Abstract:
A method of manufacture of a bottle which may be closed by a push-on closure, apparatus for manufacturing the same, a bottle and a closure for the bottle. A bottle is manufactured in a multi-component assembly. The bottle preform (not shown) is made by an injection molding technique, having detents on its upwardly and outwardly facing surfaces. It is then transferred to a blow mould where it is first heated, and then shaped by inserting a blow pin through the neck of the preform to stretch it in its longitudinal axis. During this operation, the top surface of the preform is bent down, such that the detent formed on the upwardly facing surface of the preform now extends laterally into the volume of the preform. The stretched preform is then blown to take the shape of the blow mould, forming the bottle. A closure is formed by injection moulding, and is held on the bottle by the laterally extending detents.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a method of manufacturing a bottle which can be closed by a push-on closure, to apparatus for manufacturing the bottle, to a bottle and to a closure for the bottle. The invention is particularly though not exclusively suitable for use with bottles made of PET or PEN thermoplastic materials.  
         [0002]     Beer drinkers throughout the world are familiar with the so-called crown cap, which is a metal cap used with glass beer bottles to provide an effective seal and which is applied by a crimping action and removed by a simple tool which engages under the edge of the rim of the cap to bend the cap up and lever it off the bottle. Metal crown caps are very effective but require a glass bottle and can not be used with plastics bottles, particularly made of PET or PEN. There is a need for a simple push-fit closure arrangement as an alternative to the crown cap.  
         [0003]     PET bottles with screw tops are known but these do not have the same desirable properties for use with fermented or carbonated gaseous drinks as do crown caps. An example of the manufacture of a PET bottle with a screw top is described in International Patent Application WO97/19806. In that manufacture an embryo container is formed by injection moulding. The embryo container comprises a closed-end tube which will form the body of the bottle with an outward radial flange at its mouth. Part of the upper surface of the flange is formed with a spiral, which will form a screw thread. The embryo container is transferred to a stretch/blow moulding machine where pressure is applied to its interior, forcing the radial flange downwardly and outwardly so that the upper surface of the flange becomes the inner cylindrical surface of the mouth of the bottle with the screw thread formed in it.  
         [0004]     Other methods for forming PET bottles are described for instance in U.S. Pat. No. 5,126,177 (Stenger) and U.S. Pat. No. 5,501,590 (Orimoto et al.).  
         [0005]     None of the prior art however provides a means for making a bottle with a push-on closure which can be employed with a plastics bottle and/or closure without the need to use a crimped metal crown cap and yet which retains the advantages of the crown cap.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention is defined in the independent claims below to which reference should now be made. Advantageous features are set forth in the appendant claims.  
         [0007]     A preferred embodiment of the invention is described in detail below with reference to the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which:  
         [0009]      FIG. 1  is a sectional view showing the injection moulding of a preform used in manufacturing a plastics bottle in an embodiment of the invention;  
         [0010]      FIG. 2  is a sectional view of the preform obtained from the injection moulding operation;  
         [0011]      FIG. 3  is a sectional view showing the shape of the rim of the preform in more detail;  
         [0012]      FIG. 4  shows the preform when transferred to a pressure or blow moulding machine;  
         [0013]      FIG. 5  shows the preform as in  FIG. 4  with the blow core now in place;  
         [0014]      FIG. 6  shows the preform with the stretching rod partially descended and with the blow core bearing against the inside of the rim of the preform;  
         [0015]      FIG. 7  is a detail sectioned view of the rim of the bottle and the part of the blow core which bears against it before pressure is applied to the rim;  
         [0016]      FIG. 8  is a view similar to  FIG. 7  showing the rim partially distorted by the blow core;  
         [0017]      FIG. 9  is a view similar to  FIG. 7  showing the rim with its final condition with the blow core fully descended;  
         [0018]      FIG. 10  shows the stretch rod fully descended;  
         [0019]      FIG. 11  shows the bottle in the blow moulding apparatus when the bottle has been blown under pressure;  
         [0020]      FIG. 12  is a sectional view of the resultant bottle when removed from the mould;  
         [0021]      FIG. 13  is a detail showing the shape of the rim of the finished bottle more clearly;  
         [0022]      FIG. 14  is a top view of the bottle cap;  
         [0023]      FIG. 15  is a side sectional view of the cap;  
         [0024]      FIG. 16  is a sectional detail of part of the cap;  
         [0025]      FIG. 17  is a detail view of part of the cap taken on the arrow A in  FIG. 14 ;  
         [0026]      FIG. 18  is a detail sectional view showing the cap on the bottle; and  
         [0027]      FIG. 19  is a side view of the finished bottle with the cap on it.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]     The method of making a preferred embodiment of the invention and a preferred apparatus for making it, together with the resultant bottle and a closure for the bottle will now be described in detail by way of example.  
         [0029]     The bottle is made by an essentially two-stage process. Stage one involves injection moulding in an injection moulding machine a preform. This preform is then transferred to a pressure moulding machine where it is pressure moulded at an elevated temperature to form the final shape of the bottle. When placed into the pressure moulding apparatus the preform is deformed to form the rim of the bottle, and the body of the bottle is formed by blowing. Finally, the bottle is associated with a corresponding push-on closure which, after filling of the bottle, can be push-fitted to the rim of the bottle.  
         [0030]     The bottle is made of a material which is susceptible to deformation when heated. This could be glass. However, the invention is particularly suitable for making bottles out of certain plastics materials, particularly thermoplastics. Materials such as polyethylene terephthalate (PET), polyethylene naphathalate (PEN), and co-polymers and blends of these two materials, in both crystalline and a amorphous form, could be viable.  
         [0031]     The first stage in the manufacture is illustrated in  FIG. 1 . This figure shows a section through an injection moulding machine in which the preform has just been formed by injection moulding. The preform is shown at  20 . The mould consists of a cavity insert  12 , a cavity insert carrying block  14  surrounding and supporting the cavity insert  12 , neck splits  16  supported by a neck split carrying plate  18  and an injection core  22 . The preform  20  is formed in the cavity between the cavity insert  12  and the injection core  22 , with the outer edge of the rim being defined by the neck splits.  
         [0032]     The shape of the cavity is such that the preform is generally in the shape of a closed-end tube which tapers slightly towards its closed end, and has a rim at the open end of the tube and defining the opening or mouth of the bottle. The tubular part of the preform will eventually be expanded to form the body of the bottle. At this stage the outer surface and the inner surface of the preform both taper slightly towards the closed end of the tube, being defined by the inner mould surface of the cavity insert  12  and the outer mould surface of the injection core  22 , respectively. The plastics is injected through an appropriate orifice  24  in the cavity insert  12 , at the bottom end of the tube.  
         [0033]     The rim section of the preform which is to form the mouth of the bottle and surrounds the opening to the tubular section of the preform is described in more detail below.  
         [0034]     The injection moulding apparatus is provided with appropriate cooling channels around the cavity insert  12 , and a cooling tube  26  extends into the interior of the injection core  22  so as to cool the mould core portion within the tubular part of the preform  20 . In other respects the injection moulding machine is conventional.  
         [0035]     When sufficiently solid the preform is then removed from the injection moulding apparatus. This is achieved by retracting the injection core  22 , and slightly retracting the neck splits  16  on the neck split carrying plate  18 . The preform can then be removed from the mould, if necessary with the application of some pressure from the bottom through the injection orifice  24 .  
         [0036]     The resultant preform is shown in  FIGS. 2 and 3 .  FIG. 2  shows the overall shape of the preform  20 . The closed-end tube  28  forms the greater part of the length of the preform, and terminates at the rim portion  30 . The rim portion is more clearly shown in  FIG. 3 , which is a detail sectional view through one part of the periphery of the rim  30 . Here will be seen the upper part of the wall section of the tube  28  which is to form the eventual wall of the body of the bottle. On the top of the wall section  28  there is a transverse or annular flange  32  extending outwardly from the top end of the tube  28 . It should be noted that in this description the preform and the eventual bottle are assumed to be in conventional orientation, that is with the mouth at the top and the base at the bottom. The terms “up” and “down” should therefore be construed in this sense although in fact the actual orientation of the preform or the bottle may be different from this.  
         [0037]     The annular or outwardly-extending flange  32  has an upper surface  34  and a lower surface  36 . The upper surface  34  is in part over the tubular wall portion  28 , which thus depends from the inner edge of the flange. The upper surface  34  carries an upstanding first detent  40  at or towards its radially inner edge. The detent  40  on its inner periphery is generally perpendicular to the upper surface  34 , and on its outer face slopes down towards the upper surface  34 , as shown in  FIG. 3 .  
         [0038]     The outer end of the flange  32  terminates in three generally circumferential elements. The first of these is an outwardly-extending second detent  42 . Above the outer end of the flange  32  is an upwardly-extending curved-ended sealing portion  44 . This sealing portion  44  will co-operate with a push-on closure for the bottle to provide a liquid-proof seal adequate to contain the contents of the bottle when filled with beer or other carbonated beverage or similar contents. Finally, the periphery of flange  32  carries a downwardly-extending generally-cylindrical flange  46  which is essentially parallel to the upper-most portion of the wall of the tube  28 , as shown in  FIG. 3 .  
         [0039]     The preform is now transferred to a pressure moulding or blow moulding machine  50 , a section through which is shown in  FIG. 4 . The mould parts of the machine  50  define the final shape of the bottle. The exterior part of the body of the bottle is defined by three mould parts, namely two generally semi-cylindrical side mould parts  52  separable at an axial plane, and a base punt  54  forming the base of the bottle. The blow mould also includes neck splits  56  carried by a neck split carrying plate  58 .  
         [0040]     When the preform  20  is first inserted in the moulding machine  50 , it is carried by the exterior portion of the rim  30 , and in particular the second detent  42  on the exterior of the rim, engaging with correspondingly-shaped portions on the lower internal surface of the neck splits  56 .  
         [0041]     The operation of the moulding machine  50  in shaping the bottle will now be described with reference to FIGS.  5  to  11 .  
         [0042]     The operation that takes place in the moulding apparatus  50  is to move the outwardly-extending flange  32 , and the first detent  40  with it, downwardly and outwardly, relative to the second detent  42 . In effect, the first detent moves pivotally around the second detent, due to bending of the flange portion particularly at its outer region. The result of this movement is that the upper surface  34  of the flange  32  now faces inwardly rather than upwardly, and forms the inward part of the mouth of the bottle. The first detent  40  now projects inwardly into the bottle opening. In this position, as described below, a closure can be push-fitted onto the rim portion  30  of the bottle, to engage both the first now inwardly facing detent  40  and the second outwardly facing detent  42 , so that it is retained on the bottle by these two detents. When the flange and the first detent have been moved to their final positions, the tube portion  28  of the bottle is then expanded to fill the inside of the mould and form the body of the bottle. Although thus described as two distinct steps, the precise timing of the step of forming the final shape for the rim of the bottle and the expanding of the tube can be such that they overlap or are in part simultaneous, rather than purely sequential as is described.  
         [0043]     In more detail therefore,  FIG. 5  shows the preform  20  in the moulding machine  50 , with the blow core  60  of the moulding apparatus now inserted in the mouth of the mould cavity. The blow core is shaped to seal against the top of the mould when fully inserted and has a central throughway through which passes a stretch rod or pin  62  which can be extended to reach the bottom of the mould cavity, as described below. The longitudinal passage  64  through which the blow pin  62  passes is wide enough also to provide for the flow of air under pressure through the blow core past the blow pin and into the interior of the tubular portion  28  of the preform  20 . An air inlet guide bush  66  is provided within the blow core  60 . The blow core extends into the tubular section  28  below the periphery of the rim portion  30  of the preform  20 .  
         [0044]      FIG. 5  actually shows the blow core  60  before it is fully inserted. This figure shows the blow core  60  at the position where a downwardly-extending lip  68  engages with the upper surface of the transverse flange  32 , in the region of the first detent  40 . At this point the preform is at a sufficiently elevated temperature for the plastics material to be deformable. The blow core is now fully inserted into the mould to the position shown in  FIG. 6 . It is in this operation that the blow core acts as a mandrel and the flange  32  and the first detent  40  are moved downwardly and outwardly, relative to the second detent  42 , forcing the upper surface  34  of the flange now to face inwardly. The stages of operation are more clearly seen in FIGS.  7  to  9  which show the rim of the preform and the bottom of the blow core  60  on a greater scale.  
         [0045]      FIG. 7  corresponds to the position shown in  FIG. 5 , just before the blow core is fully inserted. Here the lip  68  is just starting to make contact with the outer sloping surface of the detent  40  sufficient to start the bending operation.  FIG. 8  shows an intermediate position between the  FIG. 5  and  FIG. 6  positions where the transverse flange  32  and the detent  40  have been partially moved to their final positions. The pushing effect of the lip  68  on the blow core  60  engaging with the detent  40  has started to bend and turn down the flange so as to move the radially inner portion of the flange carrying the detent  40  relative to the outer portion of the flange carrying the detent  42 . The detent  42  is being retained in position by its engagement with the neck splits  56 .  
         [0046]     The blow core is shown fully inserted in  FIG. 9 . So far as the rim is concerned, the lip  68  has now pushed the detent  40  right around through 90° so that it no longer faces upwardly, but now faces inwardly into the mouth of the bottle. In this position, the lower surface  36  of the flange  32  has now been forced round to the point where it contacts the downwardly-extending cylindrical flange  46  at the outward end of what was previously the flange  32 . Due to the fact that the plastic is at an elevated temperature, the underside of the flange  32  melts into and becomes homogeneous with the cylindrical flange  36 , thereby providing strength and solidity to the structure.  
         [0047]     It will be seen from FIGS.  7  to  9  that the periphery of the bottom end portion of the blow core  60  is relieved as at  61  to allow for the shape of the rim portion when the blow core is fully inserted. In this condition the rim  30  is now clamped between the neck splits  56  and the blow core  60 , with the second detent  42  still engaging the neck splits  56 .  
         [0048]     The next stage is for the blow pin to be extended and this is illustrated in  FIG. 10 . The blow pin  62  is now fully inserted into the mould cavity, causing the tubular section  28  to be stretched longitudinally down to the bottom end of the mould. This stretching operation is important in providing strength to the finished bottle when made of PET or PEN.  
         [0049]     Finally, air under pressure is injected through the passageway  64  in the blow core  60  and around the blow pin  62  into the interior of the bottle. The effect of this is to expand the tubular section  28  into the shape of the bottle as defined by the interior surfaces of the mould parts  52 , forming the desired final shape of the bottle. The mould parts may carry desired shaping to provide a more complex shaping for the bottle in well known manner. The expansion of the tubular part will of course thinning of the bottle wall, as is seen in  FIG. 11 . Adjacent to the rim portion  30 , the wall now flares away from the rim, this in fact being the position shown in  FIG. 9 . The path of the air into the bottle expanding the bottle is shown by arrows  70  on  FIG. 11 . The final bottle shape is now referenced  72  on  FIG. 11 . The body of the bottle has now been expanded so that the rim portion  30  is narrower than the body of the bottle.  
         [0050]     The bottle  72  is now removed from the mould and is shown in  FIG. 12 . The base of the bottle as shown in  FIG. 12  represents a modification of the bottle previously described. In this modification the base has been formed using the process described in International Patent Application publication number WO97/19802, to which reference should be made for further description thereof. Briefly, the base is provided with an undercut re-entrant shape which provides greater strength to the base portion of the bottle. This shape is formed by the use of a multipart mould having a plurality of segments surrounding a tapered core which is moveable to wedge the segments from a closely packed array to a mutually spread array. In this manner an undercut shape as shown at  74  can be provided.  
         [0051]      FIG. 13  represents a detailed sectional view through the rim portion  30 . As is seen, the first detent  40  now constitutes an inner detent, and the second detent  42 , as before, constitutes an outer detent. A plastics push-on cap can now be provided which engages with these two detents to secure the cap on the rim of the bottle. The outer wall forming the body of the bottle now lies below the outer cylindrical flange  46 , while the upper part of the rim portion  44  forms a seal with the closure as described below.  
         [0052]     It will be seen from the foregoing that the forming of the shape of the final bottle in the blow moulding machine is achieved by a combination of three measures, namely pushing the flange  32  and the top of the wall  28  with the bottom surface of the blow core  60 , pulling the wall  28  downwardly by extension of the blow pin  62 , and the application of air pressure through the passage  64  in the blow core. The manner in which these three measures are best applied can be determined empirically for any particular situation. It may be desirable to provide the pushing with the blow core first followed by stretching with the blow pin and then the application of pressure. However, it may be preferable for these steps to partially overlap or to take place simultaneously depending on the particular application.  
         [0053]     The closure for the bottle will now be described with reference to FIGS.  14  to  18  of the drawings. The closure, cap or top  100  illustrated has a planar disc-shaped central portion  102  and a peripheral bottle-engaging portion  104 . Across the top of the disc and the bottling engaging portion  104  are eight diametrically-extending ribs  106  equally spaced around the disc as seen from above in  FIG. 14 .  
         [0054]     As shown in  FIG. 15  and more clearly in  FIG. 16 , the peripheral bottle engaging portion  104  is generally in the shape of a trough or inverted U, with opposed inwardly-directed engaging tangs at the mouth of the U. More particularly, the inner arm of the U is formed by a cylindrical flange  108  depending from the outer edge of the disc  102  where it merges into the U shaped portion or arm  104 . The curved portion  110  of the U then merges into an outer cylindrical portion of arm  112  forming the outer circumferential part of the bottle-engaging portion  104 . The lower end of the flange  108  carries an outwardly-directed first tang or finger  114 , and the lower end of the outer arm  112  carries a second inwardly-directed tang or finger  116 . Whereas the detents  40  and  42  on the bottle are preferably continuous around the periphery of the bottle, the tangs  114  and  116  may be and preferably are discontinuous and each consist of a plurality of discreet tangs arranged around the circumferential extent of the closure. The tangs are of slightly lesser extent than the spaces between them. This facilitates the construction of the mould for moulding the closure which can then release the closure by a turn-then-push movement in the manner of a bayonet catch.  
         [0055]     The bottom faces of the first and second tangs  114  and  116  are champhered to allow them to separate as they pass over the rim portion  30  of the bottle.  
         [0056]     It should be noted that the ribs  106  extend over the U shaped peripheral bottle engaging portion  104  down to a circumferential ridge  118  which runs around the bottom of the outer arm  112 . That is to say the remote ends of the rib  106  provides stiffening for the outer arm  112  of the U section  104 . The extent to which this is required will need to be determined empirically.  FIG. 17  shows an end view of one of the ribs  106  as taken on the arrow A in  FIG. 14 .  
         [0057]     When the bottle has been filled with its desired contents, the cap  100  can be forced on the rim of the bottle to the position shown in  FIG. 18  in sectional view. When the closure is pressed onto the rim portion  30  of the bottle, the arms  108  and  112  distort to allow the closure to move onto the rim of the bottle. More particularly, the two arms of the U open up into a somewhat V shape so as to pass over the portions forming the rim of the bottle. First of all, the second tangs  116  engage with the side of the sealing portion  44  forming the top of the rim of the bottle so as to pass over the sealing portion  44 . The champhering of the bottom of the tangs  116  assist in this. Then the tangs  116  engage with the detent  42  while simultaneously the tangs  114  engage with the detent  40 . All four elements are angled at their points of contact, so that further pressure from above causes the inner flange  108  to move inwardly and the outer wall  112  to move outwardly, allowing the tang  114  to pass over the detent  40  and the tang  116  to pass over the detent  42  due to radial flexing. When sufficiently on the bottle, the tang  114  and the flange  108  move outwardly again to lock on the underside of the detent  40 , while correspondingly the tang  116  and the outer wall  112  move inwardly to lock and securely engage on the underside of the detent  42 . The flange  108  now extends into the interior of the bottle. In this position, the sealing portion  44  co-operates closely with the interior of the curved portion  110  of the U shaped bottle-engaging portion  104  so as to provide an effective seal against escape of liquid or the carbonating gasses within the bottle. The cap can be made of the same type of plastics material as can be used for the bottle, including in particular PET.  
         [0058]     Finally,  FIG. 19  shows a side view of the completed bottle with the closure attached. The closure  100  is securely held on the bottle  72 . However the closure  100  can be removed by application of upward pressure on the ridge  118  forming the outer lower periphery of the closure. A tool similar to that conventionally used to remove a metallic crown top from a beer bottle may be used to remove the closure  100  from the PET bottle  72 . The closure  100  will not however bend in the manner of a metallic crown top but rather will come off essentially undistorted due to inward flexure of the flange  108  and corresponding outward flexure of the outer arm  112  of the U shaped element  104 , forcing the tang  114  past the detent  40  and likewise forcing the tang  116  past the detent  42 .  
         [0059]     Finally, the retaining force holding the closure on the bottle is such that in the event of excess pressure arising in the bottle, for example exceeding 90 psi, the closure will be released from the bottle automatically by the pressure acting on the disc  102 .  
         [0060]     The bottle shape obtained is elongate with a longitudinal axis and is generally circularly symmetrical. However, other or irregular shapes can be obtained by appropriately shaping the interior of the mould.  
         [0061]     A preferred embodiment of the invention has been described by way of example. However, many modifications may be made to the method, apparatus, bottle and bottle top described, and the foregoing description should be regarded only as one example of the implementation of the invention.