Note: Descriptions are shown in the official language in which they were submitted.
~3046~3
This invention relates -to a method o forming sandwich
structures, comprising one or more non-corrugated sheet
elements (liners) to which are bon~ed two or more corruyated
(fluted) sheet elements (mediums) which are themselves bonded
together.
~ pplicant's copending Canadian 517,430, filed September
3, 1986 discloses an improved corrugated paper board structure
in which two or more layers of corrugated medium (flutes) are
bonded together at the peaks of the flutes, and are sandwiched
between two outer liners.
The above-identified paten-t application also discloses
a method of forming the structural paper in which two or more
separate layers of corrugating medium are corrugated and then
brought into flute tip to flute tip contact on synchronised
corrugating rollers.
That method does not address the problem of capital
cost in constructing a new corrugating plant for the flute to
flute paper board and the likely under utilization of existing
corrugating machinery, making conventional flute to liner
corrugated boards.
It is an object of this invention to provide a
modification to existing corrugating machinery to enable
conventional corrugated board, as well as the new flute to
flute corrugated board, to be made. The modification can also
be incorporated into the manufacture of new corrugating
machinery to enable conventional corrugated board with improved
printing properties and visual appearance to be also made.
Conventional machinery for forming corrugated board
incorporates a unit for making single faced corrugated board,
that is a liner adhered to a single fluted layer. More complex
board constructions can be formed by bonding the exposed flutes
to another liner and, if desired, subsequently bonding that to
another single faced corrugated board.
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A "slngle facer" plant normally include~ a~ lt6
essential components:
a) Mill roll stands for liner and corrugatlng
medium.
b) A pair of corrugating roller6 for corrugating
the medium into a fluted medium.
c) A pair o~ heated smooth (non corrugated) guide
rolls for the liner board.
d) A non corrugated pres~ure roll for bringing the
liner into contact with the second corrugating
roller to form the single ~acsd board.
e) An idler roll to guide the formed single faced
board to subsequent processing unltfi.
With conventional single faced board a degree of
pressure is applied to ensure secure bonding between the
liner and the corrugated medium. This application of
pressure create6 pressure lines on the outer face of the
liner corresponding to the position of the flute tlps. The
need to apply pressure can adversely affect the strength of
the single faced structure and adverse~y affect6 the
appearance of the board and its suitability for printing.
It is also an object of this invention to overcome
these deficiencies in the conventional product.
To this end the present invention provides a method
for bonding a liner to a corrugated medium or mediums in
which adhesive is applied to the flute tips of the
corrugated medium. The liner is then brought into contact
with the corrugated medium or mediums and the assembled
liner and corrugated medium or mediums may be subjected to
heat, or other energy or chemical process to initiate or
assist in completion of the bonding. This low pressure
method of bonding gives superior bond strength (pin
adhesion) than is achieved in conventional single-faced
board.
In another aspect this invention provides a
modified single face corrugated board making apparatus
capable of forming corrugated boards having two fluted
mediums bonded together at the flute tips comprising
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a) Mill roll stands for two medium~ and one liner.
b) Two pairs of corrugating rolls synchroniæed so that
the two fluted mediums are oriented for precise
flute tip to flute tip bonding and which may
include pressure bonding.
c) A carrier roll juxtaposed to one of the corrugating
rolls and adapted to support and constrain
continuously the bonded fluted mediums during the
development of the adhesive bond. This
juxtaposition assists in achieving the required
constraint for the joined mediums after bonding of
flute tips and before bonding of the first liner.
d) A first adhesive application station adapted to
apply adhesive to one of said fluted mediums prior
to the flute tips of the said fluted mediums coming
into contact.
e) A second adhesive applicator station to apply
adhesive to the exposed flute tips of the bonded
mediums or to a liner board.
f) A liner applicator roll located adjacent to said
carrier roll downstream o said second adhesive
applicator adapted to apply a liner board to said
bonded fluted mediums.
This invention also provides the following
25 modification to enable the modified conventional single
facer machine-to make both conventional single faced board
and flute to flute board.
The modification comprises:
i) Substituting or installing in addition to
existing rolls, corrugating rolls synchronised
with the existing pair of corrugating rolls
(b) in place of the heated guide rolls (c) and
pressure roll (d). These new corrugating
rolls may substitute for the heated guide and
pressure rolls or be installed in addition to
existing rolls. One or both heated guide
rolls may be used to preheat the second
fluting medium.
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ii) Providing a mill roll stand for a ~econd
fluting medium to be fed through the new
corrugating rolls (i), if an exis~ing mill
roll stand is not available.
iii) Providing an adhesive applicator to apply
adhesive to either a liner or the exposed tips
on one side of the flute to flute structure
prior to bonding with a liner.
iv) Providing a new guide roll to allow tangential
approach of the liner prior to bonding to the
flute to flute structure.
(v) Providing very similar treatment of each
medium prior to corrugating. This includes
the provision of tension control,
; 15 preheater/preconditioners, heated S wrap drive
rolls, and steam box conditioners
incorporating a new carrier roll which
operates as a take off roll and supports the
flute to flute structure holding it in a
configuration which
(a) provides an accurately registered support
during glue application, and
(b) prohibits uncontrolled movement of the
flute to flute structure during
development of the glue bond with the
liner.
This modification enables two fluting mediums to be
precisely bonded ~lute tip to flute tip maintained in that
orientation and then to be bonded to a liner as a first
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stage in preparing a flute to flute corrugated board. Where
a conventional single faced board is to be formed one
fluting medium is simply omitted and the one pair of
corrugating rolls the preferred pair being the upper pair,
(b), are not utilized. Also the first adhesive applicator
is preferably not used.
In forminy the bonded fluted mediums it is
necessary to constrain the mediums to maintain the flute
orie~ntation of each fluted layer and to maintain the
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~;31046~
orientation and symmetry of the flute tip to flute tip
bonds. This may be achieved by using a grooved carrier roll
to take up the bonded mediums and support them until the
bond is set. Alternatively a smooth carrier surface can be
used in association with vacuum to provide the necessary
constraint. Other means for constraining the mediums can
also be used such as strings or straps to maintain the flute
tips in correct orientation.
The improved strength characteristics of the double
flute construction enable lighter weight board to be made
having strengths equivalent to those found in heavier boards
of conventional structure. Thus savings in material costs
are possible using the flute to flute construction.
It has been found that boxes formed from flute to
lS flute board-exhibit superior durability and strength. The
creasing and folding characteristics of board having flute
to flute bonding are such that the corner and edge folds of
boxes provide added strength to the construction. The flute
to flute structure creases in a well defined manner to
produce a hinged joint which is superior in strength,
flexibility and visual appearance compared with creases in
conventional board.
Bonded fluted mediums according to this invention
can be subsequently bonded to any suitable liner material to
form light weight structural laminates. The mediums can be
manufactured from 100% cellulose fibre or ligno-cellulose
fibre or combinations of cellulose, ligno-cellulose and
synthetic fibres, or they may be laminated structures.
The liners or sheet elements may be of any material
and structure of varing thickness including, but not limited
to, paper board made of cellulose fibres, ligno-cellulose
fibres; cellulose, ligno-cellulose and/or synthetic fibre
mixtures; natural or synthetic polymers, wood, or metal; or
laminates made of bonded layers of any combinations of these
materials. Strips or strings nf any material may also be
fed interm;ttently, between the mediums across the flutes
and thus be bonded at the flute tip to flute tip junction.
The inclusion of such strips or strings will constrain the
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bonded mediums and prohibit expanslon of the flute tip to
flute tlp structure until one or more llners are added and
may additionally confer added strength to the board.
Bol~ding ma~ be achieved by use of adhe~ives or by other
means such as, but not limited to, soldering, brazing and
fusion welding.
Where a light weight structural panel for building
such as celling panels or for use ln furnlture i6 required
the liners can be wood veneer. In other applications such
as air~frame skin6 for aircraft, the ].iners may be metal
foil or synthetic polymers.
The modification of a single flute station
according to this invention enables in a conventional
corrugator, the elimination of the need for pressure
application to secure the bond between the liner and the
corrugated medium. The use of the heat or other means to
complete the bonding process of the first liner to
corrugated medium or mediums at the single facer is an
innovation and has the advantage of not adversely affecting
the 6trength of the board and of not adversely affecting the
appearance of the board by reduclng the normal pressure
lines.
A preferred embodiment of this invention will now
be described with reference to the drawings in which figure
1 represents a schematic view of a conventional single facer
unit; figure 2 shows a schematic view of the unit as
modified by this invention for forming a flute to flute
structure; figure 3 shows a detailed view of figure 2 and
figure 4 shows the modified unit of this invention when used
to make conventional single faced corrugated board.
A conventional single facer unit comprises mill
roll stands 4 and 5, a preheater roll 6, a single facer
station 7 and a mill roll 8 stand for fluting medium 23.
The single facer station 7 comprises the
corrugating rolls 10 and 11, adhesive applicator 12,
pressure roll 13 for pressing the liner against the
corrugated medium 23 on roll 11. The liner board 21 is fed
from stand 5 over preheater roll 6 to the heated smooth
guide rolls 14 and 15.
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q~he ~ormed singl~ faced board 2~ i8 tran~ferred to
ldler roll 16 and then to conveyor 17 which transport6 the
single faced board 24 for further processing.
In the modified unlt of thls lnvention one of the
a mill roll stands 5 is used for a second corrugating medium
22 while an other mill roll stand is used for liner 21. A
new guide roll 31 is used to guide the liner onto
preheater roll 6 and then under a new guide roll 32, to the
S wrap rolls and onto the carrier roll 36.
l~ For medium 22, a second preheater roll 42 is
inserted under preheater roll 6. A new roll guide 43 16
used to guide the medium onto the preheater roll 42 and then
under a new guide roll 44.
For medium 23, a further preheater roll 45 i~ used.
This will require a roll guide 46 and a roll guide 47 to
guide the medium into the single facer S wrap heated rolls.
Steam sprays may be mounted on preheater rolls to
precondition the sheet.
Steam boxes may be located before rolls 10 and 34
2t) to condition the mediums prior to corrugating.
An automatic spllcer may be utlllzed with each
medium coming from roll stands 5 and 9 with the liner coming
from roll stand 4.
The guide roll 14 and pressure roll 13 shown in
figure 1 are replaced by corrugating rolls 34 and 35. The
heated smooth guide roll 15 is used to preheat the
corrugating medium 22. The two corrugated mediums 22 and 23
are adhered together between rolls 35 and 11 which are
driven synchronously to ensure precise flute tip to flute
33 tip bonding. This can be achieved by installing a direct
drive, meshed gear drive or toothed belt drive between the
driven lower corrugating roll 35 and the corrugating roll
11 .
A carrier roll 36 is installed to operate as a
3~ take-off roll and to provide support and constraint for the
bonded mediums.
The carrier roll 36 may be constructed as a shell
with appropriate drilling for vacuum application to hold the
flute to flute structure in position on the carrier roll.
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1304663
Fingers or guides may also be provided to achieve ~he
positioning of the flute to flute structure on the carrier roll
and the corrugating rolls.
As an alternative, the corrugating rolls 11 and 35 can
be arranged with a vacuum facility to hold the fluted product
in the roll flutes. The area providing the vacuum on roll 35,
can be extended to hold the flute to flute structure in -the
roll flutes and present them in such a way as to ach,ieve a
correctly aligned transfer to the carrier roll 36.
The carrier roll 36 may be a plain or grooved
cylindrical surface or may also be provided with spaced bars of
metallic or non-metallic materials to carry the flute to flute
structure.
Holding of the flute to flute structure to the carrier
roll 36 may also be achieved by use of vacuum, applied from
within the carrier roll inner cavity.
A new adhesive applicator station 37 is located
adjacent to the carrier roll 36 to apply adhesive to the flute
tips on the exposed face of the flute to flute structure. The
~0 surface of the carrier roll may be arranged to provide a
positive air pressure at point 49, causing the flute to flute
structure to " ~ out" ensuring a good transfer of the
adhesive to the exposed tips of the structure. The roll 38
guides the liner 21 to join with the flute to flute structure
to form one particular example of the structures which are the
subject of the invention disclosed in Canadian Patent
Application No. 517,430.
The top liner 21 is assisted in bonding to the flute to
flute structure after the glue application by an input of
energy in the~form of radiant or convected heat, microwave or
other energy by the units 39.
Allicomponents may be pre-heated, moistened or pre-
treated to accelerate bonding of the component to component
interfaces.
The carrier roll, assisted by positive air pressure
from the blow box 40 inside the carrier roll 36, or vacuum from
the liner side, will discharge the combined liner and
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flute to flute structure 25 to ~ransport ~ection 41
preceding the next processing st~tion.
The trAnsport section 41 may be straight or curved
in shape, and i~ curved, the curve will be arranged to
S utilise tension forces in the liner to apply gentle pressure
to the glue bond. A change in radius will achieve further
beneficial bond development.
The transport section ~1 may be provided with a
driven carrier belt or belts to transfer the combined liner
and flute to flute structure to the next section or next
processing unit.
The carrier roll 36 is driven by a separate
synchronised drive, a meshed gear drive or a toothed belt
drive from the lower corrugating roll 35 or primary driven
roll 11 to ensure it is synchronised with the corrugating
roll 35. Precision, of flute tip to flute tip bonding and
in the control of transfer from corrugating roll 35 to the
carrier roll 36 and in the positional restraint of the flute
to flute structure prior to the addition of liner 21 form
key elements of this invention.
As shown in figure 4 the modified unit of this
invention can also be used to make an improved form of
conventional single faced corrugated board.
An improved single-faced corrugated board may be
produced by ceasing to feed the corrugating medium 23 to the
corrugating rolls 10 and 11 and also ceasing to apply glue
to glue station 12 while continuing application at glue
station 37 to corrugated medium 22. In this case the glue
station 37 is moved towards the carrier roll 36 to contact
the thinner conventional corrugated sheet and the carrier
roll 36 is rotated through one half flute pitch to bring
corrugated medium 22 into mesh with carrier roll 36, after
leaving corrugating roll 35.
From the above it can be seen that the production
of board structures with flute tip to flute tip bonding can
be achieved with modification of existing machinery or
construction of new machinery.
Also from the above it can be seen that the
production of conventional board structures with improved
appearance can be achieved.
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