Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a forming apparatus for forming
a web from stock. More particularly, this invention relates
to a forming apparatus for forming a web of paper in the
forming section of a papermaking machine.
INFORMATION DI~CLOSURE STATEMENT
For many years, paper webs were formed by depositing a
jet of pulp, or stock, onto a moving fourdrinier wire. 'xcess
water within the deposited stock was drained through the
fourdrinier wire by various dewatering means including suction
boxes.
Paper webs formed as a result of the foregoing fourdriner
forming process resulted in a finished paper product exhibiting
a certain two-sidedness in that the water, during formation,
had been drained in one direction only. Such two-sidedness
presented a finished sheet having different surface charac-
teristics on each side of the sheet thereby causing printing
problems.
More recently, various twin wire formers have been pro-
posed which have enabled the dewatering of a web in both
directions simultaneously. Such twin wire formers have
greatly increased the quality of the resultant paper product
by providing a web having fairly uniform surface character
istics on both sides thereof.
However, many twin wire formers are disposed as retrofits
above an existing fourdrinier forming section. In such retro-
fitted machines, the jet from the headbox is deposited on the
moving fourdrinier wire and usually travels a considerable
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distance prior to entering -the forming section defined by the
cooperating bottom and top w.re. During the movement of the
wire prior to movement between the cooperating bottom and top
wires, the web is subjected only to bottom drainage. Such
bottom drainage has resulted in certain inherent character-
istics of the resultant paper web and these characteristics
have, to a large degree, been undesirable.
More specifically, during the movement of the web through
the free space between the headbo~ and the top wire when
forming paper for newsprint, relatively high linting has re-
sulted therefrom due to such bottom drainage. Furthermore,
certain speed limitations have been imposed by the afore-
mentioned open wire section and, to a degree, fines within the
paper stock are unevenly distributed throughout the resultant
web.
Additionally, in such twin wire formers, it is essential
that a gradual dewatering action be applied to the stock so
that the resultant web maintains therein, most of the fines
that were suspended in the stock.
These, and other problems, are overcome by the apparatus
of the present invention.
Conse~uen-tly, it is a primary objective of the present
invention to provide a forming apparatus that overcomes the
aforementioned inadequacies of the prior art machines and to
provide a forming apparatus which contributes a signiflcant
improvement to the art o-f paper formation.
Another objective of the present invention is the pro-
vision of a forming apparatus in which the stock is subiected
to a gradual increase in dewatering action between the first
and second ends of the forming section.
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Another objective of the present invention is the pro-
vision of a forming apparatus in which the jet of stock is
ejected directly into the forming section defined between a
first and a second forming wire.
Another objective of the present invention is the pro-
vision of a forming apparatus in which the jet of stock is
directed slightly towards the lower forming wire.
Another objective of the present invention is the pro-
vision of a forming apparatus including a first and second co-
operating wire with a suction shoe disposed below the first
wire and adjacent to the first end of the forming section
for dewatering the web downwardly.
Another objective of the present invention is the pro-
vision of a dewatering shoe having a large radius of curvature
such that a first portion of water is removed through the
first wire and a second portion of water is removed upwardly
through the second wire.
Another objective of the present invention is the pro-
vision of a forming apparatus including a suction slot for
removing the second portion of water.
Anoth~r objective of the present invention is the pro-
vision of a suction roll disposed below the first wire with
the roll having a radius of curvature which is less than the
radius of curvature of the suction shoe such that a third
portion of water is removed from the stock through the second
wire.
Another objective of the present invention is the pro-
vision of a forming apparatus in which the roll is a grooved
roll.
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Another objective of the present invention is the pro-
vision of a forming apparatus in which the roll is disposed
above the second wire such that the third portion of water is
removed through the first wire.
Other objects and advantages of the present invention will
be readily apparent to those skilled ;n the art by considering
the information contained in the annexed drawings and the
detailed description and as defined by the appended claims.
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SUMMARY_OF THE INVENTION
The present invention relates to a forming apparatus for
forming a web of paper from paper stock. The apparatus in-
cludes a frame means and a plurality of guide rolls rotatably
connected to the frame means. A 1~irst continuous forming wire
extends around, and is guided by, the first plurality of rolls.
The second plurality of guide rolls is rotatably connected to
the frame means and a second continuous wire extends around,
and is guided by, the second plurality of rolls. The first
and second wires cooperate together to define therebetween a
forming section in which the web is formed, the forming section
having a first and a second end. A headbox is disposed adja-
cent to the first end of the forming section such that the
stock is ejected from the headbox towards the first end of the
forming section so- that the stock moves together with, and
between, the wires and along the forming section in a direction
from the first towards the second end of the forming section.
A dewatering shoe is disposed adjacent to the first end of the
forming section for dewatering the web. The dewatering shoe
defines a curved surface which abuts against the first wire.
The curved surface has a center of curvature which is dis-
posed on the opposite side of the first wire relative to thesecond wire such that the first portion of water is removed
from the stock through the first wire and a second portion
of water is removed from the stock through the second wire
due to the centriFugal force of the stock moving along the
curved surface. A suction slot is disposed adjacent to the
second wire for collecting the second portion of water. A
roll means is disposed between the suction slot collector
means and the
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second end of the forming section. The roll means has a
radius of curvature ~Yhich is less than the radius of curva-
ture of the dewatering means so that a third portion of water
is removed from the stock as the stock passes around the roll
means such that the dewatering of the stock from the first
toward the second end of the forming section gradually in-
creases so that the removal of fines from the stock is mini-
mized and two-sidedness of the resultant web is inhibited.
More specifically, in a first embodiment of the present
invention, the roll means is a suction roll whereas in a
second embodiment of the present invention, the roll means
is a polymeric-covered, grooved roll.
In another embodiment of the present invention, instead
of the roll means being disposed beneath the first wire, the
roll means is disposed above the second wire such that as the
second wire passes around the roll means, the third portion
of water is removed from the stock through the first wire.
The detailed description of the present invention as
disclosed hereinafter describes the various embodiments of
the present invention. However, the present invention envis-
ages many variations and alternative arrangements that fall
within the spirit and scope of the present invention as de-
fined by the annexed claims. These variations and modifica-
tions will be readily apparent to those skilled in the art
from a consideration of the drawings and disclosure of the
present application. Such madifications and variations of the
basic concept of the present invention do not depart from the
spirit and scope of the present invention which is defined
by the appended claims.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational view of the forming
apparatus oF the present invention.
Figure 2 is an enlarged side elevational view of a
portion of the apparatus shown in figure 1.
Figure 3 is an enlarged side elevational view of a
further embodiment of the present invention.
Figure 4 is an enlarged side elevational view of yet
another embodiment of the present invention showing the roll
disposed above the second wire.
Similar reference characters refer to similar parts
throughout the various embodiments of the present invention.
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DETAILED DESCRIPTION
Figure 1 shows a forming apparatus generally designated 10
for forming a web W from stock contained within a headbox 12.
The apparatus lQ includes a frame means generally designated 14
and a first plurality of guide rolls, 16,17,18,19,20,21,22,23,
24,25 and 26 which are rotatably connected to the frame means
14. A first continuous forming wire 28 extends around the
guide rolls 16 to 26. A second plurality of guide rolls, 30,
31,32,33 and 34 are rotatably connected to the frame means 14.
A second continuous forming wire 36 extends around, and is
guided by, the second plurality of rolls 30 to 34. The first
and second wires 28 and 36 cooperate together to define there-
between, a forming section 38 in which the web ~l is formed.
The forming section 38 has a first and second end 4û and 42
respectively. The headbox 12 is disposed adjacent to the
first end 40 of the forming section 38 such that stock is
ejected from the headbox 12 toward the first end 40 of the
forming section 38 so that stock travels between the first and
second wires 28 and 36 and along the forming section 38.
Preferably, the headbox 12 is a hydraulic headbox which
delivers a uniform jet of stock. The headbox 12 is preferably
disposed less than 13 inches (33 centimeters~ from the first end
40 of the forming section 38. Ideally, the headbox 12 is dis-
posed 12 inches or less from the first end 4a of the forming
section 38. The jet of stock impinges onto the first wire 28
prior to the second wire 36 and, in the preferred embodiment of
the present invention, the jet is arranged to impinge onto the
first wire 28 at an angle within the range 1 to 5 degrees rela-
tive to the forming section 38 adjacent to the first end 40 of
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the forming section 38.
Figure 2 is an enlarged side view of the forming section
38 and shows a dewatering means, or suction shoe, generally
designated 44 which is disposed adjacent to the First end 40
of the forming section 38, The dewatering means 44 is disposed
adjacent to the first wire 28 with the first wire 28 and the
formed web ~ disposed between the dewatering means 44 and the
second wire 36. The dewatering means 44 defines a curved
surface 46 which has a center of curvature 46R. The surface 46
having a radius of curvature in the order of 200 inches (508
centimeters) with such center of curvature 46R being disposed
on the opposite side of the web W relative to the second wire
36. The curved surface 46 defines a plurality of drainage holes
48,49,50 and 51 such that water within the web W drains through
the first wire 28 and through the holes 48 to 51 for effecting
initial dewatering of the formed web W. Such drainage of water
from the the stock is assisted by a partial vacuum which is
connected to the dewatering means 44. Preferably a partial
vacuum of between 10 to 20 inches of water is applied to the
dewatering means 44. While a first portion of water is removed
from the stock by means of drainage and suction through the
dewatering means 44 it is evident that due to the curved surface
46 and movement of the stock between the wires 28 and 36 around
such curved surface 46, a second portion of water within the stock
will be thrown by centrifugal force upwardly through the second
wire 36 where such second portion will be removed by means of a
collector means 52 disposed adjacent to the second wire 36. The
collector means 52 is a vacuum slot which is disposed above the
dewatering means 44 between the first and second ends 40 and 42
respectively o-F the forming section 38.
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(11 )
In a first embodiment of the present invention as shown in
figure 2, a roll means 17 is a suction roll which is disposed
between the collector means 52 and the second end 42 of the
-forming section 38. The roll means 17 has a radius of curva-
ture which is less than the radius of curvature of the de-
watering means 44. The roll means 17 is disposed on the same
side of the first wire 28 as the dewatering means 44. That
is, the roll means 17 is disposed under the first wire 28 such
that when the first wire 28 moves around the roll means 17, a
third portion of water is removed from the stock through the
second wire 36 as the stock passes around the roll means 17.
By such an arrangement, the dewatering of the stock between
the first toward the second end of the forming section 38
gradually increases so that removal of fines contained within
the stock is minimized and two-sidedness of the resultant web
is inhibited.
Figure 3 shows an alternative embodiment of the present
invention in which a polymeric-covered, grooved roll 17A is
substituted for the suction roll 17 of the first embodiment.
Such grooved roll 17A results in a reduction of cost as grooved
rolls are less costly to manufacture than suction rolls. How-
ever, such substitution does not greatly reduce the efficiency
of the present forming apparatus.
In both the embodiments of figures 2 and 3, a radius top
suction box 54 is shown below the first wire and between the
collector means and the roll means for further reducing the
moisture content: o-f the formed web by removing water through
the first wire.
Figure 4 shows yet a further embodiment of the present
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invention in which the roll means 17B, which may be a grooved
roll, is disposed above the second wire 36B so that as the
second wire 36B passes around the roll means 17B the third
portion of water is removed from the stock through the first
wire 28B.
In operation of the forming apparatus as shown in figures
1 and 2, a jet of stock is directed from the headbox 12 towards
the first end 40 of the forming section 38. The stock disposed
between the first and second wires 28 and 36 respectively, moves
towards the suction shoe 44 which is disposed below the first
wire 28. The partial vacuum within the suction shoe 44 causes
a gentle dewatering of the stock disposed between the first and
second wire. However, due to the curved surface 46 of the de-
watering means, or suction shoe 44, a second portion of water
will be removed from the moving stock through the second wire
36 due to the centrifugal force of the stock moving around the
curved surface 46. Such second portion of water is removed
through the second wire 36 by means of the collector means, or
vacuum slot 52. In the embodiment shown in figures 1 and 2,
the formed web disposed between the first and second wires 28
and 36 passes around the roll means, or suction roll 17 which
is disposed below the first wire 28, The suction roll applies
a greater suction to the moving wires and stock than the
suction applied by the suction shoe 44 so that some of the
remaining water within the formed web is drawn through the
first wire 28 towards the suction roll 17. However, the suction
roll 17 has a radius of curvature which is less than the radius
of curvature of the suction shoe 44, therefore, as the stock
passes around t:he suction roll 17, some of the water within
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the stock is thrown by centrifugal force upwardly through the
second wire 36. Therefore, the third portion of water
removed from the formed web at the suction roll 17 is removed
partially through the first wire 28 and partially through the
second wire 36. In this way, dewatering of the stock from
the first towards the second end of the forming section 38
gradually increases so that the removal of fines from the
web is minimized and two-sidedness of the resultant web is
inhibited.
In operation of the embodiment shown in figure 3, the
suction roll 17 is replaced by a rubber-covered, grooved roll
17A so that the third portion of water is removed from the
formed web through both the first and second wires. More
specifically, some of the water passes through the first wire
28A into the plurality of grooves defined by the grooved roll
17A while some of the water is thrown through the second wire
36 due to the centrifugal force of the formed web passing
around the grooved roll 17A which, like the roll 17, has a
radius of curvature which is less than the radius of curvature
of the suction shoe.
Operation of the embodiment shown in figure 4 is slmilar
to the operation of the embodiment shown in figures 2 and 3,
however, figure 4 shows the roll means 17B which may be a
grooved roll similar to the grooved roll 17A of figure 3, but
with the roll means 17B disposed above the second wire 36B,
In the embodiment shown in figure 4, some of the water will be
removed from the formed web through the upper, or second, wire
36 and some of the third portion of water will be removed from
the web through the first wire 28B due to the roll means 17B
having a radius of curvature less than that of the suction
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shoe.
It should be appreciated by those skilled in the art that
in each of the embodiments shown in figures 2,3 and 4, the
gradual dewatering is effected between the first end of the
forming section towards the roll means such that removal of
fines from the formed web is minimized and two-sidedness of
the resultant web is inhibited.
As will be appreciated by those skilled in the art, the
foregoing embodiments are merely illustrative of some of the
arrangements for carrying out the invention as defined by the
appended claims. Many variations and modifications may be made
by those skilled in the art without departing from the spirit
and scope of the invention as defined by these appended claims.
