Pressure boost attachment for pilot valves

A fluid pressure boost attachment (18) is attached to a pilot valve (16) which senses the fluid pressure in a main flow line F. Upon restriction or blockage of fluid flow through inlet line (32) to pilot valve (16) the correct static fluid pressure is sensed in auxiliary fluid chamber (126) of boost attachment (18). Boost attachment (18) is actuated upon a predetermined pressure differential being reached between chambers (100) and (126) thereby to move actuator (120) and place intermediate fluid chamber (24) of pilot valve (16) in fluid communication with outlet fluid chamber (28) thereof.

BACKGROUND OF THE INVENTION 
This invention relates to a pilot valve for controlling a control valve in 
a main flow line, and more particularly to a fluid pressure boost 
attachment for the pilot valve. 
Heretofore, such as illustrated in U.S. Pat. No. 3,572,359 dated Mar. 23, 
1971, non-flowing pilot valves have been utilized to control a main valve 
in the main flow line for regulating a sensed or signal fluid pressure, 
either on the downstream side of the control valve or the upstream side of 
the control valve. The sensed fluid pressure being controlled is in fluid 
communication with a first fluid chamber in the pilot valve and in fluid 
communication with the flow line on one side of the control valve. A 
second fluid pressure chamber in the pilot valve is in fluid communication 
with the flow line on the other side of the control valve, and an 
intermediate fluid pressure chamber in the pilot valve is positioned 
between the first and second fluid pressure chambers. A spool valve member 
is movable between open and closed positions on valve seats separating the 
intermediate fluid chamber from the first and second fluid pressure 
chambers thereby controlling fluid flow between the chambers as desired 
under predetermined operating conditions. 
Pilot valves are normally of two basic types, those that are adapted for 
use as pressure reducing valves to sense or control the downstream fluid 
pressure, or those adapted for use as a back pressure valve to sense or 
control the upstream fluid pressure. Aforementioned U.S. Pat. No. 
3,572,359 shows embodiments for controlling or regulating both the 
upstream fluid pressure and the downstream fluid pressure. 
It is noted that the response of the pilot valve is in response to a change 
in the pressure being sensed or controlled, and if for some reason such as 
a clogged filter, the fluid pressure being sensed or controlled is blocked 
in the line to the pilot valve, the control valve is not sufficiently 
responsive as the fluid pressure being sensed is inaccurate, and the 
control valve therefore receives an inaccurate pressure signal. 
SUMMARY OF THE INVENTION 
The present invention is particularly directed to an auxiliary attachment 
for a pilot valve controlling a control valve in a main flow line and 
sensing the pressure to be controlled in the main flow line. The sensed 
fluid from the main flow line or a fluid source, such as a tank, is 
normally communicated through a fluid filter prior to entering the pilot 
valve. At times, the filter may become clogged and thereby restrict or 
block the flow of inlet fluid or fluid being sensed through the pilot 
valve. When this occurs, particularly for a so-called modulating pilot 
valve which is highly sensitive and controls the flow of fluid through the 
control valve within well defined predetermined pressure ranges, an 
ineffective pilot valve results. There may be a blockage or restriction of 
the inlet fluid or fluid being sensed to the pilot valve for other 
reasons, such as freezing or the like. The present invention is 
particularly directed to an override mechanism which overcomes or 
compensates for such problems. 
The auxiliary attachment of the present invention provides such an override 
mechanism which is attached to the pilot valve and includes a body having 
a diaphragm therein separating two auxiliary fluid pressure chambers, a 
lower auxiliary fluid pressure chamber in fluid communication with the 
main flow line upstream of the control valve, and the other or upper 
auxiliary fluid pressure chamber in fluid communication with the inlet 
fluid chamber in the pilot valve. When the inlet line to the pilot valve 
is not blocked or restricted, the fluid pressure in the inlet fluid 
chamber in the pilot valve is the same as the fluid pressure of the sensed 
fluid in the main flow line. Thus, the fluid pressure in the auxiliary 
fluid pressure chambers is the same or balanced, and the diaphragm is not 
exposed to any pressure differential or stressed. 
A plunger or piston is connected to the diaphragm and upon a blockage or 
restriction of inlet fluid to the pilot valve, a reduction of fluid 
pressure occurs in the upper auxiliary fluid pressure chamber in fluid 
communication with the inlet fluid chamber resulting in an upward movement 
of the diaphragm along with the plunger. Upon upward movement of the 
plunger, the plunger engages an adjacent end of the spool valve in the 
pilot valve and pushes the spool valve upwardly to unseat the spool valve 
and provide fluid pressure communication between the control valve and the 
downstream flow line. Thus, an effective override mechanism is provided 
which is utilized to effect a change in the fluid control pressure to the 
control valve only when there is a restriction or blockage of the sensed 
or controlled fluid pressure to the pilot valve. 
It is an object of the present invention to provide an auxiliary attachment 
for a pilot valve controlling a control valve in a main flow line which is 
effective only upon a restriction or blockage of fluid pressure from the 
main flow line to the inlet chamber of the pilot valve. 
It is a further object of the invention to provide such an auxiliary 
attachment for a pilot valve which is effective to unseat a valve member 
in the pilot valve to provide fluid communication between the dome of the 
control valve and the flow line downstream of the flow line upon such 
blockage of fluid pressure to the pilot valve and subsequent rise in tank 
pressure to a predetermined value above the pressure at which the blockage 
to the pilot valve occurred. 
An additional object of the present invention is to provide such an 
auxiliary attachment for a pilot valve in which a pair of auxiliary fluid 
pressure chambers are separated by a diaphragm and remain in a state of 
equilibrium or fluid balanced except when blockage of fluid occurs between 
the flow line and the pilot valve, at which time a pressure imbalance or 
differential occurs in the auxiliary chambers resulting in actuation of 
the auxiliary attachment and unseating of a spool valve member in the 
pilot valve. 
Other objects, features, and advantages of this invention will become more 
apparent after referring to the following specification and drawings.

Referring now to the drawings for a better understanding of this invention, 
and more particularly to FIGS. 1 and 2, a typical system in which the 
present invention is adapted for use is illustrated and comprises a main 
flow line indicated at F with a control valve C therein for controlling 
the flow through flow line F. The upstream end of flow line F is indicated 
at 10 and the downstream end of flow line F is indicated at 12. The dome 
of control valve C is indicated at 14 and a pressure responsive element, 
such as a diaphragm, is normally positioned in dome 14 for controlling the 
flow of fluid through control valve C as well known in the art. 
A typical pilot valve with which the present invention is used is shown 
generally at 16 and the auxiliary boost valve attachment comprising the 
present invention is shown generally at 18 attached to the lower end of 
pilot valve 16. Pilot valve 16 has an inlet fluid chamber 20 in fluid 
communication with a fluid inlet port 22, an intermediate fluid chamber 24 
in fluid communication with an intermediate fluid port 26, and an outlet 
fluid chamber 28 in fluid communication with an outlet port 30. An inlet 
line 32 is connected to the upstream end 10 of flow line F and provides 
fluid to fluid inlet 22 for inlet chamber 20. Branch inlet line 34 leading 
from line 32 provides inlet fluid to an inlet port 36 on auxiliary valve 
attachment 18. An intermediate flow line 38 leads from dome 14 to 
intermediate port 26 for intermediate fluid chamber 24. An outlet flow 
line 40 extends from the downstream end 12 of flow line F to outlet port 
30 for outlet chamber 28. A branch outlet line 42 extends to an outlet 
port or vent 44 for auxiliary valve attachment 18. 
If desired, branch inlet line 34 for auxiliary valve attachment 18 may be 
connected to a fluid tank such as through line 46, instead of being in 
direct fluid communication with upstream end 10 of flow line F as shown. 
Port 44 may also be vented to atmosphere through line 48, if desired, 
rather than being in direct fluid communication with downstream end 12 of 
flow line F. 
Pilot valve 16 includes a diaphragm 50 in upper body portion 51 and a 
piston member 52 secured to diaphragm 50 and urged downwardly by 
adjustable spring 54. Piston member 52 has a central bore 53 in fluid 
communication with inlet chamber 20 and extends downwardly within a 
central bore of a lower body portion 55. Received within an enlarged 
diameter bore portion 56 of bore 53 is a spool valve indicated generally 
at 58 having a pair of O-ring seals 60 and 62 thereabout for seating on 
respective seats 64 of piston 52 and fixed seat 66 of seat member 68. The 
upper end 69 of seat member 68 provides a stop for shoulder 70 on piston 
52 to limit the downward movement of piston 52. Seat member 68 has an 
externally threaded lower end 72 threaded within the lower internally 
threaded central bore 74 of body portion 55. 
In the position of pilot valve 16 shown in FIG. 2, O-ring seals 60 and 62 
are seated on respective seats 64 and 66, thereby blocking fluid 
communication between intermediate fluid chamber 24, inlet fluid chamber 
20, and outlet fluid chamber 28. When seal 60 is unseated, fluid 
communication is provided between intermediate fluid chamber 28 and inlet 
fluid chamber 20. When seal 62 is unseated, as in FIGS. 3 and 4, fluid 
communication is provided between intermediate fluid chamber 24 and outlet 
fluid chamber 28. Fluid pressure between pilot valve 16 and dome 14 of 
control valve C is controlled by the fluid communication of intermediate 
chamber 24 with fluid chamber 20 or outlet fluid chamber 28 under 
predetermined fluid pressure conditions thereby to provide a highly 
sensitive pilot valve 16. For further details of pilot valve 16 and its 
functioning, reference is made to copending application Ser. No. 774,809 
filed Sept. 11, 1985, the entire disclosure of which is incorporated by 
this reference. 
It is noted that spool valve 58 has a central bore 76 therethrough in fluid 
communication with central bore 53 of piston 52 and fluid inlet chamber 20 
at all times. Seat 68 has a central bore 78 therethrough in continuous 
fluid communication with bore 76 of spool valve 58 and thus is in direct 
fluid communication with fluid inlet chamber 20 at all times. 
Referring now to the auxiliary boost valve attachment 18 as shown in FIG. 4 
and forming the present invention, an upper body 82 and a lower body 83 
secured by threaded bolts 84 clamp a diaphragm 85 therebetween. Upper body 
82 has an extension 86 externally threaded at 87 and received within 
internally threaded opening 74 of pilot valve body portion 55. End 88 of 
extension 86 is in abutting contact with the adjacent lower 72 end of 
fixed seat member 68 and an O-ring 90 seals therebetween. Upper body 82 
has a central bore 92 therein and a restricted diameter bore portion 94 
defined within extension 86 and defining a shoulder 96. An enlarged 
diameter bore portion 98 forms an upper auxiliary fluid chamber 100 
therein and defines a shoulder 102. Auxiliary fluid chamber 100 is in 
direct fluid communication with inlet fluid chamber 20 of pilot valve 18 
at all times through piston bore 53, bore 76 of spool valve 58, central 
bore 78 of fixed seat member 68, restricted bore portion 94, and bore 92. 
Diaphragm 85 is clamped between a pair of annular plates 104 having 
internally threaded opening 106. A plunger member indicated generally at 
108 has an enlarged diameter lower head 110 with an O-ring 112 between 
head 110 and adjacent plate 104. An externally threaded intermediate 
section 114 of plunger 108 fits within annular plates 104 and a lock nut 
116 engages upper plate 104 to secure diaphragm 85 and plates 104 tightly 
on plunger 108. A small diameter end section 118 of plunger 108 has an 
actuator 120 thereon with an upper end surface 122 positioned adjacent end 
80 of spool valve 58 and adapted to contact spool valve 58 upon actuation 
thereof, as will be explained. A compression spring 124 is biased between 
shoulder 96 and intermediate section 114 of plunger 108 to urge plunger 
108 and diaphragm 85 lightly downwardly with a predetermined force. 
Plunger 108 forms a valve seat at 123 on the end of head 110, and a blind 
end bore 125 is provided in plunger 108 adjacent seat 123. 
Lower body 83 has an enlarged diameter bore 125 forming auxiliary fluid 
chamber 126 and a small diameter threaded bore 128 which receives an 
externally threaded plug forming an adjustable seat member generally 
indicated at 130. Seat member 130 has external screw threads 132 engaging 
internally threaded opening 128 for axial adjustment of seat member 130. A 
lock nut 134 is provided for securing seat member 130 at a predetermined 
position. The inner end portion 136 of adjustable seat member 130 is 
received within bore 128 and has flats 138 along its outer circumference 
for providing a flow of fluid thereat. An O-ring seal 140 about seat 
member 130 is adapted to engage relatively sharp edged seat 123 on plunger 
108 in the inoperable position of plunger 108 as shown in FIG. 2 to form a 
seal therebetween. 
When pilot valve 16 is functioning properly, auxiliary valve attachment 18 
is in a fluid balanced relation with the fluid pressure in auxiliary fluid 
chambers 100 and 126 being identical since auxiliary fluid chamber 100 is 
in direct fluid communication with fluid inlet chamber 20 of pilot valve 
16 and auxiliary fluid chamber 126 is in fluid communication with inlet 
line 10. In this position, there is no stress on diaphragm 85 and 
auxiliary valve attachment 18 is inoperable. Since there is no stress on 
diaphragm 85 and no sliding seals or other moving elements, auxiliary 
valve attachment 18 may be held in readiness for an extended period of 
time, such as several years, and yet will be fully operable if needed. 
In the event of a restriction or blockage of fluid flow through inlet line 
32 to pilot valve 16, fluid pressure in inlet fluid chamber 20 would 
either become static and cease to change or significantly lag any pressure 
changes at inlet side 10 of flow line F. However, the correct static fluid 
inlet pressure from line 34 would be in auxiliary fluid chamber 126 and 
such static pressure could be higher than the pressure in fluid chamber 20 
of pilot valve 16 and auxiliary chamber 100 of auxiliary valve attachment 
18. 
As an example, it is pointed out that the effective surface area of 
diaphragm 85 exposed to fluid pressure from chamber 126 is around 
ninety-two (92) percent of the effective surface area of diaphragm 85 
exposed to fluid pressure from auxiliary fluid chamber 100, and this area 
differential is the area circumscribed by O-ring seal 140. Thus, there is 
an eight (8) percent area differential between auxiliary fluid chambers 
100 and 126 acting on diaphragm 85 which along with the bias of spring 126 
results in a downward seating force against O-ring 140. Thus, the pressure 
differential between chambers 100 and 126 at which plunger 108 will be 
actuated may be predetermined by the size of O-ring 140 and the bias of 
spring 124. 
Upon an increase of pressure in chamber 126 to approximately eight (8) 
percent higher than the pressure trapped in chambers 20 and 100, and upon 
subsequent movement of diaphragm 85 and plunger 108 to the position shown 
in FIGS. 3 and 4, there is no area differential between chambers 100 and 
126 acting on diaphragm 85 as O-ring seal 140 is unseated and the area 
circumscribed by O-ring seal 140 is now exposed to fluid pressure from 
chamber 126. Adjustable seat member 130 has flats 138 which permit a 
restricted fluid flow within bore 125 from chamber 126 upon the initial 
unseating of O-ring seal 140. 
Upon a pressure differential between chambers 100 and 126 of around eight 
(8) percent, for example, a snap action of diaphragm 85 to the position of 
FIGS. 3 and 4 occurs, thereby moving plunger 108 and actuator 120 upwardly 
to engage the lower end 80 of valve spool 58 to unseat O-ring seal 62 from 
seat 66, thereby to place intermediate fluid chamber 24 in fluid 
communication with outlet fluid chamber 28. It is noted that upon the 
unseating of O-ring 62, a restricted flow of fluid is provided between 
intermediate fluid chamber 24 and inlet fluid chamber 20 by suitable flow 
restrictions between spool valve 58 and adjacent piston 52. A suitable 
visual indicator may be provided at a control panel to indicate the 
actuation of boost attachment 18 so that any necessary maintenance or 
repairs may be made. 
From the above, it is apparent that that pressure boost attachment 18 
provides an override mechanism which is utilized only when a restriction 
or blockage of fluid flow occurs to the fluid inlet chamber 20 of pilot 
valve 16. 
While preferred embodiments of the present invention have been illustrated 
in detail, it is apparent that modifications and adaptations of the 
preferred embodiments will occur to those skilled in the art. However, it 
is to be expressly understood that such modifications and adaptations are 
within the spirit and scope of the present invention as set forth in the 
following claims.