System for serially conveying discrete flexible articles

A system for serially conveying discrete flexible articles including a plurality of sequentially activated Coanda nozzles disposed along an article flow path and article support means cooperable with the nozzles to propel and stabilize the articles.

BACKGROUND OF INVENTION 
1. Field of Invention 
This invention relates to an apparatus and method for serially conveying 
discrete flexible articles such as plastic bags between a first station 
and a second station and incorporating means for stabilizing the articles 
during conveyance thereof. 
2. Description of the Prior Art 
The present invention has application to any operating environment wherein 
it is desired to serially convey discrete flexible articles while at the 
same time maintaining stability of the articles to ensure their accurate 
positioning at the end of the conveying operation. The invention has 
particular application to commercial plastic bread bag machines wherein 
the highly flexible and thin bags must be conveyed under high speeds to a 
stacking station whereat the bags must be in precise registry with the 
stacking mechanism. Rope or belt conveyors have conventionally been used 
in the plastic bag industry to assist in transporting the bags to a 
stacking station. Such mechanical conveyors, however, have had a number of 
drawbacks. Not only are such mechanical arrangements subject to wear, they 
are also very limited as to performance. If operated at high production 
rates the rope or belt conveyors often cannot maintain the accuracy of 
placement required by the stacking mechanism. The rope or belt conveyors 
conventionally merely provide support surfaces for the bags or other 
flexible articles being conveyed and such moving articles tend to float 
over the surfaces and curl at the leading edges thereof. Air jets have 
been employed in an attempt to maintain the articles flattened in position 
on the support surfaces but these arrangements have proven to be 
unsatisfactory, in many cases actually exacerbating the conditions of 
turbulence which distort the articles and prevent proper registration with 
the stacking mechanism. Plastic bread bags and similar articles 
conventionally have apertures found at one end thereof to permit stacking 
over wickets. The article ends must be in precise registry with the 
stacking mechanism that accomplishes this. Prior art rope mechanisms often 
result in distortion at the article ends, additionally contributing to 
poor stacking and consequent production losses. 
The present invention employs a gaseous flow to convey the bag or other 
flexible article to a predetermined station such as a pick-up or stacking 
station. While air tables and similar arrangements are known and widely 
used in the conveying art, such prior art devices are incapable of 
transporting plastic bread bags or other similar thin discrete articles at 
high speeds and under conditions ensuring nondistortion of the bags during 
transport and their accurate placement at the end of the conveying 
operation. Representative prior art patents are U.S. Pat. Nos. 2,805,898, 
3,198,515, 3,633,281, 3,650,043, 3,705,676, 3,721,472, 3,773,391, 
3,999,696, 4,014,487, 4,081,201, 4,087,133, 4,136,808 and 4,186,860. By 
means of air flows the present invention not only imparts propelling 
forces to the article but also imparts downward and endwise suction forces 
to straighten the article and maintain it in a generally flat condition. 
BRIEF SUMMARY OF THE INVENTION 
According to the teachings of a preferred embodiment of the present 
invention, a plurality of Coanda nozzles are positioned along a flow path 
between a source of discrete flexible articles and a downstream station. 
Article support means is disposed between the Coanda nozzles defining 
spaced generally flat support surfaces and a plurality of apertures 
between these surfaces and in communication therewith. The nozzles and the 
article support means cooperate to separate gaseous flow induced by at 
least one of the nozzles into a laminar fluid flow component directed 
along the support surfaces toward the downstream station to propel the 
articles and exert a downward pull thereon and a vented more turbulent 
fluid flow component directed through the apertures. The venting reduces 
the thickness of the gaseous flow over the support surfaces to reduce air 
disturbances that would otherwise be imparted to the articles during 
conveyance thereof. Further stability is imparted to the conveyed articles 
by auxilliary fluid flow generating means exerting pulling forces on the 
articles during conveyance thereof in generally opposed directions 
laterally disposed relative to the flow path. The system incorporates an 
adjustment mechanism to accommodate articles of different sizes.

DETAILED DESCRIPTION 
FIG. 1 schematically illustrates apparatus 10 constructed in accordance 
with the teachings of the present invention disposed between a source 12 
of discrete flexible articles and a pickup station generally indicated by 
reference numeral 14. The articles to be conveyed by the arrangement 
illustrated in FIGS. 1 and 2 are flexible plastic bread bags 16 of the 
type, for example, shown in detail in FIG. 3. It will be seen with 
reference to that figure that bag 16 has a gusset end 17 and spaced 
apertures 18 formed at a lip end 19 thereof during the manufacturing 
process. Such apertures are used in the prior art to align a plurality of 
bags into a precise stacked relationship whereby the bags may be packaged 
and shipped as a unit to the end user. Stacking alignment of the bags is 
accomplished by serially placing the bags over bag stacking wickets or 
spindles and positioning the wickets or spindles in the apertures. FIG. 1 
illustrates wickets or spindles 20 accommodating a plurality of bags 16 
and awaiting the receipt of more. FIGS. 1 and 2 illustrate a conventional 
arrangement for serially picking up bread bags and delivering them to the 
wickets. Such an arrangement comprises spaced pick-up and delivery units 
22 and 24 each of which comprises a rotatable hub 26 from which radially 
project a plurality of arms 28. Arms 28 are hollow and are in selective 
communication with any suitable vacuum source. Each arm (as may best be 
seen with reference to FIG. 4) has a plurality of holes 30 formed 
longitudinally therealong which enable the arms to apply a vacuum to 
opposed ends of the bags and secure the bags in position relative to the 
arms while the pick up and delivery units deliver the bags to the wickets 
with the bag apertures 18 in alignment therewith. The pick-up and delivery 
units per se are known in the prior art and will not be described further. 
It should be noted, however, that precise delivery of the bags by the 
pick-up and delivery units may only be accomplished if the bags are 
initially put into precise placement relative to the pick-up and delivery 
units themselves. Such placement becomes progressively more difficult as 
the speed of delivery of the bags to the pick-up and delivery units 
increases or the thickness of the film used to manufacture the bags 
decreases. It is the function of the apparatus 10 of the present invention 
to provide fast and accurate delivery of the bags to the station occupied 
by the pick-up and delivery units even when the bags are constructed of 
film of 1 mil or less. Such bags are delivered to apparatus 10 from a 
suitable source 12 of the bags which would normally be the downstream end 
of conventional plastic bread bag forming equipment. Because of its 
conventional nature such equipment will not be described in detail. 
Suffice it to say that the finished bags exit from source 12 in discrete 
serial fashion and are delivered to the upper surface of apparatus 10. 
Details of a preferred form of apparatus 10 may best be seen with reference 
to FIGS. 4-10. Apparatus 10 includes a plurality of Coanda nozzles 40, 42, 
and 44 disposed in spaced relationship between station 12 and station 14. 
Each Coanda nozzle is divided into two Coanda nozzle segments, Coanda 
nozzle 40 comprising segments 40a and 40b, Coanda nozzle 42 comprising 
segments 42a and 42b and Coanda nozzle 44 comprising segments 44a and 44b. 
As may perhaps best be seen with reference to FIGS. 5 and 6 each nozzle 
segment comprises a body member 46 defining a generally smoothly curved 
Coanda fluid flow attachment surface 48. A first elongated slit 50 is 
defined by the fluid flow attachment surface and a front wall element 52 
of the body member. Slit 50 leads from a plenum 54 formed by the body 
member. Each plenum 54 is connected to the outlet of a solenoid valve 58 
close coupled to each Coanda nozzle. Each valve 58 is in fluid flow 
communication with a suitable source (not shown) of pressurized air and 
each valve 58 is operatively connected to a sequential timer device 60 of 
any suitable type which controls the timing and duration of air supply to 
the Coanda nozzles in a manner to be more fully described below. 
Disposed at the upstream or leading edge of each Coanda nozzle segment is a 
cover element defining an open ended cavity with the Coanda fluid flow 
attachment surface 48 of the nozzle. FIG. 6 shows a representative cover 
element 62 employed in connection with nozzle segment 42. Cover element 62 
is flat at the top thereof and includes an extended lip 66 positioned over 
elongated slit 50 to define the open ended cavity 68 in fluid flow 
communication with elongated slit 50 and for receiving pressurized fluid 
flow therefrom. Extended lip 66 of cover element 62 defines a second 
elongated slit 70 for receiving a flow of pressurized air after it has 
passed through elongated slit 50. The width of the second elongated slit 
70 is greater than the width of the first elongated slit 50, the width of 
the first elongated slit preferably being in the range of from about 0.002 
inches to about 0.004 inches and the width of the second elongated slit 70 
being in the range of from about 0.015 inches to about 0.035 inches. 
Pressurized air passing through slit 50 will attach itself to the Coanda 
fluid flow attachment surface 48 of each nozzle and follow the contours of 
the surface in the manner shown by the arrows in FIG. 6 so that the 
pressurized air passes upwardly through slit 70 and flows along the top of 
each nozzle. In the case of nozzles 40 and 42 the Coanda air flow will 
then be directed toward article support means positioned downstream 
therefrom. The article support means comprises a plurality of overlapping 
finger elements extending between nozzles 40 and 42 and between nozzles 42 
and 44. Since the construction of the article support means associated 
with each of the Coanda nozzle segments is essentially the same, only that 
in operative association with nozzle segment 40a will be described in 
detail. 
The article support means operatively associated with Coanda nozzle segment 
40a includes a plurality of spaced support fingers 74 integrally formed in 
connection with cover element 62 and projecting upstream toward nozzle 
segment 40a. Overlapping and in registry with spaced support fingers 74 
are a plurality of upper fingers 78 attached by screws or other means to 
body member 46 of nozzle segment 40a at the location where surface 48 
turns downward. Since the support fingers and upper fingers are attached 
only at one end they are slidably engageable with one another in the event 
the relative positions of nozzle segments 40a and nozzle 42a are changed. 
As will be described in greater detail below, such nozzles are relatively 
adjustable to accommodate bags or other articles of differing widths. The 
fingers slide relative to one another and will not impede such adjustment. 
Defined by and between the fingers are spaced elongated apertures 80, the 
longitudinal dimensions of which may also of course be varied by moving 
nozzle segments 40a and 42a relative to one another. The nozzles and their 
associated article support fingers cooperate to separate gaseous flow 
induced by the nozzle into a laminar fluid flow component directed along 
the support surfaces defined by the upper surfaces of the fingers toward 
the pick-up station 14 to propel the bags therealong and exert a downward 
pull thereon in a direction substantially normal to the support surfaces 
and a vented fluid flow component directed downwardly through apertures 
80. The gaseous flow passing over each nozzle segment tends to destabilize 
and become turbulent at the location where surface 48 turns down. The flow 
becomes thicker due, among other factors, to entrainment of ambient air 
and if a portion of the air is not vented air disturbances will cause the 
bag to wrinkle and distort. This venting function is illustrated 
schematically by the air flow arrows shown in FIG. 6. Generally about 1/2 
to 1/3 of the air flow is vented off, resulting in the moving air cushion 
flowing along the finger upper surfaces being thinner and more stable. 
As will be pointed out later in more detail, air flow through each of the 
Coanda nozzle segments is turned on and off in rapid fashion during 
operation of the present apparatus. To rapidly pulse in sequence high air 
pressures but narrow slits accomodating small quantities of air for each 
nozzle segment are requirements. This results in a high magnitude suction 
being found in the vicinity of slit 50 which could distort and foreshorten 
the bags if placed in too close a proximity thereto. Such suction could 
also temporarily interrupt forward movement of such bag. The cover element 
62 prevents this from occurring by keeping each bag removed from slit 50. 
Slit 70, however, being substantially wider than slit 50, will not 
interfere with the flow of pressurized air therefrom despite the fact that 
such air flow progressively thickens after it leaves slit 50. 
The cover element also serves to protect the narrower slit 50 from 
plugging, a problem that may occur when slip agents or other similar 
materials are incorporated in or on the bag. It has been found that such 
an arrangement also creates a more stable thin air layer for applying 
propulsive forces to the bags by limiting entrainment of ambient air. 
Because of the nature of the nozzle and the combination thereof with the 
fingers of the article support means turbulent flows are minimized as is 
bag flutter. 
The present arrangement additionally comprises auxilliary fluid flow 
generating means for applying opposed air flow forces at the bag ends 
preventing flutter and other undesired distortions of the unsupported bag 
ends during conveyance on the article support means and for controlling 
placement of the bag. The auxilliary fluid flow generating means is in the 
form of auxilliary Coanda nozzles positioned along the bag flow path under 
the unsupported bag ends and adapted to pull the bag lengthwise (in the 
cross machine direction) and straighten the bag as it is propelled along 
the flow path by the Coanda nozzles 40, 42 and 44. Details of the 
auxilliary Coanda nozzles are particularly evident with reference to FIGS. 
4 and 7-10. An auxilliary Coanda nozzle 90 is disposed along the left side 
of the flow path as viewed in FIG. 7 and an auxilliary Coanda nozzle 92 
generally of like construction is disposed along the right hand side of 
the flow path as viewed in that figure. Since the auxilliary Coanda 
nozzles are essentially mirror images of one another, only the details of 
construction of auxilliary Coanda nozzle 92 will be described, with 
particular reference being made to FIG. 8. Auxilliary Coanda nozzle 92 
includes an elongated element 94 extending virtually along the full length 
of the path of movement of the bags. A plurality of bores 98 are formed 
near the top of the elongated element and such spaced bores are in 
continuous communication with a source of pressurized air through 
throughbore 100 formed in the elongated element. The generally laterally 
disposed outlets of bores 98 are adapted to be positioned beneath the free 
opposed terminal portions of the bags. The bores are preferably canted 
slightly in the direction of bag movement so as not to impede such 
movement while exerting a pulling force on the bag ends. A downwardly 
directed lip 102 projects adjacent to the bore outlets, said lip being 
continuous and extending along the length of the bag flow path. 
It should be noted that lip 102 diverges downwardly from the horizontal at 
an angle thereto. Such lip functions as a Coanda surface diverting the air 
exiting from bores 98 downwardly. This downward air movement creates 
suction below the lip and gusset ends. It has been found that failure to 
so direct the pressurized air will result in undesirable upward curling 
and other distortion of the bag ends by the air exiting from bores 98. 
When the apparatus of the present invention is utilized in conjunction 
with plastic bread bags of the type shown in FIG. 3 it will be appreciated 
that the bag ends are different. The lip end 19 of the bag wherein 
apertures 18 are located consists of a single layer while the gusset end 
17 of the bag is actually comprised of four overlapping film layers. Thus, 
each end requires a different controlling and support force. This is 
accomplished either by different air pressures at auxilliary Coanda 
nozzles 90 and 92, by having a different nozzle geometry at each bag end, 
or a combination of both. In a configuration of the type shown in FIGS. 7 
and 8 the additional transverse support needed by the heavier gusset end 
of the bag is, for example, accomplished by canting the bores 98 at 
different angles or at auxilliary Coanda nozzles 90 and 92 whereby (as may 
perhaps best be seen in FIGS. 9 and 10) the air streams directed from the 
bores at the lip end of the bag are directed at a 45.degree. angle to the 
cross machine direction while the angle of the bores at the gusset end are 
disposed at only 30.degree.. Some variation in pressures of gas fed to the 
auxilliary Coanda nozzles may also be employed for this purpose. The 
objective of the auxilliary Coanda nozzles is to control the stability of 
the overhanging ends of the bag and also ensure proper cross machine 
placement of the bag and that the bag travels without skewing, i.e. one 
end moving faster than the other. The air pressures applied to the 
auxilliary Coanda nozzles are the primary means for controlling bag 
placement. By varying the pressures the bags can be "steered." 
Representative air pressures in a plastic bread bag line were 10-14 psig 
at the lip end and 4-8 psig at the gusset end. It is to be understood, 
however, that the factors of nozzle geometry and pressures are, as stated 
above, dictated by the nature of the article being conveyed. With further 
reference to the overhanging lip 102 it has been found that an undercut as 
shown in FIGS. 7 and 8 is essential. Otherwise, the fluid flow along the 
top of the lip will continue to flow downwardly and pull down the bag ends 
to an undesirable degree. 
While the auxilliary Coanda nozzles 90 and 92 are operated under continuous 
flow conditions, such is not the case for Coanda nozzles 40, 42 and 44. 
Coanda nozzles 40, 42 and 44 are operated in timed sequence so that the 
bags transported by the apparatus are not distorted during conveyance 
thereof. It will be appreciated, of course, that transport of the bags or 
other articles on apparatus 10 must be coordinated with the rotation of 
vacuum arms 28 at pick-up station 14. The rotating hub supporting arms 28 
is positioned below the bag support surface of apparatus 10 as defined by 
the fingers 78. Consequently, as each arm is rotated into position along 
the sides of apparatus 10 the outwardly extended ends of the bag will be 
contacted by the arms and secured thereto by the vacuum in the arms. 
Assuming that a bag has already been positioned on top of apparatus 10 and 
transported thereby Coanda nozzle 40 is off and the bag on apparatus 10 
will first be contacted by the arms at the location of nozzle 40. Nozzles 
42 and 44 are also off at this time. Immediately upon engagement of the 
bag at the vicinity of Coanda nozzle 40 by the spaced pick-up arms 28 and 
lifting of the bag thereby, pressurized air will be supplied to the 
segments of Coanda nozzle 40 so that another bag exiting from source 12 
will be picked up thereby and movement along apparatus 10 initiated. When 
the leading edge of the bag approaches nozzle 42, nozzle 42 is actuated 
and nozzle 40 is again turned off. In like manner when the leading edge of 
the bag is close to Coanda nozzle 44, Coanda nozzle 42 is deactivated. In 
other words, the nozzles are sequentially turned on and off as the bag 
moves along the support fingers of the apparatus. Any suitable timer 
mechanism may be utilized to accomplish this objective. In an actual 
embodiment constructed in accordance with the teachings of the present 
invention three cams on a drive mechanism were used in combination with 
proximity switches to control nozzle flow. 
In an apparatus constructed in accordance with the teachings of the present 
invention air flow to each pair of Coanda nozzle segments was controlled 
by a single pressure regulator. Air lines from the regulator to the 
corresponding pair of solenoids was constructed of identical length to 
minimize possible nozzle cavity pressure differences. The nozzle slits 
were set very accurately so that they were equal in each segment of each 
nozzle. In fact, all nozzle segments had the same slit characteristics and 
slit 50 was in the range of 0.002-0.004 inches for each. The pressures 
measured at the regulators with respect to each nozzle were as follows: 
Nozzle 40--40-46 psig 
Nozzle 42--30-38 psig 
Nozzle 44--20-24 psig 
These figures include pressure drops across the solenoids and supply lines 
to them. It should be noted that the initial or pick-up nozzle 40 had the 
highest pressure since a greater force is required for initial bag 
pick-up. 
As stated above, it is considered desirable to make apparatus 10 adjustable 
so that it may accommodate various sized bags or other articles. Each of 
the segments of Coanda nozzles 40, 42 and 44 and its associated valve 48 
may be selectively movably positioned relative to the other components of 
apparatus 10 in the direction of movement of the bags. The frames 110 
within which each Coanda nozzle segment is positioned have elongated slots 
112 formed in the inner sides thereof to accomodate projections or keys 
114 connected to each segment body. Interconnected threaded rods 115 and 
116 threadedly secured to the segments of nozzles 42 and 44 may be turned 
by handle 117 to move the segments. Rod 115 has half the pitch of rod 116 
so that the segments of nozzle 42 will move half the distance the segments 
of nozzle 44 are moved, thus ensuring that nozzle 42 is substantially 
midway between nozzles 40 and 44. It is also felt desirable to provide 
some means whereby the segments of each Coanda nozzle may be moved toward 
and away from one another to accomodate bags or other articles of various 
lengths. This may be accomplished by mounting frames 110 on threaded 
connectors 120 whereby the frames 110 can be slid to the desired position 
and secured into place by means of lock nuts 122 or other desired 
mechanism to maintain the frames 110 and thus the Coanda nozzle segments 
at the desired distances from one another.