Gas-hydraulic pressure type actuator for pipeline valve

An actuator 4 for a valve 2 disposed in a gas pipe line 1 is driven directly by the gas pressure in the pipe line, which is tapped off and supplied to the appropriate end of the actuator cylinder via an electromagnetic spool valve 12 or 25. A hydraulic transfer circuit couples the chambers on the piston rod sides of the actuator cylinder, and includes flow control valves 17, 18 for regulating the actuator speed and an oil expansion tank. The latter may be sealed and a positive pressure established therein to facilitate the oil transfer. A hand pump 22 may also be provided to implement the oil transfer and drive the actuator piston from the piston rod side if the gas pressure is too low to power the actuator.

BACKGROUND OF THE INVENTION 
This invention relates to a gas-hydraulic pressure actuator for opening and 
closing a pipe line valve. 
Gas-hydraulic pressure type actuators are commonly used for opening and 
closing ball valves in gas pipe lines. With such actuators, the gas being 
transported through the pipe line is used as the power source, and the gas 
pressure, rather than acting directly on the actuator cylinder, is applied 
to the upper portion of an oil filled pressure vessel. This converts the 
gas pressure to a hydraulic pressure, which is then tapped off from the 
lower portion of the pressure vessel and drivingly applied to the actuator 
cylinder. Such conversion of gas pressure into hydraulic pressure is 
advantageous because: the actuator cylinder is lubricated by the working 
oil; it is easier to control the opening and closing speed of the valve 
with oil as compared with gas; and if the gas pressure drops too low to 
power the actuator the valve can be opened or closed by operating a 
hydraulic hand pump. 
A prior art actuator of this type is shown by way of example in FIG. 1, 
wherein reference numeral 1 designates a pipe line, 2 is a valve body, and 
3 is a valve stem. A lever 4a of an actuator 4 is keyed to the valve stem 
3, so as to open and close the valve in association with the stroke of the 
actuator piston. Gas outlet ports 2a and 2b in the upstream and downstream 
sides of the valve body are connected by pipes 5 and 6 to check valves 7 
and 8, respectively. Outlet pipes 9 and 10 from the check valves merge 
into a pipe 11, which leads to a port 12p of an electromagnetic valve 12. 
A port 12a of the valve is connected to a gas inlet port 15a in the upper 
portion of a pressure vessel 15 by a pipe 13, while a port 12b of the 
valve 12 is connected to a gas inlet port 16a in the upper portion of a 
pressure vessel 16 by a pipe 14. The pressure vessels 15 and 16 are filled 
with a quantity of working oil such that when the valve 2 assumes an 
opening of 45.degree., the liquid level is maintained in the vertical mid 
portions of the vessels. Connected to oil outlet ports 15b and 16b in the 
lower portions of the pressure vessels are flow control valves 17 and 18, 
respectively, whose outlets are connected by pipes 19 and 20 to ports 21a 
and 21b of a change-over valve 21, respectively. The change-over valve has 
ports 21c and 21d connected to ports 4c and 4d of the actuator cylinder, 
and ports 21t and 21p connected to suction and discharge ports 22t and 22p 
of a hand pump 22, respectively. 
In operation, some of the gas flowing through the pipe line 1 is released 
through whichever of the ports 2a or 2b is on the high pressure side, and 
arrives at the port 12p of the electromagnetic valve 12, irrespective of 
whether the valve 2 is open or closed. If the valve 12 is deenergized, the 
port 12p is blocked, while the ports 12a and 12b are open to the 
atmosphere, as shown in FIG. 1. If the solenoid 12Sa of the valve 12 is 
energized, the valve spool is shifted to the right as viewed in FIG. 1, 
thereby communicating the ports 12a and 12p with each other. This 
introduces gas through the pipe 13 to the pressure vessel 15, which 
forcibly discharges oil from the vessel. This oil passes through the flow 
control valve 17, pipe 19, valve 21, and the port 4d into the actuator 
cylinder 4, whereby the piston and piston rod 4b are urged to the left to 
open the valve 2. Simultaneously with such piston movement, the oil in the 
other side of the cylinder is discharged through the port 4c, valve 21, 
pipe 20 and flow control valve 18 into the pressure vessel 16. The flow 
rate of this oil is adjusted by the control valve 18, so that the speed of 
the actuator 4 in opening the valve 2 is thereby regulated. The upper 
portion of the pressure vessel 16 is vented to the atmosphere through the 
valve 12. After the valve 2 has been fully opened, the solenoid 12Sa is 
deenergized. Consequently, the valve spool resumes the position shown in 
FIG. 1, and the pressurized gas in vessel 15 is released through port 15a 
and valve 12 to the atmosphere. In a similar manner, if the solenoid 12Sb 
of the valve 12 is energized, the valve spool is shifted to the left and 
the actuator 4 will operate to close the valve 2. 
If the gas pressure in the pipe line 1 becomes too low to produce 
sufficient hydraulic pressure to open the valve 2, then the valve 21 is 
shifted to the left. Consequently, the suction port 22t of the hand pump 
22 becomes connected by way of ports 21t and 21a to the valve 17 below the 
pressure vessel 15. On the other hand, the discharge port 22p of the hand 
pump 22 is connected by way of ports 21p and 21d to the port 4d of the 
actuator cylinder. If, under these conditions, the hand pump 22 is 
operated, the valve 2 will be manually opened. In a similar manner, if the 
valve 21 is shifted to the right, the manual operation of the hand pump 22 
will close the valve 2. 
Such a prior art gas-hydraulic pressure type valve actuator imposes a 
number of system requirements. First, the pressure vessels 15 and 16 for 
converting the gas pressure into hydraulic pressure must be high pressure 
containers, and they must have a volume several times as large as the 
volume of oil displaced by one stroke of the actuator 4. Second, an 
increase in the size of the valve 2 greatly increases the cost of the 
actuator system. Third, since the pressure vessels 15 and 16 are normally 
vented to the atmosphere, a relatively large volume of gas is necessary to 
raise the pressure in the vessels to an operational level at the time of 
valve actuation, and such gas is subsequently lost when it is vented to 
the atmosphere. Stated otherwise, the volume of gas consumed or wasted 
during a valve actuation is several times the volume of the actuator 
cylinder. 
Actually, it is highly advantageous for the actuator to convert a gas 
pressure into a hydraulic pressure. The use of pressure vessels for 
effecting such a conversion, however, is accompanied by a number of 
drawbacks, as described above. 
SUMMARY OF THE INVENTION 
The present invention is accordingly directed to providing a gas-hydraulic 
pressure type valve actuator which utilizes the advantages of hydraulic 
pressure, but dispenses with the prior art pressure vessels, whereby the 
drawbacks attendant therewith are eliminated. 
Briefly, and in accordance with the present invention, an actuator for a 
gas pipe line valve is driven directly by the gas pressure in the pipe 
line, which is tapped off and supplied to the appropriate end of the 
actuator cylinder via an electromagnetic spool valve. A hydraulic transfer 
circuit couples the chambers on the piston rod sides of the actuator 
cylinder, and includes flow control valves for regulating the actuator 
speed and an oil expansion tank. The latter may be sealed and a positive 
pressure established therein to facilitate the oil transfer and avoid tank 
overflow and spillage problems. A hand pump may also be provided to 
implement the oil transfer and drive the actuator piston from the piston 
rod side if the gas pressure is too low to power the actuator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to a first embodiment of the present invention, as shown in 
FIG. 2, the components having the same function as those shown in FIG. 1 
are designated by the same reference numerals. The description will 
therefore be directed only to the differences from the prior art system 
shown in FIG. 1. The actuator of the present invention is essentially 
distinguished in construction from the prior art system in that; the 
outlet ports 12a and 12b of the electromagnetic valve 12 are directly 
connected to the ports 4d and 4c of the actuator cylinder, respectively; 
ports 4e, 4f are provided in the actuator cylinder on the piston rod sides 
thereof whereby the central or mid-portions of the cylinder function as 
separate pressure chambers; and a small capacity pressure head or 
expansion tank 24 is connected to the suction side of the hand pump 22. 
The change-over valve 23 is also different in spool construction and 
function from the valve 21 in FIG. 1. 
In operation, if the solenoid 12Sa of the electromagnetic valve 12 is 
energized, the line gas is introduced through port 12a directly into the 
actuator cylinder port 4d, thereby urging the piston and piston rod 4b to 
the left to open the valve 2. At the same time, the oil in the piston rod 
side of the right half of the cylinder is forced out through port 4e and 
passes, via pipe 19, flow control valve 17, communicating ports 23d and 
23c of the change-over valve 23, flow control valve 18 and pipe 20, into 
the left half of the cylinder through port 4f. This is a pure oil transfer 
flow, and the tank 24 allows for any thermal expansion or contraction of 
the oil, as well as for oil seepage or loss. The flow rate of the oil is 
regulated by the control valve 17, whereby the speed of operation of the 
valve is controlled. In a similar manner, if the solenoid 12Sb of the 
electromagnetic valve 12 is energized, the valve 2 will be moved to a 
closed position. 
If the pipe line pressure is too low to operate the valve actuator, the 
change-over valve 23 is switched to the right, whereby the discharge port 
22p of the hand pump 22 communicates with the port 4f of the actuator 
cylinder via communicating ports 23p, 23c, flow control valve 18 and pipe 
20. The port 4e of the actuator cylinder in turn communicates, via pipe 
19, flow control valve 17, and communicating ports 23d, 23t, with the 
suction port 22t of the hand pump. If the hand pump is operated under 
these conditions, the hydraulic pressure thus created in the left half, 
piston rod side of the actuator cylinder will open the valve 2. 
Conversely, if the change-over valve 23 is shifted to the left, then the 
operation of the hand pump will close the valve. Whenever the actuator 
piston reaches the end of its stroke after the opening or closing of the 
valve, the exposed portion of the cylinder wall will be lubricated with 
oil. 
Under certain conditions, dependent upon the gas pressure in the pipe line 
1 and the settings of the flow control valves 17, 18, some overflow or 
spillage from the tank 24 may be encountered if the valve is opened or 
closed too fast and a vacuum is created in one of the actuator cylinder 
halves. The embodiment of the present invention shown in FIG. 3 is 
designed to avoid this problem. 
Referring now to FIG. 3, the junction pipe 11 is connected to a port 25p of 
a three-way electromagnetic change-over valve 25. Pipes 26 and 27 connect 
the change-over valve 25 to the ports 4c and 4d of the actuator cylinder, 
respectively. Solenoids 28 and 29 switch the change-over valve from one 
position to another. A container 30 houses the change-over valve, and is 
constructed so that exhaust gases from the valve are discharged through an 
exhaust pipe 31 and a check valve 32 to the atmosphere. The flow control 
valves 17 and 18 are connected to the bottom of a sealed expansion tank 
37. The top of the tank is connected to an intake-exhaust valve 38 
comprising an exhaust valve 38a and an intake valve 38b. The 
intake-exhaust valve 38 is connected at its other end to the container 30 
for the change-over valve. 
In operation, if the solenoid 28 is energized the change-over valve spool 
is shifted to the right, and gas from the pipe line 1 flows through the 
communicated ports 25p and 25d, and the pipe 27 into the actuator cylinder 
through port 4d, thereby urging the actuator piston 48 and rod 4b to the 
left to open the valve 2. The speed of the actuator piston is controlled 
by the variable throttle of the speed control valve 17, which allows oil 
to escape from the cylinder chamber 40 into the expansion tank 37. The 
piston 47 discharges gas from the cylinder chamber 41, and at the same 
time sucks oil from the expansion tank 37 into the cylinder chamber 42. 
Where an open type expansion tank is used, as in the embodiment of FIG. 2, 
a vacuum may be created in the cylinder chamber 42. This, together with an 
increase in the resistance of the oil flow path from the tank to the 
chamber 42, may cause the tank to fill with the oil forced out of chamber 
40 and overflow. 
With the sealed expansion tank 37 used in FIG. 3, however, the oil in the 
cylinder chamber 40 creates a pressure in the tank 37, which speeds up and 
facilitates the suction of oil into the cylinder chamber 42, without any 
risk of overflow. If the exhaust valve 38a is set at a proper level, then 
if the seal of pistons 47 or 48 is lost and high pressure gas is thus 
introduced from the pipe line 1 into the tank 37 through the cylinder 
chambers 42 or 40, such gas will be vented through the exhaust valve 38a. 
This enables the economizing use of a relatively thin walled, low pressure 
tank 37. On the other hand, if the oil and gas in the upper portion of the 
tank 37 contracts due to a lowered ambient temperature, any vacuum created 
in the tank is relieved through the intake valve 38b. Further, since the 
intake and exhaust valve 38 is connected to the container 30, the 
provision and proper biasing or setting of the check valve 32 ensures the 
creation of a positive pressure in the tank 37, thus allowing the valve 2 
to be opened and closed at a relatively high speed. That is, the gas from 
the unpressurized end of the actuator cylinder is vented through pipe 26 
or 27 and valve 25 into the container 30, to thereby establish a positive 
pressure in the container under the control of check valve 32. This 
pressure is applied to the tank 37 through the intake valve 38b. In 
addition, since the tank 37 is sealed and thereby isolated from the 
surrounding atmosphere, contamination by dust and moisture is avoided. 
As is readily apparent, the energization of solenoid 29 shifts the 
change-over valve spool to the left, communicates ports 25p and 25c to 
pressurize chamber 41 and close the valve 2, while at the same time 
venting port 25d into the container 30.