CONTAINER FORMING APPARATUS

Abstract: An apparatus (10) is provided by which to form containers (26) such as are used in packaging foodstuffs. The apparatus (10) comprises counter-rotating strings of container forming assemblies (15, 16) passed through a container forming station (14). The assemblies include moulds (21, 24) by which to form the containers in a sheet (11) which is fed thereto. Container formation can be by blowing the sheet into a mould (21). The sheet might be preformed by motion of a plug (24) prior to blowing. The moulding elements are operatively mounted successively to pivotally joined support means (81, 85). The separate strings of respective container forming elements are each powered for movement in a closed loop past the container forming station (14), travelling in concert so that the sheet (11) is deformed to form a container (26) therein before exiting.

Description: TITLE Container Forming Apparatus FIELD OF THE INVENTION THIS INVENTION relates to apparatus by which to produce items of packaging of the plastic container type, produced by a moulding process from flat sheet stock. BACKGROUND TO THE INVENTION It is known to produce containers or container-like packages for foodstuffs and a range of other supermarket and general retail products. Such containers or packages are often produced by moulding the containers from flat sheet stock such as plastic sheet which is able to be heat formed into a desirable shape in suitable moulds. The apparatus by which such containers are formed achieves a result by placing a sheet of raw stock material between opposed die plates or mould bodies, or against a die plate or mould body and then bringing about the formation of a container or package, usually as an array of containers or packages, the array being formed simultaneously in the sheet by pressing or vacuum forming. When a sheet of these containers is formed, the so formed sheet is unloaded from the moulding apparatus and a fresh unformed sheet is loaded therein and the forming process is repeated. The formed sheet may then have its containers filled with product, to be held therein by a closure sheet or capping means which is usually applied thereover. The array can be divided up into individual containers or packages, or small groups of containers or packages either before or after filling. The division of the formed sheet of containers arrayed therein most usually occurs prior to the filling process. Whichever way the process is performed, a substantial mould or die is required if enough containers are to be formed in a single operation, sufficient to gain a reasonable production rate. The above apparatus reciprocatively moves die plates to and from a moulding position. This involves low production rates. British specification, GB 2255524 describes an apparatus which conveys palettes carrying deformable sheet material past forming stations, stepping them from one to another with a reciprocated mould forming the sheet. Again the reciprocating mould slows production rates. Japanese specification, JP 3288635 describes an apparatus with a plurality of counter rotated moulds, the plurality of moulds comprised of opposed assemblies moved in synchrony through a moulding station. A continuous roll of stock sheet material is fed into the nip between the conveyors to be continuously formed as it moves through the container forming station, with containers and waste exiting at the end. In this apparatus the container is formed by mechanical means and the requisite motions of the respective assemblies is effected by combined action of three cams. This is an overly complex piece of apparatus. In this apparatus the mould assemblies are stood off the links of a drive chain which is a poor means of moving the bulky assemblies. OBJECT OF THE INVENTION It is an object of the present invention to provide an apparatus for the production of containers, packages, or the like, produced from deformable stock sheet material which apparatus achieves increased production rates by more efficient means. Other objects and various advantages will hereinafter become apparent. NATURE OF THE INVENTION The invention achieves its object by providing an apparatus for forming containers such as are used in packaging foodstuffs and other commodities, said apparatus comprising: a container forming station whereat containers are formed; and mould means by which to form a container in a sheet which is fed to the mould means, at the container forming station; characterised in that: the mould means are established by operatively inter-related container forming elements, respective forming elements of each mould means mounted successively in separate strings of said respective forming elements; said separate strings of respective container forming elements are each powered for movement in a closed loop past the container forming station whereat opposed pairs of container forming elements come together; said separate strings travelling in concert along a container forming zone at the container forming station whereat the sheet is deformed to form a container therein before exiting therefrom. In an apparatus of the above kind, continuous sheet material may be fed to the apparatus, off roll stock, fed through a heater to soften the sheet and then into a container forming zone between the container forming elements. The dwell time between the container forming elements will be what suits the particular plastic being used, the shape of the container to be formed, and that allows cooling sufficient to retain the shape. The dwell time is that which is necessary before release if the plastic is to remain in its finished form. The length of the container forming zone can be lengthened so as to hold a given dwell time when higher speeds are adopted to gain greater rates of production. The sheet exiting from the container forming station is preferably fed to other packaging apparatus at which , depending on the scheme of things, filling, covering, and severing of containers, or groups thereof, occur in whatever order suits. The container forming apparatus can comprise forming elements, dies or mould parts, mounted to separate, spaced, synchronised strings of assemblies connected in the form of chains, belts conveyors and the like, with, preferably peripheral clamping of the sheet being formed, clamping being effected by the forming elements acting against the stock sheet, preferably to seal the sheet to be formed therebetween. Forming can be by action of a fluid under pressure such as by use of compressed air blowing or a mix thereof with mechanical die or mould motions. With mould elements mounted to complementary and synchronised strings, belts, chained links or conveyor, the forming element pairs are able to be moved to continuously and successively come together to engage with a sheet or ribbon of stock material fed therebetween. The forming element pairs can be mounted to travel the length of a container formation zone or station at a suitable working spacing. At the end of the zone, the forming elements part to release the formed sheet therefrom at the end of the zone and then loop back to re-engage in the container forming process. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to a preferred embodiment as shown in the accompanying drawings in which: FIG. 1 is a schematic showing elements of an apparatus in accordance with the invention; FIG. 2 is a detail at the container forming zone of the apparatus of FIG. 1; FIG. 3 is a detail of another form of an apparatus in accordance with the invention; and FIGS. 4 to 6 are detailed views at a container forming station in an apparatus in accordance with the invention. PREFERRED EMBODIMENT In FIG. 1 a container forming apparatus 10 is preferably fed a continuous sheet of deformable plastic or like type stock material 11 off a roll 12 (although it will be appreciated that the sheet material which is supplied to the apparatus might be in stock lengths fed from a store of individual sheets) . The raw sheet stock is fed to the apparatus ideally through a means to convert it to a deformable state such as by being made to pass through a heater tunnel 13 whereat the plastic material is raised to a deformable temperature. The sheet material is then preferably made to pass into a nip 14 between two continuous working strings, chains, belts, conveyors or the like, numbered 15 and 16, which are passed around suitable, spaced, support means, ideally sprocket pairs 17, 18 and 19, 20 respectively. Engagement of the sheet by the respective strings provides a means by which sheet material may be drawn off the roll 12 (although separate or additional means might be provided to assist the flow of sheet material through the apparatus. Forming elements, dies or female mould pieces 21 can be mounted, in this embodiment, one to each link or plate of chain, belt or conveyor 16. Each female mould piece 21 can have upstanding end walls 22 and 23 forming a container shape between side walls (not shown) . The hollow of the female mould piece provides the mould surface against which the deformable or softened plastic or like stock sheet is pushed or pressed to shape or mould it. At each corresponding link on complementary chain or belt 15 there can be a respective forming element, die or mould piece 24 which can be mounted in a complementary support therefor such as the hollow of a peripheral enclosing wall, cylinder or housing whose end walls 25 and 26 are seen in the section of FIG. 1. The male mould element, die or plug is the means by which, in this embodiment, the sheet is partly pushed into the corresponding female mould. The operation of the mould elements is described below in greater detail with reference to FIG. 2. Following formation of the containers in the sheet material, the now formed sheet 26 exits and it can be passed, in this embodiment, around a turnstile 27 and ideally into a punch or knife unit 28. Waste can be fed onto a suitable web roller as will be clear to those skilled in the art. Severed containers can be caught in an automatic counter and stacking apparatus 29. The nature of this piece of apparatus is well known to those skilled in the art. As it does not form part of the preset invention no more detail is given of it. An apparatus of the above kind can have a plurality of container forming chains, belts or conveyors of the above described kind, arrayed in parallel to each other and side by side across the width of a sheet of raw container forming material to produce a plurality of lines of side by side containers arrayed across the width of the stock sheet of suitable plastic or similar material. The shape of successive forming elements can be varied to vary the shape of successive containers if desired. In FIG. 2 is seen, in greater detail, the action at the container forming zone or station which is established between the two strings, chains, belts or conveyors 15 and 16 along a straight length thereof. The peripheral enclosures, rims or walls of the respective male and female container forming elements, mould parts or dies, seen in section in FIG. 2, with opposed wall elements 22 and 25, and, 23 and 26 respectively, are aligned by their respective chain links which may be plate-like bodies, or other additional or different means, to bring them together to permit male mould part, die or plug 24 to advance into female mould part or container forming element 21. Male mould part 24 is preferably mounted for movement in its peripheral wall, housing or enclosing cylinder, via a pivot 29 on a support link 30, joined at pivot 31 to lever actuator arm 32 turning on pivot 33 when its roller 34 mounts the cam 35 after engaging with cam step 36 (it will be appreciated that there are a variety of mechanisms by which the requisite action can be bought about) . The male mould part or plug 24 is ideally aligned by a depending skirt 37, 38 sliding within peripheral walls 25, 26 of its enclosing cylinder or wall. It advances, in this embodiment, to the point shown in the middle of the figure to begin the distension of the plastic sheet (not shown) which is ideally clamped between the mould pairs to form a seal therewith to enable further moulding by a blow moulding process. A fluid supplied under pressure, such as a compressed gas such as air can be blown through ports (as will be described below) preferably in peripheral wall 25, 26 of the cylinder or a base thereto, to create a gaseous pressure to push the softened or deformable plastic sheet against the female mould part or container forming element 21 to give the container its final shape (the female mould part will be provided with exhaust ports therein - not shown herein as they are features well known to those in the art - to enable release of air which would be otherwise trapped therein to defeat the action of the compressed gas). The two mould parts or container forming elements preferably engage with the plastic sheet around their opposed and aligned adjoining peripheral walls not only to establish a seal for blow moulding but also to provide the traction force which draws the sheet material off its roll, when a roll supply is utilised. The two mould parts can engage the sheet and form a seal therewith. To this end sealing rings 39, 40 can be used to engage the sheet therebetween to form the aforesaid seal. Compressed air can be operative to push the plastic around lip 41 to form a desired shape or profile at the container opening. The male die part or plug 24 is biassed by means such as springs (not shown) to the retracted position seen at the left and right hand ends of FIG. 2, to return to the fully withdrawn position, shown generally at 42 when cam follower, or roller 34, passes over the shoulder 43 in the cam surface so as to disengage therefrom. As the apparatus of FIG. 2 is sped up, the plastic may need to be retained for longer times between the mould pieces so as to complete the moulding process. This is readily achieved by increasing the length of the cam 35 and the length of the straight section of adjoined chains. The male die part or plug 24 can be used to start the extrusion in preferred embodiments. Compressed air then finishes the forming process, pushing the plastic against the cold female mould or die part where the plastic hardens. Compressed air might be used to provide all the forming needed in the container. The female mould parts on chain, belt or conveyor 16, may be cooled by a cooling means before their return to the container forming zone so as to remove therefrom what heat is gained by contact with the heated sheet (to maintain the mould parts effectiveness when passing the forming station, reducing the time needed to complete the process and the length of the forming station) . In FIG. 1, drive shaft 44 can power the respective chains, belts or conveyors, preferably via worm drives 45 and 46, turning chain support means, in this case sprockets 17 and 19 respectively. The sprockets can be movably mounted on support rails such as 47 with each sprocket mounted on a sliding block such as block 48 at sprocket 18. The sliding block 48 can be moved by a screw 49. This permits control over the nip between the chains and adjustment for various sheet thicknesses and in the case of wear. In the above described apparatus the male die part or plug can be separately heated to hold the plastic sheet at a deformable temperature over the time of contact. The female mould can be cooled for the opposite purpose of returning the material to a hardened form as quickly as possible after contact therewith, when the shaping process will be complete. It will be clear to the man skilled in the art that the male mould may incorporate a die or plug which complements the female part to squeeze the sheet thereagainst but this can introduce problems with temperature control of the parts. The male mould may incorporate the plug illustrated and compressed air can be used to finish the job. Or, the male mould can comprise a housing or cylinder only and compressed air only can be used as the only means by which to distend the sheet, but this involves the use of greater volumes of compressed air. In the above described apparatus, the chains, belts or conveyors may comprise die support plates which may be joined by pivot means such as pins, in a chain like structure. However, the man skilled in the art will realise that the 'chain' can comprise a series of links in a variety of forms, pivoted together, as with a caterpillar track. Essentially the 'chain' is a means by which respective pieces of container forming apparatus are brought together over the length of a container formation zone. In FIG. 3 is seen two chains or conveyors 50, 51, the second conveyor 51 being longer to create a zone 52 whereat the formed material can be extracted from the moulds on conveyor 51 before they reach the turnaround point about sprocket 54 whereat the spreading of the moulds at 53 would tear the formed material if the containers formed therein were still in place. Removing the containers from the moulds at the proper time is easily arranged by providing a guide which feeds the material outwardly at zone 52 as will be clear to the man in the art. In FIG 3, the two chains or conveyors 50 and 51 come together between pressure plates 55 and 56 which engage with the pivoted mould support plates of the conveyors via intervening runners or guides, 57 and 58, respectively. The runners or guides 57 and 58 may be a pair of elongate nylon blocks engaging the conveyor at opposite edges, a series of roller bearings, etc. , anything which permits pressure to be applied with suitably reduced friction therebetween. The pressure plates 55 and 56 can be mounted at each end to a suitable support means such as shafts 59 and 60 (another complementary pair being provided on the other side) with nuts or like means such as 61 and 62 threaded thereto by which to set the position of the pressure plates. A pair of plates and associated guides can be applied to each of a plurality of parallel strings of moulds if a row of moulded containers is formed across the width of a sheet material fed thereto. In FIG. 3, the two conveyors may be powered by applying motive power to the shafts 63 and 64. Any form of synchronised, counter-rotating means might be applied by which to achieve the requisite conveyor motions. The shafts might be powered by belt drives, gear trains, etc. In FIG. 4 is seen a cross-sectional detail of a section of an apparatus at the container forming station between the pressure plates 105 and 106 which engage the two conveyors 81, 82 via spaced runners or guides with one of each pair being seen in the figure, 108 and 110 engaging conveyors 81 and 82, respectively. Between the spaced guides or runners engaging conveyor 82 is a cam block 115. The conveyors are powered to move from left to right in this figure according to the arrow 70. In the motion over the cam block 115, the push rods 71 to 73 are moved axially by the block 115 to move their respective plugs into the adjoining mould. The push rods run on a roller or other suitable means to reduce friction. The rod 71 is joined to plug 75 which is biassed by a means such as the springs 76 and 77 to its retracted position. The plug 75 may have a face plate or body of heat retentive, or heat insulation material, 78, attached thereto. This may be a material such as bakelite, felt, etc. Action of the plug 75 is to advance into mould 79 to preform or stretch the sheet material prior to finally blowing it into shape. In FIG. 5, there is seen a sectional view of a portion of the apparatus between pressure plates 106 and 105, and runners or guides 109 and 107. Between the runners or guides to conveyor 88, beside the cam block (not shown) is an air valve indicated generally at 116. The air valve 116 is formed with a fixed block 89 or housing on the pressure plate 106 with a valve body 90 therein which is biassed by suitable means, such as springs 91 and 92 against the conveyor 88 to form a slide valve therewith whereby air fed under pressure through passage 93 is communicated via passage 94 in the valve body 90, and via passages 99 and 95 to chamber 96 behind sheet material (not shown) to be blown against the respective mould. The apparatus of FIG. 5 is advancing from right to left as indicated by arrow 97. In this motion, the lower port of passage 99 in support plate 98 of conveyor 88 passes over the top surface 100 of the slide valve 116. When passage 99 is aligned with chamber 102, pressurised air is fed to chamber 96. When the port to passage 99 passes onto the top surface 100, it is blocked and pressure is held in chamber 96 until passage 99 passes beyond the slide valve. A chamber 101 is provided with a surface area in excess of that of 102 so that the pressure at 102 opposing the biassing means. springs 91 and 92, is itself opposed to cancel and/or overwhelm it, ensuring good contact between surface 100 and plate 98. In FIG. 6 is seen a transverse section through the apparatus at the forming zone, between pressure plates 105, 106 with runners or guides 107 to 110. The pressure plates are mounted to support rods 111 and 112 and held in place thereon by nuts such as 113 and 114. Between guides 109 and 110 is cam block 115 and slide valve 116 passing air via port 117 to the chamber 96 behind the sheet material (not shown) in the respective female mould. In FIG. 4, the plug 83 slides in guide walls 84 mounted on conveyor plate 85 and a seal 65 can be formed therebetween. The plug 83 and the mould 86 may come together with a rim 66 on the guide wall 84 spaced from a rim 67 on mould 86 by a gap 68. A sheet of material between the plug 83 and mould 86 can be formed by this arrangement with a lip, formed in the material over the rim 67 on mould 86. The seal 65 operates in conjunction with the plug 83 to create a chamber 87 behind the sheet material which is small and requires only a low volume of pressurised air to effect the forming process.

Claims: CLAIMS: 1. An apparatus for forming containers such as are used in packaging foodstuffs and other commodities, said apparatus comprising: a container forming station whereat containers are formed; and mould means by which to form a container in a sheet which is fed to the mould means, at the container forming station; characterised in that: the mould means are established by operatively inter-related container forming elements, respective forming elements of each mould means mounted successively in separate strings of said respective forming elements; said separate strings of respective container forming elements are each powered for movement in a closed loop past the container forming station whereat opposed pairs of container forming elements come together; said separate strings travelling in concert along a container forming zone at the container forming station whereat the sheet is deformed to form a container therein before exiting therefrom. 2. An apparatus as claimed in Claim 1 wherein each of said mould means comprises a pair of opposed container forming elements, bought together at said container forming station, clamping the sheet material therebetween and whereat compressed air is utilised to press sheet material into a first one of the container forming elements. 3. An apparatus as claimed in claim 2 wherein the other of the pair of container forming elements includes a movable plug to preform the sheet ready for final pressing by compressed air. 4. An apparatus as claimed in Claim 3 wherein the movable plug includes a preheated former at the face which engages with the sheet, made in a heat retaining material. 5. An apparatus as claimed in Claim 1 wherein a sheet feeding means supports a roll of sheet material which is continuously drawn through the apparatus by engagement thereof by the mould means. 6. An apparatus as claimed in Claim 5 wherein the sheet material is drawn off the roll and it is passed through a heat tunnel to ready it for moulding, prior to its arrival at the container forming station. 7. An apparatus as claimed in Claim 6 wherein the sheet material leaving the container forming station is fed to a severing station where individual containers are cut from the sheet carrying formed containers therein. 8. An apparatus as claimed in Claim 2 wherein the other of the pair of forming elements is mounted to a support means which slides, at the container forming station, over a slide valve with at least one gallery therein from which compressed air feeds to a passage in the support means and thereby to the mould. 9. An apparatus as claimed in Claim 1 wherein both strings are a series of support means for supporting the container forming elements, which support means are hingedly connected together on pivot pins and which pass around sprocket wheels. 10. An apparatus as claimed in Claim 9 wherein the reaches of the strings extended between the sprockets run in channels to minimise flapping in the strings. 11. An apparatus as claimed in Claim 3 wherein the movable plug is mounted in operative association with a motion conversion means which is actioned at the container forming station by movement of a cam follower over a cam so as to push the movable plug into the first of the container forming elements. 12. An apparatus as claimed in Claim 4 wherein a heater is disposed along a reach of the string, ahead of the container forming station, to heat the plugs of the container forming elements. 13. An apparatus as claimed in Claim 8 wherein compressed air supplied to the slide valve is switched to feed thereto only when the support means port is passing thereby. 14. An apparatus as claimed in Claim 9 wherein the support means are pivoted together on pivot pins which engage with the sprocket wheels which drive the plates through the forming station. 15. A method of forming containers. AMENDED CLAIMS [received by the International Bureau on 07 March 1996 (07.03.96); original claim 15 cancelled; original claims 1-5, 8, 10,and 11 amended; remaining claims unchanged (3 pages)] 1. An apparatus for forming containers such as are used in packaging foodstuffs and other commodities, said apparatus comprisingi 5 a container forming station whereat containers are formed; and mould means by which to form & container in a sheet which is fed to the mould means, at the container forming station; 10 said mould means are established by operatively inter-related pairs of male and female container forming elements, respective male and female container forming elements of each mould means mounted successively in two separate strings of said respective male and female 15 forming elements} said separate strings of respective container forming elements are each powered for movement in a closed loop past the container forming station whereat opposed pairs of container forming elements corns together; and 20 said separate strings are constrained to travel in concert along a container forming zone at the container forming station whereat the sheet is deformed to form a container therein before exiting tserefrom; characterised in that 25 said container forming zone is established, along a strai ht line, and at an exit end to the container forming station, the string comprising the female container forming elements continues with movement: along said straight line past a point whereat the other string 30 leaves it. 2. An apparatus as claimed in Claim l wherein said mould ^"t-~-- clamp the sheet material therebetween and compressed air is utilised to press sheet material, into successive female container forming elements. 3. An apparatus as claimed in claim 2 wherein the respective male container forming elements include a movable plug to preform the sheet ready for final pressing by compressed air. 4. An apparatus as claimed in Claim 3 wherein the movable plug includes a preheated former at the face which engages with the sheet which is made in a heat retaining material. 5. An apparatus as claimed in Claim 1 wherein a sheet feeding means supports a roll of sheet material which is continuously drawn along a vertically oriented line through the container forming station by engagement thereof by the mould means. 6. An apparatus as claimed in Claim 5 wherein the sheet material is drawn off the roll and it is passed through a heat tunnel to ready it for moulding, prior to its arrival at the container forming station. 7. An apparatus as claimed in Claim 6 wherein the sheet material leaving the container forming station is fed to a severing station where individual containers are cut from the -sheet carrying formed containers therein. 8. An apparatus as claimed in Claim 2 wherein the respective male container forming elements are mounted to a support means which slides, at the container forming station, over a slide valve with at least one gallery therein from which compressed air feeds to a passage in the support means and thereby to the mould. 9. An apparatus as claimed in Claim 1 wherein both strings comprise a series of support means for supporting the container forming elements, which support means are hingedly connected together on pivot pins and which pass around sprocket wheels. 10. An apparatus as claimed in Claim 9 wherein at least the reaches of the strings extended between the sprockets through the container forming station run in channels to assist clamping of the sheets and to minimise flapping in the strings. 11. An apparatus as claimed in Claim 3 wherein the movable plug is mounted in operative association with a motion conversion means which is actionβd at the container forming station by movement of a cam follower over a cam so as to push the movable plug into the respective female container forming element. 12. An apparatus as claimed in Claim 4 wherein a heater is disposed along a reach of the string, ahead of the container forming station, to heat the plugs of the container forming elements. 13. An apparatus as claimed in Claim 8 wherein compressed air supplied to the slide valve is switched to feed thereto only when the support means port is passing thereby. 14. An apparatus as claimed in Claim 9 wherein the support means are pivoted together on pivot pins which engage with the sprocket wheels which drive the plates through the forming station.- STATEMENT UNDER ARTICLE 19 Claim 1 is amended by movement of features to the preamble of the claim with an additional feature to distinguish from the prior art. The exit structure to the container forming station is critical to achieving production of deep draw containers which must release from their moulds before meeting a curve where the increased spacing between the moulds around the curve would otherwise tear the intervening sheet. Consequential amendments exist in claims 2, 3 8 and 11. Claim 15 is deleted being unsearchable being included originally as a result of clerical error. Claim 5 is amended with an additional limiting feature. The remaining amended claims are amended to effect clarification.

Inventors: TUSKES ZOLTAN, TUSKES, ZOLTAN
Applicants: PRATHER DIANNE, TUSKES ZOLTAN, PRATHER, DIANNE, TUSKES, ZOLTAN
Application year: 1995
Main classification: B29C43
IPC codes: B29C49, B29C51