Note: Descriptions are shown in the official language in which they were submitted.
20~8928
ULTRASONIC WELDING IN POUCH MANUFACTURE
BACKGROUND OF THE INVENTION
This invention relates to an apparatus and a method for the
manufacture of filled pouches from films using ultrasonic welding. More
particularly, this invention relates to the use of an ultrasonic sealing
assembly to form pouches through the sealing of seams of films and also for
cutting the films to form the individual pouches.
There are various techniques that can be used to form pouches from
films. Regardless of the technique, seals will have to be made. The flat
film must be manipulated to provide both a front portion and a back
portion. This can be done in many ways. One convenient way is to first
form the film into a tube and then to form the tube into pouches. In this
technique, there will be a longitudinal seam where the film is formed into
a tube and end seals for the formation of the tube into a pouch. An
advantage of the technique of forming the film into a tube, and then
forming the tube into a pouch is that in the process of the formation of
the tube into a pouch, the pouch can be filled. There are advantages to
forming and filling the pouch in the same sequence.
Films can be sealed to form pouches using various techniques.
Adhesives can be used to form seals. A heated platen can be used to seal
thermoplastic films. Dielectric heating, also known as radio frequency
(RF) heating, can be used However, the use of ultrasonic sealing has
'
; ' ~ .:
:
advan~ages over any ~ these techlliques, nnd pnrticul ~ly in f`orm/~
~equences. Whcn adhesives are used, there are solvent ~emoval ~ ~ ~ ~ 2 8
There are also required cure times. The use of a heated platen is not
efficient since the film must be heated by conduction. In RF energy,
heating the full thickness of the Eilm is heated rather than the film
surface. This provides good sealing but is restricted to films that absorb
a sufficient arnount of RF energy to soften. Also, since the full thickness
of the film is heated, there is the potential for overheating the film and
depositing pieces of film, known as flash, onto the electrodes. This will
affect subsequent seals made by the electrodes until they are cleaned.
It has been found that the use of ultrasonic sealing for forrning
pouches from thermoplastic films is an improvement over the use of
adhesives, heated platens or RF energy. In ultrasonic sealing, only the
surfaces that are to be bonded are heated. They are heated by absorbing
impact energy. The full thickness of the film is not heated. This provides
for various advantages. Films that do not have a sufficiently high
absorption for RF energy can be used to make the pouches. The problem of
flash formation is also obviated. Due to the heat being formed only at the
impact surfaces, flash will not be produced.
It has also been found that the use of ultrasonic sealing has distinct
advantages in form/fill operations. These are operations where the pouch
is filled as it is forrned. A problern with form/fill operations for pouches
is that during the filling sequence, there is a tendency for the product to
contact the area of the pouch that is to be sealed. In other types of
sealing, including RF sealing, this can produce weakened seals. However,
in ultrasonic sealing there is a cleaning of the surfaces that are to be
bonded prior to bonding. This is accornplished by surface to surface
vibration Consequently, it has been found that the use of ultrasonic
" ' '': :
sealing in ~orm/fill ~p~ation~; has distinct advantag~ . It ~roduces2 0 4 8 9 2 8
~onsistent high strength seals.
Ultrasonic techniques have been used in bonding various materials.
They have also been used in making bags and pouches. In U.S. Patent
4,734,142 there is disclosed a bag sealing machine which utilizes
ultrasonic sealing. The bag that is produced would contain meat or
produce. U.S. Patent 4,767,492 discloses the use of ultrasonic techniques
for sealing tubular containers. These containers are sealed in a separate
operation after filling In U.S. Patent 4,866,914 there is disclosed an
ultrasonic device for sealing pouches. A product is placed into the pouch
and the pouch subsequently ultrasonically sealed in another operation. It
is noted in this patent that any foreign substances adhering to the sealing
surfaces will be removed during the sealing operation. These patents
illustrate the state of-the-art of ultrasonic sealing pouches. However,
none of these patents is direeted to the use of ultrasonic sealing in a
form/fill process.
It is also known to use an ultrasonic horn an anvil to both seal and
to cut a film. In U.S. Patent 3,939,033 there is disclosed a process where
the stationary fixture has a first raised means for sealing and a second
raised means for cutting. That is, the same surfaee does not do the
sealing and the cutting. However, it has been found that the same surface
can do both the sealing and the cutting. This results in a more effieient
ultrasonic unit.
BRIEF Sl.3MMARY OF THE INVENTION
It has been found to be advantageous in forming and filling
thermoplastic pouches to use ultrasonic sealing techniques in forming the
pouches. Ultrasonic sealing has advantages over the use of adhesives,
conduction heating or dielectric heating. A distinct advantage is the
2048928
62301-1698
ability to simultaneously clean the surface of the film that is
to be a part of the seal while heating this surface to at least
its melting point. l~his is important in form/fill sequences where
the pouch will be formed and filled in the same sequence. In such
packaging operations, the substance being packaged, usually a
liquid, will contaminate some of the seal area when it is flowed
into the open pouch. In order to get a good seal, this area
should be clean. This can be accomplished in various ways. How-
ever, the most efficient way is to use ultrasonic sealing techni-
ques. In this way, the sealarea will be cleaned as it is being
sealed.
More specifically, the invention provides a method
of forming a shaped, sealed flexible film pouch containing a liquid
substance comprising partially forming flexible film into a pouch
using ultrasonic energy, substantially filling said partially
formed pouch with said liquid substance, closing said pouch by
sealing the opening through which the pouch has been filled using
ultrasonic energy applied by an ultrasonic horn to an anvil at
first contact pressure, and increasing the contact pressure to
sever the film.
The invention also provides a shaped sealed flexible
film pouch containing a liquid substance comprised of one or more
plies, having a side seam, a lower seam, an upper seam, and a spout,
all sealed through the use of ultrasonic energy.
The invention further provides an apparatus for
forming and filling pouches comprising:
2098928
62301-1698
(a) means to shape a flexible film into a tube having an
overlapping longitudinal seam
(b) a first ultrasonie horn and anvil assembly;
tc) means to position the overlapping longitudinal seam
of said flexible film between said first ultrasonic horn and
anvil;
~ d) means to actuate said first ultrasonie horn and anvil
assembly to seal said overlapping seam to form a tube;
(e) a seeond ultrasonic horn and anvil assembly located
subsequent to said first ultrasonic horn and anvil to form top
and bottom closures on said tube and produce a pouch;
(f) means to actuate said second ultrasonic horn and anvil
assembly at a first contact pressure to seal said top and bottom
closures and at a second contact pressure to sever the film that
has been sealed to separate a filled pouch from said tube; and
(g) filling means subsequent to forming said bottom
closure and prior to forming said top closure to substantially
fill said pouch.
The ultrasonic sealing unit is comprised of an ultra-
sonic horn and an anvil for the dual purpose of sealing a film
and cutting a film. This is aeeomplished by the same surfaees on
the ultrasonic horn and anvil. The shaped cutting surface will,
preferably be a part of the anvil and will be of a triangular
cross-seetional shape. The outside base angles of the triangle
will be about 120 to 160. This will provide for 20Q to 60
interior angles. The top of the shape terminates in a smooth edge.
- 4a -
20~8928
62301-1698
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a rear elevational view of a pouch with
a beak spout formed using ultrasonic techniques.
Figure 2 is an elevational view of a sealing unit
for sealing the longitudinal seam of the pouch of Figure 1.
Figure 3 is a cross-sectional view of an anvil for
sealing and severing a film.
Figure 4 is a top plan view of the ultrasonic horn/
anvil assembly for forming the top and bottom seals and beak
spout of the pouch of Figure 1.
Figure 5 is a cross-sectional view of the ultrasonic
horn/anvil of Figure 4 along line 5-5.
- 4b -
r'i~ure b is an ~l~ational view of t:no trallxvers~ ~Lrasonic ~ Pn~a~ ~ 2 8
anvil assembly
Figure 7 is an elevatiGnal view of the form/fill unit for forming and
filling pouches.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a process for the ultrasonic
sealing of pouch containers during the process of filling the pouches as
well as the use of the ultrasonic horn and anvil assembly as a means for
both sealing and cutting the thermoplastic film. In this regard, the
ultrasonic horn and/or anvil must be of a particular shape in order to
provide for the dual functions of sealing a thermoplastic film and then
severing the thermoplastic film in the region of the seal.
In order to provide for both the ultrasonic sealing of thermoplastic
film and the subsequent severing of the film at least one of the ultrasonic
horn or the anvil will have to be shaped for the severing operation. It is
possible to have both the ultrasonic horn and the anvil of the ultrasonic
sealing unit shaped to effectuate severing. However, this is not
necessary. Only the ultrasonic horn or the anvil needs to be shaped for
cutting. In this regard, it is preferred to shape the anvil. This is the
case since the shaped piece will have greater wear. It is preferred to
have an accelerated wearing of the anvil rather than of the ultrasonic
horn.
The present process will be described with reference to the
manufacture of pouches having spouts. An illustrative pouch is set forth
in Figure 1. This pouch is designated 10 and has a rear surface 11,
longitudinal seal 12, a bottom seal 13 and a top seal 14. There is also a
beak spout 15 with a cut-out 17 and associated seal 16. The rear pouch
surface is designated
2~ 2~
in the process ~ ~olming alld ~illin(3 the pol~che~ ~t li~ure 1, a film
is in a first step formed into a tube which is accomplished by each edge of
the film being overlapped from about 0.1 cm to 1.0 cm to form a seam. This
seam is passed between the ultrasonic horn and an anvil of a longitudinal
ultrasonic sealing unit. Since the seam is now between the ultrasonic horn
and the anvil upon the application of pressure and ultrasonic energy to the
ultrasonic horn and/or anvil the thermoplastic material at the seam
juncture is heated and bonded. Pressure is preferably applied to the
ultrasonic horn. After this step, the film is now in the shape of a tube.
Preferably, at the same time that the side seam is being sealed, a pouch
top seam is being formed and sealed on a lower pouch. Also preferably at
this time the beak spout is being formed on this lower pouch and a bottom
seal on yet a further lower pouch. This is the case since the film is in a
stationary position and for increased efficiency more than one operation
can be conducted on the film at this time. Thus a side seal, a top and
beak seal and a bottom seal are all being made at once, although on
different pouches. This top and beak spout seam are formed by means of a
separate transverse ultrasonic sealing unit vis-a vis the side seal unit.
This lower transverse ultrasonic sealing unit, will in a first step, place
the interior surfaces of the tube into contact to form both the top closure
seam and the beak spout seam, and thence through the application of
pressure and ultrasonic energy will cause this pouch top seam to be bonded
and the beak spout to be formed by bonding the surfaces to this shape.
This film is now in the form of an inverted pouch which is open at its
upper end. At this point, it is now reaay to be filled with a substance,
usually a liquid. After filling, this filled pouch moves downwardly and
the transverse ultrasonic sealing unit is activated for another cycle. The
pouch bottom seal is formed on this filled pouch in this next cycle.
Simultaneo~sly the top ~eal is formed on the adj~cent ~per pouch ~8928
with a seal to form the beak spout. In each cycle after these seals are
formed, the application of ultrasonic energy ceases and the pressure of the
anvil against the ultrasonic horn is increased. In this way, the anvil and
ultrasonic horn then function as a severing device to sever the film to
form the beak spout on an upper pouch and to sever the now sealed and
filled lower pouch from the upper pouch which has had the top seal formed
but has not as yet been filled.
In summary, the transverse ultrasonic energy sealing unit, at the same
time as sealing the bottom seam of a filled lower tubular pouch will also,
seal the top seam of an upper pouch and form the beak spout of this upper
pouch. This step can be carried out concurrently with other sealing steps
since the film is in a stationary position. In this way, in this form/fill
sequence, three different sealing operations can be conducted during each
interval when there is a pause in the flow of the film. The side seam is
sealed to form a tube, the top seal and spout are made for a pouch for
which the side seam has previously been made, and the bottom closure seal
is made on a lower pouch which has just been filled with a substance.
After the top seal and beak spout of the upper pouch and the bottom seal of
the lower pouch have been formed, the ultrasonic energy is stopped and the
pressure between the anvil and the ultrasonic horn is increased to thereby
sever the lower filled pouch from the upper empty pouch. The lower filled
pouch is then forwarded for packing and the upper formed pouch is filled.
Also in the above sequence as the transverse seals are being formed, the
beak spout is being formed.
A persistent problem with regard to these pouch containers is that of
the contamination of the transverse sealing areas at the time that the
pouch is being ~illed. This is a contamination by the contents that are
,.
bein~ flowed into th~ ~uch. This is ca~ed by a ~pl~ing of the 2 04 8 92 8
~ubstance being flowed into the pouch and a dripping of the product upon
the termination of the filling process. Since the inner thermoplastic
surfaces are to be bonded, one to the other, an excessive contamination can
affect the integrity of the transverse seals. However, since in ultrasonic
sealing it is the film juncture that is being heated, rather than the full
thickness of the thermoplastic fiLm, there is a more effective weld sealing
of the pouches using ultrasonic sealing rather than other techniques. This
is the case since the ultrasonic energy is focused on the inner juneture
surfaces of the thermoplastic film and will quite efficiently remove any
contaminating substances from these surfaces prior to seal formation. This
is in contrast to radio frequency heating, also known as dielectric
heating, where the full thiekness of the thermoplastic film is heated. In
dielectrie heating there is not a concentration of the bonding energy only
onto the thermoplastie junetion surfaces. It is also not an energy which
assists in the cleaning of the bonding surfaces.
The longitudinal sealing unit is shown in Figure 2. The ultrasonic
horn 20 and the anvil 21 can each have a flat working surface. The
surfaces will either both be smooth, or one surface can be textured and the
other smooth. In use, surface 22 of the ultrasonic horn is in close
proximity to the surface 23 of the anvil. The anvil can optionally be
eooled by flowing water or other fluid through each unit. If neeessary the
ultrasonic horn ean be cooled by a jet of air. In the present instance,
each of the ultrasonie horn and the stationary fixture are designed to be
cooled. In this regard, the anvil has inlet port 27 and exit port 28 for
the flow of a cooling fluid. Although any of the usual frequencies of that
are used for ultrasonic sealing can be used, it is preferred to use a
frequency of about lO KHz (kilohertz) to 70 KHz and most preferably about
.;... . .
2048928
20 ~z to ~10 ~ ner3y i:. supplied to ~he ult:rason ~ horn through
~booster 29.
The longitudinal sealing unit is designed for sealing and need not be
capable of also cutting film. However, when it is desired that this unit
also be used for cutting, the anvil of ultrasonic horn would have a contact
surface as shown in cross section in Figure 3. The angle A of the surface
30 is from about 120~ to 160, and preferably about 150 to 175. This
results broadly in an interior angle of 20 to 60 The top surface 23(a)
is an edge and is sufficient to produce an effective seal, but yet as the
pressure between the ultrasonic horn and the anvil is increased, the film
can be cut.
In Figure 4, there is shown the anvil assembly for producing the top
and bottom seals and the beak spout for the pouch of Figure 1. This unit
simultaneously forms the bottom seal of a lower pouch and the top seal and
the seals around the beak spout of an adjacent upper pouch. After these
seals are formed, the pressure between the ultrasonic horn and anvil is
increased, and the thermoplastic material between the bottom seal of one
pouch and top seal of another pouch and the excess material in the area of
the beak spout is severed. This ultrasonic sealing unit must have
sufficient energy to complete the seal and to thin the material for
subsequent severing of the thermoplastic film.
The shape of the surfaces also produces a thinning of the film An
ultrasonic frequency of 10 KHz to 70 KHz is preferred, with a frequency of
about 20 KHz to 40 KHz being most preferred.
The unit shown in Figure 4 is the anvil assembly 40 of the transverse
ultrasonic sealing unit. This unit consists of base support plate surface
41 which supports the top and bottom sealing anvil 42 and the beak spout
sealing anvil 43 Each of these anvils is raised above the surface of the
support p1ate to the~SQne extent. The ~ealin9 anvil ~3 ¦las a surface ~ O 4 8 9 2 8
which contacts the corresponding ultrasonic horn surface and the anvil 43
has a surface 45 which contacts the corresponding ultrasonic horn surface.
The base plate can be cooled by a fluid flowing through the plate via ports
46 and 47.
The contact surfaces ~4 and 45 are in the form of an edge and are
effective to produce the desired seal and subsequently to cut the film.
Consistent with the desired seal this surface will preferably be an edge.
The shape of the anvils of this ultrasonic sealing unit is shown in more
detail in Figure 5. The exterior angle A of anvil with the horizontal
axis, which in Figure 5 is also the base plate, is about 120 to 160, and
preferably about 135 to 150. This results in interior angles of about
20 to 6G and preferably about 70 to 45. The anvils are shaped to
produce effective sealing and effective severing of the film after sealing.
During the sealing operation, the pressure between the anvil and ultrasonic p
horn, is about lO kg/cm2 to 50 kg/cm2. This is increased to about 20
kg/cm2 to lO0 kg/cm2 for severing the film. The increased pressure is
dependent on the pressure that is utilized during the sealing operations.
The pressure can be increased by the anvil being moved against the
ultrasonic horn or the ultrasonic horn being moved against the anvil.
In Figure 6 there is shown the complete transverse ultrasonic sealing
unit for forming the top and bottom pouch seals and the beak spout seals.
This consists of essentially the anvil assembly 40 and ultrasonic horn 35.
This unit produces the top and bottom seals as well as the beak spout
seals. This ultrasonic horn consists of flat surfaces 36 to contact the
shaped surfaces 44 and 45 of the anvil. The ultrasonic energy is
transferred from the booster 37 to the horn. However as noted above, the
ultrasonic horn can be shaped to function to sever the film rather than the
:
: ::
~nvil being shaped toSQ~-ve this pll~`pOSe. Iit~lel~ the ~ nasonic horn ~0~8
~vil must be shaped to provide for a severing cf the ~ilm a~ter sealing.
If the ~ltrasonic horn is to function to sever the film, the contact
portion 36 of the ultrasonic horn must be of the shape as is illustrated
for the anvil. In such an instance the anvil will have a flat surface.
The ultrasonic horns can be constructed of titanium, Monel alloys,
aluminum or aluminum alloys. Titanium is an effective metal for ultrasonic
horns. The anvil can be of the same or a different metal from that of the
ultrasonic horn. The anvil can also be a stainless steel. The anvil
should have a low wear rate.
Figure 7 sets out a preferred form/fill apparatus. In this
form/fill apparatus the pouch of Figure l is formed and filled in a top
side down arrangement. That is, the beak spout and top seal are formed
first in the lower portion of the tube, the partially formed pouch filled,
and the bottom seal then formed. This arrangement is needed for the
formation of a pouch with a beak seal since the pouch must be filled after
the beak is formed. The film 51 is unwound from supply roll 50. This
passes down over tension roller 52 and over directional rollers 53 and 54.
The film then passes over roller 56 and downward to the form/fill section.
At 57, the film is formed into an open tubular shape. Shaper 57 is
supported by fill conduit 59 which receives a product to be packaged,
usually a liquid product from supply conduit 58. The film passes in an
open fashion by supply conduit S8 to the seam forming and longitudinal
sealing section 60. In this sealing section, guide 61 directs the film
into a shape so that there is an overlapping longitudinal sea~ for sealing
by the longitudinal ultrasonic sealing unit. The longitudinal ultrasonic
horn 63 receives ultrasonic energy from transducer 62. The anvil is
_al~rled by ~ill cond~ '>9. The film, now in a tubu ~ r ~orm, exits 2048928
,ngitudinal sealing section 60 and is movec downwardly by controller 64.
Controller 64 moves the film intermittently and stops film flow in order to
permit the sealing, cutting and filling operations. This controller
includes drive rollers 65 which move the film.
In the region below the controller, the tube is transversely sealed at
67. This is accomplished by the lower sealing unit as illustrated in
Figures 4, 5, and 6. This lower sealing unit will form the top seal and
the beak spout on the tube to form an open ended pouch. This pouch is in
an inverted arrangement.Simultaneously, a lower pouch that has been filled
receives a bottom seal. This all occurs at a first pressure between the
ultrasonic horn and the anvil and the application of ultrasonic energy. At
a second higher pressure of the ultrasonic horn against the anvil, and
without the application of ultrasonic energy, the film is cut to separate
the lower pouch and to cut the film to form the beak spout on the upper
pouch. In this sequence, after the top seal and beak spout are formed, a
pouch is filled from spout 66 of fill tube ~9. After the filling step, the
filled pouch moves downwardly and the transverse ultrasonic sealing unit
goes through another cycle of making the bottom seal of this pouch and the
top seal and beak of another pouch.
As has been noted, the flow of the film is intermittent. The flow of
film is stopped for the sealing operations and for pouch filling. Thus,
each time that the film flow stops, longitudinal ultrasonic seàling unit 63
is actuated as is transverse ultrasonic sealing unit 67. Also, while the
film flow has stopped, the pouch that has been formed is filled.
Essentially any film which can be welded by means of ultrasonic energy
can be utilized to form the present pouches. The particular thermoplastic
fi~ms can be either amorphous or crystalline. Suitable films include those
Or acrylic copoly~er~J cellulosic, phenylerle oxi~e, ~ ycarbonate, and 2048928
Polystyrene. Generally, crystalline resins are not as easily sealed using
ultrasonic techniques as amorphous resins. Crystalline films are more
rigid. Flexible films are preferred. However, acetal resins,
fluoropolymer resins, nylon resins and polyester resins can be utilized in
ultrasonic sealing techniques. A preferred film is one which contains at
least one layer of ethylene-vinyl acetate. The other layer or layers can
be a polyolefin such as polyethylene, polypropylene, polybutylene and
polybutadiene.
The pouches which can be formed using the present ultrasonic sealing
techniques can be of essentially any size. Howéver, the preferred sizes
range from about 50 cc. to about 2 liters in size. These are the sizes
that are conveniently handled with regard to this type of packaging
technique. The substances which are packaged within such pouches include
personal care products, household care products and foods. In the category
of personal care products, there are liquid soaps, shampoos, and lotions.
In the household care area, there are cleaning and polishing compositions,
fabric bleach compositions, and general purpose soap compositions. In the
food area, there are included various sauces, gravies, fruit flavorings and
the like.
EXAMPLE 1
This example illustrates the forming and filling of pouches using the
form/fill apparatus of Figure 7.
A polyethylene/ethylene - vinyl acetate coextruded film 51 having a
thickness of 0~20 ~m and a width of 16 cm is fed from supply roll 50 to a
pouch forming and filling machine via rollers 52, 53, 54, and 56. The film
is fed in a continuous strand 51 to a form/fill machine. As the film
passes through an upper shaper die 57, it is formed into a tubular shape
13
.
~t~ an ov-?rklppin9 loh~iludillal ~eam. The t`ilm over~rS about lO 20~928
f ilm passes between a longitudinal ultrasonic horn 63 and stationary
fixture. The impinging pressure is about 40 kg/sq. cm. The flow of film
ceases momentarily during this operation. The side seam is formed by the
film edges being held between the longitudinal ultrasonic horn and the
anvil (as shown in Figure 2~ and an ultrasonic energy at a frequency of 20K
Hz applied. At the same time, transverse bottom seals are being formed at
the lower portion of the tube as is a beak spout. This is formed by a
transverse ultrasonic horn and mobile anvil assembly 67 ~as shown in
Figures 4 to 6). At the same time that the top seal and beak spout are
formed on this pouch, a bottom seal is being formed on a lower pouch which
has been filled. An ultrasonic frequency of 35 KH2. iS used to form these
seals. The impinging pressure of the transverse ultrasonic horn and anvil
assembly during sealing is about 40 kg/sq. cm. After the side and top
seals along with beak spout are formed on the present pouch, the newly
formed pouch with an open bottom is filled with 250 cc of bleach. The
lower pouch which has undergone closure sealing has been severed and is
conveyed to packing. The severing is accomplished by increasing the
impinging pressure of the ultrasonic horn against the stationary fixture to
about 90 kg/sq. cm. No ultrasonic energy is applied at this time. This
then completes a machine cycle. This cycle is then repeated.
The sealed seams of a representative number of pouches are tested in a
pressure tester. The pressure tester has a stationary and a moveable
platen. A sample is placed between the platens and the pressure on the
pouch increased. A burst strength of greater than 150 kg indicates an
acceptable filled pouch. The pouches consistently exceed lS0 kg.
`:
