Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~2~1990
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WATER JET EDGE TRIMMING STATION
FOR USE IN PAPERMAKING MACHINE
Field of the Invention
The present invention is directed to a water jet edge trimming
apparatus for trimming the edge from a moving web in a papermaking
machine. More specifically, the present invention is directed to a water jet
s edge trimmer system for trimming coated paper.
Background of the Invention
In the papermaking industry certain applications require edge trimming
of the paper web during web travel in the papermaking machine. One such
application occurs in the manufacture of coated paper. Coating can be done
to "on-machine" or "off-machine". Coating on-machine means that the paper is
made in the normal fashion and an additional coating station is provided such
that the paper is coated as it travels in the papermaking process.
During the coating process the "raw stock" paper is coated across the
width of the web except for the edges of the paper where a trim of 0.5 to 3
is inches of the paper web is not coated. Both sides of the paper web may be
coated with plastic or paint products which can make up a significant part of
the paper weight. The uncoated edges must be trimmed off before
processing the paper further, such processing involving calendering or
supercalendering, for example. This trimming step is typically done by means
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of a mating pair of rotary slitting knives. Slitting knives, or "slitters" are
used
to trim paper edges after the coating station thereby removing un-coated
edges of the paper from the traveling web. Slitters are also employed up-
stream of the coating station to cut the paper web prior to coating preventing
s cracked edges from entering the coater because coating of cracked edges
leads to further complications.
There are disadvantages associated with the use of knives. Knives
require high maintenance due to abrasive wear of the coating filler material,
i.e. calcium carbonate or titanium dioxide. Further, slitter knives have a
to tendency to separate (jamming) when flying splices of overlapping paper
sections joined together by tape having triple the basis weight pass by the
knife slitters. Jamming leads to paper breaks. Also, slitter knives are very
sensitive to paper wrinkles that enter the slitting zone resulting in edge
tearing of the paper. Further, it is very difficult to enter the running paper
web
is into the paired slitter knives without crimping the edge which can lead to
web
breaking.
For the above stated reasons, it is standard practice in the paper
making industry to avoid cutting the trim on the on-machine coater, because
one paper break may cost up to $8000 in lost production time. To avoid the
2o potential hazards associated with on-machine trimming, trimming is usually
done off-machine on a re-reeler machine which is a separate machine used
to un-reel, edge trim and re-reel the paper web. Such a re-reeler operation
requires significant labour costs to operate in addition to the capital costs
of
purchasing such a machine. Clearly, on-machine trimming of the edge of the
2s paper web during the coating section of the machine would be the preferred
choice of manufacture if the risks associated with web breakage by edge
trimming after the coating station could be avoided or reduced.
If a water jet could be used to trim the edge of the coated paper, then
the disadvantages associated with the use of rotary knives in the on-machine
3o edge trimming would be avoided. The pressure of the water jet is sufficient
to
cut through flying splices of triple basis weight on the coated paper.
Further,
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changes in tension which can cause paper wrinkling have no apparent effect
on the water jet cutting ability to provide a clean cut without tearing.
While it is known to use water jets to cut a paper web, the general
teaching in the art is to cut the web with the water jet impinging the web
s surface in a direction normal to the web surface to maximize the cutting
efficiency of the waterjet. However, when this teaching was applied by the
applicant to coated paper webs, some disturbing problems were experienced
which adversely affected the cutting performance of the water jet.
One problem experienced with using such a normal directed water jet
to to effect trimming of the coated paper is backsplash. It should be
understood
that the water jet pressure and nozzle orifice can be chosen such that the
water jet impinges the paper web at speeds in excess of 2000 feet/second or
about 615 meters/second. The energy of this impact transforms the fluid into
a gaseous state. This represents expansion in volume in the order of 1250
Is times. Consequently the gas stream formed by the water jet impinging the
web results in a cloud of fumes when the paper is of sufficient weight and
thickness to backsplash minute portions of the water jet spray. The fumes and
atomized paper particles backsplash towards the nozzle head of the water jet.
The coating mass on the paper which contains calcium carbonate is splashed
2o from the cutting surface back to the nozzle head and is also sprayed on
other
parts of the paper. During use, the fine particles of calcium lump together to
form and build up extending down from the nozzle to the surface of the paper
in a gummy "stalacite" type of deposit. Eventually this "stalactite" type of
deposit breaks off in a lump and travels on the boundary layer of the good
2s paper web to the wind up station where the lumped particles are glued to
the
next layer of paper. Upon un-winding, the glued together layers are ripped at
the edge leading to complete web breaks across the paper web. Clearly, this
will result in down time to re-splice and feed the tail of the paper web
through
the machine. Furthermore, splattering of the calcium deposits on the
3o boundary edge of the coated paper deteriorates paper quality.
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The use of water jets to perform slitting, tail cutting and trimming has
been disclosed in the patent literature, but there is no disclosure as to how
to
use the water jets to cut an "unfriendly' paper web such as coated paper
during on-machine operation. For example, U.S. patent 3,996,825 issued
s December 14, 1976 to Rupert Terry discloses a water jet cutter for cutting
and trimming a web. A first water jet impinges the web from below the web at
a normal angle of 90° to the plane of the web. A second water jet
impinges
the web from above the web at the same point as the lower water jet impinges
the web. The upper or second water jet is angled relative to the vertical axis
to or axis normal to the plane of the web to direct the second water jet
towards
the outside edge of the paper web such that the water jet forces the cut web
edge away from the existing web to the outside of the cutting station. The
patent teaches that various angles relative to the vertical can be used by the
second water jet as long as the jet is emitted directly downwardly and toward
Is the outside edge. A suitable angle is typically about 45 degrees. Such a
trimmer would not work in cutting coated paper because splashing from each
water jet onto the other water jet is subject to the problems associated with
the above noted trimming of coated paper on-machine.
U.S. patent 5,068,513 issued November 26, 1991 to Donald Gangemi
2o teaches a water jet cutter that is used with a laser as a slitter. In one
embodiment, the water jet cutter is angled rearwardly or upstream with
respect to the direction of web travel. However, the patent teaches that the
relative orientation of the water jet nozzle and the laser is not deemed to be
of critical importance so long as the water jet nozzle and the laser are
2s focused at the same general spot on the traveling web. Also, DE patent
application 4,28,272 laid open October 29, 1992 in the name of J.M. Voith
GmbH discloses the use of either rotary cutters, water jets or lasers to cut a
tail in a paper by angling the resultant cut with a vector component in
opposing direction to the direction of web travel and in a second direction
into
3o the center of the web away from the edge of the web. Again these patents
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are not concerned with backsplash and would be subject to waste deposit
build upon the nozzle heads and laser heads.
While prior art water jet cutters for use in tail cutting, slitting and to a
lesser extent trimming are known in the paper making industry, none of these
s patents addresses the problems associated with backsplash and the effects
of backsplash on clotting the nozzle and effecting paper quality as a result
of
cutting through coated paper on-machine. There is a need for a water jet
edge trimming system which is not subject to the disadvantages associated
with the knife edge trimmers of the prior art.
io SUMMARY OF THE INVENTION
The present invention is directed to a water jet cutting apparatus that is
not subject to the problems associated with backsplash while trimming the
edges of paper on-machine. While the present invention finds particular
advantage in cutting coated paper on-machine, aspects of the present
is invention may find application in cutting and trimming other grades of
paper
web including webs of considerably less basis weight such as tissue paper
where rewetting and redepositing of fines during trimming can cause deposit
problems.
In accordance with one aspect of the present invention a water jet
ao edge trimming station is provided for trimming the edge of a traveling web
in
a papermaking machine. The edge trimming station has first novel aspects in
the manner in which effluent by-products associated with cutting the web are
drawn below the cutting surface of the web to reduce backsplash and the
manner in which a cutting station is constructed to withstand wear associated
zs with paper striking the cutting station.
In accordance with a second novel aspect of the present invention the
water jet used to cut the paper is angled relative to the direction of paper
web
travel and the outside edge of the paper web travel. The angling of the water
jet relative to the direction of paper web travel, and in particular the
3o downstream direction, it is meant that the water jet may face downstream in
the direction of web travel and the waterjet cuts at an impact angle which in
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theory is the same as the exiting angle, but in practice the exiting angle is
slightly less than impact angle when the jet is facing downstream due to the
downstream speed of the traveling web. The relative angling of the water jet
is done with respect to a the vertical or normal axis passing through a plane
s of the web and the side edge of the web to reduce backsplash of effluent by-
products onto the water jet nozzle.
In accordance with yet a third novel aspect of the present invention the
construction of the water jet cutting apparatus of the present invention has
positive air pressure chamber surrounding the nozzle head of the water jet to
io maintain air flow over the nozzle head acting to drive away effluent
deposits
adversely affecting nozzle head performance.
In accordance with the first broad aspect of the present invention there
is provided a water jet edge trimming station for trimming an edge of a
traveling web in a papermaking machine. The station includes a water jet
is apparatus supported above the web for directing a water jet towards a point
of impingement against the web to cut through the web and form an edge trim
piece separate from the web. The water jet forms effluent by-products as it
cuts the web. The station includes a support table positioned below the water
jet and over which at least an edge portion of the web travels. The support
2o table includes a cutting station. The cutting station includes a hardened
cutting surface to better withstand cutting and wearing associated with the
paper striking the cutting surface. The cutting surface includes an effluent
receiving aperture positioned directly below the point of impingement of the
water jet through which passes the water jet after cutting through the web.
as The cutting station includes a negative pressure apparatus adapted to draw
the water jet and the effluent by-products through the receiving aperture to
accept the effluent by-products.
By using a negative pressure or vacuum to draw effluent by-products
through the effluent receiving vacuum assisted aperture in the cutting
station,
3o the effluent by-products can be removed from the papermaking machine.
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Backsplash onto the traveling web and nozzle head is diminished resulting in
improved continued water jet cutting performance and paper quality.
The hardened cutting surface preferably comprises a ceramic shoe
mounted raised above the support table by about 1 to 4 mm. The effluent
s receiving aperture is located in the ceramic shoe. By raising the ceramic
shoe or platform above the remainder of the cutting station, then only the
ceramic shoe is exposed to wear. The use of a ceramic shoe improves
longevity of the cutting station. Any suitable material can be used that can
withstand the wear and cutting associated with the paper striking this surface
io and in particular over the vacuum assisted aperture. In the preferred
embodiment, there is a cut out section on the bottom surface of the ceramic
shoe adjacent the effluent receiving. The purpose of using a cut out section
is to reduce the depth of the effluent receiving aperture and land area in the
aperture struck by the water jet and paper so as to prevent buildup of
Is effluents in the downstream land area of the aperture.
The cutting station preferably includes a draft tube extending from the
effluent receiving aperture into the cutting station. The cutting station
includes a chamber into which the draft tube partially extends to define an
outer passage surrounding the draft tube. The chamber includes a water
2o inlet and an air inlet adjacent the hardened cutting surface which permit
the
introduction of water and air into the outer passage surrounding the draft
tube
and extending into the cutting station. The cutting station further includes a
mixing zone located below the draft tube and the outer passage for mixing the
air and water from the outer passage and effluent by-products from the draft
2s tube.
It is envisaged that the effluent receiving aperture is located a
predetermined distance upstream of a downstream end of the cutting station
so as to prevent buildup of effluent by-products on the hardened surface of
the cutting station downstream of the effluent receiving aperture. By
3o maintaining this distance relatively short, any effluent by-products that
are not
exhausted through the effluent receiving aperture have a relatively short area
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to buildup gummy deposits which could adhere to the hardened surface of the
cutting station. In accordance with the present invention the predetermined
distance is in the range of 5 to 50 mm and preferably about 40 mm.
In the preferred embodiment, the support table, on which the raised
s cutting station is mounted includes two platforms. A first raised platform
extends from the cutting station downstream for supporting the traveling web.
A second platform stepped down relative to, or lower than, the first platform
also extends from the cutting station downstream for supporting the edge trim
piece separated from the web. By having the second platform positioned
io below the first raised platform, separation of the edge trim piece from the
continuing traveling web is facilitated. Furthermore, in the preferred
embodiment, an elongated slotted aperture is provided between the first and
second platforms. The purpose of a slotted aperture is to provide an
unsupported section in the web travel for the wet edges of the continuing
is traveling web and the traveling edge trim piece. It is believed that the
open
elongated slotted aperture allows the unsupported edges to dry and any
effluent by-product carried by the wet edges does not find a surface against
which effluent by-products can buildup ultimately effecting paper quality and
the trimming function.
Zo In accordance with a preferred aspect of the present invention, the trim
chute is attached to the support table. It should be understood that in an
alternative embodiment, the trim chute may be located further downstream
separated from the support table. In such an embodiment, it is possible to
separate the edge trim piece by means of air jets which also act to guide the
2s edge trim piece to the destination trim chute.
In accordance with a second broad aspect of the present invention
there is provided a water jet edge trimming station for trimming an edge of a
web in a paper machine where the web traveling past the station is relatively
flat defining a web plane. The water jet edge trimming station includes a
3o water jet apparatus having a nozzle supported in spaced relation from the
web plane for emitting a water jet along a water jet axis towards a point of
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impingement against the web to cut through the web and form an edge trim
piece separate from the web. The water jet forms effluent by-products as the
water jet cuts the web. The water jet axis has a first orientation offset by a
first predetermined angle relative to a normal axis extending at a right angle
s out of the web plane from the point of impingement such that the first
orientation of the water jet directs the waterjet in a first direction
relative to
web surface travel to reduce backsplash of effluent by-products onto the
nozzle. The water jet axis has a second orientation rotated by a second
predetermined angle about the normal axis from a line extending parallel to
to the direction of web travel passing through the point of impingement,
whereby
the water jet is directed towards the edge trim piece causing effluent by-
products to move towards the edge trim piece and away from the web to
reduce backsplash onto the nozzle and the web.
The first predetermined angle may be in the range of 15° to
45° and is
is preferably about 22° from the vertical.
The second predetermined angle may be in the range of 5° to
135°.
The preferred range for the second predetermined angle is in the range of
5°
to 89° and the water jet is directed generally in a downstream
direction. The
preferred second predetermined angle is about 30°. Alternatively, the
range
zo of the second predetermined angle is between 91 ° to 135° and
the water jet is
directed in an upstream direction. When directed in an upstream direction,
the first predetermined angle is to be chosen to cause the effluent by-
products to move laterally towards the edge of the web without being blown
back by boundary layer windage associated with the traveling web.
2s It is further contemplated to position the nozzle of the water jet within a
predetermined distance from the traveling web to maintain a laminar jet of
water to cut the web. Preferably, this distance is about 12 mm from the web.
It is also contemplated to include in the water jet station an auxiliary air
nozzle positioned immediately upstream and laterally from the water jet for
3o directing an air stream down on an edge of the traveling web to move the
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edge trim piece away from the traveling web and to further direct effluent by-
products away from the traveling web.
In accordance with a third broad aspect of the present invention there
is provided a water jet apparatus for use in an edge trimming station for
s trimming an edge trim piece from a traveling web in a papermaking machine
which produces effluent by-products during trimming. The water jet includes
a water jet nozzle head having a water inlet tube and a nozzle having an
outlet orifice through which a water jet is emitted. Additionally, an enlarged
nozzle head housing is attached to the water jet nozzle head to define a
io chamber surrounding at least a portion of the water jet nozzle head. The
enlarged nozzle head housing has a front surface spaced from and
surrounding the nozzle to define an air outlet passage around the nozzle.
The enlarged nozzle head housing includes an air inlet through which
pressurized air enters the chamber and flows towards and out of the air outlet
is passage to counteract backsplash of the effluent by-products.
The enlarged nozzle head housing is preferably curved to guide the
traveling web under the front surface to the water jet emitted from the outlet
orifice. Additionally, an auxiliary air nozzle can extend around the outer
surface of the front surface to direct an air stream across the web to the
20 outside of the web direct effluent by-products away from the nozzle head
and
traveling web towards the edge trimmed. Preferably, the outlet orifice
extends forward of the front surface of the enlarged nozzle head housing.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the nature and objects of the present
2s invention reference may be had to the accompanying diagrammatic drawings
in which:
Figure 1 is a side-elevation view of a portion of a coating section in a
paper making machine showing the positioning of the trimming station
downstream from the coating station;
3o Figure 2 is a plan view of the traveling web of paper showing the
relative positioning of the water jet and cutting table to the traveling web;
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Figure 3 is a side sectional view taken along section line III-III in
Figure 2, which section line extends along a line rotated about the normal
axis and is bent at the point of impingement to extend along the cut edge of
the paper, showing the cutting action of the water jet and the relative
s positioning of the cutting table below the surface of the web;
Figure 4 is a three dimensional illustrative view of the water jet axis
relative to the point of impingement on the paper web; and,
Figure 5 is an enlarged view of the cutting station and support table as
shown in Figure 3.
Io DETAILED DESCRIPTION OF EMBODIMENTS
Referring to Figure 1 there is shown a coating section 10 of a paper
making machine. A water jet edge trimming station or apparatus is shown
generally at 12. It should be understood that the coating process occurs
upstream of the trimming station 12. While the preferred application for the
Is present invention is in the coating section of a paper making machine, the
water jet trimming station 12 may be located in any portion of a papermaking
machine that requires edge trimming. Furthermore, the present invention
lends itself to applications where pronounced or large amounts of backsplash
occur due to the water jet cutting through heavier grades of paper and/or
2o coated paper.
In Figure 1 the web or paper web 14 is shown passing through water
jet trimming station 12. Typically, web 14 is threaded first by ropes) 16. To
permit access to the web 14 at the edge trimming station 12, a separator
sheave 18 lifts the ropes) 16 from the web 14 at first sheave 20. The ropes
Zs 16 pass over roller 22 and again meet the web 14.
The trimming station 12 is supported on a base 21 and a movable
carriage 26. The movable carriage 26 moves back and forth in a direction
across the width of the web 14 to allow an initial edge cut into the web 14
and
subsequent slitting or edge trimming of the web 14. Carriage 26 carries the
3o support table 78 for the cutting station 13.
CA 02201990 2002-03-28
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Above the web 14, the trimming station 12 includes a water jet cutter
28 having a mushroom shaped head 30. The water jet cutter 28 is supported
above the web by an arm 38 (Figure 3) connected to the carriage 26. An
operator guard 32 is provided for safety covering the water jet. The water
jet is fed water from conduit 7. Conduit 7 is connected to a controlled valve
generally shown at 36.
In accordance with one embodiment of the present invention the angulation
of the water jet axis 48 to reduce backsplash is now described. While
Figures 3 and 5 show the water jet axis 48 being oriented by a first
predetermined angle 62 and Figure 2 shows the water jet axis 48 being
oriented by a second predetermined angle 58, Figure 3 is the best illustration
showing the means for obtaining the first, and in Figure 2, for the second
predetermined angles and Figure 4 is the best illustration to describe the
orientation of the water jet axis 48.
In Figure 3, the water jet cutter 28 includes a water jet nozzle body 33
through which the conduit or water inlet 7 is connected. At the other end of
water
jet nozzle body 33 is connected a jet nozzle retaining nut 45. The jet
nozzle retaining nut 45 has an outlet orifice 46 through which a laminar water
jet is emitted along water jet axis 48. The means for obtaining the angle
orientation of water jet axis comprises angular bracket 40 surrounding the
nozzle body 33 and connected by adjustment screw 42 to pin 44. Pin 44 is
pivotally connected to arm 38 to carriage support plate 36 of the trimming
station 12. The pivot axis 44 allows adjustment of water jet axis 48 by the
second predetermined angle. The pivot screw 42 allows the water jet cutter
28 to be secured in place at the first predetermined angle and also
adjustable sideways by slot 200.
Referring to Figures 2 to 5, and particularly Figure 4, the orientation of
the water jet axis 48 is described relative to the first and second
predetermined angles 62 and 58, respectively. The direction of web 14 travel
is shown generally by arrow 50. The cross-direction of carriage travel is
shown by arrow 49. The arrows 49 and 50 define a relatively flat web plane
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passing by the trimming station. The water jet axis 48 is directed at web 14
and cuts through web 14 at point of impingement 52. As the water jet cuts
through the web it produces an edge trim piece 54 that is separated from the
remainder of the web 14 continuing on its downstream travel of arrow 50.
s The edge trim piece 54 moves past trimming station 12 and into trim chute
56. The trim chute 56 is attached to the side of trimming station 12.
The orientation of the water jet axis 48 is shown angled by first
predetermined angle 62 relative to normal axis 61. Normal axis 61 is defined
as a line extending at a right angle out of the web plane through point of
to impingement 52. This normal axis may be referred to as a vertical axis when
the web plane is running horizontally past the trimming station 12. In the
preferred embodiment of Figure 4, the first predetermined angle 62 is shown
to be about 22°. This angle may vary between 5° and 45°.
In Figure 4 a
broken line 57 extends parallel to the web travel 50 and edge of the web 55
is upstream of the point of impingement 52. Broken line 57 is shown to pass
through point of impingement 52 and lie on the web plane. The second
predetermined angle 58 is shown to be rotated about normal axis 61 from line
57. The second predetermined angle may lie in the range of 5° to
135° and
in the preferred embodiment shown is about 30°. This results in a
generally
ao downstream and cross-stream direction of angulation of water jet 48. For
illustrative purposes, the angular rotation of water jet axis 48 about normal
axis 61 on the web plane is shown by broken line 59. Also, for illustrative
purposes broken line 63 extending parallel to axis 61 is shown.
By so orienting the water jet axis 48, backsplash associated with the
2s water jet splashing back onto the water jet nozzle and web 14 continuing to
travel along arrow 50 is reduced. Further, the fog 60 (Figure 3) formed by
effluent by-products of minute particles of paper and water during cutting are
directed away from the nozzle 45 towards the edge trim piece 54, and trim
evacuation chute 56.
3o Another aspect of the present invention relates to the construction of
water jet cutter 28 as best shown in Figure 3. In particular to protect the
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nozzle retaining nut or head 45 and orifice 46 from buildup of stalactite, the
water jet is provided with a mushroom shaped head or cap shown generally
at 64. The mushroom head 64 forms part of an enlarged nozzle head
housing 66 attached with a base plate or flange 68 to the water jet nozzle
s body 33. Forward of the base plate 68 is provided the mushroom front
surface 64. The curved surface 64 has an annular aperture spaced from the
nozzle head 45 defining an air outlet passage 70. The base plate 68 and
mushroom shaped front surface cover 64 together form a chamber 72.
Pressurized air is communicated into chamber 72 through air inlet tubing 74.
io The pressurized air entering chamber 72 exits the chamber 72 at air outlet
passage 70 around the nozzle head 45 causing a positive air flow pressure
away from the outlet orifice 46 of the water jet 48. This positive air flow
pushes potential effluent by-products away from the waterjet orifice 46 and
nozzle head 45. Also located upstream and laterally of the water jet
is apparatus 28 is an additional air nozzle 75 (Figure 2). Air nozzle 75 is
connected to air supply 34 to blow additional air beside or across the cutting
point of impingement 52 to move fog 60 downstream and away from the
stream from the water jet orifice 46. Further, nozzle 75 directs the edge trim
54 immediately following the cut at the point of impingement 52 into the trim
2o chute 56.
The waterjet 48 maintains a laminar flow to cut through the paper web
14. In particular, when a flying splice passes beneath the water jet cutting
apparatus, this portion of the web may have three times the basis weight of
the web 14 normally passing beneath the cutting jet. To ensure that a cut is
2s maintained, the nozzle head of the water jet 48 is maintained at the
predetermined distance above the web 14 to maintain the laminar flow of the
water jet. In accordance with the present invention, the outlet orifice 45 of
the
water jet cutter 28 is maintained about 12 mm from the web surface. As this
is not a large distance and the effects of backsplash would result in limited
30 operation of the water jet cutter 28 prior to cleaning if it were not for
the
features taught by the present invention. Furthermore, within the operating
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environment of the water jet trimmer, the nozzle orifice has a diameter in the
range of 0.07 to 0.153 mm. Also, the water jet has pressures in the order of
16,000 to 35,000 PSIG. This results in the waterjet hitting surface of the
paper at speeds in excess of 615 meters/second.
s Another aspect to the present invention relates to the trimming station
12 as shown below the web 14 in Figures 2,3 and 5. The trimming station 12
includes a support table 78 over which at least an edge portion 77 of the web
14 travels. The portion of the trimming station 12 located below the web 14
performs a novel function in waterjet cutting. The purpose of the trimming
io station 12 below the web 14 is to evacuate effluent by-products downwardly
away from the point of cutting impingement 52. To accomplish this the
trimming station 12 further includes a cutting station 13 mounted on a support
table 78. The cutting station 13 has a hardened cutting surface 82. The
surface 82 comprises a ceramic shoe mounted raised above the cutting
is station 13 of support table 78. It is also apparent from the drawings that
the
cutting station 13 has beveled or sloped edge 79. Sloped edge 79 allows
the paper web 14 to run up over the support table 78. The ceramic surface 82
also has bevelled edges and is sufficiently hard to better withstand cutting
and wear associated with the waterjet cutting and abrasiveness of coated
Zo paper.
The ceramic shoe 82 includes an effluent receiving aperture 84. The
ceramic shoe has an undercut or cut out 83 (Figure 5) below the aperture 84
to minimize the amount of land area the jet is striking within the aperture.
Because the effluent by-products contained in the waterjet have adhesive
zs characteristics, the smaller the depth of the aperture 84 the less build-up
of
residues can occur in the aperture resulting in exhausting of the effluent by-
products below the web. At the same time the wear resistance of the shoe
must be maintained. In the preferred embodiment, it has been found that the
depth of this aperture should be in the order of 2 to 4 mm. The axis of the
3o effluent receiving aperture 84 is preferably in alignment with the waterjet
axis
22~199U
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48. It should be understood that the aperture could be cone shaped with a
conical wall of the aperture lying parallel to the waterjet axis 48.
The cutting station 13 further includes a draft tube 88 connected in
fluid flow communication with the effluent receiving aperture 84. The draft
s tube 88 extends approximately 75 to 100mm into a mixing zone 90. The
preferred extension of the draft tube is about 100mm. The mixing zone 90 is
connected to exhaust or a negative pressure apparatus 100(Figure 1). Pipe
92 surrounds the draft tube 88 and is spaced from the draft tube 88. An outer
passage 94 is located between the pipe 92 and the draft tube 88. Pipe 92
to has an air inlet 98 and a water inlet 96. An air control valve 85 controls
the
volume of air drawn from the environment. Water valve 87 controls flow of
water into inlet 96; together the valves 85 and 87 control negative pressure
or
vacuum in the mixing zone 90. Due to the negative pressure, the water
entering through water inlet 96, and air entering through inlet 98 cause the
Is effluent by-products to be drawn through aperture 84 to be mixed in the
mixing zone 90. This allows for a dilution of the effluents to facilitate
removal
from the cutting station. The mixing zone 90 is connected to exhaust
100(Figure 1)
By drawing effluent by-products into the cutting station, the present
ao invention diminishes the amount of fog or potential backsplash which would
otherwise remain below web 14 and cutting table 78 and could result in
uneven buildup of by-products effecting function of the edge trimmer.
The aperture 84 at point of impingement 52 is located a distance 110
upstream from the downstream end 122 of the cutting station 13. This
2s distance 110 is about 40mm. By maintaining this distance relatively short
below 50mm, there is an insufficient surface length over which the web 14
and trim piece 54 travel thereby minimizing the surface area over which
gummy deposits of effluent by-products can buildup creating a ridge of
hardened material that can adversely effect the cutting performance of the
3o water jet station. This buildup is the result of effluent by-products or
2201990
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backsplash that remains below the surface of web 14 and are not drawn into
aperture 84.
The cutting station 13 in addition to the raised ceramic shoe 82
includes a first raised platform 126 extending downstream of the cutting
s station 13. The station 13 further includes a lower initially or stepped
down
second platform 128. The platforms 126 and 128 are at the same height
close to the ceramic shoe 82. Platform 128 curves and is offset below
platform 126 in the direction of web travel. Platforms 126 and 128 are
separated by an elongated slotted aperture 130. The purpose of the platform
Io 126 is to temporarily support the traveling web 14 and the purpose of the
second platform 126 is to temporarily support the edge trim piece 54 prior to
disposal in the trim chute 56. The raising of the first platform 126 relative
to
the second platform 128 provides for better separation of the edge trim piece
54 from the coated web 14. The elongated slotted aperture 130 provides an
is open space between the platforms 126 and 128 over which the wet edges
132 and 134, respectively, of the cut web 14 and edge trim piece 54 are
allowed to dry so that effluent by-products do not build up on a surface
effecting paper quality and the trimming operation.
While the foregoing description has been made in reference to the
2o drawings and an "on-machine" coating section of a papermaking machine, it
should be understood that various aspects of the present invention may find
application in other parts of papermaking machines as would be readily
apparent to a man skilled in the art.
