Patent Publication Number: US-2005127023-A1

Title: Push-off cap of plastic

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a push-off cap of plastic for fastening on a container with a container neck with a retaining bead, wherein the cap comprises a peripheral skirt on which a push-piece is integrally formed and on which a peripheral guarantee strip engages via break-off webs.  
      Here it is the case of closures which are placed onto relatively wide-necked, thread-free containers and are held on the container neck with a positive and/or non-positive fit, wherein the container neck has a suitable peripheral retaining bead. Such a closure is already known from the Swiss patent CH-207 849 A with which the cap comprises a peripheral wall with which a tab for tearing off is integrally formed and a peripheral guarantee strip is integrally formed via a break-off seam. These early closures are still formed of metal. Versions in a similar constructional shape which are manufactured of plastic have however already been known for quite some time. Thus U.S. Pat. No. 3,707,240 discloses a push-off cap of plastic which may be fastened on a container neck with a retaining bead with a positive and with a non-positive fit, and additionally, for an improved sealing and mounting, is provided with a sealing plug engaging into the container neck. This closure is furthermore provided with a peripheral guarantee strip and at the location of the connection comprises a peripheral break-off seam. The guarantee strip comprises a tear-open tab but is however designed as a closed ring, but in the region of the tab comprises a break-off location running vertically to the peripheral break-off seam in the mentioned region. A similar solution, but without the mentioned sealing plug is known from U.S. Pat. No. 3,860,137.  
      Only with the further development of the shape design did then push-off caps of plastic appear which as an integrity guarantee comprise break-off seams in the form of break-off webs in the region of the push-piece. A tear seam which is perforated at a later stage forms these break-off webs. Such closures for example are known from the Swiss patent CH-A-417 378 or from U.S. Pat. No. 3,899,097.  
      During further development, the majority of push-off caps have been replaced by snap-hinge closures. Here, as also with the rotation closures, the guarantee strips were integrally formed via break-off webs. In order to be able to manufacture these closures one requires relatively complicated tools which were developed only during the eighties of the last century. On the one hand the injection moulds with star-shaped mould slides were used and later also moulds with collapsible cores and finally injection moulding tools with inserts fashioned in the manner of chucks which engage around the cap from the outside during the injection procedure and widen elastically outwards on removal from the moulds.  
      Push-off caps of plastic of the initially mentioned type may be obtained today on the market. The guarantee strips at the same time comprise a tab and an opening or break-off location present in the region of the tab. For opening a container with such a push-off cap one requires both hands. The container is held with one hand whilst the other hand grips the tab and thereafter the guarantee strip is torn off. Once the guarantee strip has been removed, the push-off cap may be opened with one hand by way of exerting a force onto the push-piece with the thumb, and the cap is elastically deformed and is pressed away past the retaining bead on the container neck.  
      It is known that during the manufacture of a plastic closure, the chain molecules of the plastic align themselves longitudinally in the break-off webs during the injection procedure. At the same time, the destruction of the break-off webs by way of tension in the direction in which the break-off webs run requires considerably more force than a destruction by a force which occurs perpendicular to the direction in which the break-off webs run and thus occurs perpendicularly to the molecule chains. This problem has been scaled down with rotation closures. With rotation closures a force multiplication is effected via the thread, by which means the required forces may be mustered despite practically all break-off webs being destroyed simultaneously. With push-off caps the forces are applied on one side in the region of the push-piece, but despite this the required forces until now have been so large that a controlled opening has not been able to be realised.  
      It is therefore the object of the present invention to realise a push-off cap of the initially mentioned type which may be opened with hand.  
     BRIEF DESCRIPTION OF THE INVENTION  
      A push-off cap with the features of patent claim  1  achieves this object.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Thanks to the new concept of varying the break-off webs along the periphery, one may achieve different opening functions. With regard to this, the subsequent description is referred to in which the invention is described in detail with reference to the drawings. The drawings show one preferred embodiment of the subject-matter of the invention by way of which solutions which differ from this are hereinafter explained in detail. There are shown in:  
       FIG. 1 a  lateral view of the push-off closure with a view onto the push-piece and  
       FIG. 2  the same view of the push-off cap rotated by 90°.  
       FIG. 3  shows the plan view of the push-off cap.  
       FIG. 4  represents a diametrical vertical section through the cap according to  FIG. 2  along line A-A in an enlarged scale, whilst  
       FIG. 5  shows a horizontal section along the line B-B according to  FIG. 2 , with a view into the inner side of the push-off cap whilst omitting the guarantee strip.  
       FIG. 6  shows the enlarged detail D, as specified in  FIG. 5  and  
       FIG. 7  the detail C according to  FIG. 4  in an enlarged scale.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      The complete push-off cap consists essentially of two elements manufactured as one piece, specifically the actual push-off cap  1  and the guarantee strip  2  which is connected to this as one piece. The actual push-off cap  1  consists of an upper cover surface  3  and a peripheral skirt  4  which connects to this. A push-piece  5  is integrally formed on the skirt  4 . The push-piece has an actual push surface  10  which projects perpendicularly from the skirt and is held on the skirt  4  reinforced by support ribs  9 .  
      The guarantee strip is realised as a closed ring and is connected to the skirt  4  of the push-off cap  1  via break-off webs  6 . An elongate support cam  7  is integrally formed on the skirt between in each case two adjacent break-off webs  6 . A thin free gap  8  remains between the elongate support cam  7  and the guarantee strip  2 . The support cams are so long that they fill out almost the entire intermediate space between in each case two adjacent break-off webs  6 . The break-off webs  6  which according to the invention are extremely thin would be destroyed per se if on placing on, the guarantee strip  2  were not to lie on the support cams. On placing the push-off cap on the container neck, the break off webs despite this are slightly compressed together. On placing on the push-off cap, a retaining bead  11  must be pressed over a corresponding retaining bead on the container neck so that these two retaining beads mutually engage behind one another with a positive fit.  
      The actual push-off cap  1  is additionally held on the container neck with a second retaining bead  12  which is integrally formed on the inner surface of the peripheral skirt  4 . Instead of a retaining bead it would also be of course possible to realise the connection with suitable retaining cams. This second retaining bead in the example represented here does not cause this to assume a sealing function. With this, on the inner side of the cover surface  3  an annular wall is arranged concentrically to the peripheral skirt  4  and forms the sealing plug  13 .  
      In  FIG. 5 , all break-off webs  6  are characterised by the letters a-l. Thanks to the present invention a simple solution has been found to be able to change the function of the push-off cap by varying the diameter of the break-off webs. For the one-handed opening on which the object of the invention has been based, it is important for the break-off webs in the region of the push-piece  5  to be able to be destroyed with relatively little effort. Accordingly, the two break-off webs g and h at their break-off location are reduced to a diameter which is smaller than the diameter at the break-off locations of the other break-off webs. This is due to the fact that the introduction of force in the region of the push-piece runs practically in the running direction of the break-off webs. In this direction, the break-off webs due to the arrangement of the chain molecules are very resistant since here practically a pure tensile force occurs. With the webs with lie further to the side, the introduction of force, created by a certain deformation of the cap, is effected by way of a combination of a tensile and shear force. Added to this is also the fact that the lever ratios always have a more favourable effect. Accordingly, the diameter of the break-off locations c-f and i-l is selected larger than the diameter of the break-off webs g and h. With the break-off webs a and b the conditions are again unfavourable and accordingly one would advantageously design the break-off webs a and b likewise smaller in cross section than the break-off webs c-f and i-l.  
      According to experience the break-off locations may be varied in the region between 0.05 mm and 0.4 mm depending on the selection of material. These details concern in particular the selection of polypropylene or polyethylene which have both been shown to be suitable for push-off caps. Other plastics however are in no way excluded. Typically, the diameter of the break-off webs in the region of the push-piece lie in the magnitude of 0.05 mm and 0.25 mm. Most preferably however the diameter would rather tend towards the lower region, specifically in the region between 0.07 mm and 0.15 mm. With the selection of this diameter of the break-off webs in the region close to the push-piece one would therefore prefer to select the break-off webs c-f and i-l in the upper region, specifically with diameters of 0.2 mm to 0.4 mm. In contrast to this the break-off webs which are arranged diametrically opposite the push-piece are selected in a magnitude of between 0.1 mm and 0.3 mm, more preferably however between 0.15 mm and 0.25 mm. All previously mentioned dimensional details are of course dimension recommendations which must be seen in relation to the push-off cap. With push-off caps with considerably larger diameters, break-off webs with larger diameters are of course also considered.  
      If such push-off caps are attached to larger receptacles, then it may be desirable to easily be able to place the push-off cap back onto the container again. This with a design according to the invention may be realised by way of increasing the break-off webs a and b in diameter with respect to the other break-off webs. In this case the break-off webs then serve as joints. With normal one-handed operation these two webs a and b are no longer severed and the closure remains hanging on these two webs. Since furthermore the guarantee strip is designed as a closed ring, this remains on the bottle and accordingly the push-off cap with the previously mentioned design shape remains fastened on the guarantee strip and thus indirectly also on the bottle. Thus the push-off cap according to the invention may be converted into a push-off cap with a so-called flap closure with little effort.  
      As is particularly evident from the  FIGS. 6 and 7 , the break-off locations are preferably formed in a conical manner. This conical shaping leads to the fact that the actual separation location or break-off location of the break-off webs  6  may be applied exactly to where this is desired. In the present case the break-off location which is indicated at  14  is applied directly on the connection location on the guarantees strip  2 . It is ensured by way of this that the remainder of the webs remain on the skirt  4 . This is selected because such closures are often attached onto relatively small bottles which are applied directly to the mouth in order to drink from this. The lips therefore would come into contact with the guarantee strip remaining on the container neck and a certain danger of injury would not be ruled out if the remainder of the severed break-off webs  6  were to remain on the guarantee strip.  
      In the present case the invention is particularly explained by way of a round closure. Basically however one may also shape the push-off caps in an oval manner or also in other shapes. If the shapes of a push-off cap deviate from the round shape, then on opening also different force conditions and other lever effects occur and accordingly the cross sections of the break-off webs may be adapted to these conditions.  
      The precision required for this is unusual for a push-off cap which indeed belongs to the most economical variant of plastic closures. Despite this, the reason why this may still be realised lies in the fact that for the manufacture here, one has employed injection moulds with chuck-like inserts. This technology per se is also unusual for plastic closures in this price class.  
      One may only realise the extraordinarily fine connection locations and break-off webs with a high processing safety thanks to the use of chucks. This high processing safety leads to a high economicability despite the relatively expensive injection moulds.