab will be held in a raised position providing the necessary tamper evidence but slots will not appear in the upper surface of the tab. 
     In another alternative arrangement, instead of having a re-entrant section, the inter-engaged formations may be provided as a complicated pattern of features which rely on the material shrinkage to prevent the features from being re-engaged after initial opening. 
     Although a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the apparatus without departing from the spirit and scope of the invention, as defined the appended claims.