Roller apparatus

A roller apparatus (23) for use in the drying section of an apparatus for producing corrugated board comprises a tubular body operative to be received over a metal roller. The wall of the tubular body comprises an inner layer (24) of relatively hard polyurethane and an outer layer (25) of a deformable polyurethane. A spiral winding of yarn (26) is wrapped around the inner layer (24).

The present invention relates to a roller apparatus for use in the drying 
section of apparatus for producing corrugated board. 
Probably the most common form of corrugated board is double faced board 
which comprises a single layer of fluting medium with a single sheet of 
liner provided on the upper and lower faces thereof. Other types of 
corrugated board are well known in the art, examples of which include 
single faced board, double walled board and triple walled board. 
Much of the machinery for making corrugated board operates on a "continuous 
run" principle to optimise space and to ensure uniformity of the finished 
product whilst minimising wastage. 
The process for producing double faced board begins with the fluting medium 
being plasticised by a combination of a heated roller and steam showers. 
It then passes between a pair of rollers featuring the flute profile, the 
corrugations are formed and adhesive is applied to the flute tips. At the 
same time the first liner sheet, normally the inner--is drawn from a roll, 
passed through a series of heated rollers and is laminated to the fluting 
by a single facer unit. The resultant continuous stream of single faced 
paper is conveyed up into and over a bridge en route to the double backer 
unit. At the double backer, adhesive is applied to the exposed flute tips 
and a second web of pre-heated liner is brought into contact with the 
fluting as the two materials pass between a heated table and a "blanket" 
belt conveyor. Here, pressure and heat are applied to speed the bonding of 
the two elements. The adhesive applied to the flute tips is generally 
water-based. Steam is generated when the heat is applied. The steam 
ultimately corrodes the metal rollers. 
The board then passes to a drying section. At the drying section the board 
passes over a series of hot plates. The board is urged into contact with 
the hot plates via an endless belt. Metal weight rollers are located on 
the surface of the belt which is remote from the board for urging the belt 
towards the board. Flute crushing can occur at the drying section as each 
of the weight rollers transmits a high point load to the flute. 
The belts at the dryer section are generally not produced in endless form, 
but as a length of material with co-operating clips or other materials 
provided at the ends thereof. These clips are used to join the two ends of 
the belt together so as to provide an endless structure. If exposed, a 
metallic seam can result in noisy roll bounce as it passes under the metal 
rollers. 
The present invention has been made from a consideration of these problems. 
According to a first aspect of the present invention there is provided a 
roller apparatus for use in the drying section of apparatus for producing 
corrugated board, said roller apparatus comprising a tubular body, the 
tubular body comprising a cylindrical wall defining an aperture extending 
therethrough, the aperture being operative to receive a rotatable metal 
roller, wherein the outermost region of the cylindrical wall comprises at 
least one layer of deformable material. 
According to a second aspect of the present invention there is provided the 
use of a roller apparatus in the drying section of apparatus for producing 
corrugated board, said roller apparatus comprising a tubular body, the 
tubular body comprising a cylindrical wall defining an aperture extending 
axially therethrough, the aperture being operative to receive a rotatable 
metal roller, wherein the outermost region of the cylindrical wall 
comprises at least one layer of deformable material. 
According to a third aspect of the present invention there is provided a 
drying apparatus for use in the production of corrugated board said drying 
apparatus comprising at least one heater for heating the corrugated board, 
a movable belt for driving the board over the said heaters and at least 
one roller apparatus located on the side of the belt remote from the 
heaters, wherein said roller apparatus comprises a tubular body, the 
tubular body comprising a cylindrical wall defining an aperture extending 
therethrough, the aperture being operative to receive a rotatable metal 
roller, wherein the outermost region of the cylindrical wall comprises at 
least one layer of deformable material. 
The deformable material is preferably a plastics material such as 
polyurethane and/or an elastomeric material such as rubber. 
The roller apparatus of the present invention can be fitted over weight 
rollers provided in the dryer sections of existing machinery for making 
corrugated board. Such roller apparatus increase the diameter of the 
rollers without significantly increasing their weight. The larger diameter 
coupled with the compressible surface layer of the roller apparatus 
increases the impression on the belt providing a more uniform applied 
pressure than known rollers and furthermore allows the roller to better 
conform to hot plate surface irregularities. This results in better heat 
transfer to the board allowing faster operating speed and more consistent 
board quality. 
The damping effect provided by the outer surface layer also reduces bounce 
which reduces bearing wear. 
In a preferred embodiment of the invention the cylindrical wall comprises 
two layers. The inner layer is preferably relatively hard for continuous 
contact with the roller. It also provides excellent stability against the 
effects of centrifugal force. The outer surface layer is relatively soft 
to give excellent damping and increased roll contact with contoured 
surfaces. Furthermore roll bounce is eliminated so as to reduce noise 
levels. 
The inner and outer layers may suitably comprise polymers such as 
polyurethane. 
The Shore A hardness of the outer layer is preferably in the range from 25 
to 50 and more preferably from 30 to 45. The Shore A hardness of the inner 
layer is preferably in the range from 40 to 95 and more preferably from 45 
to 90. 
The thickness of the inner layer is preferably in the range from 0 to 15 
and is more preferably about 9 mm. The thickness of the outer layer is 
preferably in the range from 5 mm to 20 mm and is more preferably 
substantially 10 mm. The diameter of the roller apparatus is preferably at 
least 80 mm and is more preferably in the range from 80 mm to 110 mm. 
The roller apparatus may be made by casting or any other suitable method. A 
plurality of roller apparatus may be received on a single metal roller. 
The roller apparatus preferably further comprises a reinforcing structure. 
This may comprise a fabric or yarn which is ideally located between the 
inner and outer layers of the cylindrical wall so as to stop the inner 
layer from becoming distorted. The reinforcement ideally comprises a yarn 
which is wound in a spiral manner. The reinforcement stabilises the 
rollers against the effect of centrifugal force and minimises the effect 
of failure in the event of an outer surface tear. If the reinforcement was 
not provided the roller apparatus would blow apart if there were to be a 
severe cut on the outer surface of the apparatus.

Referring to the drawings a typical apparatus 10 for making double walled 
corrugated board comprises single facer units 11,12 and double backer unit 
13. A first fluted sheet is bonded to a flat liner sheet at the first 
single facer unit 11 so as to provide a first laminate 14. Similarly a 
second fluted sheet is bonded to a second flat liner sheet at the second 
facer unit 12 so as to provide a second laminate 15. The second laminate 
15 passes to the double backer unit 13 at which a flat liner sheet is 
bonded to the other side of the fluted sheet so as to provide a double 
faced board 16. The flute tips of the fluted side of the first laminate 14 
are then coated with adhesive by an applicator roller 17 and the first 
laminate 14 is bonded to the double faced board 16. The resultant double 
walled board then passes through a dryer unit 18. The dryer unit 18 is 
shown in more detail in FIG. 2. At the dryer unit 18 the double faced 
board 16 travels over hot plates 19. Part of an endless belt 20 is in 
contact with the side of the board 16 which is remote from the dryer units 
so as to urge the board towards the dryer units. A plurality of roller 
apparatus 21 are provided on the face of the belt which does not make 
contact with the board. The rollers comprise a metal bar 22 over each of 
which are located a number of short cylindrical sleeve units 23. About 5 
to 8 cylindrical sleeves are provided along the length of the metal bar 
22, depending on the machine width. The manufacture of short tubular 
roller units rather than a single tubular unit is considered preferable as 
damage of a single short unit will only necessitate replacement of a small 
part of the roller structure. Furthermore relatively small units are 
easier to make by the preferred method of manufacture which is casting. 
The cylindrical sleeve 23 comprises a hard polyurethane inner core 24 which 
gives stability and firm contact with the roller surface and a deformable 
polyurethane outer surface layer 25 which absorbs vibrations, reduces 
roller bounce and bearing wear. A length of yarn 26 is spirally wound 
around the inner core so as to prevent the inner core from becoming 
distorted. The diameter of the sleeve is about 9 cms. In use the outer 
polyurethane layer spreads so as to provide a flat "footprint" thus 
avoiding crushing and marking of the board. Also the use of a larger 
diameter sleeve without a significant increase in weight as would be 
associated with a larger metal roller increases the impression on the belt 
without crushing the belt. The larger spread of pressure associated with 
the spread roller effect provides more time for the heat to affect the 
starch/adhesive. 
Suitable materials for the inner and outer layer include polyurethane. The 
hardness of the layers can be selected to balance performance and 
endurance. Suitable combinations are set out below. 
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Shore A Durometer Combinations 
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Inner/Outer Inner/Outer 
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90/30 90/45 
60/30 60/45 
45/45 
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Material Specifications 
Material: Thermoset Polyurethane 
Durometer 
90 60 45 30 
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100% Modulus 1400 1100 950 800 
300% Modulus 2600 2040 1770 1485 
Bashore Rebound % 
41 33 30 28 
Compression Set 
33 26 23 20 
Method B 
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The tubular roller apparatus of the present invention is preferably made by 
casting. An example roller is manufactured in the following manner. 
A polyether prepolymer is mixed with a diamine curative to produce a 90 
Shore A product. The mixture is then poured into an open casting mold and 
cured to a "green state". The cure time should be long enough to allow the 
material to solidify yet brief enough so that sufficient isocyanate ends 
are available for future bonding. The outer cylinder is removed, and the 
casting is wiped with solvent in order to remove mold release and further 
soften the material. 
Nylon yarn (1260 denier/4 ply) is wound under tension in a spiral, 8 
threads per inch, and is set in from both sides of the casting by 
approximately 1/2 inch (12.7 mm). This procedure is performed in order to 
eliminate any chance of moisture attacking the textile spiral. 
The mold is reassembled with a larger outer cylinder and reheated. 
Polyester prepolymer is mixed with a TMP based triol curative to produce a 
30 Shore A product. The mixture is poured into a cavity between a 90A 
casting wound with cords, and an outer cylinder. The mold is then struck 
with rubber hammers in order to dislodge air bubbles trapped under the 
spiral winding of yarn. The mold is placed in an oven for 16 hours. The 
mold is subsequently removed from the oven, cooled and the casting is 
removed from the mold. The casting is then trimmed on both sides. 
It is to be understood that the above described embodiment is by way of 
illustration only. Many modifications and variations are possible.