Note: Descriptions are shown in the official language in which they were submitted.
2a93~39
KNIFE VALVE
BACKGROUND OF THE INVEN~ION
1. Field of the Invention
The present invention relates to knife
valves and, more particularly, to a knife valve
adapted for use in paper mills.
2. DescriPtion of the Prior Art
Knife valves are used, for instance, in
paper mills as they are axially short, and thus
light and economical since they are made of
stainless steel. Furthermore, the valve's knife
blade can cut through solids such as pulp contained
in the liquid which circulates therethrough.
On the other hand, these knife valves are
bonnet-less in order to prevent, for example, the
pulp from jamming the valve stem within the bonnet.
Therefore, such knife valves require that the knife
blade of the valve which moves up and down and thus
in and out of the valve body seals the seat of the
valve as well as the knife itself. An elliptical
packing chamber disposed around the knife blade is
used to seal the knife. The surface which has to be
sealed is, in such a case, so large that the seal
has to be tightened more and more up to a point
where the seat scratches the surface of the knife
blade after the valve has been opened and closed a
large number of times, which results in the valve
leaking. Environmentally and down-time wise, such
failures are often unacceptable.
Also, in high performance valves, when the
frequency of operation is large and especially if
there is a requirement for high pressure operations,
that is around 150 PSI, and sealing in two
directions, the packing chamber rings of the valve
become overcharged with the changing load which
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results in the valve finally leaking through the
packing chamber. It is noted that, when a
bidirectional seal is required, gate valves cannot
be used because they become jammed with pulp.
In the above knife valves, the knife blade
must have a very precise finish in order that it
does not cut and damage the elliptical packing seal
while ensuring the tightness of the seal.
SUMMARY OF THE INVENTION
It is therefore an aim of the present
invention to provide an improved knife valve
including a bonnet and a standard cylindrical stem
seal.
It is also an aim of the present invention
to provide a knife valve having a seat which remains
tight under high pressure bidirectional operation.
It is still a further aim of the present
invention to provide a knife blade having a bypass
in its bonnet to prevent materials from accumulating
in the bonnet and consequently clogging the same and
hampering the operation of the valve.
Therefore, in accordance with the present
invention, there is provided a wafer knife gate
valve comprising a body having a valve seat, a knife
blade longitudinally movable by an operating means
in the body for opening and closing a lateral flow
passage defined through the body, a bonnet means for
completely enclosing the knife blade in the valve,
the bonnet means comprising therein guide means
defining a cavity with the operating means being
displaceable therein, a pair of chamber means being
defined in the bonnet means on each side of the
operating means, the bonnet means defining at an
upper portion thereof a passage means at least
partly around the guide means for permitting a
sufficient flow between the pair of chamber means
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when the valve is at least partly open, whereby a
substance flowing through the valve and into the
bonnet means can sufficiently circulate between the
pair of chamber means by way of the passage means
thereby preventing solids contained in the substance
from accumulating in the bonnet means and hampering
the operation of the valve, wherein, in a closed
position of the valve, the knife blade is seated
against the valve seat for isolating the flow
passage of a seat side of the valve from the bonnet
means and the flow passage on a seat-less side of
the valve.
A construction in accordance with the
present invention comprises a knife valve which
includes a body having a valve seat and also
includes a knife blade longitudinally movable by an
operating means in the body for opening and closing
a lateral flow passage defined through the body.
The valve seat is located on a first side of the
knife blade and in operative proximity thereto. A
bonnet means is provided for completely enclosing
the knife blade in the valve. Means are provided
for transferring a longitudinal force exerted by the
operating means on the knife blade when the knife
blade is in a closed position thereof at least
partially into a lateral force oriented towards the
first side. Therefore, the knife blade is forced
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against the valve seat in a tight bidirectional
seal.
In a more specific construction in
accordance with the present invention, the operating
means and the knife blade are slidably engaged one
to the other and include a first set of coacting
angular surfaces oriented for transferring the
longitudinal force into the lateral force.
In a still more specific construction in
accordance with the present invention, at least one
lug is provided on a lower portion of the body on a
second side of the knife blade. A lower portion of
the knife blade and the lug define a second set of
coacting angular surfaces adapted to urge the knife
blade against the valve seat when the knife blade is
in the closed position.
In a still more specific construction in
accordance with the present invention, the operating
means comprises a cylindrical stem having a blade
connecting member at a lower end thereof. The blade
connecting member includes a neck portion and a head
portion extending horizontally at a lower end of the
neck portion towards the first side of the knife
blade and engaging a slot defined in the knife
blade. The head portion and the slot define the
first set of coacting surfaces. The neck portion is
positioned on the second side of the knife blade and
between the knife blade and the body. Therefore,
the knife blade is sandwiched between the valve seat
on the first side thereof and the blade connecting
member and the lug on the second side thereof.
In another specific construction in
accordance with the present invention, the operating
means comprises a cylindrical stem extending through
the bonnet means. Annular sealing means are
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provided in the bonnet means around the stem to
prevent the valve from leaking.
The bonnet means may comprise a stem guide
means defining a cavity with the stem being slidable
therein. In such a case, a chamber means may be
provided around at least a portion of the guide
means. The chamber means communicates with the
cavity to allow a substance flowing through the
valve and within the guide means to access said
chamber means and circulate in the bonnet means to
prevent solids contained in the substance from
accumulating in the guide means of the bonnet means
and possibly hampering the operation of the valve.
The guide means may comprise a pair of
elongated member of arcuate cross-section and facing
each other in a spaced apart relationship to define
a pair of blade passages which join the chamber
means and the cavity. The chamber means is of
substantially annular cross-section and is disposed
concentrically around the elongated members.
In another specific construction in
accordance with the present invention, the valve
seat comprises a resilient seat including an annular
ring mounted to the body and including a pair of
resilient annular seals for providing seals between
the knife blade and the ring and between the ring
and the body. In a particular construction, the
resilient seals may be torus-shaped.
Another construction in accordance with
the present invention comprises a knife valve
including a body having a valve seat. The valve
also includes a knife blade longitudinally movable
by an operating means in the body for opening and
closing a lateral flow passage defined through the
body. A bonnet means is provided for completely
enclosing the knife blade in the valve. The bonnet
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means comprises a guide means defining a cavity with
the operating means being slidable therein. A
chamber means is provided around at least a portion
of the guide means. The chamber means communicates
with the cavity to allow a substance flowing through
the valve and within the guide means to access the
chamber means and circulate in the bonnet means.
This prevents solids contained in the substance from
accumulating in the guide means of the bonnet means
and possibly hampering the operation of the valve.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature
of the invention, reference will now be made to the
accompanying drawings showing by way of illustration
a preferred embodiment, and in which:
Fig. 1 is a perspective view of a knife
valve in accordance with the present invention in a
partly open position thereof;
Fig. 2 is a cross-sectional side view of
the knife valve shown in Fig. 1 but in a closed
position thereof;
Fig. 3 is a cross-sectional fragmented
front elevation of the knife valve in a partly open
position thereof;
Figs. 4 and 6 are cross-sectional plan
views of the knife valve taken respectively along
lines 4-4 and 6-6 of Fig. 3;
Fig. 5 is a top plan view taken along
lines 5-5 of Fig. 3 of the knife valve without its
bonnet;
Fig. 7 is an enlarged cross-sectional side
view of a resilient seat of the knife valve of Fig.
2 but with the valve being shown in a slightly open
position thereof;
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Fig. 8 is an enlarged cross-sectional side
view of the connection of the valve stem and knife
of Fig. 2; and
Figs. 9 and 10 are perspective views of
the seat side and the seatless side of the body of
the knife valve, respectively; and
Eig. 11 is a fragmented perspective view
partly in cross-section of the body of the knife
valve.
DESCRIPTION OF THE PREFERRED EMBO~IMENTS
Figs. 1 to 3 illustrate a knife valve V in
accordance with the present invention adapted for
use in paper mills and comprising a wafer type body
10 which includes body sections 10a and 10b which
respectively correspond to the seat side and to the
seatless side of the body 10 of the valve V. The
body section 10a defines a machined seat face 12 and
the assembled body 10 defines a circular passage 14.
Each side of the body 10 includes a vertical flange
16 defining a series of threaded holes 18 for
bolting the knife valve V between a pair of conduits
(not shown) in order that the valve may be used to
control the flow therebetween.
An upper portion of the body 10 includes a
horizontal flange 20 which defines a series of holes
22. A bonnet 24 which is positioned over the body
10 includes at its lower end a horizontal flange 26
defining a series of holes which are aligned with
the holes 22 of the body flange 20 when the bonnet
flange 26 is disposed thereover. A sealing gasket
28 is installed between the body flange 20 and the
bonnet flange 26. A series of bolts 30 extend
through the bonnet flange 26, the gasket 28 and the
body flange 20 with nuts 32 being engaged on the
bolts 30 to secure with a seal the bonnet 24 to the
valve body 10.
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2093~39
A knife blade 34 which is mounted
vertically in the valve V for displacement between
the valve seat 12 and the bonnet 24 is connected at
its upper end to a lower end of a stem 36 which
extends upwards through the bonnet 24. The knife
blade 34 defines a sharp edge 35 at its upper
peripheral portion to cut into any pulp
accumulation, as seen in Fig. 3. However, it is
noted that this sharp edge 35 is optional and that
the valve V may function very well without it.
The stem 36 includes adjoining upper and
lower portions 38 and 40 which are respectively
threaded and smooth. The threaded portion 38 of the
stem 36 is at least as long as the travel of the
knife blade 34. An upper portion 42 of the bonnet
24 defines a circular chamber into which are
installed a series of vertically stacked annular
packing rings 44 which are compressed by a gland
bushing 46 loaded and held in place by a loading
flange 48. A bolt and nut arrangement 50 secure the
loading flange 48 to the upper portion 42 of the
bonnet 24.
A handle assembly generally indicated by
the numeral 52 includes a mounting bracket 54 into
which are threadingly engaged the upper ends of four
mounting rods 56 which extend downwards therefrom
and through holes 58 defined in the bonnet flange
26, the gasket 28 and the body flange 20 with the
rods 56 being secured at their lower ends by nuts
60. A bushing 62 which is journaled in the mounting
bracket 54 defines a threaded cavity which engages
the threaded upper portion 38 of the stem 36. A
wheel handle 64 which includes a central opening is
fitted around an upper portion of the bushing 62
with a key 66 being provided in order that a
rotation of the wheel handle 64 causes the bushing
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62 to rotate in a horizontal plane within the
mounting brackets 54 thereby resulting in a vertical
linear displacement of the stem 36 and thus of the
knife blade 34 within the valve body 10 and the
bonnet 24.
The stem 36 slides inside a circular
cavity 68 defined in the bonnet 24 by a pair of stem
guides 69, as seen in Figs. 2 to 4. The body 10,
lower than the bonnet, also forms a stem guide
defined by a cavity 70. Bach stem guide 69 includes
a vertical elongated member of arcuate cross-
section, with both stem guides 69 facing each other
and being separated by a passage 71. The stem 36 is
prevented from rotating by a pin 72 sliding in a
vertical slot 74 defined in the body 10 and in
between the stem guides 69. The passage 71 between
the stem guides 69 and the body slot 74 can also
slidably accommodate the knife blade 34 (see Figs. 3
to 6).
As best seen in Fig. 8, an angular tapered
slot 76 which is defined in the upper portion of the
knife blade 34 slidably receives a tapered head 78
extending horizontally from the lower end portion of
the stem 36. Bottom lugs 80 which each define an
upwardly and inwardly beveled surface 81 are formed
in a lower portion of the valve body 10 on a same
side of the knife blade 34 as the tapered stem head
78, this side being the seatless side of the body 10
of the valve V. The knife blade 34 defines a sharp
beveled lower edge 82 which is substantially
parallel to the angular surfaces 81 of the bottom
lugs 80. Therefore, when the stem 36 and thus the
knife blade 34 are caused to displace downwards, the
knife beveled edge 82 contacts the bottom lugs 80 at
their angular surfaces 81, at which point a further
downwards vertical force acting on the stem 36 by
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way of the handle assembly 52 is transferred in a
horizontal force, as a result of the coacting
angular surfaces of the tapered slot and head 76 and
78, respectively, which can be parallel but which
are shown with a 1 angular offset to reduce the
friction forces between these coacting sliding
surfaces. Both the stem tapered head 76 and the
beveled body lugs 80 thus force the knife blade 34
laterally against the seat face 12 (and, more
particularly, against a soft seat disposed on the
seat face 12, such a soft seat being described
hereinbelow). When the valve V is closed, this
sealing contact is maintained by the stem force.
In normal conditions, the flow (from right
to left in Figs. 2, 7 and 8) forces the knife blade
34 against the seat face 12. When the flow is
reversed, the knife blade 34 is held in place by the
bottom lugs 80 and by the stem head 78 and the
angular surfaces of the tapered stem head 78 and
slot 76. This construction provides a high-
pressure bidirectional seal.
Guides 84 ensure the proper alignment of
the knife blade 34 when it travels between the open
and closed positions thereof, as seen in Fig. 3.
Referring now to Figs. 3 to 6, the
internal configuration of the valve body 10 is
designed so that pulp fibers are prevented from
collecting therein. The white water which contains
the pulp fibers travels in the pipes located
upstream and downstream of the valve V with a
swirling motion. The pulp flowing through the valve
body 10 is directed through wide passages 86 and 87
defined in body sections lOa and lOb respectively,
and into the bonnet 24. In view of the above
swirling motion, the pulp fibers enter the bonnet 24
on one side thereof, that is mainly along only one
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of the two sets of facing wide passages 86 and 87.
Since the movement of the pulp in the bonnet 24 is
almost completely blocked by the stem 36, the side
of the bonnet 24 receiving the pulp fibers will
become completely jammed, even before the fibers
become dry. Therefore, it is necessary to define a
bypass in the bonnet 24 and around the stem 36 to
allow the pulp fibers to reach the other side of the
bonnet 24 in a relatively unimpeded motion. Once
the pulp reaches this other side of the bonnet 24 it
returns to the passage 14 through the other set of
facing wide passages 86 and 87, whereby the pulp
fibers follow a substantially uninterrupted swirling
motion through the valve V. The bypass is made of
an annular cavity 88 defined at the top of the
bonnet 24 concentrically around the stem guides 69
to ensure a good circulation of the pulp fibers
outside of the circular cavity 68 in the bonnet 24,
instead of clogging the bonnet 24 and the stem 36 at
the circular cavity 68.
As seen in Figs. 2 and 3, an edge 90 is
defined on one side of the stem head 78 to provide
additional cleaning of the stem cavities 68 and 70
as it cuts through the pulp fibers. A further
passage 92 is also defined in the valve body 10 to
further ensure the proper flow of the pulp.
It is noted that a recess 94 (see Fig. 2)
defined in the top surface of the valve body 10 is
adapted to receive a shoulder 96 formed at the lower
end of the bonnet 24 thereby allowing the body 10
and the bonnet 24 to be perfectly aligned when they
are mounted together.
Now referring to Figs. 7 and 8, an annular
soft seat 98 may also be installed in the valve body
10 within the seat face 12. This resilient seat g8
consists of a ring 100 having a swaged front seal
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ring 102 which provides, in the closed position of
the knife valve V, the seal between the resilient
seat 98 and the knife blade 34. A rear seal ring
104 ensures the seal between the ring 100 and the
valve body 10. The resilient seat 98 is secured to
the valve body 10 by three clips 106 welded
equidistantly thereon. Each clip 106 includes a L-
shaped finger 108 which engages an annular recess
110 defined in the ring 100.
As well seen in Figs. 2, 5, 6 and 9, when
the valve V is in its closed position, the passages
86 on the seat side of the valve V are closed at
their lower ends by the seat face 12 thereby
ensuring the tightness of the valve V. Indeed, the
seat face 12 closes the passages 86 to prevent fluid
communication between the pipe on the seat side of
the valve V and the passages 86, and thus the bonnet
24 and the pipe located on the seatless side of the
valve V. If the flow is from left to right on Fig.
2, the seat face 12 closes the access to the
passages 86 and thus to the bonnet 24 and to the
other side of the valve V, whereas, if the flow is
from right to left, the fluid will fill the passages
87, the bonnet 24 and the passages 86, at which
point it is denied access to the seat side of the
valve V by the seat face 12.
As seen in Fig. 11, an opening 112 becomes
defined above the seat face 12 when the blade 34 is
completely raised (when the valve V is in its opened
position) to allow fluid to access the passages 86
as they are mainly hidden between the body section
lOa and the blade 34, and to provide communication
between the facing sets of passages 86 and 87
provided on both sides of the blade 34.
In the present invention, the knife blade
34 is free to fully contact the seat face 12 of the
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valve body 10. The presence of the bonnet allow for
the angular engagement of the stem head 78 in the
knife tapered slot 76 which results in a positive
torque induced closure of the knife blade 34. The
force applied on the stem 36 provides a positive
load on the knife blade 34. The angular engagement
of the stem head 78 and the gate blade 34 further
results in a bidirectional seat tightness.
Furthermore, the installation of the
bonnet 24 and the standard cylindrical stem seal or
packing rings 44 instead of the oval packing found
normally around the blades of knife valves ensures
that there is no leakage through the stem packing.
Therefore, the sealing of the valve is not achieved
by a packing around the knife but by a packing on
the valve stem which is rendered possible by the
provision of the bonnet and the ensuing result that
the knife is completely inside the valve. Also, the
smaller circular stem packing results in a reduced
required thrust to operate the knife valve while
ensuring a perfect tightness thereof.
Finally, the special body and bonnet
inside geometry of the present knife valve V
provides a continuous flushing of the valve for
preventing pulp accumulation therein. Indeed, the
bypass arrangement, which is mainly characterized by
the bonnet cavity 88 providing communication between
both sides of the bonnet 24 to bypass the stem 36,
prevents the wooden chips from accumulating within
the stem guides 69 which could hamper the operation
of the valve V and even cause the same to fail.
From the above, it is easily understood
that two new concepts have been incorporated in a
knife valve to provide an ideal valve for use, for
instance, in paper mills. First, the use of a
bonnet is now possible when solids are present in
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the liquid flowing through the knife valve due to
the above described bypass arrangement provided in
the bonnet. In this case, a positive torque induced
closure of the knife blade, such as with the
structure described before, is optional depending on
whether or not, for example, a bidirectional seal is
required.
Second, a high-pressure bidirectional
tight knife valve is provided by the positive torque
induced closure of the knife blade, as described
hereinbefore. In this latter case, a bonnet is
provided with or without a bypass, depending on
whether or not solids are present in the liquid
flowing through the knife valve.
The combination of the bonnet, the bypass
and the positive torque induced closure of the knife
blade results in a knife valve well adapted for use
in paper mill applications necessitating a high
pressure bidirectional seal.
It is also easily seen that various other
structures could be devised as equivalents to the
proposed illustrated bypass arrangement and positive
torque induced blade closure arrangement. For
example, a ramp could be defined directly onto the
valve body at the top of the valve opening to
deflect laterally the stem head and thus the upper
portion of the knife blade tightly against the valve
seat, with the stem head being laterally
displaceable with respect to the stem. In such a
case, the stem head could be fixedly secured to the
knife blade.
The above features result in a knife valve
having a long cycle life without any leakage, even
under high pressure bidirectional flow.
; Regarding the bypass feature of the valve,
it is noted that the present valve finds its
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principle use in installations where white water is
circulated through the pipes. White water normally
includes approximately 1% of solids, but it is noted
that the present valve has been tested for white
water containing 7 to 8% of solids. As the fluid
circulates through the pipes and the valve passage
14, it displaces in a whirl. The fluid can move up
the circular cavity 66 of the bonnet 24, whereby
without the passages 71 the stem 36 could become
jammed with solids within the stem guides 69. With
these passages 71, the fluid can enter the bonnet
whereby it becomes necessary to allow the bonnet 24
to be flushed in order to prevent a clogging of the
bonnet itself. For that purpose, the wide passages
86 and 87 provide a communication between the bonnet
24 and the valve opening or passage 14. There must
be provided a set of facing wide passages 86 and 87
on each side of the stem 36, as best seen in Figs.
5, 6, 9 and 10, in view of the whirling motion of
the fluid. Indeed, the swirling fluid will, asides
from entering the stem cavity 68, flow upwards in
one of the sets of facing passages 86 and 87. With
the provision of the annular bypass cavity 88, the
fluid in one side of the bonnet will flow to the
other side of the bonnet and be forced out thereof
through the other set of wide passages 86 and 87.
Tests have shown that, without the bypass
cavity 88, one side of the bonnet 24 becomes
completely clogged with solids due to the entering
of the pulp fiber fluid by way of the first set of
facing passages 86 and 87 into the bonnet 24 as a
result of the whirling motion of the fluid in the
pipes. With the present arrangement, the fluid can
then be flushed out of the bonnet 24 through the
other set of facing wide passages 86 and 87 which is
located on the other side of the stem 36.
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Accordingly, the combination of the wide passages 86
and 87, the bonnet 24 and the bypass 88 allow the
fluid to continuously flow through the valve V, with
the dimension of these elements being such as to
allow fluid to contain some solids. As the seat
face 12 and the soft seat 98 intercept the passages
86 above the valve passage 14 and as the blade 34 is
held tight against the soft seat 98 along its entire
periphery, it is easily understood that there is no
communication between the seat side of the valve V
and the bonnet 24 when the valve is closed.
Finally, it is noted that tests have been
conducted with knife valves V constructed in
accordance with the present specification and that
such knife valves have been tested in sizes of 6
inches, 10 inches, 12 inches, 18 inches and 24
inches. The tests have proven that the present
knife valve V provides a tight seal without
clogging. In white water use, ball valves have been
successfully used in white water operations,
although such ball valves can cost up to $70,000.00
for a 24-inch valve which also weighs approximately
8,000 pounds, thereby necessitating a complex
structure for mounting the same in a ceiling, or the
like. Also, the spacing between the pipes required
for such large size ball valves is considerable. A
corresponding 24 inch knife valve in accordance with
the present invention costs from $12,000.00 to
$15,000.00 and does not exceed 1,000 pounds in
weight. Furthermore, it is well known that standard
knife valves used with white water become jammed
approximatively every two weeks thereby resulting in
high costs especially due to down time. The present
knife valve used in white water applications in
paper mills have not yet failed, and thus caused
any downtime, in over a year. Therefore, tests have
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convincingly shown that the present knife valves are
functional and economical.
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