U.S. patent application number 10/850558 was filed with the patent office on 2005-07-28 for papermaking apparatus.
Invention is credited to Amos, John, Salmon, Antony.
Application Number | 20050161186 10/850558 |
Document ID | / |
Family ID | 9958590 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050161186 |
Kind Code |
A1 |
Amos, John ; et al. |
July 28, 2005 |
Papermaking apparatus
Abstract
The present invention relates to an assembly of forming elements
which together define in a papermaking apparatus a discontinuous
supporting surface for a papermaking suspension to permit drainage
and micro-turbulence to be accurately controlled, and to the
papermaking apparatus per se.
Inventors: |
Amos, John; (Bacup, GB)
; Salmon, Antony; (Bacup, GB) |
Correspondence
Address: |
NAWROCKI, ROONEY & SIVERTSON
SUITE 401, BROADWAY PLACE EAST
3433 BROADWAY STREET NORTHEAST
MINNEAPOLIS
MN
554133009
|
Family ID: |
9958590 |
Appl. No.: |
10/850558 |
Filed: |
May 20, 2004 |
Current U.S.
Class: |
162/352 ;
162/351; 162/354 |
Current CPC
Class: |
D21F 1/483 20130101 |
Class at
Publication: |
162/352 ;
162/351; 162/354 |
International
Class: |
D21F 001/00; D21F
001/58; D21G 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2003 |
GB |
0311802.3 |
Claims
1. A papermaking apparatus capable of making a sheet of paper (or
board) from a papermaking suspension, said apparatus comprising:
one or more supply means for introducing the papermaking suspension
into a wet end of the apparatus; a carrier for carrying the
papermaking suspension from the wet end to an output end of the
apparatus; and an assembly of forming elements which include: a
primary blade positioned adjacent the one or more supply means; a
first secondary support blade coupled to a leading face of the
primary blade by a first drainage deckle; and optionally n
consecutive additional secondary support blades and n consecutive
additional drainage deckles, wherein a trailing face of the first
additional secondary support blade is coupled to a leading face of
the first secondary support blade by the first additional drainage
deckle and a trailing face of the second to n.sup.th additional
secondary support blades is coupled respectively to a leading face
of the first to n-1.sup.th additional secondary support blades by
the second to n.sup.th additional drainage deckle respectively,
wherein n is an integer of one or more, whereby the upper surface
of the primary blade, the first secondary support blade, the first
drainage deckle, the n additional drainage deckles and the n
additional secondary support blades together define a discontinuous
surface for supporting the papermaking suspension.
2. A papermaking apparatus as claimed in claim 1 wherein the
discontinuous supporting surface is irregularly discontinuous.
3. A papermaking apparatus as claimed in claim 1 wherein the
discontinuous supporting surface is stepped.
4. A papermaking apparatus as claimed in claim 1 wherein the upper
surfaces of the primary blade, the first secondary support blade
and the n consecutive additional secondary support blades are
substantially coplanar at a first height and the upper surface of
at least one of the first drainage deckle and n consecutive
additional drainage deckles is at a height different from the first
height.
5. A papermaking apparatus as claimed in claim 4 wherein the upper
surfaces of the primary blade, the first secondary support blade
and the n consecutive additional secondary support blades are
substantially coplanar at a first height and the upper surface of
each of the first drainage deckle and n consecutive additional
drainage deckles is at a height different from the first height
whereby to define a discontinuous surface which is stepped.
6. A papermaking apparatus as claimed in claim 5 wherein the upper
surfaces of the first drainage deckle and n consecutive additional
drainage deckles are substantially coplanar at heights different
from each other and from the first height whereby to define a
discontinuous surface which is substantially irregularly
stepped.
7. A papermaking apparatus as claimed in claim 5 wherein the upper
surfaces of the first drainage deckle and n consecutive additional
drainage deckles are substantially coplanar at a common height
different from the first height whereby to define a discontinuous
surface which is substantially regularly stepped.
8. A papermaking apparatus as claimed in claim 1 wherein the upper
surfaces of at least one of the first drainage deckle and n
consecutive additional drainage deckles is angled.
9. A papermaking apparatus as claimed in claim 8 wherein the upper
surface is angled downwardly from trailing to leading edges of the
upper surface.
10. A papermaking apparatus as claimed in claim 1 wherein at least
one of the first drainage deckle and n consecutive additional
drainage deckles generates micro-turbulence in the papermaking
suspension by extrinsic means.
11. A papermaking apparatus as claimed in claim 1 wherein at least
one of the first drainage deckle and n additional drainage deckles
is adapted to transmit a means for generating micro-turbulence in
the papermaking suspension.
12. A papermaking apparatus as claimed in claim 1 wherein the upper
surface of at least one of the first drainage deckle and n
consecutive additional drainage deckles comprises a groove adapted
to transmit fluid onto its upper surface.
13. A papermaking apparatus as claimed in claim 12 wherein the
groove is adapted to transmit pulses of fluid onto its upper
surface.
14. A papermaking apparatus as claimed in claim 12 wherein to an
end wall of at least one of the first drainage deckle and n
consecutive additional drainage deckles extends a transverse slot
outwardly from a transverse end wall of the groove.
15. A papermaking apparatus as claimed in claim 12 wherein to a
first and second end wall of at least one of the first drainage
deckle and n consecutive additional drainage deckles extends
respectively a first and a second transverse slot outwardly from a
first and second transverse end wall of the groove
respectively.
16. A method for constructing a papermaking apparatus as defined in
any preceding claim comprising: (a) obtaining a conventional
papermaking apparatus comprising one or more conventional forming
elements in the forming area; (b) substituting at least one of the
one or more conventional forming elements with an assembly of
forming elements which include: a primary blade positioned adjacent
the one or more supply means; a first secondary support blade
coupled to a leading face of the primary blade by a first drainage
deckle; and optionally n consecutive additional secondary support
blades and n consecutive additional drainage deckles, wherein a
trailing face of the first additional secondary support blade is
coupled to a leading face of the first secondary support blade by
the first additional drainage deckle and a trailing face of the
second to n.sup.th additional secondary support blades is coupled
respectively to a leading face of the first to n-1.sup.th
additional secondary support blades by the second to n.sup.th
additional drainage deckle respectively, wherein n is an integer of
one or more, whereby the upper surface of the primary blade, the
first secondary support blade, the first drainage deckle, the n
additional drainage deckles and the n additional secondary support
blades together define a discontinuous surface for supporting the
papermaking suspension.
17. An assembly of forming elements including: a primary blade
capable of being positioned adjacent one or more supply means at
the wet end of a papermaking apparatus; a first secondary support
blade coupled to a leading face of the primary blade by a first
drainage deckle; and optionally n consecutive additional secondary
support blades and n consecutive additional drainage deckles,
wherein a trailing face of the first additional secondary support
blade is coupled to a leading face of the first secondary support
blade by the first additional drainage deckle and a trailing face
of the second to n.sup.th additional secondary support blades is
coupled respectively to a leading face of the first to n-1.sup.th
additional secondary support blades by the second to n.sup.th
additional drainage deckle respectively, wherein n is an integer of
one or more, whereby the upper surface of the primary blade, the
first secondary support blade, the first drainage deckle, the n
additional drainage deckles and the n additional secondary support
blades together define a discontinuous surface for supporting a
papermaking suspension being carried by a carrier from the wet end
to an output end of the papermaking apparatus.
Description
TECHNICAL FIELD
[0001] The present invention relates to an assembly of forming
elements which together define in a papermaking apparatus a
discontinuous supporting surface for a papermaking suspension to
permit drainage and micro-turbulence to be accurately controlled,
and to the papermaking apparatus per se.
BACKGROUND OF THE INVENTION
[0002] In the papermaking industry, various forming elements are
deployed to promote the drainage of water from paper stock in its
transformation from a papermaking suspension (or slurry) of fibres,
water and chemicals (eg fillers) into a self-supporting web of
cellulose fibres commonly referred to as a sheet (ie a sheet of
paper or board). De-watering takes place in the forming area at the
"wet end" of a papermaking apparatus, a typical one of which is
illustrated schematically by way of example in FIG. 1. Thus in FIG.
1, parallel papermaking wires 1 (or mesh or a belt) move in
direction A and are supported from beneath by discrete forming
elements which include forming boards 2, spaced apart foils 3 and
low vacuum blades 4. Suction box covers 5 together with Uhle box
covers 8 constitute dewatering elements.
[0003] Crucial to the formation of the sheet of paper (or board) in
the forming area is the drainage of the papermaking suspension and
the micro-turbulence generated in the papermaking suspension which
serves to eliminate agglomeration thereby enhancing the uniformity
of the papermaking suspension. The harmonic pitch of the
papermaking apparatus is the spacing on the paper table of the
forming board, forming foils and gravity foils which together
determine the natural harmonics of the wet end of the papermaking
apparatus and which is established at the time that the papermaking
apparatus is designed to give the desired drainage and
micro-turbulence. It can be a disadvantage of conventional
papermaking apparatus that the design is specified in accordance
with certain grades of paper (or board) and certain types or
quality of pulp.
[0004] Referring again to FIG. 1, the papermaking suspension is
ejected from a flow box or head box (not shown) onto the
papermaking wire 1. Commonly the forming board 2 which is a solid
unitary element may do little more than help to direct the
papermaking suspension flow onto the moving papermaking wires 1
prior to de-watering. However the forming board 2 may be provided
with grooves or slots to generate micro-turbulence. GB-A-2190932
discloses a solid forming board (known commercially as the
TURBOFORM.TM. board) in the surface of which one or more
transverse, open-ended slots are provided. The depth of the slots
may be varied by an insert to achieve the requisite degree of
micro-turbulence in the papermaking suspension whilst permitting
limited drainage. However the TURBOFORM.TM. board is able to take
little or no account of the natural harmonic pitch of a papermaking
apparatus. Moreover the TURBOFORM.TM. board is generally of little
use in a slow speed papermaking apparatus.
SUMMARY OF THE INVENTION
[0005] The present invention seeks to improve the versatility of a
papermaking apparatus by introducing into the forming area an
assembly of forming elements which together define a discontinuous
supporting surface for the papermaking suspension. More
particularly, the present invention relates to an assembly of
forming elements which takes account of and enhances the natural
harmonic pitch of the papermaking apparatus to accurately control
in the forming area the drainage of and micro-turbulence in the
papermaking suspension thereby satisfying a demand from customers
for improved paper quality (eg improved fibre and fines dispersal
throughout the sheet).
[0006] Thus viewed from one aspect the present invention provides
an assembly of forming elements including:
[0007] a primary blade capable of being positioned adjacent one or
more supply means at the wet end of a papermaking apparatus;
[0008] a first secondary support blade coupled to a leading face of
the primary blade by a first drainage deckle; and
[0009] optionally n consecutive additional secondary support blades
and n consecutive additional drainage deckles, wherein a trailing
face of the first additional secondary support blade is coupled to
a leading face of the first secondary support blade by the first
additional drainage deckle and a trailing face of the second to
n.sup.th additional secondary support blades is coupled
respectively to a leading face of the first to n-1.sup.th
additional secondary support blades by the second to n.sup.th
additional drainage deckle respectively, wherein n is an integer of
one or more,
[0010] whereby the upper surface of the primary blade, the first
secondary support blade, the first drainage deckle, the n
additional drainage deckles and the n additional secondary support
blades together define a discontinuous surface for supporting a
papermaking suspension being carried by a carrier from the wet end
to an output end of the papermaking apparatus.
[0011] Viewed from a further aspect the present invention provides
a papermaking apparatus capable of making a sheet of paper (or
board) from a papermaking suspension, said apparatus
comprising:
[0012] one or more supply means for introducing the papermaking
suspension into a wet end of the apparatus;
[0013] a carrier for carrying the papermaking suspension from the
wet end to an output end of the apparatus; and
[0014] an assembly of forming elements which include:
[0015] a primary blade positioned adjacent the one or more supply
means;
[0016] a first secondary support blade coupled to a leading face of
the primary blade by a first drainage deckle; and
[0017] optionally n consecutive additional secondary support blades
and n consecutive additional drainage deckles, wherein a trailing
face of the first additional secondary support blade is coupled to
a leading face of the first secondary support blade by the first
additional drainage deckle and a trailing face of the second to
n.sup.th additional secondary support blades is coupled
respectively to a leading face of the first to n-1.sup.th
additional secondary support blades by the second to n.sup.th
additional drainage deckle respectively, wherein n is an integer of
one or more,
[0018] whereby the upper surface of the primary blade, the first
secondary support blade, the first drainage deckle, the n
additional drainage deckles and the n additional secondary support
blades together define a discontinuous surface for supporting the
papermaking suspension.
[0019] It will be apparent that the assembly of forming elements
largely making up the forming area of the papermaking apparatus of
the invention may be advantageously extended to any desired length
to achieve the requisite formation characteristics simply by adding
additional secondary support blades and additional drainage deckles
(ie by increasing n). Moreover, in sharp contrast to conventional
rigid forming boards, the forming elements of the papermaking
apparatus of the invention may be assembled into the papermaking
apparatus quite straightforwardly to the desired length. To
exemplify its improved versatility, the papermaking apparatus may
be used with a broader range of paper (or board) grades (eg varying
in weight) than has hitherto been possible irrespective of the
carrier speed.
[0020] The upper surfaces of the forming elements together present
a discontinuous supporting surface (paper table) to the papermaking
suspension. This discontinuous surface serves intrinsically to
generate micro-turbulence in the papermaking suspension. For this
purpose, the profile, thickness and/or relative positioning of the
primary blade, the first secondary support blade, the first
drainage deckle, the n additional drainage deckles and the n
additional secondary support blades may be varied to suit the
requirements of the papermaking process. Typically the
discontinuous supporting surface is irregularly discontinuous. For
example the discontinuous supporting surface may be stepped (eg
irregularly stepped).
[0021] Preferably the upper surfaces of the primary blade, the
first secondary support blade and the n consecutive additional
secondary support blades are substantially coplanar at a first
height and the upper surface of at least one (preferably each) of
the first drainage deckle and n consecutive additional drainage
deckles is at a height different from the first height.
Particularly preferably the upper surfaces of the primary blade,
the first secondary support blade and the n consecutive additional
secondary support blades are substantially coplanar at a first
height and the upper surface of each of the first drainage deckle
and n consecutive additional drainage deckles is at a height
different from the first height whereby to define a discontinuous
surface which is stepped. More preferably the upper surfaces of the
first drainage deckle and n consecutive additional drainage deckles
are substantially coplanar at heights different from each other and
from the first height whereby to define a discontinuous surface
which is substantially irregularly stepped. Alternatively (if
desired) the upper surfaces of the first drainage deckle and n
consecutive additional drainage deckles are substantially coplanar
at a common height different from the first height whereby to
define a discontinuous surface which is substantially regularly
stepped
[0022] Alternatively or additionally the upper surfaces of at least
one of (preferably each of) the first drainage deckle and n
consecutive additional drainage deckles is angled (eg angled at a
height different from the first height). Typically the upper
surface is angled downwardly from trailing to leading edges of the
upper surface. The difference between the first and second height
and any degree of angling may be judiciously chosen to generate the
desired micro-turbulence into the papermaking suspension. For
example, each of the first drainage deckle and n consecutive
additional drainage deckles may be angled at a different angle to
fine tune the micro-turbulence. Typically the angle is in the range
1-4.degree. from the horizontal.
[0023] Additionally or alternatively at least one (preferably more
than one eg each) of the first drainage deckle and n consecutive
additional drainage deckles generates micro-turbulence in the
papermaking suspension by extrinsic means. In a preferred
embodiment, at least one (preferably more than one eg each) of the
first drainage deckle and n additional drainage deckles is adapted
to transmit a means for generating micro-turbulence in the
papermaking suspension. Preferably the means for generating
micro-turbulence is sourced externally and may be a physical means
or electromagnetic radiation. For example, the means for generating
micro-turbulence may be pulses of fluid (eg gas or liquid such as
water) or vibrations (eg sonic vibrations).
[0024] Preferably the upper surface of at least one (preferably
more than one eg each) of the first drainage deckle and n
consecutive additional drainage deckles comprises a groove adapted
to transmit fluid (eg water) onto its upper surface. Typically the
groove is a closed end groove (ie a groove extending downwardly
from and transversely along the upper surface remote from its
opposing edges). The transverse end walls of the groove may be
curved (eg semicircular).
[0025] Preferably the groove is adapted to transmit pulses of fluid
(eg water) onto its upper surface. Preferably to an end wall of at
least one (preferably more than one eg each) of the first drainage
deckle and n consecutive additional drainage deckles extends a
transverse slot (eg a transverse substantially circular slot)
outwardly from a transverse end wall of the groove. Particularly
preferably to a first and second end wall of at least one
(preferably more than one eg all) of the first drainage deckle and
n consecutive additional drainage deckles extends respectively a
first and a second transverse slot (eg a transverse substantially
circular slot) outwardly from a first and second transverse end
wall of the groove respectively. The or each transverse slot is in
fluid communication with the groove and therefore with the upper
surface so that pulses of fluid (eg water) may be transmitted
therethrough onto the upper surface. The depth of the groove, the
nature of the means for generating micro-turbulence and the manner
in which the means for generating micro-turbulence is applied may
be judiciously chosen to refine the micro-turbulence generated
intrinsically in the papermaking suspension (eg by dampening or
amplifying the micro-turbulence imparted by the natural harmonic
pitch of the forming elements) which in turn assists fibre
formation and dispersal of fines throughout the sheet (ie improves
sheet quality).
[0026] The first drainage deckle and n additional drainage deckles
may couple the leading and trailing faces of a first and second
consecutive forming element in any convenient manner. Preferably
the leading and trailing faces of the drainage deckle engage the
first and second consecutive forming elements through male and
female portions (eg interlocking male and female portions) of any
convenient coupling arrangement. The male and female portions may
be a tongue and groove or a dovetail-type arrangement. Preferably
the male and female portions are a tongue and groove. More
preferably the trailing face of the drainage deckle bears a tongue
adapted to engage a complementarily shaped groove on the leading
face of the first forming element and the leading face of the
drainage deckle bears a groove adapted to be engaged by a
complementarily shaped tongue on the trailing face of the second
forming element.
[0027] The thickness and/or profile of the first drainage deckle
and n additional drainage deckles may be different but are
preferably largely the same and may (in practice) be judiciously
chosen to accurately control drainage of and micro-turbulence in
the papermaking suspension as discussed above. Typically the
trailing and leading faces of the drainage deckle are substantially
perpendicular to the upper and lower surfaces. The upper edge of
the leading face typically comprises a shoulder and the upper edge
of the trailing face is chamfered.
[0028] The primary blade may be positioned immediately after the
one or more supply means and support the carrier substantially at
the point where (in use) the papermaking suspension flows onto the
carrier. Typically the trailing face of the primary blade tapers
downwardly and forwardly and the leading face is substantially
non-tapered (ie substantially perpendicular to the upper and lower
surfaces) and incorporates the male or (preferably) female portion
(eg a groove) of any convenient male/female coupling arrangement
(eg a tongue and groove). The upper edge of the leading face
typically comprises a shoulder and the upper edge of the trailing
face is chamfered. The primary blade is normally (but not
necessarily) the same thickness as each of the first and n
additional secondary support blades. The lower face may be adapted
to enable the primary blade to be mounted on the forming box (eg by
incorporating the male or (preferably) female portion of any
convenient male/female coupling arrangement such as a dovetail type
arrangement or (preferably) T-bars/T-slots).
[0029] The carrier may be a wire (or wires), belt, mesh or other
arrangement driven between the wet end and the output end in a
conventional manner. The carrier may be at least partly composed of
fabric, metal or plastic which may be woven or otherwise
manipulated.
[0030] The one or more supply means may be head boxes or flow boxes
as desired.
[0031] The first secondary support blade and n optional additional
secondary support blades (which may be different but are preferably
the same) support the carrier largely in the area where sheet
formation takes place (the forming area). Typically the trailing
face of the first secondary support blade and n optional additional
secondary support blades is substantially perpendicular to the
upper and lower surfaces and incorporates the female or
(preferably) male portion (eg a tongue) of any convenient
male/female coupling arrangement (eg a tongue and groove). The
upper edge of the leading face typically comprises a shoulder and
the upper edge of the trailing face is chamfered. The first
secondary support blade and n optional additional secondary support
blades are normally (but not necessarily) the same thickness as the
primary blade. The lower face may be adapted to enable the first
secondary support blade and n optional additional secondary support
blades to be mounted on the forming box (eg by incorporating the
male or (preferably) female portion of any convenient male/female
coupling arrangement such as a dovetail type arrangement or
(preferably) T-bars/T-slots).
[0032] By substituting the forming elements of a conventional
papermaking apparatus with the assembly as hereinbefore defined,
the natural harmonic pitch of the conventional papermaking
apparatus is advantageously enhanced in a controlled manner.
[0033] Viewed from a yet further aspect the present invention
provides a method for constructing a papermaking apparatus as
hereinbefore defined comprising:
[0034] (a) obtaining a conventional papermaking apparatus
comprising one or more conventional forming elements in the forming
area;
[0035] (b) substituting at least one (preferably all) of the one or
more conventional forming elements with an assembly of forming
elements which include:
[0036] a primary blade positioned adjacent the one or more supply
means;
[0037] a first secondary support blade coupled to a leading face of
the primary blade by a first drainage deckle; and
[0038] optionally n consecutive additional secondary support blades
and n consecutive additional drainage deckles, wherein a trailing
face of the first additional secondary support blade is coupled to
a leading face of the first secondary support blade by the first
additional drainage deckle and a trailing face of the second to
n.sup.th additional secondary support blades is coupled
respectively to a leading face of the first to n-1.sup.th
additional secondary support blades by the second to n.sup.th
additional drainage deckle respectively, wherein n is an integer of
one or more,
[0039] whereby the upper surface of the primary blade, the first
secondary support blade, the first drainage deckle, the n
additional drainage deckles and the n additional secondary support
blades together define a discontinuous surface for supporting the
papermaking suspension.
[0040] In accordance with an embodiment of the method of the
invention, the conventional forming elements include a conventional
forming board and the primary blade of the assembly functionally
replaces the conventional forming board. The primary blade may be
(but is not necessarily) the same width as the forming board and is
generally the same length.
[0041] In accordance with an embodiment of the method of the
invention, the conventional forming elements include one or more
forming foils and the first and n optional additional secondary
support blades functionally replace the one or more forming foils.
In this embodiment, n will be determined by the user in accordance
with the demands of the application.
[0042] In a preferred embodiment of the method of the invention,
the forming elements are mounted individually on existing T-bars of
the forming box of the conventional papermaking apparatus thereby
retaining the harmonic pitch of the conventional papermaking
apparatus but refining it accordingly. In contrast, the rather more
cumbersome rigid TURBOFORM.TM. board is mounted in the conventional
papermaking apparatus on at least two T-bars simultaneously.
[0043] Viewed from an even yet further aspect the present invention
provides a kit of parts comprising one or more of the forming
elements selected from the group consisting of a primary blade as
hereinbefore defined, a first secondary support blade as
hereinbefore defined, n additional secondary support blades as
hereinbefore defined and n consecutive additional drainage deckles
as hereinbefore defined, said one or more of the forming elements
capable of being assembled into an assembly as hereinbefore
defined.
[0044] The present invention will now be described in a
non-limitative sense with reference to the accompanying Figures in
which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a side perspective view illustrating the present
invention;
[0046] FIG. 2 illustrates schematically an isolated side view of a
first embodiment of the assembly of forming elements of the
invention;
[0047] FIG. 3 illustrates schematically an isolated side view of a
second embodiment of the assembly of forming elements of the
invention;
[0048] FIG. 4 illustrates a primary blade;
[0049] FIG. 5 illustrates a secondary blade;
[0050] FIG. 6 illustrates a drainage deckle of the first
embodiment;
[0051] FIG. 7 illustrates a drainage deckle of the second
embodiment;
[0052] FIG. 8 illustrates a conventional papermaking apparatus in
use; and
[0053] FIG. 9 illustrates a papermaking apparatus of the invention
in use.
DETAILED DESCRIPTION OF THE INVENTION
[0054] FIG. 2 illustrates schematically an isolated side view of
the assembly of forming elements 1 of a first embodiment of a
papermaking apparatus of the invention. The assembly of forming
elements 1 includes a primary blade 2 positioned immediately after
the one or more supply means (not shown), a first secondary support
blade 3, first and second consecutive additional secondary support
blades 4a and 4b, a first drainage deckle 5 and first and second
additional drainage deckles 6a, 6b. The assembly of forming
elements 1 defines a discontinuous upper surface for supporting the
papermaking suspension carried by a papermaking wire 7.
[0055] The primary blade 2 is illustrated alone in FIG. 4. A
trailing face 42a of the primary blade 2 tapers downwardly and
forwardly. A leading face 41a of the primary blade 2 is
perpendicular to the upper and lower surfaces and is provided with
a shoulder 42 at its upper edge. The lower surface incorporates
T-shaped slots 49a, 49b which engage T-shaped bars on the forming
box.
[0056] The first secondary support blade 3 and first and second
additional secondary support blades 4a, 4b are the same and are
illustrated alone in FIG. 5. A trailing face 2 la of the first
secondary support blade 3 and first and second additional secondary
support blades 4a, 4b is perpendicular to the upper and lower
surfaces and is provided with a chamfer 500 at its upper edge. A
leading face 21b of the first secondary support blade 3 and first
and second additional secondary support blades 4a, 4b is
perpendicular to the upper and lower surfaces and is provided with
a shoulder 501 at its upper edge. The first secondary support blade
3 and first and second additional secondary support blades 4a, 4b
are the same thickness as the primary blade 2. The lower surface
incorporates a T-shaped slot 59a which engages a T-shaped bar on
the forming box.
[0057] The upper surfaces of the primary blade 2, the first
secondary support blade 3 and the first and second consecutive
additional secondary support blades 4a and 4b are substantially
coplanar at a first height.
[0058] The first drainage deckle 5, first additional drainage
deckle 6a and second additional drainage deckle 6b are essentially
(but not precisely) the same and are illustrated alone in
perspective view in FIG. 6. The upper surfaces 65 of each of the
first drainage deckle 5, first additional drainage deckle 6a and
second additional drainage deckle 6b are at heights different from
the common height of the primary blade 2, the first secondary blade
3 and the first and second additional secondary support blade 4a,
4b whereby to define a discontinuous surface which is substantially
irregularly stepped. Moreover the upper surface 65 of each of the
first drainage deckle 5, first additional drainage deckle 6a and
second additional drainage deckle 6b is angled at a different angle
in the range 1-4.degree.. The difference between the heights
creates voids 11a, 11b and 11c. The voids 11a, 11b and 11c and the
variable angling of the upper surfaces 65 of the first drainage
deckle 5, first additional drainage deckle 6a and second additional
drainage deckle 6b contribute to the generation of micro-turbulence
in the papermaking suspension.
[0059] The trailing face 21a of the first additional secondary
support blade 4a is coupled to the leading face 21b of the first
secondary support blade 3 by the first additional drainage deckle
6a and the trailing face 21a of the second additional secondary
support blade 4b is coupled to the leading face 21b of the first
additional secondary support blade 4a by the second additional
drainage deckle 6b. The trailing face 1a of the first secondary
support blade 3 is coupled to the leading face 41a of the primary
blade 2 by the first drainage deckle 5.
[0060] The first drainage deckle 5 and first and second additional
drainage deckles 6a, 6b couple the leading and trailing faces of
the forming elements by a tongue and groove arrangement.
[0061] For example, a trailing face 71a of the drainage deckle 5
bears a tongue 72 adapted to engage a complementarily shaped groove
73 on the leading face 41a of the primary blade 2 and the leading
face 74a of the drainage deckle 5 bears a groove 75 adapted to be
engaged by a complementarily shaped tongue 76 on the trailing edge
of the first secondary support blade 3.
[0062] FIG. 3 illustrates schematically an isolated side view of
the assembly of forming elements 31 of a second embodiment of a
papermaking apparatus of the invention which is particularly useful
in slow speed papermaking apparatus. The assembly 31 is largely the
same as the assembly 1 described for the first embodiment
hereinbefore but has a different first drainage deckle 35 and first
and second additional drainage deckles 36a, 36b (see FIG. 7). Each
of the first drainage deckle 35 and first and second additional
drainage deckles 36a, 36b is adapted to introduce micro-turbulence
into the papermaking suspension by extrinsic means. Each of the
first drainage deckle 35 and first and second additional drainage
deckles 36a, 36b comprises a closed end groove 301 extending
downwardly from and transversely along the upper surface 300. To an
end wall 302 of each of the first drainage deckle 35 and first and
second additional drainage deckles 36a, 36b extends a first
transverse circular slot 303 outwardly from the groove 301. To an
opposing end wall 304 of each of the first drainage deckle 35 and
first and second additional drainage deckles 36a, 36b extends a
second transverse circular slot 305 outwardly from the groove 301.
Through the slots 303, 305 may be transmitted pulses of water which
reach the upper surface 300 through the groove 301 and generate
micro-turbulence in the papermaking suspension.
[0063] To illustrate the general improvements in the generation of
micro-turbulence, FIGS. 8 and 9 illustrate respectively a
papermaking suspension during dewatering in a conventional
papermaking apparatus and a papermaking apparatus of the
invention.
[0064] It will be understood that this disclosure, in many
respects, is only illustrative. Changes may be made in details,
particularly in matters of shape, size, material, and arrangement
of parts without exceeding the scope of the invention. Accordingly,
the scope of the invention is as defined in the language of the
appended claims.
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