Apparatus and method for fabricating containers

A pouch making machine which simultaneously creates perimeter seams for a plurality of pouches on a web and temporarily stores the seamed web in an accumulator at the conclusion of the seaming step, and then withdraws the web from the accumulator to sever the individual pouches from the web. The individual pouches are severed from the web by a cutoff knife that is moving at the same velocity as the web during the cut. The withdrawal of the web from the accumulator is carried on independent of the seaming step, except that regulating means is included to make the long term average web speed the same through the seaming step as through the cutoff step.

BACKGROUND OF THE INVENTION 
This invention relates to the fabrication of containers, for example, 
flexible sterilizable pouches intended for storing medical or surgical 
items. The invention is described in the context of such pouches, but the 
principles disclosed can be applied in other applications, as will be 
evident to those skilled in the art. 
One form of pouch commonly used for storing sterile items, and for other 
uses, consists of two similarly sized rectangular sheets seamed to each 
other around their peripheries, using heat and pressure. If intended for 
gas sterilization (e.g. ethylene oxide or steam) one of the sheets is a 
made from a porous material which is permeable to the sterilizing gas, but 
is impermeable to bacteria and the like. This membrane could be, for 
example, surgical paper or a spun olefin (such as is sold by the DuPont 
Company under the trade name of Tyvek). The second sheet is usually a 
transparent non-porous plastic sheet, such as polyethylene, which is 
impervious to both gas and bacteria. In pouches intended for radiation 
sterilization, neither of the sheets need be porous; both can be 
polyethylene, or other suitable material. 
A myriad of pouch constructions have been devised over the years, of which 
a great many are presently in commercial use. A number of examples of 
pouch designs can be found illustrated in U.S. Pat. Nos. 3,754,700, 
4,367,816, 5,549,388, and 5,551,781, and in many other patents. 
Whatever the style, pouches are usually made on a machine wherein the 
various required constituents of the pouch are supplied as webs from large 
rolls of the respective materials. As the materials are fed through the 
pouch making machine, the various webs which are used to create the pouch 
are brought into face to face contact, and the required peripheral and 
other seams are made. The seams are commonly made by pressing the areas to 
be seamed between a heated seaming iron (which has the form of the desired 
seam pattern) and a platen. Since it takes some time (generally between 
0.5 and 1 second) to create a seam in this manner, the web feed is made 
intermittent. That is, the web feed is stopped during the time the seaming 
iron is pressing the web layers against the platen, and after each seaming 
is completed the web is then moved to bring the next area to be seamed 
under the seaming iron. 
Other operations which may be needed to be performed on the materials 
making up the pouch, such as cutting openings in one or more webs, 
printing, etc., are synchronized with the seaming cycle. These operations 
may be accomplished while the seams are being formed, or while the web is 
being drawn between seamings, or in a combination of both. 
As noted above, pouch seams are most commonly made by the application of 
heat and pressure to the seam areas, and the present invention is 
described herein as though that method is being used. Under some 
circumstances, however, it may be convenient to make some or all of the 
seams using adhesives rather than heat to cause the various films to 
adhere, and it will be appreciated that the principles of the present 
invention, as described below can be used to fabricate pouches using 
adhesive technology in place of heat and pressure. 
After the needed peripheral and possibly other seams are made, a fresh web 
area is moved under the seaming iron, and the previously seamed area is 
moved to a cutoff knife where the completed pouches are severed from the 
web. The cutoff knife is not usually located immediately adjacent the 
seaming iron. For practical space reasons, normally there are one or more 
patterns of perimeter seams between the seaming iron and the cutoff knife, 
and one or more additional seaming cycles usually occur between the time a 
seam is made and the time that the just seamed section arrives at the 
cutoff knife. 
Cutoff knives generally operate much faster than do the seaming irons; for 
example, even before the present invention, knives operating at a rate of 
five cuts per second or even somewhat faster were available. The cutoff 
cycle in prior art pouch making machines is also synchronized with the 
seaming cycle. 
In order to achieve relatively high production, it is common to utilize 
seaming iron assemblies which can make the seams for many (for example, 10 
or more) pouches at a time along the length of the web. Hence, in such a 
machine, pouches are made in two consecutive timewise steps: 1) seaming a 
plurality of pouches simultaneously, and 2) sequentially cutting off 
completed pouches. Assuming a seaming iron ten pouches deep, if it takes 
one second to make the seams for the ten pouches, it will take about an 
additional two seconds to cut the pouches off the web (at a rate of five 
per second), for a total of three seconds to make the ten pouches. This is 
a theoretical rate of 200 pouches per minute. If the seaming iron were 
twenty pouches deep, the theoretical production would be 240 pouches per 
minute. The maximum possible theoretical production, even if the seaming 
iron were an infinite number of pouches deep, would be 300 pouches per 
minute, being limited by the cutoff rate of prior art cutoff knives (about 
5 cuts per second). In a copending application by the present inventor 
(U.S. patent application Ser. No. 08/824,817) means are disclosed which 
permits a production rate up to the capacity of the cutoff knife, even 
though the seaming iron is not of infinite length. 
The present invention improves the rate of production of pouch making 
machines by 1) providing a cutoff knife which can operate at a much faster 
rate than prior art knives, 2) not stopping the web while severing the 
pouches (i.e., causing the cutoff knife to travel with the web during the 
severing operation), and 3) permitting the cutting off of the completed 
pouches to proceed even while the web is stationary in the seam forming 
portion of the machine (while the seams are being created). 
It is an object of the present invention to provide a pouch fabricating 
machine and method which improves on the production rate obtainable with 
prior art pouch fabricating machines. 
It is another object of the present invention to provide a web cutting 
knife capable of much higher cutoff rates when compared to prior art 
knives. 
SUMMARY OF THE INVENTION 
In the pouch making method of the present invention, the seaming and cutoff 
operations are not done sequentially, as in the prior art, but are rather 
carried out simultaneously and continuously. Pouch production is therefore 
not a function of the sum of the amount of time it takes to create the 
seams and the time to sever the pouches from the web, as in the prior art, 
but rather, is determined by the time to achieve only one of these 
functions. Hence the production rate is inherently higher than in 
comparable prior art pouch fabricating machines. Additionally, the cutoff 
knife used in the present invention is capable of much higher speed 
operation as compared to knives of the prior art. 
In accordance with the present invention, the input webs are fed to a 
seaming iron, and the peripheral and other seams are made as in the prior 
art. But when the seams are finished, the web is not fed directly to a 
cutoff knife, as was done in prior art machines, but is rather fed to an 
accumulator which accepts the intermittently moving web, and temporarily 
stores it. The material entering the accumulator from the seaming 
operation is fed out of the accumulator, as required, to the pouch 
severing portion of the machine, where the pouches are severed from the 
web. The pouch severing portion of the machine draws material from the 
accumulator continuously (albeit, usually not at a constant rate) and 
severs the pouches without stopping the web. This is done through the use 
of a knife which moves in the direction of web travel (i.e., the machine 
direction) as it is cutting the web. It will be appreciated that avoiding 
the necessity of stopping the web to cut is of great advantage in terms of 
web handling, and permits greater production than has been heretofore 
possible. 
The timing of the seaming operation and the severing operation are grossly 
different, but because an accumulator is provided as a buffer between the 
two operations, both can function simultaneously. The seaming cycle 
requires the web to be stationary for approximately one second per cycle, 
whereas the cutoff cycle does not require the web to be stopped at all. 
While the long term average web speed past the seaming iron and the cutoff 
knife are the same, the instantaneous speeds are vastly different, the 
accumulator absorbing the short term differences in web travel. 
The production rate of machines made according to the principles disclosed 
herein is limited only by the web handling capabilities of the machine or 
by the maximum cut rate of the knife. Knives made according to the present 
invention can easily make 800-1000 or even more cuts per minute. Modern 
web handling techniques, including the use of servo motors and carefully 
programmed acceleration/decelleration profiles, make such production 
practical. 
The invention is described in greater detail in the below detailed 
description and in the accompanying drawings, from which a more 
comprehensive understanding of the invention may be had.

DETAILED DESCRIPTION OF THE INVENTION 
Words in this document are generally used in accordance with their ordinary 
meanings, else their meanings are evident from the context or are defined. 
For convenience and in order to aid understanding, the phrase "machine 
direction" is used to refer to the direction of motion of the web as it 
passes through the fabrication process, "seaming iron depth" is intended 
to refer to the number of pouches in the machine direction seamed on each 
activation of the seaming iron, and "mesh" is used to indicate a scissors 
type cutting motion between two adjacent blades. Other definitions appear 
in the text as the occasion arises. Finally, while the following 
description is couched in terms of a "pouch", it should be understood that 
the terms "pouch", "container", "package" or similar term used in this 
document are meant to encompass any or all of the others, the particular 
word used in a particular case being a matter of linguistic style. 
FIG. 1 is a schematic side view of a pouch making machine embodying the 
present invention. The construction of pouch making machines in general is 
well known, so that constructional details are unnecessary to convey a 
knowledge of the invention to those skilled in the art. For illustrative 
purposes, a machine is shown which produces a conventional "chevron" 
pouch. Such a pouch consists of two rectangular sheets seamed together 
around three of their four sides, the fourth side seam being made after 
the pouch is completed and the desired contents inserted. The seam on the 
side of the pouch opposite the omitted seam is in the shape of a chevron, 
hence the name. 
While a machine embodying the principles of the present invention can be 
made wherein the seaming iron is only one pouch deep, best advantage of 
the invention will be had if the seaming iron is at least two, and 
preferably many pouches deep. The depth of the seaming iron actually used 
is a matter of economics and convenience; any desired number can be used 
in connection with the present invention within the constraints of space 
and practicality. Similarly, the seaming iron may be any number of pouches 
wide, as is economical under the circumstances. The following description 
will assume that the seaming iron is only one pouch wide, but it will be 
appreciated that this is an arbitrary choice for convenience in 
explanation. If the seaming iron were more than one pouch wide, it would 
be necessary to slit the web apart between the pouches before the final 
cutoff step, but otherwise the explanation of the process would be 
identical to that which follows. 
As seen in FIG. 1, two webs of sheet stock 11 and 12 are fed into the pouch 
making machine from rolls 13 and 14. The webs 11 and 12 are drawn (under 
tension) into the machine by rollers 15/16. Web tensioning devices are 
well known in the art and hence are not described here. One or both of 
rollers 15/16 are driven by motor 17. The motion is intermittent in that 
the webs are drawn rapidly into the machine for a period of time, and then 
the motion stopped for some other period of time to allow the perimeter 
seams of the pouches to be made. The seams (112) are preferably created by 
pressing the webs between hot seaming iron 18 and platen 19. The seaming 
iron 18 is pressed against platen 19 by one or more hydraulic or air 
cylinders 22 under the control of computer 36. The temperature of seaming 
iron 18, and the duration of the pressing cycle are variables which depend 
on the particular materials used and the characteristics of the seam 
desired. A common duration for the pressing cycle is about one second. 
After the perimeter seams are made and seaming iron 18 released, rollers 
15/16 draw the composite web 110 along the machine direction until the 
material for the next set of pouches is in position to have the perimeter 
seams created. It is preferred that web 12 have indicia printed thereon 
(shown as marks 113 in FIG. 2) spaced one pouch length apart. 
Photosensitive sensor 20 is positioned to detect the marks, and computer 
36 causes the rollers 15/16 to stop after the number of marks equal to the 
depth of the seaming have been detected. 
As the rollers 15/16 are drawing the webs 11 and 12 under the seaming iron, 
the web section on which pouch seams have previously been formed is passed 
into the accumulator portion of the machine. The accumulator is the 
portion of the machine between rollers 15/16 and roller 23. As the web 110 
is fed into the accumulator, a force provided by torque motor 34 (acting 
through arm 40 and flexible line 41) causes dancer rollers 24 to move 
downward and accommodate the web being fed in. Dancer rollers 24 
preferably have little mass so that, at the high speeds of operation of 
which the invented machine is capable, inertial effects do not create 
problems. The motion of dancer rollers 24 is sensed by vertical position 
encoder 35, and the resulting position data is transmitted to computer 36. 
The term accumulator as used herein refers to a section of a pouch making 
machine which temporarily stores varying amounts of web material so as to 
permit the instantaneous velocity of the web entering the section to not 
necessarily be the same as the instantaneous velocity of the web leaving 
the section. Such instantaneous input/output velocity differences cause 
the amount of web material stored in the accumulator to vary with time. 
The control system used to regulate the relative speeds of of the seaming 
section and the cutoff section of the machine will be discussed below. 
While the web 110 is being fed into the accumulator by rollers 15/16, 
rollers 25/26 withdraw material from the accumulator and feed it to the 
cutting mechanism (for example shear 200) where the individual pouches are 
cut off the web. FIG. 2 illustrates a portion of the web 110 after seaming 
and just before reaching the shear (and also a completed pouch (111) after 
it has been severed from the web). Rollers 25/26 are driven by motor 28 
under the control of computer 36, advancing the web as required to 
synchronize with the cutting mechanism. Photosensitive sensor 31 detects 
marks 113 on the web as rollers 25/26 feed the web out of the accumulator. 
One difference between the motion of rollers 15/16 and 25/26 is that 
rollers 15/16 advance the web many pouch lengths per seaming cycle (as 
many pouch lengths as the seaming iron is deep), whereas rollers 25/26 
advance the web one pouch length per cutoff cycle. Another difference is 
that rollers 15/16 are stopped for a period of time during each seaming 
cycle to permit the seams to be created, whereas, rollers 25/26 never stop 
(even though their instantaneous speed may vary substantially during a 
cutoff cycle). 
While the long term average speed of the web 110 leaving the accumulator is 
set to be the same as that of the web entering the accumulator, the 
instantaneous speeds are obviously quite different. The accumulator 
absorbs the short term variation in input/output material caused by the 
differences in instantaneous speed. 
One embodiment of a novel cutting mechanism which can be used in connection 
with the present invention is depicted in FIGS. 3-7. FIG. 3 is a schematic 
depiction of this embodiment, viewed from the side. In general terms, the 
cutting action is accomplished by shear 200 comprised of a pair of meshing 
blades 210 and 211. By "meshing" is meant engagement with a scissors like 
action. Instead of moving reciprocally in an up/down motion as do the 
blades of prior art scissors type cutters, the cutting edges of the blades 
in shear 200 move horizontally in the direction of web motion while the 
cut is being made by the vertical motion. In this embodiment the blades 
move with a circular motion, which has both vertical and horizontal 
components. FIG. 3 shows the blades in six positions, "a" through "f", 
during a cutoff cycle. Note that the blades 210 and 211 are continuously 
moving in circular orbits (212 and 213), and do not stop at the positions 
shown. The figure shows the upper blade 210 and the lower blade 211 in 
each of the illustrative positions. One rotation of the blades represents 
one cutoff cycle. Position "a" is where the blades are furthest apart, 
position "d" is where they are completely meshed, positions "c" and "e" 
are the positions where the blades are just beginning to mesh and their 
last point of contact, respectively, and positions "b" and "f" are 
intermediate points shown for reference. The phantom line circles 212 and 
213 shown in FIG. 3 represent the loci of the cutting edges of blades 210 
and 211 as they travel during a cutoff cycle. 
The web 110 is shown being fed into the cutter by nip rollers 25 and 26. 
Stationary guides 218 and 219 assist in directing the web into the cutter. 
The blades 210 and 211 are constrained (by means which will be described 
below) to maintain constant their angular attitudes in space as well as 
their horizontal positions relative to each other while their respective 
cutting edges trace out overlapping circles 212 and 213. As indicated in 
FIG. 3, blade 210 rotates in a counterclockwise direction, while blade 211 
rotates in a clockwise direction. Hence, during the half rotation when the 
blades are closest (between positions "b" and "f" while passing through 
positions "c", "d", and "e") the horizontal motion of the blades is in the 
direction of motion of web 110, (i.e., the machine direction). 
The horizontal speed of web 110 is regulated (by computer 36 responsive to 
encoders 38 and 39, as will be discussed later) to be substantially equal 
to the horizontal speed of the blades 210 and 211 when the blades are 
between positions "c" and "d". The blades 210 and 211 are preferably (but 
not necessarily) rotating at a constant angular speed, which implies that 
their horizontal speeds between positions "c" and "d" are not constant; 
hence the speed of web 110 will also vary during the cutting interval. 
Note that it would appear from FIG. 1 that the web is cut at the instant 
the blades pass position "c", but FIG. 3 is intended to illustrate the 
principle involved, and in practical machines, as will be discussed later, 
the cutting interval is spread out over a significant angle of motion of 
the blades. 
To the extent that there is a mismatch between the horizontal speeds of the 
web and the cutter blades during the cutting interval, it is preferred 
that the web be moving faster than the cutter blades. Under this 
circumstance, a slight buckling of the web may occur during the cutting 
interval, but so long as the mismatch is not great, satisfactory cuts can 
be made. 
Referring next to FIG. 4, a partially cross sectioned end view of the 
cutting mechanism described above is shown looking back into the cutter 
from the output side. With the exception of a few details, the cutter has 
left/right symmetry, and hence much of the following description will 
describe only the portion which appears at the left in FIG. 4, it being 
understood that, generally, parts described on the left side of FIG. 4 
have counterparts on the right. As seen in FIGS. 4-6, the cutter is shown 
with blades 210 and 211 in their most distant position, whereas in FIG. 7, 
the blades are shown completely meshed. 
The upper and lower blades 210 and 211 are shown mounted between left and 
right guide assemblies 220 and 220', which assemblies assure that blades 
210 and 211 maintain their angular and spatial positioning relative to 
each other. Blade 210 is coupled to upper guide block 222 and blade 211 is 
coupled to lower guide block 223. Blade 211 is rigidly attached to lower 
guide block 223, however, blade 210 is allowed to rotate slightly about 
axle 224 (FIG. 7). Spring loaded button 225 causes blade 210 to press 
against blade 211 when the blades are meshed, but the rotation is limited 
by stop 226 so that excessive rotation is not experienced (when the blades 
are not in contact). Blade 211 has a small lead-in 227 ground on a corner 
to assure proper meshing of the blades. It may be found that the initial 
contact between blade 210 and the lead-in 227 causes objectionable noise, 
particularly at high speeds, and in such cases a linear cam arrangement 
(not shown) can be used to create a gentler initial contact between the 
blades. In order to obtain good cutting action, it may be found to be 
advantageous to mount the blades such that the cutting edges are not 
precisely parallel, but rather cross slightly along their length. 
It will be noticed that, as shown in FIG. 4, the cutting edge of blade 210 
slopes downward to the right, whereas the cutting edge of blade 211 is 
horizontal. This configuration causes the shearing action of the blades to 
be spread out over some time interval, rather than being concentrated. 
Spreading of the shearing action is preferred since the cutting force 
requirements under such conditions are less. Whether the upper blade is 
sloped or whether the lower blade, or both are sloped to provide the 
distributed shearing action is a matter of choice. 
Guide blocks 222 and 223 are driven in circular paths by cranks 228 and 
229, which in turn are driven (in opposite directions) by gears 230 and 
231. Guide blocks 222 and 223 are kept in alignment by guide rods 232 and 
233, which preferably are a slip fit in guide block 223 and a tight fit in 
guide block 222. Since blades 210 and 211, together with their supporting 
structures, represent a substantial unbalanced mass, counterweights 234 
and 235 on gears 230 and 231 might be desired. Motive power for the cutter 
is provided by motor 30 coupled to gears 230 and 231 through axle 236 and 
gear 237. 
A second embodiment of a cutting mechanism for use in connection with the 
present invention is illustrated in FIGS. 8-11. FIG. 8 is a schematic 
diagram illustrating the operation of the shear 201 (viewed from the 
side). Web 110 is fed into the shear 201 by nip rolls 25 and 26. Similar 
to the first shear embodiment, the knife is comprised of two blades 250 
and 251 which cut using a scissors action. The blades travel in different 
paths, however, as compared to the first embodiment. FIG. 8 shows the 
blades in five positions covering one cutoff cycle, "a" through "f". Blade 
position "a" is the position where the blades are furthest apart, and 
blade position "d" is where they are at maximum mesh. By means which will 
be described later, the angular relationship between the blades is kept 
constant. Blade 250 is caused to rock back and forth, preferably at a 
constant radius, by servo motor 30, and the cutting edge thereby traces 
out an arcuate path represented by the phantom line 248 in FIG. 8. 
Positions "a" and "d" for blade 250 are in the same place. Blade 251 is 
also caused to rock back and forth by the servo motor 30, but not with a 
constant radius. The radius may be caused to vary by servo motor 30, or a 
separate servo motor 30' (not shown) can be used to provide the required 
motion. The cutting edge of blade 251 traces out a somewhat elliptical 
path as it rocks back and forth, as represented by the phantom line 249. 
The blades start to mesh at "c", and are completely meshed at "d". 
FIGS. 9 through 11 show the actual construction of the second embodiment of 
the cutting mechanism illustrated in FIG. 8. While only the left portion 
of the cutter is shown in FIG. 9, it will be understood that, as in the 
first embodiment, this embodiment has left/right symmetry and that with 
the exception of some minor parts, the elements shown in FIG. 9 have 
counterparts on the right side of the mechanism. 
The upper and lower blades 250 and 251 are shown in FIG. 9 supported by 
guide assembly 252 (which has a right counterpart guide assembly, not 
shown). The guide assembly 252 is free to rotate around axle 253, with 
guide rods 254 and 255 being fixed in block 256. Block 257 is driven by 
crank 258 and slides up and down on guide rods 254 and 255 as crank 258 
turns. Crank 258 is coupled to gear 259, which in turn is driven by motor 
30. As crank 258 turns, guide assembly 252 rocks back and forth, pivoting 
around axle 253 (as indicated in FIG. 10). The motion of blades 250 and 
251, as the guide assembly moves, is actually arcuate, but is nonetheless, 
substantially horizontal. 
In addition to its substantially horizontal oscillatory motion, blade 251 
is moved upward and caused to mesh with blade 250 by the chain of elements 
including gear 260, axle 253, eccentric 261, push rod 262, bar 263, and 
sliding block 264. Gear 260 may be mechanically coupled to gear 259 with a 
1:1 gear ratio, or gear 260 may be driven by a separate servo motor (30'), 
not shown. If gears 259 and 260 are mechanically coupled, the motion of 
blade 251 will be substantially as illustrated by phantom line 249 in FIG. 
8. If a separate servo motor 30' is used to drive gear 260, its speed 
during a cutoff cycle could be varied so as to bring positions "c" and "e" 
relatively closer together. This could be desirable in order to provide 
more time to enable the desired length of web to pass through the shear 
between cuts. 
As in the first embodiment, the speed of the web 110 is controlled by servo 
motor 28 to match the horizontal speed of the blades when they are between 
positions "c" and "d", and to increase or decrease the web speed at other 
times so that the desired length of web is cut off at each cutoff cycle. 
Alternatively, or in addition, the speed of motor 30 may be varied during 
each cutoff cycle to achieve the desired pouch length. 
Two embodiments of the cutting mechanism of this invention have been 
described above to illustrate the variety of ways in which the principles 
of the invention may be applied. It should be apparent that other 
embodiments are possible within the teachings of the invention. For 
example, as an alternate construction to the embodiment shown in FIGS. 
8-11, instead of rocking back and forth about axle 253, the guide 
assemblies 252 could easily be mounted for horizontal rectilinear motion 
on rails or ways and driven by a linear servo motor, rack and pinion, or 
crank and connecting rod to achieve pure horizontal back and forth motion. 
The pouch making machine described above and schematically illustrated in 
FIG. 1 is comprised of three sections, a seaming section, an accumulator, 
and a cutoff section. In some senses, the sections operate independently, 
however, their operations must be coordinated in that their average 
throughputs (in, for example, pouches per minute) must be close enough to 
the same to keep the amount of web stored in the accumulator at any time 
within the accumulator's capacity. The speeds of motors 17, 28, and 30, as 
well as the operation of cylinder 22 must be closely controlled and 
coordinated in order to obtain satisfactory operation. 
A presently preferred way of regulating the speeds of the various motors to 
achieve proper system operation is to utilize computer control. The 
computer (36) receives signals from encoders 35, 37, 38, and 39, as well 
as from photosensitive sensors 20 and 31, and in return, the computer 
controls cylinder 22, and motors 17, 28, and 30. All of the control 
modules for controlling the motors, and all of the signal conditioning 
units required, are encompassed within the term "computer" as used herein. 
The preferred operational plan under computer control begins with entering 
the independent variables into the computer memory. The preferred 
independent variables are 1) the length of each pouch, 2) the depth of the 
seaming iron (in number of pouches), 3) the desired seaming dwell time, 
and 4) the desired draw time to draw material from rolls 13 and 14 between 
seamings. Instead of the draw time, the intended number of pouches per 
unit time (i.e., pouches per minute) could be entered. 
From these inputs the computer 36 calculates an appropriate velocity and 
position profile for motor 17 during the draw sequence which will result 
in the proper number of marks 113 passing under photosensitive sensor 20 
during each draw. The motor 17 is programmed to stop the web a 
predetermined distance after photosensitive sensor 20 detects the last 
mark 113 of the desired draw sequence, preferably utilizing encoder 37. 
That is to say, if the seaming iron is 10 pouches deep, for example, the 
web will be stopped after each 10 marks 113 are detected. When motor 17 
stops, cylinder 22 is energized for the predetermined seaming time (input 
1), after which motor 17 starts another draw sequence. 
If the desired draw time is used as an independent variable (rather than 
the alternative, the intended number of pouches per minute), computer 36 
calculates the number of pouches per minute to be severed from the web by 
dividing the depth of the seaming iron (input 2) by the sum of the dwell 
time (input 3) and the draw time (input 4). This quotient is the number of 
pouches per minute produced by the seaming section, and hence the number 
of cuts per minute required of the cutoff knife. The rotational speed of 
motor 30 is set by computer 36 in accordance with the value calculated (or 
the value entered, if the alternate independent variable is used). Motor 
30 preferably has a uniform angular velocity during the rotation of blades 
210 and 211 (or 250 and 251), but under some circumstances, in order to 
accommodate pouches longer or shorter than can be produced using a 
constant angular velocity, it may be desirable to either speed up or slow 
down the rotation of motor 30 between positions "d" to "c", as compared to 
the speed of rotation between positions "c" to "d" 
Motor 28 is programmed to have a non-uniform angular velocity in that the 
web's velocity is matched to the horizontal velocity of the cutoff knife 
blades between positions "c" and "d", and then the web is either 
accelerated or decelerated so that exactly one pouch length of web is fed 
to position "c" between each arrival of the blades at position "c". Note 
that at position "d", the web has been completely severed, and it is no 
longer necessary to maintain close correspondence between the web speed 
and the horizontal blade speed. In order to accommodate small variations 
in actual pouch lengths and other variabilities, photo sensor 31 senses 
each mark 113 some short time before the cutoff knife reaches position 
"c", and computer 36, responsive to the outputs of encoders 38 and 39, 
causes motor 28 to bring the correct point on the web to position "c" as 
the blades start to mesh. 
Encoder 35 senses the vertical position of dancer bar 24, and causes the 
entire machine to stop if the capacity of the accumulator is exceeded. In 
addition, if encoder 35 senses that the cutoff section is running a little 
slower or faster than the seaming section (by the lower or upper extreme 
position of dancer bar 24 drifting up or down), computer 36 will alter the 
velocity profile of either motor 17 or motor 30 slightly to compensate. 
An alternate means for causing the two sections of the machine to run at 
identical average speeds (and so ensure that the capacity of the 
accumulator is not exceeded) is to continually or repeatedly compare the 
number of marks 113 detected by photosensitive sensors 20 and 31 (by 
computer 36), and if the accumulated difference exceeds a predetermined 
value, to make a speed correction of either the seaming section (motor 17) 
or the cutoff section (motor 30) to compensate. 
What has been described is a machine and method for fabricating pouches at 
speeds which have heretofore been considered impractical. Persons skilled 
in the art will no doubt be able to make various modifications and 
adaptations of the invention but yet be within the inventive teachings 
disclosed either explicitly or implicitly herein. The limits of the 
invention sought to be protected are defined by the following claims.