Note: Descriptions are shown in the official language in which they were submitted.
. `~ l 1131~60
MANUFACTURE OF SEALED-END TUBULAR THERMOPLASTIC ~ET
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BAGGING
One sort of tubular netting of thermoplastic material
which may be used to make the product of the present
invention also is the raw ~aterial for the process des-
cribed in the U.S. patent of Kebekus, et al, 3,017,314,
issued January 16, 1962. In Rebekus, et al, the netting
is advanced through a work station where it is radially
constricted at two axially slightly spaced points and
periodically is simultaneously heat welded and severed
between these two points, then cooled -- thus adjacently
making the bottoms of what is to become two bags.
A recently issued V.S. patent of Pelster, et al,
4,091,595, issued May 30, 1978 shows a manufacture at
the bag filling station, of plastic netting bags made
. 15 from the preferred material, Dupont's Vexa~ plastic mesh
tubing. ~ ~
Although the resulting kind of bag has myriad uses,
presently it is best known to most consumers as the plastic
netting bag in which grapes, oranges, onions and the like
often are sold in supermarkets. Marbles are typical of a
non-food product which can be packaged in similar material.
This kind of bag is in increasing demand for use in place
of plastic film bags, for packaging products which do not
require envelopment by a complete vapor barrier.
A further use is to permit foodstuffs and the like
to be soaked in a processing fluid while individual quanta
thereof are segregated into individual fluid-permeable
packages. Typical i~ the marination of pre-sorted, pre-
selected amounts of cut-up chickens, e.g. the whole or a
proportional amount of the cut-up chicken which will be
cooked in the same batch at a fast food retail store which
features fried chicken.
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1131~0
In small-scale packaging operations, individual bags
such as are produced using hot knife thermal welding with
simultaneous bag cut-off, are conveniently used. With
larger scale operations, particularly for use with produce-
bagging machinery which is at least partially automated,often the most efficiently useful product is a continuous
"rope" of potential netting bags produced by gathering and
sealing the netting strands every so often along the length
of the rope. The rope can be payed off a roll and succes-
sively cut through next to each seal to successively make
- individual bags. In other words, for such a product, sever-
ing operation is not performed simultaneously with the
gathering and sealing, and may be perfonmed, e.g. by a
customer at a field location, rather than by the manu-
facturing entity which made the intermittantly sealed rope.
Further, the spooled, întermittantly sealed rope of tubular
thermoplastic netting material may serve as a supply of
bags to an automated bagging machine (not part of the pre-
sent invention) which successively pays out, fills, closes
and severs the leading bag of the rope. A similarly desir-
able product is a boxed coil of such rope of bag precursors
in series. Another, is a transparent package of a plurality
of individual, empty bags. The package having a grab-hole
in its side wall through which the bags may be individually
withdrawn for filling.
Paxton, U.S. patent 3,732,662, issued ~ay 15, 1973
shows packaging goods into tubular netting using a "sausage-
stuffing" technique. When the tube terminal portion holds
a full quantum of goods, it is manually spun, mechanically
clamped, and ¢ut off.
Herrell, U.S. patent 3,780,488, issued December 25,
1973 shows that it is known to seal a non-twisted, tubular
thermoplastic film, simply gathered and clamped between an
ultrasonic horn and anvil to form a package end.
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It has been found that if one radially gatheringly
condenses a tube of thermoplastic netting and attempts to
make a seal using an ultrasonic horn and anvil, quite
commonly two, three or several separate seal nuggets and
sometimes a fray are formed. These are not integrated into
a separate seal and results in bags having one or more weak
sections or gaps in their botto~s. While, but for having
an undesirably nonuniform appearance, such bags could be
used to package larger items, such as large onions, which
_ 10 are not likely to fall out through small gaps in the bag
bottom, these bags cannot be used to reliably package
small items such as grapes or marbles.
summarY of the Invention
~ tube of thermoplastic netting is drawn through a
work station in a radially collapsed, condensed condition.
At the work station, the netting is angularly twisted to
rope-like form, to increase its bulk density and, in such
condition, is drawn between the die and platen of an ultra-
sonic welding horn. Periodically, the die and platen
momentarily bear against a succeeding short length of the
twisted, condensed rope-like form making a fused seal
nugget integrating all strands of the netting at that
site. The resulting product may be a long length of such
tubing, having such a seal every so often, or a plurality
of bags formed from the intermediate product by making one
transverse cut through the netting tube beside each seal
nugget.
The present inventor~ have found that if the condensed
tubular netting also is twisted significantly, when an
ultrasonic seal i~ made, all of the netting strands are
consolidated at the site of the seal into a monolithic
seal nugget with no separated strands and no frays. The
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material resulting from being sealed in accordance with the
present invention may be fully cut across next to each
seal by the manufacturer into individual bags; or it may
be partially cut through fully across its width next to
each seal to make lines of weakness that will permit a
customer to sever the lead bag from the rope by giving it
a sharp tug, or the intermittantly transversally sealed
rope may be sold in a spool-wound, coiled-in-box or
similar form with neither full nor partial severing, e.g.
when the severing step is to be conducted on the custo-
_ mer's bagging machinery.
The principles of the invention will be further dis-
cussed with reference to the drawings wherein preferred
embodiments are shown. The specifics illustrated in the
drawings are intended to exemplify, rather than limit,
aspects of the invention as defined in the claims.
Brief DescriPtion of the Drawings
Figure 1 is a schematic diagram of a process for
producing bagging in accordance with principles of the
present invention;
Figure 2 is a somewhat schematic top plan view of a
generalized form of the apparatus;
Figure 3 is a side elevation view of apparatus for
carrying out important intermediate steps in the process;
Figure 4 is a top plan view of the apparatus shown
in Figure 3;
113~6~)
Figure 5 is an enlarged sclae side elevation view, with
portions broken away and sectioned, of a portion of what is
shown in Figure 3;
Figure 6 is an enlarged scale top plan view, with
portions broken away and sectioned of what is shown in Figure 3;
Figure 7 (located on page with Figure 1) is a fragmentary
vertical transverse sectional view of the welding horn and platen
forming a seal nugget between them;
.
Figure 8 is a perspective view of the apparatus, from its
output end, when the apparatus is equipped for severing the
intermittantly sealed nettingstock into individual bags aligned
in a series of transversally oriented individual bags on a
take away conveyor;
Figure 9 is a fragmentary frontal perspective view of a
single netting bag produced in accordance with the present
invention;
Figure 10 is an intermediate portion of a rope of netting
bags pFoduced in accordance with the present invention;
Figure 11 (located on page with Figure 2) is a package
of a group of the Figure 9 bags, which permits withdrawal of
individual bags through a grab hole provided in the package
side wall.
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General Description
As illustrated in Figures 1 and 2, in a preferred
embodiment, the process may be conducted as follows.
A continuous tubular rope 10 of thermoplastic
ne~ting, such as Dupont's Vexar is unreeled from a spooled
supply 12 and is guided through a set of intermittantly
rotated feed rolls 14. Downstream, the rope of netting
passes through another set of coordinately intermittantly
rotated feed roll 16.~
Between the two sets of feedrolls 14, 16, are a
twisting station 18 and a sealing station 20.
At the twisting station, after the rolls 14, 16 have
stopped advancing the rope 10, and thus are holding a
length L of the rope 10 gently tensioned therebetween,
15 the rope length L is given an angular twist at the station
18, of a sufficient number of turns as to substantially
maximally radially condense the rope length L, at least
in the vicinity of the sealing station.
While the number of twists is maximized at the twisting
20 station, and progressively decrea~e upstream and downstream
of the twisting station, the sealing station 20 is so close
to the twisting station that substantially maximal conden-
sation persists at the sealing stations. The number of
turns needed is a function of the length L and the relative
25 locations of the twisting and sealing stations within it,
and of the initial condition of the incoming feed stock of
thermoplastic tubular nettlng 10. Typical, is the produc-
tion of a ten-turn twist ~3600 degree) at the twisting station
18 in order to provide a seven turn twist (2520 degree) at
30 the sealing station 20.
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At the sealing station, an axially short segment of
the substantially fully radially condensed feed stock,
while being confined against laterally spreading out, is
contacted with a sealing device, preferably an ultrasonic
sealing horn in order to melt all of the strands in the
segment into a massive seal nugget. The sealing device
withdraws in time for the next unit advance of ~he feed-
stock.
That advance carries the newly formed seal downstream
- 10 to a region where the thermoplastic tubular netting, con-
verted by having said seal may be simply wound up again,
or subjected to a cutting operation at a cutting station
22.
At the cutting station, the converted feedstock is
cut across the width thereof beside the seal nugget. The
cutting operation takes place between succeeding intermittant
advances of the feedstock. The cut is either partial, so
as to leave the rope physically intact, yet with a line of
weakness along which, if the rope is grasped and pulled,
it will sever, or is fully cut in two.
If the cutting is partial, the thus further-converted
rope is reeled up and packaged, e.g. as a coil in a carton.
The customer of such a product, typically a grocery chain,
can supply this product, e.g. to its produce departments,
where the cartons may be hung or otherwise stationed where
produce is being bagged. The bagger need only pull out
enough of the converted rope as to pass a seal nugget, then
sharply tug in order to sever the rope at the pre-cut line
of weakness beside the seal nugget, thus separating a bag
from the leading end of the converted stock.
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~ ~ - 8 ~ 113i~60
~ If the coiled converted stock is sold without such
partial pre-cutting, it may still be packed in a similar
way. However, in such an instance, the user is provided
with a razor knife or the like to cut the rope next to
each seal nugget in order to separate bags from the con-
verted rope, as needed.)
As generally illustrated in Figure 2, in the preferred
embodiment, at the cutting station, the converted rope is
completely severed next to each succeeding seal nugget in
order to serially produce individual bags at the downstream
end of the converted rope.
9ecause the cutting station 22 is downstream of the
feed rolls 16, an e.g. transparent tube 24 is provided so
that it longitudinally extends between the downstream side
of the rolls 16 and the upstream side of the cutting station
22. The converted rope is thus pushed downstream by the
rolls 16, and it passes through the tube 24, which keeps
the rope on target heading into the cutting station 24.
In the presently preferred embodiment the cutting
station includes knife means in the cutting station 24,
which cuts across the converted feedstock just upstream of
each succeeding seal nugget. Thus each bag B, as it is
created, is already mostly past the cutting station, so
that it may drop from the cutting station through a baffle
box 26 and onto the upper run of a horizontal, endless
conveyor belt 28. The purpose of the baffle box 26 is
to lay each succeeding bag B onto the belt 28 90 that it
extends crossw~e of the belt.
As opposed to the feeding at 14, 16, the sealing at
20 and the cutting at 22, all of which are carried out inter-
mittantly in the preferred embodiment, the conveying at 28
is continuoue. Thus, the succession of completed bags is
carried past an inspection station 30 where, e.g. a human
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3 ~3~5~60
ins2ector is available for a culling from the line any
damaged or imperfectly made bags.
Downstream from the inspection station, the bags B
drop into a container such as a carton 32 that is supported
on a weighing platform 34. The latter may be of a conven-
tional electronic sort, in which a preselected gross weight
figure may be dialed into the weighing apparatus. Such a
weight would be one that equates to the weight of the empty
carton plus the weight of the number of bags which are to
be packed in that carton. When the dialed-in weight is
reached, as succeeding bags roll off the forward end of the
conveyor belt 28 and into the carton 32, a belt, buzzer or
other indicator is actuated, so an attendant may replace
the filled carton with an empty one.
A suitable, utterly conventional control system (not
illustrated) may be employed for coordinating the starting
and stopping of the intermittantly operated elements, which
may be powered by utterly conventional means (not illustrated)
such as D.C. electric motor(s) with appropriate drive
train(s), pressurized fluid-powered piston and cylinder
arrangement(s), and the like.
Detailed Description of the Presently
Preferred Embodiments of the Invention
Presently, E. I. Dupont de Nemours & Co. of Wilmington,
Delaware markets as tubular packaging material and as
stock therefore ~pool-like coiled supplies of tubular
thermoplastic netting which is very diaphanous, so tha~
when it is made into bags and radially outwardly expanded,
much produce or other articles may be contained within the
tube, using very little plastic material. Similar material
is available from other manufacturers. A typical plastic
for the material is polyethylene or polypropylene.
.
- 10 -11~ 6()
The aforementioned U.S. patent of Pelster, et al
shows Vexar thermoplastic mesh tubing spooled in the manner
in which it is customarily supplied to converters or
packagers. As is notable from Pelster, et al, the thermo-
S plastic mesh tubing, as received, is in a significantlyradially condensed condition, but it is not significantly
angularly twisted. Thus, Pelster, et al are enabled to
simply pay the supply convolutely off the roll and radially
expand it over a mandrel in their process in which expan-
sion at the cutting and sealing station is an essential.
Conversely, in the present process, at the sealingstation, the supply is wanted in a substantially fully
radially condensed condition, in which further condensation
from the as-unreeled not significantly twisted condition
is achieved by applying an angular twist to the stock being
unspooled. One way that a certain, but usually insufficient
amount of radially condensing twist can be imparted to
the stock being unspooled is to pull it axially off one
end of the coiled suppiy without rotating the supply
spool. That imparts one twist per instantaneous length
of coil. However, as the coil diminishes in diameter the
number of complete twists thus imparted per unit length
of stock will increase. But beyond this continuously
changing va~iable, the amount of twist thus imparted in
most instances would produce insufficient radial condensa-
tion to permit secure and complete sealing at the ultra-
sonic horn.
Accordingly, such an uncoiling method would generally
not be used alone, and, in fact, when more convenient to
do so, the stock may be uncoiled convolutely, exactly as
in Pelster, et al.
11 - 113~;0
Although, in theory, it might be possible to obtain
the spooled tubular netting feedstock in an already maxi-
mally radially condensed, significantly angularly twisted
condition, there are reasons why, so far, that has proved
impractical. The netting is produced by extruding a tube,
intermittantly slittinq it, and longitudinally stretching
it, then reeling it onto a spool, all in a continuous
process. Producing a twist would call for putting the
winding-up apparatus on a spider which revolves angularly
about the wind-up path. Also, during storage on the spool,
_ the feedstock would tend to take a set in its twisted
condition, making later opening and filling of the resulting
bags too difficult. There are conceivable economic condi-
tions, however, under which pre-twisting could become
attractive.
At the stage depicted in Figure 3, the incoming stock 10
of thermoplastic tubular netting has been uncoiled from
a spooled supply, either convolutely, with spool rotation,
or over an axial end of the spool, without spool rotation.
Although it is possible to conduct the process using
a single, condensed tube of feedstock, it is considered
generally much more economical to conduct the process
simultaneously on several parallel feedstocks. Thus, in
the drawings, e.g. Figure 3, it will be noted that the
process is being simultaneously conducted on six parallel
feedstocks, grouped in twos. However, six is not a magic
number; more or less feedstocks than illustrated could be
processed on one correspondingly equipped set of apparatus.
Figures 3 and 4 show the twisting station 18 and the
sealing station 20 disposed next to one another intermediate
the upstream and downstream sets of feed rolls 14 and 16.
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l 1131~0
Figure 5, shows the twisting station 18 and the sealing
station 20 by themselves and in more detail.
At the twisting station 18, each rope of feedstock
passes through a twisting fixture 36. The twisting station
includes a frame 38, which includes an upstanding plate 40
having a plurality of circular openings 42 therethrough,
one for each fixture 36. The fixtures 36 each comprise a
pulley element 44 and a drag element 46, both preferably
molded of lubricous plastic material such as nylon, fitted
together through the hole 42 from opposite sides of the
plate 40, and held together by a shoulder screw 48. The
association is such that although these parts are held
together, the pulley element 44 is free to turn relative to
the drag element 46. Opposed axially facing surfaces 50,
52 and radially outer surface 54 provide simple bearings for
rotation of the twisting fixture relative to the twisting
frame. Of course more elaborate bearings can be provided
where desired. At correspondingly eccentric sites, openings
56 and 58 are formed respectively through the pulley element
44 and the drag element 46. The feedstock 10 is threaded
through both openings 56 and 58. This fact, and the light
tension provided between the feed rolls 14, 16, ensure that
the respective openings 56 and 58 in the same twisting
fixture remain generally in coaxial alignment, at a lateral
offset from the rotational axis of the respective twisting
fixture 36.
The fit of the feedstock through the openings 56,58 when
these openings are aligned is a snug yet sliding fit, some-
what like that of a shoelace in a shoe vamp eyelet.
Each pulley element 44 is provided with an external
radially outwardly opening circumferential groove 60. A
drive belt 62 is entrained about each pulley element, in
~ 60
the respective groove 60 thereof. Thus, when the drive
belt is intermittantly driven, all of the pulley elements
44 are rotated by the same angular amount.
Because the drag elements 46 are not rigidly, drivingly
connected to the respective pulley elements 44, they tend to
angularly trail the respective pulley elements during
rotation. The result is that as rotation is begun, a slight
angular offset is created between the normally coaxially
aligned openings 56, 58. Thus, the respective feedstocks
lO are slightly pinched at the respective interfaces 56/58.
The pinching action is sufficient to ensure that as each
twisting fixture 36 rotates, with the respective feedstock
lO eccentrically held, each respective feedstock is provided
with a number of angular twists, sufficient to substantially
fully radially condense the respective feedstock in the
vicinity of the sealing station.
After the twisting fixtures have been rotated, the
sealing apparatus at the sealing station 20 is operated
to form a seal nugget on the short segment of each angularly
twisted rope of feedstock that is within the sealing station
at that time.
Then the sealing apparatus retreats from the thus-
nuggeted feedstocks, and the feed rolls 14, 16 are operated
to advance the respectiye feedstocks by one bag length.
At this time, the twisting fixtures are not rotating, so
the respective openings 56, 58 tend to coaxially align.
Thus, while the fixture~ grip and hold the feedatocks while
the feedstocks are being angularly twisted, the feedstocks
may be easily pulled forward during the feedstock advancing
step, as the gripping action of the twisting fixtures
becomes immediately relaxed.
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1 In the presently preferred embodiment, the sealing
accomplished at the sealing station 20 is accomplished by means
of frictional heat created in the molecular structure of the
feedstock, due to the temporary application of an ultrasonic
sealing horn to a confined segment thereof.
Ultrasonic sealing devices ~ se, having reciprocable,
automatically controlled horns per se are well known; one commer-
cially available device that is suitable for use in the process
of the present invention is Branson, Model 400 Series manu-
factured by Branson Sonic Power Co., of Danbury, Conn.
As available, an ultrasonic sealing device 64 has a housing
66 within which a crystal (not illustrated) is excited to produce
ultrasonic vibrations, which are delivered to an output head 68
that is mounted on the housing 66 to be reciprocated vertically
in response to control signals. Typically, the head 68 has
one or more ultrasonic sealing horns 70 mounted thereon, these
being typically spatulate elements designed to focus the
ultrasonic waves travelling therethrough, toward an axially
outer end (usually lower ena) working surface 72.
In practice, it is common in ultrasonic sealing operations
to use an ultrasonic sealing device in combination with a
support fixture for properly holding and supporting the material
that is to be sealed. The ultrasonic sealing horn and
support fixture associate in use approximately as respectively
do the movable platen and fixed bed of a press.
In the present instance, the ultrasonic sealing device 64
output head 68 is shown having one ultrasonic sealing
horn 70 of generally the same shape as a flat-bladed screw-
driver head, with the respective working surfaces 70 at the
respective lower ends. This ultrasonic sealing horn
- 15 ~ 60
are mounted to move vertically toward and away from three
xespective support fixtures 74.
Each associated ultrasonic sealing horn 70 and support
fixture 74 pair is juxtaposed to operate upon two feedstocks
10, so the three pairs together serve all six feedstocks.
~s aforementioned, this doubling up and the particular
number ~f feedstocks is subject to variation to accommodate
processing less or more feedstocks, or the same number of
feedstocks in a different arrangement, e.g. one horn for
all three support fixtures; two groups of three instead of
three groups of two; two horns for one support fixture, etc.
Some important modifications have been made in order
to suit c~mmercially available ult-asonic sealing equipment
for use in the process of the present invention. What
follows are some of the details, set forth with respect to
one ultrasonic sealing horn and one support fixture.
The support fixture 74 is illustrated in Figures 3 - 7,
and its details are most apparent from Figures 5 - 7.
In general, the support fixture 74 is constituted by a
short length of rectangular-sectioned metal bar stock having
a deep slot 76 running axially centrally along the length
of the upper side thereof, bordered by two thus-created
upstanding flanges 78. Somewhat below tangency with the
floor 80, two openings 82 are drilled horizontally trans-
versally through the bar stock so that most of what isremoved to make the holes once was part of the flanges 78,
but a small amount once was part of the bar stock at and
just below the floor 80. The two laterally spaced openings
82 enter through the upstream face 84 of the fixture 74
and exit through the downstream face 86.
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In order to create somewhat larger-volume ~olding
cavities 88 in the support fixture, the shallow concave
grooves created in the floor 80 when the openings 82 are
drilled may be enlarged, as illustrated, by milling out more
material. However, it is preferred that the profile of
each molding cavity 88 (Figure 7), remain generally upwardly
cylindrically concave.
As a further modification, by preference, a trademark
or other logo, e.g. of the converter, the bag manufacturer,
10 _ the netting supplier, the bagging material customer, or the
produce marketer, may be provided in relief in each molding
cavity 88 as illustrated at 90. Thus, as each seal nugget
is formed, it is provided with a raised logo 92 (Figures 9
and 10) which helps make the bag traceable as to its source.
lS The logo 92 may be a pictographic design, or character
symbols such as numbers and/or letters, or combinations of
such. (What is illu~trated is a double arrow logo indicating
origin in Gallaher, Kantlehner and Associates, Inc. of
Louisville, Kentucky.)
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2~ In practice, the support fixture 74 is mounted on a
sealing station frame 94, t,hat in turn, is mounted on the` `
main frame 96 of tpe device of the invention, just down~
stream from the twisting station 18.
The ultrasonic we~lding horn 70 is modifie~ by havin~
a roughened fi~ish~-9~ on the working surface 72 thereof.~ ;
By preference! t~he roughened finish is a medium female
knurl 98~,othe~r types of rou~ghening, such as sand-blasting
cau~d be used. ~he main purpose i8 to effectively overcome
the tendency of the ultrasonic vibrations, when transmitted
- 30 to the feedstock to undesirably lateFally~spread the feed-
- stock. Too often, if the working surface 72 were smooth,
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some strands of the feedstock would be displaced laterally
and not be fully consolidated into the seal nugget.
As an elaboration, the knurling or other roughening
may incorporate a logo to serve in place of or in addition
to the logo 90.
j By preference, what happens at the sealing station is
the following. Starting from a point in time at which the
horn 70 is withdrawn from the fixture 74, the feedstock
has been advanced another bag length, and the twisting
station has operated to angularly twist the feedstock now
at the twisting and sealing stations sufficiently to sub-
stantially fully radially condense the feedstock segment
100 that is now superimposed upon a respective molding
cavity 88, the ultrasonic welding horn 70 is indexed down-
wardly so that it enters the slot 74 and its working surface
72 comes into engagement with the feedstock segment 100.
The ultrasonic vibrations are initiated in the device 64
and transmitted to the horn, which is pressed down on the
feedstock segment 100, tending to force substantially all
of the feedstsck segment 100 into the molding cavity 88.
The energy of the ultrasonic vibrations quickly creates
such intense internal frictional forces in the thermoplastic
material of the feedstock sesment 100 that the material
within the feedstock segment melts into a single, integral
seal nugget N which incorporates substantially all of whatpreviously were the individual, though interconnected
strands of the netting 10.
At some running speeds with some plastic materials
and at certain ultrasonic energy levels, it may be necessary
to pause momentarily at this point in order to lead heat away
from the nugget, either into the metal of the horn or fixture
acting as a heat sink, or into cooling fluids which for
that purpose may be conducted through internal channels
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within the ultrasonic sealing horn 70 and/or through the
support fixt~re 74. However, the need for such measures,
the intensity with which they need to be applied, and means
for accomplishing the same are easily within the competence
of persons of ordinary skill in the the~moplastics molding
art.
As the $eal nugget is being formed, the proximity of
the sealing horn to the fi~ture, limited by engagement of
the horn working surface 72 with the shoulders lQ2 (the
floor sections 80 beside the molding cavity 88) or the near
approach of the horn surface 74 to the shoulders, limited by
small ear-like portions of the nugget which may spread
slightly laterally out of the cavity 88, yet remain contigu-
ous with the reaminder of the seal nugget N.
lS Once the seal nugget N has been formed, the horn 70
is withdrawn upwardly, out of the slot 76 and is ready for
the next cycle.
In the variations of the preferred embodiment in which
the end product of the process is either individual bags or
a con~erted feedstock rope with perforation lines of weak-
ness cut across next to each seal nugget, the cutting station
22 which is located downstream from the sealing station
operates respectively to make a full or an intermittant cut
beside the seal nugget N which was formed in the preceding
cycle relative to the seal nuqget that was just formed and
still resides at the sealing station 20. Then, it is time
for the feed rolls 14, 16 to advance the feedstock by another
bag length, bringing the seal nugget that was just formed,
to the vicinity of the cutting station 22 and a correspondingly
new quantum of feedstock into the twisting and sealing stations.
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Where, as shown, each converted feedstock is to be
completely severed into a succession of bags B, the pre-
ferred instrumentality for performing the cutting step
is a shear device. As shown, the shear device incl~des
5 a bed plate 106 with a stationary cutting edge 108 at
the downstream end thereof. A frame 110 over the bed
plate near the downstream end mounds one or more shear
knives 112 via guided vertically reciprocating means,such
as a pressurized fluid-powered piston and cylinder arrange-
ment 114 (the actuation of which is controlled and timed
together with the rest of the apparatus of the invention).
Accordingly, intermittantly, once during each cycle of
operation, while the converted feedstock is not in the act
of advancing, at a time when each converted feedstock rope
has one bag's worth protruding downstream past the sta-
tionary cutting edge 108 of the shear device bed plate,
so that on each such converted feedstock protruding por-
tion, there is a unitary seal nugget located just upstream
of that stationary cutting edge, the piston and cylinder
arrangement 114 is actuated to momentarily thrust the
shear knives down along the stationary cutting edge 108
in shearingly cutting relation therewith, thus lopping
from the downstream, leading end of each converted feed-
stock, a respective bag B.
With regard to Figure 9, each bag B is constituted
by a selected length of tubular thermoplastic netting,
open at a mouth M, and having a seàl nugget N fonming
a massive, substantially fully integrated closure for
the opposite end thereof. (The seal nugget N may be
right n at" the end of the bag B, or a short distance
downstream, typically one-half inch downstream, depending
on the spatial relation of the cutting station 22 to the
sealing station 20.) By preference each seal nugget N is
embossed in the process of its formation as aforesaid, with
identifying indicia typified both by the logo 92 and by the
medium male knurling 116 ~the latter an artifact of
.
~13~i0
-- 20 --
1 the medium female knurling 98 on the working surface 72. Any
of a number of means may be used to close the mouth once the
bag has been filled. No particular bag closure forms a part
of the present invention. Typically useful presently
available closures include hang tags stapled or adhered in
place, twist ties and bread wrapper closures (key-slotted tags).
In fact, the bag filler could use another ultrasonic welding
horn to seal filled bags closed).
Where the desired product is a continuous rope of what
will become bags B, as individuals are snapped off the leading
end of the rope along respective transverse lines of weakness
W formed beside each seal nugget N, e.g. just upstream of
each seal nugget, a convenient way of accomplishing that is
to replace the shear knives 112 with similar ones (not
illustrated), which make intermittant per~orations, rather
than a continuous cut.
Where the desired product is a continuous rope of what
will become bags B, as individuals are later cut off the
leading end of the rope at the point of use, e.g. using a
razor knife, the cutting station 22 simply may be deactivated
and the converted feedstock merely coiled and spooled,
cartoned or otherwise packaged for storage and/or shipment.
Referring back to Figures 2 and 8, and to the instance
in which the output of the apparatus is at least one, six
are shown, stream of a succession of individual bags B,
e.g. being generated by the six at the leading ends of con-
verted feedstock at the cutting station 22, the remainder of
the process will be described in somewhat more detail.
An axially forwardly and downwardly obliquely declining
somewhat convergent trough 116 is mounted on the main frame
96 so that it projects forwardly of the cutting station 22 from
below the level of the bed plate 106. Even as a row of
- 21 ~ 96~
bags B is about to be cut from the several laterally adjacent
converted feedstocks, the leading nugget-sealed ends are
drooping down somewhat into proximity with the trough 116.
Upon the occurrence of a cutting step, the resulting bags
fall into the trough 116 and slide down it into the baffle
box 26.
As shown, the baffle box 26 is an open top, open bottom,
downwardly convergent hopper constituted by peripheral up-
standing sidewalls 118 and endwalls 120. Inside the hopper,
baffle plates 122 protrude toward the center from the two
opposed sidewalls 118. Theb~fle plates preferably are flat,
but are adjustably mounted at different heights (e.g. via
pegs in adju~tment holes) so as to decline from the sidewalls
toward the center at various levels (typically 2-4). Each
lS bag B which enters the baffle box 26 through its open hopper
top tends to advance axially forwards and to fall downwards,
striking one or more baffles in the course of becoming
aligned horizontally and centrally of the hopper thereby, and
is thus fully laid out substantially straight. In substan-
tially that condition, each bag issues through the openhopper bottom and, e.g. falls a very short distance (typically
a couple of inches) onto the upper horizontal row of an end-
less conveyor belt 28.
~he conveyor belt 28 may serve yet another, or plural
other bag manufacturing devices, e.g. another device just
like the one 12 - 26, each of which ends with a respective
baffle box 26 over the conveyor belt 28, between the baffle
box 28 illustrated, and the inspection station 30.
At the inspection station, the succession of bags B
30 i8 monitored, possibly with automatic devices, but typically
by human eye, and any malfonmed bags spotted may be simply
culled from the line. Note that preferred orientation and
use of equipment relative to the inspection station places
.'' ~' ~' ' `~.
.
- 22 -
113~:~60
all of the bags in a single series of transversally stretched
out bags coming past the inspection station with the ~sealed
ends N nearest the inspector~
The bags which pass the inspection, upon being conveyed
further typically drop off the downstream leading end of the
conveyor 28 and into a carton 32 which is disposed on a
weighing device 34 that has a signalling system for indicat-
ing when a carton is full, as explained above.
Typically certain parts of the apparatus, such as the
baffle box 28, the chute 116 and the tubes 24 are made of a
transparent material, such as glass or clear plastic, so
that its throughput may be more easily monitored.
A typical length for the bags B is twenty-six inches.
A typical feedstock is Dupont's Vexar tubular thermoplastic
netting. A typical end product is a carton of 1000 individual
bags B,or a unitary coil of 1000 ba~ B precursors, each marked
by a seal nugget N indicating the bottom of what will become
a bag B when that bag is cut or snapped from the leading end
of the coil. Such coils typically may be sold spooled or
cartoned.
Another preferred form the product may take is shown
in Figure 11. Here, a group of individual bags B, typically
one hundred of them, typically all with like orientation
(like so many licorice sticks or soda straws) are sleeved
in a tubular sack S of clear plastic film having one
sealed shut end E, and a hang tag T adhered onto and closing
the opposite, formerly open end thereof. The tag T i9 pro-
vided with one or more openings O so that the package may
be conveniently hung next to a work sta~ion.
:
- 23 - 1 1 31 9 6 ~
As a further elaboration, the sidewall of the sack
S, perhaps six inches up from the lower, sealed shut end
E is provided, when the sack S is manufactured, with an
intermittantly cut through ring of perforations P which
define in their midst a grab-out closure G. In order to
use such a package, the worker hangs the package next to
their work station, grabs out and discards the grab-out
closure G, and thus creates a grab-out opening through
which bags B may be withdrawn as individuals. The
grab-out closure G typically is circular and three or four
inches across. _
It should now be apparent that the manufacture of
sealed-end tubular thermoplastic net bagging as described
hereinabove, possesses each of the attributes set forth in
the specification under the heading "Summary of the Invention"
hereinbefore. Because it can be modified to some extent
without departing from the principles thereof as they have
been outlined and explained in this specification, the
present invention should be understood as encompassing all
such modifications as are within the spirit and scope of
the following claims.
,, :
.,
,
~: ' . ' : '
- 24 - 1131~60
~hèsc elements should show in Figure 8
(OutPut end fragmentary perspective)
16 Downstream Feed Rolls
Sealing Station (partial)
22 Cutting Station
24 Tubes
26 Baffle Box
28 Conveyor Belt (partial)
64 Ultrasonic Sealing Device (partial)
96 Main Frame (partial)
104 Shear Device
106 Bedplate
108 Stationary Cutting Edge
110 Frame of Shear Device
112 Shear Rnives
114 Piston and Cylinder Operating 112 (partial)
116 Trough
118 Sidewalls of Baffle Box
120 Endwalls of Baffle ~ox
122 Baffle Plates
.; . '~
.
