Note: Descriptions are shown in the official language in which they were submitted.
9493
~4S58~
This in~ention relates to an improved method for
inerting the surface o~ a cross-linkable polymeric product
while the product is in motion.
To accomplish effective inerting in a dynamic
system, the inerting procedure mu~t account for the air
lying immediately above the product which, as the product
moves, tends to be drawn with the product and along its
surface. Hence, simply purging the work zone, although
effective in a static system, is entirely inade~uate and
unsuitable for the dynamic system.
Common to the dynamic inerting system disclosed
in the above cited patent applicatlon and to the present
invention is an enclosure including a treating chamber,
which houses the source o~ radiant energy, an entrance ;~
tunnel leading to the treating chamber and adapted to
receive the product, and an exit tunnel extending rearward
from the treating chamber. Likewise, the design of the
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inerting system to be disclosed herein adheres to the
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9493
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principles of the cited patent application concernlng the
relevance o~ the inerting geometry to the dynamic sy~tem
although directed to an improved method of pas~ing the
inert gas into the enclosure~ The mean~ for inJecting the
inert gas must take such ~orm as to provide a substan-
tially unidirectional curtaln or stream o~ inert gas having
a width at least equal to the width of the moving product
and muRt be so oriented a~ ko direct the stream o~ gas
toward the moving product so that the stream intersects
with the surface o~ the product at a predetermined angle
of inclination and with a component o~ velocity opposed
to the movlng product. An elongated channel or slot
formed ln the tunnel surface wall, as is shown in the afore-
mentioned patent application, represents the pre~erred inert
gas ln~ector mean~.
Heretofore lt wa~ necessary for the enclosure exlt
tunnel to have a length sub3tantially greater than the
entrance tunnel length. In thl~ manner the ma~ority of the
inertlng gas wa~ ~orced to ~low out the entrance tunnel.
This method o~ controlllng gas flow direction proved to be
~atisfactory at low and moderate product line speeds o~ less
than ? feet per min. However, at higher line speeds, o~
over ? feet per minute and up to about lO00 feet per minute,
the length o~ the exlt tunnel becomesJ from a practical
standpolnt, prohlbltive. It has now been dlscovered that
the length o~ the exit tunnel can be 3igni~1cantly reduced
and in ~act rendered ec~entially independent of the length
` of the entrance tunnel provlded that:
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~SS~ ,
(1) the inert gas stream is fed into the enclo-
sure at an included angle of above about 45 degr-ees but
below about ~5 degrees with respect to the longitudinal
axis o~ the enclosure, said angle oriented such that the
~ issuing gas stream has a velocity cGmponent ln a direction
- opposed to the directlon of the moving product;
(2) the inert gas flow rate exiting from the
entrance and exit tunne} respectively is held to below a
critical volumetrlc flow level per unit Or tunnel width
for each speclfic inert gas composition; and
~3) the inert gas velocity component opposing
the moving product has a magnitude ~ubstantially equal to
and pre~erably greater than the velocity of the moving
product.
The speciflcation of any given production line
~ facility and tunnel design parameters outlined in the pre-
; viously clted patent may then govern khe total enclosure
design length with the inert gas in~ector inclination angle
and flow rate chosen to satisfy the hereinabove stated
conditions. Moreover, by ~atis~ying the above stated
conditions, occasional instability ln the direction o~
inert gas ~low within the enclosure, w~lch has been noted
to occur particularly at higher operatlng speeds, has been
ellminated.
It has been further demonstrated that, provided
the above noted conditions are satlsfied, the ~tream of
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9493
~45~8~
inert gas can be introduced into the enclosure either up-
stream of the treating chamber as is shown ln khe a~ore-
mentloned patent applicatlon or, i~ des~red, downstream
o~ the treatlng chamber. The latter arrangement has been
found to be particularly advantageous in applications
where the product consists of a plurallty Or entlties each
of finlte length and where the product thickness varies
.
over at least about one-quarter lnch in depth.
Accordingly, lt is the principal ob~ect Or the
present inventlon to provide a method for maintainlng a
substant~ally inert atmosphere at the surface o~ a moving
product as it moves through the interior o~ an enc:Losure.
It is a ~urther ob~ect Or this invention to pro-
vide a method of inertlng the sur~ace o~ a moving product
at product travel speeds of up to about 1000 feet per min.
and regardless of whether the product is of a contlnuous
`' length or represents one Or a plurality of entitles each
of flnite length and thickness.
Other ob~ects and advantages will become appar-
ent ~rom the rollowing detailed de~criptlon when taken in
connection with the accompanying drawings o~ which:
~igure 1 is a diagrammatic illuRtration in long-
itudlnal section of a treatment enclosure ~or lrradiating
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a moving product ln an atmosphere to be controlled in
accordance with the teachlngs oP the present invention;
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Figure 2 is an exploded view of the inert gas
in~ector showlng the pre~erred angle of inclination ~or
the in~ector relatlve to the longitudinal axis of the
enclosure; .
Figure 3 is an illuatrative isometric o~ a por-
tion of either tunnel of the enclosure of Figure 1 in -~
which the inert gas in~ector is located wlth a sectlon~:
thereof cut-away to illustrate the lateral orientation
of the inert gas in~ector relative to the. width o~ elther
tunnel respectively.
Re~erring to Figure 1-3 inclusive in which the
treatment enclosure 10, ~or lrradiating the moving product
P, i~ diagrammatlcally illustrated and comprises a treat-
ing chamber 12 which hou~es a ~ource o~ radiant energy ..
(not shown?; an entrance or inlet tunnel 14 located up-
stream o~ the treating chamber 12 in the directlon Or the :.:
moving product P; and an exit tunnel 16 extendin~ down-
. I stream of the treatlng chamber 12. The term "tunnel" ~or
purpo~es of the pre~ent disclo~ure is de~ined a~ a hollow
pa~sageway Or uni~orm cro~s-~ectlon which may either have
a sel~-enclosed perlphery or a partially enclosed periphery
whlch become~ ~ub~tantlally fully enclosed ~hen the moving
product P 18 pre~ent and whlch preferably con~orms to the
de3ign parameters outlined ln the aforementioned patent
application. For simpllcity o~ illu~trationg the medium
18, whlch may represent, for example, a conveyor belt
sur~ace ~or advancing the product P through the en~ .:
closure 10~ hown rormlng the physical bottom of the
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9493
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enclosure 10. It should be understood, however, that the
bottom of the ~nclosure 10 may be formed in any manner and
is, in fact, preferably established by the moving product
itself where the product is continuous.
The product P may represent a chemical coating
or a coated substrate and may be of a continuous length
such as a web or of a finite length. In the latter in-
stance the product P would actually be presented to the
enclosure for treatment as a series of abutting or spaced
entities. For purposes of the present invention any source
of radiation may be employed to treat the product P within
the treating chamber 12 of the enclosure 10 although an
internally cooled or non-cooled source is preferred. Pre-
ferred sources of actinic radiation are low pressure ultra-
violet mercury tubes and/or germicidal lamps.
Inert gas G. is supplied from an inert gas plenum
chamber 19 and passed through an inert gas injector 20
into the enclosure 10. The source of supply for delivering
the gas to the plenum chamber 19 is n~t shown. The inert
gas injec~or20 is orientecl wi~h respect to the longi~udinal
axis of the enclosure 80 that its shorter axis intersects
with the longitudinal axis forming the acute angle " '~" ;
as shown in Figure 2. Angle 'lc~ll is defined as the angle
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form~d between the stream of inert gas G, issuing from the
gas injector 20, and the longitudinal axis of the enclosure ;
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9493
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~4S515~
10 along which the product P is intended to travel and
shvuld lie within a range of above about 45 degrees but
below about 85 degrees and be oriented within such range
such that the gas stream has a velocity component in a
` direction opposing the moving product and of a magnitude
at least about equal to the velocity o the product. The
gas injector 20 may be fabricated by orming a slot in the
top surface of th~ enclosure 10, as shown in Figures 1 and
3 respectively. The longer or longitudinal axîs of the gas
injector 20 should lie substantially parallel to the width
of either tunnel 14 and 16 respectively as i9 shown in
Figure 3
; It has been taught that dynamic inerting requires
a non-tur~ulent non-mixing inert gas 10w within the
interior of the enclosure 10. It has now been dis-
; covered thatthe required non-turbulent non-mixing flow
within the enclosure 10 is assured regardless of product
speeds up to about 1000 feet per min. by the combination of:
introducing inert gas into the enclosure 10 in the form of
a substantially unidirectional stream; appropriately direc- ~
ting the inert gas stream toward the advancing product P at ;
the preferred angle " ~"; and maintainlng an inert gas
volumetric 10w per unit of ~unnel width, which is limited,
or each inert gas composition, to a maximum level out of
each tunnel 14 and 16 respectively. For an inert gas of
substantially nitrogen th~ volumetric flow per unit of
tunnel width out from each tunnel 14 and 16 respectively
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must be below about 650 cu.ft./hr. per foot of tunnel
wldth. For helium the maximum level is about 5000
cu.ft./hr. per foot of tunnel width and ~or carbon dioxide
the maxlmum level is about 360 cu.ft./hr. per ~oot Or
tunnel width. The above levels were determined mathe-
matlcally and con~irmed experimental~y. It should be
noted that the above levels are independent of tunnel
height and independent of product speed at least up to
about 1000 feet per mln.
Moreover, it has ~urther been discovered that
substantially all of the air carried with the advancing
product P, upon approaching the inlet openlng 22 of the
enclosure 10, may be strlpped of`f the product sur~ace and
dlverted away from the enclosure 10 provlded thak; the
inert gas veloclty component, in the direction opposing
the moving product P, has a magnitude ~ubstantially equal
to or greater than the veloclty of the moving product P.
. .
This is based upon a study made o~ the atmosphere within
the enclosure 10. Measurements of the oxygen levels within
the enclosure 10 have ~hown levels of 50 to 100 ppm and
~enerally less than 500 ppm under typical operating condi-
tions at line speeds in the range o~ about 300 to about
1000 feet per minute. '~
As previously stated, the lnclined position of
the inert gas injector 20 provides a pre~erenkial direction
for the lnert ga~ ~low toward the upstream end o~ the en-
closure 1~. This pre~erence has been shown to exist not
only when the in~ector 1~ located in the forward tunnel 14
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but also when located in the exit tunnel 16. The
injector can be as equally effective when located in
the exit tunnel 16 as it is when positioned in the entrance
tunnel 14 but not necessarily at the same angle of
inclination. Moreover, although the entrance tunnel 14
should still have a length which extends from the
inlet 22 downstream to the injector 20 a distance equal
to at least ten times the smallest cross-sectional dimen-
sion of the tunnel opening; the length of the exit tunnel
16 no longer must bear any relationship to the length of
the entrance tunnel 14.
The faster the product travels through the en-
closure 10 the more the injector should depart from a
vertical position, i.e., the angle of inclination "c~ "
should become smaller. An angle Ic~" o below about 45
degrees, however, significantly raises,the danger of estab-
lishing a venturi effect at the rear of the enclosure
causing air to be drawn into the enclosure 10 through
the exit tunnel 16. The preferred angle for speeds above
200 feet per minute is about 60 degrees.
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For a slower moving product below 200 feet per
min. and particularly a discontinuous product~ it is more
desirable to operate at a higher angle Or incllnation
llmited however to below about ~5 degrees, pre~erably at
about 75 degrees. At this angle any slight perturbation
ln flow which might develop due to a thicknes~ varlation
in product P o~ greater than one-quarter inch or due to
a sudden change in product speed will not upset the pre~-
erential flow condition out o~ the entrance tunnel 14.
Although the method o~ the present invention
;~ has been described with reference to a single in~ector
20, lt i5 obvious that a tandem combination o~ ln~ectors
may be used provided that the stipulated condltions of,
maximum volumetric ~low, total velocity component oppos-
ing the moving product and range of incllnation angle be
observed. In the latter respect, lt is also apparent
that the in~ector 20 need not be fabricated so as to be
stationary in orlentation. Instead, an ad~ustable in~ec-
tor means may be employed for a~lxing any deslred angular
orientation within the prescribed range. It should be
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further understood that it will be apparent to one o~
ordinary sklll in the art to suggest mlnor variations
and modi~cations without departing from the scope and
- ~pirit o~ the invention as is hereby claimed. ~'
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