NZ305862A

NZ305862A - A process and apparatus for manufacturing a metal can with a foil closure membrane

Info

Publication number: NZ305862A
Application number: NZ305862A
Authority: NZ
Inventors: Werner Grabher
Original assignee: Werner Grabher
Priority date: 1995-04-02
Filing date: 1996-03-30
Publication date: 1999-10-28
Also published as: ES2127634T3; JPH11509810A; DK0819086T3; CA2217311C; KR100526838B1; CN1185138A; ATE174859T1; CA2217311A1; EP0819086A1; AU694023B2; EP0819086B1; ZA962628B; DE59601055D1; JP3689115B2; KR20050038655A; BR9604869A; GR3029457T3; CN1063401C; AU5398796A; WO1996031406A1

Abstract

The tin can is closed by a paper, plastic or metal-foil membrane (2) on at least one end face in such a way that the outer side of the foil edge region (5) raised in the direction of the can's axis (A) is joined to the essentially cylindrical inner surface of the wall of the can (1) to form a seal, without covering the wall edge of the can. The membrane foil (2) with the raised foil edge region (5) is introduced into the can and forced against the inner wall of the can (1) by a die (8) with an expandable periphery (17). Heat is then applied to create a sealing join between the raised foil edge region (5) and the inner wall of the can (1) without any external pressure-absorbing device.

Description

<div class="application article clearfix" id="description"> New Zealand No 305862 International No PCT/EP96/01410 TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates 02 04 1995, Complete Specification Filed 30 03 1996 Classification (6) B65D51/20, B65B7/28 Publication date 28 October 1999 Journal No 1445 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention Tin can with a foil closure membrane, and a process, device and foil for manufacturing the can Name, address and nationality of applicant(s) as in international application form WERNER GRABHER, Oberwingertstrasse 8, CH-9436 Balgach, Switzerland 1 Process and apparatus for the production of] having a foil closure diaphragm, and sheet m having a diaphragm foil closure N 2 PATENT OFFICE a a , ^4 SFP 1997 fetal can R'iCci v'lD The invention relates to a process and an appaiatus foi the production of a can according to the piecnaractenzmg clause of Claim 1 or of Claims 7 and 8, as well as to a sheet metal can having a diaphragm foil closure . Metal cans have to date been closed essentially either by flanging together the cut can edge with a sheet metal lid (for example according to WO 83/02577 or US-A-3, 952,677) or by providing with a sheet metal ring provided with a foil (according to AT-A-368.919), or the inner surface of the can wall (1) had to be conically shaped (for example according to DE-U-94 1 4 440) , at least m the region of the raised foil edge (5), which reguired more complicated can production and high tolerances to enable the same position of the_diaphragm disc relative to the can edge always to be achieved on introduction of the punch. On the other hand, discs with a raised edge which do not overlap the cut edge of the can have been disclosed for plastic cans (for example, DE-A1-33 05 144 or CH-A-629 984), but these were always relatively stable lid parts for the bottom of cans capable of bearing a pressure load or those having a relatively soft wall (for example according to US-A-4,599,123), which required an external pressure absorption apparatus for the sealing process. Such discs have also been proposed for metal cans (CH-A5-659633), however, they can only be fixed by means of a heat conductive (metal) lid, through which the heat for sealing the diaphragm has to be applied and which remains m the can. WO-A-84/04507 has already described an apparatus m which the can is closed by a diaphragm foil which is t Tl ;; n j 1 ") r> e\ '' pressed against the can inner wall by means of a rubber ring mechanically expanded oufwards and is connected to said wall by means of a heat-seal coat. However, this requires a very complicated design of the rubber ring ana of the welding tool brought to the can wall from the outside. It is the object of the invention to provide a process for tne production of a can, for e> ample one comprising tin plate or aluminium sheet, having a simple and especially cheap closure This is achieved for the first time by the feature stated m the characterizing clause of Claim 1 Preferred embodiments of the mstart invention are described m the cnaracterizmg parts of Claims 2 and 3. As disclosed m another context, the closure consists of only one diaphragm foil, optionally of plastic and/or paper (in particular laminated with thin aluminium foil), but preferably a metcl foil, m particular of aluminium, everything also being denoted below merely as foil for the sake of simplicity, and optionally permits the can opening to be revealed m a manner known per se with tne aid of pull tabs The diaphragm disc edge raised _n tne direction of the can axis does not overlap the -preferably flanged - can edge, thus facilitates pulling off and therefore leaves the can edge with its robust outside or standing surface. The diaphragm foil is preferably not more than 0 2 mm, m particular not more than 0 1 mm, thick, consists, for example, of a 50 (Jin aluminium foil with a 20 jum heat-seal coating on the inner surface and a 10-20 jjm antifriction coating on the outer surface and is therefore suitable for the closure of the subsequent withdrawal opening. Depending on the contents or on a lid used, however, the can bottom, too, may be produced according to the invention, if required. Also preferred is the use of embossed foils beqe-a-se-^.tJhev can pEL^criM^P RmfYomcT, I 13 AU3 1999 L-RECEIVED 3 do . be more easily fitted closely to cans with changing tolerance and also give better stability. In general, at is preferable if the diaphragm foil - at least m the region intended for connection to the inner surface of the can - is coated witn a heat-seal coating. In principle, however, the inner surface of the can may also be provided with a primer or a heat-sealable coat m the region mentioned - as m the cas > of the inner surface of combination cans (for example, laminated with aluminium foil), otherwise, tight connection frequently requires the use of special - m particular multicomponent - adhesives or heat-seal coatings. In ar>y case, bright or coated cans can thus also be closed with a tight seal. In an inconvenient procedure employed to date, it was necessary to exert pressure externally against a fixed, stable punch applied m the interior of the (relatively soft) cardboard can by bringing together annular segments or bringing together two conical surfaces. This is no longer the case m the process according to the invention The much better and less inconvenient method of applying pressure from the inside is not possible m the case of conventional, soft cans since the diameter tolerances of the can were too large for exact external holding directed against the internal pressure, or it was necessary for the can inner edge and punch to have a conical shape. In the case of the car according to the invention, external nolding is no longer required at all; loose centring is sufficient. The apparatus according to Claim 7 is particularly suitable for carrying out the process according to the invention, preferably when at least one of the features of Claims 8 to 10 is realized Of course, the diaphragm foils used for closing tne cans according to the invention are axgeaient ly produced beforenand from material according/ toL^alV^ OF NZ I 3 Al'S B93 -RECEIVED (\ rj Claims 4 to 6 and are then applied to the corresponding can opening with the aid of the process according to the invention, so that they can also be easily introduced into cans having different tolerances and in some cases are m the desired position simply owing to the conical foil edge region. It is true - as mentioned - that Swiss Patent 659,633 has disclosed a sheet metal can whose end face is closed oy means of a raised diaphragm. However, an essential feature of the invention there is a heat-conducting lid which remains m the can until the latter is opened by the end user (Fig 9) , whereupon however the diaphragm is also removed and the can no longer complies with the claim. However, the can according to the present invention is closed only at one end by means of a diaphragm foil and is free from a neat-conduct.ng lid tnere (as is usual in the industry, and it is thus suitable at the opposite end for filling, i.e an intermediate product, whereas the comparable intermediate product according to Swiss Patent 695,633 has a heat-conducting lid wmcn makes the can more expensive and more complicated) Claim 13 protects the can according to the invention insofar as it differs, m a manner which cannot be uniquely defined m design terms, from that disclosed m Fig. 9 of Swiss Patent 695,633. There, m fact, the inner diameter of the heat-conducting lid must correspond exactly to the can inner diameter minus twice the diaphragm wall thickness, with the result that the conditions established during thermoforming m the foil edge region (for example, wrinkles and creases) will differ from those m the case of the can according to the invention, as can be produced, for example, by a process according to any of Claims 1 to 6 or with the aid of an apparatus according to any of Claims 7 to 10. The foil used here is in fact, for example, one having a slightly conical foil lE(rTUA^R0?ERfr^F]cEl OF NZ Ul 1 9 AUG 1999 " ~C EIVED 5 1'J\ ; ' ■ 0 which, after thermoformmg, is heat-sealed to the can inner wall in a broad gap between punch and can inner wall by expansion of the punch circumference as descnoca, for example, m US-A-4, 599, 1 23, has proved to be extremely disadvantageous since, on introduction into the can - without overlapping the cut edge of the can - it must result m the formation of creases, which make it more difficult, or even impossible, to achieve a tight connection between the foil and the inner surface of the can. possibilities according to the prior art for final mounting. However, since the foil used according to the invention is relatively thin and is preferably a foil having good thermal conductivity, use is made of a high-temperature joining process, for example the application of a heat-seal coating on the outer sartace According to an aspect of the invention there is provided a method of producing a sheet metal can having a diaphragm foil which is provided at an opening at one end of tne can, wherein the diaphragm foil comprises paper or plastic or metal foil, the method comprising closing the opening with the diaphragm foil so that the outside edge region of the foil extends outwardly substantially parallel to the central a<is of the can , is essentially cylindrical, and is tightly connected with the inside of the can wall without overlapping the edge of the can wall, the can being closed m the absence of an additional cover which is heat-conducting According to an aspect of the invention there is provided a semifinished can structure having a sheet metal sidewall chat is open at one end and fillable at the open end prior to sealing and closing of the can structure, the intermediate can structure having a closed end opposite said open end, the A o.oaa collar parallel to the diaphragm disc, There are of course a large number of 1 9 AU3 J029 6 introduced into the can 1 and connected to it Sj^e-jgc}^ edge. This is more advantageous because, m the conventional embodiment, it was necessary to ^Yof^ol^'ED either a predetermined breaking point, for example by punching, or a parting of the diaphragm foil edge overlapping the cut edge of the can from the diaphragm foil disc stretched over the can opening. In the case of a thin foil of preferably not more than 0.2 mm, m general even not more than 0.1 mm, this always gave rise to difficulties Of course, such a thin foil which serves merely for maintaining freshness or preserving aroma or for preventing contamination is relatively difficult to handle. According to the invention, it now has, along the circumference of a cover region 4, a foil edge region 5 which is raised all around and imparts a certain rigidity to the diaphragm disc part stretched over the can opening. For imparting rigidity (and also for achieving a slight, radial elasticity during deep drawing and/or -sealing) , the diaphragm foil 2 closing the bottom of the can preferably has at least one annular bead. The diaphragm foil 2 reinforced in this manner can now be picked up m an interlocking manner (so that the foil shape is not changed on insertion into the can opening), for example by means of a suction gripper known per se, and can be mounted on the top of the can 1 m a first step. Here, a further difficulty associated with a thin foil is encountered, it is in fact necessary to ensure that the foil remains on the top of the can 1 so that it can be tightly connected to the inner surface of the can in the next step. It would be possible m principle to provide the upper edge of the can 1 with an adhesive so that the film remains attached thereto m the desired position. However, this is advantageously effected according to the invention in a manner more readily evident from Fig. 2 7 In said figure, the raised edge is at" least slightly conically divergent, i.e there is! an ^i43&4Pft19S7 with the vertical V, which angle, although nnly ve^ry small is still measurable and has a magnitude than 5°, in particular less than 2° In a practical embodiment, the diameter of the lower surface of the diaphragm disc, i.e. m the region of the cover surface 4, is nnly a few tenths of a millimetre smaller than the opening diameter of the diaphragm disc, it being necessary for the height measured along tne vertical V to be only about 5 mm The upper, larger diameter of the diaphragm foil 2 is of course expediently chosen so that, when mounted, it is held on the top of the can 1 by the suction gripper by means of frictional force. A further measure for securing the diaphragm foil 2 on the top of the can 1 may consist m a collar 6 which has a hook-shaped cross-section and interacts with the upper edge of the can 1 . The upper, generally sharp edge of the can 1 is furthermore preferably flanged towards the outside (7 m Fig. la, 3), m order to prevent damage to the thin foil or injury to the user. The diaphragm foil 2 thus fits with this collar 6 firmly on the edge of the can. However, this is only an intermediate step m the closing of the can 1 and should not hinder the subsequent steps. This includes the action of a punch 8 which is shown only schematically m Fig. lb and presses the diaphragm foil 2 into the position shown m Fig. lb. The collar 6 slides from the position indicated by a dash-dot line m Fig. 3, in which it was present before being pressed down by the punch 8, into the interior of the can and, owing to the ductility of the foil material (with simultaneous sufficient toughness), assumes the position, indicated m Fig. 3 by solid lines, at the inner circumference of the can 1. The conical shape of the film edge region 5 with the small angle 13, which 8 N L. 1-/M ~ shape, the can circumference As a result of title S1 ^5Bvi5 conical shape, the formation of creases and'■ wriiiklis^-as mentioned expressly m US-A-4,599,123 - is avoided. As described below, the process according to the invention and the apparatus according to the invention result in a tight connection between the diaphragm foil 2 and the cylindrical region of the inner surface of the can immediately below the (preferably flanged) can edge: In a preferred embodiment, the punch 8 is formed according to the section shown m Fig. 4. It consists of several parts, namely the actual punch surface 9, which is connected to the lug 11 of a punch head 12 by means of upward-projecting pins 10 (only one is shown, but there are preferably three). A centring ring 13 is placed around the punch surface 9 and can be moved along guide pins 14 and against the action of at least one pressure spring 15. Usually, the ring 13 assumes the lowered position on the left m Fig. 4, m which, for example, it is supported on the upper side of the punch surface 9 in a manner not shown, but optionally is also held by other means. can edge, and has a recess 13' for this purpose. The process can now take place m such a way that the can 1 stands on a lifting table and is raised, with the result that the centring ring 13 is displaced against the action of the spring 15 to the upper position shown on the right At the same time, the punch surface 9 emerges from the interior of the ring 13 and thus presses the diaphragm foil 2 into the position shown m Fig. lb and 3. stationary and the can held m a centred position while the punch surface 9 is moved downwards. In this case, In this position, the centring ring 13 holds the Alternatively the ring 13 could also be ® 9 N £ PATENT OFFICE it would be necessary, for example, for the lag be m the form of a piston rod of a fluidic acfgregate, preferably of a pneumatic piston/cylinder aggregate. ^ x However, it is clear that m this case further latitude is allowed as a result of design considerations, since in fact only the relative movement of the parts shown and the can is important Furthermore, the centring of the can, or of the diaphragm foil 2 relative to it, could be carried out m various ways. From the above explanations, it is clear that it is important to position the raised foil edge region 5 of the diaphragm foil 2 as close as possible to the inner circumference of the can (as shown m Fig 3) m order to connect said edge region firmly to said inner circumference. For this purpose, the punch 8 has a spreading device, which is formed by a wedge arrangement m the embodiment according to Fig. 4. A row of wedge segments 16 is guided along the upper side of the punch surface 9 m such a way that they can be displaced radially outwards with respect to the central axis A of the punch 8. For guidance, the back of the punch surface 9 could have, for example, grooves or slots (not shown). However, the flat back of the punch surface may also be sufficient for guidance Although the wedge segments 16 as such could themselves be used for pressing the raised foil edge region 5 of the diaphragm foil 2 against the inner circumference of the can 1 , it is advantageous if elastic piston rings 17 or Seeger circlip rings are stretched around them. This provides a more uniform circumferential area when these rings 17 are pressed against the foil edge region 5 of the diaphragm foil 2 and moreover performs a dual function by also generating a restoring force which acts on the segments 16 A conical wedge 18 is provided for pressing the wedge segments 16 radially outwards, which wedge can be 1997 10 «>■ - • — pice M SEP 1997 gments with moved downwards and between the wedge se their wedge surfaces 20, by means of an actuatiiigQ^d —q 19 of a drive, preferably of pneumatic reason for preferring a pneumatic drive is that there is scarcely any danger of soiling by oil or leaked liquid and it is particularly easy to set a maximum pressure which does not extend the can When the conical wedge 18 is moved downwards against the punch surface 9, it spreads apart the wedge segments 16 and thus presses the elastic rings 17 against the foil edge region 5 (whic : is partially indicated m the bottom right of Fig. 4) m an outward direction, where the can edge fits firmly m the recess 16'. The position of the diaphragm foil 2 according to Fig. 1b is reached m this way. In this position, however, the diaphragm foil 2 must also be secured and in general also sealed This can be effected m a conventional manner by means of adhesive bonding, preferably by means of heat-sealing, because the thin diaphragm foil 2 does m fact transmit the heat relatively readily. For this purpose, the outside of the film edge can be provided with a heat-seal coat 21 (Fig. 2) A heating means is then coordinated with the spreading apparatus 16-18. Said heating means could be formed per se by heating coils housed m the wedge segments 16, but space is very limited there, and it is also necessary to provide movable connections Although this possibility should therefore not be ruled out, it is possible to provide a radiant heat source 22 (for example, an annular one), for example above the wedge segments 16 and the ring 17, which heat source heats these parts m order to warm up the heat-seal coat 21 (Fig. 2) and lo fuse it with the inner surface of the can 1. The wedge segments 16 may be formed, for example, from a ceramic material having good heat storage properties, which also improves the wear properties. , iiiLLj" orr^E 11 I l RF? 1597 Fig 5a shows the wedge segments 16 4n(3 a-.sJ££Jn(3 ring 17 m the closed position and Fig. 5bj shows theify'j^p m the position m which they are spread (by the wedge pieces 18 of the punch 8 which is not shown here and is moved at right angles to the plane of the drawing) for the purpose of heat-sealing the diaphragm foil 2 to the inner surface of the can It is clear that the wedge arrangement shown is only one possible embodiment which may be preferred with regard to the life of the apparatus, and that many modifications are possible within the scope of the invention For example, the conical wedge 18 could simply be formed by a pressure plate which is movable relative to the punch surface 9, it being possible to provide a rubber bellows between the upper side of the punch surface 9 and the pressure plate. Said bellows expands laterally from the top on being supplied with a pressure medium through the pressure plate which is used instead of the part 18 and which then would also be connected to- the rod 19 for actuating the latter, and thus presses on the displaceable parts 16 or directly on the ring 17 A horizontal drive extending radially outwards would also be possible for the individual segments 16, but would be of complicated design Particularly m this case, but also m other cases, heating of the upper can edge from the outside for heat sealing may be the simpler solution. As soon as the can 1 is closed m the position according to Fig. 1b, further, additional measures may be advantageous. For example, in order to protect the vulnerable diaphragm foil 2, a lid 23 or 24 (Fig. 1c) can also be mounted. Another particular advantage of the present invention is that the foils can be separately produced and, if necessary, kept m stock, and - where the cans 1 are of identical diarueter - cans naving different volumes can be equipped with the foils 2 which are 12 produced beforehand and, owing to their design with the foil edge region 5, are m fact sufficiently stable This foil edge region 5 can also be readily coated with the adhesive 21, which would be difficult to apply to the inner circumference of the can, owing to the dangei of soiling. On the other hand, the invention is of course not limited to the use of an adhesive, as already explained. The invention is not limited to the embodiments described Thus, the output of the apparatus according to the invention with multiple tools - for example, arranged on a turntable - can be increased m a manner known per se. NZ PATENT OrY\rS 2 4 SEP 1997 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> ,A L 233 1 3 °!$r f\ r f ^ 1 < ■< o WHAT I CLAIM IS 1 . Process for the production of a can of sheet metal having a closure diaphragm foil of paper, plastic film or metal foil which is provided on at least one end face, said diaphragm foil having an edge region being introduced into the can, and closes the one or more end faces so that the outer surface of said edge region which extends outwardly substantially parallel ro the central axis of the can is tightly connected to the inner surface of the can wall, said can wall being m cylindrical form, characterized in that said edge region is pressed against the inner surface of the can by means of a punch having an expandable circumference and thereafter the edge region being tightly connected - essentially over its total vertical distance - to the inner surface of the can under the action of heat, the expansion being effected without being opposed by a force from an external pressure absorption apparatus. 2. Process according to Claim 1 , cnaracterized m that the expansion of the puncn circumference is effected by the transformation of the axial movement of the punch into a radial movement of pressure elements, especially of wedge segments and/or pistor rings or spring rings. 3 Process according to Claim 1 , characterized m that the expansion of the punch circumference is effected by a pneumatically operated rubber bellows. 4 Process according to any one of the preceding Claims, characterized m that the edge region of the diaphragm foil used in the process initially is conically divergent and nas a hot-melt adhesive coat on its outer surface —I I 19 AUG 1999 I PECEIVPn 5 Process according to any one of the preceding Claims, characterized m that the diaphragm foil used in the process initially has, at the free end of the edge region, a collar which projects radially outwards and is approximately hook-shaped m cross-section 6. Process according to any one of the preceding Claims, characterized in that the diaphragm foil is embossed or grained 7 Apparatus for carrying out the process accordLing to any one of the preceding Claims, having a displaceably mounted punch with, a circumference spreadable trarsversely to tne displacement direction, a displacement means for tne punch and a spreading means for producing the corresponding movements being provided, cnaracterized m that the punch is displaceaoiy mounted inside a centring means for tne diapnragm foil ana tne can., and a heating means for tne circumference of tne puncn or for tne upper can edge is provided from tne outside. 3 Apparatus for carrying out tne process according to any one of Claims 1 to 6, having a displaceably mounted puncr witn a circumference spreadable transversely to tne Displacement direction, a displacement means for tne puncn and a spreading means for orcaucmg tne corresponding movements cemg crov_ced, characterized m tnat a centring means for tne ciapr.ragm. foil and tne can and a heat—ng means for trie circjroiersn.ee or tne puncn are prov_dec. 19 AUG 'iSSh r ' * 9 Apparatus according to Claim 7 or 8, characterized in that the spreading means comprises a combination of, on the one hand, at least two radially e\pandable piston rings or spring rings with openings offset relative to one another or, on the other hand, at least three wedges arranged in the form of a ring 10. Apparatus according to any of Claims P to 9, characterized in that the spreading means consists of a hydraulically or pneumatically operable rubber bellows arranged along the punch circumference. 11 A method of producing a sheet metal can having a diaphragm foil wmch is provided at an opening at one end of the can, wherein the diaphragm foil comprises paper or plastic or metal foil, tne method comprising closing the opening with the diaphragm foil so that the outside edge region of the foil e<tenas outwardly substantially parallel to tne central a<is of the can, is essentially cylindrical, and is tightly connected with the inside of tne can wall without overlapping the edge of the can wall, the can being closed in the absence of an additional cover which is heat-conducting 12 The method according to Claim 11, characterized m that the edge of the can wall is flanged on the outside and/or tne edge region of the foil diaphragm rests against the inner wall of the can essentially without creases and wrinkles 13. Sheet metal can produced by a process as claimed m any one of Claims 1 to 6 and/or with the aid of an apparatus as claimed m any one of Claims 7 to 10, wherein the edge reg_on of the foil extending outwardly substantially parallel to tne central axis of the can is tightly connected to the inner _.dqe of nr ■ST^- the can wall j OFfJz I 3 AUG (939 Tr, 16 "2r n 14 A semifinished can structure having a sheet metal sidewall that is open at one end and tillable at the open end prior to sealing and closing ot the can structure, the intermediate can structure having a closed end opposite said open end, the closed end being sealed by a closure diaphragm ot a material selected trom the group consisting of paper, plastic him and metal foil, the intermediate can structure having a central a.\is, the closure diaphragm having an edge region which extends outwardly substantially parallel to said central asis, the edge legion or the Diaphragm being tightly connected to an inner surface of said siaewall without overlapping an outer edge of said sidewall at said closed end, wherein an inner surface of said sidewall has a cylindrical shape m an area of the sidewall tnat is tightly connected to said edge region of tne diapnragm, and wherein the edge region of the diaphragm is free from an additional cover which is heat-conducting 1 - semifinished tan structure according to claim 14, having a configuration selected from the group consisting of 1) a can structure wherein the edge ot the can sidewall is flanged in an outward direction, and 2) a can structure wherein the edge region of the diaphragm rests against the inner surface of the can substantially without creases or wrinkles 16 A semifinished can structure according to claim 14 or claim 15, wherein the closure diaphragm is not more than about 0 2 mm m thickness, and is selected from the group consisting of embossed diaphragm material and grained metal foil 13 AUG i339 received 17 ^ ^ ^ «i - I"7 A process for the production of a can of sheet metal substantially as herein described with reference to any one of the accompanying drawings. 18 An apparatus substantially as herein described with reference to any one of the accompanying drawings. 19 A sheet metal can substantially as herein described with reference to any one of the accompanying drawings. 20 An intermediate can structure substantially as herein described with reference to any one of the accompanying drawings. END OF CLAIMS 1 9 AUQ 1222 I </div>