ASEPTIC PACKAGING PROCESS AND APPARATUS

Abstract: Thin-walled can bodies (10) made by the DWI process are aseptically filled with a non-carbonated liquid food product at ambient temperature. The aseptic process comprises, within a sterile environment, sterilising the can bodies by hot air in a first oven (36) and filling them in a filler (40) with a metered dose of the product, sterilising end closures (11) for the cans in a second oven (42) again by hot air, and placing the end closures on the cans whilst still at an elevated temperature so as to form closed packages having a temporary aseptic seal, moving the closed packages from the sterile environment, and, subsequent to the sterile environment, double-seaming the end closures onto the can bodies to form hermetically sealed cans, and reforming the end closures inwardly of the cans so as to create in the cans a positive internal pressure by which panelling of the can side walls may be resisted.

Description: "ASEPTIC PACKAGING PROCESS AND APPARATUS" This invention relates to the aseptic packaging of liquid food products, and provides a process and an apparatus for such packaging. It is well known and commercially practised to aseptically package liquid food products such as fruit juices in rectangular containers made of a paper-based laminate. Aseptic packaging in other materials such as plastics and metal is less well known, although various proposals have been made to do so. In particular, there already exist on the UK market aseptically packed cylindrical cans of a food product, fabricated in the manner well known for cans of the kind which are destined to be closed onto a food product and subsequently sterilised thermally in a steam or water/steam retort. Such cans are made of a body which is formed by bending to cylindrical form and edge-welding a piece of rectangular plate of substantial thickness and rigidity, and circular end closures which are attached by double- seaming to respective ends of the body to complete the enclosure. One end closure is fitted by the container manufacturer, that is to say, before the container is filled with product, whereas the other end closure is fitted by the packer after filling. Such containers are usually known in the art as "3-piece cans". A known general desideratum for packages of food products, particularly those having a container made of metal, is that the container should be resistant to panelling when closed and/or after opening. Patent specification GB 2089191 (Toyo Seikan) describes a method of preventing or reducing panelling of containers which have been aseptically filled with a food product, and proposes that for this purpose either a metered dose of liquid nitrogen (or other inert gas) should be placed in the headspace of the container before closing, or alternatively nitrogen should be dissolved in the product and charged together with the product into the container. With either of these alternatives the nitrogen creates an increased gas pressure within the container after closing, so reducing the danger that inward pressure on the side wall of the closed container will panel the side wall with consequently increased risk of leakage and reduced consumer acceptance. However, the use of nitrogen or other inert gas in an aseptic swterilisation process such as is described in GB 2089191 has several drawbacks; especially where the gas is injected in a liquified form it is difficult and expensive to dose the required quantity of gas accurately into the container, and to keep it there until the container can be subsequently closed so that the gas can no longer dissipate. A further method of creating an increased pressure in the headspace of a food product container is known from GB patent specification No. 1235060 (J J Carnaud) , in which a three-piece can containing a food product is thermally sterilised after filling and closing. In order o prevent possible panelling of the can side wall caused by the subatmospheric pressures which will otherwise occur inside the can as it and its contents cool to ambient temperatures, the end closures of the can are deformed inwardly so as to counteract any pressure reduction. However, the reforming operation must be performed at a time when the can is still hot and so already has an elevated internal pressure the magnitude of which may vary within wide limits. The pressure increase which can be safely generated by the reforming operation is therefore limited. The present invention is concerned with food products which are packed cold, that is to say, at a temperature which is equal or close to ambient temperatures and typically within the range 5°C to 40°C, and seeks to provide a method and apparatus for aseptically packaging the product in a reliable and simple way. In accordance with the invention from a first aspect there is therefore provided a process for aseptically packaging a liquid food product substantially at ambient temperature in metal containers each comprising a body and an end closure, the body having a thin side wall liable to panelling, the process being characterised by the following operations :- (a) passing the empty container bodies through a heated enclosure to sterilise them and any gas within them; (b) passing the end closures through a further heated enclosure to sterilise them; (c) moving the sterilised container bodies to a product filler at which a predetermined dose of the said liquid food product is charged into them individually substantially at ambient temperature; (d) placing the sterilised end closures individually on the product-charged container bodies so as to form closed packages having a temporary aseptic seal; steps (a) to (d) above being carried out within a continuously sterile environment; (e) removing the closed packages from the sterile environment, and, whilst so removed, (f) uniting superimposed marginal edges of the end closures and container bodies so as to render the closed packages hermetic; and subsequently (g) reforming the hermetic packages to generate a positive pressure therein. European Patent Specification EP 059097 (James Dole Corpn) describes a method possessing some of the features of the invention, but it will be noted that no reforming operation is carried out (operation ' g') . Moreover the end closures and container bodies are permanently united within the sterile environment, which may be aggressive to the closing maching; also, access to the closing machine may be impeded. Performing a double-seaming operation outside the sterile environment of an aseptic packaging process is disclosed in EP 0181879 (CMB Packaging), but the containers used in the process are 3-piece cans and again no reforming operation is carried out. GB Patent Specification 2124597 (Vaux Breweries) discloses that lightweight thin walled cans may be supported internally by pressure generated either by a vaporised gas or by inward deformation. However no detail is given for the aseptic packaging process to be used. From a second aspect the invention provides an apparatus for aseptically packaging a liquid food product substantially at ambient temperature in metal containers each comprising a body and an end closure having a central panel, the body having a thin side wall liable to panelling, the apparatus being characterised by the following components : - (a) a first sterilising oven supplied with a heated gas and adapted for sterilising the container bodies and any gas within them; (b) a second sterilising oven supplied with a heated gas and adapted for sterilising the end closures; (c) a product filler adapted for charging a predetermined dose of the said liquid food product substantially at ambient temperature into the sterilised container bodies; (d) a combiner adapted for placing the sterilised end closures individually on the sterilised and product- charged container bodies so as to form therewith closed packages having a temporary aseptic seal; (e) a sealer adapted for uniting superimposed marginal edges of the end closures and container bodies to render the closed packages hermetic; (f) a reformer adapted for reforming the central panels of the end closures of the hermetically closed packages to generate a positive pressure therein; (g) drive means arranged to move the container bodies and end closures substantially without interruption through components (a) to (f) as appropriate; and (h) a sterile environment for the container bodies and end closures between their entry to the appropriate sterilising oven and their exit together from the combiner, the sterile environment not extending to the sealer or the reformer. The above and other aspects and preferred features of the invention will be apparent from the following description of a process and apparatus embodying the invention, the description being given, by way of example only, with reference to the accompanying drawings. In the drawings : - Fig.l diagrammatically shows a product-filled can and an end closure prior to placement of the end closure on the can for forming a temporary aseptic seal therewith; Fig.lA shows the end closure as it is formed, and prior to its first reforming stage for placement on the can; Fig.2 is a block diagram showing the aseptic packaging process for which the can and end closure of Figs. 1 and 2 are used; Fig.3 is a diagrammatic perspective view of the apparatus used for performing the packaging process; Fig. is a general arrangement of the apparatus as seen in side elevation; Fig.5 similarly shows the apparatus as seen from above; Figs. 6A and 6B are diagrammatic views showing respective halves of the stator of the can sterilising pven; Fig.7 shows the can sterilising oven generally in central vertical section; Fig.8 is a plan view of the can sterilising oven as seen in section on line X - X of Fig.7; Fig.9 similarly shows the can sterilising oven as seen in section, but with the rotor removed for clarity; Fig.9A is an enlarged view of the intersection between the two halves of the oven of Fig.9; Fig.10 shows cans passing down the helical track of the rotor of the can sterilising oven; Figs.11 and 11A show the inlet gas lock to the can sterilising oven, respectively in plan view from above and in end elevation; Fig.llB diagrammatically shows a can passing through the inlet gas lock when driven by a rotating scroll. Figs.12 and 12A are views similar to Figs. 11 and HA of the filler gas lock of the can sterilising oven; Fig.13 shows, in central longitudinal section, the filling device by which each sterilised can in turn is charged with a metered dose of product after its sterilisation in the can sterilising oven; Fig.l3A shows the filling device in transverse section taken on the line XIIIA-XIIIA of Fig.13; Fig.14 is a diagrammatic view of the end closure sterilising oven; and Fig 15 is a diagrammatic view of the apparatus, showing the scrolls used for transporting cans between sections of the apparatus. Referring firstly to Figs 1 to 5, the method and apparatus which are described below are designed to package a liquid food product aseptically in cans closed by easy-opening end closures. Typically the food product is a still (i.e. non-carbonated), milk-based product. One of the cans 10 and an associated aluminium alloy end closure 11 are shown in central vertical section in Fig.l, as they appear immediately prior to placement of the closure on the product-filled can and the temporary formation of an aseptic seal between superimposed seaming flanges 12 and 13 of the closure and the can as will be described. The can 10 has been conventionally formed by a drawing and wall-ironing (DWI) operation from tinplate or aluminium, and accordingly it has an integral base formed with a central recess 14 and surrounding stand ring 15. A particular feature of the can (which is not apparent from the drawing) is the thinness of its cylindrical side wall 16 in relation to the wall thicknesses which are normally employed for food cans destined for sterilisation in a conventional steam or water/steam retort. The minimum wall thickness of the can lies within the range 0.068mm to 0.084mm, especially 0.07mm, for tinplate, and within the range 0.096mm to 0.114mm, especially 0.1mm, for aluminium. This can be compared with the wall thickness of a conventional tinplate food can, which is typically 0.14mm to 0.17mm. The can side wall 16 has a simple cylindrical shape, with no beading, fluting or the like such as has been proposed to impart rigidity to thin-walled cans. In order to strengthen it against axial loading and panelling, it is proposed that the can 10 after filling and closing should be artificially pressurised. For that purpose the closure 11 has a central panel 17 which has peen reformed to the raised position shown in Fig.l and which after closing is mechanically and permanently inverted to a lowered position which it had when the closure was originally pressed. In this lowered position the central panel will project towards the interior of the completed pack, as can be understood from Fig.lA which shows the lowered position denoted by the reference 17' . Despite the two reforming operations performed upon it, in the completed pack the central panel 17 is capable of bulging or "blowing" to indicate product spoilage at pressures of a magnitude which is typical for food products. It is proposed to pressurise the can to within the range 0.5 to 2 bar, whereas the central panel is designed to "blow" at pressures within the range 2 to 4 bar. The central panel 17, should be understood as having a tear-away portion defined by a score line, neither of which are specifically indicated. A tab 18 attached by rivet 19 enables the tear-away portion to be removed for providing user pouring access to the product in well known manner. The closure 11 forms the subject of GB patent Applications Nos. 9707678.0 and 9707688.9 which were filed by the present Applicants on the same day as the GB Application No. 9707687.1 from which priority is claimed for the present Application. These further GB Applications were respectively entitled "Container End Manufacture" and "Container Ends" (Agents refs: 4930, 4931), and the reader is referred to them and any Application deriving priority from them for further information in particular regarding the method proposed for forming the end closure and the material of which it is made. ASEPTIC PACKAGING SYSTEM The general arrangement of the aseptic packaging system can be understood from Fig.2 which is a block diagram of the functional stages employed in the packaging process. Referring now to Fig.2, the process comprises sterilisation of the empty cans 10 by a thermal sterilisation operation 20, after which the cans are filled with a measured dose of a cold but sterile liquid product 82 in a filling stage 22. Simultaneously with these operations, easy-opening end closures 11 destined to close the cans are sterilised by a thermal sterilisation operation 24. The sterilised and product- filled cans are fitted loosely but aseptically with the sterilised end closures in a combining operation 26, following which they and the end closures on them are subjected to a seaming operation 28 by which the cans and end closures are double-seamed together at their seaming flanges 13,12 to form a closed pack having a permanent hermetic seal. The process is completed by a reforming operation 30 by which the end closures of the packs are reformed inwardly so as to pressurise the pack internally for the purpose described above. The closed and internally pressurised packs are denoted 32 in Fig.2 as they emerge from the apparatus on a conveyor 52. The apparatus by which the packaging process of Fig.2 is performed is shown as a diagrammatic perspective a view in Fig.3 and as a general arrangement in Figs. 4 and 5. From those drawings in combination with Fig.2 it will be understood that the apparatus has a welded tubular support frame 34, and includes a can sterilising oven 36 with associated scroll 38 ' for carrying the cans (not shown) into the oven in single file. This oven performs the can sterilisation stage 20 of the packaging process. From the oven 36 the sterilised cans are passed horizontally through an elongate filler 40 by which they are charged with a metered dose of the liquid product which is supplied in a cold but sterilised condition by a supply pipe 91. The filler accordingly performs stage 22 of the packaging process. An end closure sterilising oven 42 is mounted above the downstream end of the filler 40. In addition to sterilising the end closures by sterile hot air the oven serves to combine them individually with filled cans received from the filler, so as to close the cans temporarily but in an aseptic manner. The oven 42 accordingly performs the end closure sterilisation stage 24 of the packaging process; in combination with the filler it also performs the combining stage 26 of the process . Together with the liquid product supplied by supply pipe 91, the sterilising ovens 36 and 42 form the input ends of the sterile zone 54 of the apparatus. The output end 56 of this zone, which also includes the filler 40, is located upstream of a rotary seamer 48 to which the cans are moved by a scroll 211 (Fig.15) after their temporary sealing by the end closures. The seamer, which is accordingly and desirably located in a normal, non- ^sterile environment, is conventional except for its omission of the end closure application apparatus which must usually be provided in can filling lines. The seamer performs the seaming stage ' 28 of the packaging process of Fig.2. The seamer 48 is further modified by the addition of a reforming station 50 at which the raised end panel 17 (Fig.l) of the cans leaving the seamer are mechanically engaged by a reciprocating plunger (not shown) and inverted into the cans. The reforming station accordingly performs the reforming stage 30, and the internally pressurised cans 32 (Fig.2) which leave it are carried away by the conveyor 52 for subsequent dispatch and sale. Figs .4 and 5 in particular show the arrangement of the ancillary equipment by which filtered and heated air is supplied to the ovens 36 and 42, and the filler 40 is separately supplied with sterile but cold gas and, through supply pipe 91, with sterile liquid product. The ancillary equipment is generally mounted at the top of the apparatus on a support table 58 forming part of the frame 34. It has primarily separate and independent air circulation and heating units 152 and 154 for the can sterilising oven 36 and the end closure sterilising oven 42 respectively. The unit for the can sterilising oven comprises a blower 156 driven by electric motor 158, and supply and return ducts 160, 162 connecting the blower to the can sterilising oven. Likewise, the unit 154 for the end closure sterilising oven has blower 164 with motor 166, and supply and return ducts 168, 170 respectively. In each case electrical heating elements (not shown) are mounted in the supply duct and/or the return duct for heating the air flowing through the unit. The detailed arrangement of the ovens 36 and 42, the filler 40, the seamer 48 and the reforming station 50 will become apparent from the following descriptions of them individually. CAN STERILISING OVEN 36 The oven 36 by which the empty cans 10 are sterilised before filling and closing is shown in Figs.6 to 12. It is generally cylindrical, having a central rotor 60 which is mounted for rotation about a vertical axis in an anticlockwise direction (Figs.6, 8 and 9) within a cylindrical stator 62. The stator 62 has inner and outer skins 64 and 66, and a thermally insulating layer (not shown) attached to the inside of the outer skin. For access to the oven interior it is formed in two generally semi-cylindrical halves 62A, 62B which are separable on a vertical diameter. In Fig. 6 the stator halves 62A, 62B are shown individually and diagrammatically, the half 62B being shown in relation to the rotor 60 and to cans 10 moving through the oven. Fig.9A shows detail of each intersection between the stator halves 62A, 62B, and it will be seen that for each stator half the skin material is extended radially through the intersection, so as to join the inner and outer skins 64, 66 to one another. Overtoggle catches 70 attached by bolts 72 enable the stator halves to be clamped firmly but releasably together, a resilient hollow sealing strip 74 then providing a gas-tight seal between them. The general arrangement of the oven insofar as it relates to the cans 10 is apparent ' from Figs 6A and 6B, of which Fig.6A shows the ' interior of the stator half 62A which provides both an inlet port 76 and an outlet port 78 at which cans can respectively enter and leave the oven. Cans are driven to pass in single file through the oven between these ports when supported on the turns of a continuous and inwardly projecting helical track 80 which extends down the interior of the stator with a pitch between turns slightly greater than the height of the cans. As is indicated in Fig.10 which shows three cans 10 one above the other on the helical track 80, the track is provided in an integral manner by suitable deformation of the sheet material forming the inner skin 64. In radial cross-section it has the form of a V on its side and having its apex directed inwardly of the oven. Its upper flank 80A is arranged to support the cans as they move down the track, by engagement with the stand rings 15 (Fig.l) of the cans. Its lower and upper flanks 80A, 80B are inclined at approximately equal and opposite angles to the horizontal, and they are formed with gas outlet holes 81, 82 at spaced intervals along their lengths. The track pitch, whilst greater than the can height, is sufficiently small to ensure that gas issuing from the outlet holes can enter, respectively, the interiors of the cans and the recesses 14 on their underside in a forceful manner. The temperature of the gas issuing from the holes 81, 82 is typically within the range 180°C to 200°C, especially 190°C. The rotor 60 of the can sterilising oven has a support cylinder 83 which is mounted and driven for rotation as will be described. The rotor is arranged to engage the cans for driving them, with the assistance of gravity, down the helical track 80. For that purpose vertical bars 84 are attached at regular intervals around the exterior of the support cylinder. As can be seen from Fig.8, the bars 84 are L-shaped in cross-section, having one arm 85 in face-to-face contact with the support cylinder 83 and attached to it by rivets and adhesive (not shown) . The other arm 86 of each bar projects radially outwards from the rotor, the spacing of the bars being selected so that cans 10 passing through the oven on the turns of the helical track 80 can be individually received and located in the pockets which are formed between the arms 86 of adjacent bars. The stator 62 is closed to form a thermally insulating and gas-tight enclosure by transverse end structures 200 and 201 respectively at its top and bottom ends, to which rotary bearings 202, for the rotor are attached. The rotor is arranged to be driven from below the oven, by means of a vertical drive shaft 203 passing through the bearing 202. As previously mentioned, in operation of the filling line empty cans 10 are fed into the oven 36 by a horizontal inlet scroll 38 which is driven by gearing (not shown) at its upstream end. The cans enter the oven through an inlet gas lock 102 (Fig.4) which begins the sterilisation process and prevents substantially any contaminants from entering the oven past the incoming pans. During operation of the oven 36 heated air for the outlet holes 81, 82 of the track 80 is supplied from the gas circulation and heating unit 152 via the duct 160 to openings 204 (Fig.βB) formed in the inner skin 64. From there it is distributed to the outlet holes via the cavity 205 (Fig.7) between the rotor skins. Having heated and purged the cans 10 within the oven 36 the gas leaves the hollow centre of the rotor 60 at a temperature typically of 185°C, and returns to the unit 152 through the central duct 162. The arrangement of the inlet gas lock 102 can be seen from Figs. 11, HA and 11B. It is generally in the form of a hollow, generally rectangular tube forming an external blister on the stator 62. It has an inlet end plate 104 with a shaped shaped aperture 106 (Fig. HA) through which the cans are moved on the scroll 38. As can be clearly understood from Fig.llB which shows it in diagrammatic cross-section, the gas lock 102 provides an enclosure 108 for a part of the inlet scroll 38 and for the cans 10 carried by it. Within this enclosure a gas manifold having inlet and outlet gas distribution chambers 110 and 112 separated by a partition 114 extends above the cans. Holes 116 formed in the floor of the inlet distribution chamber 110 enable hot gas supplied from the gas circulation system via the inlet chamber 110 to be fed downwardly into the interior of the cans. After heating the cans and purging them of ambient, non-sterile air the gas is returned to the gas circulation system for filtering and reheating, via holes 118 formed in the floor of the outlet chamber 112. The free end of the inlet scroll 38 within the inlet gas lock 102 is open to the interior of the oven 36 via the inlet port 76. Cans carried by the scroll are therefore presented in turn to the helical track 80 and to successive pockets between bars ' 84 of the rotor 60. The scroll and rotor are synchronised and suitably dimensioned for this purpose. Guide bars (not shown) on the stator ensure a smooth transition of the cans as they move from one device to the other. After leaving the oven 36 having moved down the track 80 the sterilised cans 10 are destined to pass into the filler 40 by which they are to be charged with a sterile liquid product in a sterile but cool environment. Separation of the environments of the oven and filler is achieved by a filler gas lock 120 which is in many respects the same as the inlet gas lock 102, likewise having gas inlet holes 122 and gas outlet holes 124 supply heated gas to, and extract it from, cans 10 passing through the lock. The cans emerge from the lock through a shaped aperture 126 in an outlet and plate 128. At that time their temperature is typically within the range 150°C to 160°C. The filler gas lock 120 is associated with a scroll 130 which extends throughout the filler 40 to drive gearing (not shown) at its downstream end by which it is driven in synchronism with the rotor 60 of the can sterilisation oven. The free end of this scroll is located opposite guide bars (not shown) at the outlet port 78 of the oven, and cans which have been sterilised in the oven are picked smoothly by the flights of the scroll off the helical track 80, and leave the oven via the filler gas lock. FILLER 40 The filler 40 is as has been described and claimed in European Patent EP 0591396B1 (Agents ref: 4211EP) , Figs 1 and 2 of which, when suitably renumbered, are reproduced as Figs 13 and 13A of this specification. From those drawings it will be seen that the filler has a metering screw 87 having a helical thread 88 with thread gap 89, and mounted to rotate about a horizontal axis above cans 10 which are moved at regular intervals along and beneath it in synchronism with the screw rotation as indicated by the arrow A. The screw 87 is mounted within a containment vessel 90 to which the liquid product being filled into the cans is supplied via a pipe 91. The screw is free to undergo limited movement transversely of its rotational axis, and is biassed downwardly by spring-loaded presser pads 92 arranged to make sliding contact with the thread 88. Beneath the screw 87, and aligned with it, the containment vessel 90 is formed with an elongate slot 93 on each side of which it provides a bearing surface (not referenced) for the screw. The screw is biassed downwardly against these bearing surfaces by its own weight and by the presser pads 92, and as it rotates it distributes product 94 from the containment vessel 90 to the parts of the dispensing slot 93 which at the time in question correspond with the gap 89 between its turns. Accordingly, each can 10 passing through the filler is subjected to a continuous stream of the liquid product 94 which is first produced as the container passes beneath the upstream end of the dispensing slot 93 and which is terminated as the can passes the downstream end pf the dispensing slot. As can be seen from Fig.4 in particular, in the aseptic packaging system of the present application the filler 40 has its containment vessel 90 mounted above a closed filling chamber 132 through which the empty cans 10 are carried at a regular spacing by the scroll 130 previously mentioned. The filling chamber has its side walls formed with windows 134 through which the filling process can be viewed, and a convergent base 138 which tapers downwardly to an outlet at which any liquid product which has escaped is collected for recirculation via a pipe 140. In order to maintain sterility the interior of the filler is charged with a sterile gas (e.g. nitrogen or air) at slightly superatmospheric pressure supplied via a pipe 210. The sterile gas has a temperature which typically lies within the range 15°C to 30°C, that is to say, it is substantially at ambient temperature; likewise, the temperature of the liquid product entering the filler via the filler pipe 91 is substantially ambient, typically again between 15°C and 30°C. Being thin-walled and light-weight, the cans 10 have a low thermal mass; therefore, despite leaving the filler gas lock 120 at an elevated temperature they quickly cool and cause substantially no temperature increase of the food product which is charged into them from the filler pipe. The filled cans therefore have a substantially uniform ambient temperature. END CLOSURE STERILISING OVEN 42 The end closure sterilising oven 42 is shown iiagrammatically in Fig.14. It has a rotor 140 driven from below to rotate about a vertical axis, in an anticlockwise direction as shown, within a generally cylindrical stator 141. In a corresponding manner to the rotor 60 of the can sterilising oven 36, the rotor 140 has regularly spaced vertical L-section bars 142 attached to its exterior surface. In combination with the adjacent interior surface. In combination with the adjacent interior surface of the stator 141 the radially projecting arms 144 of these bars form pockets in which vertical columns of the end closures 11 can be formed and supported from beneath as they move around with the rotor. The columns of end closures within the oven 42 are created from a supply of the end closures fed one-at-a- time into the stator 141 by a star wheel 146 which is itself supplied from an end closure feed unit 148. The oven 42 forms part of the sterile zone of the aseptic packaging system, and a gas Jock (not shown) is therefore provided for the star wheel 146 to prevent any substantial gas or contaminant entry through that route. Air heated to a temperature typically within the range 180°C to 200°C, especially 190°C, is supplied to the oven 36 by pipe 168 fed from heater/blower unit 154, and is extracted from the ' oven via further pipe 170 aligned with its central axis; see also Figs. 4 and 5. The average temperature in the interior of the oven accordingly is typically about 185°C. In addition to sterilising the end closures 11 the oven 42 also serves, by virtue of rotation of the rotor 140 in the appropriate direction and speed, to place the sterile closures on the sterile and product-filled cans ^LO arriving from the filler 40. For that purpose the cans are guided to enter the oven beneath a rail 150 which is supported by the stator 141 and serves to support the columns of end closures 11 over part of the rotor 140 periphery. The rail is located so as to progressively release the bottom end closures 11 of successive columns on the rotor, so that each can 10 in turn has an end closure placed on it with the seaming flanges 12, 13 of the end closure and the can in engagement. A further rail (not shown) on the oven then engages the end closure from above, and so applies downward pressure by which a temporary aseptic seal is formed between the seaming flanges. In this condition the closed can can safely leave the sterile environment for subsequent operation of the seamer 48 and reformer 50. The temperature of the end closure when it first makes contact with the can beneath it should be above 80°C, typically 100°C to 120°C, so that the lining compound on the underside of the end closure remains tacky. However, because in part, of its separation from the food product, the end closure does not cause any substantial temperature increase of the latter within the can before it cools. The closed can therefore leaves the sterile environment substantially at ambient temperature but with a slightly positive superatmospheric pressure derived from the pressure within the filler 40.

Claims: CLAIMS : 1. A process for aseptically packaging a liquid food product substantially at ambient temperature in metal containers each comprising a body (10) and an end closure (11), the body having a thin side wall (16) liable to panelling, the process being characterised by the following operations :- (a) passing the empty container bodies (10) through a heated enclosure (36) to sterilise them and any gas within them; (b) passing the end closures (11) through a further heated enclosure (42) to sterilise them; (c) moving the sterilised container bodies to a product filler (40) at which a predetermined dose of the said liquid food product is charged into them individually substantially at ambient temperature; (d) placing the sterilised end closures individually on the product-charged container bodies so as to form closed packages having a temporary aseptic seal; steps (a) to (d) above being carried out within a continuously sterile environment; (e) removing the closed packages from the sterile environment, and, whilst so removed, (f) uniting superimposed marginal edges of the end closures and container bodies so as to render the closed packages hermetic; and subsequently (g) reforming the hermetic packages to generate a positive pressure therein. 2. A process in accordance with Claim 1, characterised in that operation (g) is achieved by reforming central panels (17) of the end closures. 3. A process in accordance with Claim 2, characterised in that the container bodies (10) are made by the DWI process, having an integrally formed base (14, 15) and one open end, the open end is closed by a respective end closure (11) to form a said hermetic package, and the reforming step (g) comprises reforming a projecting central panel (17) of the end closure to an original position inwardly of the hermetic package. 4. A process according to any preceding claim, characterised in that the reforming step (g) generates a superatmospheric pressure of between 0.5 and 2.0 bar within the hermetic packages. 5. A process in accordance with any preceding claim, wherein the can bodies (10) are manufactured from tinplate or aluminium, having the minimum thickness of 'their side wall (16) within the range 0.068mm to 0.084mm or 0.096mm to 0.114mm respectively. p . A process according to any preceding claim, characterised in that in order to heat their respective enclosures steps (a) and (b) are carried out using hot air which is caused to enter the enclosure at a temperature of between 180°C and 200°C. 7. A process according to any preceding claim, characterised in that step (c) is carried out within an enclosure (90) supplied with a sterile gas at a slightly superatmospheric pressure. 8. An apparatus for aseptically packaging a liquid food product substantially at ambient temperature in metal containers each comprising a body (10) and an end closure (11) having a central panel (17), the body having a thin side wall (16) liable to panelling, the apparatus being characterised by the following components : - (a) a first sterilising oven (36) supplied with a heated gas and adapted for sterilising the container bodies and any gas within them; (b) a second sterilising oven (42) supplied with a heated gas and adapted for sterilising the end closures; (c) a product filler (40) adapted for charging a predetermined dose of the said liquid food product substantially at ambient temperature into the sterilised container bodies; (d) a combiner (150) adapted for placing the sterilised end closures individually on the sterilised and product-charged container bodies so as to form therewith closed packages having a temporary aseptic seal; (e) a sealer (48) adapted for uniting superimposed jnarginal edges of the end closures and container bodies to render the closed packages hermetic; (f) a reformer (50) adapted for reforming the central panels of the end closures of the hermetically closed packages to generate a positive pressure therein; (g) drive means arranged to move the container bodies and end closures substantially without interruption through components (a) to (f) as appropriate; and (h) a sterile environment for the container bodies and end closures between their entry to the appropriate sterilising oven and their exit together from the combiner, the sterile environment not extending to the sealer or the reformer. 9. An apparatus in accordance with Claim 8, characterised in that the sterilising ovens (36, 42) , the product filler (40), the combiner (150), the sealer (48) and the reformer (50) are serially arranged generally in horizontal alignment. 10. An apparatus in accordance with Claim 9, characterised in that in passing between the combiner (150) and the sealer (48) the closed packages with temporary aseptic seal move through a right angle. 11. A gas oven for articles, characterised in that it has a generally cylindrical rotor drivable to rotate about a vertical axis, a stator surrounding the rotor end defining therewith an annular gap within which articles to be heated may pass, an inwardly projecting helical track formed on the inside of the stator and capable of supporting the articles as they move within the gap between an upper, entry port and a lower, exit port, and outward projections on the rotor by which the articles are moved with the rotor circumferentially of the oven and, by gravity, axially thereof.

Inventors: PERIGO JOHN ALFRED, PRICE FREDERICK, PERIGO, JOHN, ALFRED, PRICE, FREDERICK
Applicants: CROWN CORK & SEAL TECH CORP, METAL BOX PLC, PERIGO JOHN ALFRED, PRICE FREDERICK, CARNAUDMETALBOX PLC, CROWN CORK & SEAL TECHNOLOGIES CORPORATION, PERIGO, JOHN, ALFRED, PRICE, FREDERICK
Application year: 1998
Main classification: B65B55
IPC codes: B65B55