Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
`: 106~51
BACKÇROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a method and apparatus
; for the automatic filling and packaging of foodstuffs under
aseptic or low-bacterial count conditions, which foodstuffs
have been previously dis;nfected orsterilized and then passed
to a filling and packing plant. The packaging material is
disinfected by means of high-intensity ultraviolet radiation.
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Description of the Prior Art:
Automatic techniques for the aseptic filling and packag-
ing of foodstuffs is being used on an increasingly wide scale.
To date, the aseptic packing of pre-sterilized (uperised) milk
in packages made of a composite paper material has gained
particularly wide acceptance. (The uperisation of milk is
described, for example, in Industr. alim, agr. 1956, p. 635 -
640.) The packages are predominantly tetrahedral or rectangu-
lar in shape and are made up by applying transverse seals to
` a tube of packaging material formed from a strip of packaging
material drawn from a roll (cf. TARA 271, February 1972, page
104).
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Generally, '~aseptic packing" can also be defined as
the placing of a cold, commercially sterile foodstuff into
a pre-sterilized container under sterile conditions. The
container, if provided with an appropriately pre-sterilized
lid is enclosed in a sterïle envïronment so as to produce
an airtight package (Food Technology, August 1972, page 70).
-; Another packaging technique which has become very
~` important is t~e packaging of low-bacteria count foodstuffs
in, for example, deep-drawn prefabricated beakers which are
then heat-sealed with refined aluminum foil. Common applica-
tions include the packing of yoghurt, soured milk, cream,
and so on. An essential feature of the known techniques is
that nosterilization occurs of the contents by heating in the -
already sealed package, as is the case with canning and pre-
serving techniques. The tedious heating process is thus elimin-
ated without having to take into account deleterious changes
in the contents of the packaged foodstuff such as flavour or
composition. Furthermore, the packages can be made of materials, ;
in particular plastics, which cannot withstand elevated temper-
atures. A particularly critical aspect of the known techniques
i is that the packaging material must be so free from bacteria
; as to provide the greatest possible safeguard against infection
of the previously sterilized or disinfected contents by bac-
teria, moulds and/or yeasts which could cause spoiling.
Here it is pertinent to note that in the case of uperised
milk, for example, a single bacterium in the package can cause
the milk to spoil.
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- A large variety of methods and apparatus for disin-
fecting packaging materials have been proposed and applied
in practice. These are reviewed, for example, în "~erpackungs-
Rundschau" 7 (1970) pages 51 - 54. Other references in the
literature include Food Technology, September 1973, page 49
(disinfection with alcohol and ultraviolet radiation) and
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Food Technology, August 1972, pages 70 - 74 (e.g. disinfection
with wet and high-temperature steam, the so-called "James Dole
process"). In particular, a method is known as described in
"Verpackungs-Rundschau" 7 (1970) pages 52 - 53, whereby packag-
ing material is disinfected by means of high-intensity ultra-
violet radiation. It is disclosed that the ultraviolet wave-
length of 254 nm has proven especially effective against all
relevant micro-organisms. However, micro-organisms differ
with regard to their sensitivity to ultraviolet radiation.
Thorough destruction of all micro-organisms present can be
~, ! achieved only with a very heavy radiation dose. on page 54,
op. cit., it is disclosed that the high destruction rates
are obtained only when the distance of the foodstuff from
the light source is very short. Further, it is not known
whether or how packages can be sterilized to the required
degree and at a sufficient speed as required in filling plant
~; operations.
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' A need therefore continues to exist for a method
:; 25 of packaging foodstuffs under sterile conditions by exposure
of the packaging material to a sterilizing light source
such that the degree of sterilization is swift and complete.
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S I~MMARY OF THE IN VENTI ON
` Accordingly, one object of the ~resent invention is
to provide a method by which packaging material can be dis-
infected on an industrial scale by means of ultraviolet radiat- -
S ion on filling and packing machines. ~ -
In one aspect the invention pertains to a method for - ~
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automatically packaging previously disinfected or sterilized
foodstuffs under antiseptic to low-bacterial count conditions.
The improved method comprises providing a packaging material,
and producing a predetermined ultraviolet radiation of sufficient
intensity to disinfect the packaging material. The step of
producing the radiation includes forming a mercury discharge
with a current density of more than one ampere per square centi-
meter at a pressure between 0.005 and 0.5 Torr, generating with
lS the discharge ultraviolet radiation in which the spectral rad- ;
iation intensity of the 253.7 nm line reaching the packaging
material is set to at least 0.05 Watts per square centimeter,
and destroying harmful bacteria on the packaging material ex-
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clusively by exposure of the packing material to the predetermined
ultraviolet radiation for an interval of from one to sixty
seconds.
Another aspect of the invention relates to an apparatus
! for automatically filling and packaging foodstuffs under aseptic
to low-bacterial count conditions, the foodstuffs having been
previously disinfected or sterilized. The apparatus includes
at least two mercury discharge tubes having a high-current,
~;; low-pressure mercury discharge with a current density of
, more than 1 A/cm2 and a mercury pressure of 5 x 10 3 to
. 5 x 10 1 Torr. The discharge tubes have discharge paths and --
the material surrounding the discharge paths within the dis- -
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charge tubes is transparent at least for the wavelength 253.7
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nm. Means are provided for passing a packaging material
to a station for receiving the foodstuffs and means are
provided for applying the spectral radiation intensity of
the 253.7 nm line of the ultraviolet radiation of the discharge
tubes on the packaging material with at least 0.05 W/cm2.
The discharge tubes are arranged one behind the other relative
to the direction of movement of the packaging material toward
the station and extend across the entire width of the packaging
; material. The discharge paths of the discharge tubes lie
lO in a plane parallel to the plane of the irradiated portion
of the packaging material. The radiation applying
means includes a reflector formed of an upper part disposed
above and parallel to the plane of the discharge paths.
Two side parts of the reflector extend from the upper part
to a line of the packaging material at those points at which
the ultraviolet radiation begins and ends, respectively. The
reflectivity of the reflector is better than 0.75 and the
two side parts are approximately perpendicular to the upper j'
part, wherein the ratio of the vertical distance between the - -
; 20 plane of the discharge paths and the packaging material to
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the distance between two adjacent discharge paths is at
least 0.5. The shortest distance between the two outer
discharge paths and the adjacent side parts is smaller than
twice the diameter of one discharge tube and the shortest
distance between the side parts and the packaging material is
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less than lO nm.
BRIEF DESCRIPTION OF THE DRAWIN('.S ~ :
A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
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FIGURE 1 sho~s a filling and packaging plant fox the
packaging of port~on~sized pacRages~ of low~bacter~a content; ~:
FIGURE 2 shows a filling and packing plant for the -~
aseptic packaging of a pre-sterilized liquid, such as uperised
milk;
FIGURE 3 shows in schematic form the arrangement of a
folded discharge tube over a feed line of packaging material;
FIGURE 4 illustrates discharge tubes in a reflector
, over a feed line of packaging material; and
. 10 FI~URE 5 is a diagram showing the destruction rate K
of various relevant micro-organisms in relation to the exposure
time t of the packaging material to ultraviolet radiation, at
a radiation intensity of 0.3 W/cm2.
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DETAILED DESCRIpTION OF THE PREFERRED EMBODIMENTS
A mercury discharge of the kind described above
; produces ultraviolet radiation having a spectrum which causes
: destruction of the relevant micro-organisms in a surprisingly .
effective manner. Although control of the radiation intensity
is aimed basically at the 253.7 nm line, it is preferred that -
the ultraviolet spectrum should also contain significant
proportions of the 184.9 and 194.2 nm lines. If the stated
minimum radiation intensity and minimum time of exposure of
the packaging materials to the ultraviolet are observed, the `:;
packaging material is surprisingly disinfected to an extent ;~
.~ 25 which, in contrast to previous general expectations, makes
disinfection by means of ultraviolet radiation practical on an
industrial scale.
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In F~GURE 1 the packing ,m,ateri~al 1 in the fo~m
of preshaped conta~ners, e.g. deep-d~a~n beakers, ~s taken
from a s-tack and conveyed ~n d~rect~on M. The packing
material 1 is first exposed to infrared rad~ation IR and
then to ultraviolet radiation W from the discharge paths
5 of discharge tubes 4 located in a housing 6, 7, 8 which
,~ acts as a reflector. The reflector housing containing the
-' UY radiation source is also termed the W channel. Under
the filling station F the portion-size beakers are filled
, 10 with the previously disinfected contents, e.g. yoghurt or
, cream. Packing material 2, a sealing foil of aluminum
, 50 - lOO~m thick, for example, running off a roll Rl, is
first, like material 1, passed through an infrared channel '
and an ultraviolet channel, and is then fed via a guide '
roll to the stamping and sealing station 10. Here, lids
,~i are stamped from the sealing foil and attached to the filled
beakers by heat to give an air-tight seal. The completed '
~, portion-size packs then leave the machine on the right. ,-'
" ' To keep the plant generally aseptic, sterile air ~'
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' could also be introduced horizontally from the side. ,~
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In FIGURE 2, packing material 3, e.g. a laminated ~
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paper composite with plastic-coated aluminium foil, runs
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from roll R2 in direction M into a UV channel comprising
two reflector housings 6, 7, 8 with discharge tubes 4
arranged on either side of the packing material 3. The packing
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material 3 is then shaped in a device (not shown) into a tube
T, transversely sealed at Q, and then ejected as a finished
package P. The liquid contents of the package are fed into
the packaging material through conduit F, a pipe which is
introduced into the shaped tube. As in FIGURE 1, the apparatus
of FIGURE 2 can also be provided with an IR channel before the
UV channel.
The discharge tubes 4 are provided so that the packaging
material 1, 2, 3, in whatever form it occurs, is exposed to
radiation of the correct intensity and with the wavelength
spectrum specified by the invention. The tubes are conveniently
of the form described in United States Patent No. 3,971,968,
granted July 27, 1976, to which reference is made as appropriate.
, The desired ultraviolet radiation is emitted from the part
of the discharge tube 4 denoted "discharge path 5".
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, FIGURE 3 shows a folded discharge tube 4 over a feed
' line of packing material 1, 2, 3. Each part of the discharge
tube 4 extending over the full width of the packing material
; 1, 2, 3 is to be considered as a discharge path 5, and thus
the folded discharge tube 4 shown has four discharge paths
5 arranged in series and extending over the whole width of
the packing material 1, 2, 3.
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The procedure of disinfection by means of ultravioiet
radiation is as follows:
The dis~harge tubes 4 are operated for example at 10 ~/cm~
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with a mercury~ tem~erature of 72C, corresponding to about
6 x 10 2 Torr. In th~s manne~, intense ultra~olet radiation
of ~ave-length 253.7 nm is generated w~th an efficiency of
more than 20~, whereby the spectrum also includes substantial
~ 5 proportions of the lines 184.9 and lq4.2 nm. At these wave-
; lengths of radiation, as will be described more fully below,
all sporogenetic and non-sporogenetic bacteria are killed at
the required rate within a few seconds, while mould spores,
particularly aspergillus niger, are more resistant.
l 10 It is often not necessary to kill all of the mould
; spores present in a foodstuff, as the spores are neither
toxic nor pathogenic and, in sealed packages of milk for
example, are also virtually incapable of multiplying. If
destruction of the mould spores is desirable, however, it - -~
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is achieved in accordance with another important aspect of
the invention by heating the packing material 1, 2, 3, to
more than 60C, e.g. to 80 - 90C in the sterile part of
the filling and packing plant. It is known that mould spores
are destroyed completely at such temperature within a few
i 20 seconds.
The packaging material 1, 2 is heated as shown in
FIGURE 1 by means of infrared radiation IR before the
packing material is subjected to the ultraviolet radiation
UV. The infrared radiation section can be kept short -
because the temperature created by the infrared radiation
is retained in the UV channel owing to the dissipation of
'~ W power, and even rises a few degrees, and thus the packing
material is held for a sufficiently long time at the temperature
necessary to kill the mould spores.
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The dosage of UV radiation tested in practice (cf. DIN 5031 Sheet 1,
August 1970, para. 7) on packing materials is 1.5 Ws/cm2, although the
measurement relates only to the 253.7 nm line. Taking into account the
technically and industrially reasonable feed rates for the packag~ng
material, irradiation of the packaging m~terial with an intensity on the 253.7
nm line of 0.3 W/cm, and exposure of the material to the UV radiation of
5 seconds, has proven advantageous.
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In order that the discharge tubes 4 emit nct only 253.7 nm radiation,
but also 183.9 nm and 194.2 nm radiation, the discharge paths 5 are provided
¦ with substances which do not absorb these lines. Such a substance is
, high-purity quartz, e . g . synthetic quartz . This not only makes available
the ultraviolet spectrum important for killing micro-organisms, but also
causes ozone 03 to be generated in considerable quantities from atmospheric
oxygen. The presence of O3 has an added sterilizing effect on the packag-
ing material and the surroundings.
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It is very important that the feed line of the packaging material,
regardless of its form (containers, flat strip), be irradiated uniformly
and homogeneously. Achieving this has hitherto presented a serious
practical problem. But here, too, the invention offers an effective .
~0 remedy. Homogeneous irradiation transverse to the direction of movement
~, . M of the packing material 1, 2, 3 is obtained by arranging the straight
ection. the dtschttrge tube- 4, i.e. the tiischar_e paths 5, so thttt
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; they extend across the ~ull ~dth of th~ l~ne of ~ackaging
mater~al and l~e in ser~es ~n a plane E parallel to the plane
; of the irradiated line of packaging ~Fig. 4). Arranging the ~ ; -discharge paths 5 in series transverse to direction M has
, 5 the further adYantage that any unequal ageing of the dis-
; charge paths is compensated more effectively. Homogeneous
~ distribution over a defined distance in the direction of
- movement M is achieved by means of a reflector. This is
highly reflective for the short-wave ultraviolet and consists
of highly polished anodised aluminium, for example. Its
reflectivity is better than 0.75. The reflector comprises
an upper portion 6 and two side pieces 7, 8. These extend
from the upper portion 6, preferably vertically, towards the
feed line of packing material 1, 2, 3. Side piece 7 is at
the entrance of the UV channel, and side piece 8 at the exit.
This arrangement of the reflector not only creates
a defined radiation section, but also produces highly
homogeneous and diffuse radiation on the packaging material
in a manner not immediately predictable. One reason for
this at first surprising result is that the high-current low-
pressure mercury discharge as operated with the parameters
of the invention is optically narrow, i.e. the radiation ~-
comes uniformly from the whole volume of the discharge, and -
no absorption takes place. The optical laws for point, line
and area sources cannot, therefore, be applied to a reflector
of this kind.
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The d~sch~rge path~ 5 and the reflector 6, 7, 8
are advantageousl~ arranged ~n a hou~ng hav~ng openings to
the outside which are as small as possible and form a seal
as tight as possible at the entry and exit of the packaging
material 1, 2, 3. This housing screens the surroundings
from the W radiation and also prevents dissipation of the -
ozone produced by the radiation, particularly in the direction
of the filling station F. The housing can also consist of
the reflector itself 6, 7, 8, as shown in FIGURES 1 and 2.
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; 10 The housing or the reflector can be equipped with
an exhaust device 9 for the ozone formed. The electrode
spaces of the discharge tubes 4 are conveniently outside
the housing or reflector, located side by side in a special
lamp enclosure. The reflector must be of a suitable shape
and size so that the UV radiation at the packaging material
is as homogeneous and diffuse as possible. The method of
determining such dimension is described with reference to
FIGURE 4:
In order that the radiation intensity I on the
packaging material fluctuates by less than 10~, i.e.~
= 10%, the condition: a/d > 0.5 must be observed when
using a reflector of reflectivity R ~ 0.75. Here, a is the
; vertical distance between the axis of a discharge path 5 and
the packing material l, 2, 3. The vertical distance c of
plane E in which the discharge paths lie is itself of
secondary importance, but it should be as small as possible,
and in particular smaller than the distance
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d between the axes of two discharge paths. Edge effects can then be more ;
effectively avoided.
Also to minimize edge effects, e should be as small as possible,
; and b as large as possible. Here, e is the shortest distance between the
axis of the outermost discharge path 5' and the neighbouring side piece 7,
8, and b is the length of a side piece 7, 8 from plane E towards the ~ -
packaging material. If, in particular, e ~ 1.5 D (where D = diameter
of discharge path 5) and a-b = f < lOmm, then ~I/I C 10% over the
entire line of packaging material 1, 2, 3 from inlet side piece 7 to outlet
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lû side piece 8.
; ~ Homogeneous and diffuse ultraviolet radiation as described
above have the following advantages, among others:
The interior of preformed containers is uniformly irradiated, in
particular without shadows. Surprisingly, the interior of beakers 3 cm
deep and 6 cm wide is disinfected at all points just as quickly as a flat
¦¦ ~trip (wl the same discharge tuùes and the s~une reflector). ~ ¦
The discharge tubes 4 do not have to be matched to a certain feed
` rhythm, i.e. it is immaterial at which point of the irradiated area a
:~ preformed container stops between feed movements.
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Having generally described this invention, a further understanding
can be obtained by reference to certain specific examples which are
provided herein for purpose of illustration only and are not intended to be
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¦ limiting unless otherwise specified. - , -
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¦ FIGURE 5 shows the results of microbiological disinfection tests .
¦ A low-pressure high-current mercury discharge of 10 A/cm and
6 x 10 Torr was used, with a radiation intensity on the 253.7- nm line
of 0.3 W/cm at the test substrate.
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Refined spore cultures of the tested bacteria moulds were applied
to defined surfaces in defined dilutions in the range 10 - 10 per smear,
and partly dried. The cultures were then exposed for different times ~
to the ultraviolet radiation, and afterwards washed off and incubated. The ~ 1 -
reduction of microorganisms was then determined with the aid of absolute
sterility tests.
Tests were pcrformed for the following organisms: ~ -
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' Bacillus subtilis (spores)
Bacillus stearothermophilus (spores )
Es¢herichia coli
Mucor mucedo
Aspergillus Niger
' Penicillium chrysogenum
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Escherichia coli and Mucor mucedo were reduced in 2 to 3 seconds
at a rate K of more than 10 . The results for the other micro-organisms
tested can be seen in FIGURE 5.
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With a spectral (253.7 nm) radiation intensity of 0.3 W/cm, the
effect of the total short-wave UV radiation is such that
-all sporogenetic bacteria with a radiation time of S seconds under- -
go a reduction rate ~ 10 (Subtilis and Stearothermophilus most resistant)
; 5 with initial counts of up to 108 on areas G 1 cm2,
-with a radiation time of 5 seconds all non-sporogenetic bacteria
undergo even much higher reduction rates, and
-in the case of mould spores, radiation times of up to 30 seconds
are necessary (Aspergillus Niger most resistant) to achieve high reduction
rates ~ ` 104). `
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In accordance with the invention, the combined infrared/ultraviolet
technique as described above is used to avoid the possibly long times
necessary to destroy mould spores. For the sake of completeness it may
also be mentioned that it would be perfectly practical to irradiate packag-
l5~ ~ Ing materials 1 and 2 of FIGURE 1 on both sides, i.e. not only on the
contents side, but also on the outside. This would eliminate the danger
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of the sterile space becoming infected by the packing material. ~A
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The method of the invention, together with the apparatus for implementingil, is used with particular success for filling and packing liquids or pastes
in soh or semi-rigid containers, and thus especially for packing up erised
milk in continuous-tube type containers, or for placing yoghourt, soured milk,
~ ~ cream, etc. in portion-sized packages. Hitherto, disinfection with steam or
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hydrogen peroxide ~I202 has been mainly used in these cases. But steam
disinfection presents serious mechunical problems because the steam is highly
corrosive. Disinfection with H202 presents A further problem in that there
must be adequate safeguards to keep the chemical away from the food so that
the method can be at least legally acceptable. None of these problems arise
with the method and apparatus of the invention.
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Since u~ith portion-sized packages the foil cover is colored and covered
with printed matter, and since the packages are particularly susceptible to .
distortion, the use of UV disinfection according to the invention for the foil
cover is of very special significance. It is also possible to employ a classical
method of disinfection, e.g. the H202 technique, for less sensitive containers,
and disinfect only the cover foil with ultraviolet. ; -
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Having now fully described this invention, it will be apparent to one of
ordinary skill in the art that many changes and modifications can be made thereto
without departing from the spirit or scope of the invention as set forth herein.,, . . .~
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