Note: Descriptions are shown in the official language in which they were submitted.
~107Z6S
The present invention relates generally to
pipeline fittings and has particular reference to gate
valves adapted to shut off the flow of liquid in pipelines,
made use of in diverse fields of industry. such as mining,
construction, chemical, petroleum production, and the like.
The invention can find most utility when applied
for pipelines laid in underground coal winning by the
hydraulic method.
A large number of diverse types of gate valves
are known for use currently which comprise substantially
a housing hermetically joined with pipeline~, and a
closing member translationally traversable in between
the sealing elements of the housing.
However, despite a great diversity of gate valves
now in use the problem how to prolong their service life
is yet far from being completely solved, especially when
the gate valves are used to shut off the flow of liquids
containing solid impurities, as the closing members and
their sealing elements are liable to destruct within a
short period of time. This is due largely to the fact
that when the pipelines are shut off or intercommunicated,
adverse conditions for the closing members and sealing
elements are liable to arise, consisting in that a passageway
is established when the pipelines are communicated to each
other or shut off, said pa~sageway being confirmed within
the bottom end of the closing member, the gate valve housing
and the sealing elements and featuring the same cross-
sectional area at the entrance and exit thereof. We have
3~ been successful in finding out thàt the flow of liquid
2 ~
13 .
1107265
along such a passageway d~fines a void space situated
beneath the closing member close to the entrance to the
passageway, said void space considerably choking the
free passage area and, consequently, reducing the
hydrodynamic pressure in the flow, thus providing the
conditions for the onset of cavitation. Before leaving
the passageway the flow of liquid expands, the hydrodynamic
pressure rises and the cavities are broken, all this
leading to rapid failure of both the closing member and
the sealing elements.
It is an essential object of the present
invention to provide a gate valve, wherein favourable
conditions would be established for operation of its
closing member and for longer service life thereof.
It is another object of the present invention
to reduce the mass and overall size of the gate valve.
In keeping with said and other objects in a
gate valve to shut off the flow of liquid in pipelines.
a gate valve comprising, a valve housing defining a flow
path therethrough having an inlet and an outlet to allow
flow of a liquid therebetween, a gate valve operable to
close and open the valve and disposed to extend across said
flow path substantially normal to the flow of liquid
therethrough, said gate valve having a tapered lower edge
along an entire lower portion of a major side face of
the gate, said gate decreasing in cross section toward
said lower edge and in a direction toward the direction
of flow of said liquid.
~Such a constructional arrangement of the closing
device makes it possible to gradually compress the flow
: B _ 3 _
, ~ ~, . .
7Z65
of liquid thereunder towards the direction of its passing
and thereby rule out the onset of conditions fraught
with cavitation and bring the latter outside the closing
member towards the direction of the flow of liquid. As
a result, favourable conditions are provided for operation
of the closing member and sealing elements, whereby the
gate valve service life is many times extended. Furthermore,
this renders it possible to reduce the mass of the closing
member and of the actuator imparting translational motion
thereto.
In what follows the invention is characterized
in that provision is made on the end of the closing member
for a projection located on the side of the bevelled
edge thereof and adapted, when in either of its extreme
positions, to
B
1107265
contact with the sealing element which is situated in the
housing at the end of the liquid flow. This is instrumental
in keeping the sealing elements against being dislodged by
the flow of liquid and doing away with their being fixed
rigidly in position in the valve housing, a feature that
simplifies much the gate valve construction.
It is expedient that the sealing elements be so
fitted in the housing as to be forced against the closing
member through the agency of elastic rings interposed
between the housing and the sealing element, whereby a
required contact pressure is developed at the place of
sealing in cases where the pressure of the flow of liquid
is below normal. In addition, such an arrangement of the
sealing elements provides for a complete hermetic tightness
when shutting off the pipelines even in case of foreign
object penetration in between the sealing element and the
closing member.
Thus, the gate valve proposed herein is simple
in construction, reliable in operation and features long
service life.
In what follows the present invention is illustra-
ted in a detailed disclosure of a specific embodiment of
the gate valve to shut off the flow of liquid in pipelines
substantially as represented in the accompanying drawings,
wherein: -
Fig. 1 is a general view, partly in longitudinal
section, of the gate valve, according to the invention,
Fig. 2 is a front view showing the position of
the closing member at the instance where communication
is established between the pipelines as seen along the
1~)7Z65
direction of the flow of liquid, and
Fig. 3 is a section taken along the line III-III
in Fig. 2.
Now referring to the accompanying drawings, the
gate valve to shut off the flow of liquid i~ built in to
pipelines 1 and 2 (Fig. 1) and comprises a housing 3 and
a closing member or gate 4.
The housing 3 is made as a three-way fitting
composed of branches 5, 6 and 7, the diameters of the
branches 5 and 6 approximating those of the pipes 1 and
2, respectively. The branches 5 and 6 of the housing are
communicated with the pipelines 1 and 2 through a quick-
to-release coupling 8 of any heretofore known construction
providing for a hermetically sealed joint.
The housing 3 accommodates annular sealing
elements 9 and 10 between which the closing member 4 lS
interposed with a possibility of translationally traversing
normal to the direction of the flow of liquid. The closing
member 4 is made as a slide gate, though it may also be
made as one-piece structure or be composed of a number of
oblong components (not shown in Figs. 1 through 3).
The closing member 4 with its top end is connected
~by any of the heretofore known means) to a telescopic rod
11 of an actuator 12 in whose capacity use may be made of
any hitherto known driving means suitable for imparting
translational motion to the closing member, the actuator
consists of a nut 13 and a handwheel 14 in the given
particular case.
A bevelled edge 15 is provided on the bottom end
of the closing member 4 throughout its entire width as it is
shown in Figs. 2 and 3, the abovesaid bevelled edge is so
1107265
made that when the pipeline 1 gets communicated with the
pipeline 2, a passageway 16 is established between the
bevelled edge 15 of the closing member bottom end, the
sealing elements 9 and 10 and the housing 3, said passageway
growing narrow towards the direction of the flow of liquid
as indicated by the arrowhead A in Figs. 1 and 3. It is
due to the provision of said bevelled edge 15 that a
lateral surface 17 of the closing member 4 facing the
direction of the flow of liquid is of shorter length than
an opposite lateral surface 18 thereof.
Such a tapered shape of the passageway 16 is
retained throughout the entire period of translational
motion of the closing member as the pipelines 1 and 2
are either communicated or shut off; in addition the flow
area of said passageway 16 at its entrance exceeds that
at the exit thereof.
A projection 19 ~Figs. 1 and 2) is provided on
; the end of the closing member 4 on the side of its
bevelled edge 15, said projection being adapted to contact
the sealing element 9 located in the housing on the side
facing the direction of the flow of liquid, with the closing
member 4 assuming either of its extreme positions.
The lateral surfaces of the projection 19 easily
turn, as ,shown in Fig. 2, into the surface forming the
bevelled edge 15.
; The sealing elements 9 (Fig. 1) and 10 are so
mounted in the housing 3 as to be forced against the
closing member 4 through the agency of elastic rings 20
made in any presently known materiàl fit for long-term
operation in the liquid handled by the pipelines 1 and 2.
1107265
The sealing elements 9 and 10 has annular
recesses 21 for the elastic rings 20 to accommodate; in
order to prevent the rings 20 and the sealing elements 9,
10 against axial displacement away from the closing member
4, annular ridges 22 are provided in the housing 3 on the
inner surface thereof, for the elastic rings 20 and the
sealing elements 9, 10 to bear against.
An access hole 23 is made in the housing 3 on
its wall facing the valve actuator 12, said hole being
adapted for installing the sealing elements 9, 10 and
elastic rings 20 into the housing or withdrawing these
components therefrom without dismantling the valve housing
from the pipelines.
The herein-proposed gate valve operates as follows.
In order to establish communication between the
pipelines 1 and 2 one must rotate the gate valve handwheel
14 along with the nut 13, with th0 result that the rod 11
along with closing member 4 moves upward with respect to
the sealing rings 9 and 10 forced against the closing
member 4 by virtue of elastic deformation of the rings 20.
While the closing member 4 is being moved the
passageway 16 (Fig. 3) is formed in between the sealing
rings 9 and 10, the housing 3 and the bevelled edge 15 of
the bottom edge of the closing member 4, said passageway
getting narrower towards the direction of the flow of liquid.
Thus, provision of the bevelled edge 15 and the tapered
passageway 16 enable a gradual compression of the flow of
liquid in the passageway 16 throughout the width thereof,
whereby a minimized flow area and minimized hydrodynamic
pressure therein are ensured at the exit of the passageway
16. Moreover, formation of cavitation voids occurs outside
~1~7Z6S
the closing member 4, this being due to the fact that the
flow of liquid is widely expanded just upon leaving the
passageway 16, accompanied by raising the hydrodynamic
pressure therein and destruction of cavitation voids.
Thus, the bevelled edge on the bottom end of the closing
member and formation of the passageway 16 enable one to
dislodge cavitation off the closing member into the
downstream flow of liquid.
When the closing member 4 is lifted into the
topmost position the projection 19 restructs the travel
of the sealing element 9 caused by elastic deformation
of the ring 20 and hydrodynamic effect produced by the
flow of liquid.
Once the flow of liquid in the pipelines 1 and
2 has been shut off the closing member 4 moves down to
assume its bottommost position; thus, the flow of liquid
gets shut off first at the end of the sealing element
10, then at the end of the sealing element 10, this being
due to the provision of the bevelled edge 15 and owing to
the different length of the lateral surfaces 17 and 18
of the closing member 4~ Thus, any possibility of the
onset of cavitation is obviated in this case as well,
and the process of cavitation is brought outside the
closing member towards the direction of the flow of liquid.
_ g _
