GB1568369A

GB1568369A - Method and apparatus for forming the rim of a container

Info

Publication number: GB1568369A
Application number: GB44836/75A
Authority: GB
Original assignee: Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1976-10-28
Filing date: 1976-10-28
Publication date: 1980-05-29

Description

(54) METHOD AND APPARATUS FOR FORMING THE RIM OF A CONTAINER (71) We, METAL Box LtMrrED, of Queens House, Forbury Road, Reading RGI 3JH, Berkshire, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement This invention relates to the manufacture of wide-mouthed plastics containers such as are used as tubs for soft margarine, disposable drinking cups and the like. The invention concerns the formation of such articles with peripheral rims; in the finished article these rims may serve to attach a closure as by snapengagement or clinching, or they may merely provide for the container a smooth terminal edge of pleasing feel and appearance, such as would be the case with disposable drinking cups.

In a first aspect the invention provides a method of reforming the rim of plastics container preform of the kind having a body portion extending outwardly and upwardly from a base to a ledge supporting a rim in the form of an inverted groove around the preform mouth without application of heat, said rim being formed of an upper portion of the body wall converging generally towards the mouth, a down-turned skirt portion arranged outside the upper wall portion in spaced relationship thereto, and a flange portion joining the upper wall portion to the skirt portion and forming a substantially plane terminal surface for the preform, said method comprising the step of applying axially directed pressure between a first surface engaging the said terminal surface of the preform and a second inwardly sloping surface slidingly engaging with the skirt portion at least at the free edge thereof so turning said skirt portion inwardly of the preform towards the flange portion. According to one method a boss is inserted into the mouth of the preform to provide a restraint against any inward deformation of the rim. According to another method the upper wall portion is surrounded to provide an external restraint against any substantial outward deformation during reforming of the rim. A further external restraint may be applied to confine the skirt portion before and during the reforming of the skirt portion.

In a second aspect the invention provides a method for further reforming a preform which has been reformed in accordance with the method from the first aspect and which has an annular ledge joining the upper wall portion to the remainder of the body wall and disposed so as within the preform to present an annular surface facing inwardly towards the preform mouth, the method comprising the further steps of, subsequent to the reforming of the skirt in accordance with the method in the first aspect, placing a lid in the ledge with its periphery adjacent the upper wall portion, and applying axial pressure to the preform by oppositely directed engagement with the said terminal surface in the one hand and the underside of the ledge on the other whereby to snap engage the reformed skirt portion under the ledge and fold a portion of the upper wall portion into retaining engagement with the lid.

In a third aspect the invention provides apparatus for reforming a rim of a plastics container preform, fetid rfm 'os-st'ng of an upper portion of the body wali which converges towards the preform Ir,oilth, a downturned skirt portion arranged outside the upper wall portion in spaced relationship thereto and a flange portion joining the upper wall portion to the skirt portion and forming a substantially plane terminal surface for the preform, said apparatus comprising a first tool adapted to engage the terminal surface of the preform and a second tool having an inwardly sloping surface adapted to slidingly engage the skirt portion at least at the free edge thereof said first tool and said second tool being arranged for relative movement towards and away from one another whereby to turn the skirt portion inwardly of the preform towards the flange portion.

The apparatus may optionally include a boss adapted for entry into the mouth of the container where it provides a restraint against inward deformation of the rim. The apparatus may further include a hollow tube portion to sleevingly engage the upper wall portion; and a further hollow tube portion adapted to sleevingly engage the skirt.

In a fourth aspect the invention provides apparatus for reforming the rim of a plastics container preform which includes an annular ledge joining the upper wall portion to the remainder of the body wall and disposed so as within the preform to present an annular surface facing upwards towards the preform mouth, the apparatus comprising further tooling in the form of a third tool having a generally plane bottom surface to engage with the terminal surface of the reformed preform, and a fourth tool adapted to engage with the underside of the said ledge, said third and fourth tools being arranged for relative movement towards and away from one another whereby by applying axial pressure to the preform to snap engage the reformed skirt portion under the ledge and fold the upper wall portion into engagement with a lid resting upon the ledge to retain the lid in position.

In a fifth aspect the invention provides containers made according to the method or by means of the apparatus according to the inven tiOn.

Various aspects and features of the invention will now become apparent from the following description of various embodiments thereof, given by way of example and with reference to the accompanying drawings. In the drawings: FIGURE 1 shows, in section on a diametral plane, a plastics preform of circular crosssection and having a rim to be reformed; FIGURE 2 is a view in central vertical section of an apparatus embodying the invention when in use to reform the rim of the preform of Figure l; FIGURE 3 shows the preform after reforming by the apparatus of Figure 2 and when closed by a snap-fitted plastics lid; FIGURE 4 is a sectional view of part of the apparatus in a modification thereof and at the beginning of a reforming operation; FIGURE 5 similarly shows the apparatus of Figure 4 at the end of the reforming operation; FIGURE 6 shows the reformed preform of Figure 3 when fitted with a closure disc and preparatory to the clinching of the closure disc into position to close the preform; FIGURE 7 is a view corresponding to Figure 2 and showing a further apparatus embodying the invention at the beginning of its operation to close the preform of Figure 6.

FIGURE 8 shows the preform of Figure 6 after closure; FIGURE 9 is a sectional view of part of the apparatus of Figure 7, in a modification thereof and when at the beginning of an operation to reform again the rim of the preform; FIGURE 10 similarly shows the apparatus of Figure 9 at the end of the reforming operation; and FIGURE Il shows a detail of the preform of Figure 6 when reformed to a different rim configuration than is achieved as shown in Figures 9 and 10.

Referring to Figure 1, a circular preform 9 for a margarine tub is thermoformed in conventional manner from A.B.S. plastics sheet material having a nominal thickness of 750 microns. It is formed of a generally plane base 10 and a body wall 11 which extends upwardly and outwardly from the base in a generally flared manner as shown.

The body wall 11 is formed of a lower, upwardly flared frustoconical portion 12 extending from the base periphery, an upper, upwardly convergent frustoconical portion 13 of substantially smaller length than the portion 12 and joined to that portion by a generally horizontal ledge portion 14, a flange portion 15 extending outwardly from the upper end of the portion 13 and providing a plane and annular terminal face 16 for the preform, and a downturned rudimentary skirt 17 carried around the periphery of the flange portion 15 and providing the free edge 18 of the preform as a whole. The edge 18 is formed by trimming flash from the preform after moulding, and takes the form of an outturned edge asperity.

It will particularly be noted that the elbow 40 formed at the junction between the flange portion 15 and the upper frustoconical portion 13 lies on a slightly greater radius than the further elbow 41 formed between the ledge portion 14 and the lower frustoconical portion 12; furthermore, the skirt 17 as a whole lies on a greater radius than the elbow 42 joining the portions 13 and 14. The further elbow by which the skirt is joined to the flange portion 15 is denoted 43.

The upper frustoconical portion 13, the flange portion 1 5 and the skit 17 together provide the preform with what can be considered as a peripheral rim forming around the preform mouth an inverted and generally Ushaped groove or channel. For ease of identification this rim is denoted generally by the reference numeral 100.

Figure 2 shows an apparatus by which the rim 100 may be reformed to adapt it for engagement by a conventional snap-on plastics cover 19 with a necked-in peripheral skirt 119, as shown in Figure 3. Referring now to Figure 2, the apparatus comprises an upper curling tool 30, and a lower curling tool which is mounted vertically beneath the upper tool and is generally denoted by the reference numeral 31. Although not apparent from the drawings it is to be understood that the two tools are relatively movable along the central vertical axis XX of the apparatus; conveniently, and as is assumed for this and for the other embodiments later to be described, the lower tool is fixed in position and the upper tool is vertically reciprocable towards and away from it by means not shown.

The lower tool 31 has a generally cupshaped housing 32 having a cylindrical blind bore 33 and surmounted by a curling ring 34, and a cylindrical ejector block 35 which is located generally within the bore 33. The ejector block is vertically slidable along the bore 33 and biassed upwardly by compression springs 36. An upper limiting position of the block is determined by engagement of a peripheral shoulder portion 37 on the block beneath a lower horizontal face 38 of the curling ring where the latter projects radially inwardly beyond the housing bore 33. Above the shoulder portion the block has a cylindrical outer surface 45. The cylindrical peripheral surface of the shoulder portion is denoted 81.

The inner bore or surface of the curling ring 34 is partly cylindrical and partly frustoconical.

The cylindrical part, denoted 57, has a diameter which is chosen to be equal to, or slightly greater than, the nominal overall diameter of the elbow 42 of the preform 9 to be reformed; the diameter of the surface 57 is, however, considerably smaller than the diameter of the elbow 43 and free edge 18 of the preform.

The part 58 of the inner surface of the curling ring 34 extends upwardly and outwardly from the top end of the part 57 thereof as a frustoconical reforming surface. The outer peripheral limit of this surface lies on a greater diameter than the free edge 18 of the preform 9.

The upper tool 30 is generally cylindrical, having a nominal overall diameter at a cylindrical surface 80 which is the same as that of the preform. At its lower end the upper tool is reduced in diameter at a horizontal annular shoulder 59; below this shoulder it forms a generally cylindrical boss 60 defined by a circular and horizontal bottom face 61 , a cylindrical and vertical side face 62, and an arcuate peripheral concavity 63 joining the faces 61, 62 around the lower terminal edge of the upper tool.

For operation a preform 9 as shown in Figure 1 is placed manually or automatically in position on the lower tool 31 when the upper tool 30 is in a retracted upper position in which it is spaced above the lower tool. As can be understood from Figure 2, the preform then has the part of its lower surface provided by the frustoconical portion 12 and ledge portion 14 snugly engaged by the ejector block 35 at a correspondingly shaped frustoconical recess 64 and peripheral rim 65 of the latter.

The base 10 and rim 100 of the preform are however, free of all engagement by the ejector block or, indeed, the lower tool 31 as a whole.' With the preform supported in this matter the upper tool 30 is progressively lowered towards the lower tool 31. The diameter of the boss 60 at its surface 62 is slightly less than that of the elbow 40 of the preform, with the result that the movement of the upper tool causes the boss to enter within the mouth of the preform and shortly thereafter to snugly engage its recess 63 with the preform in the region of the elbow 41. Further and substantially simultaneous face-to-face contact between the upper tool and preform also occurs between the horizontal faces 59 and 16 of those two items.

After the engagement of the upper tool and preform as described above, continued downward movement of the upper tool carries the preform 9 and ejector block 35 downwardly together against the action of the springs 36, any necessary lateral location for the combination being provided by sliding engagement of the surface 81 of the shoulder portion 37 with the housing bore 33. Since the upper tool and ejector block are directly opposed to one another where they cooperate through the preform in the region of the elbow 41, the preform suffers little or no deformation by reason of the vertical forces which it transmits between them.

At the beginning of the downward movement of the preform the free edge 18 of the latter is clear of the frustoconical reforming surface 58 of the lower tool. Continuing movement of the upper tool, however, brings the edge 18 into engagement with the surface 58, and the latter, by virtue of its inclination to the horizontal, thereafter forces the skirt 17 to move inwardly by pivotal deformation at the elbow 43. This movement is accompanied by sliding of the edge 18 inwardly along the surface 58; to that end the surface 58 may have a special coating or treatment to give it hardness together with a low coefficient of friction.

The downward movement of the upper tool, and thereby the deformation of the preform 9, is stopped at the position of the upper tool depicted in Figure 2; by this time the desired degree of reforming of the skirt 17 has taken place, the skirt 17 having adopted the angle of the surface 58 which is chosen accordingly. The upper tool is then retracted to allow the ejector block to return to its upper limiting position under the action of the springs 36 and there after to separate the tools, after which the finished container, denoted 9' in Figure 3, may readily be removed for subsequent filling with product and fitting of a snap-on plastics closure 19 as shown.

During the reforming operation described above, any tendency for the preform to be permanently deformed otherwise than at the elbow 43, and to a lesser extent, the skirt 17 is prevented by restraining engagement of the preform with the surfaces 59, 62 and 63 of the upper tool 30, and with the surface 57 and, as previously described, the surfaces 64 and 65 of the lower tool 31. In particular, the upper frustoconical portion 13 of the preform is prevented from permanent deformation radially of the preform by engagement of the surfaces 62 and 57 with, respectively, its inside and outside faces. In the interests of clarity the length and cone angle of the portion 13 have been exaggerated in the drawings; in reality the clearance provided between the surfaces 62, 57 will be only marginally greater than the expected thickness of the plastics material of the preform in that region.

Although buckling of the portion 13 may occur, it will therefore be only temporary, being insufficient in magnitude to create permanent deformation in the finished container 9'.

In a variation of the arrangement shown in Figure 2 lateral location for the preform is provided by mutual engagement of the cylindrical surfaces 45, 57 in addition, or alternatively, to engagement of the surfaces 81, 33 as described above.

Figures 4 and 5 show a modification of the apparatus of Figure 2 at, respectively, the beginning and end of a reforming stroke.

The modified apparatus is identical to the original, with the exception of the reforming surface 58 which is contoured rather than frustoconical. The configuration of the reforming surface will become apparent from the following description of its performance during a reforming operation.

During the downward stroke of the upper tool 30 as previously described, the free edge 18 of a preform 9 to be reformed first engages the reforming surface at a frustoconical entry portion 70, by means of which the permanent inward deflection of the skirt 17 is begun. As will be seen from the drawing, the cone angle of the portion 70 is relatively small, typically 3or .

The edge 18 passes from the portion 70 onto a further surface portion 71 which is cylindrical so that the surface 58 causes little or no deformation of the preform during the time that the edge is traversing it. The reforming operation is thereby subject to a dwell period while this occurs. The diameter of the portion 71 is made slightly greater than that of the upper tool 30 at the surface 80 for a reason later to become apparent.

From the portion 71 the free edge passes via a radius 73 onto a further frustoconical portion 72. This portion has a large cone angle and is largely responsible for the reforming of the preform, the finished condition of the latter being shown as in Figure 5.

During reforming by the surface portion 72 the upper and lower tools 30, 31 are firmly restrained against relative movement in a lateral sense by suitable means not shown. If desired, lateral location may be provided by mutual engagement of the surfaces 81,33 and/ or 45,57 as previously described.

As before modification, the apparatus of Figures 4 and 5 provides both inwardly and outwardly radial restraint for the upper frustoconical portion 13 of the preform while the rim 100 is being reformed. Thus the apparatus of Figures 2 and 4,5 achieve, when stated in general terms, a method of forming a wide-mouthed plastics container with a rim, which method comprises: providing a wide-mouthed plastics preform having a base and a body wall extending peripherally from the base to a rim portion which provides an inverted peripheral groove around the container mouth, the rim being formed of an inner portion comprising the upper region of the body wall converging generally towards the mouth, and a downturned skirt portion arranged in spaced and outwardly concentric relation with the inner portion and joined to the same by a flange portion forming a generally plane, circular terminal surface for the preform, the method further comprising reforming the rim portion whilst the inner portion is restrained from radial movement both in the inward and outward directions, the reforming being achieved by slidingly engaging the free edge of the skirt portion so as with axial pressure applied to the skirt portion to force the same inwardly of the preform and towards the flange portion against a support engaged with the terminal surface.

Figures 6,7 and 8 illustrate how, as an alternative to Figure 3, the already reformed preform 9' may be provided with a closure.

As shown in Figure 6, the closure is in the form of a circular cardboard disc 20 which is placed in the mouth of the preform so as to be peripherally supported by the ledge portion 14, the diameter of the disc being chosen accordingly.

After, or possibly before, the disc 20 is placed in position the preform is received in a tool 131 which receives and supports it in the manner of the ejector block 35 of Figure 2. Accordingly, the tool 131 has a recess with a frustoconical surface 64 and rim 65.

As shown in Figure 7, the tool 131 is the lower of two tools which are vertically reciprocable by suitable means and which together form a second apparatus embodying the invention. The upper one of these tools, denoted 130, has a plane and horizontal lower surface 21 of larger diameter than the overall diameter of the preform. The surface 21 is hard, with a lower coefficient of friction.

In order to reform the preform to form a closed container 9" (Figure 8), it is merely necessary to bring the tools 130,131 together.

After contacting the preform at its terminal surface 16 as depicted in Figure 7, further relative downward movement of the tool 130 towards the tool 131 causes a lower part 23 of the upper frustoconical portion 13 to move progressively and generally in a radially inward direction, by flexing generally about the top free edge 22 of the disc 20 as a fulcrum. At the same time as this is happening the portion 13 progressively buckles approximately midway up its free length along the broken line 25 in Figure 7, with the result that while the lower part 23 of the free length is being deformed inwardly towards the disc 20, the remainder 24 of the free length is deformed outwardly in relation to the part 23.

This latter movement is accompanied by sliding and, latterly, tilting movement of the flange portion 15 on the tool surface 21, and so causes the skirt 17 to move downwardly and snap resiliently over the elbow 26 (Figure 8) which is in the process of being formed by the portions 13,14 around the edge of the disc 20.

The relative movement of the two tools 130, 131 is halted when the upper part 24 of the portion 13 is horizontal and in firm contact with the lower part 23, the latter itself being horizontal and in firm contact with the disc 20. By this time the snapengagement of the skirt 17 has occurred so that, as can be appreciated from Figure 8, the preform, now the finished container 9", is provided with a secure closure with good sealing properties and of pleasing appearance. The tools are then separated to release the container. If desired, one or more sealing rings of a resilient material may be provided on the ledge portion 14 andlor the peripheral margin of the disc 20 to improve the seal between them. Such a ring may be of a flowed-in compound, or it may be a separate, preformed item.

In the modification of the second embodiment depicted in Figures 9 and 10, the lower tool 131 comprises an inner part 101 formed with the recess 64 and rim 65, and an encircling outer part 102 arranged concentrically on the inner part. The inner part is, as before, fixed in position; the outer part, however, is slidable vertically on the inner part and biassed upwardly by springs (not shown) to the limiting position shown in Figure 9, in which its top surface 104 is flush with the rim 65.

The top tool 130 carries a spacer post 103 arranged to contact the part 102 as the upper tool descends. Otherwise it is identical to the like-numbered upper tool of Figure 7.

After a reformed preform 9' (Figure 3) has been received on the recess 64 and rim 65 of the part 101 in the manner previously described, the upper tool 130 is lowered to effect the second reforming operation. This operation is substantially as described in relation to Figure 7, that is to say, the free-standing portion of the upper frustoconical portion buckles along a line 25 so that the skirt 17 moves outwardly and downwardly past the elbow 26 which is in the process of being formed around the periphery of the disc 20, the skirt then snap-engaging beneath that elbow so as again to provide an aesthetically pleasing and secure finish to the finished container.

The outer part 102 of the lower tool acts to provide restraint beneath the preform at the elbow 26 while the latter is in its formative stages. As can be understood from Figure 10, which shows the container - now denoted 9" - in its finished condition ready for removal, the spacer post 103 later drives the part 102 downwardly against its associated biassing springs and by so doing enables the skirt 17 to be accommodated beneath the elbow 26. An outer member similar in function and arrangement to the part 102 may, if desired, be provided for the apparatus shown in Figure 7; correspondingly the part 102 may be omitted from the arrangement of Figures 9 and 10.

The use of a preform 9' which has already been partly formed enables more consistent reforming to be achieved with an improved and tighter rim formation.

As previously described, the reforming operations performed by the apparatus of Figures 7 and 9,10 involve buckling of the upper frustoconical portion 13 where it lies above the closure disc 20. In an attempt to accurately control the position of the line 25 along which this buckling occurs the portion 13 may be formed of upper and lower frustoconical parts having different cone angles. The cone angle of the upper part is smaller than that of the lower part and may in the limit be zero so that the upper part of the portion 13 is cylindrical. Other methods of locating the position of buckling - for example, localised thinning of the plastics material - may alternatively or additionally be used.

Figure 11 illustrates a modification of the reforming operation involved in Figures 7 and 9,10 in which the whole of the frustoconical portion 13 is reformed downwardly and inwardly so as to snap-engage the skirt 17 over the formative elbow 26; the reforming apparatus is omitted for clarity. Whether or not buckling takes place is determined by suitable choice of the relative d -fn.sions of the preform 9 or 9', the constituent parts of its rim 100 in particular, and other factors such as the closing speed of the upper tool 130 and the coefficient of friction of its operative surface 21, the provision of special features on the portion 13 to assist buckling as previously described or, conversely, to deter it, and the temperature of the preform. In the latter respect it will be noted that although the apparatus of Figures 2,4 and 5,7 and 9 and 10 all perform their reforming operations on preforms 9 or 9' which are at ambient temperature, this is not essential; if desired, heat may be applied to the preform before andlor during reforming. It will be understood that the apparatus of Figures 7 and 9,10 achieve a method which basically differs from the method achieved by the apparatus of Figures 2 and 4, 5 in that the reforming of the rim occurs at the inner portion of the body wall rather than at the skirt portion and, furthermore, the reformation is achieved employing sliding engagement with the flange portion rather than with the skirt portion.

In a modification of the arrangements of Figures 6 to 11 the disc 20 is injection-moulded from plastics material and preferably formed with a tear-away panel having a suitable tab or pull ring attached thereto. The panel is defined by a line of weakening preferably located just inside the marginal area of the disc at which engagement with the container 9' or 9" occurs. This marginal area may desirably be formed with resilient beads or the like to ensure an adequate seal with the container.

The invention may be used in relation to preforms (reformed or otherwise) which have been manufactured by injection-moulding rather than thermoforming as described. The plastics material of the preform may be other than A.B.S. material and may, for example, be polyvinyl chloride, polystyrene or nylon.

Furthermore, the invention is not limited to the reforming of rims on articles or circular cross-section; for example, it has application to containers of square cross-section with rounded corners, such as are used for packaging ice cream for the wholesale and freezer trade. Other shapes of container suitable for application of the invention include the bow sided rectangular formings used for the retail sale of margarine.

WHAT WE CLAIM IS: 1. A method of reforming the rim of plastics container preform of the kind having a body portion extending outwardly and upwardly from base to a ledge supporting a rim in the form of an inverted groove around the preform mouth without application of heat, said the rim is being formed of an upper portion of the body wall converging generally towards the mouth, a down-turned skirt portion arranged outside the upper wall portion in spaced relationship thereto, and a flange portion joining the upper wall portion to the skirt portion and forming a substantially plane terminal surface for the preform, said method comprising the step of applying axially directed pressure between a first surface engaging the said terminal surface of the preform and a second inwardly sloping surface slidingly engaging with the skirt portion at least at the free edge thereof so turning said skirt portion inwardly of the preform towards the flange portion.

2. A method according to claim 1 which includes the further step of inserting a boss into the mouth of the preform so as by providing inward restraint for the upper wall portion to prevent any substantial inward deformation of the same during reforming of the rim.

3. A method according to claim 1 or claim 2 which includes the further step of surrounding the upper wall portion, below the flange portion, with means to provide external restraint for the upper wall portion to prevent any substantial outward

Claims

**WARNING** start of CLMS field may overlap end of DESC **. it, and the temperature of the preform. In the latter respect it will be noted that although the apparatus of Figures 2,4 and 5,7 and 9 and 10 all perform their reforming operations on preforms 9 or 9' which are at ambient temperature, this is not essential; if desired, heat may be applied to the preform before andlor during reforming. It will be understood that the apparatus of Figures 7 and 9,10 achieve a method which basically differs from the method achieved by the apparatus of Figures 2 and 4, 5 in that the reforming of the rim occurs at the inner portion of the body wall rather than at the skirt portion and, furthermore, the reformation is achieved employing sliding engagement with the flange portion rather than with the skirt portion. In a modification of the arrangements of Figures 6 to 11 the disc 20 is injection-moulded from plastics material and preferably formed with a tear-away panel having a suitable tab or pull ring attached thereto. The panel is defined by a line of weakening preferably located just inside the marginal area of the disc at which engagement with the container 9' or 9" occurs. This marginal area may desirably be formed with resilient beads or the like to ensure an adequate seal with the container. The invention may be used in relation to preforms (reformed or otherwise) which have been manufactured by injection-moulding rather than thermoforming as described. The plastics material of the preform may be other than A.B.S. material and may, for example, be polyvinyl chloride, polystyrene or nylon. Furthermore, the invention is not limited to the reforming of rims on articles or circular cross-section; for example, it has application to containers of square cross-section with rounded corners, such as are used for packaging ice cream for the wholesale and freezer trade. Other shapes of container suitable for application of the invention include the bow sided rectangular formings used for the retail sale of margarine. WHAT WE CLAIM IS:

1. A method of reforming the rim of plastics container preform of the kind having a body portion extending outwardly and upwardly from base to a ledge supporting a rim in the form of an inverted groove around the preform mouth without application of heat, said the rim is being formed of an upper portion of the body wall converging generally towards the mouth, a down-turned skirt portion arranged outside the upper wall portion in spaced relationship thereto, and a flange portion joining the upper wall portion to the skirt portion and forming a substantially plane terminal surface for the preform, said method comprising the step of applying axially directed pressure between a first surface engaging the said terminal surface of the preform and a second inwardly sloping surface slidingly engaging with the skirt portion at least at the free edge thereof so turning said skirt portion inwardly of the preform towards the flange portion.

3. A method according to claim 1 or claim 2 which includes the further step of surrounding the upper wall portion, below the flange portion, with means to provide external restraint for the upper wall portion to prevent any substantial outward deformation of the same during reforming of the rim.

4. A method according to all or any of the preceding claims which includes the further step of surrounding the skirt portion with a means to provide external restraint for the skirt portion before and during the application of axial pressure to reform the skirt portion.

5. A method for further reforming a preform which has been reformed in accordance with any of claims 1 to 4 and which has an annular ledge joining the upper wall portion to the remainder of the body wall and disposed so as within the preform to present an annular surface facing upwardly towards the preform mouth, the method comprising the further steps of, subsequent to the reforming of the skirt in accordance with claims 1 to 4, placing a lid in the ledge with its periphery adjacent the upper wall portion, and applying axial pressure to the preform by oppositely directed engagement with the said terminal surface in the one hand and the underside of the ledge on the other whereby to snap engage the reformed skirt portion under the ledge and fold a portion of the upper wall portion into retaining engagement with the lid.

6. Apparatus for reforming the rim of a plastics container preform, said rim consisting of an upper portion of the body wall which converges towards the preform mouth, a downturned skirt portion arranged outside the upper wall portion in spaced relationship thereto and a flange portion joining the upper wall portion to the skirt portion and forming a substantially plane terminal surface for the preform, said apparatus comprising a first tool adapted to engage the terminal surface of the preform and a second tool having an inwardly sloping surface adapted to slidingly engage the skirt portion at least at the free edge thereof said first tool and said second tool being arranged for relative movement towards and away from one another whereby to turn the skirt portion inwardly of the preform towards the flange portion.

7. Apparatus according to claim 6 wherein the first tool has a boss adapted for entry into the mouth of the preform so as to provide an inward restraint for the upper wall portion to prevent any substatial inward deformation of the same during reforming of the rim.

8. Apparatus according to claim 6 or claim

7 wherein the second tool has a hollow tubular portion adapted to sleevingly engage over the upper wall portion below the skirt portion to provide external restraint for the upper wall portions to prevent any substantial outward deformation of the same during reforming of the rim.

9. Apparatus according to all or any of claims 6 to 7 wherein the first tool has a hollow tubular portion adapted to sleevingly engage the skirt portion, before and during the application of axial pressure to reform the rim, and so prevent any substantial outward deformation of the skirt.

10. Apparatus according to any claim of claims 5 to 7 for a preform which includes an annular ledge joining the upper wall portion to the remainder of the body wall and disposed so as within the preform to present an annular surface facing upwards towards the preform mouth, the apparatus comprising further tooling in the form of a third tool having a generally plane bottom surface to engage with the terminal surface of the reformed preform, and a fourth tool adapted to engage with the underside of the said ledge, said third and fourth tools being arranged for relative movement towards and away from one another whereby by applying axial pressure to the preform to snap engage the reformed skirt portion under the ledge and fold the upper wall portion into engagement with a lid resting upon the ledge to retain the lid in position.

11. A container made by a method as claimed in any preceding claim.

12. A method of reforming the rim of a container preform, substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

13. A method of reforming the rim of a container preform, substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.

14. A method of reforming the rim of a container preform to retain a lid thereon, substantially as hereinbefore described with reference to the accompanying drawings.

15. Apparatus for reforming the rim of a container substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

16. Apparatus for reforming the rim of a container substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.

17. Apparatus for reforming the rim of a container substantially as hereinbefore described with reference to the accompanying drawings.