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Патент USA US3091124

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May 28, 1963
R. C. WEBSTER
3,091,114
METHOD AND APPARATUS FOR TESTING SEALED PACKAGES FOR LEAKS
Filed Dec. 17, 1959
COMPRESSED
AIR CYLINDER
INFRA- RE D
N20 DETECTOR
\
ROBERT C.WEBSTER
WW 2471?,
United States Patent 0 ""1C6
3,091,114
Patented May 28, 1963
1
2
3,091,114
oxide as an ingredient, may be used, providing that the
same will not be detrimental to the contents of the pack
age, whether food or other items. The preferred gas
consists ‘essentially of a ?rst gas selected from the group
METHGD AND APPARATUS FOR TESTING
SEALED PACKAGES FOR LEAKS
Robert C. Webster, Madison, Wis, assignor to Air Re
duction Company, Incorporated, New York, N .Y., a
corporation of New York
Filed Dec. 17, 1959, Ser. No. 860,263
6 Claims. (Cl. 73-493)
consisting of carbon dioxide, nitrogen and a mixture of
carbon dioxide and nitrogen and a second gas consisting
of nitrous oxide.
The amounts of these gases consists, on a weight basis,
from 75 to 99% of the ?rst gas and from 1 to 25% of
This invention relates generally to the art of leak de 10 the second gas. The preferred gas composition contains,
on a weight basis, 97% of the ?rst gas and 3% of the
tection and, more particularly, to an improved method of
testing sealed packages for leaks and to apparatus for
second gas.
Nitrous oxide is an important ingredient of the inert
readily and economically carrying out the method. The
gas mixture. This is an extremely stable oxide of nitro
invention pertains, in one of its more speci?c aspects, to
gen and is prepared commercially by the thermal de
an improved and simpli?ed method of making and testing
composition of ammonium nitrate at a temperature of
a sealed package which includes a receptacle compris
about 464° F. according to the reaction:
ing a ?exible, deformable, ?uid impermeable sheet ma
terial, whereby to ascertain whether any leaks exist in
the receptacle.
Nitrous oxide affords a number of important advan-.
The invention has Wide application and may be ad
tages in the practice of this invention, including:
vantageously employed in testing various types of sealed
(1) It is non-toxic.
(2) It does not adversely affect the ?avor of food
products when used in the amounts indicated above in
package which comprises a readily deformable receptacle,
a. selected product and a quantity of a nitrous oxide-con 25 the inert gas mixture.
(3) It is non-corrosive, when used as contemplated by
taining inert gas, both the product and the gas being con
this invention.
tained within the receptacle.
(4) It may be readily detected in small or even min
The principal object of the invention is to provide an
ute quantities by commercially available infra-red gas
improved method and ‘apparatus for testing a sealed
packages for leaks. It is primarily concerned and par
ticularly applicable to the ‘detection ‘of leaks in a sealed
analyzers.
package for ‘leaks.
(5) It is relatively inexpensive in the amounts re
Another object of the invention is to provide an eco
nomical and dependable method of determining whether
quired per package.
a package, which is intended to be hermetically sealed
and devoid of leaks, is in fact properly sealed and leak
testing a sealed package according to this invention com
A preferred and recommended method of making and
35
tree.
The invention has for another object the provision of
a simpli?ed method for readily determining the presence
prises ?rst forming the package by introducing a selected
product and an inert gas into a receptacle and heat seal
ing the receptacle with the product and gas therein. The
of leaks in a sealed package ‘which includes a receptacle
inert gas consists essentially of a, ?rst gas selected from
consisting of a ?exible, deformable, ?uid impermeable
sheet material, without damaging the receptacle.
the group consisting of carbon dioxide, nitrogen and a
A further object of the invention is to provide appa
ratus of the character indicated which is sturdy and
durable in ‘construction, which is reasonable in manufac
turing, operating and maintenance costs and which is
capable of performing its intended functions in a depend 45
able and trouble-tree manner.
.
My instant invention is especially concerned with the
detection of any leaks that may exist in a sealed pack
age of the character indicated, wherein the receptacle
of the package is made from a relatively thin, ?exible,
deformable, ?uid impervious sheet material. The pre
ferred sheet material of the receptacle is any suitable
mixture of carbon dioxide and nitrogen and a second gas
consisting of nitrous oxide. The receptacle preferably
consists of a thin, ?exible, ‘deformable, ?uid impermeable
thermoplastic sheet material. The package is placed in
a closed zone which envelops an atmosphere that is de
void of nitrous oxide. The package is then “squeezed”
by being subjected to ‘an externally applied pressure that’
is greater than the pressure existing in the closed zone.
If there are any leaks in the receptacle, this causes the
inert gas, including nitrous oxide, to be discharged from
the receptacle into the closed zone exterior of the re
ceptacle. Immediately following application of the ex
ternal pressure to the package, the gas in the closed zone
exterior of the package is analyzed for the presence of
synthetic thermoplastic resinous composition having the
indicated properties and capable of being economically 55 nitrous oxide to thereby determine Whether any leaks
exist in the receptacle.
fabricated, formed into a receptacle of desired con?gura
tion and then heat sealed. Among the presently avail
able synthetic compositions which are suitable for the
It is essential in practicing this invention that a dif
ferential pressure be developed between the interior of
the package and the region of the closed zone exterior
the package. A differential pressure is necessary to
purposes of this invention are cellophane that has been
coated with wax and rubber and laminates of polyvinyl 60
cause at least some of the inert gas in the package to
idene chloride that are made and marketed by Dow
be discharged through any leaks that exist in the mate
rial
of the receptacle and then analyzed for nitrous oxide.
The package to be tested may contain any desired
To this end, a positive pressure is preferably produced
product, including, but not limited to, food items, such
within the package which is greater than the normal
as cheeses ‘and the like. The detailed description of the 65
pressure therein. While the package may be subjected
invention appearing further .along herein is directed to
to a negative pressure, instead of being subjected to an
application of the invention to the making and testing
internal positive pressure, by creation ofa partial vacuum
Chemical Company under the trademark “Saran.”
of sealed packages containing cheese, by way of illus
in the closed zone, this is not believed to be as advan
trau'on.
tageous in view of the time required and the possibility
As was indicated earlier herein, the receptacle also 70 of damaging the receptacles of sound packages during
contains an inert gas comprising nitrous oxide. Any
testing.
suitable inert gas or mixture of gases, containing nitrous
The enumerated objects and other objects, together
3,091,114
3
1i
with the advantages obtainable by the practice of this
invention, will be readily understood by persons versed
in the art from the following detailed description and the
accompanying drawing which respectively describe and
member 24 by a connector unit 23. The bearing mem
ber preferably consists of a planar plate 24 which is nor
mal to the axis of the piston rod and is provided with a
plurality of perforations 25. The lower face of plate 24
illustrate a package and a preferred arrangement of
should at all times be located above the bottom or open
apparatus for testing the package for leaks in accordance
with the invention.
In the drawing, wherein like reference characters de
end of the hood unit. The distance between the plate
and the bottom of the hood unit is determined by the
thickness of package P which is to be tested. This
making a package to be tested and shows the relative
position thereof in the course of forming the package;
thickness of the package.
One of the hood end walls 19 is provided with a pair
distance may be readily adjusted through the medium
note corresponding parts throughout the several views:
of
set screw 22 and should be slightly less than the
10
FIG. 1 is an isometric view of certain parts used in
' FIG. 2 is an isometric view of the completed package;
FIG. 3 is an isometric view of apparatus for detecting
any leaks that may exist in the receptacle of the package
shown in FIG. 2; and
7
FIG. 4 is a view in enlargement taken along line 4-4
of FIG. 3 and illustrating the parts in another relative
position.
Referring initially to FIG. 2, I have illustrated therein
a package P which is to be tested for leaks and which
of internally threaded stub conduits 26 and 27 which
establish communication between the exterior and in
terior of the hood unit. Conduit 26 is provided with a
nipple 28 while conduit 27 is provided with a like nipple
29.
'
Positioned on platform 10 is an instrument 30 for
detecting the presence of nitrous oxide in gas that is
20 admitted thereto. This instrument is preferably an infra—
red detector that is adapted to receive and analyze rela
tively small amounts of nitrous oxide. Instrument 39
comprises a receptacle 5 and product 6 (FIG. 1) within
is connected to nipple 28 by a ?exible conduit 31 and a
the receptacle. The receptacle is made up of a pair of
?tting 32. Gas that is transmitted to instrument 30
thin, ?exible, deformable, ?uid impermeable sheets 7 of 25 from the hood unit is discharged from the instrument
an appropriate thermoplastic material. Product 6 con
sists of a stack of rectangular slices of cheese 8 which
are of like size.
7
through a conduit 33.
Also positioned on platform v10 are a cylinder 35, con
taining compressed air or other suitable gas for ?ushing
the interior of the hood unit, and a unit 36 for con
In the course of making the package, the facing mar
ginal portions of thermoplastic sheets 7 are brought to
trolling discharge of compressed air from the cylinder
‘gether and heat sealed to obtain a hermetically sealed
in response to operation of instrument 30. Cylinder 35
receptacle 5 with the product 6 contained therein. The
communicates with unit 36 by way of a conduit 37 having
completed package P contains an inert gas in addition to
a series-connected manual control valve 38. Unit 36
the product 6. This gas preferably consists, on a weight
and conduit 37 communicate with the interior of the
basis, of 97% carbon dioxide and 3% nitrous oxide. 35 hood unit by way of a ?exible conduit 40 which is
The inert gas is admitted into the receptacle in any
coupled to nipple 29 by a ?tting 41. Unit 36 is operative
manner known to the art, prior to completing the sealing
ly connected to instrument 30 by a connector 42.
thereof.
For the purpose of outlining the operation of the illus
The pressure of the inert gas within the receptacle at
trated arrangement of apparatus in testing a package P
the time scaling is completed may be atmospheric or, as 40 for leaks, it is assumed that the package is placed on belt
is preferred, slightly above atmospheric, i.e., within the
conveyor C directly beneath the hood unit and that the
range 'of 1 to 3 pounds per square inch gauge.
parts are in the relative position shown in FIG. 3.
The apparatus includes a ?rst support which comprises
is also assumed that the atmosphere surrounding the
package and within the hood is devoid of nitrous oxide.
a ?exible, imperforate, belt conveyor C, the illustrated
Hydraulic ?uid under pressure, from a suitable source
portion of which is disposed horizontally and is movable
toward the right, as indicated by the arrow. The ap
(not shown), is introduced into cylinder 12 above piston,
13 and urges the piston, piston rod 14 and the hood unit
paratus also includes a second support consisting of a
H downwardly from the position shown in FIG. 3 to that
stationary platform 10 that is maintained above and in
spaced relation to the conveyor by a plurality of posts 11.
shown in FIG. 4. This causes plate 24 to bear against
A hydraulic cylinder 12 is mounted on the platform and 50 the upper surface of package 0? and exert a positive pres
is equipped with a vertically reciprocable piston 13.
sure against the package. At the same time, theopen
Secured to and projecting downwardly from the piston
end of the hood unit circumscribes the package and bears
is a piston rod 14 which extends through and below the
against the upper surface of conveyor C, thereby de?n
bottom wall of cylinder 12 and platform 10. The cylin
ing a closed zone with the conveyor. The pressure ex
der is connected to a pair of conduits 15 and 16, conduit 55 erted by plate 2.4 on the package will depend on the con
15 communicating with the interior of the cylinder above
?guration of the package and the material of the pack
the piston and conduit 16 communicating with the inte
age receptacle. This pressure should be su?icient to
rior of the cylinder below the piston. These conduits are
force inert gas, including nitrous oxide, outwardly
adapted to transmit and withdraw water or other suit
through any leaks that may exist in the receptacle ma
able liquid under pressure into and from the cylinder 60 terial without damaging the material of the receptacle
whereby to impart reciprocation to the piston in the
or the product contained therein. Gas in hood unit H is
'usual manner.
continuously or intermittently analyzed by infra-redde
A hood unit H is positioned between the platform and
tecting instrument 30. If no nitrous oxide is evolved
the conveyor and is secured to and reciprocable with
during testing of a particular package, instrument 30, of
the piston rod and the piston. The hood unit includes 65 course, indicates that the gas admitted thereto is free of
a top wall 17, a pair of parallel side walls 18 and a pair
nitrous oxide. If the gas within the hood unit contains
of parallel end walls 19. The hood unit is open at its
nitrous oxide that is discharged from a particular pack
lower end, as shown in FIG. 4. A collar 20 is positioned
age during testing, the presence of such nitrous oxide will
centrally on top wall 17 and is rigidly secured thereto,
be indicated by instrument 30 and the package should be
preferably by welding, as indicated at 21. Piston rod
discarded or reformed with a new receptacle.
14 extends through collar 20 and an aligned opening in
The interior of the hood unit is purged by ?ushing with
top wall 17. The piston rod is adjustably secured to
compressed air from cylinder 35 to remove traces of
the hood unit by a set screw 22 which is carried by
nitrous oxide after instrument 30 indicates that leaks
collar 20.
exist in a particular package. Transmission of com
The lower end of the piston rod is a?ixed to a bearing 75 pressedrair from the cylinder to the hood unit is con
3,091,114
6
interior of the hood unit for detecting the presence of
trolled by unit 36 which, as indicated earlier, is respon
sive to operation of infra-red detecting instrument 30.
Unit 36 may be of any desired construction capable of
performing the indicated function. It may be electro
nitrous oxide in gas admitted into the hood unit, and
means responsive to operation of the last-mentioned
means for ?ushing the interior of the hood unit with a
gaseous composition that is devoid of nitrous oxide.
3. In apparatus for detecting leaks in the sealed re
ceptacle of a package which includes a product and an
inert gas comprising nitrous oxide that are contained in
the receptacle, said receptacle comprising a ?exible, de
mechanical and include an electromagnet or similar de
vice that is actuated in response to operation of instru
ment 39 to control ?ow of compressed gas from cylinder
35 to hood unit H. The interior of the hood unit may,
if desired, be ?ushed after each test regardless of whether
instrument 3% indicates that leaks exist in a particular 10 formable, ?uid impermeable sheet material, the combina
tion comprising support means, including a ?rst support
receptacle.
and a second support, said package being adapted to be
The infra-red method of detection, as exempli?ed by
placed on the ?rst support, a hood unit carried by the
the use of instrument 30, is well known and utilizes the
second support above the ?rst support and movable up
ability of nitrous oxide to absorb radiation in the infra
red spectra. Detecting instrument 30 need not be de 15 wardly and downwardly relative to the second support,
said hood unit being open at its lower end, said hood unit
scribed in detail here since it embodies a generally well
including a bearing member Within its con?nes and spaced
known construction. Among the suitable commercially
above its open end, the ?rst support and the bearing
available infra-red detecting instruments is one manu
member being adapted upon predetermined downward
factured and marketed by Perkin-Elmer Corp., Norwalk,
Connecticut.
20 movement of the hood unit to apply su?'icient pressure to
the package to effect discharge of inert gas from the in
terior of the receptacle through any leaks that may exist
in the receptacle, and means communicating with the
interior of the hood unit for detecting the presence of
nitrous oxide in gas admitted into the hood unit.
4. In apparatus for detecting leaks in the sealed re
ceptacle of a package which includes a product and an
sense. For example, hood unit H may be of a size and
inert gas comprising nitrous oxide that are contained
construction that is capable of accommodating a plural
in the receptacle, said receptacle comprising a ?exible,
ity of packages instead of a single package, as shown, and
cooperate with other parts in simultaneously testing all 30 deformable, ?uid impermeable sheet material, the com
bination comprising support means including a ?rst sup
such packages for leaks.
port and a second support, said package being adapted to
I claim:
be placed on the ?rst support, a hood unit carried by the
1. In apparatus for detecting leaks in the sealed re
second support above the ?rst support and movable up
ceptacle of a package which includes a product and an
wardly and downwardly relative to the second support,
inert gas comprising nitrous oxide that are contained in
said hood unit ‘being open at its lower end, said hood
the receptacle, said receptacle comprising a ?exible, de
unit including a bearing member within its con?nes and
formable, ?uid impermeable sheet material, the combi
spaced above its open end, the ?rst support coacting
nation comprising support means, a hood unit carried by
substantially simultaneously with the hood unit and the
the support means and movable toward and away from a
selected part of the support means, said hood unit being 40 bearing member upon predetermined downward move
It will be appreciated that various changes may be
made in the above-described method and apparatus with
out departing from the invention or sacri?cing any of
its advantages. Accordingly, it is to be understood that
all matter contained herein shall be interpreted as being 25
illustrative and explanatory rather than in a limiting
open at one end, said hood unit including a bearing mem
ment of the hood unit to respectively de?ne a closed zone
and apply sufficient pressure to the package to effect dis
ber within its con?nes and spaced from its open end, said
charge of inert gas from the interior of the receptacle to
package being adapted to be positioned in the open end
the closed zone through any leaks that may exist in the
of the hood unit between said selected part of the sup
port means and the bearing member, said part of the sup 45 receptacle, and means communicating with the closed
zone ‘for detecting the presence of nitrous oxide in the
port means and the bearing member being adapted upon
closed zone exterior of the receptacle.
predetermined movement of the hood unit toward said
5. Apparatus according to claim 4 wherein the bearing
part of the support means to apply su?icient pressure to
member comprises a perforate plate and wherein the hood
the package to effect discharge of inert gas from the in
unit also includes means for varying the distance between
terior of the receptacle through any leaks that may exist
the plate and said open end of the hood unit.
in the receptacle, and means communicating with the in
6. Apparatus according to claim 4 including means re
terior of the hood unit for detecting the presence of
sponsive to operation of the last-mentioned means for
nitrous oxide in gas admitted into the hood unit.
2. In apparatus for detecting leaks in the sealed re 55 ?ushing the interior of the hood unit with a gaseous com
position that is devoid of nitrous oxide.
ceptacle of a package which includes a product and an
inert gas comprising nitrous oxide that are contained in
References Cited in the ?le of this patent
the receptacle, said receptacle comprising a ?exible, de
UNITED STATES PATENTS
formable, ?uid impermeable sheet material, the combina
tion comprising support means, a hood unit carried by 60 1,538,369
Akiyama ____________ __ May 19, 1925
the support means and movable toward and away from
2,011,332
Chapman _____________ __ Aug. 13, 1935
a selected part of the support means, said hood unit being
2,834,686
Reuman ______________ __ May 13, 1958
open at one end, said hood unit including a bearing mem
ber within its con?nes and spaced from its open end,
OTHER REFERENCES
“Symposium on Non-Destructive Tests in the Field of
said package being adapted to be positioned in the open
end or" the hood unit between said selected part of the 65 Nuclear Energy,” Pappin paper “Helium Leak Detection
support means and the bearing member, said part of the
support means and the bearing member being adapted
upon predetermined movement of the hood unit toward
said part of the support means to apply sufficient pres
Techniques,” Chicago, Apr. 16-18, 1957 (published
1958), Patent O?ice Scienti?c Library call number TK
9153, A52, pp. 328 and 332, Methods of Test, relied on.
“Nitrous Oxide .for Leak Detection,” publication of
sure to the package to effect discharge of inert gas from 70 Ohio Chemical & Surgical Equipment Co., Madison 10,
Wisconsin, Technical Information Series I.B., received
the interior of the receptacle through any leaks that may
U.S. Patent O?ice May 23, 1958 (Copy in Div. 36).
exist in the receptacle, means communicating with the
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