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ABSTRACT

To provide a corrugating roll for a single facer which avoids generation of press marks or fracture of paper without a loss of paper by suppressing a contact pressure between a corrugating medium and a liner paper, and which may manufacture the corrugated paper in a low cost with easiness of machining work, in a corrugating roll for a single facer, in which a pair of corrugating rolls engage with each other through a tooth form in parallel to roll axes on circumferential surface portions of the rolls, a profile of a tooth tip portion is composed, in combination, of a plurality of arcs that are symmetrical with respect to a tooth apex portion. The profile of the tooth tip portion includes the tooth apex portion and is constituted in combination by a first arc having substantially the same radius of curvature as that of an outer circle of the corrugating roll. The profile of the tooth tip portion is constituted in combination by a second arc that inscribes with the first arc at a terminal portion of the first arc. The profile of the tooth tip portion is constituted in combination by a third arc that circumscribes with the second arc at a terminal portion of the second arc.

Inventors: Hiroyuki Takenaka, Hiroaki Sasashige Takayuki Miyake
Original Assignee: Mitsubishi Jukogyo Kabushiki Kaisha

BACKGROUND OF THE INVENTION


The present invention relates to a single facer and a corrugating roll for a single facer.

An example of a conventional single facer (i.e., single faced corrugated board producing machine) is shown in FIG. 7. The single facer uses a pressure roll 3.

More specifically, a core paper 7 fed to the upper side of an upper corrugating roll 1 in a direction indicated by an arrow is delivered between a pair of an upper corrugating roll 1 and a lower corrugating roll 2. The upper corrugating roll 1 and the lower corrugating roll 2 have tooth forms in parallel with axes on circumferential portions thereof and are engaged with each other. The upper corrugating roll 1 and the lower corrugating roll 2 are rotated while the core paper 7 is fed in the engagement portion to thereby form the corrugation on the core paper 7.

The corrugated core paper 7 is transferred to a glue application roll 4 by the rotation of the lower corrugating roll 2. The glue application roll 4 performs the glue layer thickness control by a doctor roll 5, picks up glue contained within a glue container 6 and applies it to the top of the corrugation of the core paper 7.

The glue applied paper 7 is transferred to a pressure roll 3 by the rotation of the lower corrugating roll 2 and at the same time, a liner paper 8 is supplied to the pressure roll 3. The pressure roll 3 presses the liner paper 8 against the lower corrugating roll 2 and presses and adheres both papers to form a single-faced corrugated board 9.

Another example of the single facer is shown in FIG. 8. In this single facer, an endless pressure belt 10 is used instead of the pressure roll 3.

Since the pressure belt 10 simultaneously presses a plurality of teeth of the lower corrugating roll 2, it is possible to reduce a pressure between the core paper and the liner paper 8 in comparison with the pressure roll 3.

However, since the upper corrugating roll 1 and the lower corrugating roll 2 of the above-exemplified single facers have a tooth tip portion having a relatively small radius of curvature as shown in FIGS. 4 to 6, there have the following disadvantages.

More specifically, as shown in FIG. 4, the upper corrugating roll 1 and the lower corrugating roll 2 have the tooth portions in parallel to the roll axes on the roll outer circumferential portion of the radius R.sub.C of curvature. As shown in FIG. 5, their tooth profile of tooth portion is composed of three portions, i.e., a tooth tip portion, a tooth side portion and a tooth bottom portion.

The tooth tip portion includes a tooth apex portion S.sub.1 and is defined by an arc (S.sub.1 to S.sub.2) forming a part of a circle .epsilon. (indicated by a two-dotted and dash line in FIG. 5) having a relatively small radius of curvature.

The tooth side portion is defined by a straight line (S.sub.2 to S.sub.3) that is tangential with the circle .epsilon. at a terminal portion of the arc (S.sub.1 to S.sub.2) forming the tooth tip portion.

The tooth bottom portion is tangential at a terminal end portion S.sub.3 with the straight line (S.sub.2 to S.sub.3) forming the tooth side portion and is defined by a concave arc (S.sub.3 to S.sub.4) forming a part of a circle .zeta. (indicated by a two-dotted and dash line in FIG. 5) having a relatively small radius of curvature.

Thus, since the tooth tip portion of the lower corrugating roll 2 is defined by the arc (S.sub.1 to S.sub.2) having a relatively small radius of curvature, when the core paper 7 and the liner paper 8 are compressed between the lower corrugating roll 2 and the pressure roll 3 or the pressure belt 10, as shown in FIG. 6, a nip pressure W is applied between the tooth tip portion F of the lower corrugating roll 2 and the pressure roll 3 or the pressure belt 10, a pressure P having a sharp rise is applied to the paper E (i.e., the core paper 7 and the liner paper 8), and the maximum pressure is extremely increased.

If such a large local pressure is applied, not only a fracture of the paper is likely to be generated upon bonding but also a black pressure mark, called a press mark, is generated, to thereby permanent discoloring occurs even if the paper is not broken.

Accordingly, in the conventional corrugating roll, the paper fracture is very likely to occur upon bonding. Otherwise, the permanent discoloring, called a press mark, is generated to reduce a quality and a strength of the corrugated board. In addition, the conventional system has a disadvantage of generating a loss of paper to cause an economic problem. Also, a working efficiency is degraded.

Furthermore, in the above-described prior art, since the tooth tip portion has a relative small radius of curvature for the upper and lower corrugating rolls 1 and 2, it also has a disadvantage that the machining work is troublesome.

For example, upon machining the upper corrugating roll 1 and the lower corrugating roll 2, if, first of all, the roll form having a radius R.sub.C is machined and the tooth portion composed of the tooth tip portion, the tooth side portion and the tooth bottom portion in parallel to the roll axis on the roll outer circumferential portion, since the arc having the relatively small radius of curvature has to be formed as the tooth tip portion, the number of the machining steps is increased, as a result of which the manufacturing cost is increased.

SUMMARY OF THE INVENTION


In view of the above-described problems inherent in the prior art, it is an object of the invention to provide a corrugating roll for a single facer which avoids generation of press marks or fracture of paper without a loss of paper by suppressing a contact pressure between a corrugating medium and a liner paper, and it is another object of the invention to provide a corrugating roll for a single facer which may manufacture the corrugated paper in a low cost with easiness of machining work.

In order to attain these and other objects, according to the present invention, in a corrugating roll for a single facer, in which a pair of corrugating rolls engage with each other through a tooth form in parallel to roll axes on circumferential surface portions of the rolls, a profile of a tooth portion is composed, in combination, of a plurality of arcs that are symmetrical with respect to a tooth apex portion.

The profile of the tooth tip portion includes the tooth apex portion and is constituted in combination by a first arc having substantially the same radius of curvature as that of an outer circle of the corrugating roll. The profile of the tooth tip portion is constituted in combination by a second arc that inscribes with the first arc at a terminal portion of the first arc. The profile of the tooth tip portion is constituted in combination by a third arc that circumscribes with the second arc at a terminal portion of the second arc.

Also, it is preferable that a length of a chord which is a linear distance between the terminal portions of the first arc is 0.2 to 0.6 mm, more preferable, 0.35 to 0.4 mm.

According to the present invention, a pressure belt or a pressure roll is pressed against the corrugating roll, and a corrugating medium and a liner paper are fed between the corrugating roll and the pressure belt or the pressure roll to pressingly bond the corrugating medium and the liner paper together.

As described above in detail on the basis of the embodiment, according to the present invention, since the tooth tip portion of the corrugating roll is realized to have a gentle arc form that has no abrupt or steep change in the curvature, when the corrugating medium and the liner paper are compressed between pressure belt or pressure roll and the corrugating roll, the maximum contact pressure to the liner paper and the corrugating medium can be suppressed. Accordingly, it is possible to suppress the sharp rise and to make uniform the contact pressure between the pressing mechanism and the corrugating roll.

As a result, it is possible to suppress the fracture of the paper or the press mark that is the black pressure mark caused by the excessive pressure. It is therefore possible to avoid the loss of paper and to enhance the yield. It is possible to increase the strength and the quality of the corrugated board.

Also, even in the wave-shape formation by the engagement of the corrugating rolls, a smooth slippage is ensured. Therefore, the paper fracture due to the tension increment in formation may be prevented.

In addition, since the first arc of the tooth tip portion has the same radius of curvature as the radius of curvature of the outer circle of the corrugating roll, it is advantageous that the machining work is facilitated.