Note: Descriptions are shown in the official language in which they were submitted.
CMD-7015
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BAG MAKING APPARATUS WITH AUTOMATIC
COMPENSATION SYSTEM
Cross-Reference To Related Applications, If Any: None.
BACKGROUND OF THE INVENTION
Field of the Invention
-
The invention relates generally to the art of plastic
bag making machines. More specifically, the present
invention relates to a bag machine which employs a rotary -
sealing drum. Still more specifica'lyl the present
invention relates to a bag machine in which the sealing
drum is adjustable in size to produce different bags of
different sizes and in which the drum mechanism is
designed to compensate automatically for slight
corrections in the spacing of heat seals while the bag
making machine is operating.
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Descriptlon of Related Areas of Art
Many different t~pes of plastic bag maklng machines
are known to the art for producing plastic bags for
industrial and individual consumers for many different
applicatlons (e.g. small sandwich bags and trash bags).
Whlle the present invention has a wide range of
applications for the production of such products, the
related art will be explained by reference to one
par-ticular class of bags, i.e., polyethylene trash bags
or, garbage bags and wastebasket liners of the t~pe
usually sold in boxes of folded bags or rolls of bags.
Further discussion of the history and operation of
these machines can be found in U.S. Patent No. 4,642,084
entitled "Plastic Bag Making Machine", issued to the
present inventor on February 10, 1987 and assigned to
Custom Machinery Design, Inc. ~"Gietman patent 084").
~hat patent discloses a bag machine which includes a
rotary drum constructed of a plurality of slats and which
includes a gear mechanism adapted for infinite variation
of the drum diameter between a first smaller diameter and
a second larger diameter. A sealing blanket is provided
for the drum and is automatically adjusted for different
drum diameters to provide proper tension on the film as it
passes around the expandable drum.
In that configuration, manual rotation of a hex nut
assembly while the machine is stopped increases or
decreases the drum's diameter through a series of
appropriately mounted mitre gears and ring gears. Once
this adjustment is made, the machine begins operation.
Readjustment of the drum diameter can only be accomplished
by stopping the machine to adjust the hex nut assembly.
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Additionally, very small errors in drum diameter size can
lead to acute problems, particularly when the film passing
through the machine has preprinted material thereon which has
to appear at the same relative position on each bag. An error
of a fraction of an inch leads to serious problems when the
bag width is only several inches across and the speed of the
film moving thorough the machine is 500-900 bags per minute.
By the time the error is detected, a considerable amount of
film is wasted. Furthermore, the mistake is irreparable since
the heat seals and perforations can not be "corrected".
A bag making machine which overcomes these shortcomings
and those noted in the Gietman patent '084 would represent a
considreable advancement in the art.
OBJECTS AND SUMMARY OF l'HE INVENTION
It is a primary object of the present invention to
provide a plastic bag making machine whi~h addresses the
shortcomings of the prior art. Preferably, the machine is
capable of adjusting for different bag sizes without requiring
the machine to be stopped. The machine preferably is
adjustable to produce a wide variety of bag sizes and types
from various thicknesses of plastic film; ~nd is operable in
either a manual or automatic adjustment mode. The machine
desirably should automatically compensate for errors in sizing
of bags by adjusting its
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sealing apparatus to the bag size being produced without
having to stop the machine.
Generally, the invention provides a plastic bag making
machine utilizing a rotatable drum having an adjustable
diameter and a number of sealing bars, one or more of which
may be selectively activated. The drum is constructed of a
plurality of side members or slats and includes a gear
mechanism adapted for infinite variation of the drum diameter
between a first smaller diameter and second larger diameter.
A blanket is provided for the drum and is automatically
adjusted for different drum diameters to provide proper
tension of the film as it passes around the expandable drum.
The gear mechanism is operated by a motor mounted in the drum
and can alter the drum diameter while the machine is running.
Operation of the motor can be manual or automatic.
A chill roll, a rotary handle hole punching unit, a
perforator/cutter station and phase variators are also
included in the preferred embodiment, but ara generally
known in the art~ Nhen the machine is used to make bags
having printed material thereon, a comparator unit is used.
The comparator unit uses an electric eye or other
appropriate sensor adjacent the drum to determine the
spacing between activated sealing bars. An optical reader
is used to determine the spacing between printing on the
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film. A mlcroprocessor system compares these measured
spacings to a preselected spacing interval. The
microprocessor system then activates the drum motor if
necessaL-y to adjust the spacing between heat seals and
printed matter on the bag. The machine checks spacing on
an ongoing basis to maintain proper spacing.
Other variations and modifications of the invention
will become apparent to those skilled in the art after
reading this specification and are deemed to fall within
the scope of the present invention if they fall within the
scope of the claims which follow the description of the
preferred embodiment.
DESCRIPTION OF THE DRAWINGS
FIGURE l is a schematic illustration of the bag making
machine according to the preferred embodiment of the
present invention;
FIGURE 2 is a longitudinal elevation (partially in
section) of the expandable sealing dr~m according to the
preferred embodiment of the present invention;
FIGUR~ 3 is a cross-sectional view taken along the
line 3-3 of FIGURE 2;
FIGURE 4 is a perspective view of a length of printed
plastic film as used in the preferred embodiment of the
present invention.
In the FIGURES, like refexence numerals refer to like
elements. To improve the clarity of the description of
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the major features of the present invention, only general
descriptions are provided for components which are well
known in the art, and could be variously embodied by one
of ordinary skill in the art after reading and
understanding the principles of the present invention,
and/or are speciflcally described in the Gietman patent
`084
DESCRIPTION OF THE PREFERRED EMBODIMENT
Before proceeding to a more detailed description of
the preferred embodiment, it will be helpful to point out
the basic elements of the present invention as
incorporated in a bag making system such as the one
disclosed in the Gietman patent `084. For this purpose,
reference should first be made to the schematic diagram of
FIGURE 1, which shows a bag making machine 10
incorporating the present invention.
The major elements of system 10 include a dancer and
idler assembly 12, a sealing drum and blanket assembly 14,
a chill roll 16, a comparator unit 15, a punching station
17, a folding station 18, a pull roll system 20, a
perforator/cutting station 22 and a phase variator
assembly 24. The present invention is primarily concerned
with the sealing drum and blanket assembly 14 and the
comparator unit 15 as applied to plastic bag making
machines and other machines in which a specific function
is to be performed in a preselected spacing relationship
to preprinted matter on pliable material.
The elements of the system shown in FIGURE 1 may be
configured in other ways, including removing elements
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shown thereln. Likewise, the bag making machine 10 may
have other elements added depending on the type of product
being produced. For purposes of illustration, the basic
system of the Gietman patent `084 will be used herein but
should not be deemed limiting in any way. As noted above,
this system can be employed in any mechanism wherein
certain functions are to be performed in a specific
spacing relationship to preprinted matter on a stream of
pliable material.
Film 11 is fed from a source of plastic tubing 13
through dancer roll 12a and idler roll 12b into the
sealing drum and blanket assembly 14. Source 13 may be
any source for printed plastic material such as an
e~truder, a preprinted roll of plastic film, or a printer
on which the plastic is imprinted. Dancer roll 12a and
idler roll 12b maintain proper tension and speed for the
bag making system.
The sealing drum and blanket assembly 14 consists of a
cylindrical drum 28, which is capable of being varied in
diameter. That feature is illustrated in FIGURE 1 by the
dotted line. A number of sealing bars 30 are also shown
in FIGURE 1 and periodically form cross seals across the
fla~tened film tube 11. Sealing bars 30 are of
conventional design and are disclosed in detail with
respect to construction and operation in the Gietman
patent 084. A blanket 32 is mGunted on rollers 34, 35,
36 and 37 for surrounding a portion of drum 28 in such a
way that the film 11 passes between blanket 32 and drum 28
while seals are being formed. Rollers 34 and 35 are
mounted to an elongate frame 39 which is pivotable between
the full and dotted line positions shown in FIGURE 1.
Frame 39 includes a perpendicular plate 40 near its
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midsection, the latter being coupled to an air cyllnder 42
having an extensible rod 43. It will be appreciated that
extension of rod 43 causes rollers 34 and 35 to move to
the dotted line position when the drum diameter decreases,
thereby maintaining tension of the blanket 32 against the
drum 28.
Roller 37 is driven from a motor 44 by belt 45 to
drive blanket 32, and in turn blanket 32 will rotate drum
28 due to the tension between these components. The
specific construction of drum 28 will be discussed in more
de-tail below.
After passing the chill roll 16, the film 11 next
passes through an optional punching station 17 which
punches preselected hole and handle configurations in the
film. Thereafter, -the film may be further processed as
shown or in any other appropxiate manner.
The final element shown in FIGURE 1 is the variator
system 24 which is driven from a gear box 63 by belt 64.
Gear box 63 is driven by the drum 28 through belt 65.
Variator system 24 also includes hand wheels 66 and 67,
used to vary the phase of the perforator/cutting station
22 and the punching station 17, respectively. Adjustments
to the phase of perforator/cutting station 22 are made by
hand wheel 66 via belt 55. Similarly, adjustments to hand
wheel 67 are communicated to punching station 17 by belt
68. It should be recognized that the variators may be
adjusted while the bag making machine 10 is in operation.
Proceeding now to the more detailed description of the
preferred embodiment of the present invention, reference
is made to FIGURES 2 and 3 to illustrate the expandable
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sealing drum 28. Drum 28 is generally cylindrical and is
comprlsed of a plurallty of elongate slats 70. Each slat
70 includes a steel base 72 having a sllghtly curved
exterior surface. A rubber lagging 71 is provided on the
exterior surfaces to assis-t in maintaining proper traction
between blanket 32 and drum 28.
Drum 28 also has a pair of generally circular end
plates 75 and axial shaft sections 77a and 77b extending
through the center of drum 28 and mounted in suitable
bearings to permit rotation of drum 28. Twelve mounting
plates 79 having holes therein are attached to the
interior sides of each of end plates 75 near the outer
edge thereof, the axis of the openings of each plate 79
being radial with respect to the axis of shaft sections
77a and 77b. Similar plates 80 are affixed to end plates
75 inwardly of plates 79 so that twelve pairs of spaced
apart mounting plates (79 and 80) are disposed
equidistantly around each end plate 75.
A threaded rod 82 is placed through the holes in each
pair of plates 79 and 80, one end of which extends
outwardly therefrom. A mitre gear 85 is mounted on the
inner end of rod 82. Rotation of mitre gear 85 causes
rotation of rod 82.
A pair of ring gears 88 are rotatably mounted to a
machined hub of end plates 75 or. bearings 89 and are
constructed and arranged to mesh with mitre gears 85.
Rotation of any one of the rods 82 causes rotation of the
ring gear 88 and, in turn, the rotation of all t~elve of
the threaded rods 82 which are coupled to that particular
ring gear~
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Slats 70 are coupled to the threaded rods 82 by a
threaded plate 92 fastened to each end of slats 70.
Rotatlon of the rods 82 will cause plates 92 to travel up
and down the length of the rods. Rotatlon of a rod 82 in
one direction will cause the slats 70 to move radially
inward, reducing the drum diameter, while rotation in the
opposite direction will cause a drum diameter expansion.
Rotation of rods 82 is accomplished by motor 46
mounted in tube 48~ Tube 48 is a hollow tubular section
coaxially joining shaft sections 77a and 77b. Pinion 38
on gear box 49 is run by motor 46 and engages a ring gear
50 through which is mounted an axle 52. Axle 5~ extends
radially outward from tube 48 and has a pair of sprockets
56 and 57 mounted thereon~ Sprocket 56 engages chain 59
which in turn engages another sprocket 60 on one of the
rods 82 mounted adjacent the end plate 75 on shaft section
77a. Similarly, chain 62 runs between sprocket 57 and
sprocket 61 mounted to a rod 82 adjacent shaft section
77b.
Rotation of axle 52 by motor 46 causes the chains 59
and 62 to rotate the rods 82 adjacent each end plate 75,
thereby reducing or enlarging the diameter of the drum 28.
Motor 46 is energized by wires 54 which extend through
shaft section 77b and tube 48 from switch 51. Switch 51
provides the operator with the option of operating motor
46 manually or permitting automatic operation with
processing unit 21 in a manner to be described below. The
operator may operate the motor 46 while the machine 10 is
running to adjust the drum diameter during operation if
desired.
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Flnally, comparator unit 15 will be described. As
noted above, comparator unit 15 includes a central
processing unit (CPU) 21. Connected to CPU 21 are a first
detector 19 and a second detector 23. Detector 19 is
located above the path of the film as ~t passes over the
idler roll 12b. Idler roll 12b provides a consistent
optical background for detector 19 so that registration
marks 100 on the film 11 can be read accurately.
Detector 23 is positioned directly above drum 28. In
the preferred embodiment, detector 23 is an electric eye
device deslgned to generate a signal when an object passes
through it. In the present invention, a small protrusion
26 is placed on drum 28, as seen in FIGURE 3. Detector 23
sends a signal to CPU 21 every time drum 28 makes a
complete revolution. Specific operation of CPU 21 and
comparator unit 15 will be described below.
Comparator unit 15 is activated by the operator by
turning switch 51 to its automatic setting. Various CPU
functions may then be selected and performed.
Operation
_
While the operation of the bag machine of the present
invention will be described with specific reference to the
configuration of the Gietman patent 084 and a machine for
producing plastic, it should be understood that the
principles taught herein have numerous other applications.
Therefore, application of the subject matter should not be
limited just to plastic bag making machines.
CPU 21 is preprogrammed with preset conditions for the
number of sealing bars 30 to be used (and, therefore, the
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number of seals per 360 of rotation of drum 28). Drum 28
is manually adjusted to the approximate proper size by
switchlng operation to the "manual" setting on switch 51.
Thereafter, the switch 51 lS set on "automatic" for
continuous operation.
Initially, film 11 is fed from roll 13 through the
dancer and idler rolls to the blanket and drum assembly
14. As the film passes over the idler roll 12b, detector
19 reads the position of the mark registration 100
relative to the activated seal bars' position generated by
detector 23, and compares this relationship to the preset
conditions. Appropriate activation of the motor 46 and
adjustment to drum size is then made. For exampler if the
seal bar position is progressively moving away from the
mark registration on the film, then the drum size is too
small and motor 46 will be activated to increase the drum
diameter. When the seal bar holds its position relative
to the mark registration, drum 28 is then set at the
proper diameter.
At this pointj seal bar operation and the mark
registrations 100 are in phase. A shift may then be
required to bring each seal and coxresponding mark
registration 100 into proper spacing. This is also
accomplished with the CPU 21 and its automatic control of
the drum size.
In order to do this, the drum size is altered
temporarily to allow the mark registration 100 to "move"
closer to the seal. As an example, if the registration
mark needs to be moved closer to the seal, the drum size
is altered to establish a known rate of advancement of the
mark 100 toward the seal on each revolution of drum 28.
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When enough revolutions are completed, the drum is
returned to its proper size and normal operation ensues.
The followlng example is illustrative of how this is
accomplished, but is not in any way limiting on the use of
the equipment or the components therein.
If the registration mark is 6 inches away from the
desired relative position to the seal, the drum
circumference may be reduced by 1/2 inch. Thus, after
every revolution of the drum, the registration mark is 1/2
inch closer to the seal. After 12 revolutions, the seal
and registration mark will be properly spaced~ Drum 28 is
then expanded to the original circumference and normal
operation of the machine may recommence.
During normal operation of the machine, plastic film
11 is fed from the roll 13 through the dancer roll 12a and
idler roll 12b to the blanket and drum assembly 14 where
heat seals are applied. The plastic film may be
configured so that the seals define the bottoms of plastic
bags being formed. Alternatively, the seals may define
the sides of the bags. In this situation, the plastic
film 11 is slit longitudinally down the middle, the middle
slit being the top opening of each bag being formed~
Utilizing the drum sizing and the registration
mark/seal orientation functions of the comparator unit 15,
seals may be consistently placed in proper orientation to
any printed matter appearing on the film. As the film 11
leaves the blanket and drum assembly 14, it encounters the
chill roll 16 which cools the heat seals.
The plastic is next fed to the punching station 17
where handles may be punched into or out of the plastic
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and the bag's configuration may be further defined. For
example~ "t-shirt" bags are quite popular in supermarkets
and grocery stores at present. These bags have a lower
bag section and two handles that resemble the shoulder
straps of a tank top t-shirtO This configuration may be
punched on the apparatus shown.
From the punching station 17, the film may be fed to a
folding station 18 as disclosed in the Gietman patent
084. Fxom folding station 18 film 11 may next move to
the perforator/cutting station 22 where perforations can
be placed between bags or where the bags may be completely
separated. As shown in the Gietman patent `084, the
separation between bags may also be partially slit,
lS partially perforated. The bags then move on to a
packaging operation.
In the preferred embodiment, the punching station 17
and perforator/cutting station 22 are run off of the same
gear box 63 connected to the drum 28. Variator system 24
allows adjust~ents to these stations so that there is no
phase variance between seals, handle cuttings and
perforation or cutting.
The comparator unit 15 serves one other function
during operation of the machine. The two detectors 19 and
23 are continuously measuring the moving averages, and
changes therein, of the discrepancy between the actual
spacing between the registration mark and the seal and the
preset, or desired spacing.
When the discrepancy reaches a preselected limit, the
CPU 21 instructs the motor 46 to make a minor adjustment
in the size of the drum 28 to compensate. The drum
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diameter may be slightly lncreased or decreased. This
compensation function is continuous and ongoing so tha-t
the printed matter 101 is maintained in a consistent
position on the bags.
Unlike systems designed to perform the same functions,
the improvements to the bag making machine as disclosed
herein and in the Gietman patent ~084 allow these machines
to operate at speeds far in excess of those of the prior
art.
While one preferred embodiment of the present
invention is shown ln the FIGURES and described in detail
herein, modifications and variations could be developed by
one of ordinary skill in the art after the objects of the
invention are understood. For example, in any operation
in which a specific function such as perforation or
punching needs to be performed on a continuous stream of
pliable material (e.g., paper or cloth) having printed
matter thereon, in a preselected spacing relation, this
system can easily be adapted to perform efficiently and
easily. Accordingly, the present invention is not to be
limited to the specifically disclosed preferred
embodiment, but rather only by the scope of the claims
which follow.
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