Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO90/11176 PCT/AU90/0011
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B~OW MOULDING MULT~PLE WAL~ED ARTXCLES
This lnventlon relates to blow moulding o~ multiple
walled hollow artlcles and ln particular, although not
limited to, containers havlng an external wall of
~hermoplas~lcs material.
In the past, in the construction of dou~le walled
thermoplastlcs contalners such as insulated vessels
having an lnternal wall defining a food or beverage
retaining cavity and spaced from an external wall, often
with an insula~lng medlum ln the cavity between the
walls, a number of manu~acturlng ~teps have been
required. Generally, the inner and outer wa~ls were
moulded as separate articles, the inner wall was inser~ed
into the outer wall, and thP marg~ns o the walls were
sealed together, often with a capplng ring. Preformed
insulating segmen~s have been introduced betwe~n the
wall~ as th walls are fi~ted together. ~he multiple
mouldlng~ and fabrication steps re~uired by this
35 technique have besn inconvenient insofar as the insertion
and capping/sealing steps have been time consuming and
accordingly expensive, while requiring the manufacturer
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to keep stocks of each of the preformed components
required to form the double walled container. ~ ::
It has been proposed in ~rltish Patent Specifica~ion
No. 1125609 to blow mould an outer ve~sel around a
preformed inner vessel, thereby reduclng the number of
fabrication steps and the nec~sslty to keep stocks of
each of the components of tha container. In ~his pa~ent,
the ~nterior surfaces of a prefor~ed .tnner ve~sel are
supported on a mandrel, a parison is e~truded around the
inner vessel and the parison iS blow moulded to form an
outer wall of the finished artlcle. The mandrel has an
in~ernal heating/cooling system and servPs to prevent
destruction or deformation of the lnner vessel during
blow moulding of the outer wall. The need for a
supporting mandrel does not allow thls technique ~o be
usad with anything other than straight necked inner ~`~
vessels, as otherwise the mandrel cannot support all of
the interior surfaces o the inner vessel. Si.milarly,
the ~echnique cannot be used to mould multiple w~lled
vessels having three or more concentric ves~els as access
cannot be provided for the suppo:rting mandrels into each
of the varlous lnter-wall spaces. ~ :
It is an object o~ the pr~sent invention to
amellorat ~ome of the shortcomings evident ln prior art
techniques for producing hollow multiple walled articles.
In accordance with ~he pressn~ $nvention there is
provided a m~thod of blow moulding ~ multiple walled
hollow artlcle ln which an inner v~ssel having a neck and
a hollow body is ~uxtapos~d with a mouldable sheet
extru~ion,
the segments o~ a spli~ mould are closed onto the
extrusion to form a substan~ially se~led parlson around
the body of the lnner v~ssel ln the mould with an annular
end portlon of th~ parison ex~ending closely around the
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neck o the inner vessel and
a fluid pressure medium is applied to a space
delned between the body o~ the inner vess~l and the
sealed parison to form a blow moulded outer vessel,
~he method belng characterized by pressurlzing the
interlor o the lnner vessel with a fluid pressure medium
during blow moulding of the outer vessel.
Fur~her accordlng to the present invention there is
provided a hollow multiple walled article blow moulded by
the method described in the immediately precedlng
paragraph.
The invantion also provides blow moulding apparatus
for producing a hollow multiple walled article, the
appara~us comprising:
means fur extrudlng mouldable sheet mater~al;
means for supporting an inner vessel ln
Juxtaposition with the mouldable sheet extrusion, the
innar vessel having a neck and a hollow body;
split mould seyments arranged to close onto the
mouldable sheet extrusion to form a substantially sealed
parison around the body of the inner vessel in the mould
with an annular end portion of the parison extendlng
closely around tha neck of the inner ~essel; and
means ~or applying fluid pressure to a space defined
between the body o~ the inner vessel and the mould
segments to blow mould the parison onto the mould,
the apparatus being characterized by further
comprising means to apply fluid pressure to the lnterior
of the lnner vessel during blow moulding of the parison.
In th~ method and apparatus of the invention, the
application of the fluid medium to the lnterior of the
35 inner vessel can preven~ the inner vessel from being
distorted, burst or otherwise damaged dur~n~ blow
moulding of the outer vessel. The pressure in each of
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the sp~ce between the lnner and outPr vessels and the
interlor of the lnner ve~el is advantageously
sub~tantlally equal during th~ blow mouldlng step.
Conveniently the same source of pressure msdium is
provided for said space and said interisr in which case
means may be provided in the pressure medium onduit for
compensating for di~fsrences in volume between said space
and sald lnterior in order to apply the deslred pr~ssure
thereto~ The volume compensatlon means may be l~ the
13 form of pressure regulatlng means and/or variable volume
means.
In one embodiment of the multiple walled hollow
artlcle, the space defined between the inner vessel and
ou~er vess~l is used to insulate the inner vessel. This
may be achieved by drawlng a vaouum in the said space and
seallng it upon remov~l of the respective fluid pressure
applicatlon meanQ. Alternatively, an insulation medium
such as a foamed polyurethane may ba in~ected into the
space~ .
In another embodiment of the multiple walled hollow
article, the space between the inner vessel and outer
vessel is itself used as a separate storage space for
beverages etc. or a remo~able haat: exchange medium such
as iced water. To achiev~ this the said space can be
provided with its o~n neck and s~opper or cap to allow
access therein.
The lnner vessel may itself deflne a plurallty of
lnterior cavities and unless a con~rary sense is implied,
the term should hereinafter be construed to include su~-h
multiple cavlty vessels.
In one arrangement of a multlple cav~ty inner
vessel, the hollow body is par~itioned by one or more
lnternal walls to define a plurallty of sidP by side
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cavltie~. In an alternative arrangement, a multiple
cavity inner vessel may comprise a central lnterior
cavlty sur~ounded by a plurallty of concentric walls
defining at least one substantially annular space around
S the central cavity.
Conveniently, with each of these multiple cavity
arrangements, each cavity ls provided with a respective
neck ~o allow access therein so as to allow ~ plurality
of differen~ beverages etc. to be carrled without
intermixing. To achieve thls it wlll yenerally be
necessary for the parison to be confin d closely around
each of the necks durlng blo~ mouldlng of the outer
vessel. Where a multiple cavity inner vessel is provided
with a respective neck for each cavi~y it w~ll generally
be necessa:ry to provlde a respectiv~ source of fluid
pressure for each of the n~cks to ensure pressuriza~lon
of each cavlty ls chieved.
The annular end portion of the parison which extends
around the or each neck of the inner vessel will
typically seal therearound ~y shr.inking thereon. If the
composition~ of the inner and oul~er vsssels are
compatible, the closing of the mould segments may cause
the portion of the parison lying closely around the neck
o~ the inner vessel to become welded thereto to form a
common neck of the hollow multlple walled article.
Alternatively, the necks of the lnner and ou~er vessels
may be adhesiv~ly bonded together.
Convenlently, the outer surface of the neck of the
inner vessel ls provided wl~h protruding beads or ribs
around whlch the parison may extend durlng sealing
thPreof around ~he neck, thereby to more securely anchor
the neck of the outer vessel to the neck of the lnner
vessel. I~ partiGular, beads or ribs on ~he neek
extending in a generally axial direction (i.e. from the
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lip of the neck towards the bottom of the inner vessel)
rnay, when the neok of the outer vessel ls shrunk
thereover, prevent the lnner ves el from rot~ting
relatlve to the outer vessel. Grooves provlded axlally
along the neck of the inner vessel may have the same
effect. Alternatlvely ribs or grooves provlded
circumferentially around the neck of the lnner vessel
may, when the parlson ls shrunk and sealed therearound,
prev nt the lnner vessel from belng dlslodged from the
o:lter ves~el 1n an axial directlon.
In a stlll furth~r embodiment, the fluid pressure
medium for blow mouldlng the outer vessel may be
lntroduced around the neck of the ~nner vessel so tha~ a
gap remains between the necks of the inner and outer
vessels whlch may be sealed, for example by an insula~ing
material whlch assists location of the inner ve~sel
relative to the outer vessel in the finished article.
In general, the space defined batween the inn~r
vessel and the~mould segments withln which tha outPr
vessel is blown will extend ~ubstantlally annularly
around the inner vessel. Alternatlvely the outer vessel
~ay extend along a portlon of the inner vessel body as
well as i~s nec~ to form a common multilayered wall and
~hus the spac~ between the inn~r and outer vessels will
have a somewhat C~shaped cross sectlon.
Protrud~ng rldges or bead~, as dlscussed above in
relatlon ~o the neck o~ the lnner ve~al may also be
pro~ided on ~he body of tha inner vessel to aeslst in
locating it within the ou~r vessel. With this
arrangement, the closlng of th~ mould ~egments wlll
generally cause the parlson to lie or become welded
adJacent the rldges or beads, and the blow moulding step
will produce hollow regions therearound.
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WO90/11176 PCT/AU90/00117
Conveniently, a blow pln for blow mouldln~ e~r
vess~l enters the mould at an end portion remote frcm
where the ~nd portlon of the parison will be moulded
around the neck of the inner vessel, in which case a
small aperture will typically remain in the bottom of the
finished article. Alternatively, the blow pin may ent~r
the split mould to one side of the portion which moulds
th~ outer vessel around the neck of the inner ve~sel. In
each case the remaining aperture may b~ used to insert an
lnsulatlng ma~erial such as polyurethane foam or to draw
a vacuum ln the space defined betwP.en the inner and outer
vessals.
~he fluld pressure medium will generally comprlse
alr, but other fluids may be appropriate. For lnstance,
i~ may be appropriate to in~ect a settabl~ liquld as the
blowing medlum, which on ~et~ing may act as an lnsulator
for the hollow double walled article.
The material for the lnner vessel may comprise any
appropriate material but will generally be a plastics
materlal. Alternatively the inner vessel may comprise
other materlals such as glass or metal. It w~ll be
appreciated that the applicatlon of a fluid pressure
medium to the or each interior cavlty of the inner vessel
may allow a comparatively fragile inner vessel to be
used. The inner vessel may have a composit~ construction
havi~g, ~or instance, an tnsulatlng layer on ex~ernal
surfaces thereof. Where ~he lnner vessel ls itself of
multiple ca~ity construction each of i~s respec~ive
vessels may be of different materials.
The mouldable sheQ~ Pxtrusion to form the sealed
parison will generally be an open tubular parison.
~lterna~ively ~he mouldable sheet extruslon may take the
form of two or more opposed sheets, edges of whioh are
sealed togethPr by the closlng split mould segments to
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form the sealed parison.
Materlals approprlate for the parison include, for
instance, polyethylene, PVC, polycarbonate, polyamide,
polyace~al.
The inner vessel may be placed under an e~trusion
port and the mouldable she~t extrusion ex~ruded around or
adjacent the inner v~ssel. Alternatively it may be
10 appropriate ~o extrud~ an approprlate length cf mouldable ~ :
sheet extruslon and then to juxtapose the lnner vessel
withln or b~tween portlons o the mouldable sheet
extrusion. This may be achieved by manoeuvring the inner ~:
vessel into place within or between the mouldable sheet
extruslon.
With either of the above arrangementQ, extruders
which do not constantly extrude the sheet mat~rial are
particularly convenient to allow su~icient time to
20 complete the ~uxtaposltion, mould closlng and opening, ;~
blow mouldlng and axhaust steps, before the next length
of sheet materl~l is extruded. An accumulatlng head
extruder, in whlch the extrudable material accumulates in
a piston arrangement when extrus:ion ls lnterrupted, is an
example of a non constant extrus:ion apparatus.
An al~ernative extrud~r uses travelllng nippers or
sciss~rs whlch cut the ~op o~ an approprlatP length of
extrusion and convey it away from the ~xtrusion port, for
instance, down toward~ a moulding station dlsposed below
~he parison ex~ruslon area ~o be juxtapos~d wlth the
inner vessel. ~ travelllny parison arrangement is
particularly convenl~nt a3 lt may allow a further len~h
of mouldable sheet extrusion to be prepared whil~ a first
length is belng sealed with the mould segments and blow
moulded.
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Two embodlments of a hollow douhle walled artlcle
made in accordance with the invention will be described
by way of ~xample only wlth reference to the accompanying
drawings in which:
Flgure 1 ls a slde sectional view of a first
embodiment of a blow moulding apparatus wlth mould
segments in the open positlon;
Figure 2 is a side sectional view of the flrst
embodiment wlth the mould segments ln the closed
position; and
Figure 3 is a front sectional view of a second
embodiment, looking into a mould segment.
In figures 1 and 2, the blow mouldlng ~pparatus 10
comprises a parison extruder 12 for extruding a tubular
mouldable sheet extrusion. The extruder has a screw feed
14 and annular extrusion port 16 Por produclng an open
thermoplastics parison 18. Extending through the parison
extruder 12 and coaxlal wlthin the extrus~on port 16 is a
blow pin 20 ~onnected ~o an air csupply (~ot shown~. The
blow pin 20 extends below the parison extruder 12.
Parlson cutting means (not cieplcted) are also
provided below the parison extrucler, adjacent the
extrusion port 16. The blow mou].dlng apparatus further
comprises a pair of matable blow mould segments 30, 32
adapted ~o close 1n a horizontal plane around a portion
of the parison. In figurP 1 the blow mould segments 30,
32 are depicted ln an open positlon (support means
omitted for clari~y) and in Xigure 2 the blow mould
segments are deplcted in the closed positlon, clamped
around a parison length. The blow mould segments 30, 32
may themselves act as the par~son cutting means.
Each blow mould segment 30, 32 has an lnternal
moulding surface 34, 36 respectively defining two halves
of a screw n~.cked bottle. At the top each blow mould
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segment 30, 32 has an upper half gate 38 to accommodate
the blow pin when the mould segments 30, 32 are closed
therearound. A lower blow pln 40 extends upward from a
point below, but coaxlal wlth, the upper blow pin 20.
Each mould segment 30, 32 has a lower half yate 42 at a
bo~om portion thereof to accommodate the lower blow pin
40 when ~he mould segments ar~ closed therearound.
Th~ lower blow pln 40 is connected ~o the same air
supply as the upper blow pin 20 through a regulator (not
shown~ able to ad~ust the air flow through each blow pin
relative to each other to apply an approprlate volume of
air through each blow ptn and thus e~ualize pressures as
descrlbed in ~reater detall below with reerence to
figure 3~
The nozzle 44 of the lower blow pin 40 has an
exterior surace 46 adapted to b~ snugly received in the
neck 48 of a preformed inner vessel 50. The inner ~essel
50 ls held, neck down wlthin the open parlson and ~s
generally coaxial with it.
The surface 46 of the lower blow pln nozzle 40 is
positloned such that the lower half gates 42 o~ the blow
mould segments 30, 32 oan accommodate the neck 48 of the
inner vessel 50.
When position~d on the lower blsw pin nozzle 40 r the
end 52 of the inner vess~l 50 remotn from th~ neck 48
lles near, but not touchlng the upper blow pln 20.
. As show~ ln figur~ 1, an annular space 54 is de~ined
between the open parison 18 and the ~nner vessel 50 when
the mould is ln the open posltion.
Generally, the lower blow pin 4Q will be retractable
such that an inner vessel 50 can be lnser~ed thereon and
the innar vessel manoeuvred into the approprlate posl~ion
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coaxial with the parison extrusion port 16. A parison
length ls then extruded around the inner vessel 50
through the extrusion port 16. E~trueion ls ceased when
the end 56 of the parison is at least parallel with ~he
neck 48 of th~ lnner vessel.
Thereafter, the mould segments 30, 32 are clo~ed
around the parison 18 thereby cutting o~f any exce-~s
length of parlson. Lower moulding surfaces 58 and 60
ad~acQnt the lower gate halves 42 together defining the
screw neck of the finished moulding, force the lower end
portion of the parison, ad~acent its end 56, closely
agalnst the n~ck 48 of the inner vessel to hrink it
therearound and form a common neck for the flnlshsd
moulding, and so seal the end of the parison remote ~rom
the upper blow pin ~0. The upper ~ate halves 38 of the
mould segments 30, 32 close around the upper blow pin 20
and so seal that end of the parison.
A fluid pressure medium such as alr is introduced to
the now sealed annular cavlty 54 throu~h the upper blow
pin 20 to blow mould an outer wall 60 of the fini~hed
ar-icle, against the moulding surfaces 34, 36 of th~.
mould segments and thus to form a double walled hollow
artlcle havin~ the walls united at a common neck but
having an annular space between th~ walls elsewhere.
Fluid pressure medlum may al~o bs introduced to the
annular space 54 prior to sealing o4 the neck 48.
A Pluld pressure medlum is also introduced into the
interlor 62 o~ the inner ve~sel throu~h th~ lower blow
pin 40 to equali2e pressure wlt~ln the annular spare 54
and thQ lnterlor of the lnner vessel 62. A the
respective volumes of annular cavity 54 and th~ lnterior
52 of the inner vessel are different, to equallze their
pressures requlres tha~ the respectlve volumes o air
blown in should also be correspondingly different. One
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~O90/11176 PCT/AU90/00117
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arrangement of achlevlng this dlfferentlal volume of air
i5 descrtbed ln greater d~tail wlth reference to figure
3.
After blow moulding has been completed, and the
outer vess~l has cooled sufficiently, the air ls
exhaus~ed in such a manner that the respective préssures
wlthin the lnner vessel and between the tnner and outer
vessels are malntained substa~ti~lly equal to each other
to prevent dlstortlon or rupture of the inner vessel.
~he mould segments 30, 32 are ~hen opened, and the lower
blow pin, with the double walled articl~ attached may be
retracted to remove the artiole from the upper blow pin
20, leaving an aper~ure in the outer wall 60 at the end
of the vessel remote from the common neck. This aperture
may be used, for lnstance, to lnsert an insulatlon medium
such as a foamlng polyurethane compositlon.
The embodiment of Figure 3 is similar in overall
concept but moulds a common neck between the inner and
outer walls of tha article, ad~acent an aperture for
in~erting a blow pln into the generally annular cavity : ;
betwaen the walls.
In ~gure 3, a front view of a spll~ mould segment
70 is depictad w,~tn an lnner vessel 72 in place on a
first blow pin 74. A stmilar, opposed split mould
segment (no~ shown) definPs the mould when closed on ~he
mould segment 70. As wl~h the embodlmen~ o~ figures l
and 2, th~ neck 76 of the lnner vessel is snugly received
on a nozzle R8 of the blow pin 74. AdJacent a gata 78 of
the mould or receivlng the first blow pin 74, threaded
internal surfaces 90 of the mould, in the closed position
closely surround the neck 76 ~o weld the neck to a
parlson. Th~ mould segment 70 has a fur~her gate 82 for
recelvin~ a second blow pin 84 which extends into a
cavity 86 between a mouldlng surfaca 90 of th~ mould
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segment 70 and the lnner vessel 72. Between the gates
78, 82 the lnternal ~urface of each mould segment has a
raised handle mouldins portion which cooperate to allow a
handle to be integrally blow moulded with the outer
vessel. The position of the tubular parison, prior to
closing the mould segm~nts is ~ndicated by phantom lin~s
92.
The respective volumes of the inner vess2l and ~he
space de~ned bet~een the lnner vessel and the mQuldlng
surfaces of the mould segments dlffer. As lt ls
desirabl~ to equalize the pressure ln each of these
volumes during the ~low moulding ~tep and subs~quent air
exhaust step, the apparatus is provided w~th pressure
equalizatlon means to allow a single souree of air to
metre a respec~ive appropriate volume of air into each
space.
The pressure equalization means comprises a source
of pressurlzed filt~red air (not depicted) connected to
an alr llne 94. The air line 94 has an ad~ustable
regulator 96 upstream of a solenoid two way valve 98
having an exhaust port lO0 and downstream line 102. The
downstream llne 102 branches into an inner vessel line
104 leadln~ ~o flrst blow pin 74 and an outer vessel line
106 leadln~ to the second blow p:ln 84. Inner vessel line
104 and ou~er vessel line 106 each have a respective ~low
control valv~ 108, llO lntermediate ltS blow pin and its
connection ~o the air llne ~4. The flow control valves,
two way valve and regulator are shown schematically in
this drawing. The flow con~rol valves 108, llO each
serve to independently regula~e air flow i~ bo~h the
blowlng and exhaust dlrect~ons.
To further metre the respectlve volumes of air to be
applled from each blow pin 74 and 84, the inner 104 and
outer 106 air lines each have a respective variable
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volume chamber 112, 114 ln the form of an ad~ustable
pi~ton arrangement. Thus, t,he dlfference ~n vDlume
b~twaen the lnterlor volume o the lnner vessel 72 and
the space between the inner vessel and mouldlng surfaces
86 can be compensated by appropriate ad~ustment of each
variable volume chamber thereby to allow an equalization
of pressure withln each of these space~ dur~g blow
mould~ng and subsequ~nt exhaus~.
In flgure 3, the volume of the ~ariable volume
chamber 112 associated wlth the lnner vessel blow pin 74
is relatively small as its piston 116 is near tAe end of
~ts stroka and is disposed ad~acent the variable volume
chamber's connection 118 with air llne 104. ~n contrast,
variable volume chamber 114, to metr~ a smaller volume o
air to be blown lnto the relatively small space 86
defined between the inner vessel and mouldlng surfaces,
has its piston 120 set to de in~ a relatlvely large
volum~. The respeotive adJustments to suit a particular
common air input pressure can be set empirically or by
mathematlc l calcul~tion of the d~ffer~nces in Yolume of
air to be blown~ Thls arrangement of pres~ure ~ :
equallzatlon mean~ is partlcularly convenient as lt
allows a~r pressure wlthin the lnner vessel and outer
vess~l to be equalized yet uses a si~gle source o~ air
pr~ssur~. Furthermore, becaus~ th~ varlable volume
chambers 112, 114 and flow con~rol valves 108, 110 are
each lndep~ndently ad~u~table, the apparatus can be
adapted to blow mould hollow multlple walled art~cles of
di~erent volume~ and conflgurations.
Ad~us~men~ of the volume~ o~ ~luid pre~surs medium
metred through each blow pln has be~n dlscussed by
reference to equalization o~ the pressure achieved ln the
inner vessel and between ~he lnner vessel and parison.
It will be apparent, however, ~hat particularly where the
robustness of the inner vesq~l is known, some variance in
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the pressures requlred in each space may be allowed and
the varlable volume geometry hereln described can be used
accordlngly.
Typically, mouldlng of double walled articles
according to the second embodiment may invol~e placing a
preformed ln~ r vess~l 72 upon the first blow pin 74 and
ad~acent the second blow pin 84, whereupon a parison
length ex~ruded els~wherP ~nd supported by cutting
lC scissors may be manoeuvred over and descend around the
inner vessel 72. Mould segments 70 are then closed
around the parison whereupon a common nec~ of the double
walled artlcle ls formed around the first blow pin. Air
ls applied to the cavlty 86 be~ween the inner vessel 72
and moulding surfaces 90 of the mould to blow mould a
double walled hollow articl~ having an integ:ral handle, a
common n~ck and a cavity between the walls.
An insula~ing ma~erial, such as a foaming
polyurethan2 composition may be :Lntroduced to the cavity
between th~ walls of the double walled artlcle by way of
the aperture left ln the outer wall after wlthdrawa~ of
the blow p~n 84.
Al~ernatively, where ~his double walled article ls
i~self u~ed as the inner vessel for a further application
of the method and apparatus of th~ present invention, the
apertura left in the outer wall after the withdrawal of
the blow pipe 84 may hP used to apply fluid pressure
medium in addi~ion to ~luid psessure medium applled to
the innexmost vesssl 72 through its neck 76, during the
blow mouldin~ of an outermos~ vessel. Wlth this further
appllcatlon ~o msuld a mul~ipl8 wall article, lt may be
parttcularly convenient to provlde the blow pin for blow
moulding the outermos~ ves el a~ ~he remote end relat$ve
to the neck of the lnnermost and ~ntermedia~e vessels.
WO ~/11176 PCT/AU~/~117
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The descrl~ed embodlments hav~ been advanced merely
by way of explanatlon and many modificatlons may be made
thereto wlthout departlng from the spirlt and scop of
~he lnvention whloh includes every novel feature and
S comblnation of novel features herein dlsclosed.
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