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Патент USA US3100716

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Aug; 13, 1963
3,100,711 _
P.. E'lS'L'ER
Filed July 18, 1958
5 Shen-z’cs-Shee’rl l
Paul Eis/er
Aug. 13, 1963
_Filed 'July 18, 195s
5 Sheets-Sheet 2
m ..Minw„m,
by á/îäczß(
Aug. 13, 1963
Filed July 18, 1958
5 Sheets-Sheet 5
Paul. E \S\_ER
(31th ÓPmej
Aug. 13„ 1963
-Filed July 18, 1958
5 Sheets-Sheet 4
Attoaney .
» Aug. 13, 1963
P. E'lsLl-:R
' -
Filed July 18, 1958
5 sheets-sheet s
Paul. Emsa
bj ¿.jßw
United States Patent ” ice i,
Patented Aug; 13, 1963
a carryingout the invention on `account of the versatility
and choice of materials, forms and decorative treatments
it offers, and the variety of" different technical require-_
Paul Eisler, 57 Exeter Road, London NW. 2, England
ments it can satisfy. VThe manufacture of the foil'pattern
-'zlliletl July 18, 1958, Ser'. No. 749,554
Claims priority, application Great Britain July 24, 1957
on the plasticiilm, the provision of additional layers and
the satisfaction of the variousv technical requirements de
14 Claims. "(Cl. 99`--171)
scribed later can follow some of the now well-known linesV
of packaging practice and permits the use of the cheapest
The supply of hot food in catering establishments such
metal foil tthin aluminium foil) on practically lany type of
as restaurants and canteens, schools, hotels, camps and
hospitals, through vendingmachines, tothe motorist or 10 plastic film which would in all probability be chosen for
the particular packs in anycase so that the cost is sub
passenger inltrain, ship, .plane o_r coach, and last but not
stantially not much greater than that of normal packaging.
least to parties and individual-s in private homes depends
- The heating ñlrns ofthe invention are designed to yworkV
so much on personal service and/ or costly equipment that
reliably only once with the foodstuff or eating appliance
itis found ever more unsatisfactory.
’The object of the present invention is to simplify the 15 with `which they are associated. i A design for repeated
useÍwould defeat a» good deal of the hygienic purpose ofY
heating `of food 4and it does this by means of a dispensible
heating'ñlm forming an electrical resistance of large sur
face area and very small thickness, which` is associated
with a food package or an eating appliance »and includes
the invention apart from the cost involved.
. Designing for a single occasion of-.use is carried out
which when so connected is capable of supplying vheat to
(A) Keepingthe film as intact as possible until thisy occa
by a combination of steps which within the paramount
terminalareas for attachment to a low voltage supplyvand 20
the` food at a predetermined rate.
» '
of cost and economy aim at
sion arises
` The heating film in many'cases will-form part’lor the
(B) Making the film of wide applicability notwithstanding
Whole of a food package though other possibilities are
1 the great variety of requirements ofvarious foodstuffs
and their treatment prior to this occasion while saving
any provisions which would be required if the film
enyisaged and will be described.`A In any case the resist
anc'e'may consist of Va metallic pattern, preferably `of me
-tallicrfoil for-ming a ñimsy structure. Preferred struc
tures will beldescribed later in more detail, but briefly
they' can be visualized as` flimsy Ifabrics consisting of a
metallic foil pattern on a thin plastic filml
were to' be used again.
Thelow voltage on which the iihns are designed to
operate may advantageously be» theI same as that of the
usual motor car battery, namely l2 volts. For use on
„ The ilimsiness of the heating ñlm is primarily motivated
by ‘reasons of cost and heat capacity butit presents the
problem of satisfying the abovev aims, (A) in full and (B)
at least in part. v To thisend (a)vthe current path of the
metal foil pattern irrespective whether it is itself in» series
on parallel with other paths, is subdivided into several
aircraft they may be designed to operate at 24 to 28
small and interlinked paths asl long 'as their widths
volts as >supplies at this voltage areiusually available. 35 parallel
do not. become too small, remaining .say larger than 0.01Provision is however made in some cases to operate them
inch thus* avoiding difficulties due to pin holes.
' for‘avery short time (to give a high heat shock),at about
The .co-pendingl U.S. Patent applications Serial No.
48 vo1>t`s`,`but' always remaining below the voltage level
whichit `would be dangerous to touch and below the volt-_
age which is subject _to the insulation and earthing regu
lations of various electricity authorities.
s The heating films as proposedby the present invention
are disperisible` for hygienic reasons and convenience.
They have therefore to be produced Very cheaply and
this is m‘ade possible by the present invention apart from
theuse of a very simple method of production of the film
Vbecause they are designedto be only lflimsy structures
Without needy „of and provision for good class electrical
783,633, nled November 110„_19585 new Patent No. 3,020,u ,
378, íand .Serial No. 789,221, `filed December 29‘, 1958,
` «describe themethod »of expanding 'foil into such multi
path meander line patterns which are the preferred- way
p of carrying _out the alb-ove step.
'(b) The metal ~foilis crimped. In said U.S. applica
45 tions it has been shown how this crimping assists pro
ductionof the Yfilm but in the present context another
aspect of crimping' isV used. The crimped metal foil pat
tern is not only Iin-uch more elastic than the smooth pat
tern rand therefore better capable of surviving indents or
50 other local stresses, it to some extent .also compensates -the
achieying even surface temperature and without substan
hot spot ette-ct dueto a hole which interrupts only one
tial Jor` particular mechanical protection against the ulti
or a ‘few of the small parallel interlinked paths of a
mate user’s'handling- of the food. .Y 'Ihey are cheaply pro
insulation, without a heavyv heat conductive mass for
lwhole pathway.
duceable also because they are `onlyrequired Yto work
4the following: Crimp
reliably `not more than onc'e and because they usually 55 ing rneans that a major part of i-sthe
foil surface is at a
form part ofv the food package or eating appliance so that
slope to the overall surface of the «film and that the to
talarea of this overall surface is smaller than the total
actual foil area would :be if all crimps were stretched
Theremare íilm materials under development,v> and in
lf -a hole is made in apart of a'meander Ylimb
'some cases' already in limited production, which can be 60 ' out.
which reduces its width'the intact limb on this Width
used as‘heating ñlms without a patterning process. Such ` is stressed by nearly the same force originating largely
at most only a fraction of their total cost is an additional
film materials are for instance ultra thin titanium foil, - ' from the crimps dueto inherent »stresses as was exercised
lacquered steel foil, or plastic films on which a metallic
layer has been deposited by vacuum evaporation or which
on .the width ofthe whole limb. It consequently ñattens
out to some extent. As- the main heat 4transfer is -i-n
are otherwise coated with an electrically conducting layer, ' 65 the directionV normal to the overall surface of the rfilm,
or which contain a high carbon or graphite filler. When
their production will have been `improved ‘and will have
reduced their cost sufficiently, they can be used -for the
the flattened part can `dissipate heat better .and remains
therefore a 'somewhat cooler hot spot than would bave
been the case with an equivalent smooth foilpattern..
y(c) _The invention protects the heating ñlm against any
. At the present time, however~and this‘relates to cost, 70 corrosive influences `of the foodstuff and--in -compliance
withy heal-th regulations-«prevents any danger of >food
uavailabilityand qualityÍV-a plastic film carrying a metal
present invention.
foil pattern isfpreferred. v It is also a preferred means of
being poisoned bythe heating tilrn, if necessary by pro
viding a thin layer between riood and foil (such :as a plastic
areas apart. A diagrammatic section is shown in FIG
film, or a coating on the Ifoil) but as the film is not to
URE 1. The foodstuíf has a loop of the foil l2 with-l
in it with a slip k13A of insulating foil ybetween theV ends
be reused it ‘does not have to he provided with mechanical
protection from ‘damage caused -by emptying Ithe food .
from the package or using the eating appliance, hy scrap- f
and the whole is contained in `a paper or like Ibag E14.
The lsl-ip 13 may ibe adhesively secured and as shown it,`
ing or .tearing it with cutlery, or even «by removing it
may conveniently be part of the bag folded over. " " Pref
from the hot Kfood. vThis is strictly in accordance with
point (B) above.
erably also the bag is constructed so .that the top must
he torn away to gain access to the terminalfareas `and
In the heating film the prime function of the .-foil sup
porting ylayer is the [same as in the normal ifood pack
to provide an air-vent during heating.
age, that is to :serve as :a barrier-layer, :a container, a
decoration carrier etc. ~ To put the metal _toil‘pattern
the connector Vshown in FIGURE 2 which comprises a
'Connection of the foil to theV supply may be made by Y
y simple spring clip ydevice consisting of two pivoted arms
on it is not a necessity, but -in the main a measure to ’
15 terminating in jaws pressed together in thisexample
make it as effective and to keep -it as intact as possible
by the aid of a bow spring 16. The leads 17 bringing
without much extra cost until it is used. Using .a normal 15 the supply are connected to foil contactsV 18'backed by
food packaging material as a support lfor the lfoil pat
rub-ber or >like insulation 19‘ mounted on the jaws and
tern permits a thinner and therefore more resistive foil
which engage the terminal areas of the heating film such”
pattern than would otherwise be practicable and thus
as the ffoil 12 of FIGURE l. To avoid short-circuitinîg
permits a sare and economical voltage (.12 volts up to 48
the supply when the clipl is released withouta'heating
volts tothe used). Its insulating .function at _such a Ívolt 20 iilm inplace but with the supply still connected with the
age is 4very secondary.
lead 17, the foils 18 exten-d over ‘less than half the length
»The practical production method -of ‘some ofA the
of the jaws and are not opposite one another, but the
. major types of heating hlm are described in said co-pend
backing 19 extendsV over the full length so that the jaws i
ing U.S. patent applications while the present invention
also includes novel structures and ymeans which will be 25
described later.
The invention willvbe further Idescribed with reference
to the accompanying drawings which illustrate a number l
of possibleembodiments and modes of uses of the heat
ing iilm without being in .any way. exhaustive.
--FIGURE 1 illustrates a particularly simple form of
f »
squarely press against the terminal >lareas on the ñlm or
one another.
I-f, as shown in FIGURE 3, one jaw carries two foil
contacts 19al withv separate leads to each contact and the
other a single contact 19b, this'device can also be used
for connecting to a heating film with two electrical paths Y
and bringing these paths into series or parallel by exter
nal switching. For the same purpose there can also he
another terminal arrangement with two foil contacts on '
FIGURE 2 shows in end viewa convenient form ot'
both the opposite jaws of the Vconnector and four` leads v
connector lfor making rapid connection to the terminals
the insertionor removal of the food ‘package operates,
of a heating ñlrnaccortding to the invention,
35 the switching directly.
y ,
FIGURE 3 shows in a view at right angles to FIG
If the foil in FIGURE 1 needs patterning Vto give the
URE 2 a development of the connector,
` necessary resistance, the necessary coherence can be ob
-¿FIGURE 44 shows :an example of a heating iilm in- _. tained ‘by using expanded foil as describedV
iny said Co
tended totb'e looped andk lsealed into .a bag, I
U.S. patent applications. Alternatively - a` dat
`FIGURE 5 shows onegfor‘m of heating iilm which can 4.0 pending
meander patterning can -be used which, >as shown inV FIG
be «folded up to yforni a bag,
URE 4, can be given the necessary coherence y'by lreplacing
’ FIGURE 6 shows the application of the heating iilm v the
insulating slip 13 of FIGURE l by an adhesive, insu
‘ of the invention to aca-mister,
tape 23 extendin-gright across the foil 2tv before
{'¿FIGURES 7 and »8 are views at right angles to one
the latter is looped, in order‘to hold the limbs of the pat- '
another of a device according tothe invention for heat
ing "the contents of a bottle during pouring out,
kFIGURE 9 .shows a mode of using the heating iilm so '
as to‘- attain very rapid .heating off‘tfoodstuiis in the form
ofA slices,
Another -very simple material »for use for instance for
50 sistin'g of a laminate of patterned aluminium foil and plas
‘ FIGURE 1‘1 shows’y yet another alternative to FIG
to givefthe pattern the necessary coherence. e
, >bags or Wrappings is a two-layer packing material con
.t 'FIGURE‘lO shows jan alternative to FIGURE. 9,
tern spaced correctly along a central strip.`v4 The tapelcan“>
obviously be made of whatever width may be necessary
"FIGURE-'12 is a plan view showing a fform of Íìlm
used Vin wrapping :slabs of deep trozen foodstuff,V
f ‘FIGUREY 13 is a sectional end view showing one of
thewrapped packages using the ñlm of FIGURE 12,
FIGURE 14 is a diagram showing the process of form
tic lilm. The choice of plastic ñlm depends--apartfrom'the usual packing` considerations (compatibility with con
tents, vapour-permeability, price,_s-trength, facility Afor dec
oration, etc.)-on~ the temperature endurance of the >pai-7
ticular plastic. When the intended heating temperature
is low enough it permits the use of ordinary polythene
iilm, polyvinylchloride, ’ regenerated cellulose (cello
ing the packagejof FIGURE d3, .
phane) and `even paper. Where higher temperature plas
f 'FIGURE -'15 yis a plan view ‘or part of another form of
tic films are needed, irradiated or high density polyethyl
deep Áefrozen package,
60 ene, polycarbonate, or polyester ñlm is chosen while oth
i Í FIGURE y16` is a part sectional View` of the complete
ers may become available in the course of time. Y
' package-'erstellten 15,
` FIGURE 17 is a section Lof] a combined connecting
)FIGURE >18 is a »sectional detail ofone arrangement
of >termina-Isin a package embodying the heating film,
If, for instance, a bag is made from this two-layer'ma
terial, the aluminium toil is ñrst patterned by any known
process, |such as expanding as in said U.S,' patent appli.-`
cations or punching slots. The pattern provides one (or
more) continuous valuminium line(s) with Very small
ygaps between' them and covers nearly the whole area ofY
the bbag except for certain strips which are not connected
steamingl the _ foodstuff.
`~The simplest Iformi `of all of the heating yfilm is no 70 with the continuous heater'line(s). As shown by'fway of
example in‘FIGURE 5 the continuous >lines are pro
more than apiece «of aluminium Ãfoil, preferably pat- `
duced by rows of apertures Z5 and long slots 26.- Consid
FIGURE 19 is a sectional view of a pack intended for
¿terned‘t‘o increase its electrical resistance and suspended
with-in a mass of granular foodstuff such as potato crisps
f in a conventionallpaper or other »electrical insulating bag
together with just enough insulation to keep the terminal
eration will -show that this results in a number of mean:
dering paths inl-parallel beingproduced between-a ter
minal area 27 and -a terminal area 28 of each portion of
Y the patterned area. w Between each suchpatterned arear
cording to the invention-#also provide other effects de
and not connected with 'the continuous >heater lines are»
transverse strips 29 which yform edge reinforcements on
the fold when the material is folded intoa bag.2 I-t will
A three layer structure of the final package can also be
made by fixing a two-layer material round av canister
be understood that a repeating pattern is produced of a
(metal wall of canister-plastic nlm-foil, pattern) or in
continuous length of insulating support 3,1 which is sev-v
ered `at ìthe dot lines andffolded at the ,dotY and dash
lines, FIG. 5. Another strip 32 lalso not connected
side or outside another'food container. "Fór such fixing
purposes it is proposed priorvto or after' patterning,- to
with the continuous lines is arranged -along each edge. l ' apply »an adhesive layer, such as- self-adhesive coating,
to the plastic nlm or .to the aluminium -foil of the two
This isa narrow line with many holes or notches to in
or three-layer material. The adhesive must be chosen to
withstand not `only the operating temperature safely, but
crease its resistance. When the material is folded into
a bag, the longitudinal edges are folded over and these
ñne line patterns 32 are connected to a suitable voltage
supply to provide the necessary sealing heat. The over
‘laid plastic film edges weld together in the areas of the
also to suit the surfaces it has to stick to.
By its application to a three-layer' material a four
liayer material including heating the film proper is ob
tained to which again further layers can be added dur
Y gaps between, within, and around the metal lines 32.
ing processing or fixing to the container or appliance wall.
The flexible part of this heating film however,`cousisting
The hot metal lines themselves also become adherent to
the plastic. This procedure is, of course, only possible
of adhesive and plastic film or films, metal foil or foils,
ink and sometimes paper or cardboard or similar"v fabrics,
where the heat-sealing temperature‘lies well above the
designed maximum operating temperature of the bag and
where the seal is not affected by operating temperature.
With the particular arrangement shown, when the bag
is completed there are two separate patterns, one on each
side, each having two termina-lV areas. A device similar
to that shown in FIGURE 2 may be used but with each
of the two rubber packings 19 each carrying two contact
Y foils extending over a little less than half length.
remains an extremely cheap dispensible material. llt 'per
mits a choice lof placing a metallic, plastic, adhesive or
cellular surface on the inside or outside of the food con--v
tainer or appliance, permits 'most conventional decorative
treatments and adds som-e further facilities for decora
25 tion. It is safe to touch when connectedto the low
foil contacts opposite one on the two rubber backings'will
be of the same polarity so that whenlthe device is4 closed
Without a bag in position, there lis no short-'circuiting
'I'he `pattern of the continuous heater line or lines is
‘usually a vmeander with very small gaps, Wide and short
voltage supply. The thinness of the heating' nlm renders
it less important to its heating efficiency Whether' the
source of heat, which is the fo'il pattern, is nearer the
inside or the ioutside of the nlm. Thus the choiceof the
material to be in contact with vthe food and/or the con
tainer or appliance wall is not restricted.
-Where hot food is likely to attack the plastic film ther
mally ror chemically, the heating film of the invention
consisting of continuous aluminium foil-adhesive and
an ornament, sign or lettering, or `take part in the deco
-rative treatment of the package. The anodizing and col 35 paper-foil pattern, used with the aluminium foil inside,
that is in contact with the hot food, offers particular ad
ouring facilities available for' aluminium can‘be utilized
vantages and the paper libres will keep apart the two
to enhance lthis effect, and decorative printing can be
metal layers even when Ithe plastic or other adhesive which
combined with printing of acid resists for etching for the
bonds the llayer of the tti-lm softens. For heating to still
same purpose. The ink onlyy needs to be cleaned off the
40 higher temperature thin asbestos paper instead of ordi
arms covering nearly the whole tarea available as shown .
in FIGURE 4. It can however he so shaped as to form
It is also possible to imprint the aluminium. foil on the
nary paper may Ábe used as separating layer, as Vgllass
side bonded to the plastic film prior to the laminating or
ñbres, polytetrañuoroethylene or other very high tempera
coating process. The term coating refers for example
t-o the plastic film `:being made by lacquering the. alumin
ture enduring plastics are still tòo expensive for a dis'
pensib-le heating film.
Vassociation or incorporation a three layer material, not
separately producing on‘the one hand the foil pattern
An adhesive based on waterg'lass and put on in drop
rather than in la continuous -film is suitable for stick
some extent for instance by overprinting the gaps with
ing the foils to the paper. It is preferable to coat this
an inkof'the vcolour ofthe reverse side of the foil. '
heating nlm with a varnish, and it is'v not necessary to use
. The aluminium foil pattern can befon the inside or on
an expensive heat-resistant varnish. It may soften or
theoutside of the package. To reduce damage in trans- .
«the operating temperature without damage to the
port it is advisable to >provide a protective `coating by 50 orack'a-t
operating function «of the heating film. ‘ The -production
varnishing or bonding of'lak plastic, `usuallytransparent,
of this high temperature heating film is best effected by
film over it. In thiscase the heating `film hasbecome by
ium foil. ’ The gaps in the pattern can be hidden to 45
on the varnish nlm and on the other hand the aluminium
55 foil laminated «to asbestos paper with the sodium silicate
adhesive. Both 'materials are then bonded together,~ `with
In the rstructure plastic' film-‘foil patternaplastic film, ' the
same or a similar adhesive, the foil pattern faee being
1 there _can be substituted for the'foutward plastic nlml 4prac
placed against the asbestos paper. f
„ ticallyany'insula-ting material suitable for the pachage,
VThe foregoing Idescription has so far illustrated the
and. of `the desired thermal'insulation-and mechanical 60 basic structures and the production ‘of heating films able
>counting the layer or layers of ink for foil patterning lor Z,
properties. vThus plastic foam, papier mache, corrugated ^’
- ._paper, cellular cardboard crate material, etc. can be used
as the outside layer. Alternatively and based yon conven
tionalpackaging considerations such material or a metal
,foil or `other metal wall may `:be stuck to the plastic nlm
while the ifoil pattern remains Without a protective plastic
A! structure of’ a three> layer materiali unpatterned
aluminium foil-plastic film-aluminium foil pattern is
»very suitable for foi-l packs and forms a preferred mate
rial-for nexible pack-aging. "In view‘of the good heat con
duction of the unpatterned aluminium foil which is de
to achieve any «desired temperature permitted by the par
. ticular` materials incorporated-_say up to about 600°
F.-during the short operatingl time of the heating nlm. >
This coversv the range of temperatures required for ¿ile
freezing `food and for keeping food warm and heating it
'up for immediate consumption or in boiling, steaming,
baking, stewing, frying `and other cooking-operations.
Before describing further varieties' of the structure of the
dispensible heating nlm which aire all the subject ‘of the
present invention, several 'applications of the heating nlm
vwhich are themselves :also subjects of the present inven
tion will be described by way of example.
sirably about .002 inch thick, thev `foil pattern can leave
The description of these applications will also help to
more gaps of the area and thus «be used more easily for
illustrate some of the further structural features of sorne
A‘decorative enects or lettering. >'This material can-ac 75 species of the heating iilm according to the invention
which will be described in conjunction with an example
of their application.
It is "not >necessary to ‘always heat 4up all slices while ’
they are in their box or container.y The heating film can
One of the simplest uses of the heating iilm will be in
have terminals (not shown) at the foldsgto permit the
heating up ‘cold precooked food ranging from soups to
heating up of a single slice vor of a group of slices, and
pies and puddings, from sausages to stews, from vege 5 the heating can be arranged either while the slices are in
tables `and fruits to drinks of many kinds. _In the case of
the box or outside with the heating webs partly unfolded.
packages Vof some frozen‘food` itmay be «only necessary
(d) Instead of inserting slices into the folds of one or,
to heat them up to quickly defreeze the food which is
`eaten coldwhile with other frozen food packs and in
Amore long heating webs the slices 52 can as shown in
FIGURE l0 be wrapped individually in heatingñlms 53
providedrwith tear off zones 54 between the slices.` For
enclosure in a box the Áwhole length may befolded zigzag
case of most other wrapped or -tinned or bottled foods it
is desired to heat them upquickly to be eaten or drunk
at the zones 54 or rolled up. All the heating films in .one
box are patterned so that the complete pattern is coherent
The'following examples will illustrate the application ot
the heating iilm as or in some of the above food packages:
(a) In FIGURE l6 the heating film is a disc or wide
tape 33 stuck or otherwise fixed to the outside of a can
ister 34. It is supplied with the canister or separately.
The terminals, one being shown at 35, are on end flaps
and the parts belonging to each slide are connected in '
parallel, but each part has accessible terminals indicated
at 55. In this way provision is made to permit heating
of slices singly or in a groupafter tearing off the ñlm
containing the single slice or group, or when for instance
which `can be folded against ythe Wall of the canister.
all groups are in series all together, inside or outside the
.For separate> application the film may be supplied With a 20 box. Perforations in the heating film will permit the easy
self-adhesive backing in long‘length or as labels in a roll
escape of vapour (for crisping) or of steam. Thepro~
‘ Vor in a ñat dispenser.
posed method of heating will also permit the marketing of.
(b) The heating film is an “immersion” heating tape or
.tube putA inside a ycontainer of liquid or semi-liquid food
new types of food in tliinslices, such as saus-ages, minced
meats, tarts etc.
» ï
lor it is a bag containing the vfood placed inside a rigid tin, 25
(e) An alternative to the tear-off heating nlm is a com
jar or other container. In this category also falls theV
pletely separate heatingl film 56 for each slice 57 asin
provision of a» heating film as a strainer at the mouth of
FiGUR-E ll. In this case the inside'of the box 58 `can
a liquid food container or ofa tubular collapsible or
have metal foil strips which» connect all heating films as
folded~up «heating` ñlm immersed in a bottle or dispensing
long as they are in the box. The simplest arrangement
device. The heating film .is switched on only when it is 30 isïto provide terminals 59 at the ends. of eachglilm and
`fullystretched out orunfolded y¿and liquid is to be poured`
two supply strips in the‘box so that all are in parallel but ~
, '.ou-t. `Both varieties of ñlm «can be associated with meas
it is preferred to connect heaters of ¿a number of indi- i
uring and dispensing devices for the liquid and can ac
lvidual slices in series. y They form a group and all groups
tually constitute such'devices either inside the bottle or
container or be fixed outside to the cork Ior screw- stopper.
1n a box are paralleled. Thus as shown there may be
short strlps 6l in’the‘box each connecting two adjacent
terminals~59 and if these strips are energised .as indicated"
They heat more or less only the liquid poured out Iand do
this ideally while the liquid is being dispensed ( and meas
by the signs + and - the desired scheme is obtained.. ..
ured). By way of example as shown in FIGURES 7 and
(f) A particularly useful application of the invention is
8 a film formed into a tube 36 passes through the stopper
to the defreezing and re-heating of precooked deep frozen »
voli a bottle 37 andA its upper end is cut off at a slope to 40 food Whether in establishments such as restaurants and
form Aa pouring spout. `Just where it comes through the
canteens, in aircraft or other vehicles or again in places
.stopper its sides are pinched in and the terminal areas are
ì provided >here to be engaged by a forked wedge form con
nector 38 on which connecting foils are provided to make
of entertainment, inthe home or in camps. Certain
Vlittle so that its lower end rises above a boss 39 on the
weight and the space occupied by it.
bottom of the bottle whichpreviously. closed it and
lallows the bottle contents to be poured out becoming
«heated as they flow along the tube. An additional closure
It is proposed to fill food while hot from cooking `intok
containers .which "are considerably shallower‘t-han are
equipment is saved and in the case of aircraft and other
vehicles there is avaluable saving not only of the cost of
.contact with the terminal areas and lift the tube 36a 45 such heating equipment, but even more important of. its
' f `and sealedcover `can be provided at the upper end of
¿the tube to exclude dust and the like before use and to
-ensure that the bottle has not been tampered with.
(c) In FIGURE 9 the filnr is a long web 41 folded,
concertina~wise, the folds holding thin slices 42 for the`
‘foodstulf The Whole may be enclosed in the usual wrap
ping or»_container. This arrangement permits very quick
heating up in Viewk of the large surface area in contact
with the food and the thinness of the` food sandwiched
customarily yused at present »in large kscale catering, so
150 that when deep frozen the-,food is inshallow slab form
and to equip the slabs-with the heating film preferably
lover lboth large surfaces but at least over the lower large 'Y
surface. The film `.may be presen-t in'rthe containers or` it
may be wrapped around the partly or fully frozen slab.
The first part of the :freezing is vdesirably effected very
quickly Iby a coolant of such low temperature that at
least ya »deep frozen 4wall is formed along the walls. of
"the Vcontainer (which is'provided with'a separating film
between the folds of the heating film. There may be a
or release agent) so that the food can then be removed. " `
slice in each fold, but for easier removal of the hot food, 60 .The container can be .returned for Vreuse while the »freezing
as shown only the »odd folds of the web are filled with
1s cont1nued_ at the >usual Atemperature of the cold store.y
food slices, the even folds being compressed together;
vWrapping and sealing of ftherheating ñlm is then effected
,'thus‘the lweb assumes a comb-like configuration.
`or completed and the slab is then ready for delivery 'to ‘
comb ends Vmay as shown be bent to enclose the slices*>
the place of use._ It will be observed that the containers Y
completely. The heating ñlm may be porous or perfo 65 never Lleave the *factoryV and are: in any case 'rapidly re- i ï
to use.
rated to permitcirculation’ of liquid or vapour between
us, the num-berr of containers requiredY
g adjacent slices or the slices may have 'inner wrappings `for
1s reduced and the problems of cleaning and sterlizingV
are much simplified. "
easier and cleaner removal. More than one web may lbe
arranged in afood package or container. This `applica
If the food is t-o be served in `the usual -way ionl plates,
tion ofthe heating film is one preferred Way for quick 70 the film is preferably of Vflexible type so that after
.deffrjeeaingof.deep-frozen food, for rendering Iwafers and v defreezing and heating the food can be squeezed out of
biscuits crisp again and for many solid foods which are
the film as out of a .collapsible tube.r If fthe slab isa
enclosed in a package of insufficient surface areas to per
.single portion, the package can be supported on the
mit a speedyenough penetration of heat from that area
plate during heating while if itis a multiple portion rit
to »the inside.
75 can be supported >on a shallow (tray or inclined board.
time lfrom a multiple pack may be incorporated in the s
tinous layer '62 of high temperature resisting polythene
iilm bearing a repeat pattern of aluminium .gtoili63 pref
design of the metallic pattern of the heating hlm; Single
portion slabs may be formed in Va continuous package
with seals` between the slabs much añter the fashion of
the` arrangement above .described with reference to PIG
URE l0, but with the slabs taking the place of slices.
Also itis possible for the multiple package to contain
of the layer 62 equally on both `sides are secured. Us
Markings enabling single portions tojbe dispensed at a
erably of the expanded foil type as disclosed in said U,S.
patent applications and incorporatingLbusbars 64 across
the length of the layer 62. `On‘the other side of the
toil pattern 63v separate cross pieces 65 of :the same
.polythene ñlm extending beyondV the longitudinal edges '
ingfor convenience the term length Vfor dimensions inthe
ments dispense with the need for. measuring devices in 10 longitudinal direction of the layer 62, the width of the
layer is equal to the width of the slabs and the, length
serving` the heated food. >
of each cross piece 65 is equal to twice thesum of the
Desirably weighty terminal clips or a‘ synthetic rub
`length and thickness of the slab so that the crossV piece
ber pad with terminals or some other means of exerting
can just encircle the slab. In the width direction each
light'pressure on the top of the food pack during re-heat
cross piece extends beyond the edges of the layer 62
ing are provided so that lgood contact between the heat
slabs in rows across as Well as along it. These arrange
further inside. As soon as itis certain `that the liquid
by slightly more than the thickness of the slab so that
Vthese projecting parts’ can >completely cover the end of
a slab. The, distance .between the adjacent ledges of suc
_cessive' crosss pieces 65- is occupied 'by a bus bar64
or just' below the temperature iimityof the polythene
arms and if this is folded about a_ slab with the cross
meander p_aths which are at the top of the food package
. terminal areas 67 of the foil pattern, Ithe two areas being
is higher than the resistance of those at the :bottom which
is the present case are assumed to be parallelr to «the paths
Von top and which are more certain of good contact
insulated fnom one another by the polythene tape 62 as
shown‘in FIGURE 13. During packing and transport,
with the food before `and after it has liquiiied. Con
sequently the top part ofthe heating film will not
get so hot nor have suchy la high. heat dissipation as
30 for `connection to be made when heating is to be effected.
ing Yfilm and the foodis assured. Soon the boundary
layer of the food will liq-uify and ensure an even and good
heat transfer from the heating hlm to _the frozen -food
medium is present over the whole area of the- heating 20 just wide enough to provide two terminal areas. T11-us,
from centre to centre of two successive bus bars, the heat
film, the trate of heating can be increased to as much
ing film has the form of a cross with wide but short
as will keep this> liquid medium near the boiling point
piece outermost,v theA slab can be completely unwrapped'
iilm, Whichever
-is the lower. As a precaution the »foil~
pattern must be designed so that the resistance of those 25 leaving ’across the centre of the width two flaps 66 with
these'tlaps 66 Vcan be folded down fiat and then be raised
vTo facilitate separation of the successive packs the
layer 62 and metallic pattern 63 can have a row of
pe-nforations 68- along the mid-line .of each bus bar area.
` the bottom part.
'As shown in FIGURE 14 -the containers into which the
In some cases it may >only be convenient to'provide
the heating film. at the bottom of the package, yfor in 35 food is filled are preferably shallow metal trays 69
each with awide blade 71 temporarily 4fixed, -tofits side.
stance by laying the iilms in the containers into which
'I‘he film is laid in vthe trays and the relative dimensions
are suchthat the lines lof perforations 68 Acome into
the food can be :defroze'n and heated. Where the demand
register with the top edges of the blades 7,1 which shea-r
canUbe ~estimated accurately, time can be `allowed for
this, «but to increase the rate where“ there. is a, sudden 40 through the tape when the tray is lifted olf a conveyor
on which it is ‘carriedvpast a filling station and into a
demand an additional heating íilmfbent into a ‘form
'freezing tunnel. The surface of the't-ray is made very
~fwhich`is like that shown in yFIGURE Y9=but with fol-ds 4of
the hot `food is filled.
This limits the rate ‘at which
less depth can be inserted into thefoodstuff from above
as soon as the heating from below has softened. it suf
smooth,l to permit quick chilling by conduction 'when the
'tray is I‘taken through a metal channel held at very low
ticiently, the insertion lbeing preferably effected by the» 45 ,temperature )whereby the above mentioned frozen wall
aid A.of a'bar member made of wood with cross lblades
-which 'lit into the «folds of the film, the barmemjber
bein-g withdrawn as soon as the iilm‘shas been pressed
into position. r[his Iñurther film has a much larger area
s is produced.
It it is desired to deal with several files of lpackages
side by side on the same conveyor a multiple layer. can
be used comprising a series of parallel layers 62 each
" in contact with the food than 4that at the. bottom and it. 50
* with aV metal pattern. 63l as before While the cross` pieces
65 will extend over the -’whole series. The distance be
is well distributed through the bulk Aof theïfood so that
it enables the rate of heating to be speeded up very con
siderably. -Its terminal areas may be arranged simply to
tween adjacent layers -62‘will be a litle more than twice
the thickness of the slabs. ` The cross pieces may then
be perforated half way between adjacent layers to allow
overlie those of the> one at the bottom so that the two
` easy separation of the individual packages which each
are connected in parallel across the samev connections ‘ 55
`crosspiece holds` together like a'chain. s
If the food’ is to. be served on «traysas 1s convenient
particularly on vehicles such as trains, and in _aircraft
into direct` contact with the film, ythe film maybe ofyery
and also in camps and` places of entertainment, or again
thin flexibles and cheap wide‘we‘b` consisting of Aaluminum
foil patterned.v between two polythene films ofga quality‘ 60
1 -iin Vthe lhomewhen television is being- used, it is.l de
.’sira'ble that the food should be contained in a container
able to endure` a “high” temperature as that term is un
derstood Vin'connection'with polythene. The pattern in» having suflicient Vstiffness as supponting'fwhilethe food is
being »defrozen and reheated. Such 'container may be
principle comprises bus ba-rsfand` meander lines desirably
arranged’ to iit into a recess in ‘a tray, or the containers
‘ of ~«the expanded »foil type asin vsaid U.S,." Patent applica
may. be constituted bythe trays,- t-hough separate dis
’tions and the polythene boils `are arrangedtoj. leave the
f In a simple Yarrangement `in which the food is ñlled
terminal constituted by thefbusl bars bare and _the size
pensible containers are preferred.v f In @the latter case,
For a single Viile'îof packages the web is preferably
’ îrigidity. v At present aluminium foil pressings are often
>being such that the> film canïcompletely «enclose‘thelsla-b ' ‘ the heating film ‘can be embedded in the food and `easily
f'be hem'oved when the yfood Ais hot `either' by the con
and leavethe terminal areas of the two flaps standing up
Afrom the surface of ‘the slab so> Fthat.connection can; be s Vsumer or the person who serves him. If, _as is preferred,
made by. means of _sa device such as shown _in FIG-Il '70 a separate container is fusedßas this has to contain the
hot, often liquid food, Ait should have a high degree of
Y made up as shown in FIGURE l2k of a base layer as Wide
yused as individual food packs to .permit the heating of
the food `while in the pack on the yhotplate or inv an oven
as the ‘extent in this width direction of an individual or
multiple portion as may be desired, consisting of a con 75 and in'some cases to render it possible to serve the food
in theserpressings.Y One of the‘ldisadvantages of these
foil packs is that »they are' usually not rigid enough for
„packs are connected in parallel .within each lot.,v To- keep
food which is soft or liquid when hot. 'The cause of this
more) lots of food packs are connectedy in series.v lThe
the .food only warm the collective terminals of two_(or
-shortcoming is that they must be I'good heat conductors
heating films ofthe individual packages are designedA for
and not too thick .for reasons of cost and weight, and the CII Vthe aircraft’s supply .of 28 volts and have three terminal
provision of Vstitfening sections by pressing vthe foil has n
its limits.
areas and two* meander paths each so that theyV can
individually be connected in series vor parallel. >'Ilhe '
vswitching operations are controlled by conventional tem
perature sensitive [devices or by timing. The described
A higher degree of stiffness of theindividual food
"package whch has 1to1 contain the hot, often liquid, food
is desirable particularly if [the -food is heated and served 10 heating of .the packs their bulk boxes or trays and the
in it. The present invention provides for this and the
series-parallel switching enables a steep heating curve to
vgreater rigidity of the tray packs according sto the inven- e _be obtained and the food to be'kept warm without an .
tion yalsofacilitates their filling while they are Ion a con
oven >or hot box.
veyor line without the conveyor line itself needing any
special construction. Since these containers are >like shal
low boxes with often thin top and bottom covers'but
fairly rigid side Walls they can be held in any order on a
Ymeals to be servedr from deep frozen packs even on
The same scheme of serving heated food; on trays can
be applied in such spaces as on motor cars and coaches
Iconveyor belt merelyby exerting a slight ‘squeeze on
them through side rails or by soft elastic bands running
and in trains and also in hospitals, canteens, camps,
schools, factories and so forth. vFor all these purposes` l
‘between the rows «of containers. The heating film covers
`all Walls or »only top and bottom wall of -the container.
aswell as for aircraft, vthe vtray may >be provided- with
means for connection to the low voltage electricity sup
.The part of the heating nlm which subsequently forms
the {top cover »of the box is simply ‘folded back_over
front and/or back side walls, while, the container is
ing filled.>A To prevent food drippings from "soiling
other ¿sides of the pack `aiguard strip is fixe-d above
The >speed of heating enables hot "
ply an-d preferably also with one or more small lamps’V `
for indicating that the heating is “on” or 'for throwing soft
light on the tray. The latter is particularly desirabler
line lof these' other side walls. The` superiority of the ’
tray packs according to the invention over present day
foil packs is made possiblebecause 'the present inven
when eating in 'dark places (television watchers’ trays, ~
motorists’ trays, night meals in sick room, camps etc). ‘
The tray on which the .food is served may in this case
_be a permanent washable tray.
V'l'îhe’ food itself as above described‘is shipped .in or
tion‘provides a hot iilm surface which is the heat creat 30 served on dispensible, preferably decorated tray insets
‘ingv element itself and which can be in `close- contact
which incorporate heating films and means of connection, Y
.with the food. The container need Atherefore not be
>and are usually cheap pressings or mouldings in plastic v
o‘f -good heat conductivity throughout its thickness. Thus
or papier-mache. >Such insets may be used to-y heat
up order
food, to
it Iwarm
them at
a lowcost and
of production
replace plates.
it can be made from or incorporate laminated structural
`material of high stiffnessY but vlow v_veight."` This mate
jrial is generally sandwiched between two ñat films 4or
‘foils of which the inner` film maybe or may support '
the thin plastic heating film with they metallic pattern
are madetoo vflimsy kto be used instead of an larm
chair tray, but ,when -placed on a tray, or von a table
or a board they stand at least the rigours of oneß meal.
At this stage it will be convenient to describe further
the provision for the vsupply of ,current to the heating
film. This is :generally either lfrom the secondary wind# Á
andthe outer a` decorated paper, plastic' i’ilm or metallic
-foil. Between and to these thin, smooth skins a thick,
airy, buckling resisting ‘layer’ is'istuck consisting for
instance. of corrugated paper or cardboard, stiff plastic
ing »of a transformer completely insulated vfro`m` theV Y'
foam, honeycomb construction, papier-mache ora similar,
cheap vand lightweight stiifening filler. ‘There is no
>Il?àed to make fthe whole package from this laminated
mains lor from the battery of a car `or other vehicle. In ' >
Ysome cases it may be a stationary battery associated »with , '
harmless voltage not needing compliance with the elec
.tricity supply authorities’ regulations. For aircraftpack-_`
It is, for instance,fsuiiicient to` have it on -
the four low side Walls of shallow :box-«or tray-_like
food packs, thusv constituting a stiff ytrarne of the stressed
skintype, while the' large bottom area or top and bottom
,a charging device.
The voltage _supplied is` a low, '
"ages, it is usually 28 vol-ts but for lgeneral- use preferably f
iti's' the same as ilsjstand‘and in motor ‘cars which is ffl-2 '
areas are formed only by the heating film proper. 'Ihus
as'shcwn for example in'FlGURES l5 yand 16, the sides
volts in most cases.
Where temperature control ¿can A
be provided Afor eitherdby an automatic cut out-or by
"of the container are made of corrugated paper 91 having
the usualtbase paper 92 and another paper 9.3 >stretched
,over and ‘secured to the crests ofthe corru-gations so
kthat a composite material of thestressed skin type results
r>the attention of the user,
well as along the corrugations 'which are here set lper
high shortàtime overload isk sufficient ‘forheating upV his
-prefcooked food packs, canisters »or beverages, but,` for
, public eating places, vending machines or'iïor 'the> cooking'
times higher
for a voltage
very brief
shock at a two to four provision`
made“ by a time switch. lFor the private consumer a small
which is stiff in planes >normal to the `corjrugations as` 55
- transformer yof lange surface area capable of `sustaining a l
pendicular tothe top` and bofttom .of the containerl yThe
iheatin'g film `94. lvforms the top land bottom, with tapes 95
`carrying the terminal areas projecting sideways and this
facilities :described later a langer transformerais required.
cardboard box 97 recessed at’the bottom to protectrth'e
film andconten'ts. '.Suoh‘packs‘can' be sately stacked on
'oney another'and can >`pbeco'nnected in circuit when rso
¿the heating film iirst while »the foodfpack is on» a tray
îas'sem-bly containing the fooíd' 96` is 'contained in a usual’ 60
. In these installationsthe maximum-voltageislrsupplied Ito ` '
on which
of thisan charaoterare
ample supplyof
useful `on
a voltageof about 28 v-olts is often4 available.î The pack
Yages `may-«be supported in Ítrays or tray insets Yhaving
. moulded compartments serving as armchairtrayson which
Vthe `meal vis served.
For defreezing and heatingr up
` quickly a large quantity of individual‘fo'od packs sup
y fp'llied inV bulk boxes, «or «on stacks of tnays’or trayk inserts
the total contents of `,each bulk box or stack »of -trays
-is divided into two «lots and the terminals -of all food 75
held insidethe vending,` machine. The ,temperature
of the. paokageis sensed either by surfacethermometric
elements in the `‘tray or 'a olding device or by the heating Y
film itself. (This Iwillbe described‘illater.) `The sensing
actuates further controls,_such as reductionv of the voltage
to the value ttor merely keeping the food atthe tempera'
ture reachedY or desired, rejection of packages for faults `
>in heating film, switchingxon of Aa signal Vlamp for “ready,
take out” or‘igivin'g'v a warning. t The installation may>
have several channels to heatv several food packages
-simultaneously. Coin operated ven-ding »machines with ‘i
only'one channel can however have several terminals or
hot plates where food‘packs are .kept warm while slowly
emptied by fthe consumer.
cut-out vwill only permit the transformer to be switched
yon again after its temperature has dropped sufficiently
A transformer for use «by ¿helga-.neral public or in a
'restaurant is preferably designed to; be like a flat _box
which will be in a very short time in view of its lange
surface area. '_ Transformers used ina kitchen or the like
may have a tubular shapefor feature trays, pockets or
.other cooling surfaces which may be filled with or im
so that it can be used as warmplate and lends Aitself
`»to-artistic styling and use as- a centre piece on a dining
table. It is switched on the primary side and has lamps
to show that it is “on” It may have a switch to reduce
the 12 volts output to a “keep food warm” level.
The 12 volt terminals of they transformer may as shown
mersed in water, if there is an unforeseen overloading due
"to a party for example.
'Thefigure of 12 `volts is preferred as the nominal
in FIGURE 17areas
be in
to the.
the foil
of leaf
indicated 10 voltage of the transformer secondary. The tuansiorm'er
may be operated at this voltage for a long time and
at 73 of the heating film. Thesefleaf springs 72 are not
directly connected to the- transformer winding butv are Y at constant >temperature when it is used not to` heat up
`a single food‘dpack, but just to keep hot a number of
supported "by an insulator 74 say. of plastic or rubber
such packages or equivalent devices which have their heat- `
and arefslidable conveniently against the action of a
spring not shown. . When the terminals 73 have been 15 ing films connected in series. d
The provision of two terminals in the -foil pattern of
pushed between the leaf springs 72 continued further
-the >heating film can be varied. Three terminals can
_provide Ífor different heating rates or for different sup
attached to the insulator 7'4 carries the leaf springs ,Y plies, such as for the heating cycle described or_,for
further inward when they ride off insulating guides 76` 20 a fairly constantV 12 volt supply. They will enable -two
vparts `of the foil pattern to be connected in parallel for
`between metal terminals _77 which are' connected to the
heating-,up and inV series for keeping warm or quick
transformer secondary so that «the current is' now switched
thawing of `deep-frozen food using a connector as shown
on to the lheating film. When the terminals are pulled
out they' first switch the current .off by drawing the leaf A y'in FIGURE> 3 (for example.
The terminals yof the heating film are preferably only
springs on“v to the insulating guides v76 and thereafter the'
heating film terminals are pulled right out 'of the leaf - large bare areas within the foil pattern. They ar-e usually
folded over. 'Ilhe arrangement of the folds depends
. springs.
also ‘on the preferred way of inserting them into the sup
For `car`s or` other vehicles `or camping places, similar
terminals can be provided on a hinged tray’which can be Y v ply terminals. A fold turning the metal foil outside is pre
>fixed` to the dashboand lor4 hung rover the hack of the so ferred -for a “push-in” type of supply terminal as is
shown in FIGURE i17. However it is possible to arrange
front `seat .of a car Vof some similar suppont. Itis a self
the terminals of the film so thatl they are folded with
Gontainedv‘accessory with a fuse or out out and cable
the metal 'foil inside, that is »with the folded Ifoil areas
for connection' to the battery or to a socket on the dash
in `contac’twith eachother as shown in 'FIGURE 18. Here
board. Alternatively terminals with connections to the
battery may be built in.
` 1 ‘
35 `the metallic foil pattern 78 ison the inside of a paper
container `79. There may be additional layers as prev
`»In @order not to complicate l.the description it has
:mostly `been confined so far to heating films operating ' îiously `described herein.` 'I'he metal pattern includes
inward movement whichV may Ibe transmitted directly
from the food package 'vor by hand through a rod 75
' terminals 81 which have their extreme ends foldedup
onïa fixed’ voltage, say-12 volts, supplied'Í from a trans
>formerior battery, and to initial'heat shocks or sub- i
and secured to a paper strip -82 which continues below
.by suitable switching or other usual devices on «the supply
side. The present invention includes the automatic pro
' terminals are carried up‘t-hroulgh the top of the bag `‘79
sequent reductions in venengy supply'being provided for .4.0` the terminals.r =By~ pulling out the Vterminal` strip the
vision ofA an advantageous heating cycle particularly inl
4.conjunction with the smalltrans‘formers of largeV surface
yarea alreadyreferred to. A further object of this feature
kis the reduction of the cost ofv these transformers and
,but still remain insulated .by the paper strip. Connec
tion can then be madev to them for example by the device
of FIGUREZ or FIGURE 3. FIGURE 18 has other
features which are-described below.
» *d
The design of the heating film, nominally made for
their’useasfhot plates or-the'like. >'I'hese transformers
»say 12 volts-should take into consideration the heating y
, higher than ‘the l12 volt nominal and arranged to be "»very
stitntes a fuse .which will blow at a certain current. An
- other w‘ay toprovide a fuse is to connect a tiny link in
Vcycle described. This is vvparticularly necessary when a
are constructed as in said’U.S. patent application Serial
lfuse is provided in Ithe circuit, for instance in the foil pat
No. 752,384 in such a way that both theinonnnd'the
tern ofthe heating film itself. Such provision is made by
windings have a very lange surface exposed and also
that both core andwwindings have a very small cross 50 narrowing the width of the continuous line at a conven
ient place ’in the film so that this part of the pattern con
section. On “no Aload” the secondaryrvoltage is much
near, but still below,r the minimum to which local regula
tions" apply and `below the voltage which is> ‘safe to
the'pattern which consists of two foil pieces under tension
The tensionsmaytbe that
~ touch-«whichever the lower in case the two figures are 55 held together with la solder.
which is pre-sentinany event in such an `article as a filled
l held to differ.
A consequence ‘of the extraordinary saving in weight by
. bag of flexible heating film or by development of vapour
Vpressure during heating of the foodstuff. If the solder is
a low melting solder the fuse also breaks on being over
is «the fact that the transformer will get hot or hotter
thanlthe food packageabout as quickly as the heat 60 heated by any means.
ing film ¿fed by it. --Its output voltage will consequently
wThe use offlow «melting point solder as a lfusible ele
' Vfall considerably while theiwattage available gets down
' ment only one of a'variety of means of guardingagainst
l' the reduction .of the cross section of the active materials
as the square’of the voltage. At the same time the ohmic
>undesirable temperature. rise proposed by the invention.
resistance'of the heating ìfilm rises as`it heats up and
‘l thus fur-therV reducesfthefcurr'ent intake. Consequently
a heating cycle results which is much different lfrom that
available from a `fairly constant voltage supply. An
'i initial heat shock is supplied automatically and the heat-v
` ing-up is speeded considerably. ,
The “10st” energy goes mainly into heating the trans
" 'former and this is made use of in the hotplate arrange
“ ment already mentioned. The large surface area of the
' transformer 'as well as a thermostat and/for cut-out in
‘ the primary circuit of the transformer prevent its tem-V
perature from rising `beyond predetermined limits. The
In the following examples »alternative means to achieve
65 Va similar protection are given.
‘d v In' the description of the three layer structure of thev
`heatmg film consisting of> unpatterned foil-plastic film
foil pattern, it was-mentioned >that this materialy enables
.other effects as lwell to be obtained.
One such effect is
to actuate ya cut-out if a hot spot occurs or the overall
>temperature rises unduly. 4The plastic film separating
the two metallic layers is not only thin but is of a sub
stance chosen for- its `melting-point at the critical tem
perature at which the cut out is to be actuated. The un- Y
patterned foil is'earthed. =lt is thick enough and of sufli- '
_for `all practical cooking processes have already been `de
scribed earlier. The following additional features of the
ciently. high melting point to be unaffected by the “short”
arising when the plastic film` melts yat any point.
It is '
invention deal with a number of, varieties of foods and
preferably an aluminum -foil of about .0102” thickness.
their cooking.
The earthing current is used to release a cut-out or blow
_ .'
When the package contains liquid food or food heldin
,a fuse anywhere inthe circuit, but it is preferred to have
a liquid the terminals of the heating lilm are made acces
a fusible element in the heating iilrn itself by arranging
sible only when a steam escape is open. This precaution _
for the earthing current to break the path of'the current
in the -foil pattern. For that purpose a fusible element
is provided in the foil circuit near a terminal, for instance
the low melting solder type referred to previously oran
other temperature yactuated “explosive means” of rupture `
of> »that circuit. A line meander pattern between the earth
is to be observed on most packages.-v Heating films in the
form of immersion heaters or of bags inside ia tin or >box>
have their terminals secured to the wall of the tinor box
which must be‘opened before connection can be made to
them. » Plastic film packs or the' like may have a holeV held
closed or covered bythe folded terminals or‘a> strip con
terminal fand the unpatterned foil is arranged opposite
-nected with the terminals; when the tcrmi'nalsare pulled
and as close as possible to this rupture element so that
the earthcurrent can actuate it in case of a short by heat
Aout or pushed in for switching the current on ’the hole Vis
uncovered. Thus as shown in FIGURE’ 18 there is'an
conduction from the meander pattern.
i ,
aperture S3 in the bag 79` and pattern 78 which> is normal
The principle illustrated iby the above example can be
-ly covered by a seal 84 to which the paper strip 82 is -at
«i carried into eifect in several other forms.
Vtached. Breaking of the seal opens the aperture 83 and
` The low melting solder can be replaced by a conductive 20 also releases the paperv stripenabling the terminal-s to be
adhesive consisting for instance of 'graugihiteV or metal
pulled out. The lower end of the paper strip maybe
powder ini a binder softening atthe critical temperature;
narrower than the upper part -which is to insulate the ter- '
minals 81. >Alternatively as in FIGURE l f_or‘example`
The “explosive mea-11s” of rupture can be‘the use of steam
rising from a heated capsule enclosing ia few drops of `
the terminals may be sealed in and breakingof the _seal
water, it can Ybe a small piece of steel magnetically oper
creates or uncovers an opening in the package.
ated by a» spiral coil element instead of heat actuated. "
l When the contents of the package isa dry foodr or is a
The cut-out provides only one'type of temperature and
concentrate, which is dry or viscous, which bastov ybe
stored in this condition` but mixedl later with Ywater "or
V“safety” regulation. The temperature of the foodpacked
sauce or other liquid orto be boiled in such a liquid, the "
Acan ‘be sensed `and the supply regulated accordingly by
incorporating thermometric elements. They can be made
dry food or concentrate should not be heated as such by
the ñlm. `The invention provides two schemes-for such
a separate part or layer of the heating film or >the resist
ance change of a standardfoil pattern can be directly
sensed _by a device on the supply side. The accuracy ob
cases. `Thus the requisite quantity'of water or_ other
üiquid can be sealed in la plastic ibag which is »part of the
tainable with the aluminum pattern-while insufficient
in standardmeasuring devices-is generally suiiicient for-
heating yfilm or" attached to it, for vinstance by the film
being wound round thebag. The seal of the bag lgives
way whenV a_ certain temperature ist reached forfiiistance
the purpose here in View. '
‘ ‘
boiling point, and the liquid pours on to the dry foodstuff
. or concentrate. Boiling can thusproceed.; Inthe _second
Üfoil is preferred, but the invention is not restricted to
»scheme the dry material or concentrate `is packed 1n a
'this metal. Tinfoil is another possible choice, and if other
metals or alloys including for instance titanium becomes 40 _heating iilm which is very porous, for> instance ina per- t
forated bag, the pores or perforation offthis package being
available as thin layers or foils at a price making their
, sealedl by anediblesubstance soluble in hotwater, such as '
-ilse economically feasible,- they may also come into con
. gelatine. If the foil pattern is sufiiciently cohereritto b_e
sideration, particularlyfor the higher temperature heat
- Here it might be emphasizedthat »the use of aluminum ` Y
~ing films.
easily removable from the hot food as a whole it rnay_'b_eV
used ldirectly on a gelatine til-m withoutanother (plastic)
The inventionincludes the application of the dispensa
ñlm support to enclose the liquid or powdered concentrate;
` ble heating films to egg containers and cups.
. Several such bags, each for an individual portion, may for
The heating iilm for egg boiling may be` vacuum formed
into a shape enclosing the egg. Y It is crimped to accom-vr
i instance be packed in a box or tin. _ For use each package
is placed in a dish with the requisite amount of water and ‘ -
`rriodate Variations in the size `and shape of an egg or of
ythe egg cup or egg crate to which it may be stuck. 'The
‘ crimping also facilitates the insertion of the egg and per
¿switched on. Mixing Voccurs 'as soon as the hot liquidhas
dissolved the `gelatine film.
'mits clamping of the lfoil terminals by spring contacts ,
V'such as those of FIGURE >2 or 3 without pressing theV
egg. When a dispensible egg crate is used it may beof
and to various hot sweets.
Yet a further possibility is application to the steaming
of food. Thus 4by making the bag’in which the food.
stored liquid proof `and enclosing a liquid in a can or foil
container and providing a steam escape (in it, the food can
' ‘
In the above example the dispensible food .package
that is the egg crate-has been used n_ot only as an eating
be .steamed by the rpassage of steam through the foodÍto a
final steam escape from the package which is opened prior
applicanœ but also as a‘cooking means. This principle
k vvaried in shape and styling„in heating energy and tem- .
65 to or in switching on the current.k yAnother arrangement
_for steaming is` that shown in FIGURE‘19.; This is liii-
- perature can ber applied to other foodstuffs aswell and be
used for cooking `as well as for heating up’ 'or keeping `the
heated V_food warm. Among other advantages it dispenses
’ with 'or reduces washing-rupi.
present invention includes the use of the heating film for
cooln'ng. This is however not only a question of tempera
may be extended to beverages such as coffee'or chocolate ,
The permanent contacts may be on a flexible cable or
tape and the ‘connector may also incorporate an eggtimer,
’ s-witc‘h„.fuse, etc. The heating ñlm may also be stuck on
Theegg boiling example has also illustrated that the
other >similar materials as soluble substances to__~fill_',_the
pores or perforations of theheating film pack the method
a coherent unit for a number of ’eggs `as in present use.
food‘in a-concentrated sauce. Using sugar, chocolatev or
decorated papier mache or cardboard and styled las a
single egg cup Wlhile the other half of the crate may be
to a standard type of egg crate.
Using a fairly strong heating film this scheme may be
employed ’to provide sausage type Askins enclosing solid
tended more particularly for the defree'zing and thenV
steaming of frozen rawV food such as vegetables._ The food
. '85 is enclosed in a bag S6 which incorporates the heating
film andis -held in a separate> wrapper at least the 'bottoni
- of which is -porous as at 87. The heating lilm 1s designed .
so that i-t develops most heat at the bottom ofthe bag.
The lower part of the bag has at least one concertina Vfold
~ . ture and wattage required; heating film“ structures and
as at 88 and contains the necessary water or other` liquid.
‘ supply sources for all temperatures and energies necessary 75 This liquid can be in the form of an ice cube inserted dur
. ing packing or liquid'can be" added by the user when'he
opens the upper end' of 'the b'ág'to gain access tothe termi
na1s89`;` ln the use the bag" isysuspended by the terminals 89 ina clip >coiin'e‘ctor such" as 'that shown inl FIGURE
2 or 3`. The bag vat íirst remains folded until defreezing is
' completed and the liquid is heated up,`but when the pres
isolating at least part of the foodstuff and it permanently
loses itsf permeability as a' result of one operation in
volved: in- heating> and removal vof the foodstuff.
j 4.1» A rood-ï package -asset forth in claim 1, in which the
heating' tilin has smallopenings therein which are closed
by solid edible materials Iwhich are cleared trom said
openings as .a result or the heating of the Íoodstuif.
5. A rood package as set lforth in claim l, in which the
terminal areas inside the container are .accessible by
ing on the proportions, the rate of boiling and such like
conditions. Only a small steam escape is provided and 10 providingan opening in the container which constitutes a
sure rises the fold 38 unfolds and room is left at the top
for steam. If need be, there can be several folds depend
there will be a constant reilux of condensed steam back
-6. A food package -as set Iforth in claim l, in which the
package is provided with la passageway with said heat
ing vii-lin positioned at least partly in the passageway
the necessary steam space.
The arrangement above described for dealing with dry 15 through which the foodstuff is removed from the pack
age when heated.
foods and for steaming and various other schemes are
7. A -food package as set ‘forth in> claim 1, in which said
arranged so that necessary changes in the disposition of
into the -body of liquid being boiled. Instead of a bag, a
box may be used but this must be large enough to provide
the parts or in the opening and vents are effected `auto
heating lilm constitutes a plurality of substantially paral
lel layers within the container. .
rn’atically before vaccess to the terminals is obtained. ySuch
provisions are preferable t0 means which require attention 20 V8. A food package as set ‘forth in claim 1, in which
said heating ñlm constitutes a plurality of substantially
and/ or extra tools, although the present invention covers
parallel layers within the container, :at least some of said
them as well. Such tools are for instance pins to be in
layers being provided with tear-olf zones and with ter
serted, Stoppers to be removed. etc.
In frying or stewing packs there may be a partition
minal areas so that they can be connected to an electric
separating the .fat or sauce Ifrom the other tfood, and»> 25 supply .after being separated :at the tear-off zones.
9. A food package as set forth in claim 1, in which
the heating nlm maybe part of the partition or immersed
said heating lilm constitutes a plurality of substantially
in the liquid only. :In case of frozen Áfood the partition
parallel layers
the container, and -at least some
may be an edible fil-m, :but generally this is not the case.
Itis `.torn or pertorated either simultaneously with theV
¿of said layers are provided with respective terminal areas,
'opening of the steam «escape by the action of getting 30 and the package including corresponding contacts which
access to the terminals or later ‘by the heat or vapour " are held pressed .against said respective terminal areas.
10. A .food package as set forth in claim l, in which
pressure of the heated liquid. This rupture may be used
for automatically timing the processv by designing the ' said heating iilm constitutes a plurality of substantially
parallel layers Within the container disposed so that at
package so .that the circuit Vin a part of the lfoil pattern
is also ruptured and the energy input is reduced to a 35 least some of the layers dissipate heat to the foodstuff at a
different rate lfrom the others.
desired level.
11. A »food package as set ‘forth in claim 1, in which
For baking, roasting or grilling thin food slices a
said terminal areas .are folded «over and extend‘over sub
high temperature heating hlm may be used which is
stantially the ent-ire length of two opposite edges of the
spaced ltrom the «food-stuit .and trom the insulated con
tainer Wall by expanded metal spacers on both sides of 40 heating iilm.
12. A lfood package as -set forth in claim 1, in which
the food
slices. -For lower temperature work the attach
said terminal areas are lfolded to llie within the package,
ment would be carried out by sticking or other tixing
:and in which means are provided .attached to said ter
`rninal >areas and accessible from outside the package
The heating iilms and 'food packages themselves often
‘form eating appliances, and this form o-f the food pack 45 whereby said terminal .areas are pulled out when con
age is proposed for use in camping, for travelling, for
nection to an electric supply is to be made.
the army and wherever provision for crockery `and con
`13. A `food package as set forth in claim 1, in- which
said container also includes a permeable Wall separating
ventional tableware is inconvenient.
it into at least two compartments with the tfoodstuif »con
I claim:
1. A food package comprising a Y»dispensable container 50 taine-d in at least one of said compartments, and in which
an edible medium is provided which becomes iluid when
having outer walls yand with -a foodstuff therein, a sep
arate dispensable electrical heating iilm -at least having
hot contained in the other of said compartments, the
heating lilm bein-g adapted to heat said medium so that
the heated medium passes through said permeable wall
insulating layer between the iilm and the outer Wall of 55 and heats the foodstuff in its compartment.
. the major part of its suface within the outer walls of
the container and at least one electrically yand thermally
the container, said heating ñlm including terminal areas
accessible without removing the foodstuff trom the con
tainer, ,and said heating lìlm :also including an electrical
conductive pattern of metal toi-1 providing >at least one
meander path between said terminal areas »and presenting
a value of resistance between said terminal areas which
when connected by said terminal areas to la low voltage
source heat is developed at a rate adequate to heat the
foodstuff in the container, said iilm being
and of
large-heat transferring surface area and positioned in the 65
container so that its surface temperature «during the heat
. ing period does not reach a value -Which would damage
2. A ‘food package as set forth in claim 1, in which the 70
heating Ifilm is spaced Áfrom the container wall and has
the foodstuff on both sides so that both surfaces of the
14. A ,food package as set yforth in claim l, in which
said container is flexible :and hermetically sealed, the
pressure within the container Ibeing sub-'atmospheric so
that the heating iilm is held in contact rwith the Ifood
stuif by the .atmospheric pressure acting on the container,
-and said terminal areas being accessible Without breaking
the hermetic seal.
References Cited in the tile of this patent
Fletcher ____________ __ Mar. V18, @1941
Neff __________ __'_____.. Jan. 5, 1943
Aft ____________ .__‘_____ June 28, 1949
Bailey ______________ __ Sept. 19, 1950
Hound ______________ __ Not/.16, 195,1 `
l2,578,3’ 14
Meunch _____________ .__ Dec. 11, 11951
heating iilm dissipate heat to the foodstuif.'
Vogt ______________ _’__ Mar. 9, .-1954
3. A food package `as set »forth in claim 1, .in which the
heating lilm before heating forms .an impermeable Wall 75
(Other references on following page)
2,724,674 l
Eisler ______________ __ May 29, 1956r
'Cox ...... __'. _______ __. June 29, -1954
Bliley ..... __` ________ _, OctJ, 23, `195‘6 ‘
Phair @t a1. __________ __ Sept. 7, 1954
, 2,682,596
.Pmítikìn-__"__'_ _______ _.. Nov, 22, v`13955
lEis-1er __________ _.'___r__« Mayr. 6,. ç1956
Talbot et lad. __________ __ 'Feb'. 12, 1957
Reuman _; _______ _;.___v_ May 13, 1958
McLean --2 __________ __, July 22, 1958
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