Shoe press belt

Details Shoe press belt Shoe press belt

2000-09-27

2001-10-02

Chin, Peter (Department: 1731)

Paper making and fiber liberation

Apparatus

Running or indefinite length product forming and/or treating...

C428S182000, C162S901000

Reexamination Certificate

active

06296738

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to shoe press belts for use in paper-making machines and other like machinery, and more particularly to an improved groove configuration for such press belts.
DESCRIPTION OF THE RELATED ART
Press belts are used in various press devices, such as shoe-type presses, as used in the papermaking industry to transport a continuous sheet of paper through a press nip. Press belts used in the paper making art typically include a series of circumferential, spaced-apart grooves which provide channels to transport water away from the sheets as they are being pressed.
The efficiency at which satisfactory sheets can be pressed is limited by the ability of the press belt channels to carry water away from the sheet being pressed. Over the past several years, in attempts to increase productivity, several groove configurations have been introduced. However, none of these configurations have proved particularly successful.
One such groove configuration is disclosed in unexamined Japanese Patent Publication No. 501594/1998, in which the groove, as viewed in cross-section, includes a curved bottom and spaced diverging side walls, which have an angle of divergence between 6 and 15 degrees. Another known groove configuration is disclosed in Japanese Utility Model Publication No. 36960/1989, which comprises a flat bottom and opposite diverging side walls (see FIGS.
1
and
2
). Be that as it may, more commonly used press belts have grooves formed in a rectangular cross-section, in order to simplify machining, reduce production costs and increase productivity. There are, however, significant drawbacks associated with the use of square groove configurations in shoe press belts. For example, in a conventional shoe press belt wherein grooves are formed on the surface of the belt with a rectangular cross-section as shown in FIG.
3
(
a
), the grooves have a tendency to deform as shown in FIGS.
3
(
b
)-(
e
). More particularly, as the nip pressure increases from 500 KN/m to 1000 KN/m, 1500 KN/m and 2000 KN/m, the upper end portions of square grooves become narrower as if closing the entrance, the side walls bulge inward, and the bottom becomes convex. This deformation significantly reduces the cross-sectional area of the grooves, and consequently their capacity to drain water from the pressed sheet. It is known if the water draining function of the grooves deteriorates, so-called ‘groove-marks’ may appear on the pressed sheets.
Another problem associated with the use of square groove configurations is that sharp corners are likely to be formed under nip pressure at the juncture between the lower edge of the side walls and the bulging bottom of the grooves. These sharp corners create points of stress concentration which may lead to cracks.
Recent attempts to reduce the amount of groove deformation include the use of harder resins in manufacturing press belts. While press belts formed of harder resins are more resistant to groove deformation, they are more susceptible to crack formation and/or delamination, thus shortening the service life of the belts.
Therefore, it is the object of the present invention to provide a press belt having an improved, groove configuration which retains water drainage capacity under nip pressure, while at the same time being resistant to crack formation, thereby enabling a satisfactory service life and avoiding the formation of ‘groove-marks’ on the pressed sheet. The ideal press belt design would also be simple and hence cost effective to manufacture.
SUMMARY OF THE INVENTION
The above objects are accomplished by providing a shoe press belt formed with at least one groove on the outer surface thereof for draining water, wherein the at least one groove comprises side walls having concave inwardly facing surfaces. The grooves may be helically formed or they may include a plurality of spaced apart longitudinal grooves formed in parallel.
In one embodiment of the invention each of the grooves has a flat bottom and rounded corners smoothly joining the side walls.
In another embodiment of the invention, each of the grooves has a concave inwardly facing bottom and rounded corners smoothly joining the side walls.
Further, the present invention provides a shoe press belt, wherein the upper edges of the side walls are convexly rounded to smoothly join with the surface of the press belt.


REFERENCES:
patent: 3600779 (1971-08-01), DeNoyer
patent: 5543015 (1996-08-01), Jermo
patent: 5626723 (1997-05-01), Schiel et al.
patent: 36960 (1989-11-01), None
patent: 510594 (1998-10-01), None

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