Manufacturing container or tube from paper; or other manufacturi – Bending – Corrugating
Reexamination Certificate
2000-08-10
2004-10-05
Kim, Eugene (Department: 3721)
Manufacturing container or tube from paper; or other manufacturi
Bending
Corrugating
C493S465000, C493S427000, C493S434000, C492S036000, C492S034000
Reexamination Certificate
active
06800052
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a corrugating machine utilized in the manufacture of corrugated cardboards or paperboards and a corrugating roll design for use with the machine.
An example of a conventional “single facer” corrugating machine for making a single faced corrugated cardboard is generally shown at
100
in FIG.
5
. The single facer
100
generally comprises corrugating rolls consisting of a pair of upper and lower, counter-rotating, longitudinally toothed, corrugating rolls
110
a
and
110
b
for providing corrugations or flutes in a paper medium, or core A in a nip
160
created between the rolls
110
a
and
110
b
, a gluing section
120
for applying glue or adhesive to the tops of the flutes of the corrugated medium A as it is moved therepast, and a smooth surfaced pressure roll
130
disposed downstream of the gluing section for cooperating with the lower toothed roll
110
b
to bond the glued corrugated paper medium A and a paper liner B to each other to form a single faced corrugated cardboard product C. Each of the upper and lower corrugating rolls
110
a
and
110
b
has a tooth profile
140
defined by a plurality of tooth roots or bottom lands and a plurality of tooth tips extending longitudinally along the outer peripheral surface of the roll. Suction device
150
is disposed adjacent to the lower corrugating roll
110
b
to hold the corrugated medium A against the lower toothed roll
110
b
by suction.
In the conventional corrugating process using the single facer
100
, a paper medium web is passed into the nip
160
formed by the inter-engaging teeth of the two corrugating rolls
110
a
and
110
b
, and this web begins to be deformed as it moves into an actual corrugating impression zone P in the nip where full engagement of the teeth takes place, i.e., one of the tooth tips of the upper roll
110
a
and the corresponding one of tooth roots of the lower roll
110
b
are in registration or in impression engagement. At the corrugating impression zone P, the medium web is formed into a final corrugated configuration as shown in FIG.
6
. The corrugated medium A, after passing through the nip, is transferred to a glue applicator roll
170
of the gluing section
120
while being held by suction or vacuum against the lower corrugating roll
110
b
. Such transfer of the corrugated medium web can be accomplished by rotation of the lower corrugating roll
110
b
. The gluing section
120
picks up the glue contained in a glue reservoir
190
while rotating within the reservoir to be partially immersed in the glue therein, and applies the glue to the tops of the corrugations of the paper medium A. Doctor roll
180
is used to perform glue layer thickness control and provide for the application of a uniform glue layer to the tops of the corrugations of the medium A. The glued medium A is next passed between the lower corrugating roll
110
b
and the pressure roll
130
along with the liner B being carried around a portion of the pressure roll
130
. The pressure roll
130
presses the glued corrugated medium A and the liner B against the lower corrugating roll
110
b
to bond the materials A and B to each other and thus produce a single faced corrugated cardboard paper product C.
The conventional design of the single facer
100
has the following disadvantages when used in the manufacture of the single faced corrugated cardboards.
Firstly, in order to ensure that the paper medium can be formed with the industrial standard type flutes and to prevent spring back of the fluted paper medium after it leaves the corrugating nip, it is required to provide a significant corrugating nip pressure between the pair of the corrugating rolls
110
a
and
110
b
at the corrugating impression zone P, the amount of which pressure is determined in accordance with a given center-to-center distance of the upper and lower corrugating rolls
110
a
and
110
b
. More specifically, the medium web can be clamped by the substantial corrugating nip pressure provided between one of the tooth tips
152
of the upper corrugating roll
110
a
and one of tooth roots
151
of the lower corrugating roll
110
b
, as shown in FIG.
7
.
Paper tensile strength may depend mainly on frictional forces acting among the fibers of the paper medium and a degree of fiber entanglement. The fibers in the paper medium tend to be generally oriented in a direction perpendicular to the length of the roll as the paper medium moves through the corrugating nip. Application of substantial nip load to the medium at the corrugating nip position P may cause some of the fibers in the portion of the medium being corrugated to be cut, thereby resulting in a decrease of the degree of fiber entanglement. This may lead to a reduction strength or rupture of the corrugated paper medium and a decrease in the quality of the product.
Secondly, in order to handle a higher corrugating speed, the liner B is brought into contact with only the tops of the glued flutes of the paper medium A between the lower corrugating roll
110
b
and the pressure roll
130
. In this case, the glue cannot fully penetrate into both of the medium A and the liner B. Thus, bonding may occur at interfaces between the liner B and the tops of the flutes of the medium A in which some of the fibers therein may be cut undesirably, thus resulting in reduction of the bonding strength and also reduction of the strength of the single faced corrugated cardboard product in the form of a trussed structure composed of the combined corrugated medium A and liner B.
To overcome the second disadvantage, Japanese Laid Open Patent Applicatio. No. 8-25531 proposes a pair of upper and lower corrugating rolls for a single facer wherein the corrugating rolls, instead of each having a tooth profile composed of a single arc, each have a profile of a tooth tip portion defined by a combination of a plurality of arcs that are symmetrical with respect to its center line. The tooth tip portion of each of the corrugating roll has a gentle arc form that has no abrupt change in curvature. With this arrangement, a substantially uniform distribution of contact pressure exerted on the liner and paper medium webs can be accomplished as they are compressed between the pressure roll and the lower corrugating roll.
As can be appreciated, however, the pressure roll has a smooth cylindrical surface whereas the lower and upper corrugating rolls have their tooth profiles. Accordingly, application of the teachings of the 8-25531 application to the pair of upper and lower corrugating rolls defining the corrugating nip therebetween would not prevent the loss of the strength of the paper corrugated medium because of the cut fibers mentioned above with regard to said second disadvantage. Moreover, modification of the corrugating roll design having the tooth profile composed of a single arc into that having the tooth profile defined by the combination of the plurality of arcs mentioned above may require delicate machining operations.
Also, for overcoming the problem as described in connection with the high corrugating speed, Japanese Laid Open Patent Application No. 6-23884 discloses a single facer machine wherein a liner web can be bond to a corrugated paper medium web under a reduced contact pressure in a nip formed by lower corrugating and pressure rolls. In the single facer of the 6-23884 application, the liner contacts the glued flute tips of the corrugated medium in the pressure nip formed by the pressure roll and the lower corrugating roll, with the liner web being tensioned by means of tensioning rolls disposed upstream and downstream of the lower corrugating roll in order to reduce the substantial contact pressure which would be otherwise required at the pressure nip.
However, it is not practical to apply the teachings of the 6-23884 application to the pair of upper and lower corrugating rolls defining the corrugating nip because high corrugating nip pressure is required at the nip defined between the upper and lower corrugating rolls whereas relatively low contac
Kabushiki Kaisha Isowa
Kim Eugene
Stroock & Stroock & Lavan LLP
Tawfik Sameh H.
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