Ball Valve

A ball valve disclosed herein is low cost and offers a fast and reliable valve operation. Furthermore, the actuating force the ball valve requires, when it is shut off, is small. The ball valve is capable of fine adjustment of the flow. The ball valve comprises a valve casing defining a flow path of a fluid, a valve seat disposed in the midway of the flow path, a valve element which is in engagement with the valve seat or out of engagement with the valve seat, to shut off the flow path or to regulate the flow rate in the flow path, a control rod inserted into the valve casing and movable upward and downward, and a connecting rod, one end of which is rotatably supported at the inner end of the control rod, and the other end of which is connected to the valve element. The valve element comprises a communication path which communicates with both the upstream side of the flow path and the downstream side of the flow path and an on-off means for opening or closing the communication path.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a ball valve disposed in the midway of a 
flow path, and, more particularly, to a ball valve which regulates a fluid 
flow and is used as a shut-off valve in both emergency state and normal 
operating state. 
2. Description of the Related Art 
A shut-off valve of ball valve type is conventionally well known. The ball 
valve, constructed of a ball-like valve and its valve seat, partitions a 
flow path into its upstream portion and its downstream portion of the flow 
path, and a path is drilled in the center of the ball-like valve, to which 
a control rod is linked. The control rod is rotated to allow the ball 
valve to shut off or adjust its flow rate. 
Also available is a globe valve in which a partition board is provided in 
parallel with a flow path to divide it into two. A valve seat is disposed 
on the partition board, and a ball-like valve is vertically pressed onto 
the seat by means of the thread portion of a control rod connected to the 
valve. 
The shut-off valves in the prior art, however, suffer the following 
problems. In the above-described ball valve, when the ball valve is 
shifted from its full-flow state in which the path of the valve is aligned 
with the flow path, to its partial-flow state in which the valve rotates 
to a position where a partial flow is established between the upstream and 
the downstream of the flow path, to a shut-off state in which the flow 
path is completely blocked, a fluid remains confined to the path in the 
valve and its relief portion. When the fluid is expanded by heat, a seal 
portion disposed around the control rod is damaged. 
A large torque is needed to rotate the control rod, since the valve is 
tightly sealed onto its seat. This presents a operational difficulty. In 
particular, in the shut-off state of the flow path, the degree of seal 
between the valve element and the valve seat is extremely large because 
the pressure of the fluid is exerted onto the valve element. Thus, the 
valve seat suffers a rapid wear rate. 
Foreign matter such as rust tends to be jammed between the flow path end of 
the valve element and the valve seat. Also, foreign matter deposited on 
the bottom of the relief portion has been a cause of jamming. 
The ball valve subjects the flow of the fluid to curved path, causing a 
large energy loss. 
In the globe valve, since the flow of the fluid is curved in a complex path 
in the valve seat portion, the loss of pressure is substantial. Thus, the 
number of shut-off valves in a piping system had to be properly 
controlled. Furthermore, since the control rod uses a screw mechanism, it 
takes time to complete a shut-off operation. The screw mechanism is 
definitely reliable, but presents a problem, particularly in an emergency 
situation. To shut off a high pressure fluid, a large force is directly 
exerted onto the control rod, and a large torque is required. The globe 
valve is complex in structure and costly to manufacture. 
SUMMARY OF THE INVENTION 
A first object of the present invention is to provide a ball valve which 
operates in a reliable and fast manner and which is low cost and free from 
the above-described problems of each valve type. 
A second object of the present invention is to provide a ball valve which 
needs a small actuating force to release the valve from its shut-off 
state, which is quick to recover back pressure, and which provides a fine 
tuning capability of fluid flow. 
To achieve above objects, the present invention comprises a valve casing 
defining a flow path, a valve seat disposed in the midway of the flow path 
inside the valve casing, a valve element which is in sealing engagement 
with the valve seat or out of engagement with the valve seat to completely 
shut off the flow path or to regulate the flow rate in the flow path, and 
operating means connected to the valve element for engaging the valve 
element with the valve seat or for disengaging the valve out of the valve 
seat, whereby the operating means supports the valve element in a 
displaceable manner in the direction of the flow of the fluid. 
According to an embodiment of the present invention, the operating means 
comprises an operating rod, and a connecting rod, one end of which is 
rotatably supported at the inner end of the operating rod and the other 
end of which is secured to the valve element. 
According to a preferred embodiment of the present invention, the valve 
element comprises a communication path that allows the upstream of the 
flow path to communicate with the downstream of the flow path, and an 
on-off means for opening and closing the communication path. 
According to a preferred embodiment of the present invention, the on-off 
means comprises a medium-size valve seat disposed in the midway of the 
communication path, and a medium-size valve element disposed at the other 
end of the connecting rod, for shutting or regulating the flow of the 
fluid through the communication path in coordination with the medium-size 
valve seat. 
Here in the context of this specification, the term medium-size valve 
element means the one relatively smaller than the already described valve 
element. The term medium-size is used in the same sense throughout this 
specification. 
In the above preferred embodiment, a medium-size communication path may be 
disposed to communicate the communication path that is open to the 
upstream of the flow path, with the communication path that is open to the 
downstream of the flow path. The preferred embodiment further comprises a 
small-size valve seat in the midway of the medium-size communication path 
and a small-size valve element which cooperates with the small-size valve 
seat to completely shut off the flow path or to regulate the flow rate in 
the flow path. The preferred embodiment functions as a multi-phase 
pressure regulation type between the upstream and the downstream of the 
flow path. The small-size valve element may be provided with urging means 
made of an elastic material. 
Here in the context of this specification, the term small-size valve 
element means the one relatively smaller than the medium-size valve 
element. The term small-size is used in the same sense throughout this 
specification. 
As described above, the ball valve comprises the valve seat disposed in the 
midway of the flow path, the valve element which cooperates with the valve 
seat to completely shut off the flow path or to regulate the flow of the 
fluid in the flow path, and operating means connected to the valve element 
for engaging the valve element with the valve seat or for disengaging the 
valve out of the valve seat, whereby the operating means supports the 
valve element both in a vertically movable manner and in a displaceable 
manner in the direction of the flow of the fluid. The valve element thus 
moves in agreement with the flow of the fluid, and no undue force is 
exerted on the valve element. Furthermore, the valve element is free from 
unstable movement such as vibrating in perpendicular to the direction of 
the fluid flow. In a fast operation in which back flow is about to take 
place because of a reversed pressure relationship between the upstream 
side and the downstream side of the flow path, the valve element moves to 
be in engagement with the valve seat and check the back flow. The ball 
valve is simple in structure and low cost. 
The inner end of the control rod is connected to one end of the rigid 
connecting rod in a manner that the connecting rod is rotated. The other 
end of the connecting rod is rigidly connected to the valve element. Even 
when the pressure on the upstream side is released, it is possible to 
block the fluid on the downstream by mechanically pressing beforehand the 
control rod against the valve seat on the downstream side. 
When the pressure on the downstream side get larger than the pressure on 
the upstream side and when a force exerted on the valve element overpowers 
the mechanical force exerted beforehand onto the control rod to press it 
against the downstream valve seat, the valve element is shifted onto the 
upstream valve seat to check a back flow. 
Since the valve element is provided with the communication path that is 
open to both the upstream and downstream of the flow path, and the on-off 
means for opening or closing the communication path, the ball valve can 
release the upstream pressure in cooperation with already-mentioned 
functions. The force required for release operation during shut-off is 
reduced. Since the on-off means is constructed of the medium-size valve 
seat disposed in the valve element and the medium-size valve element 
disposed on the other end of the connecting rod, the on-off means is 
simple in structure and offers a reliable operation. 
As already described, the ball valve comprises the medium-size 
communication path disposed in the medium-size valve element, the 
small-size valve seat disposed in the midway of the medium-size 
communication path, and the small-size valve element that cooperates with 
the small-size valve seat. The ball valve functions in a multi-phase 
pressure regulation fashion between the upstream and downstream of the 
flow path. Along with the already-described functions, the ball valve is 
able to perform pressure release in a multi-phase manner by activating 
sequentially first the small-size valve element, medium-size valve 
element, and then the normal valve element. 
Provided with the urging means made of spring and the like, the medium-size 
valve element permits fine movement and thus fine adjustment of flow rate. 
If an external force used to adjust the medium-size valve element is 
exerted for some time, the flow set can be maintained even after the 
external force is removed. 
A more complete understanding of the present invention can be obtained by 
reference to the following detailed description of the preferred 
embodiments thereof in connection with the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a ball valve 1 according to the present invention 
comprises a flow path 20 in a horizontal direction and a cylindrical valve 
casing 2 that defines a vertically extending hollow portion 24. The 
horizontal portion of the valve casing 2 receives sleeves 3, 3, and the 
top of the vertical portion of the casing 2 is fitted with a lid 4. Both 
sleeves 3, 3 constitute at their inner ends valve seats 6, 6'. A control 
rod 7 is inserted into the valve casing 2 via seals 17, 17. The bottom end 
8 of the control rod 7 has a socket portion 8a, which receives one end of 
a connecting rod 9. The connecting rod 9 is connected to the socket 
portion 8a with a pin 8b. The pin 8b has a threaded portion 8c, and a nut 
8d and a washer 8e are screwed around the threaded portion 8c of the pin 
8b to prevent the pin 8b from coming off. As shown in FIG. 2A, the other 
end 10 of the connecting rod 9 is a flange portion and rigidly attached to 
a ball-like valve element 5. Since the ball valve 1 according to the 
present invention employs the sleeves 3, 3, some degree of flexibility is 
allowed in determination of material selection and machining accuracy of 
the sleeves. A commercially available T-type fitting may be used for the 
casing 2, resulting in a low material cost. 
The ball-like valve element 5 may be constructed of rubber, resin, metal. 
The ball-like valve element 5 may be a metal ball lined with rubber or 
resin. The material of the ball valve element 5 is mutually different from 
that of the valve seat 6, 6'. Specifically, if the ball-like valve element 
is constructed of a rigid material such as metal, the valve seats 6, 6' 
that are engaged with the ball-like element are constructed of an elastic 
material. If the ball-like valve element is constructed of an elastic 
material, the valve seats 6, 6' are constructed of a rigid material. 
FIG. 3 shows another structure of the end portion 8 of the control rod 7, 
wherein the pin 8b at one end of the connecting rod 9 is movable within an 
elongated opening 8f to allow some degree of play. This structure 
increases even sealing of the valve element 5 circumferentially around the 
valve seats 6, 6'. 
In FIG. 1, the ball-like valve element 5 is connected to the control rod 7 
via the connecting rod 9 that is connected to the end 8 by the pin 8b as 
shown in FIG. 2 and FIG. 3. The ball-like valve element 5 is vertically 
moved as the control rod 7 is moved. The ball-like valve element 5 
together with the connecting rod 9 is also rotatably supported around the 
pin 8b so that the valve element 5 is displaceable in the direction of the 
flow path. The ball-like valve element is thus movable in the combined 
vertical and horizonal movement. In the event of an emergency requiring an 
immediate shut-off of the flow path, the control rod 7 is lowered to allow 
the valve element 5 to be subjected to dynamic pressure of the fluid 
flowing from the upstream side 22 to the downstream side 23, and the valve 
element 5 is put in sealing engagement with the valve seat 6 to shut off 
the flow path 20. One of both the valve element 5 and the valve seats 6 is 
rigid while the other of both is elastic and the connection structure 
shown in FIG.3 permits additionally some degree of freedom in motion of 
the valve element 5. These arrangements help ensure a complete shut-off of 
the flow path 20. Since the valve element 5 is allowed to move vertically 
and horizontally along the flow of fluid, the valve element 5 suffers 
practically no swing in perpendicular to the direction of the flow of 
fluid. Thus, the motion of the valve element 5 is stable. 
A rigid connecting rod 9 connects the valve element 5 to the control rod 7. 
When the control rod 7 is further lowered with the valve element 5 
shutting off the flow path 20, a couple is exerted on the pin 8b and on 
the lower edge of the valve seat 6 of the downstream side. In addition to 
the force of the pressure of fluid flow, the mechanical force via the 
control rod 7 is thus additionally exerted onto the valve element 5 in a 
manner that allows the valve element 5 to be further pressed against the 
valve seat 6. If the pressure on the upstream side 22 happens to drop 
below that on the downstream side 23 for some reason, the valve element 5 
stays engaged with the valve seat 6 continuously keeping shut off the flow 
path 20. 
Another situation may be contemplated where the valve element 5 keeps the 
flow path 20 shut off by means of the pressure of fluid only. In this 
case, when the pressure on the downstream side 23 exceeds the pressure on 
the upstream side the valve element 5 is disengaged from the upstream 
valve seat 6, shifted to the downstream valve seat 6', and engaged with 
the downstream valve seat 6' to check a back flow. This prevents an 
accidental situation. 
Besides the shut-off operation, the ball valve according to the present 
invention may be applied for regulating the flow rate of a fluid. As shown 
in FIG. 4, the control rod 7 is left lowered to a middle position rather 
than to a fully lowered position sufficient enough for the valve element 5 
to shut off the flow path 20. With the valve element 5 at the middle 
position, the valve element 5 is put into a partial engagement with the 
valve seat 6. The degree of engagement determines the flow rate of the 
fluid, and thus the flow rate is regulated. Since the streamline 21' of 
the fluid is formed along the spherical surface of the valve element 5, 
the streamline 21' is smooth as shown in FIG. 4. A low pressure-loss flow 
rate regulation is thus achieved. 
FIG. 5 shows another embodiment. Disposed in the valve element 5 is a 
communication path 11 which is open to both the upstream side 22 and the 
downstream side 23 of the flow path 20. The communication path 11 is made 
up of a communication path 11a that open to the upstream side 22 and a 
communication path 11b that is open to the downstream side 23. The 
communication path 11 has on-off means 12 between the communication path 
11a and the communication path 11b. The on-off means 12 in this embodiment 
is of a structure similar to conventional ball valves, and comprises a 
medium-size valve element 9a and a medium-size valve seat 5a with which 
the medium-size valve element 9a is engaged. The medium-size valve element 
9a is provided with a stopper 9b which prevents the connecting rod 9 from 
coming off from the valve element 5. The stopper 9b abuts the underside 
13a of a nut 13 that is screwed into the valve element 5. 
FIG. 6 shows another embodiment of a communication path and its on-off 
means disposed in the valve element of FIG. 5. In this embodiment, a 
medium-size valve element 9a and a medium-size valve seat 5a are of a 
structure similar to that of a sluice valve. Since the remainder of the 
structure remain unchanged from the embodiment shown in FIG. 5, identical 
or similar parts are designated with the same reference numerals, and 
their description is omitted. The on-off means is not limited to the ball 
valve and the sluice valve shown in FIG. 5 and FIG. 6, respectively. For 
example, on-off means similar to a cock, a needle valve or a plug valve 
may be an acceptable alternative. Alternatively, an on-off means 
constructed of an electrically controlled solenoid valve built in the 
valve element 5 will equally work. 
FIG. 7 shows still another embodiment. Disposed in the medium-size valve 
element 9a in FIG. 5 is a medium-size communication path 9e which 
communicates with a communication path 11a open to the upstream side and 
with a communication path 11b open to the downstream side. Disposed in the 
midway in the medium-sized path 9e are a small-size valve seat 9d and a 
small-size valve element 9c in order to perform pressure regulation 
between the upstream side 22 and the downstream side 23 of the flow path 
in a multi-phase manner. 
According to the ball valve 1 of the present invention, the inner bottom of 
the valve casing 2 is directly washed by the fluid flow, when the ball 
valve 1 is opened. Even in its closed state, the ball valve 1 allows its 
inner bottom portion to be in contact with the fluid of the upstream side. 
The ball valve 1 is thus free from stagnation of fluid, sedimentation and 
build-up on the inner bottom of the casing, which the conventional ball 
valve has suffered from. 
In a ball valve of the type according to the present invention, the problem 
is a large force that is required to put the valve element 5 out of 
disengagement with the valve seat 6 when the ball valve 1 is to be 
released after an emergency shut-off. For example, assume that a pressure 
of 10 kgf/cm.sup.2 is exerted on a valve seat of 10 cm inner diameter. 
This pressure is translated into a force of 785 kgf. This cannot be 
manually released. Since the ball valve 1 according to the present 
invention comprises the communication path 11 disposed inside the valve 
element 5 and the on-off means 12 for opening or closing the communication 
path 11, a relatively small force is sufficient enough to release the shut 
valve. In FIG. 5, by allowing the control rod 7 to disengage the 
medium-sized valve element 9a from the medium-sized valve seat 5a, the 
fluid flows from the upstream side 22 to the downstream side 23, the 
downstream pressure as a back pressure for the valve element rises, and 
the differential pressure between the upstream side 22 and the downstream 
side 23 lessens. As a result, the force required to release the shut valve 
is relatively small. Because of its relatively small diameter, the 
medium-sized valve element 9a is subjected to relatively small pressure of 
the fluid, and thus the control rod 7 is easily manually manipulated. 
In FIG. 6, the sluice valve replaces the ball valve of FIG. 5. The 
medium-sized valve element 9a and the medium-sized valve seat 5a are 
controlled to shut off or regulate the flow of the fluid, increasing the 
downstream pressure that is the back pressure of the valve element. The 
stopper 9b at one end 10 of the connecting rod 9 prevents the connecting 
rod 9 from coming off from the valve element. 
The on-off means shown in FIG. 5 and FIG. 6 are particularly effective if 
the flow is an incompressible liquid. In the incompressible fluid, a 
slight release of pressure is enough to recover the back pressure of the 
valve element. Furthermore, if the medium-sized valve element is urged by 
urging means made of elastic material such as spring, it may be easy to 
displace the medium-sized valve element in a small increment. Thus, fine 
adjustment of flow rate is possible. For example, the medium-sized valve 
element 9a is always urged toward the upstream side by a spring. The flow 
path is blocked when the medium-sized valve element 9a is pressed 
downward. When released, the medium-sized valve element 9a is raised, 
allowing a slight current to flow along the flow path. 
Although the present invention has been discussed in connection with the 
illustrated embodiments in detail, it will be understood that the present 
invention is not limited to the above embodiments and that various 
modifications and changes are made without departing from the scope and 
spirit of the present invention.