Dandy pan construction for reduced surface cracking

Details Dandy pan construction for reduced surface cracking Dandy pan construction for reduced surface cracking

2000-03-07

2001-08-21

Hastings, Karen M. (Department: 1731)

Paper making and fiber liberation

Apparatus

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

C162S357000, C162SDIG007

Reexamination Certificate

active

06277245

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to dandy rolls for paper making machines, and more particularly, to a construction of a dandy pan to reduce surface cracking.
BACKGROUND OF THE INVENTION
A dandy roll is used in the manufacturing of paper. The purpose of the dandy roll is to smooth the paper and apply a finish to the paper as the paper moves under the dandy roll. The dandy roll eliminates bubbles, foam, and major inequalities in formation, compacts the fibers, and may mark the paper with a watermark pattern. In large paper making machines, the dandy roll is of considerable weight.
FIGS. 1 and 2
illustrate a dandy roll disclosed in U.S. Pat. No. 2,947,356. A dandy roll
10
includes an end plate
12
having an outwardly extending annular flange
14
. At the opposite end of dandy roll
10
is an end plate
17
from which extends an integrally formed, elongated, hollow journal
18
. Extending between end plate
12
and
17
is a framework (not shown) supporting a screen
20
which forms the surface of dandy roll
10
and may bear patterns for watermarking. A pair of rollers
26
are mounted on spaced brackets
22
by means of pins
24
. An annular shoe
16
on dandy roll
10
is in rolling engagement with rollers
26
. A bearing
28
supports hollow journal
18
. Means for driving dandy roll
10
may be affixed to the outer end of journal
18
, for example, a pulley, gear, or sprocket.
FIG. 1
shows a sprocket
30
having a plurality of circumferential grooves
31
for reception of a plurality of driving V-belts (not shown). Flange
14
defines an opening in end plate
12
through which extends one of a support bar
32
. Support bar
32
supports a water tray
40
, also referred to as a dandy pan
40
. Dandy pan
40
is fixed while dandy roll
10
is rotated thereabout. A spray pipe
42
provides liquid spray droplets to wash fibers and other paper debris from screen
20
, through the openings in screen
20
, and into dandy pan
40
. The removal of the paper debris improves paper quality. The liquid and other debris is then removed from the dandy pan.
In the manufacturing of some types of paper, for example photographic paper, defects in the paper may adversely affect the use of the paper. Defects, such as damage to the paper finish, can occur should the liquid spray droplets be allowed to fall onto the paper. Further, moisture droplets which form on the dandy pan may also damage the paper finish should they fall onto the paper. Steam, circulated within the dandy pan, can be employed to provide a source of heat. The steam causes the dandy pan to dissipate sufficient heat energy to promote the evaporation of the moisture droplets and liquid spray droplets. The evaporation of the moisture droplets and liquid spray droplets reduces possible damage to the paper finish.
The steam circulated within dandy pan
40
can be extremely hot, for example, 225 degrees F. and 12 psi. When the liquid spray droplets fall onto dandy pan
40
, cracks can occur on the surface of the dandy pan causing steam to escape. The escaping steam condenses on the paper surface, thereby adversely affecting the paper by contributing to a poor surface finish of the paper. Repairing and/or replacing the dandy pan eliminates the problem, but is expensive and reduces production. Cracks on the surface of the dandy pan have been a persistent problem. Applicant's have noticed cracks in the surface of a dandy pan within 6 to 12 months of operation.
Accordingly, a need continues to exist for a dandy pan suitable for a manufacturing environment. The dandy pan must be of a construction whereby cracks are not susceptible to forming on the surface of the dandy pan.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a robust dandy pan suitable for a manufacturing environment.
A further object of the present invention is to provide a dandy pan having a construction which is not susceptible to cracking on the surface.
Still another object of the invention is to provide a dandy pan which does not require frequent repair or replacement.
These objects are given only by way of illustrative example. Thus, other desirable objectives and advantages inherently achieved by the disclosed invention may occur or become apparent to those skilled in the art. The invention is defined by the appended claims.
According to one aspect of the invention, there is provided a dandy pan for use with a dandy roll in the manufacturing of paper material. The dandy pan includes a base portion and a top portion attached to the base portion to define an enclosed area through which steam is circulated to heat the dandy pan. A plurality of ribs are disposed within the enclosed area. Each of the plurality of ribs is welded to the base portion and secured to the top portion by at least one weld. The spacing of the ribs is equal to or less than approximately nine inches. In a preferred embodiment, the ribs are spaced approximately eight inches apart.
The present invention provides a dandy pan which is robust and suited for a manufacturing environment. The present invention's dandy pan has a construction which is not susceptible to cracking, thereby reducing the need to repair or replacement the dandy pan.


REFERENCES:
patent: 2947356 (1960-08-01), Hornbostel
patent: 5076894 (1991-12-01), Simmons et al.
patent: 5338408 (1994-08-01), Marx, Jr.

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