U.S. patent number 3,924,521 [Application Number 05/472,167] was granted by the patent office on 1975-12-09 for method for forming flat bottom plastic bags.
This patent grant is currently assigned to Violet M. Hanson. Invention is credited to John E. Finn, Violet M. Hanson.
United States Patent |
3,924,521 |
Hanson , et al. |
December 9, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Method for forming flat bottom plastic bags
Abstract
Flat bottom bags are formed from a supply of substantially
endless plastic tubing, gusseted along two sides to form a flat
reel. A sleeve of predetermined length is withdrawn from the reel
and allowed to hang along a vertical plane between two foraminous
plenum chambers which are then moved toward each other to squeeze
the length therebetween. Simultaneously a sealing and shearing
mechanism forms a transverse seal and cuts the sleeve length from
the reel, the gussets being at the same time sealed in the seam.
The plenum chambers are then subject to vacuum and are moved apart,
causing the sides of the now formed bag to separate opening the
same. Upon opening of the bag, a forming mandrel is inserted
therein and moved through the length of the bag until it reaches
the sealed end. Simultaneously a presser member is moved across the
outside surface of the bag folding over the seam, and pressing the
gusset portions into flat flaps and in addition forming
simultaneously the flat bottom to the bag. The mandrel or the
presser plate is provided with heat sealing means sealing the flaps
to the sleeve sides.
Inventors: |
Hanson; Violet M. (Old
Bethpage, NY), Finn; John E. (Plainview, NY) |
Assignee: |
Violet M. Hanson (Old Bethpage,
NY)
|
Family
ID: |
23874451 |
Appl.
No.: |
05/472,167 |
Filed: |
May 22, 1974 |
Current U.S.
Class: |
493/209; 493/218;
493/239 |
Current CPC
Class: |
B31B
70/64 (20170801); B31B 70/00 (20170801); B31B
2160/10 (20170801); B31B 2155/00 (20170801); B31B
2150/00 (20170801); B31B 2160/102 (20170801); B31B
2150/0016 (20170801); B31B 2155/003 (20170801); B31B
2160/20 (20170801); B31B 50/94 (20170801) |
Current International
Class: |
B31B
29/00 (20060101); B31B 1/74 (20060101); B31B
1/94 (20060101); B31B 37/00 (20060101); B31B
033/00 () |
Field of
Search: |
;93/35SB,35R,84R,84FF,14,15,16,17,21,22,23,24,25,28,29,30,31,33H,53SD,8R
;53/385,386 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Coan; James F.
Attorney, Agent or Firm: Bauer & Amer
Claims
What is claimed is:
1. A method of making a reinforced flat bottomed bag comprising the
steps of providing a sleeve having opposed faces and sides gusseted
inwardly between the opposed faces, closing one end of said sleeve
with a seam to seal the opposed faces together with the gusseted
sides therebetween, thereafter pulling said opposed faces apart to
open said sleeve, inserting a form within the other end of said
sleeve and pressing the form against the closed end to flatten the
whole of the gusseted sides against the faces forming flaps having
folds lying in overlapping relationship with the opposed faces, and
securing preselected portions of said flaps and said overlapping
sides and faces to form a flat bottom.
2. The method of making a reinforced bag according to claim 1
including the steps of sealing said flaps, sides and faces together
along said folds.
3. The method according to claim 1 wherein said faces are pulled
apart by exerting suction on the exterior surfaces thereof.
4. The method according to claim 1 wherein said sleeve is cut from
an endless tube of material in a predetermined length and the
bottom is seamed adjacent said cut.
5. The method according to claim 4 including the step of cutting
said sheet and forming said seam simultaneously.
6. The method according to claim 5, said form being a mandrel
conforming to the shape of said bottom and being provided with heat
sealing means to seal said folds.
7. The method according to claim 1 including the step of applying a
blast of air into the open end of said sleeve simultaneously with
the application of suction and withdrawal of the sides thereof.
8. The method of continuously forming flat bottom reinforced bags
from a substantially endless roll of tubular plastic material
folded to have flat faces and longitudinally gusseted sides,
comprising the steps of periodically withdrawing a predetermined
length of said tubing, securing said length between a pair of
foraminous plates, cutting said predetermined length from said
tubing and forming a seam adjacent said cut end to seal one end of
said tubing, withdrawing said foraminous plates and simultaneously
applying a vacuum thereto to suck said material against said plates
and open said length of tubing, inserting a shaped mandrel within
the open end of the length of tubing and pressing said mandrel
against the sealed end thereof to flatten the whole of the gusseted
sides against the sealed end forming flaps having folds with the
faces thereof and sealing said folds to said faces, thereafter
repeating said process until said roll is exhausted.
9. The method according to claim 8 including the steps of
collapsing said open tubing and folding the formed sealed end
against one face of said tubing and thereafter ejecting said length
of tubing from between said foraminous plates, prior to repeating
said process.
10. The method according to claim 9 including the step of providing
a counter on the outer surface of said sealed end against which
said shaped form is adapted to press, said counter simultaneously
folding and pressing over the seamed end against the face of said
tubing.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for making
flat bottom plastic bags and in particular to a flat bottom bag
having a bottom of more than one thickness and being
reinforced.
In a co-pending application, Ser. No. 376,112, filed on July 3,
1973, there is disclosed a flat bottom bag formed of paper,
plastic, cloth or combinations thereof in which a tubular length of
material is first gusseted along two sides, cut into a
predetermined length and provided with seal transverse to its
length. Thereafter, a mandrel is inserted in the tube to shape the
bag and flatten the bottom end into a reinforced multiple layer
flat bottom. The present invention has as its main object the
provision of an improved method for forming the bags disclosed in
the aforementioned application and simple apparatus for carrying
out the method in a continuous cyclical operation.
It is further object of the present invention to provide a method
and apparatus particularly adapted to the formation of thin walled
plastic bags having flat bottom. In general, in the known prior art
the formation of flat bottomed bags from thin walled plastic
material was most difficult and virtually impossible wherein it was
necessary to form the flat bottom with multiple reinforced layers
sealed together to form the unitary structure. Substitute measures
were only possible in the prior art. In particular, the prior art
utilized separate reinforcing layers, such as heavy cardboard to
maintain a flat rectangular bottom. More often than not, the flat
bottomed construction required the creation of perforations or
slits in order to create the necessary folds to establish the flat
condition. The present invention has as its object the formation of
an imperforate reinforced construction capable of carrying solids,
granular and liquid materials. In general, the known apparatus for
forming bags, particularly from plastic material, are complex and
rather costly both to build and to operate, in addition to being
incapable of making the flat bottom imperforate bag desired herein.
It is accordingly another object of the present invention to
provide simple economic apparatus for the formation of such
bags.
The foregoing objects, as well as further objects, features and
advantages of the present invention, will be more fully appreciated
by reference to the following disclosure.
SUMMARY OF THE INVENTION
According to the present invention the method for forming a flat
bottom reinforced bag comprises sealing one end of a tubular sleeve
which has been previously folded to have opposed faces and sides
gusseted inwardly between the opposed faces, pulling the opposed
faces apart to open the sleeve and thereafter inserting a form
within the sleeve. The form is pressed against the sealed end to
flatten the gusseted sides forming flaps having folds with the
opposed faces and the gusseted sides lying in overlapping
relationship. Thereafter preselected portions of the flaps and the
overlying sides and faces are joined together to form a flat
bottom.
Preferably, the faces of the sleeve are pulled apart by exerting
suction on their exterior surfaces, the suction being maintained
until the form is capable of moving into and out of the open
sleeve.
Preferably, the sleeve is cut from an endless tube of material
which has been prefolded with its gusseted sides. The cutting of
the sleeve and the seaming of its one edge can preferably be done
simultaneously by combination knife and seal means. The form
inserted within the open sleeve is also preferably provided with
sealing means so that the gusseted flaps can be secured to the
faces of the sleeve so as to form and maintain a flat bottom.
In carrying out the method the present invention provides novel
apparatus for forming the reinforced flat bottom bags from a
tubular sleeve having opposed faces and gusseted sides. The
apparatus comprises means for supporting the sleeve adjacent one
end, a foraminous plenum chamber located adjacent each of the faces
of the sleeve having means for moving the chamber toward and away
from the respective faces. Means are provided for seaming closed
one end of the sleeve to seal the opposed faces together with the
gusseted sides therebetween. The plenum chambers are movable
inwardly relative to each other to engage the respective faces of
the sleeve to support the sleeve during the seaming operation and
is movable outwardly thereafter. Means are provided for applying a
vacuum through the plenum chambers on the outward movement so as to
cause the faces of the sleeve to adhere to them and open the
sleeve. A mandrel is movable into the open end of the sleeve
against the seamed end to flatten the gusseted sides forming flaps
having folds with the opposed faces in overlying relationship.
Means are provided for securing the flaps and the overlying sides
along preselected lines thereby forming and maintaining a flat
bottom.
The apparatus includes means for supporting a substantially endless
reel of plastic material which is prefolded with its opposing faces
and gusseted sides into a continuous sheet. The apparatus includes
means for withdrawing a predetermined length of sleeve from the
sheet and cutting the length therefrom. Preferably the means for
withdrawing the sheet comprises a pair of engaging pull rollers
which are intermittently driven so as to obtain predetermined
lengths. The pull rollers are arranged to support the sheet in a
vertical plane and the foraminous plenum chambers are arranged
parallel to the plane and movable in a direction transversely
thereto. The cutting means and the means for forming the seam in
the sleeve are preferably mounted on a common support and operable
simultaneously. Accordingly, the foraminous plenum chambers are
movable into engagement with the faces of the sheet prior to the
cutting of the sheet from the reel.
A plate is provided which is movable over the exterior surface of
the seamed end of the sleeve which acts in cooperation with a
mandrel to press the seamed and flat against the bottom and to act
as a counter for the mandrel. If desired a flow of air may be
impressed into the open end of the sleeve on the outward movement
of the foraminous plenum chambers to assist in the opening of the
sleeve. Further, a flow of air under pressure may be impressed
outwardly from the foraminous plenum chambers on withdrawal of the
predetermined length of sleeve from the reel. This flow of air
insures the free movement of the sheet material and prevents any
harmful effects arising from static electricity.
The apparatus is further provided with means for collapsing the
formed bag so that it again assumes its flat position in which the
gusseted folds extend inwardly. The apparatus also includes means
for folding the bottom flat against one of the faces of the sleeve.
This latter folding means also comprises the means for removing and
ejecting the completed bag from the apparatus.
Full details of the present invention are set forth in the
following description and are illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is an isometric view of the apparatus for carrying out the
present invention,
FIG. 2 is a series of views A through F showing various stages of
bag formation according to the method of the present invention,
FIGS. 3A through 3E are front elevational views of the apparatus
shown in FIG. 1 showing sequentially the operation of the apparatus
through the respective stages of bag formation corresponding to
FIGS. 2A through 2E,
FIGS. 3F through 3H show sequentially the several steps in the
final stage of the method of bag formation corresponding to FIG.
2F,
FIG. 4 is a sectional view of the apparatus taken along line 4--4
of FIG. 3A,
FIG. 5 is a sectional view of the apparatus taken along FIG. 5--5
of FIG. 3A,
FIG. 6 is a sectional view of the apparatus taken along line 6--6
of FIG. 3A,
FIG. 7 is an enlarged portion of the plenum chamber of the
apparatus showing the direction of its air holes,
FIG. 8 is an exterior view of the bag bottom before being sealed
and at the stage corresponding to FIG. 2C,
FIG. 9 is an external view of the bag bottom as seen in FIG. 8
showing the position of the heat sealing means,
FIG. 10 is a top view of the forming mandrel showing the heat seal
means, the forming lip and ventilation holes,
FIG. 11 is a sectional view taken along lines 11--11 of FIG. 10,
and
FIG. 12 is a sectional view of the apparatus taken along line
12--12 of FIG. 3E.
DESCRIPTION OF THE INVENTION
The formation of flat bottom bags according to the present
invention is concisely illustrated in the sequential views shown in
FIG. 2. Initially a reel 10 of unseamed or seamed flattened tubing
12, preferably of plastic, but of any other applicable material,
prefolded with longitudinal gusset folds 14 is provided. In the
first stage (FIG. 2A) a predetermined length of flat tubing 12
sufficient to form a bag B is withdrawn from the reel 10. In the
second stage a transverse seam 16, preferably heat sealed, may also
be formed by other methods, as glueing. The seam 16 is formed at
what becomes the bottom edge of the bag and the predetermined
length of tubing is cut adjacent the seam so as to separate that
portion from the endless reel.
In the third stage (FIG. 2C), the sides of the flat tubing 12 are
pulled outwardly in the direction of arrows 18 causing the bag to
open and expose the gusset sides. A forming mandrel is then
inserted through the open end 20 of the bag B until a flat bottom
22 is formed. During this stage, the gusset portions adjacent and
held by the bottom seam 16 are folded into triangular flaps in the
interior of the bag. In the fourth stage (FIG. 2D), the flaps 24
are heat sealed along lines 26 to the exterior tubing material so
that they become integrally formed with the bottom 22 of the bag.
Thereafter the mandrel is withdrawn. In the fifth stage (FIG. 2E),
one side of the bag is pushed inwardly, as the mandrel is being
withdrawn, this folds the bottom of the bag 22 toward one of its
sides simultaneously the gusset folds 14 are again folded inwardly.
In the final stage (FIG. 2F), the bag bottom 22 is pressed against
the bag sides and moved to a storage in stacking position.
As seen in FIG. 1, the apparatus for carrying out the
aforementioned method comprises a supporting frame having a back
wall 30 on which is journaled a freely rotatable supporting shaft
32 extending cantilevered from the back wall in a horizontal plane.
The reel 10 of plastic tubing 12 is adapted to be held on the shaft
32 and to be passed downwardly between a pair of contra-rotating
pull rollers 34 located below and somewhat to the side of the shaft
32. The pull rollers 34, preferably made of rubber or other
similarly resilient material are in pressure engagement with each
other and as seen in FIG. 4 are each mounted on shafts 36 journaled
in the back wall 30. The rollers 34 are interconnected for conjoint
rotation by an intermeshing gear train 38 to a drive motor 40 also
mounted on the back wall. The motor 40 is connected to an automatic
control system (not shown) so that it may be intermittently driven
in accordance with the predetermined program to withdraw a
predetermined length of tubing 12 from the reel 10 and allow the
tubing to hang vertically therefrom.
Located a short distance below the drive rollers 34 is a sealing
and shearing assembly, generally depicted by the numeral 42. This
assembly comprises cooperating right and left hand bars 44 and 46
respectively, mounted in a guide rail support 48 on the back wall
so as to be reciprocatingly movable toward and away from each other
in a horizontal plane normal to the vertical plane defined by the
hanging plastic tubing 12. The bars 44 and 46 are connected by a
suitable gearing or rack mechanism with a linear motor 50, as seen
in FIG. 5 so that they are simultaneously moved. Fixed to the guide
rail is a stop block 51 which may be used to limit the movement of
the bars 44 and 46 toward each other. Fixed to the upper edge of
the right bar 44 is a knife 52, the cutting edge of which is
adapted to slidingly engage the upper surface of the left bar 46,
which thus serves as a knife counter therefor. The right bar 44 is
further provided with an elongated linear heating element 54,
suitably connected to a source of current, while the left bar 46 is
provided with a groove 56 adapted to receive the heating element
54.
Located below the sealing and shearing assembly 42 is a tube
distension assembly, generally depicted by the numeral 58,
comprising a vertically disposed first hollow plenum chamber box
60, movable toward and away from the plane of the depending plastic
tube 12, by a linear motor 62 secured to its back wall face and
mounted on the back wall of the machine frame. On the left side of
the plastic tube 12 a second and third hollow plenum chamber box 64
and 66 are located vertically one above the other. The lower left
plenum box 64 is provided with a horizontal shelf 68 formed above a
rearwardly extending base web 70 on which the upper left plenum box
66 slidably rests. The upper plenum box 66 is movable toward and
away from the plane of the plastic tubing 12 by a linear motor 72
which is secured to its rear face and is mounted on the base web
70. Similarly the lower plenum box 64 is movable in the same
direction by attachment with another linear motor 74 which is
itself mounted on the back wall 30 of the machine frame. The
vertical height of both the lower left plenum chamber and the upper
left plenum chamber 64 and 66 respectively is equal to that of the
right plenum chamber 60 and because motor 72 actuating the upper
left plenum box 66 is secured to the base 70, the upper plenum box
66 can be made to be conjointly movable toward and away from the
plane of the plastic tubing 12 together with the lower plenum box,
by not actuating the motor 72. On the other hand relative movement
between the upper plenum box 66 and the lower plenum box 64 is
possible by independently activating the motor 72. Actuation of the
motor 74 causes both the lower plenum box 64 and the upper plenum
box 66 to move toward and away from the plane of the plastic tubing
12. The upper plenum box 66 and the lower left plenum box 64 both
slidably rest on a horizontal supporting plate 76 which extends
perpendicularly outward from the back wall 30 of the machine frame.
Each of the plenum boxes 60, 64 and 66 are provided with a front
wall having a plurality of holes 78 and each are connected to a
source of both air under pressure and under vacuum. The source may
be a common source and in any event the sources are provided with
suitable control valving for regulating intermittent flow of either
air or vacuum inwardly or out of the plenum boxes 60, 64 and 66. As
seen in FIG. 7, the major portion of the holes 78 are angled
downwardly toward the plane of the depending plastic tubing 12
while at least some of the holes along the upper edge of the right
plenum box 60 and the upper left plenum box 66 are horizontally
directed.
The horizontal plate 76 is divided symmetrical to the plane of the
vertically depending plastic tube 12 to provide a slot 80 in which
is located a forming mandrel 82. The mandrel 82 comprises a flat
horizontal plate-like member fixed at the end of a rod 84,
connected to a linear motor 86 adapted to move the mandrel
vertically from the slot 80 upwardly toward the sealing and
shearing assembly. As seen in FIG. 10, the forming mandrel 82 is
provided with a plurality of ventilation holes 88 and electric
heater or glueing bars 90 arranged in a configuration conforming to
the manner in which the gusset flaps 24 are to be sealed as
disclosed in the co-pending application. The forming mandrel 82, as
seen further in FIG. 11, is provided with a peripheral lip member
92 comprising a rectangular frame having an L-shaped cross section.
The base leg of the lip 92 is set within a circumferential slot 94
and held therein by a flexible or resilient member 96 such as a
rubber pad so that under upward movement of the forming mandrel 82,
the lip 92 can engage the inner surface of the plastic tubing
causing the same to open into the relatively flat shape of the bag
bottom 22 seen in FIG. 2D having accurately folded corners and
edges. The resilience of the lip 92 allows the lip to recede under
pressure thus ensuring that the plastic tubing will not be
torn.
Located at the level of the horizontal plate 76, along the vertical
plane of the depending plastic tubing 12, are a pair of air jet
nozzles 98, one on each of the forward and rear sides of the
forming mandrel 82, as seen in FIG. 6. The air jet nozzles 98 are
connected to a source of air under pressure with suitable
regulating and controlling mechanisms to provide intermittent blast
of air on predetermined signal.
Mounted above the right plenum box 60 in a horizontal plane is a
press plate 100 secured to the end of a rod 102 activated by a
linear motor 104. The press plate is adapted to slidably rest on
the upper edge of the plenum box 60 and to be movable transversely
across its top toward the left side of the apparatus to a position
directly in line with the forming mandrel 82.
Mounted to the back wall 30 behind the right plenum box 60 are a
pair of back to back linear motors 106 adapted to move in a
direction parallel to the plane of the depending plastic tubing 12
and perpendicular to the plane of the back wall 30. Extending from
each of the linear motors 106 is a wire rod 108 in the form of a
U-shape. The U-shaped wire rods 108 bend around the right plenum
box 60 each terminating in a tuck finger 110 extending in the plane
of the depending plastic tubing 12. The motors 106 are adapted to
move the tuck fingers 110 inwardly in the direction of arrow 112,
as seen in FIG. 12, along the plane of the plastic tubing to engage
with the gusset folds 14.
Fixed to each side edge of the shelf 68 of the lower left plenum
box 64, are a pair of L-shaped brackets 114 having one leg
extending vertically upward. Attached to pivot about a point 116 on
the upper ends of the vertical legs is a U-shaped wire ejection bar
118 which girdles the upper plenum box 66. The ejection bar extends
rearwardly from the pivot point 116 and is connected to a rod 120
extending from the vertically movable linear motor 122 pivotally
mounted on the base web 70 of the lower left plenum box 64. The
wire ejection bar extends forwardly of the pivot point 116 to the
plane of the front face of the lower plenum 64 with which it is
conjointly movable in the horizontal direction by virtue of its
connection to the base web 70. The upper left plenum box 66 is
provided with a groove 123 into which the wire ejection bar 118 may
recede when the upper plenum box 66 is aligned with the lower
plenum bar 64, as seen in FIG. 1, on withdrawal of the upper plenum
box 66 rearwardly from the plane of the lower left plenum box 64,
the ejection bar is free to pivot and on actuation of the motor 122
is caused to pivot in the direction of the arrow as seen in FIGS.
3G and 3H.
Located above the upper left plenum 66 and slightly to the left is
a take off platform for the finished bag. The platform comprises a
flat plate 124 at the leading end of which are located a pair of
ejection rollers 126, having a rubber or resilient plastic face in
pressure contact with each other. The platform plate 124 and the
nip of the rollers 126 lie in a horizontal plane substantially even
with the lower surface 128 of the counter sealing and shearing bar
46, which lower surface is curved to permit a smooth arcuate
extension from substantially the vertical plane of the plastic
tubing 12 to the plane of the platform plate 124. The several
linear motors which are shown preferably comprise air piston and
cylinder actuators of conventional form. Hydraulic piston and
cylinder actuators may also be used as can rotary electric motors
coupled with suitable pinion and rack means. Solenoid actuated
pistons may also be used. The structure and operation as well as
the use of these devices as well as other equivalent devices will
be obvious to those skilled in the present art. A source of air
both under pressure and under vacuum is required in the present
apparatus. Suitable pump compressor or similar means may be
provided to supply either or both. Conventional control means,
valve means, etc. to regulate the operation of the air supply will
also be obvious. For clarity and simplicity some of the parts of
the present apparatus have been omitted from the drawings, tubular
connectors, electrical connectors, vacuum fittings, etc. have all
been omitted from the drawings and from the description. While
specific details such as these are not shown their structure and
function will be obvious. Suitable interlocks and control means as
well as a programable control system obtaining sequential operation
of the various elements of the present apparatus are also omitted
for the sake of clarity and brevity. The following description of
the apparatus through its sequential steps and operation cycle to
form a bag will render the further description of the omitted
elements unnecessary. In the following description of the apparatus
it will be clear that the positions shown in FIGS. 3A through 3E
correspond to the method steps 2A through 2E respectively while the
positions shown in FIGS. 3F through 3G correspond in total to the
steps shown in the method stage illustrated in FIG. 2F.
The various control and interlock system will be apparent from the
following description.
Turning now to FIG. 3A, the operation of the apparatus is initiated
by placing the supply reel 10 on the supporting shaft 32 and
extending its leading edge between the pull rollers 34
simultaneously the bars 44 and 46 of the sealing and shearing
assembly, the plate 100, the right plenum chamber 60 and the left
plenum chambers 64 and 66 jointly are withdrawn to their furthest
position from the plane of the plastic tubing 12. Simultaneously
the forming mandrel 82 is retracted to its lowest position. This
leaves a free path of movement along the vertical plane for the
tubing 12. In the first stage of operation the pull rollers 34 are
actuated by their motor 40 so as to withdraw a predetermined length
of tubing 12 from the reel 10. This is obtained by programming the
length of time the motor 40 is actuated for a predetermined time
dependent upon the diameter of the rollers 34 thereby a given
length can be obtained. If desired, suitable sensing means such as
a photoelectric cell, microswitch or the like can be arranged along
a path of the plastic tubing 12 to determine the length withdrawn.
To assist the tubing 12 as it is being withdrawn from the reel 10
and to prevent static electricity from causing the tubing to be
attracted to either one or the other of the plenum boxes, a flow of
air under pressure is supplied to the plenum boxes 60, 64 and 66
under low pressure so that the air streams outwardly from the
plenum boxes in the direction of the arrows shown in FIG. 1. The
flowing outward air insures that the plastic tubing will descend
along the central plane and without creases or folds.
After the predetermined length of plastic tubing 12 is withdrawn by
the pull rollers 34 the pull rollers stop and thereafter the plenum
boxes 60, 64 and 66 simultaneously are moved inwardly toward the
plastic tubing 12 as indicated in FIG. 3B until they abut the
surface of a plastic tubing. The plastic tubing is then held taut
between the arrested drive rollers 34 and the plenum boxes. Almost
simultaneously the sealing and shearing assembly bars 44 and 46 are
caused to move inwardly toward each other. The knife 50 cuts the
tubing transversely to the vertical plane while simultaneously the
heater element 54 heat seals the bottom edge with the seam 16 as
seen in FIG. 2B. During this operation both the forming mandrel 82
and the plate 100 remain in their retracted positions. After the
creation of the heat sealed seam 16 the bars 44 and 46 of the
sealing and shearing assembly together with the right plenum box 60
and the jointly aligned plenum boxes 64 and 66 begin a rearward or
outward movement from the plane of the plastic tubing 12; as soon
as this outward movement begins a vacuum is applied in each of the
plenum boxes causing the flat sides of the plastic tubing to adhere
to their faces. Simultaneously air under pressure is applied
through the air jet nozzles 98 located at the level of the
horizontal shelf 76. This causes an air flow into the open end of
the tubing assisting in the opening of the tubing into the form
shown in FIG. 3C. As the plenum boxes pull the sides of the plastic
tube the sealed upper end, which now is to become the bottom of the
bag, is pulled downwardly, the gusset folds are pulled outwardly
and the bottom edge opened. As soon as the bottom edge opens, the
forming mandrel 82 is elevated by its motor 86 into the bag, as
seen in FIG. 3C. Simultaneously the plate 100 is advanced across
the upper edge of the pelnum box 60 by its motor 104. As the plate
100 advances, it wipes across the exterior surface of the bottom of
the bag folding and flattening down the transverse excess tab
remaining between the seam 16 and the edge at which it was sheared
from the remaining tubing on the reel 10 to form a perfectly flat
bottom as seen in FIG. 8.
The forming mandrel 82 rises and the plate 100 advances
simultaneous to each other until the forming mandrel causes the
interior of the bag to be wedged between it and the plate 100 as
seen in FIG. 3D. In this position, the forming lip 92 resiliently
creases the corner and bottom edges of the bag to form a perfectly
flat bottom. Whereupon the heating or glueing elements 90 located
on the forming mandrel heat seals or glues the gusset flaps and the
bottom seam in the form indicated in FIG. 2D. The location of the
ventilation holes 88 in the forming mandrel 82 enable the movement
of the mandrel through the bag and the escape of both heat from the
sealing element 90 as well as of air from within the bag. The
continued application of suction through the plenum boxes 60, 64
and 66 and the introduction of air under pressure through the
nozzles 98 insure that the bag remains open during the formation of
the bottom, the sealing process and the subsequent withdrawal of
the mandrel.
It will be observed from FIGS. 3C and 3D that the opening of the
bag and the insertion of the mandrel causes those portions of the
gusset folds which had been adhered to the bottom seam 16 to fold
into the triangular flaps 24 as seen in FIG. 8 and that once these
flaps are sealed a substantially unitary reinforced bottom panel 22
is provided. This arrangement occurs without the necessity of
supplying complex mechanisms for tucking and folding the flaps per
se, the same being automatically produced merely upon the
distension of the tube 12.
As seen in FIG. 3E, after the bottom panel is completed, the
forming mandrel 82 is withdrawn and the plate 100 retracted.
Suction however is maintained on the sides of the bag. Immediately
following the withdrawal of the mandrel 82, the tuck fingers 110
are caused to move inwardly against the gusset fold 14, as seen in
the dotted lines of FIG. 12. Simultaneously the upper left plenum
box 66 is retracted outwardly from alignment with the lower left
plenum box 64 leaving the bottom portion of the left side of the
bag free. The introduction of the tuck fingers 112 thus causes the
bag to fold inwardly along its gusset folds and to pivot inwardly
along the bottom portion. As soon as this tip in occurs the right
plenum box 60 and the lower left plenum box 64 are advanced
inwardly toward the center line defined by the plane of the tubing
12 causing the flap sides of the bag to again collapse inwardly. As
the lower left plenum box moves inwardly it carries with it the
ejection bar 118 as seen in FIG. 3F, along the fold line
established by the tuck fingers 110. The simultaneous inward
movement of the plenum boxes causes the tube to again collapse into
its flat state, the reinforced bottom 22 collapsing in a flat
manner over the ejection bar 118. The upper left plenum box 66 is
maintained in its rearmost position leaving a substantial amount of
space free for the collapse and movement of the bottom panel 22.
The plenum boxes 60 and 64 move inwardly until the completed bag is
substantially collapsed into a flat condition and the bottom panel
22 is folded over vertically. Prior to this point the tuck fingers
110 are withdrawn so that it does not interfere with the collapse
of the bag. Once the bag is collapsed, as seen in FIG. 3H, the
ejector bar 118 is pivoted upwardly in the direction of the
ejecting rollers 126 by activating the motor 122 to pull the rod
120 inwardly or downwardly. The motor 122 is pivoted about the
extending shaft 125 so that in its downward movement it causes the
ejecting bar 118 to move upwardly. As seen in FIG. 3H this pulls
the completed bag upwardly with it until the leading edge of the
bottom panel 22 engages between the ejecting rollers 126. The
arcuate bottom surface of the counter bar 46 of the sealing and
shearing assembly tends to direct the bag into the nip of the
rollers 126 from whence the rollers will pull the bag outwardly and
deposit it upon the take off platform 124. To prevent the bag from
sticking to the faces of the plenum boxes, a low pressure supply of
air is fed to the plenum boxes. To further assist in the direction
of the bag as it is being ejected by the ejector bar 18 and to
insure that the bottom panel 22 remains hooked over the ejector bar
118 during its upward travel, a air jet nozzle 130 as seen in FIGS.
3F and 3G can be supplied in order to direct a blast of air on the
opposite surface of the bag. The bag formation cycle is completed
once the bag is deposited on the platform 124 whereupon the
components take their initial positions as seen in FIGS. 1 and 3A,
that is the ejector bar 118 moves down into its horizontal position
and the upper left plenum box moves forwardly into alignment with
the lower left plenum box 64. The cycle may thereupon be
restarted.
It will be seen from the foregoing that a substantially simple
method and rather simple apparatus is provided for the formation of
flat bottomed plastic bags. The present apparatus and method is
particularly suitable for use with plastic raw material since the
same can be supplied in substantially endless webs facilitating its
cyclic handling. Furthermore, the use of vacuum and air enables the
handling by rather simple apparatus of thin highly flexible plastic
sheet material. In particular, the method and apparatus provides
simple means for forming a perfectly flat bottomed bag in which the
bottom is formed with a single operation.
Various modifications and changes have been suggested in the
disclosure, others will be obvious to those skilled in the present
art. It is therefore intended that the present disclosure be taken
as illustrative only of the invention and not limiting thereof.
Although throughout the disclosure the sealing or glueing elements
90 have been related to the mandrel operating in cooperation with
the presser plate 100, those skilled in the art will readily
recognize that the functions may be changed by simple rearrangement
of structures. Thus, it is within the scope of the invention to
provide that one or more or all of the elements 90 may be on the
plate 100 or that both the plate 100 and the mandrel 82 may include
such elements in facing cooperating relationship. When the elements
90 are employed for glueing, conventional glue conduits and valves
will be substituted for the electrical lines and switches without
departing from the inventive disclosure.
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