Bi-directional flow control system

For use in a fluid system, which includes a control valve or the like having one port to which the higher of two pressures is delivered and another port from which fluid flows to the lower of two pressures, a four-way shuttle valve with high and low pressure ducts. Pressure level passages connected from the two pressure zones, are each connected by lateral transfer passages to both the high and low pressure ducts. One-way check valves in each of the four lateral passages enables flow only to the high pressure port and from the low pressure port. In the event of pressure reversal, the check valves will shift so that flow is always from the high pressure line to the high pressure duct of the shuttle valve.

BACKGROUND OF THE INVENTION 
Generally, a pilot or control valve in a pressure control system with a 
main shut-off valve has its inlet port connected to one side of the main 
valve and an exhaust line connected to the other side. For example, with a 
pilot valve controlling the jacket pressure of a main valve, the inlet 
port of the pilot valve is connected to the upstream side in the normal 
direction of flow and a dumping valve for evacuating the jacket is 
connected to the normal downstream side. However, in the event of pressure 
reversal this system becomes inoperative and, where pressure reversal is 
occasioned, bi-directional control requires the provision of two parallel 
control valves, manually switching devices or the like. 
OBJECTS OF THE INVENTION 
It is an object of this invention to provide a device which will 
automatically switch over the control lines of a control valve, regulator 
or the like upon a pressure reversal in the pipeline. 
It is a further object of this invention to provide a shuttle valve device 
which will enable continued operation of a control valve despite pressure 
reversals in the pipeline. 
Other objects and advantages of this invention will become apparent from 
the description to follow, particularly when read in conjunction with the 
accompanying drawing. 
SUMMARY OF THE INVENTION 
In carrying out this invention, I provide a valve body having generally 
parallel high and low pressure ducts extending therein intermediate the 
ends thereof. A pair of pipeline communication passages, which are 
connected to opposite sides of the main shut-off valve, extend into the 
shuttle valve body on opposite sides of, and transverse to, the high and 
low pressure ducts. These are then connected separately to the high and 
low pressure ducts by means of lateral passages. A one-way check valve in 
each of those lateral passages that are connected to the high pressure 
duct, enables flow only from the pipeline communication passages to the 
high pressure duct. Similarly a one-way check valve in each of those 
lateral passages that are connected to the low pressure duct, enables flow 
only from the low pressure duct to the pipeline communication passages. 
Hence, whatever the direction of flow, the shuttle valves will enable flow 
from the high pressure side of the main valve to the high pressure duct 
and from the low pressure duct to the low pressure side. The high pressure 
duct is connected to the inlet of a pilot valve which controls the jacket 
pressure of a main shut-off valve, and the low pressure duct is connected 
to the dumping port of the pilot valve so that when the jacket is 
evacuated, it automatically dumps to the low pressure side of the main 
valve.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now to FIG. 1 with greater particularity, the shuttle valve 10 of 
this invention may be operated in conjunction with a pilot valve 12 that 
controls the pressure in the jacket 14 of a main valve of the type wherein 
the valve is opened when the higher line pressure overcomes pressure in 
the control chamber 14. For example, in the main valve 16 shown a flexible 
tube 18 is stretched around a dam or barrier 20 under slight hoop tension, 
which, augmented by the pressure in the jacket 14 opposes upstream 
pressure acting against it through a series of slots 22 or 24, depending 
upon the direction of flow, as indicated by the arrows "Normal" and 
"Reverse". The slots 22 and 24 are provided in a core or cage 26 which is 
carried in the valve body 28. 
When the control pressure in the jacket 14 is so overcome, the tube 
stretches outward and flow occurs from the higher pressure side 30 or 32 
through the slots 22 or 24, around the barrier 20 and out the other slots 
to the then downstream side. 
In the pilot valve 12, upstream pressure is delivered through line 34 to 
the intake port 36, from which it is delivered through orifice 38 (the 
size of which may be varied by turning the plug 40) to load line 42 to 
load the jacket 14. Flow pressure fluid being controlled is fed to sensing 
port 44 where it acts against a diaphragm 46 opposed by an adjustable 
spring 48. When the spring 48 overcomes the pressure at the sensing duct 
port 44 a valve plug 50 is moved away from a port 52 to allow the chamber 
14 to be dumped back through line 42 and out through dumping port 54 to a 
low pressure line 56. 
In conventional operation, the intake port 36 is connected by line 58 from 
a port 60 in the usual upstream side of the valve 16 and the dumping port 
54 is connected by line 62 from a port 64 in the downstream side of the 
valve. However, in a system wherein flow reversal is occasioned, the pilot 
valve 12 is rendered inoperative. Therefore, the shuttle valve 10 of this 
invention is interposed in the system. 
The shuttle valve 10 includes a valve body 66 in which are bored high and 
low pressure ducts 68 and 70. As shown, the high pressure duct 68 is 
connected by line 34 to the intake port 36 of the pilot valve and the low 
pressure duct 70 is connected by line 56 from the dumping port 54 of the 
pilot valve. Since low pressure duct 70 carries the lower of two pressures 
in the system, i.e. the downstream pressure at any given moment, the 
sensing port 44 may also be connected to line 56 by sensing line 71, for 
control of downstream pressure. Pipeline communication or pressure level 
passages 72 and 76 are brought into communication with the opposite sides 
of the main valve 16 by connection through lines 58 and 62. The pipeline 
communication passages 72 and 76 extend into the valve body 66 on opposite 
sides of, and transverse to, the high and low pressure ducts 68 and 70. 
High pressure transfer lines 78 and 80 extend outward in opposite 
directions from high pressure duct 68 to communicate with the pipeline 
pressure level lines 72 and 76. Low pressure transfer lines 82 and 84 
extend outward from the low pressure duct 70 to the pipeline pressure 
level passages 72 and 76. One-way check valves 86 and 88 are interposed in 
the high pressure transfer lines 78 and 80 to enable flow only from the 
pipeline pressure level passages 72 and 76 to the high pressure duct 68. 
One-way check valves 90 and 92 in the low pressure transfer lines enable 
flow only from the low pressure duct 70 to the pipeline pressure passages 
72 and 76. 
In operation, assuming that flow passage 30 represents the high pressure 
side of the valve 16, the check valve 86 will be opened to allow flow of 
high pressure fluid to the high pressure duct 68, and through the line 34 
to the intake port of the pilot valve 12 to load the control chamber 14 of 
the main valve 16. In the meantime, the higher pressure in pipeline 
pressure level passage 72 holds the check valves, 88 and 90 firmly against 
their seats to prevent flow from the lower pressure passage line 76 to the 
high pressure duct 68. Therefore, flow from the low pressure duct 70 can 
only be through check valve 92 to the pipeline pressure level line 62. In 
actual operation a state of balance is reached wherein the dumping valve 
52 is partially open to permit a certain amount of dumping at port 54 
continuously for continuous flow through the valve 16. 
In the event that flow in the pipeline (not shown) reverses and flow 
passage 32 becomes the high pressure side, the check valve 88 is 
immediately unseated to enable flow from line pressure passage 76 to the 
high pressure duct 68, biasing check valves 86 and 92 firmly against their 
seats so that low pressure flow from the low pressure duct 70 is possible 
only through check valve 90 to line pressure passage 72. 
The operation is illustrated schematically in FIG. 2. Assuming that 
pressure in line 30 is the higher of two pressures, it will unseat check 
valve 86 and seat check valves 90 and 88 so that flow from line 30 is out 
through high pressure duct 68 and flow from low pressure duct 70 enabled 
only through check valve 92 to line 32. Should pressure reverse, and flow 
passage 32 become the higher, it will unseat check valve 88 and seat check 
valves 92 and 86 so that flow from line 32 goes out through high pressure 
duct 68. Flow from low pressure duct 70 is enabled only through check 
valve 90 to flow passage 30. 
While this invention has been described in conjunction with a preferred 
embodiment thereof, it is obvious that modifications and changes therein 
may be made by those skilled in the art to which it pertains, without 
departing from the spirit and scope of this invention, as defined by the 
claims appended hereto.