Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates generally to improved method and appara-
tus fox applying printed labels to flexible packaging envelopes and more
particularly to such labeling carried out reciprocally so that both sides
of such envelopes are labeled in registration.
It is typical for thermoplastic packaging bags to bear printed
labels of advertising material or content description. Bags may be labeled
after manufacture, or, alternatively, bags may be formed from a stock of
thermoplastic film material which has already been labeled before con-
version into the packaging envelope. It is known to bond a thermoplastic
fil~ bearing labeling indicia to a thermoplastic packaging bag by corona
discharge treating the film faces to be bonded and then contacting those
faces afterwhich they adhere together permanently. Othex energetic
adherent surface treatments are known.
In making thermoplastic packaging bags, it is conventional to
make a series of such bags from a flattened seamless tubular film of
indefinite length. A series of end-seal bags may be made by transversely
heat sealing across the width of the flattened tubing, followed by sever-
ing the tubing so that the transverse seal forms the bottom of a bag. A
series of side-seal bags may be made similarly except that the transverse
seals form the bag sides and one edge of the collapsed tubing forms the
bottom of the bags.
Of general interest is the disclosuxe of U.S. Patent 4,120,716
for "Method of Applying Printed ~abels to Flexible Envelopes Using Corona
Discharge Treatment" issued October 17, 1978 to Bonet, wherein a labeling
method is disclosecl that includes bonding a labeling film to a collapsed
tubular film by corona treating the faces o:E the respective films to be
brought into contact and then contacting the treated film faces without
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application o-F heat to bond the labeling film to the tubular substrate.
It is a primary object of the present invention to provide for
reciprocal labeling of an advancing collapsed tubular film preliminary to
bag making whereby reciprocal labels are bonded to opposite sides of the
collapsed film at regular intervals such that the labels of each re-
ciprocal set are in registration respectively.
SUMMARY OF T~E INVENTION
In accordance with the present invention, there is provided a
method for reciprocal labeling of packaging envelopes comprising (a)
advancing a collapsed tubular polymeric film of indefinite length and
adherently treating the outer surface of the collapsed film, Ib3 advancing
a printed web of indefinite length, having printed along one sllrface
-thereof a regularly repetitive pattern of reverse-printed reciprocal
label sets, and adherently treating the printed surface of the web, (c)
longitudinally slitting the advancing web between reciprocal prints to
form two reciprocal label strips, and (d) advancing the label strips
oppositely alongside the advancing collapsed film such that the adherently
treated surfaces of the strips are adjacent opposing sides of the col-
lapsed film respectively and adjusting the registration of printed matter
between said label strips, and (e~ then directing the strips into bonding
contact with the collapsed film.
The term "adherently treating" is intended to refer to energetic
treatment of a surface, especially a polymeric surface~ to impart adhesive
properties thereto, such as by corona discharge, flame, ultra violet, or
plasma treatment. Preferably, such treatment is by corona discharge.
Since the reciprocal label strips are formed from a single
printed web, control of registration of reciprocal label sets ill the
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final bonded configuration is greatly facilitated, with no control being
necessary after initial regis-tration set-up in most cafies.
Additionally, there is provided apparatlls for reciprocal label-
ing of packaging envelopes comprising (a) means for adherently treating
the outer surface of an advancing collapsed tubular film, ~b) means for
adherently treating the printed surface of an advancing reverse-printed
web, having printed along one surface thereof a regularly repetitive
pattern of reverse-printed reciprocal label sets, (c) means for longitu-
dinally slitting the advancing web between reciprocal prints to form two
reciprocal label strips, (d) means for advancing the label strips
oppositely alongside the advancing collapsed film such that the adherently
treated surfaces of the strips are adjacent opposing sides of the col-
lapsed film respectively and adjusting the registration of printed matter
between said label strips, and (e) means for directing the strips into
bonding contact with the collapsed film.
BRIEF DESCRIPTION QF THE DRAWINGS
Further details are given below with reference to the drawings
wherein:
FIG. 1 is a schematic side-view of a process line for reciprocal
labeling of a collapsed tubular film according to an embodiment of the
invention; and
FIG. 2 is a schematic side-view of an auxiliary process line
feeding labeling material to the main process line of the previous figure.
DESCRIPTION OF THE PREFERRFD EMBODIMENTS
Referring specifically to the drawings, in FIG. 1 a schematic
side-view of the ma:in process line according to a preferred embodiment of
the invention is shown wherein a collapsed tubular film of indefini-te
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length is reciprocally labeled preliminary to converting the tube into a
series of packaging bags. ~ conventional extrusion unit 12 extrudes an
inflated tube 14 of thermoplastic packaging film which is then collapsed
to a lay-flat conEiguration by a pair of pinch rollers 16, the collapsed
tubular film being indicated at 18. A representative packaging film is
composed of polyethylene. Alternatively, the tubular film may be supplied
in roll form which when fed out from the roll is preferably inflated as
at 14 to break any cling of the in-terior surfaces of the tube as may
result from compression in roll form. The collapsed tubular film 18 is
then advanced in-line to a corona treatment unit 20 wherein one side of
the collapsed tubular film is corona treated between conventional corona
Ullit 22a and discharge roller 23a followed by treatment of the opposing
side of the collapsed tubular film between corona unit 22b and discharge
roller 23b. The collapsed tubular film exits the corona treatment unit
20 at 24 having had substantially its entire outer surface treated by
corona discharge. The treated collapsed film 2~ is then advanced in-line
between reciprocal label strips 26a,b and then to bonding roller 34 where
the tubular film is reciprocally labeled, i.e. the collapsed film is
oppositely labeled on its exterior lay-flat sufaces such that labels of
each reciprocal label set are substantially in registration. The plane
of the main process line 10 is indicated by line 1-1.
Labeling material is fed to the main process line 10 from
auxiliary process line 50 as discussed below in connection with FIG. 2,
the auxiliary line being aligned in plane 2-2 generally perpendicular to
plane 1~ pper label strip 26a is fed to the main process line 10 over
a conventional 45 turn bar 28a as indicated at location 27a and exits
under turn bar 28a so that upper label strip 26a travels parallel and
adjacent to collapse!d tubular film 24 and is then direc-ted over roller
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32a and then to bonding roller 34. As discussed below, upper label strip
26a has reverse-printed labeling ma-t-ter on its lower surface, this same
surface having been corona ~reated for bonding to collapsed film 24.
Collapsed film 24 is reciprocally labeled on its underside with label
strip 26b which is fed from auxiliary process line 50 over a 45 turn bar
28b as indicated at location 27b to exit under turn bar 28b and is then
passed over reversing rollers 30 and 31 so that lower label strip 26b is
traveling with and adjacent to collapsed tubular film 24. As discussed
below, lower label strip 26b has reverse-printed labeling matter on its
upper surface, this same surface having been corona treated. The lower
label strip 26b is next passed over roller 32b and onto bonding roller 34
so that at bonding roller 34, by virtue of tension roller 40, upper label
strip 26a and lower label strip 26b are urged against opposite surfaces
of collapsed tubwlar film 24, whereupon the label strips are permanently
bonded to the collapsed film at 36. The bonded configuration at 36 is
then directed from bonding roller 34 around tension roller 40 whereupon
the reciprocally labeled tubular film at 42 exits the main process line
and is either directly advanced to a bag making operation as discussed
above or is accumulated in roll form for later bag making. It is noted
that the printed labels in the final bonded configuration will lie between
the label strips and the tubular film, respectively, to provide abrasion
protection for the labels thereby preserving labeling appeal and also to
impart an attractive glossy appearance. Since the labeling material will
be read in reverse in this configuration, the labels must be initially
reverse~printed.
In FIG. 2, there is schematically shown auxiliary process line
50 which feeds main pr~cess line 10, auxiliary line 50 lying in plane 2-2
which is preEerably perpendicular to the main process line 10 lying in
plane 1-1. Allxiliary line 50 begins with the provision of a roll of
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printed web 5l, having printed along one surface thereof a regularly
repetitive pattern of reverse-printed reciprocal label sets, from which
label strips 26a,b are prepared. The term "reciprocal label set" is
intended to imply that front and back labels of each label set are simul-
taneously printed side-by-side on the web 51. This reciprocal printing
arrangement is advantageous in that registration between front and back
labels in the final bonded configuration is easily achieved, due to the
regularity of repeat spacing between front labels and back labels respec-
tively, and further in that any need for a two-side printing press is
eliminated. The web is composed of a thermoplastic material compatible
with the thermoplastic ~aterial of the collapsed tubular film. The
~upply of printed web is fed out at 52 and advanced in-line to corona
treatment unit 54 where the printed side of the web is subjected -~o
corona discharge treatment between conventional corona unit 55 and dis-
charge roller 56. The corona treated web is then advanced to slitter 58
which cuts the web longitudinally along a line lying between front and
back labels of each reciprocal label set, such that at location 60 two
reciprocal label strips will be advancing side-by-side and upon being
passed over roller 62 are separated into upper label strip 26a and lower
label strip 26b. ~ower label strip 26b is then directed onto turn bar
28b at 64 where it is passed around the bar in the direction of arrow 29b
and exits under the bar as indica-ted at 65 (flowing into the plane of the
drawing~. Since label strip 26b at this point will be advancing opposite
that of collapsed tubular film 24, i-t is then reversed over rollers 30
and 31, as discwssed above, such that strip 26b exits over reversing
roller 31 as indicated at 66 having been rotated in the direction indicat-
ed by arrow 33.
Referrirlg to the point of separation of upper and lower label
strips at roller 62, upper label strip 26a is passed through a longitu-
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dinal registration control unit 70 having reversing rollers 71 and 74 and
tension rollers 72 and 73. Tension rollers 72 and 73 operate in unison
by reciprocal displacement about center of rotation 75 so that as tension
rollers 72 and 73 are displaced the inventory of upper label strip 26a is
varied within controller 70. In general, longitudinal registration
control is accomplished by selectively adjusting the path length of one
of the label strips. Upper label strip 26a exits ~rom registration
controller 70 over turn bar 28a as indicated generally at 68 and rotates
about 45 turn bar 28a in the direction indicated by arrow 29a to exit
under the bar as indicated at 69. Upon upper label strip 26a exiting
under turn bar 28a at 6g and upon lower labeling strip 2~b exiting over
reverse roller 31 at 66, upper and lower strips 26a,b will be travelling
adjacent to and with collapsed tubular film 24 such that the corona
treated surfaces of labeling strips 26a,b are towards collapsed film 24
respectively. It is noted that the label strips are routed so as not to
abrade their corona treated surfaces or the printed matter thereon, this
being possible since both featu~es are on the same surfaces, respec-
tively. Additionally, it is preferred that sliding friction over the
turn bars be minimized, so as not to irregularly stretch the label
strips, by air-lubricating the turn bars or by providing a low friction
coating such as Teflon. Transverse registration of printed matter
, ~ ~ .,.
between the label strips is simply adjusted by varying the longitudinal
spacing between the turn bars 28a,b, i.e. by shifting one or both of the
turn bars along the longitudinal direction of tubular film 24 the trans-
verse location of the respective label strips will be shif-ted across the
tubular film.
A key advantage o~ the invention is that in most cases con-
tinllolls registration control is not required after initial longitudinal
a J~ rnu ~ ~
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and transverse registration adjustment as described above. This advan-
tage arises from the requirement that front and back label strips are
formed from a single web on which are printed reciprocal label sets so
that front and back labels are always juxtaposed and have the same repeat
distance. However, in cases where there is a defect in the regularity of
the web, such as a deficiency in planarity~ continuous monitoring of
registration with feedback control may optionally be provided if the
irregular web is to be used. For example and referring to FIG. 1, in the
vicinity of location 36 where label strips 26a,b have been bonded to
tubular film 2~ on bonding roller 34, the registration of upper and lower
reciprocal labeling is continuously monitored. A preferred location for
registration monitoring is just down-course from rollers 32a,b. Alterna-
tively though less preferred, monitoring may be conducted after bonding
just down-course from 36. In response to this registration monitoring,
longitudinal registration control unit 70 is automatically adjusted
accordingly, and likewise for transverse registration via turn bar spac-
ing, to maintain registration of reciprocal labeling within acceptable
limits. Monitoring can be conducted by conventional means, for example by
a photoelectric detector cell pair to optically sense two dimensional
registration of each reciprocal label set.
Regarding bag making from the reciprocally labeled collapsed
tubular film, proper orientation of printed ma-tter on the label strips
must be predetermined. If side-sealed bags are made such that the folded
edges of the collapsed tubing form the top and bottom of a bag, then the
label strips will extend across the bag, and printed matter on the label
strips will usually be oriented transversely on the strip. On -the other
hand, if end-seal bags are made from the collapsed tubing, the label
strips wilL extend lengthwise of the bag, and printed matter on the label
strips will usually be oriented lengthwise on the strips. It is noted
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that the label strips will typically be of a wid-th less than the width of
the collapsed tubing~ Transverse location of the label strips on the
tubing is as desired and, for example, will be placed towards the edge of
the tubing that will form the bag bottom :in the case of side-seal bags.
Although the present invention has been described in conjunc-
tiOIl with preferred embodiments, it is to be understood that modifica-
tions and variations may be utilized without departing from the prin-
ciples and scope of the invention, as those skilled in the art will
readily understand. Accordingly, such modifications and variations may
be practiced within the scope Gf the following claims:
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