Note: Descriptions are shown in the official language in which they were submitted.
795
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TWIN WIRE WEB FORMER ~(ADAPTION)
This invention is directed to a web forming
machine such as a paper machine, and in particular to a
twin wire machine or providing two sided web formationO
Significant advances in web formation have
taken place over the past three decades, with the advent
of twin wire forming, wherein a web is formed between a
pair of wires so as to provide two sided formation.
Historically, from the earlier work at St. Anne's Boaxd
10 Mill by R.J. Thomas and others, as evidenced in Canadian
Patent No. 583,482 - September 15, 1959 which comprised in
essence a second wire run superimposed on a fourdrinier
machine, the twin wire arrangements progressed to special
purpose machines such as that of David Webster, and of
15 R.M.A.T. de Montigny (U.S. Patent No. 2,995,186), and the
later Papriformer (T.M.) machine of de Montigny et al
Canadian Patent No. 731,383, April 5, 1966.
Another twin wire machine embodying certain
characteristics was the "centrifugal dewatering" twin
20 wire concept of C.A. Lee (U.S. Patent No. 3,150,037 -
September 22, 1964). These special purpose machines
diverged from the planar aspect of the old fourdrinier
machines to a convoluted wrap arrangement.
Considering the characteristics of twin wire
25 machines, as compared with web forming on a fourdrinier,
the length of the formation zone is significantly
shortenedf the strength and characteristics of the product
are enhanced by two sided formation, and machine speed
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GOK 101-201
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can be significantly increased with consequent
enhancement of productivity.
The gains afforded by adoption of the special
purpose formers are offset by high costs, and loss of
production time while a mill is converted from
conventional fourdrinier operation.
The present invention provides an alternative
solution which permits the upgrading of an existing
fourdrinier machine to twin wire forming while
minimizing both conversion CQStS and production time
losses during changeover; and makes the provision for a
modular unit for integration with the existing machine
elements, to facilitate easy, rapid erection while
permitting upgrading of the facility. This imparts the
inherent advantages of twin wire formation generally and
particularly through a potential increase in speed of
operation together with the provision of an improved,
"two sided" product.
It will be further understood that the position
of the module, in its relation downstream, relative to
the breast roll, is not a fixed factor, but would be
determined in accordance with relevant factors such as
machine speed and stock feed. Furthermore, because o:E
the modular nature of the module, and the manner of its
mounting by intermediate stools upon the structure of
the original fourdrinier, it is possible to comparatively
readily relocate the module along the fourdrinier, in
order to modify its action relative to the other elements
corporating therewith.
The terms "wire" and "band", encompass
fourdrinier wires, "wires" o synthetic fabrics, and
felts of various types on which a web can be formed.
The present invention thus provides in a paper
machine for forming a web on a first moving endless band,
having a source for depositing stock on the band the
improvement comprising a second endless band, a forming
GOK 101-201
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roll to receive the first and second bands in wrappiny
relation about a portion of the periphery of the forming
roll, a second roll spaced from the first roll to receive
the first and second bands in reversed wrapping relation
about the second roll, and at least one guide roll located
within the loop of the second band to guide the bands in
a predetermined direction prior to separation of the band
from the web and the other band.
In co-ordinating the modular unit containing
the ~orming roll, the second rolII guide rolls, the
second wire etc. with the existing fourdrinier structure,
suitable provision is made for wire support means, such
as foils, located beneath the main fourdrinier or first
~ire in the convergence zone and defining, in combination
with the second wi.re, the throat into which the stock
layer travels, whereby the geometry of the throat is
dynamically stabilized in conjunction with the breast
roll by means of which the second wire is guided to the
throat, i.n relation to the amount of the stock material
present therein at any gi~en time. Again, at the point
of divergence of the two wires, the provision of suction
boxes beneath the first wire provides separation of the
formed web from the offgoing second wire, which follows
a return path.
In carrying out the invention there is provided
a method of modifying a fourdrinier machine, including
the steps of locating a forming roll to carry a second
wire in converging relation with the wire of the
fourdrinier, passing the fourdrinier wire and the second
wire in wrapping relation about a portion of the
periphery of the forming roll, providing a second
dewatering roll downstream of the forming roll, passing
the two wires in wrapping relation about a portion of the
periphery of the second roll, and separating the two
wires while retaining the formed web on the fourdrinier
wire. The method includes the further steps of
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supporting the fourdrinier wire and the second wire at the
zone of convergence, and dewateri~g the wires.
Certain embo~iments of the invention are described,
reference being made to the accompanying drawings wherein
Figure 1 represents a schematic cross-sectional elevation
of a first embodiment of the paper machine, and Figure 2
is a similar drawing of a second embodiment, each embodi-
ment incorporating its respective twin wire module in
accordance with the present invention.
The drawings are not intended to represent
scale of the components nor of their relative positions
in terms of downstream location.
Referring to Figure 1, the arrangement 10
comprises a fourdrinier section 12 having a module 14
in superposed co-operating relation thereover. A headbox
16 provides a stock supply under desired conditions of
directionl velocity and volume to the for~ard reach 18
of the fourdrinier wire 20.
The module 14 has a forming roll 24, a second
roll 26 spaced therefrom, guide rolls 28 and a breast
roll 29 over which the second wire 30 is trained.
The zone of convergence 32, between wire 20 and
wire 30 forms a throat, bounded beneath ~he wire 20 by
a suction box 34 having foil portions thereon in wire
supporting relation.
The lower wire 20 and upper wire 30 are trained
for two sided stock dewatering around the open surface forming
roll 24, which may be a vacuum forming roll, as is well
known in the art, or a grooved roll with, or without a
mesh sleeve thereover.
The wires 20, 30 are reverse wrapped about roll
26, so that the top wire 30 of the module is outermost.
Guide rolls 28 align the off-going wires 20, 30, as they
leave the second roll 26, with the couch roll 38 of the
fourdrinier. A series of suction boxes 40 are provided
beneath the wire 20, underlying the point of divergence
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of wire 30 which commences the return path of wire 30~
whereby the web is held in contact with the bot~om wire
20, for passage to the couch roll 3~.
Referring to Figure 2, -the arrangement 110
comprises a fourdrinier section 112 having a module 11~ in
superimposed co-operating relation thereover. A headbox
116 supplies stock material under controlled volume-
direction-velocity conditions ~o the forward reach 118
of the fourdrinier wire 120. This forward reach 118 is
repositioned upwardly by repositioning the breast roll.
The module 114 provides the second dewatering
roll 126, guide rolls 128 and a breast roll 129, over
which the second wire 130 is trained.
The zone of converyence 132, between wires
120 and 130 forms a throat, bounded beneath by the wire
120 and having foils thereunder, in wire supporting
relation or the segments of a suction box 134.
The lower wire 120 and the upper wire 130 are
trained around an upper portion of the periphery of the
forming roll 124 in downward wrapping relation and
formin~ the apex of the throat region thereon. The wires
120, and 130 are subsequently reverse wrapped around a
lower portion of the periphery of the second roll 126,
such that the resulting wire path is substantially
serpentine in profile view, having wire 120 outermost.
Guide rolls 128 align the off-going wires 120,
130, as they leave the second roll 126, with the couch
roll 138 o~ the fourdrinier and the plane described by
roll and the appropriate surfaces of the suction or flat
boxes 40~ these boxes being deployed in wire supporting
relation under wire 120. A series of suction boxes 140
specifically deployed beneath wire 120, and underlying
the point of divergence of wires 120 and 130, further
function to hold the web in contact wi~h bottom wire 120
for delivery to the couch roll 138.
Refering now to both drawings, by their
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GOK 101 201
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appropriate ~eference numerals, the illustrated extent
of the modules 14, 114, is not intended to be proportionate
to its size, relative to the fourdrinier section 12,
112, and in all probability there is a significant run of
the wire 20, 120, downstream from the return run of wire
30, 130.
In operation, the stock deposited on the lower
wire 20, 120, commences downward drainage and felting
onto the wire 20, 120, before entry into the throat 32,
132. In the throat 32, 132, the top wire 30, 130,
contacts the stock layer and commences formation against
the top wire 30, 130. Passage of the wires in mutual
reacting and compressive relation with the stock about
the forming roll 24, 124, produces dewatering through
both wires under pressure generated by the tension force
of the outermost wire 20, 130, which is reapplied as
the wires reverse about roll 26, 126, wi-th the wire 30,
120 to the outside. Various save-alls 39, 139, are
provided within the loop of the wire 30, 130, to receive
water expressed through the wire 30, 130. Water passing
- through the upper reach of the lower wire 20, 120, is
deflected downwardly into a saveall within the wire loop.
The presently disclosed modular arrangement 1~,
114, may be erected as a unit and moved into position
astraddle the fourdrinier section 12, 112. There then
remains the need to restring a new, lower fouxdrinier
wire and to modify or install the disclosed suction
boxes 34, 40, 134, 140. Such a changeover is normally
effected with an up-rating of the headbox and the drive
of the machine, with modLfication to the drier section to
match the increased capacity of the machine, due to the
higher speed. In the event that production quantity up
rating is not required, it is generally possible to
retain the original drive, substantially unmodified, as
the longer wire of the modified forming section passes
over significantly fewer suction boxes, flat boxes,
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GOK 101-201
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foils or the like, With consequent reduction in wire drag,
and enhanced wire li$e. The second wire is normally
driven by contact with the longer wire.
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