CA2133312A1 - Process and installation for producing aluminium cans for beverages or foodstuffs - Google Patents

Abstract

ABSTRACT
The invention relates a process for manufac-turing beverages cans made of aluminum comprising the following process steps: coating of pure-aluminum slugs (10) with a soap-based lubricant; impact extrusion of the slugs (10) to form cups (20); ironing the cups (20) to form can bodies (30) with simultaneous molding of the bottom; cutting the can bodies (30) to length; cleaning the can bodies cut to length by washing with a mildly alkaline, aqueous cleaning medium, rinsing and drying;
lacquering the can bodies cut to length and cleaned;
necking and flanging the can bodies cut to length and cleaned, to form finished beverage cans (40). The can (40) manufactured in accordance with the process accord-ing to the invention has, both at the can wall and across and bottom, an minimum wall thickness determined by the strength of the material and by the strength requirements relating to the beverage can.
(Figure 1)

Description

,_~ P0717 ~ 33 PROCBSS AND ARR~G1~3T POR ~ZW~PACT~ING
B~:Y~RAGE~ 3 0~ ~I~

The invention relates to a proces~ for manufac-5 turing a beveraye can made of aluminum an~ to an arrange-ment for carrylng out the process and to a co~e~ponding beverage can made o~ pure aluminum.
Beverage can~ m~de of aluminum are manufactured according to the prior art by means of, in a fir~t step, 10 a cup being prodllced by cuppirlg fr~m a ro~lnd piec~ of body sheet, said cup b0i.ng cylindrical having a bot tom area which i~ greater than the bottom area of the fin-i~hed can, and having a cylinder height w~lich i~ ~ller than t1~at of thQ f inif3hed can . In a ~econd ~;t~p, t.his cupped cup is formed, by ironin~, lnto a cylindrical CaII
whoae dimensions corr~pond to the dimen3ions of the f i~iah~d can, apart ~rom ~ slightly great~r wall h~ight.
During this second proca~ing Btep~ the ironing, the bottom i~ formed at the ~ame time. The can i~ then 20 proce~ed into a f~nlshed beveraga can by means o cutting to lengthJ cl~ning, lacquering (outaide and inside), necking and flanging. A proces~ of tbi~ type i nor~ally used to manuf~ctur~ beverage can~i made of alloyed alu~rlinum.
A fu~ther proceas for manufact~ring beverage cans made o~ alumi~ tar~s from a ~3lug from which, by ~eans of impact extru~ion, a c~n body i8 for~ed, whone dimen-~3ions~ apart ~ro~ a ~lightly gre~er wall height, corre cpond to tho~e of the fini~hed c~n. ThiEI can body i~
30 llkawi~a prvccEI~ad by cutting to length, cleaning, lacquering, necking and flanging to give, the fini~had be~e~age can. U~ lly thi~ Becond proceaB iB u~ed to manu~acture beverage c~ns msde Of pure aluminum.
The c:anr) manufactured accordin~ to the two 35 proces~es msntioned bo~h ha~e the drawback that their wall thickne~, at lea~3t zonally, iB not de'cermined by the strerl~th of the ma~e:rial and ~he strength , ~ ~

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pO717 - 2 ~ 33~2 ..
re~uirem~nt~ relatin~ to the Can, but by th~ manufac-turing pr~CesB. In t~e cas~ o~ th~ ~upping proc~Gs thi3 ~, particula~ly relate~ to the can bottom, whone thicknesn e~aentially corresponds to the thickne3s of the body nheet, and to the can wall zone at a dîstance from the 1~j bottom, which zone, for the purposc of problem-free ,~$,',1 necking, must be thicker than required in term~ of 3I strength. In the impact extrusio~ procens it ~elaten ~o the ent.ire can wall, whlch haa a minimum thicknens deter-mined by tho im~act extru~ion procen3, a~ well a~ the transition zone between wall and bottom which likewine ~ han a thickne~n defined by the process. I~ other words, l this ~eans that the beverage cans manufactured according to the prior art processe6 are heavier than absolutely neces~ary~
Furthermore, the round piece~l of sheet metal, which are punched from a Htrip o~ roll~d ~heet me~al and are u6ed as the qtarting material for the cupping pro-. ce~s, cause iDevi~able wastage of ~ 3tarting material which, having been produced by a number of process ~teps, is of high quality.
The object of the inventi~n then iD to specify aproce~ and to prov.ide an arrangement by meann of which beverage cann made of al~minum can be manufactured, whose wall thickne~ in ~ ones are [~ic] de~ined not by the manufacturing proce3n but by the str~ngth of tlle material used and by the ~trength requirements r.elating to the can. At the name time, the proae~g in to make it posnible to uDe, a~ the ~tarting material, a material which can be manufactured an simply ac~ ponnible ~nd in Eew proc~s~
~3teps, in 9u~:h a Way th~t lrlevital~le .scrap~ c~s well as the cans themnelveu, can be reproce~d i~to th~ ~tartiIIg material with little ~ost and effort (recycling). The actual proce~ accordin~ to the inv~ntion i~ to nati~fy high environmental requirem~t~ At the name time, the proce~n according to the invention, without iner~a~ed CQst of appliancen, ia to provide or productio~ rate~
which are ~omparable with the production rates of the ,~ P~7~7 ~ 3 ~ ~ ~33~2 prior art proce~s~
This ob~ect i~ achi~ed by the proce~ ha~ing the eaturs8 according to P~te~t Clai~ 1 a~d the ar~angement having the eature9 according ~o Patent Claim 4.
The proc~3 ac~ording ~o the invention ~tart from ~lug~ made of pure aluminum, whlch ~re punched ~ro~
unrolled ~heet metal a~d are commercially availa~l~ as ~uch, which mlnimize~ the wa~t~ge problem for the manu-factur2r. ~he proce~ according to ~he in~ention i~ ba6ed on forming from E~uch a alug, by mean~ of impact extru-8ion, a cyl~ndrical cup who~e botto~ haa ~ greater diameter than haE~ the bottom of the fini~h~d can. Thi~
cup i~ molded into ~ can body by iro~ing, the bottom at the same time b0ing molded by pre~slng. ~he can body i6 then p~ocessed by means of cutting t~ l~g~h, cleaning, lacquerlng, necking ~nd flanging to ~ive the finished c~n.
The impact ~xtr~l~ion proce~3E~ per~i~a the di~
tribution of material acroE~E) the can b~ttom to be tallorcd to the ~trength requirement~ relating to the fini~hed can, i.e . t~e central zone of the bottom advan-tageou~ly to b~ mad~ thinner than the ~i~ zone. The mini~u~ wall thick~e~ ~chievable ~f the imp~ot-e~ruded cup in the vicinity of the cylinder wall and in parti-cular in the cyli~der wall-bottom tran~ition ~one i6 determined by the .impact extru~ion proce~. sy mean~ Of ~he ironing ~ep it i3 pos~ible, howe~er, to reduce thi~
wall thickns~s to ~ degxae d0~in2d by th~ ~rength requirementa, includi~g, in particular, in the wall-~ot~om ~ran~ition zone, if ~he diame~er o~ the cup iB
chosen to be ~lightly larger khan the di~n~ter o ~he can and, a~ ~ ~re~ult, during ironing the material of the outer~o~t ~ction~ of the cup botto~ i~ al~o inYolved in the irolling pro~e~.
3S The proce~ according to the in~ention thu~
e~ble~ ~aslufactur~ o~ a beverag~ can who~e wall ~hick-ne~e in each zone (~yli~der wall, bottom and tran~itio~
zone) ean be freely predefined within wlde range~ and 2:~333~2 ~ P0717 - 4 -- thu~ be adju~ted in accordance wlth the ~trength r~quir~- m~nt~, whe~e~ accordlng to the known cuppi~g proce6s thi~ only applies to the bottom zone of the can wall a~d according to the known impact extrunion proce~s only to th~ can botto~ ln neither ca~e the~efore applying to t~e top zone of the can wall and to ~he transition zons be~ween can wall and san bottom. Thi~ al~o ~e~, how-ever, that the proce~s according to the i~vention enables manufacture of a can with a minimum of ma~erial. This economic adv~ntage ic further reinforc~d by the fact that the ~tarting material in the ~orm o~ slug~ of pure aluminum i8 inexpenaive, thank~ to waate recycling pos~ible at very little co~ ikewi~e, prod~ction o~
slug~ from u3ed cans i~ Blmple and not e~pen6ive. The~e lS economic advantaga~ fa~ outweigh th~ additional materi~l required owing ~o the lower ~trengt~ o~ pure aluminum.
In addltlon to the economic ad~antage# of the can~ manufactured in accordance with the proce~ accord-ing to the lnvention ther~ are environmental advantages which, in particular, a~e that it i~ po~sible to l~e, for impact ~xtrusion o~ pure ~luminum, a ~oap-ha~ed lubricant and that the cans can then be wa~hed with a~ environ-mentally adva~tageou~, mildly alkaline cleaning medium, ~urface gllalities being produced in the proce~s whlch preae~t no problem~ what#oev~r in ~b~eque~t lacquering.
~n contra~t, canD made of alloyed alumin~m have to be wa~hed acidically to achieve the ~ame ~urface q~a}ity, which cau~e~ di~po8al problem~.
The proca~ according to th~ invention and an arra~gement fo~ aarryl~ out the proces~ will now b0 de~cribed in d~t~l with r~fere~ce to the following figure~, in which:
Pigure 1 8how8 ~chemat2cally, how a beYe~ag~ can i8 produced in acaorda~ce with tho procees accord-ing to kha i~ventio~;
Yi~urs 2 ~how~ a ~chsmatic pre~entation o~ the arrange~e~t for carrying out th8 proce according to the invention;

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~igure 3 ~how~ a ~ch~matic ~ection through an ex~mpla~y be~er~ge can ma~ufactured by mean~ of the proce~ according to the inventi~n.
Figuxe 1 ~howa, ochematically, the individual 5 Bt3ge8 of the proce~c according to ~he invention.
In a fir~t pSOCf'5~ tep (lubricating), a glu~ 10 ~ade o:E purs alumin~ (purity 99 . 0% or higher) i~ coated with a soap-based lubrlcant. ~his ia done, for example.
in a alug drum whlch ic ch~rged with 81ug~ and lubricant.
I~ a ~econd proce~ ~tep ~impact extru~ion) thore i~ produced by imp~ct extru~ion, fro~ the ~lug 10, a cylindrical cup 2~ havlng ~ cup wall 21 and a cup ~otto~
22. To thi~ end, the 81ug ia placed i~to a female die and, by mean~ of a male die, i~ pre~sed again~t the f~male die, mate~ial. flowing in the oppoRlta direction between male and female die and thu~ bein~ for~ed into the cup w~ll 21. I~ ~o doi~g, the face of the malo dle and the male die travel are designed in BUCh a way that the ~up ~o~tom 22 o~ tho cup 20 produced e~entially cor-20 re~pond~, in t~3r~ of ma~erial di~3tribution, ~o thepredefined bottom of the fini~hed can. Advant2geously, the cup bottom 22 o~ ~he cup produced il3, a~ ~hown, thinner in the ce~tral ~one than in the ri~ zone~. The cup wall 21 h~ ~ height which i~ ~malle~ than tho wall height of the finiehed can ~for example from 25 to 75 thereof ), and the cup bottom 22 ha5 a diam~ter which i~
greater than ~he diameter of the bottom o~ the fini~hed can.
The second p~oce~e ~tep can be carried out by ~0 employlng a conventional i~pact extru~ion appliance. The tr~vel o~ the lmpact extru~ion mal~ die for producin~ the cup ~0 in con~iderably chol-t.er th~n the tra~el o~ a cor^
re6pondi~lg tool ~or manufacturirlc~ a can body (proc~ss according to the prior art) . Since the time required for i~npac~ extru~lon primaxily depend~ on qaid tr~vel, this ~ea~ an increaae in capaclty ~or the proce~ accordiug ~o ~he invention.
In a third proc2~ 8tep ~iro~ling and botto~

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~ ~0717 - 6 2133312 formlng) there i8 in~erted into the cup 20 an ironing ram who~e diameter corre~po~d~ to the inte~nal diameter o~
the flni~h~d can. With the aid of ~aid ironing ram, the cup 20 i~ drawn through one or mo~e ironing rings having an lnte~nal diameter whl~h decre~e~ in the direction o~
movamsnt of ~he cup. The clearence ~etwee~ the last ironing ri~g and the iro~ing ram corre~pond~ to the ~tipulated wall thickness o ths ini~hed can. In the same operation, the bottom of the cup i~ pres~ed into a stipulated shape between the face of the i~oning ra~ and a co~nter^tool. ~he two tool~ molding ~he boktom to this end have ~hape~ corresponding to one another. The product of the ironlng and bottoM-formi~g ~t~p i~ a can hody 30, whose ca~ wall 31 haa ~ thickne~s which satisfie~ the strength re~uireme~t~, ~or example i~ ~sentially con~tant over the entir~ can wall, and w~1ich iA slightly higher than that o~ the fini6hed c~n. In crder ~o increa~e the ~tability under load of the can, the can botto~ 3~, molded in th.i~ proce~s step, i~ advantageously ~O not only curved concavely toward the can lnterior but ha~
additional ~hape el~ment3 which incre~e re~istance to pre~ure and by means of which the bottom thick~ess required can be ~urthe~ reduced. Such a shape elemen~
increasing re~istance to pre~ure i~, for example as ~how~, a ~tiffening ring 35 who6e diameter i~ small~r than the ext~rnal diameter of the can and approximately ~orre~po~d~ to the in~arnal diameter o a recessed can lid, in ~uch a way that the Atiffen~ng ring additionally as~i~t~ the ~tackablli~y of the cans.
The thi~d proce~s step can be carried out by e~ploying a convent~onal ironing appliaPce.
In furthe~ proce~a stepA~ the can body, in a mannër k~own per ~e, iB cu~ to size, cleaned, lacque~ed out~ide and in~ide, neckod ~nd flanged. Thu~ the finished 35 be~era~e ca~ 40 1c produced. For ~he purpo6e of cleaning~
the can body, cut to ~i~e, is wa~hed with a mildly alkaline, aqueou~ cleaning medium and i~ the~ rin~ed and dried.

,r~ P0717 ~ 7 ~ ~1333~2 Fis~r~ 2 BhOW~, ~chematically, an ex~plary arrange~ent for manufacturing beverage cans made of aluminu~ in accordance wlth the proce~ according to the invention. Thiu arrangement e~nentially ~on~ist~ of an appliance S for coatlng the ~lugs Wit}l lubricant, for exAmple a ~lug dru~, o~ at leaat one, adv~n~a~ously two appli~nce(~) r~.l and F.2 for impact extruaion of the 91ug~ to form cups, an appliance A for ironing the cups, can bodie~ to form an appliance s or cutting the can bodie~ to ~ize, au ~ppliance W for cleaning the ca~
bod~e~ cu~ to ~iz0, a~ appliance L for lacqueri~g and an appliance ~ for neckin~ and f lanying the can~. All the~e appliances are known per ~e and therefore need not be de~crib~d here i~ detail.
Figure 3 ~hows, llfe-ai~e, a ~ection thro~gh an ex~mpl~ry beverags ca~ manu~actur0d in accordance with th~ proceE~ accordi~g to ths in~entio-n. The left half ~how~ the fi~ished (necked and flanged) be~erage can, the right half Qhowa the can body cut to ~ize. The can ahown 2U haa an internal ~olu~e o~ 350 ~1 and iB de~ig~ed for a minimum bur~ti~g pre~ure of 12 bar. It i~ made of A19g.~. It ha~ tha ~ollowing wall thicknea~ea: central zone 41 of ~h~ bottom 0.46~0.01 mm, outer xone 42 of the bottom 0.66i0.01 mm, can wall 43 ~.24~0.01 mm. The tranaition ~on~ 4~ ~etwe~n bottom and wall 1~ narrow and ha~ a conti~uou~ tran~itio~ f~o~ th~ bottom th~ckness (0.65 ~ to t~e wall thic~ness (0.24 ~m).
Obviously it .i~ alao pos~ible ~or larger or ~maller cans to be manufactured in accordance with the 30 process accord.ing ~o the invention. It i0 al~o possible for the can to ba necked more markedly in order to b~
able to be closed with a ~maller ea~y-open e~d. In prin-ciple it is poa~ibla to manufacture, ill accordance with the proceas accordin~ ko the i~en~ion, beverag~ can3 which can be clo~ed With any ~ize of lid (sm~ller than the can diameter). ~he can shown in Figure 3 can be ; ~uikably ~ecked for lid~ ha~ing di~meter~ lea5 than 60 mm.
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Claims (10)

PATENT CLAIMS

1. Process for manufacturing beverage cans (40) made of aluminum, comprising the process steps:
a. slugs (10) made of pure aluminum having a purity of at least 99.0% are coated with a soap-based lubricant;
b. slugs (10) are formed by means of impact extrusion into a cylindrical cup (20) having a cup bottom (22), the diameter of the cup bottom (22) being larger than the diameter of the bottom of the bever-age can (40);
c. the cup (20) is molded into a can body (30) by means of ironing, the cup being drawn through one or more ironing rings by means of an ironing ram and, at the same time, the cup bottom (22) being molded by pressing between the face of the ironing die and a counter-tool;
d. the can body (30) is cut to length;
e. the can body cut to length is washed with a mildly alkaline, aqueous cleaning medium and is then rinsed and dried;
f. the can body, cut to length and cleaned, is finished by necking and flanging to give the beverage can (40).

2. Process according to Claim 1, characterized in that there is produced, in the impact extrusion step, a cup (20) whose bottom (22) in its central zone is thinner than in its outer zone adjoining the cup wall (21).

3. Process according to either Claim 1 or 2, characterized in that in the ironing step the can bottom is curved concavely toward the interior, and a shape element increasing the resistance to pressure is pressed into the bottom.

4. Arrangement for carrying out the process according to any one of Claims 1 to 4 [sic], comprising an appliance (S) for coating the slugs with lubricant, at least two appliances (F.1 and F.2) for impact extrusion of the slugs (10) to form cups (20), an appliance (A) for ironing and bottom forming of the cups (20) to form can bodies (30), an appliance (B) for cutting the can bodies (30) to length, an appliance (W) for cleaning the can bodies cut to length, an appliance (L) for lacquering the can bodies cut to length and cleaned, and an appliance (E) for necking and flanging the can bodies cut to length and lacquered, to form beverage cans (40).

5. Beverage can made of pure aluminum having a purity of at least 99.0%, manufactured in accordance with a process according to any one of Claims 1 to 3, charac-terized in that its bottom in a central zone (41) is thinner than in outer zones (42) adjoining the can wall, in that the can bottom is curved concavely inward and additionally has shaped elements which increase resistance to pressure.

6. Beverage can according to Claim 5, characterized in that the bottom of the can has, as a shape element increasing the resistance to pressure, a stiffening ring (45) whose diameter is smaller than the external diameter of the can.

7. Beverage can according to Claim 5 or 6, charac-terized in that can wall (43), above a narrow transi-tion zone (44) between can bottom and can wall, has a constant wall thickness which is smaller than the wall thickness of the can bottom.

8. Beverage can according to any one of Claims 5 to 7, characterized in that it has, in a central zone (41) of the can bottom, a wall thickness of 0.4 ? 0.2 mm, in an outer zone (42) of the can bottom has a wall thickness of 0.7 ? 0.2 mm, and in the zone of the can wall (43) has a wall thickness of 0.2 - 0.35 mm.

9. Beverage can according to any one of Claims 6 to 8, characterized in that it consists of Al99.5, has an internal volume of 350 ml, in a central zone (41) of the can bottom has a wall thickness of 0.46 ? 0.01 mm, in an outer zone (42) of the can bottom has a wall thickness of 0.66 ? 0.01 mm, and in the zone of the can wall (43) has a wall thickness of 0.24 ? 0.01 mm.

10. Beverage can according to any one of Claims 6 to 9, characterized in that its opening is necked in such a way that it can be closed for a easy-open end having a diameter which is smaller than the diameter of the can.