Abstract:
The invention provides, in one aspect, a method of making a container having a body and a rim defining an opening for the container, the opening being capable of being closed by a push-on lid, the container being made of a material which is susceptible to deformation when heated. In other aspects, the invention also provides a container and an apparatus for making a container.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a method of manufacturing a container which can be closed by a push-on lid, to apparatus for manufacturing the container, to a container and to a lid for the container. The invention is particularly, though not exclusively, suitable for use with containers made of PET or PEN thermoplastic materials. 
       BACKGROUND OF THE INVENTION 
       [0002]    Containers made from material which is susceptible to deformation when heated, in particular thermoplastic materials such as PET or PEN, are well known. The use of such materials to manufacture the container allows a preform to be made and then subsequently expanded under pressure to obtain a finished article. The use of such preforms is known in the art, for example in WO97/19801 and WO97/19806. 
         [0003]    Containers for materials such as paint are required to meet drop tests, whereby the container is dropped from a height and to pass the test the lid of the container must not come off. For example, a 1 m drop test is known in the art. 
         [0004]    There is therefore a need for containers, made from material which is susceptible to deformation when heated, which have a design such that the lid is secured sufficiently to pass such drop tests. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides, in a first aspect, a method of making a container having a body and a rim defining an opening for the container, the opening being capable of being closed by a push-on lid, the container being made of a material which is susceptible to deformation when heated, the method comprising the steps of: 
         [0006]    a) providing a preform made of a material which is susceptible to deformation when heated, the preform being in the shape of a closed-end tube with a rim at its mouth, the rim comprising: an outward generally-radial flange having an upper surface and a lower surface, the flange extending from a radially inner end to a radially outer end, the tube depending from the radially inner end of the flange; a first detent simultaneously formed with the flange as an upstanding elongate projection from the upper surface of the flange, which detent is located at or near the radially inner end of the flange; and a second detent simultaneously formed with the flange as an upstanding elongate projection from the upper surface of the flange, which detent is located at or near the radially outer end of the flange; 
         [0007]    b) placing the preform in a pressure moulding apparatus at an elevated temperature with the preform being located in the apparatus at least in part by the second detent; 
         [0008]    c) expanding the tube under pressure to form the body of the container; and then 
         [0009]    d) moving the first detent downwardly and outwardly relative to the second detent so that the first detent projects inwardly into the opening for the container; 
         [0010]    wherein the movement of the first detent downwardly and outwardly relative to the second detent is controlled to only occur after step c), and such that after step d) the first detent projects inwardly into the container, with its elongate axis at an angle of from 60° to 120° to the elongate axis of the second detent, such that the first detent forms an internal rim. 
         [0011]    Such a method is advantageous as it allows a container to be produced that has an internal rim, which can engage with a lid and prevent it from coming off, e.g. when the container is dropped. 
         [0012]    The container must have a body and a rim defining an opening but other than this the exact size and shape of the container is not particularly limited. In one embodiment, the body of the container is substantially cylindrical in shape but it will be appreciated that other shapes are possible. The container may or may not have a neck between the body and the opening. In the present invention a container may be, for example, a bottle, a can (such as a can of the type that can contain paint), an aerosol container, or the like. 
         [0013]    A key feature of the invention is that the first detent which forms the internal rim in the container is only moved in a controlled manner. No movement of the first detent due to the application of pressure to expand the tube is permitted. The first detent is only moved to form the internal rim after this application of pressure to expand the tube, and it is moved in a controlled manner to ensure correct positioning of the internal rim. 
         [0014]    It has not previously been recognised that the detent should be protected from movement caused by pressure “blowing out” the tube to expand it to form the body of the container. Indeed, some previous methods (e.g. in WO97/19806) have specifically looked to move the detent by the application of the “blowing out” pressure. This would move the detent in an uncontrolled manner. 
         [0015]    The present invention provides containers that have an internal rim, where the internal rim is formed in a sufficiently controlled manner that its positioning is accurate and reproducible. This was lacking in previous techniques for making containers. The controlled reproducibility is key when obtaining a product that has an internal rim which can engage with a lid and prevent it from coming off (e.g. when the container is dropped) to a repeatable and commercially useful degree. 
         [0016]    It was not previously even recognised that the methods used for forming internal rims in containers of this type were insufficiently accurate and reproducible to be useful for providing good and secure sealing mechanisms. 
         [0017]    In relation to discussion of all aspects of this invention, it should be noted that the preform and the eventual container 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”, “horizontal” and “vertical”, and the like, should therefore be construed in this sense, unless the context clearly indicates otherwise. However the skilled reader will appreciate that in fact the actual orientation of the preform or the container may be different from this. 
         [0018]    The preform provided in step a) may suitably have been injection moulded. In one embodiment, step a) comprises the step of injection moulding the preform in an injection moulding apparatus in order to provide the preform. In an alternative embodiment, however, the preform may be created in a separate stage (whether by injection moulding or otherwise) that is not part of the claimed method and therefore the preform is simply provided in step a), having already been made. 
         [0019]    The preform provided in step a) has a first detent that is located at or near the radially inner end of the flange. In this regard, it is preferred that the first detent is located between the radially inner end of the flange and the midpoint of the radially inner end of the flange and the radially outer end of the flange. Accordingly, the linear distance between the first detent and the radially inner end of the flange is less than 50% than of the total linear distance between the radially inner end of the flange and the radially outer end of the flange. In one preferred embodiment, the linear distance between the first detent and the radially inner end of the flange is less than 40%, such as less than 30%, or less than 25%, of the total linear distance between the radially inner end of the flange and the radially outer end of the flange. It may be that the linear distance between the first detent and the radially inner end of the flange is 20% or less, such as 15% or less or 10% or less, of the total linear distance between the radially inner end of the flange and the radially outer end of the flange. 
         [0020]    In one embodiment, the first detent extends from the flange for a length of from 0.5 mm or more, preferably 1 mm or more, e.g. from 1 mm to 10 mm; more preferably 1.5 mm or more, such as from 1.5 mm to 10 mm; for example 2 mm or more, e.g. from 2 mm to 5 mm. 
         [0021]    In one embodiment, in the preform provided in step a) the first detent has its inner periphery substantially perpendicular to the upper surface of the flange. Preferably, in the preform the first detent has its outer periphery substantially perpendicular to the upper surface of the flange. 
         [0022]    The preform provided in step a) has a second detent that is located at or near the radially outer end of the flange. In this regard, it is preferred that the second detent is located between the radially outer end of the flange and the midpoint of the radially inner end of the flange and the radially outer end of the flange. Accordingly, the linear distance between the second detent and the radially outer end of the flange is less than 50% than of the total linear distance between the radially inner end of the flange and the radially outer end of the flange. In one preferred embodiment, the linear distance between the second detent and the radially outer end of the flange is less than 40%, such as less than 30%, or less than 25%, of the total linear distance between the radially inner end of the flange and the radially outer end of the flange. It may be that the linear distance between the second detent and the radially outer end of the flange is 20% or less, such as 15% or less or 10% or less, of the total linear distance between the radially inner end of the flange and the radially outer end of the flange. 
         [0023]    In one embodiment, the preform has more than two detents simultaneously formed with the flange as an upstanding elongate projection from the upper surface of the flange, for example it may have three or more such detents, e.g. three, four or five such detents. 
         [0024]    In a preferred embodiment, the preform provided in step a) has a third detent simultaneously formed with the flange as an upstanding elongate projection from the upper surface of the flange, located between the first detent and the second detent. 
         [0025]    Preferably, the third detent and second detent between them define a trough, suitable for receipt of a correspondingly shaped sealing projection on the container lid, there being a sealing portion in the trough for sealing engagement with the sealing projection of the lid. 
         [0026]    In one such embodiment, the third detent is located substantially half way between the first detent and the second detent. For example, it may be that the linear distance between the third detent and the second detent is equal to the linear distance between the third detent and the first detent, or these distances may differ by an amount that is not more than 20%, such as not more than 15%, or not more than 10%, of the total linear distance between the first detent and the second detent. 
         [0027]    In one embodiment, the second detent is provided with an outwardly facing protrusion, suitable for engaging with an engaging portion on the container lid. The second detent may, for example, have its outer face sloped so as to create a protrusion, e.g. due to the outer face sloping outwardly from top to bottom. The second detent may equally have a separate protrusion extending from the outer face. 
         [0028]    In one embodiment, the first detent extends continuously around the mouth of the preform provided in step a). This will provide a container that has a continuous internal rim that can be used to receive a “push-fit” type lid. 
         [0029]    In another embodiment, the first detent is discontinuous, for example it may be made up of two or more sections, such as three, four, five, six, seven, eight, nine, ten or more sections. This will provide a container that has a discontinuous internal rim that can be used to receive a “bayonet-fit” type lid. The sections may be spaced apart regularly or irregularly. For example, the first detent may be discontinuous and made up of four or eight regularly spaced detent sections. 
         [0030]    In one embodiment, the spaces between the detent sections are equal to or smaller than the detent sections themselves. In another embodiment, the spaces between the detent sections are larger than the detent sections themselves. Preferably, the detent sections make up 30% or more of the circumference of the first detent, such as 40% or more, e.g. 50% or more, such as 60% or more. 
         [0031]    In one embodiment, one or more of the detent sections are provided with a protrusion which can act to prevent rotation of the lid relative to the container. 
         [0032]    In one embodiment, the second detent extends continuously around the mouth of the preform. This may be advantageous in providing a complete seal for the container. 
         [0033]    In an alternative embodiment, the second detent is discontinuous around the mouth of the preform. This embodiment may be used for applications where having a sealed container is less important. 
         [0034]    The preform and resultant container are made of a material which is susceptible to deformation when heated. This could be glass. However, the invention is particularly suitable for making containers 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 amorphous form, could be viable. Reference to polyethylene terephthalate (PET) includes recycled PET. 
         [0035]    In one embodiment, the preform provided in step a) is shaped with the rim narrower than the tube, such that in the resultant container the rim is narrower than the body. Preferably, in the resultant container the width of the rim is 90% or less of the width of the body, such as 85% or less, e.g. 80% or less. This is advantageous in that it allows a handle to be incorporated into the rim area without affecting the overall width of the container. Therefore the containers can be stacked together more easily, without space being wasted between containers that are placed side to side. 
         [0036]    Step b) is suitably carried out using pressure moulding apparatus having mould parts defining a mould cavity and comprising: (i) a securing component that permits the location of the preform in the mould cavity with the second detent in a fixed location therein, (ii) a generator of a pressure differential between the interior of the tube and the exterior to expand the tube into contact with the mould parts defining the mould cavity; (iii) a shield for shielding the first detent from the pressure that is applied to expand the tube; and (iv) a source of controlled downward pressure, e.g. of 600 kPa or higher, that can act to move the flange and the first detent downwardly and outwardly relative to the second detent such that the upper surface of the flange faces inwardly and the first detent projects inwardly into the opening for the container, with its elongate axis at an angle of from 60° to 120° to the elongate axis of the second detent, such that the first detent forms an internal rim. 
         [0037]    Preferred apparatus is of the type described further below. 
         [0038]    Step c) may involve expanding the tube under pressure to form the body of the container in any conventional manner. 
         [0039]    In one embodiment, step c) may comprise applying differential pressure between the interior of the preform and the exterior of the preform, to expand the tube portion to form the body of the container. 
         [0040]    In one embodiment, step c) may involve the injection of air or other gas under pressure into the tube, to expand it into the shape of the container body as defined by the interior surfaces of the mould parts in the pressure moulding apparatus. 
         [0041]    Optionally, step c) may comprise longitudinally stretching the tube portion of the preform. It may be that this is in addition to the injection of air or other gas under pressure into the tube. The longitudinally stretching may be before, during or after the injection of gas. 
         [0042]    The expansion of plastic preforms under pressure is known (e.g. from WO97/19801 and WO97/19806) and can be carried out at any suitable temperature and pressure. 
         [0043]    As discussed above, it is key that the first detent is not moved until after step c). The first detent is moved in a controlled manner in step d). 
         [0044]    Preferably, therefore, the first detent is shielded from the pressure applied in step c). This may be due to it being located in the pressure moulding apparatus in a location that is not exposed to the pressure applied in step c). In a preferred embodiment, the first detent is located in the pressure moulding apparatus in a location that is separated from the inside of the tube which is to be exposed to the pressure to cause expansion of the tube. 
         [0045]    In one such embodiment, the first detent is located in a section within the pressure moulding apparatus, wherein this section is separated from the inside of the tube which is to be exposed to pressure, to cause expansion of the tube, by a shielding wall. The shielding wall seals the section away from the inside of the tube which is to be exposed to pressure, and therefore prevents the first detent from being exposed to this pressure. 
         [0046]    For example, in one embodiment the first detent is located in the pressure moulding apparatus in a corridor whereby a wall of the corridor contacts the preform at a point between where the tube extends from the radially inner end of the flange and the first detent, such that the wall forms a barrier between the first detent and the parts of the preform exposed to pressure in step c). 
         [0047]    Preferably, the inward projection of the detent after step d) is such that its elongate axis is at an angle of from 65° to 115° to the elongate axis of the second detent, such as from 70° to 110°, more preferably from 75° to 105°, for example from 80 to 100°, most preferably from 85 to 95°, such as from 87 to 93°, e.g. about 90°. 
         [0048]    In one embodiment, the inward projection of the detent after step d) is such that it does not extend substantially beyond perpendicular to the elongate axis of the second detent. For example, its elongate axis may be at an angle of from 65° to 95° to the elongate axis of the second detent, such as from 70° to 90°, more preferably from 80 to 90°, most preferably from 85 to 90°. 
         [0049]    Preferably, in step d) the movement of the first detent may be achieved by applying downward pressure of 600 kPa or higher, e.g. from 600 to 2000 kPa, to the first detent, whilst supporting the second detent in a fixed position, so as to cause the first detent to move downwardly and outwardly with respect to the second detent. For example, a pressure of 650 kPa or higher, preferably 700 kPa or higher, such as 750 kPa or higher, e.g. 800 kPa or higher, more preferably 900 kPa or higher, such as 1000 kPa or higher, e.g. 1100 kPa or higher, or even 1200 kPa or higher may be used. In one embodiment, the pressure used is from 650 to 2000 kPa or higher, such as from 700 to 1800 kPa or higher or from 750 to 1500 kPa or higher. It may, for example, be from 800 kPa to 1800 kPa or higher or from 900 kPa to 1500 kPa or higher. In one embodiment it is from 1000 kPa to 1800 kPa or higher, preferably from 1100 kPa to 1500 kPa or higher. 
         [0050]    In one embodiment, the pressure is applied for 0.05 s or more, such as from 0.05 s to 1 second, for example from 0.05 to 0.8 s, such as from 0.05 to 0.7 s, e.g. from 0.1 to 0.6 s, for example from 0.1 to 0.5 s, such as about 0.3 s. 
         [0051]    Step d) may apply pressure in any suitable manner; for example hydraulically, pneumatically or elastically. 
         [0052]    For example, a mechanical device that applies pressure using a mechanical spring, hydraulics or pneumatics may be considered. A nitrogen spring may also be used. Equally, pressure could be applied by direct application of a pressurised gas. 
         [0053]    In one embodiment, step d) uses a mechanical device, such as a piston, to place downward pressure on the first detent. The piston movement is controlled to ensure that after step d) the first detent projects inwardly into the container, with its elongate axis at an angle of from 60° to 120° to the elongate axis of the second detent, such that the first detent forms an internal rim. The piston may be, for example, pneumatic or hydraulic. 
         [0054]    In this regard, the piston may be physically prevented from moving beyond a set distance that corresponds to movement of the first detent to a location where it projects inwardly into the container, with its elongate axis at an angle of 120° to the elongate axis of the second detent. For example, a stop or block may be provided in the pressure moulding apparatus that prevents the piston from moving beyond a set distance. A casing, such as a steel casing, may act as a stop to prevent the piston from moving beyond a set distance. A cushion may be used to aid smooth operation. 
         [0055]    Equally, the movement of the piston may be computer controlled, with the computer controlling the movement of the piston so that it does not move beyond a set distance that corresponds to movement of the first detent to a location where it projects inwardly into the container, with its elongate axis at an angle of 120° to the elongate axis of the second detent. 
         [0056]    Pressurised gas, e.g., air or nitrogen, may alternatively or additionally be used to place downward pressure on the first detent in step d). For example, a nozzle may be located above the first detent and may be used to blow air or other gas onto the first detent to cause their downward movement. The pressure of the gas and time for which the gas is applied are controlled so as to ensure that after step d) the first detent projects inwardly into the container, with its elongate axis at an angle of from 60° to 120° to the elongate axis of the second detent, such that the first detent forms an internal rim. 
         [0057]    In one embodiment, the rim includes a downward flange depending from the lower face of the radial flange. The downward flange may extend from the flange at any location that is outward of the first detent. For example, it may be substantially half way between the first detent and the second detent, or it may be closer to the second detent than the first detent. 
         [0058]    In one such embodiment, in step d) the lower surface of the radial flange moves into homogeneous contact with the downward flange. 
         [0059]    In one embodiment, the method further comprises the step of: 
         [0060]    e) filling the container with a product. 
         [0061]    In one embodiment, after step d) or optional step e), the method further comprises the step of: 
         [0062]    f) fitting a lid to the container, in which the lid includes (i) a trough, suitable for receipt of and engagement with the second detent, and (ii) an engaging portion for receipt under and engagement with the inner rim formed by the first detent, to secure the lid on the container. 
         [0063]    The engaging portion of the lid may, in one embodiment, be discontinuous around the lid. In one such embodiment, the first detent is also discontinuous. 
         [0064]    Accordingly, the engagement of the engaging portion with the inner rim formed by the first detent may provide a push and twist, bayonet style, fastening of the lid to the container. The step f) may therefore involve pushing and twisting the lid onto the container. 
         [0065]    In an alternative embodiment, the first detent, and hence the inner rim, is continuous. In such an embodiment, the engagement of the engaging portion with the inner rim formed by the first detent may provide a push fit fastening of the lid to the container. The step f) may therefore involve push-fitting the lid onto the container. 
         [0066]    In optional step e), the product placed into the container may be any product that can be stored in a push fit or bayonet fit container. It may be a solid or liquid product, including emulsions. For example, it may be paint, varnish, or ink, medication (in liquid form or in solid form, e.g. tablets), food supplements (such as vitamin supplements), industrial chemicals, food or drink (e.g. tea bags, instant or ground coffee, milk, biscuits, cereal, pasta, rice), fuel (e.g. petrol, diesel); detergent products, e.g. for laundry or dishwashing, in powder or tablet or liquid form (such as dishwasher tablets, dishwasher salt, laundry powder or tablets); or pet food (e.g. dog biscuits). 
         [0067]    In a second aspect, the invention provides a container obtainable by the method of the first aspect. The container is, therefore, made of a material which is susceptible to deformation when heated, and the container comprises a body portion and a rim portion, the body portion having a base wall and a side wall extending upwardly therefrom, the rim portion extending from the side wall and providing an opening constituting the mouth of the container, the rim portion including an inwardly facing detent facing into the opening and a first upwardly facing detent facing upwards from the opening, located at or near the radially outer edge of the rim, wherein the inwardly facing detent projects inwardly into the container with its elongate axis at an angle of from 60° to 120° to the elongate axis of the first upwardly facing detent, such that the first detent forms an internal rim. 
         [0068]    Preferably, the inward projection of the inwardly facing detent is such that its elongate axis is at an angle of from 65° to 115° to the elongate axis of the first upwardly facing detent, such as from 70° to 110°, more preferably from 75° to 105°, for example from 80 to 100°, most preferably from 85 to 95°, such as from 87 to 93°, e.g. about 90°. 
         [0069]    In one embodiment, the inward projection of the detent is such that it does not extend substantially beyond perpendicular to the elongate axis of the first upwardly facing detent. For example, its elongate axis may be at an angle of from 65° to 95° to the elongate axis of the first upwardly facing detent, such as from 70° to 90°, more preferably from 80 to 90°, most preferably from 85 to 90°. 
         [0070]    In one embodiment, the inwardly facing detent extends inwardly for a length of from 0.5 mm or more, preferably 1 mm or more, e.g. from 1 mm to 10 mm; more preferably 1.5 mm or more, such as from 1.5 mm to 10 mm; for example 2 mm or more, e.g. from 2 mm to 5 mm. 
         [0071]    In one embodiment, the rim has more than one upwardly facing detent facing upwards from the opening, for example it may have two or more such detents, e.g. two, three or four such detents. 
         [0072]    In a preferred embodiment, the container has a second upwardly facing detent facing upwards from the opening. For example, this may be located at or near the radially inner edge of the rim. 
         [0073]    Preferably, the first and second upwardly facing detents between them define a trough, suitable for receipt of a correspondingly shaped sealing projection on the container lid, there being a sealing portion in the trough for sealing engagement with the sealing projection of the lid. 
         [0074]    In one preferred embodiment, the first upwardly facing detent is provided with an outwardly facing protrusion, suitable for engaging with an engaging portion on the container lid. The detent may, for example, have its outer face sloped so as to create a protrusion, e.g. due to the outer face sloping outwardly from top to bottom. The detent may equally have a separate protrusion extending from the outer face. 
         [0075]    In one embodiment, the rim includes a downwardly facing flange facing downwards from the opening. The downwardly facing flange may extend downwardly at or near the inner edge of the rim, or it may be closer to the outer edge than the inner edge. 
         [0076]    In one embodiment, the inwardly facing detent extends continuously around the mouth of the container. 
         [0077]    In another embodiment, the inwardly facing detent is discontinuous, for example it may be made up of two or more sections, such as three, four, five, six, seven, eight, nine, ten or more sections. The sections may be spaced apart regularly or irregularly. 
         [0078]    For example, the inwardly facing detent may be discontinuous and made up of four or eight regularly spaced detent sections. 
         [0079]    In one embodiment, the spaces between the inwardly facing detent sections are equal to or smaller than the detent sections themselves. In another embodiment, the spaces between the detent sections are larger than the detent sections themselves. Preferably, the detent sections make up 30% or more of the circumference of the inwardly facing detent, such as 40% or more, e.g. 50% or more, such as 60% or more. 
         [0080]    In one embodiment, the first upwardly facing detent extends continuously around the mouth of the preform. 
         [0081]    The container is made of a material which is susceptible to deformation when heated. This could be glass. However, the invention is particularly suitable for containers made 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 amorphous form, could be viable. 
         [0082]    Preferably the rim is narrower than the body of the container. Preferably, in the container the width of the rim is 90% or less of the width of the body, such as 85% or less, e.g. 80% or less. This is advantageous in that it allows a handle to be incorporated into the rim area without affecting the overall width of the container. Therefore the containers can be stacked together more easily, without space being wasted between containers that are placed side to side. 
         [0083]    The invention provides, in a third aspect, a lid for use with the container of the second aspect, the lid having (i) a peripheral trough suitable for receipt of and engagement with the first upwardly facing detent, (ii) an engaging portion located radially inwardly from the peripheral trough for receipt under and engagement with the inwardly facing detent, to secure the lid on the container. 
         [0084]    The engaging portion of the lid may, in one embodiment, be discontinuous around the lid. Accordingly, the engagement of the engaging portion with the inwardly facing detent may provide a push and twist, bayonet style, fastening of the lid to the container. 
         [0085]    There may, for example, be three or more sections, such as four, five, six, seven, eight, nine, ten or more sections. The sections may be spaced apart regularly or irregularly. For example, the engaging portion of the lid may be discontinuous and made up of four or eight regularly spaced sections. 
         [0086]    In one embodiment, the spaces between the sections are equal to or smaller than the sections themselves. In another embodiment, the spaces between the sections are larger than the sections themselves. Preferably, the sections make up 30% or more of the circumference of the engaging portion of the lid, such as 40% or more, e.g. 50% or more, such as 60% or more. 
         [0087]    One or more of the engaging portions may be provided with a protrusion which can act to prevent rotation of the lid relative to the container. 
         [0088]    Alternatively, the engaging portion of the lid may, in one embodiment, be continuous around the lid. Accordingly, the engagement of the engaging portion with the inwardly facing detent may provide a push fit style fastening of the lid to the container. 
         [0089]    The peripheral trough may, in one embodiment, be defined between inner and outer cylindrical flanges, wherein the inner cylindrical flange is fixed and the outer cylindrical flange is hinged so that it can move from an open position where it does not engage with the first upwardly facing detent to a closed position where it does engage with the first upwardly facing detent. In particular, this may be a “click-lock” type hinge. In such an embodiment the lid is made from a material that is sufficiently flexible to permit the formation of such a hinge, such as polypropylene or polyethylene. 
         [0090]    The outer cylindrical flange may be continuous or discontinuous. 
         [0091]    The outer cylindrical flange may, for example, have three or more sections, such as four, five, six, seven, eight, nine, ten or more sections. The sections may be spaced apart regularly or irregularly. 
         [0092]    For example, the outer cylindrical flange may be discontinuous and made up of four, six or eight regularly spaced sections. 
         [0093]    The spaces between the sections may be equal to or smaller than the sections themselves. Alternatively, the spaces between the sections are larger than the sections themselves. Preferably, the sections make up 30% or more of the circumference of the outer cylindrical flange, such as 40% or more, e.g. 50% or more, such as 60% or more. 
         [0094]    In an alternative embodiment, the peripheral trough is defined between fixed inner and outer cylindrical flanges. 
         [0095]    In this alternative embodiment the corresponding container may optionally be provided with external lugs to enhance the strength and security of the closure. These lugs are provided on the injection moulded preform from which the container is formed and are unaffected by the pressure blow moulding of the container. The lugs are located below the second detent and project outwardly from the container. For example, in a preferred embodiment the container is provided with a downward flange depending from the lower face of the radial flange and the lugs are located on the outside surface of this flange. 
         [0096]    The container may, for example, have two or more sections, such as three, four, five, six, seven, eight, nine, ten or more lugs. The lugs may be spaced apart regularly or irregularly. 
         [0097]    For example, the container may have four, six or eight regularly spaced lugs around its outer periphery. 
         [0098]    In this alternative embodiment, the fixed outer cylindrical flange may be shaped to engage with any such external lugs, so that the lugs act to further hold the lid in place on the container. 
         [0099]    The outer cylindrical flange is preferably discontinuous. The outer cylindrical flange may, for example, have three or more sections, such as four, five, six, seven, eight, nine, ten or more sections. The sections may be spaced apart regularly or irregularly. 
         [0100]    For example, the outer cylindrical flange may be discontinuous and made up of four, six or eight regularly spaced sections. 
         [0101]    The spaces between the sections may be equal to or smaller than the sections themselves. Alternatively, the spaces between the sections are larger than the sections themselves. Preferably, the sections make up 30% or more of the circumference of the outer cylindrical flange, such as 40% or more, e.g. 50% or more, such as 60% or more. 
         [0102]    In such an embodiment, the lid may be made of plastics materials, such as thermoplastics, including polyethylene, polypropylene, polyethylene terephthalate (PET), polyethylene naphathalate (PEN), and co-polymers and blends thereof, in both crystalline and amorphous form. Reference to polyethylene terephthalate (PET) includes recycled PET. It may also be made of metal, including alloys, wood, or glass. 
         [0103]    In a fourth aspect of the invention, there is provided a closed container, comprising a container in accordance with the second aspect and a lid in accordance with the third aspect, wherein the lid seals the container. 
         [0104]    In one embodiment, the closed container may contain product. The product may be any product that can be stored in a push fit or bayonet fit container. It may be a solid or liquid product, including emulsions. For example, it may be paint, varnish, or ink, medication (in liquid form or in solid form, e.g. tablets), food supplements (such as vitamin supplements), industrial chemicals, or fuel (e.g. petrol, diesel). 
         [0105]    In a fifth aspect, the invention provides apparatus for making a container having a body and a rim portion defining an opening for the container, the opening being capable of being closed by a push-on lid, the apparatus comprising: 
         [0106]    pressure moulding apparatus having mould parts defining a mould cavity and comprising: (i) a securing component that permits the location of the preform in the mould cavity with the second detent in a fixed location therein, (ii) a generator of a pressure differential between the interior of the tube and the exterior to expand the tube into contact with the mould parts defining the mould cavity; (iii) a shield for shielding the first detent from the pressure that is applied to expand the tube; and (iv) a source of controlled downward pressure, e.g. of 600 kPa or higher, that can act to move the flange and the first detent downwardly and outwardly relative to the second detent such that the upper surface of the flange faces inwardly and the first detent projects inwardly into the opening for the container, with its elongate axis at an angle of from 60° to 120° to the elongate axis of the second detent, such that the first detent forms an internal rim. 
         [0107]    In one embodiment, the apparatus is suitable for making a container in accordance with the second aspect. 
         [0108]    In one embodiment, the apparatus is suitable for carrying out a method in accordance with the first aspect. 
         [0109]    Preferably, the shield is provided by the inclusion of a section within which the first detent can be located, which section can act to shield the first detent from the pressure that is applied to expand the tube. 
         [0110]    In one such embodiment, the pressure moulding apparatus includes a section within which the first detent can be located, this section being separated from the inside of the tube which is to be exposed to pressure to cause expansion of the tube by a shielding wall. The shielding wall seals the section away from the inside of the tube which is to be exposed to pressure, and therefore prevents the first detent from being exposed to this pressure. For example, the pressure moulding apparatus may include a corridor, within which the first detent can be located, whereby when the preform is in the apparatus a wall of the corridor contacts the preform at a point between where the tube extends from the radially inner end of the flange and the first detent, such that the wall forms a barrier between the first detent and the parts of the preform exposed to the pressure that is applied to expand the tube. 
         [0111]    Preferably, the source of controlled downward pressure can apply a pressure of 650 kPa or higher, preferably 700 kPa or higher, such as 750 kPa or higher, e.g. 800 kPa or higher, more preferably 900 kPa or higher, such as 1000 kPa or higher, e.g. 1100 kPa or higher, or 1200 kPa or higher. 
         [0112]    In one embodiment, the source of controlled downward pressure can apply a pressure of 600 kPa or higher (such as 700 kPa or higher, 800 kPa or higher, 900 kPa or higher, 1000 kPa or higher, 1100 kPa or higher, or 1200 kPa or higher) for from 0.05 s or more, preferably from 0.1 to 1 second, for example from 0.2 to 0.8 s, such as from 0.3 to 0.7 s, e.g. from 0.4 to 0.6 s, such as about 0.5 s. 
         [0113]    Preferably, the source of controlled downward pressure comprises a mechanical device, such as a piston, to place downward pressure on the first detent. 
         [0114]    In this regard, the apparatus suitably includes a component for physically preventing the piston from moving beyond a set distance that corresponds to movement of the first detent to a location where it projects inwardly into the container, with its elongate axis at an angle of 120° to the elongate axis of the second detent. For example, a stop or block may be provided in the pressure moulding apparatus that prevents the piston from moving beyond a set distance. Equally, a computer may be included and the movement of the piston may be computer controlled, with the computer controlling the movement of the piston so that it does not move beyond a set distance that corresponds to movement of the first detent to a location where it projects inwardly into the container, with its elongate axis at an angle of 120° to the elongate axis of the second detent. 
         [0115]    The source of controlled downward pressure can comprise a source of pressurised gas, e.g. air, to place downward pressure on the first detent. For example, the apparatus may comprise a nozzle located above the flange and first detent which can be used to blow air or other gas onto the first detent to cause their downward movement. The pressure of the gas and time for which the gas is applied are controlled so as to ensure that the first detent may be moved to project inwardly into the container, with its elongate axis at an angle of from 60° to 120° to the elongate axis of the second detent, such that the first detent forms an internal rim. 
         [0116]    The generator of a pressure differential between the interior of the tube and the exterior to expand the tube into contact with the mould parts defining the mould cavity may suitably comprise a source of pressurised gas, such as pressurised air. 
         [0117]    Suitably, this may comprise a blow core that has a central throughway through which a flow of air or other gas under pressure can be blown into the interior of the tubular portion of the preform. An air inlet guide bush may be provided within the blow core. The blow core may, in use, extend into the tubular section below the periphery of the rim portion of the preform. 
         [0118]    The apparatus may further comprise a stretching component that can be used to longitudinally stretch the tube portion of the preform. This may, for example, be a stretch rod or pin. This component may be provided as part of the generator of a pressure differential. For example, a blow core may be provided that has a blow pin passing through its longitudinal cavity, which in use can be extended to reach the bottom of the mould cavity. 
         [0119]    The securing component that permits the location of the preform in the mould cavity with the second detent in a fixed location therein may suitably comprise a shaped cavity or seat for receipt of the second detent. The shape of the shaped cavity or seat can be such that the second detent is securely received and has limited movement in a horizontal direction. 
         [0120]    The apparatus may, in one embodiment, further comprise: 
         [0121]    injection moulding apparatus shaped and arranged to produce a preform in the shape of a closed-end tube with a rim at its mouth, the rim comprising: (a) an outward generally-radial flange having an upper surface and a lower surface, the flange extending from a radially inner end to a radially outer end, the tube depending from the radially inner end of the flange; (b) a first detent simultaneously formed with the flange as an upstanding elongate projection from the upper surface of the flange, which detent is located at or near the radially inner end of the flange; and (c) a second detent simultaneously formed with the flange as an upstanding elongate projection from the upper surface of the flange, which detent is located at or near the radially outer end of the flange. 
         [0122]    A preferred, non-limiting, embodiment of the invention is described in detail below with reference to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0123]    By way of example, the invention is described with reference to the accompanying drawings, in which: 
           [0124]      FIG. 1  is a sectional view showing the injection moulding of a preform used in manufacturing a plastics container in an embodiment of the invention; 
           [0125]      FIG. 2  shows the preform when transferred to a pressure or blow moulding machine; 
           [0126]      FIG. 3  shows the preform as in  FIG. 2  with the blow core now in place; 
           [0127]      FIG. 4  shows the preform with the stretching rod partially descended and with the blow core bearing against the inside of the rim of the preform; 
           [0128]      FIG. 5  shows the container in the blow moulding apparatus when the container has been blown under pressure; 
           [0129]      FIG. 6  is a detail showing the shape of the rim of the finished container more clearly; 
           [0130]      FIG. 7  is a side view of the container; 
           [0131]      FIG. 8  is a view from below of a lid for the container; 
           [0132]      FIG. 9  is a cross sectional view showing the shape of the periphery of the lid more clearly; 
           [0133]      FIG. 10  is a side view of two of the containers stacked side by side; 
           [0134]      FIG. 11  is a side view of an alternative embodiment of the container; 
           [0135]      FIG. 12  is a cross sectional view of the lid for the alternative embodiment of the container; and 
           [0136]      FIG. 13  is a cross sectional detail showing the shape of the periphery of the lid of  FIG. 12  more clearly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0137]    The method of making a preferred embodiment of the invention and a preferred apparatus for making it, together with the resultant container and a lid for the container will now be described in detail by way of example. 
         [0138]    The container is made by an essentially two-stage process. Stage one involves injection moulding, in an injection moulding machine, a preform. This stage may be carried out separately and therefore is not an essential stage of the claimed method. The preform may therefore simply be provided and then subjected to stage two. 
         [0139]    In stage two the preform is transferred to a pressure moulding machine where it is pressure moulded at an elevated temperature to form the final shape of the container. When placed into the pressure moulding apparatus the preform is deformed to form the rim of the container, and the body of the container is formed by blowing. 
         [0140]    In a further stage (which again can be carried out separately and therefore is not an essential part of the claimed method) the container is associated with a corresponding push-on lid which can be push-fitted to the rim of the container. The container may be filled with product before push-fitting the lid onto the container. 
         [0141]    Stage one 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  1 . The mould consists of a base plate  3 , a cavity insert  4 , a cavity insert carrying block  5  surrounding and supporting the cavity insert, neck splits supported by a neck split carrying plate and an injection core. There is also an injection nozzle  2 . The preform is formed in the cavity between the cavity insert and the injection core, with the outer edge of the rim being defined by the neck splits. 
         [0142]    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 container. The tubular part of the preform will eventually be expanded to form the body of the container. 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 and the outer mould surface of the injection core, respectively. The plastics material is injected through the injection nozzle at the bottom end of the tube. 
         [0143]    The rim section of the preform which is to form the mouth of the container and surrounds the opening to the tubular section of the preform is described in more detail below. The injection moulding apparatus is provided with appropriate cooling channels around the cavity insert, and a cooling tube extends into the interior of the injection core so as to cool the mould core portion within the tubular part of the preform. In other respects the injection moulding machine is conventional. 
         [0144]    When sufficiently solid the preform is then removed from the injection moulding apparatus. This is achieved by retracting the injection core, and slightly retracting the neck splits on the neck split carrying plate. 
         [0145]    The preform can then be removed from the mould, if necessary with the application of some pressure from the bottom through the injection orifice. 
         [0146]      FIG. 2  shows the overall shape of the preform  1 . The closed-end tube  9  forms the greater part of the length of the preform, and terminates at the rim portion. There is a transverse or annular flange  8  extending outwardly from the top end of the tube  9 . 
         [0147]    The annular or outwardly-extending flange has an upper surface and a lower surface. The upper surface is in part over the tubular wall portion, which thus depends from the inner edge of the flange. The upper surface carries an upstanding first detent  10  at or towards its radially inner edge. The detent on its inner periphery is generally perpendicular to the upper surface, and on its outer face is generally perpendicular to the upper surface. 
         [0148]    The outer end of the flange has an upwardly extending second detent  11 . Towards the middle of the flange, approximately half way between the first detent and second detent, there is a third upwardly extending detent  12 . 
         [0149]    The lower surface of the flange carries a first downwardly extending flange  13  towards its outer end. There is also a second downwardly extending flange  14  extending from the lower surface of the flange, towards the middle of the flange, approximately half way between the first detent and second detent. 
         [0150]    The preform is transferred to a pressure moulding (or blow moulding) machine, a section through which is shown in  FIGS. 2 and 3 . 
         [0151]    The operation that takes place in the pressure moulding machine is to (1) expand the tube portion of the container to fill the inside of the mould and form the body of the container and then (2) move the first detent downwardly and outwardly, relative to the second detent. 
         [0152]    The mould parts of the machine define the final shape of the container. The exterior part of the body of the container is defined by three mould parts, namely two generally semi-cylindrical side mould parts  6  separable at an axial plane, and a base plate  7  forming the base of the container. The blow mould also includes neck splits carried by a neck split carrying plate. 
         [0153]    The blow mould also includes a piston  15  which can exert a controlled pressure of 600 kPa or higher, e.g. from 1000 to 1500 kPa, for from 0.1 to 1 s, e.g. about 0.5 s. The piston is provided with a stop so that it can only move a controlled, predetermined, distance. 
         [0154]    The pressure moulding machine includes a corridor  15   a , within which the piston  15  can move. The first detent can be located within this corridor. When the preform  1  is in the machine a wall of the corridor contacts the preform at a point between where the tube  9  extends from the radially inner end of the flange  8  and the first detent  10 , such that the wall forms a barrier between the first detent and the parts of the preform exposed to the pressure that is applied to expand the tube. This therefore ensures that during the expansion of the tube under pressure, the first detent  10  is not exposed to the pressure and so does not move downwardly and outwardly at that stage. 
         [0155]    When the preform  1  is first inserted in the moulding machine, it is carried by the exterior portion of the rim, and in particular the second detent  11  on the exterior of the rim, engaging with correspondingly-shaped portions on the lower internal surface of the neck splits. The operation of the moulding machine in shaping the container will now be described with reference to  FIGS. 3 to 5 . 
         [0156]    During the step of expanding the tube portion, the first detent is protected from the effect of the pressure due to the piston  15  and the associated corridor  15   a  in which it moves shielding the first detent from the pressurised air. 
         [0157]    During the step of moving the first detent, 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 of the flange now faces inwardly rather than upwardly, and forms the inward part of the mouth of the container. The first detent now projects inwardly into the container opening. In this position, as described below, a lid can be push-fitted onto the rim portion of the container, to engage the first, now inwardly facing, detent. 
         [0158]    In more detail therefore,  FIG. 5  shows the preform  1  in the moulding machine, with the blow core  16  of the moulding apparatus now inserted in the mouth of the is 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  17  which can be extended to reach the bottom of the mould cavity, as described below. The longitudinal passage through which the blow pin 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 of the preform. An air inlet guide bush is provided within the blow core. The blow core extends into the tubular section below the periphery of the rim portion of the preform. 
         [0159]    The next stage is for the blow pin to be extended. The blow pin is now fully inserted into the mould cavity, causing the production of a stretched tubular section  1   a  which is stretched longitudinally down to the bottom end of the mould, as shown in  FIG. 4 . This stretching operation is important in providing strength to the finished container when made of PET or PEN. 
         [0160]    Next, air under pressure is injected through the passageway in the blow core and around the blow pin into the interior of the container, as shown by arrows B in  FIG. 5 . The effect of this is to expand the tubular section into the shape of the container  18  as defined by the interior surfaces of the mould parts, forming the desired final shape of the container. 
         [0161]    The mould parts may carry desired shaping to provide a more complex shaping for the container in well known manner. 
         [0162]    The expansion of the tubular part will of course cause thinning of the container wall. 
         [0163]    The final step is that the piston  15  moves downwardly due to air pressure from air inlet C to exert a downward pressure on the first detent  10 , which is moved downwardly and outwardly, relative to the second detent  11 , forcing the upper surface of the flange  8  to face inwardly. The second detent  11  is retained in position by its engagement with the neck splits. 
         [0164]    Due to the fact that the plastic is at an elevated temperature, the underside of the flange melts into and becomes homogeneous with the downward flange  14 , thereby providing strength and solidity to the structure. 
         [0165]    The container  18  is now removed from the mould and is shown in  FIG. 7 . 
         [0166]    One version of a lid  19  for the container will now be described with reference to  FIGS. 8 and 9 . 
         [0167]    The lid  19  has a peripheral trough  21  suitable for receipt of and engagement with the first upwardly facing detent. The lid also has an engaging portion  22  located radially inwardly from the peripheral trough for receipt under and engagement with the inwardly facing first detent  10 , to secure the lid on the container. 
         [0168]    The engaging portion  22  is discontinuous around the lid. There are four regularly spaced sections making up the engaging portion. Accordingly, the engagement of the engaging portion with the inwardly facing first detent  10  provides a push and twist, bayonet style, fastening of the lid to the container. 
         [0169]    The peripheral trough  21  is defined between an inner cylindrical flange  21   a  and an outer cylindrical flange  21   b . The inner cylindrical flange is fixed, whilst the outer cylindrical flange is hinged, being a “click-lock” type hinge. Specifically, it moves about hinge  21   c  so that it can move from an open position where it does not engage with the first upwardly facing detent (as shown in  FIG. 9 ) to a closed position where it does engage with the first upwardly facing detent. 
         [0170]    The outer cylindrical flange is discontinuous and is made up of six regularly spaced sections. 
         [0171]    The lid may be polyethylene or polypropylene. 
         [0172]      FIG. 10  shows a side view of two completed containers with their lids attached. The lid  19  is securely held on the container  18 . The containers also have handles  20 . Due to the narrow width of the rim of the container as compared to the body, the handles can be provided without affecting the overall width of the container and therefore improved side by side stacking can be achieved, as shown. 
         [0173]    An alternative embodiment of the container is shown in  FIG. 11 , and the lid for the alternative container is shown in  FIGS. 12 and 13 . This container  28  and lid  29  are the same as those described above with reference to  FIGS. 1 to 10 , except for the following details. 
         [0174]    The container  28  is provided with external lugs  32 . These lugs are provided on the injection moulded preform from which the container is formed and are unaffected by the pressure blow moulding of the container. The lugs are provided on the outer surface of the first downwardly extending flange  13 . 
         [0175]    The container has four regularly spaced lugs  32  around its outer periphery. 
         [0176]    The lid  29  has a peripheral trough  31  and an engaging portion  30  as above; however the peripheral trough  31  is defined between a fixed inner cylindrical flange  31   a  and a fixed outer cylindrical flange  31   b.    
         [0177]    The fixed outer cylindrical flange  31   b  is shaped to engage with the external lugs  32 , so that the lugs hold the lid in place on the container. 
         [0178]    A preferred embodiment of the invention has been described by way of example. However, many modifications may be made to the method, apparatus, container and container top described, and the foregoing description should be regarded only as one example of the implementation of the invention.