Note: Descriptions are shown in the official language in which they were submitted.
6~
Th~ present invention rclat~s to gate valves suitabl~
.or controlling the flow of abrasive slurries such as tailings
from mining operations and the like.~ More particularly the in-
vention relates to a knife gate valve having no gate packing box
or stem packing box.
A knife gate valve having a thin bladed knife gate with
a sharp edge which is forced between two seals made o~ resilient
material is known. Examples of these types of valves are shown in
Canadian Patent 598,397 and 614,768 to Williams and U.S. Patent -~
3,333,816 to Williams et al. All of the valves shown in these
patents, however, include a gate or stem packing box to prevent
leakage from the valve. These packing boxes cause the valve to
become bulky and complex.
Clarkson in Canadian Patent 1,017,315 discloses a pack-
lngless knife gate valve, but which has a special insert piece hav-
ing a larger internal diameter than the normal flow passage way and
a special liner to fit therein.
The present invention provides a packingless gate valve
which has a pair of valve body housings which may have standard l`
pipe flange fittings, Victaulic (trade mark) pipe fittings or other
types of fittings for standard pipe connections. The pair of valve
bodies together need not be so wide as the valve shown in the
Clarkson patent. Furthermore, the end connections of both valve
bodies are standard pipe connections unlike the valve shown in the
Clnrkson patent.
Packingless valves do from time to time leak and the
present valve has a space between the two flange body housings
mnintained by spacer strips on each side of the flowpassa~e and any
leakage that does occur is allowed to drain from this space and does
not cause a build up of particles which could prevent operation of
the valve. The valve body housings each have a flange surface which
is substantially perpendicular to the flow passage, the flange
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~surfaces on the pair of housings oppose each other. Each ~lange
surface has a slot and the slo~s in the opposing ~lang~ sur~ac~s
are aligned and extend around the ~low passage with a seal ring
fitting in ~ach slot. lrhe seal ring has a sealing surface which
mates with the sealing surface of the other seal ring and a knife
blade is forced betwaen these two sealing surfaces which part to
allow the knife blade to close the flow passage in the valve.
The present invention provides a packingless gate valve
comprising a pair of valve body housings, each housing having a
flow passage of substantially the same diameter therethrough, each
housing having a connector flange with a flange surface perpendic-
ular to the flow passage, the ~lange surface on one housing facing
the flange surface on the other housing, a slot in each flange
surface e~tending around the flow passage, the slot in one flange
surface aligned with the slot in the other flange surface, a space
between the flange surfaces having a guiding means on each side,
means for connecting the two flanges together with the space in
between, a seal ring in each slot with a sealing surface of one
ring touching a sealing surface of the other ring in the space
between the flange surfaces and a knife gate having a sharp edge
disposed between the sealing surfaces of the seal rings adapted
~o move backwards and forwards in the space within the guiding
means.
In other embodiments of the present invention the gate
vnlve has seal rings which each have a circular backing ring with
rasillent material attached thereto, the backing riDg being re-
placeable wlthin the slot. In another embodiment, the sealing
surface of each seal ring is radiused and in another embodiment
the sealing surface of each seal ring has chamfered edges. In a
still further embodiment, spacer strips are located at each side
of the flow passage outboard of the slot in the space between the
flange surfaces, the spacers forming the guiding means for the
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knife gate.
In drawings which illustrate embodiments oi th~ inv~ntion
Fig. 1 is a cross sectional elevation through one embod-
iment of the knife gate valv~ of the present invention.
Fig. 2 iS a cross ~ectional view taken at line 2-2 of
Fig. 1. ;
Fig. 3 is an end view of one embodiment of a valve
according to the present invention showing the operator mechanism.
Referring now to th~ drawings, Fig. 1 and 2 show one
embodiment of a knife gate valve according to the present invention
wherein a first valve body housing 10 is connected to second valve
body housing 11~ Both valve body housings 10 and 11 are substan-
tially the same, they have a standard pipe flange 12 at one end
with bolt holes 13 for connection to a pipe flange ~or a conduit
or other connector. It will be appreciated that the standard pipe
~lange does not necessarily form part of this valve, the end con-
nection may be a Victaulic type pips connection or olle end could
be one type of end connection and the other end a di~ferent typs o~
end connection. The inside surfaces o~ the valve body housings 10
and 11 have connector ~langes 14 which both have flange surfaces
15 ~acing each other and substantially perpendicular to a ~low
passage 16 in th~ valve body housings 10 and 11. The flow passage
16 in both body housings is sub~tant1ally the same cliameter. Each
connector ~lange 14 is substantially rectangular in shape, and has
a row o~ holes 17 in each flange 14 at opposite sides of the flow
passage 16, and two spacer strlps 18 having holes therein to match
the holes in the ~langes 14 are placed one on each side o~ ths flow
passage 16 between the two ~langes 14 so that when the two flanges -~
14 are bolted together by bolts 19 through bolt holes 17 the spacer
strips 18 provide a space 20 between t~e two flange surfa¢es 15~ Thus
the spacer strips l8 provide guiding means for the knife gate valve. -~
A slot 21 having a rectangular cross se~tion is located in each
~lange surface lS around the flow passage 16 but within the area o~
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~he flang~ sur-~ac~ no-t cover~d by the spacor strip lB. The slot
21 axtends in a circle around the flow passage, and is aligned
with the slot 21 in the opposite or adjacent valve body housing.
A seal ring 22 is located in each slot 21, the seal ring having a
sealing sur~ace 23 so that the two seal rings 22 mate and seal at
their sealing surfaces 23 in the space 20 between the ~lange
surfaces 15 to prev~nt the liquid in tha valve escaping.
As shown in the drawings, the seal ring 22 has a circular
metal bac~ing ring 24 with a resilient material attached thereto.
The resilient material forms the sealing surface 23 of the seal
ring 21, the metal backing ring, preferably steel, acts as a rigid ~
support to retain the seal ring 22 within the slot 21. A rectan- -
gular knii'e blade 25 having a tapered sharp edge 26 is supported
~rom a valve stem 27 and passes between the sealing surfaces 23 of
the seal rings 22. The knife blade 25 passes between the spacer
strips 18 on each side of the flanges 14 which act as guidas. As
the knife blade 25 slowly moves downwards in the gap 20, the seal-
ing surfaces 23 on the seal rings 22 are parted, but seal to bo-th
sides of the knife blade 25. The knife blade may be located at
any position within the flow passage 16 and in this manner9 the
valve can be partially closed. When the knife blade 25 passes to
~he bottom of the valve body housing, the valve is closed complete-
ly. '
The sealing surface 23 of each seal ring 22 may be sub-
stantially flat as shown alternatively it may be radiused or have
ch~mfered edges to provide easier parting when the sharp edge 26
o~ the Icnife gate 25 passes between the seal rings 22. In a pre-
ferred embodiment the seal ring is formed from a Linatex (reg-
istered trade mark) rubber material adhesively aittached to a steel
ring. The seal ring 22 may be formed of a flexible material having
a hardness of 35 to 40 Shore A Durometer. The backing ring may be
a harder rubber or plastic material sufficient to support the
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flexible portion which has th~ sealing sur~ace 23 thereon when
the knife gate 25 is forced between the sealing sur~aces. In
one embodiment the knife gate is between 1/8 and 1/~ inch thick.
Fig. 3 shows an operating mechanism for the knife gate
valve illustrated in Fig. 1 and 2 wherein the stem 27 connected
to the knife blade 25 is a threaded spindle and extends upwards
through a housing 30 which has a spindle nut 31 connected to a
hand wheel 32. The housing 30 is mounted on a frame 33 with legs
3~ supported from the top side bolts 19 on each side of the valve
body. Rotating the hand wheel 32 causes the spindle nut to rotate
and the stem 27 rise upwards or downwards depending on the direc-
tions of rotation, and thus move the knife blade 25. In a pre-
ferred embodiment an indicator may be provided showing the exact
location of the knife blade 25 within the flow passage of the
valve.
In another embodiment the spacer strips 18 between the
two ~langes 1~ are omitted, and each flange has a shoulder and
raised surface which rest adjacent to each other thus leaving the
space 20 between the flangas. The space 20 is of sufficient width
to allow passage of the knife gate and the shoulders on the flanges
at each side provide guides for the kni~e blade. ;
It will be understood by those skilled in the art that
various changes may be made to this particular valve, for example
an abrasive lining may be added in both halves of the valve body
housings to avoid wear of the metal in the flow passage. The
~eal ring 22 may be replaced by merely removing the bolts 19
between the two connector flanges 1~, parting the flanges, removing
-~he old seal rings 22 and inserting new seal rings into the slots
21. Other changes may be made to the knife gate valve of the
present invention without departing from the scope of the present
invention which is only limited by the claims.
