TABLE DE FORMATION SUR MACHINE A PAPIER

FORMING BOARD FOR PAPERMAKING MACHINE

Abrégé anglais

FORMING BOARD FOR PAPERMAKING MACHINE
ABSTRACT OF THE DISCLOSURE
A papermaking machine having a forming wire,
a headbox and a forming board is disclosed. The
headbox includes a lower slice having an apron
positioned substantially in alignment with and closely
adjacent the forming board such that as the forming
wire travels over the the forming board the jet of
paper stock leaving the headbox is laid onto the wire
at the board at substantially zero angle of
impingement. The forming board further includes a
lead-in blade over which the wire travels. The blade
acts to deflect fluid, normally pumped by the wire
along its path of travel, away from the underside to
the jet of paper stock prior to this jet reaching the
forming board. Advantage is found with the disclosed
papermaking machine in that it substantially
eliminates pumping of fluid to the underside of the
stock, has zero angle of impingement of the stock onto
the wire and prevents drainage at the point of
impingement which reduces the loss of fine fibres
through the wire and minimizes the disturbance of the
paper stock resulting in better paper formation and
increased operating speeds.

Revendications

- 8 -
The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows:
1. A papermaking machine comprising:
a breast roll, a forming board and a forming
wire passing around the breast roll and over the
forming board;
a headbox for producing a jet of paper
stock, the headbox including a lower slice lip having
an apron, the lower slice lip and apron projecting
beyond of the center of the breast roll in the
direction of wire travel; and,
the forming board including a lead-in blade
section and a rear section, the rear section being
spaced rearwardly of the apron in the direction of
paper stock travel to provide a gap between the apron
and rear section, the rear section being positioned
substantially in alignment with the apron and the
lead-in blade section being angled with respect to the
rear section to project downwardly below the
substantial alignment of the rear section and the
apron, the forming wire passing over the lead-in blade
section and changing direction of travel, as the wire
passes through the gap and over the rear section, to a
direction of travel in alignment with the rear section
such that the jet of paper stock leaving the headbox
passes across the gap and is laid onto the forming
wire at the rear section of the forming board at
substantially zero degrees angle of impingement to
thereby minimize disturbance of the paper stock and
minimize drainage as the stock leaves the headbox and
impinges the wire.
2. The papermaking machine of claim 1
wherein the lead-in blade section slopes downwardly
from the rear section at an angle between 5 to 15
degrees.

- 9 -
3. The papermaking machine of claim 2
wherein the angle is between 10 and 15 degrees.
4. The papermaking machine of claim 1
wherein the lead-in blade section slopes downwardly
from the rear section at an angle of about 15 degrees.
5. The papermaking machine of claim 1
wherein the gap between the apron and the rear section
of the forming board is about 3 inches.
6. The papermaking machine of claim 1
wherein the breast roll is positioned beneath a plane
defined by the rear section of the forming board.
7. The papermaking machine of claim 1
wherein the lead-in blade section includes and edge
portion and a front wall extending below the forming
wire rearwardly and downwardly away from the edge
whereby the front wall enhances the amount of fluid
deflected by the lead-in blade section through the
forming wire and along the front wall.
8. The papermaking machine of claim 7
wherein the front wall is spaced adjacent the breast
roll and has a curvature that follows the peripheral
surface of the breast roll.
9. A papermaking machine comprising:
a breast roll, a forming board and a forming
wire passing around the breast roll and over the
forming board at a predetermined velocity;
a headbox for producing a jet of paper
stock, the headbox including a lower slice lip having
an apron, the lower slice lip and apron projecting
beyond of the center of the breast roll in the
direction of wire travel; and,
the forming board including a lead-in blade
section and a rear section, the rear section being
spaced rearwardly of the apron in the direction of
paper stock travel to provide a gap between the apron

- 10 -
and rear section, the rear section being positioned
substantially in alignment with the apron and the
lead-in blade section being angled with respect to the
rear section to project downwardly below the
substantial alignment of the rear section and the
apron, the forming wire passing over the lead-in blade
section and changing direction of travel, as the wire
passes through the gap and over the rear section, to a
direction of travel in alignment with the rear section
such that the jet of paper stock leaving the headbox
passes travels across the gap at said predetermined
velocity and laid onto the forming wire at the rear
section of the forming board at substantially zero
acceleration relative to the velocity of the
travelling wire to thereby minimize disturbance of the
paper stock and minimize drainage as the stock leaves
the headbox and impinges the wire.
10. The papermaking machine of claim 9
wherein the lead-in blade section slopes downwardly
from the rear section at an angle between 5 to 15
degrees.
11. The papermaking machine of claim 10
wherein the angle is between 10 and 15 degrees.
12. The papermaking machine of claim 9
wherein the lead-in blade section slopes downwardly
from the rear section at an angle of about 15 degrees.
13. The papermaking machine of claim 9
wherein the gap between the apron and the rear section
of the forming board is about 3 inches.
14. The papermaking machine of claim 9
wherein the breast roll is positioned beneath a plane
defined by the rear section of the forming board.
15. The papermaking machine of claim 9
wherein the lead-in blade section includes and edge
portion and a front wall extending below the forming

- 11 -
wire rearwardly and downwardly away from the edge
whereby the front wall enhances the amount of fluid
deflected by the lead-in blade section through the
forming wire and along the front wall.
16. The papermaking machine of claim 15
wherein the front wall is spaced adjacent the breast
roll and has a curvature that follows the peripheral
surface of the breast roll.
17. A papermaking machine comprising:
a forming wire;
a headbox for producing a jet of paper
stock, the headbox including a lower slice lip having
an apron; and,
a forming board having a rear section, a
lead-in blade and a front wall, the rear section being
positioned beside the apron and spaced rearwardly of
the apron in the direction of paper stock travel to
provide a gap between the apron and rear section;
the lead-in blade being positioned beneath
the lower slice lip with the lower slice lip
overlapping the lead-in blade, and the lead-in blade
projecting forwardly and downwardly from the rear
section in the direction of wire travel to define a
passage between the lower slice and the lead-in blade
where the lower slice overlaps the lead-in blade, the
forming wire passing over the lead-in blade, along the
passage, through the gap and over the rear section of
the forming board to receive the jet of paper stock,
the front wall extending below the forming wire
rearwardly and downwardly away from the lead-in blade,
the lead in blade deflecting fluid, pumped by the
forming wire, away from the passage and the gap
through the forming wire and along the front wall
prior to the forming wire reaching the passage so as
to reduce the amount of fluid pumped by the wire along

- 12 -
the passage through the gap toward the underside of
the jet of paper stock and thereby reducing the
disturbing effect on the underside of the stock caused
by fluid passage along the passage through the gap.
18. The papermaking machine of claim 17
further including an exhaust located rearwardly of the
lead-in blade in the direction of wire travel, said
exhaust being positioned adjacent the passage and the
gap to draw away any remaining fluid left in the
forming wire prior to the forming wire passing through
the gap and reaching the underside of the jet of paper
stock.
19. The papermaking machine of claim 17
further including an exhaust located in the front wall
below the lead-in blade and the forming wire to
enhance the amount of fluid deflected by the lead-in
blade through the forming wire and along the front
wall.
20. The papermaking machine of claim 17
further including a breast roll around which the
forming wire travels, the breast roll being positioned
below the headbox, the lead-in blade and the front
wall.
21. The papermaking machine of claim 18
wherein the apron has an undersurface having a tip
projecting downwardly into the passage toward the
forming wire in advance of the gap in the direction of
wire travel.
22. The papermaking machine of claim 21
wherein the tip contacts the forming wire.
23. A papermaking machine comprising:
a forming wire;
a headbox for producing a jet of paper
stock, the headbox including a lower slice lip having
an apron; and,

- 13 -
a forming board having a rear section, a
lead-in blade and a front wall;
the rear section being spaced rearwardly of
the apron in the direction of paper stock travel to
provide a gap between the apron and rear section, the
forming wire passing through the gap and over the rear
section of the forming board to receive the jet of
paper stock; and
the lead-in blade being spaced rearwardly of
the apron and projecting forwardly and downwardly from
the rear section in the direction of wire travel and,
the front wall extending below the forming wire
rearwardly and downwardly away from the lead-in blade,
the lead-in blade deflecting fluid, pumped by the
forming wire, away from the gap through the forming
wire and along the front wall prior to the forming
wire reaching the gap, an exhaust being located in the
front wall below the lead-in blade and the forming
wire to enhance the amount of fluid deflected by the
lead-in blade through the forming wire and along the
front wall and to reduce the amount of fluid pumped by
the forming wire through the gap toward the underside
of the jet of paper stock and thereby reducing the
disturbing effect on the underside of the jet caused
by fluid passing through the gap.
24. The papermaking machine of claim 23
wherein the apron has an undersurface having a tip
projecting downwardly toward the forming wire in
advance of the gap in the direction of wire travel.
25. The papermaking machine of claim 24
wherein the tip contacts the forming wire.
26. The papermaking machine of claim 17
wherein the front wall is spaced adjacent the breast
roll and has a curvature that follows the peripheral
surface of the breast roll.

- 14 -
27. The papermaking machine of claim 23
wherein the front wall is spaced adjacent the breast
roll and has a curvature that follows the peripheral
surface of the breast roll.
28. A papermaking machine comprising:
a breast roll, a forming board and a forming
wire passing around the breast roll and over the
forming board;
a headbox for producing a jet of paper
stock, the headbox including a lower slice lip having
an apron, the lower slice lip and apron projecting
beyond of the center of the breast roll in the
direction of wire travel; and,
the forming board having a rear section, a
lead-in blade and a front wall;
the rear section being spaced rearwardly of
the apron in the direction of paper travel to define a
gap therewith through which the forming wire passes as
the wire travels over the forming board to receive the
jet of paper stock; and,
the lead-in blade being positioned above the
front wall forwardly and downwardly from the rear
section, the front wall extending rearwardly and
downwardly from the lead-in blade, the lead-in blade
deflecting fluid pumped by the forming wire through
the forming wire and along the front wall reducing the
amount of fluid pumped toward the underside of the jet
of paper stock and thereby reducing the disturbing
effect this fluid has on the underside of the jet.

Description

9~
FORMING BOARD FOR PAPERMAKING MACHINE
FIELD OF THE INVENTION
The present invention relates to a
papermaking machine of the Fourdrinier type. In
particular, it relates to the headbox lower slice lip
and the forming board.
BACKGROUND OF THE INVENTION
Fourdrinier papermaking machines currently
in use employ a headbox having upper and lower slices
that control the jet of stock leaving the headbox.
The stock passes over an apron of the lower slice and
impinges a forming wire. The forming wire carries
- the stock through various nips in the forming section
so as to dewater the stock and thereby form the paper
from the stock. The forming wire in the vicinity of
the headbox passes around a breast roll located
beneath the headbox and over a forming board. The
forming board is positioned in spaced apart relation
offset from the apron of the lower slice lip so that
after the stock leaves the apron its projectory is
such that the jet impinges the wire at a
predetermined angle of impingement. In current
papermaking-machines this angle of impingement is
about 5 degrees. The forming wire is known to
provide windage as it travels about the breast roll
and is known to have fluids entrained in the wire. A
fluid shower of water and air passes beneath the
~k

~9~
-- 2
underside to the lower slice of the headbox ensuring
that there is no build up of paper fibre from the
returning wire which could be introduced to the
underside of the jet of stock.
There are basically two disadvantages
associated with the above described papermaking
machine. First the angle of impingement that the
stock meets the forming wire tends to produce
instabilities and back flow which creates
disturbances in the fibres of the stock and results
in drainage at the point of impingement causing loss
of fine fibres through the wire. Secondly, the
pumping action of the wire tends to follow the path
of travel of the wire introducing a fluid shower to
the underside of the stock which creates further
disturbances to the fibres in the underside of the
stock.
With respect to the pumping action of the
wire, this problem has been recognized previously in
Canadian Patent No. 670,293 which issued
September 10, 1963 to Joseph Baxter, Jr. The primary
object of this patent is to overcome the difficulties
associated with windage from the wire tending to
disrupt uniform deposit of stock on the wire. Baxter
teaches eliminating the windage problem by
introducing a steam chamber between the lower slice
lip and the breast roll. The steam chamber produces
steam that strips the wire of all windage as the wire
passes through the chamber. Baxter further teaches
that the condensing of the steam will necessarily
produce a corresponding increase in the temperature
of the stock resulting in the steam being absorbed.
Applicant is not aware of such a steam chamber being
used in Fourdrinier type paper machines. The problem
with this solution is that the steam under pressure
~hits the underside of the paper stock destabilizing

the stock. Further, the heat generated by the steam
chamber heats up the underside of the headbox
introducing uncontrollable creep to the lower slice
which disturbs the stock jet. Also, the headbox is
designed to maintain the temperature of the stock
within a predetermined range which will be effected
by the heating of the lower slice.
SUMMARY OF THE PRESENT INVENI'ION
It is therefore an object of the present
invention to provide a papermaking machine that
substantially eliminates the introduction of fluids
to the underside of the paper stock as it is
deposited onto the forming wire.
It is a further object of the present
invention to minimize disturbances and drainage which
occur as the paper stock is deposited on the forming
wire.
In accordance with one aspect of the
present invention there is provided a papermaking
machine comprising a forming wire, and a headbox for
producing a jet of paper stock. The headbox includes
a lower slice having an apron. The paper machine
further includes a forming board having a rear
section spaced rearwardly of the apron in the
direction of paper stock travel to difine a gap
therewith through which the forming wire passes as
the wire travels over the forming board. The rear
section is positioned substantially in alignment with
the apron so that the jet of paper stock leaving the
headbox is laid onto the forming wire at the rear
section of the forming board at substantially zero
- degrees angle of impingement to thereby minimize
disturbance of the paper stock and minimize drainage
as the stock leaves the headbox and impinges the
wire. Clearly, advantage is found by the forming
board and apron being positioned in ali~gnment to

~%~
provide an angle of impingement of substantially zero
degrees sin~e this lays the stock onto the ~,Jire with
minimal disturbance substantially eliminating
drainage. In effect, the headbox and the forming
board of the paper machine appear to the stock as
being almost continuous.
In accordance with another aspect of the
present invention there is provided a papermaking
machine comprising a forming wire and a headbox for
producing a jet of paper stock. The headbox includes
a lower slice having an apron. The machine further
includes a forming board having a rear section, a
lead-in blade and a front wall. The rear section is
spaced rearwardly of the apron in the direction of
paper travel to define a gap therewith through which
the forming wire passes as the wire travels over the
forming board to receive the jet of paper stock. The
lead-in blade is positioned above the front wall
portion forwardly and downwardly from the forming
section. The front wall extends rearwardly and
downwardly from the lead-in blade. The lead in blade
deflects fluid pumped by the forming wire through the
forming wire and along the front wall reducing the
amount of fluid pumped toward the underside of the
jet of paper stock and thereby reducing the
disturbing effect this fluid has on the underside of
the jet. As a result, any disturbances effecting the
underside of the jet of paper stock as it impinges
the forming wire are minimized.
To enhance fluid reduction to the underside
of the jet of paper stock it is envisaged that the
paper machine further includes an exhaust located
rearwardly of the lead-in blade below the gap and
adjacent the forming section to draw away any fluid
remaining with the forming wire through the forming
wire before the forming wire reaches the underside of

the jet of paper stock. Alternately, the paper
machine may further include an exhaust located in the
front wall to enhance the amount of fluid deflected
along the front wall.
It is also envisaged that the apron may
have a tip projecting downwardly from its
undersurface toward the forming wire adjacent the
gap. This tip may contact the forming wire.
In one embodiment of the present invention
the lead-in blade projects beneath the lower slice of
the headbox. In another embodiment of the present
invention the lead-in blade is spaced rearwardly of
the apron.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the nature
and objects of the present invention, reference may
be had to the accompanying diagrammatic drawings in
which:
Figures 1 to 4 are schematic views of four
preferred embodiments of the papermaking machine of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1 there is shown a
portion of a papermaking machine generally at 10.
The papermaking machine 10 includes a headbox 12
having an upper slice 14 and a lower slice 16. The
lower slice 16 includes an apron 18. The apron 18
has a tip 20 that projects downwardly from its
underside.
The papermaking machine further includes a
breast roll 22 about which a forming wire 24
travels. The last section of the papermaking machine
illustrated in this figure is the forming board 26.
The forming board 26 includes a rear section 28
including foil 29 positioned in alignment with and
spaced ~rom the apron 18. The forming board 26 has a

~8~
-- 6 --
lead-in blade shown generally at 30 as a foil. In this
embodiment, the lead-in blade 30 projects beneath the
lower slice 16 of the headbox 12 so that the lower slice
16 overlaps lead-in blade 30 and defines a passage 41
therebetween through which the forming wire 24 passes. As
shown in the Figure, the wire 24 passes over the lead-in
blade 30 and the front tip of foil 29 at an angle A which
is about ten degrees and can lie in the range of 5 to 15
degrees. The lead-in blade is positioned above a front
wall portion 34 of forming board 26 with the top end of
wall 34 sloping downwardly from and co-extensively with
the lead-in blade. An exhaust is shown at 36 behind the
lead-in blade 30 in the direction of wire travel. The
exhaust may comprise a fan applying suction to the wire 24
as it passes over exhaust 36.
In operation, headbox 12 delivers a jet of paper
stock 36 between its upper and lower slices 14 and 16. As
the stock leaves the slices, it passes over apron 18,
across gap 40 and impinges on the forming wire 24 at the
rear section 28 of the forming board 26. It should be
understood that the distance across gap 40 between the
edge of apron 18 and the forming board 26 is relatively
small and in the preferred embodiment is about 3 inches.
Because the apron 18 and the rear section 28 of the
forming board are in alignment, the angle of impingement
is zero degrees. As a result, the stock is delivered from
the headbox ~o the forming board with minimal disturbance
and no drainage at the point of impingement.
The forming wire travels around breast roll
22 pumping fluid shown generally at 42 in the
direction of arrow 44. The tip of the lead-in blade
30 deflects much of the fluid through the wire and
along front wall 34. This is shown by arrow 46 and
fluid 48. Any fluid continuing to travel with the
wire 24 is deflected by tip 20 on the underside
. .

of the apron and is drawn into the exhaust 36. This
is shown as flui~ 50. It should be understood that
the back pressure created by exhaust 36 should be
sufficient to draw the fluid into the exhaust r"ithout
disturbing the underside of the jet of paper
stock 38. By deflecting the fluid away from the
underside of the paper stock the present invention
eliminates disturbances caused to the underside of
the paper stock by the fluid pumping action of the
wire.
Referring to Figure 2 there is shown
another preferred embodiment of the present invention
wherein the lead-in blade 30 does not project beneath
the lower slice 16 of the headbox 12 but is instead
positioned rearwardly of the apron 18 in the
direction of wire travel. In this embodiment the
exhaust 36 is located in the front wall 34 to
enchance fluid deflection through the wire 24 and
along front wall 34.
Figure 3 is directed to the same embodiment
as Figure l; however the apron 18 in this embodiment
does not include the depending tip 20. This
embodiment shows a further breast roll 52 around
which a second forming wire 54 travels. The second
forming wire 54 meets the stock is provided adjacent
forming section 56.
Figure 4 is directed to the same embodiment
as Figure 2; however the apron 18 in this embodiment
does not include the depending tip 20. This
embodiment shows a forming roll 58. A nip 60 is
provided between the roll 58 and wires 24 and 54 just
prior tG the forming section 56.

Dessin représentatif