Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BAG STACKING METHOD ~ND APPARAT~S
Tha present invention relates to a method and
apparatus for stacking thermoplastic bags and more
particularly to stacking bags on sharpened pins that
penetrate the web materialO
The subject matter of the present invention is
related in substantial respect to the subject matter
disclosed in Canadian Patent ~,161,679 issued February
7, 1984 and in Canadian Patent Application S.N. 461,154
filed on August 16, 1984 which are owned by the assignee
of this present invention.
The disclosure of the referenced patent describes a
bag production technique whereby an elongate strip of
tubular thermoplastic material is provided with two or
more holes adjacent its longitudinal median. At
regularly spaced intervals the web is severed and
sealed to define a generally rectangular web portion
which is referred to as a web segment. Each segment
contains at least one hole on opposite sides of the
longitudinal median serving to be received on pins
carried by a stacking device which is part of a wicket
conveyor. Each segment, as it is produced is
transferred in an arcuate path to the stacking device.
The subject matter of the present invention has
particular utility if it is desired to produce bags,
while of the same type disclosed in a referenced patent,
but without providing holes in each web segment.
Stacking is achieved by substituting sharpened pins on
each of the stacking plates carried by the wicket
conveyor so that web segments transferred for stacking
are pierced and collected on the stacking device. Thus
the web segments need not be provided with holes and any
resistance encountered in piercing ~he web segments is
overcome by the manner in which a conventional vacuum
arm transfer device is valved to retain a firm grip on
each web segment until the segment has been pierced by
the sharpened pin.
In an apparatus, according to an aspect of this
invention, for manufacturing thermoplastic bags, from a
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roll of tubular thermoplastic web material, of the type
comprising means for removing a narrow longitudinally
extPnding median strip from one web ply, means for
sealing and severing the web transversely with respect
to the median strip thereby forming a segment of a
generally rectangular configuration, and a rotary
transfer means for transferring and stacking individual
formed segments in succession on at least one pair of
upright pins mounted to a stacking plate, the lateral
sides of the segment draping over the stacking plate,
wherein the improvement comprises the punching of
mounting holes in the segmsnt by the force of the rotary
transfer means depositing the segment on the pins
through the other web ply in the area facing the open
median strip in the one web ply, each pin having a
sharpened conical shaped head projecting upwardly from a
cylindrical shaft mounted to the stacking plate, each
shaft having a diameter substantially less than the
diameter at the base of the conical shaped head thereby
facilitating the downward sliding of the pierced segment
beyond the base of the conical shaped head without
appreciable force applied by the rotary transfer means.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is diagrammatic elevation of a major
portion of a bag making and stacking machine
incorporating the novel subject matter of the present
invention;
Figure 2 is a diagrammatic perspective showing one
form the web segment can take and the cooperation of a
seal bar and platen roll to produce a web segment;
Figure 3 is a diagrammatic prospective
illustrating the accumulation of a plurality of web
segments and a web segment which has been pierced by
pins;
Figures 4, 5 and 6 illustrate the sequence of
events occurring when a web segment is adjacent the
upper end of the sharpen pins, the deformation of the
web as the pins impart perforating stresses and piercing
of a web segment;
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Figure 7 is a plan of a stacking plate carrying a
group of accumulated web segments;
Figure ~ is an elevation of a web segment cutting
station;
Figure 9 is a plan of a modified stacking plate
provided with two stacking pins, and
Figure 10 and 11 are, respectively, an elevation
and plan of a modified cutting device and a stacking
plate wherein stacking pins are located on a medial line
and the cutting knife is relieved or slotted.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1, which is similar in substantial respects
in construction and mode of operation to the subject
matter disclosed in the 1,161,679 patent will be
described to merely point out the major components and
their organization so that the novel subject matter of
the present invention may be described in contsxt. The
overall machine, generally indicated by the numeral 10,
and its major components comprise a base plate 12
supporting a unwind stand 14 mounting for free or
controlled rotation a roll of thermoplastic materials
16. The unwound strip 18 passes over a plurality of
idle rolls, collectively identi~ied as 20, and over
upper and lower sets of idle rolls 22 and 24 carried by
tower structure 26. While not shown, the idler rolls
24 are mounted for upward and downward vertical
movement and serve to accumulate and provide a proper
amount of tension to the web strip 18. The tower
structure also is provided gusseting devices 28 to form
inward folds to the web strip. After passing through
web drive rolls 30 and another accumulatiny and
tensioning devic~ 32, the web strip 18 is intermittently
advanced by draw rolls 34 serving to project a selective
length of a web strip beyond a platen roll 36 and an
oppositely disposed heated seal bar 38. As is
conventional in the art, the time period for a draw roll
rotation is determined by the length of the web strip 18
which is projected beyond (from right to left as used in
Figure 1) the seal bar. On arresting the draw roll
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rotation the seal bar 3~3, which is elevated during web
advance, is lowered in pressure engagement with the seal
roll and accordingly the leading portion of the web,
indicated by the numeral 40, is severed and sealed
thereby defining a web segment 42 shown in Figures 2
and 3.
The leading portion of the web 40 projected beyond
the seal bar 38 is laterally supported by a series of
belts 44 traveling in a generally triangular path
defined by a plurality of rollers 46.
A rotary transf~r mechanism 48 comprising a
plurality of radially extending circumferentially spaced
hollow bars or arms 50, having their inner ends rigidly
connected a split hubs 52 and rotating about the axis of
shaft 54, and trans~er the leading portion of the
severed web 40 in an arcuate path for collection on a
conveyor 56 which comprises a plurality of stacking
plates or devices 58 each of which mount upwardl~
extending sharpened pins 60.
As shown in Figure 3, the transfer mechanism 48
includes two hubs 52 axially spaced on the shaEt 54 and
each hub mounts a set of radially extending
circumferentially spaced hollow arms or bars 50. As is
conventional the stationary portion of the split hubs 52
is connected to a source of vacuum (not shown~
communicating with each of the areas 50 which are
secured to the rotating half of the split hubs. Each of
the arms 50 is provided with a series of small diameter
holes 62 on the face of the bars that come into to
contact the leading portion of the web 40 and thereby
the web portion is grasped due to blocking of ths holes
62. The grasped web segment is transferred in an
arcuate path to one of the stacking plates 58 located at
a stacking station SS.
Figure 2 shows, in greater detail, the
relationship of the seal bar 38 and the platen roll 36.
When the seal bar 38 comes into pressure engagement
with the platen roll the leading portion 40 of the web
18 is severed and sealed to producs the web segment 42.
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It is to be understood however, that as soon as the
leading portion of the web 40 is severed and sealed it
is engaged by a pair of opposed bars 50 and transferred
as mentioned above.
Reference to Figure 3 will reveal accumulation of a
plurality of web segments 42 on a stacking plate
positioned at the stacking station SS. It also should
be noted that the web segment 42, shown in Figure 2, has
its central zone 42a free of holes or perforations in
contrast with preparation of the web segment as
disclosed in the referenced 1,161,679 patent. Figure 3
shows the stacking plate 58 provided with four upwardly
projecting pins 60 having their upper ends sharpened
such as to take the form of a pencil point so that as
the web segment 42 carried by the arms 50 approach the
stacking plate 58 the pins 60 pierce the web and
accordingly the stack of web segments assume a
registered orientation; meaning that the stack of web
segments overlie each other such that corresponding
edges are even. It is to be recognized that vacuum to
the arms 50 is maintained to a sufficient level to
firmly hold the web segments 42 until the resistance of
the film, or web to puncturing by the pins 60 has been
overcome.
With reference now to Figures 4, 5 and 6 the
progressive action involved in piercing and plunging a
web segment 42 on the pins 60 is illustrated. If
desired, the elevation of the pins 60 from the plate 58
can be made so that the upper tips of the pins 60
concurrently engage the web segment 42 and therefore all
pins penetrate the webs at the same time. It should be
recognized however that the pins can be made the same
elevation such that penetration occurs sequentially
rather than concurrently. Figure 5 illustrates
deformation of the web by the tips of the pins 60 while
Figure 6 shows the web penetrat~d by the pins. As
~" indicated above the vacuum supplied to the bars 50 is
maintained until the web segment 42 is pressed
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downwardly onto the surface of the plate 58 or the
surface of previously stacked segments.
The piercing stacking pins 60 are formed with a
conical point 62a and a transition radius 62b blending
the base or the conical point 62a with a smaller
diameter shank 62c. Providing a shank 62c of smaller
diameter than the diameter of the base of the cone 62a
facilitates producing a compact stack of web segments
since the diamstar of the hole produced by the pins 60
is substantially equal to the diameter of the base of
the cone 62a which is somewhat greater than the
diameter of the shank 62c. In this way after the web
segment was progressed beyond the base of the cone 62a
stacking is facilitated as there is no resistance to
being compactly stacked against the plate 58 or
previously stacked segments.
After a selected number of web segments have been
stacked on a particular stacking plate 58, the conveyor
is indexed (from right to left as viewed in Figure 1)
toward a cutting or a cutting and sealing mechanism 72
; which comprises a frame structure 74 supporting a pair
of concurrently operable linear actuators 76 having
their output rods 76a connected to a knife or other
suitable cutting element 78 serving to cut or cut and
combine a stack of web segments located thereunder along
the imaginary line 80 shown in Figure 7. It will be
noted that the knife is projected between the pins 60
whereby cutting along the line 80 produces two bag
stacks which are retained on the conveyor until
unloading or removal occurs.
As shown in Figure 8 the rods 76a of the actuators
76 are connected to a cross head 82 which in turn has
rigidly attached thereto by any suitable means such as
fasteners 84 the knife 7~. In order to maintain the
integrity or life of the edge 78a of the knife 7B a
deformable insert 86, which may be a strip of wood, is
affixed to the plate 58 and forcibly engaged by the
knife edge 78a in the course of dividing the stack of
web segments into individual bag stacks.
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Figure 9 shows a modification whereby each plate
58 mounts two pins 60 located on either side of the
imaginary parting line 80. Figures 10 and 11
illustrate in a modified form wherein thP pins 60 are
located on the imaginary line 80 and that the knife 78,
by being formed with slots 88, to provide clearance for
the pins 60, cuts the web segments along the line 80
but with interrupted uncut portions corresponding to
the slots 88. If one chose to produce bag stacks be
using the construction shown in Figures 10 and the
portion of the web material that can be allocated to
define the volume of the bag would be increased.
Although the best mode contemplated for carrying
out the present invention has been herein shown and
described, it will be apparent that modification and
variation may be made without departing from what is
regarded to be the subject matter of the invention.
