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Патент USA US2405675

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Aug- 13,
'6-
c. A. SOUTHWICK, JR; mm.
METHOD OF FORMING SEALS
25%,675' I
’
Filed July 25, 1940
$41
mam.
Patented Aug. 13, 1946
2,405,675
UNITED STATES PATENT, OFF-ICE
2,405,675
METHOD OF FORMING SEALS
Charles A. Southwick, Jr., South Norwalk, Conn.,
and Arthur F. Stagmeier, Upper Montclair,
N. J ., assignors to General Foods Corporation,
New York, N. Y., a corporation of Delaware
Application July 25, 1940, Serial No. 347,542
8 Claims. (Cl. 154-42)
1
2
This invention relates to the formation of heat
causes loss of time and increased cost and fur
thermore imperfect seals are still encountered
which slow up production and, if undetected,
cause deterioration of the product.
One of the objects of the present invention is to
sealed seams or joints between sheets or layers of
wrapping or packaging material.
In packaging various materials in bags, wrap
pers, carton liners and the like, it is often de
sirable in practice to provide tightly sealed pack
insure absolute uniformity of pressure through
ages. For .example, it is desirable to package some
out the entire sealing zone, regardless of varia
materials under vacuum in substantially airtight
tions in thickness of the material or the pres
packages; in other cases it is desirable to pre
ence of foreign material in the seam, etc.
vent the escape of moisture vapor or volatile con 10
Another object is to facilitate the application
stituents from a package, or to protect the 'con
of heat to the material in such a manner as to
tents of a package from the in?uence of the out
obtain rapid heating to the desired temperature
side air or other medium to which the package
and at the same time a uniform temperature
may be subjected. The accomplishment of these
throughout the sealing zone.
results has been facilitated by the development of 15 A further object is to facilitate the control of
better packaging materials and also by the use
the temperature in the sealing zone.
of thermoplastic sealing materials which become‘
Another object is to provide a method of seal
plastic when heated and hence can be united in
ing thermoplastic materials which does not re
tegrally by the application of heat and pressure.
quire the use of heated metallic sealing members.
In practice such seals ‘are usually effected by
A still further object is to enable more rapid
20
the use of heated presser bars or rollers between
sealing with consequent‘ savings in time and ex
which the juxtaposed layers of packaging mate
rial are pressed together and heated, or by the
‘ The invention is applicable generally to form
use of a heated presser bar or roller in combina
ing and sealing operations with various types of
tion with a yielding backing member. Substan
packages, as for example forming the side and
tial difficulties have been encountered, however, 25 end seams and closing and sealing the mouth of
in the use of this method of sealing. For instance
- bags, wrappers, liners either in or to be inserted
it is dif?cult even with great care to maintain a
later in cartons, etc.-, and regardless of the par
uniform, true pressing surface without distor
ticular material to be packaged. Further any
tion, particularly where the seam to be made has 30 suitable type of packaging material may be em
pense.
substantial length, and as a consequence Varia
.
~
ployed, the choice depending on the nature of the
tions in pressure and temperature cause imper
material to be packaged and the conditions to be
fect seals. Also the use of hot metallic sealing
maintained in the package. Thermoplastic sheet
material or sheet material having a thermoplas
members in direct contact with certain materials
such as Plio?lm involves difficulties due to the 35 tic coating may be used, in which event the seal
tendency of such materials to adhere to the seal
may be formed at any point where two layers
ing members, so that in practice it is customary
of material come in contact, or coatings of ther
to employ laminated sheet stock with resulting
moplastic sealing material may be formed on the
increased cost.
base material. only at points where seals or seams
Further where there are irregularities in the
are I to be formed. Examples of suitable sheet
40
material or where additional thicknesses of ma
materials are rubber or rubber derivatives of the
terial are interposed between the sealing elements,
type known as Plio?lm, waxed paper, heat-seal
the irregular surface of the packaging material
ing cellulosic materials such as heat-sealing Cel
lophane, etc. ,
'
may prevent the formation of a perfect seam.
_ When bulk material is to be packaged, some of 45
It has been found that perfect seals of the types
the loose material may find its way between the
referred to above can be obtained rapidly and with
surfaces to be sealed with similar objectionable re
practically complete uniformity by the applica
sults.- When packaging bulk materials under
tion to the sealing zone of a hot ?uid under pres
vacuum, for example, the package must be evac
sure which presses the packaging material to
uated and thereafter sealed and the suction may 50 getherand at the same time heats it to the de
cause the displacement of some of the material
sired temperature. Gaseous ?uid media are pre
into the sealing zone. In order to minimize ‘the
ferred because of the ease with which they can
above difficulties, the presser elements may :be
be handled and controlled as pointed out herein
maintained in contact with thematerial for a
after. Any suitable inert gas or condensable
substantial period. However, this precaution 55 vapor can be employed with good results, air and
5
2,405,675
‘6
ing-arm l5‘engages the vframe plate 6 and opens
clamping members and then ‘admitting; a hot
the valve [3 admitting steam to'the' nozzle mem-'
fluid under pressure to said chamber to heat and
ber through the pipe I0; Steam thus ?lls the
press said surfaces together while limiting the
passage l2 ‘in contact with the material ‘of the bag
area of pressure application to said zone, where
along the. area 3, but is substantially con?ned b1 byxthe seal is formed .by fluid pressure without
to this area since the bag is clamped tightly be
enclosing said packaging material in a pressure
tween the members. Where the ends of thepas
chamber.
sage i2 extend beyond the material of the bag
'
‘
_
2. The'method of forming a seal between .ad
as shown in Fig. 2, there may be some spacing
jacent ?at sheets of packaging material having
between the ends of the nozzle member and the 10 oppo'sedsurfaces of thermoplastic sealing mate
bag member, the amount of which will depend on
the thickness of the bag material under com,
rial which comprises clamping .said sheets to
gether along the edges of the zone to be sealed,
the clamped portions of the sheets in said zone
pression by the piston l9 and on the yieldability
of the backing memberr However this spacing
forming a pressure chamber with one of‘ said
is very small and the steam leakage at the ends 15 clamping members and then admitting steam
is accordingly very slight, the steam being con
under pressure to said chamber to heat and press
?ned under pressure in the nozzle passage so as
said surfaces together while limiting the area
to maintain a substantially uniform pressure at
' of pressure application to said zone, whereby the
every point in the sealing area 3 and rapidly bring
seal is formed by ?uid pressure without enclos
the packaging material to the desired sealing 20 ing said packaging material in a pressure cham
temperature due both to the latent heat and the
ber.
‘
sensible heat of the steam. As soon as the seal
3. The method of forming a seal between ad
has been completed, the ?ow of operating ?uid
jacent ?at sheets of packaging material having
in the cylinder !8 is reversed Withdrawing the
opposed surfaces of thermoplastic sealing mate
piston 19 and nozzle member 8 and releasing the 25 rial which comprises clamping said sheets to
sealed bag. At the same time valve 13 is auto
gether along the edges of the zone to be sealed
matically closed, cutting off the supply of steam.
between relatively movable clamping members,
It will be seen that the invention insures the
maintenance of uniform pressure and tempera
ture at every point throughout the area of the
seam. Regardless of irregularities of material
or extra thickness due to folds, the packaging
the clamped portions of the sheets in said zone
forming a pressure chamber with one of said
?culties heretofore attendant on the use of
rial in a pressure chamber.
clamping members, heating and pressing said
surfaces together by a hot ?uid under pressure in
said chamber while limiting the area of pressure
material will be pressed together at every point
application to said zone, and controlling the ?ow
in the sealing zone with exactly the same pres
of‘ said ?uid in accordance with the relative move
sure and will be heated rapidly at every point 35 ment of said members into and out of clamping
to the desired sealing temperature. Hence uni
position, whereby the seal is formed by ?uid
formly perfect seals are obtained without the dif
pressure without enclosingsaid packaging mate
.
heated presser bars, rollers, etc., as described
4. The method of forming a seal between ad
above. The desired sealing pressure and tem 40 jacent sheets of packaging material which com
perature can be readily obtained and accurately
prises clamping portions of said sheets together
controlled merely by adjusting the heat content
along the edges of a zone to be sealed, said por
and pressure of the ?uid medium. Another ad
tions having opposed surfaces comprising ther
vantage of the invention, which is of particular
moplastic sealing material, and con?ning a hot
importance in quantity production operations, is
?uid under pressure in contact with one of said
that very rapid sealing can be accomplished by
portions while limiting the area of pressure ap
the use of higher temperatures and pressures,
plication to said zone to heat and press said sur
and the seams can be removed immediately from
faces together, whereby the seal is formed by
sealing position without danger of imperfections.
?uid pressure without enclosing said packaging
This feature of the invention enables quantity - material in a pressure chamber. ,
production of sealed packages at a high rate of
5. The method offorming a seal between ad
speed, with consequent savings in time and ex
jacent sheets of packaging material which com
pense.
It will be understood that the invention is not
limited to the particular embodiments described
above for purposes of illustration, and that vari
ous changes may be made in the details of the
method without departing from the spirit of the ‘
prises clamping portions of said sheets together
along the edges of a zone to be sealed, said por
tions having opposed surfaces comprising ther
moplastic sealing material, and con?ning steam
under pressure in contact with one of said por
tions while limiting the area of pressure applica
invention. The choice of packaging and sealing
tion to said zone to heat and press said surfaces
materials, the particular fluid to be employed for 60 together, whereby the seal is formed by ?uid
sealing, the temperature and pressure to be em
pressure without enclosing said packaging ma
ployed, and other details will depend on condi
tions in each case which have been explained
above and will readily be understood by those
skilled in the art. Hence reference is to be had
to the appended claims for a de?nition of the
limits of the invention.
What is claimed is:
1. The method of forming a, seal between ad
terial in a pressure chamber.
6. The method of forming a seal between ad
, jacent sheets of packaging material which com
prises clamping portions of said sheets together
along the edges of a zone to be sealed between
relatively movable clamping members, said por
tions having opposed surfaces comprising ther
moplastic sealing material, con?ning a hot ?uid
jacent ?at sheets of packaging material having 70 under pressure in contact with one of said por
opposed surfaces of thermoplastic sealing mate
tions while limiting the area of pressure applica
rial which comprises clamping said sheets to
tion to said zone to heat and press said surfaces
gether along the edges of the zone to be sealed,
together, and controlling the ?ow of said ?uid in
the clamped portions of the sheets in said zone
accordance with the relative movement of said
forming a pressure chamber with one of said 75 members into and out of clamping position,
2,4055%
7
which" eomprises
‘wherebyltheseal:iszformediby?uiiiipressurewith
:imt enelosm'gj'ssidipaekagmgmaterial sin :2, pres
:su‘re "ch'aix‘ibet.
-
“A process :‘of irom?n'g "hermetic .heat seals
which comprises lsuperimpb’simg predetermined
mews 'o'f ?exible ssheetimatemalsuiteible f0'r":pa'c'k
aging, at least the meeting surfaces of whiohrare
thermoplastic: :dire'c't‘irrg 29. :current .of warm Ygas
58
{superimposing predetermined
‘areas ofr?exible'sheet materialosuitame iompack
fagéing, iati‘ile'ast :the ;meet‘ingg:surfaces of ‘which are
‘thermoplastic: ‘directing a current :of ‘warm egas
z'ag'a'instlat 'leastmne exterior esurface "of ‘said pre
detem?nedfareasio bring-said thermoplastiosur
faces to their ‘temperature of fusion; supporting
:said qa'rede'termined ‘areasia‘gainst 'the . kinetic :en
Jergy Yo'f vsaid‘geas ‘to ‘produce .an effective sealing
.zatirl‘east one ‘exterior surface 10f zsai'd .zpre
det'e'miined areas to r-rbring .saald thermoplastic 10 fpressune ‘between said thermoplastic ‘surfaces;
surfaces ito lth'eir temperature of :fusion; and sup
‘portmg rsai'd ‘predetermined areas against the
rtanéhshi‘elding 'epredetermined portions :of said
area's fromith‘ej heating :and pressing e?ect .of said
"current.
CHARLES A. :SOUTHWICK, “JR.
isealmg pressuma betweenrsaidtthermoplastic :sur
‘ARTHUR E. :=STAGMEIEB.
15
lfaiees.
‘
‘:8. A 'iprocess ‘of forming ihermetie :heat :seals
kinetic energy ie'fi'sai'dsgeisl to ‘produce ' an :effective
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