Pilot valve mechanism for high or low pressure cut-off control

An improved pilot valve mechanism for controlling the flow of a pressure medium responsive to predetermined variations in a pressurized system. The pilot valve mechanism is constructed in such manner that a plurality of pilot valves may be connected in an assembly and may be operative to shut down operation of a flow system responsive to sensing of pressures that are above or below a predetermined range of operating pressure. Each of the valves may include a shuttle valve mechanism capable of interrupting fluid communication between the inlet and outlet of the pilot valve mechanism or between the outlet and vent thereof, depending upon the position of a shuttle valve actuating piston that is proportionally movable responsive to variations in the pressure that is sensed by the pilot valve mechanism. Movement of the shuttle valve actuating piston and the shuttle valve are controlled by an urging means that may be adjustably preset for a particular high or low pressure. The shuttle valve incorporates annular peripheral seal that is retained in assembly with the shuttle valve and engagable with and movable partly beyond annular sealing edges defined within the valve body of the valve assembly in order to control fluid communication between the various ports. Slight movement of the shuttle valve peripheral seal away from the annular sealing edges affords substantial cross-sectional flow area for large volume flow, thus providing for rapid pressure responsive actuation. Utilization of sealing elements having low friction characteristics and utilization of a low friction spring for urging the shuttle valve and piston between operative positions thereof, facilitates accurate operation of the pilot valve mechanism at relatively narrow pressure differentials.

FIELD OF THE INVENTION 
This invention relates generally to pilot valves that are typically 
utilized to monitor pressure conditions in a pressurized system and to 
cause the pressurized system to shut or become blocked responsive to 
detection of operating pressures that are above or below a predetermined 
acceptable pressure range. More particularly, the invention is directed to 
the provision of a pilot valve mechanism for use in both high and low 
pressure sensing or in combination high and low pressure sensing which 
pilot valve mechanism facilitates a relatively large volume flow of 
control fluid for rapid actuation or deactivation of associated mechanical 
devices and at the same time effectively prevents displacement or fluid 
erosion of sealing elements in the pilot valve mechanism. The invention 
also relates but is not limited to pressure actuated pilot valve 
mechanisms having shuttle valve seals which contact sealing edges within 
the pilot valve body and have portions of the seals which move past the 
sealing edges. Additionally the invention is related to pilot valve 
mechanisms which pass fluid at a substantially high pressure which may be 
at least as high as pressure in an associated pressurized system. 
BACKGROUND OF THE INVENTION 
Pilot valve mechanisms which may also be referred to as control valves, 
have long been utilized for the purpose of automatically responding to 
pressure variations in a flow system and inducing actuation or 
deactivation of mechanical devices in the event a dangerous or undesirable 
pressure level is sensed. As is typically the case, pilot valves or 
control valves may comprise a valve body having a pressure responsive 
valve element disposed therein for controlling communication between the 
inlet, outlet and vent port of the valve, whereby a mechanical device, 
such as a valve actuator, may be energized by pressurized pilot fluid 
passing through the valve and may be deenergized by blocking application 
of the pressurized pilot fluid and by allowing pilot fluid to be vented 
from the mechanical device through the pilot valve mechanism. 
As is typically the case, a piston within the pilot valve is provided with 
a plurality of annular grooves having O-rings disposed therein, which 
O-rings slide across the inlet, outlet and port openings of the valve, 
depending upon the position of the shuttle valve. When high operating 
pressures are involved, travel of the O-rings across the ports subject 
small areas of the O-rings to radial expansion due to the pressure 
differential acting on them as they travel across the port. This radial 
expansion of the O-rings causes them to be cut or nipped on their 
perimeter thus requiring frequent repair and replacement. Moreover, it has 
been determined that excessively large ports create extremely rapid wear 
of the O-rings, while ports that are sufficiently small to prevent 
excessive O-ring wear typically retard the flow of pressurized medium 
through the pilot valve mechanism and thus prevent rapid actuation of the 
mechanical device that is being controlled. Depending upon the particular 
pressure range at which the pilot valve mechanisms are to function, 
certain optimum port sizes have been developed that allow sufficient flow 
for actuation at acceptable speeds even though the speeds are not 
necessarily optimum. Accordingly, it is desirable at times to provide 
pilot valve mechanisms for actuator systems having the capability of 
allowing rapid flow of pilot fluid for rapid actuation without the 
attendant difficulties that are often associated with the use of sliding 
O-rings of conventional pilot valve mechanisms. 
A problem typically associated with conventional pilot valve mechanisms is 
the tendency of O-rings to become completely displaced from their grooves 
as the result of excessive pressure differential or the tendency of such 
O-rings to become extruded from the groove to such extent that they become 
cut or excessively abraded as the O-ring slides passed various structural 
components of the pilot valve mechanism. It is, therefore, appropriate to 
provide a pilot valve mechanism having a facility for positively retaining 
O-rings in their proper position and for preventing such O-rings from 
becoming extruded from their grooves. 
Where conventional O-rings are employed as dynamic sealing elements and are 
disposed in sliding engagement with a cylindrical wall defining a bore, 
such as is typically the case in most commercially available pilot valve 
mechanisms, the O-ring, after remaining stationary for a suitable period 
of time, will become adhered to the wall structure defining the bore to 
such extent that substantial pressure is necessary to break it loose and 
accomplish the desired actuation. Depending upon the characteristics under 
which the O-rings operate, it may require pressure in the order of 300 PSI 
to break certain O-rings loose from the wall structure of the bore and to 
achieve linear actuation of the piston carrying the O-rings. Of course, 
when the O-rings breaks loose and movement occurs, the piston typically 
slams the opposite position because of the pressure differential that is 
necessary to initiate piston operation. This usually results in erratic 
and undesirable operation of the pilot valve mechanism causing consequent 
erratic operation of the mechanical device with which the pilot valve is 
associated. 
Sticking of O-rings is due largely to the fact that surface areas of piston 
bores have a certain degree of surface imperfection, depending upon the 
characteristics of the machining operation producing the bore. Sticking is 
also affected by temperature of the pilot valve as well as temperature of 
the fluid passing through the valve. Extreme high temperatures and extreme 
low temperatures increase the possibility of sticking due to changes in 
operating characteristics of an O-ring of a specific temperature. The 
material from which most O-rings are composed has a facility for extrusion 
into the surface imperfections and may have a characteristic of 
establishing a permanent or semi-permanent set after a certain period of 
time, thereby causing the O-ring to become mechanically adhered to the 
wall structure of the bore. It is desirable, therefore, to provide a 
sealing element having a material in sealing engagement with the bore, 
which material will be substantially frictionless, to allow relatively 
free movement of the piston in the bore and which material will not 
readily extrude into the surface imperfections of the piston bore and 
become adhered to such surface imperfections. 
It is typical for compression springs to be employed in pilot valve 
mechanisms for imparting a force to a movable shuttle valve assembly that 
controls the flow of control fluid through the pilot valve mechanism. This 
is true primarily because the structure necessary for containing 
compression springs is much simpler and less expensive than other urging 
devices, such as tension springs, for example. Where control pressure 
ranges are fairly wide and exceptional repeatability is not a governing 
factor, pilot valve mechanisms incorporating compression spring devices 
for shuttle valve actuation are quite acceptable. They are less desirable 
when the opposite parameters are controlling. 
When the coils or convolutions of typical compression springs overlap, it 
is obvious that the spring rate of the spring is substantially altered. 
When this occurs, a pilot valve mechanism will also have altered pressure 
responsive characteristics which may render the valve completely 
unacceptable for the service for which it is intended. Alteration of the 
pressures to which the pilot valve mechanism will respond, may create an 
unsafe condition if the altered response pressure of the valve is 
excessively high or low. If the shuttle travel of the valve mechanism is 
great enough to create a condition where coil inteference of the 
compression spring can occur, it may be undesirable to place such a valve 
mechanism in a critical environment. 
Another undesirable pilot valve pressure responsive condition results when 
compression springs of pilot valves bend or buckle to such extent that the 
spring is allowed to rub against an internal surface of the valve 
mechanism or against a surface of a spring guide. When this occurs, the 
frictional rubbing engagement of the spring against another surface will 
substantially alter the spring rate of the spring and will interfere with 
normal spring function. The occurrence of spring rubbing will obviously 
modify the pressure range to which the pilot valve mechanism will respond 
and will frequently render such pilot valve mechanisms undesirable for use 
in environments where accurate pressure response is critical. Spring 
rubbing has the effect of broadening the range of pilot valve pressure 
response which renders compression spring type pilot valves undesirable if 
the high and low pressures to which the valve must respond are narrowly 
spaced. Rubbing of the spring will generally create sufficient frictional 
interference that pilot valves, so constructed, will not respond 
accurately to low pressures. 
Accordingly, it is a primary object of the present invention to provide a 
novel pilot valve mechanism suitable for both high and low pressure 
actuation, wherein the pilot valve mechanism employs a piston and sealing 
arrangement allowing a large amount of flow to occur through the pilot 
valve mechanism with minimal pressure responsive movement of the piston 
and valve assembly thereof. 
Also, it is another primary object of the present invention to provide a 
novel pilot valve mechanism suitable for operation with a pressurized 
fluid in the range of two hundred (200) pounds per square inch (PSI) to 
five thousand (5,000) PSI. 
It is another important object of the present invention to provide a novel 
pilot valve mechanism employing sealing elements that promote effective 
substantially friction-free sealing, promote ease of valve and piston 
actuation and which do not tend to adhere to the wall structure of the 
valve mechanism and interfere with relatively free piston and valve 
movement. 
Among the several objects of the present invention is noted the 
contemplation of a novel pilot valve mechanism developing a flow passage 
through the valve upon opening of a shuttle valve mechanism, which flow 
passage is of a dimension at least as great as the dimension of the inlet, 
outlet or vent ports of the valve mechanism in order to facilitate maximum 
fluid flow for rapid shut-in of a mechanical device associated with the 
pilot valve mechanism. 
It is an even further object of the present invention to provide a novel 
pilot valve mechanism employing an urging means to oppose movement of the 
piston and valve mechanism of the pilot valve assembly and which 
cooperates with the piston and pilot valve mechanism to facilitate 
effective and accurate operation in narrow ranges of pressure differential 
operation of the valve mechanism and to achieve accurate high and low 
pressure operation repeatability. 
It is also an important object of the present invention to provide a novel 
pilot valve mechanism incorporating a tension spring mechanism for 
imparting a pressure controlling force to a shuttle valve mechanism, which 
tension spring mechanism is not affected by friction interference and coil 
override and is accurately responsive a full range of fluid pressures. 
It is also an important object of the present invention to provide a pilot 
valve mechanism that is of simple construction, is reliable in use and low 
in cost. 
Other and further objects, advantages and features of the present invention 
will become apparent to one skilled in the art upon full consideration of 
the matter disclosed herein. The form of the invention, which will now be 
described in detail, illustrates the general principles of the invention, 
but it is to be understood that this detailed description is not to be 
taken as limiting the scope of the present invention. 
SUMMARY OF THE INVENTION 
A preferred embodiment of the present invention may comprise a pilot valve 
body within which may be defined an elongated passage which is disposed in 
fluid communication with the fluid pressure of a pressurized system. A 
piston element may be disposed within the elongated passage and may 
include annular sealing means disposed in engagement with the wall of a 
bore defining a part of the passage, whereby the piston element may be 
movably responsive to pressure variations within the pressurized system. A 
spring, that is adjustable for determination of the pressure at which the 
particular valve may operate, acts through an actuator stem on a shuttle 
valve interposed between the actuator stem and piston to oppose movement 
of the piston and allow piston movement and, consequently, valve movement 
to be proportional to the pressure variations occurring in the pressurized 
system. 
The pilot valve mechanism may employ a shuttle valve having seals, disposed 
at opposite end portions of a central body portion. The seals are disposed 
for sealing contact with annular sealing surfaces defined within the valve 
body. The dimension of the annular sealing surfaces and the chamber within 
which the valve element is movable is chosen such that upon slight 
movement of the seal elements away from the annular sealing surfaces a 
fluid flow area will be developed that is at least as great as the 
dimension of the individual ports, thereby allowing maximum fluid flow 
through the pilot valve mechanism and ensuring rapid actuation of the 
mechanical device with which the pilot valve mechanism is associated. 
The spring that opposes pressure responsive movement of the piston and 
shuttle valves may conveniently take the form of a tension spring, rather 
than a compression spring as is typically employed, which tension spring 
cooperates with the shuttle valve and piston assemblies to ensure precise 
responsiveness and repeatability of the pilot valve mechanism and ensures 
efficient operation under circumstances where the mechanical device, with 
which the pilot valve mechanisms are associated, may function efficiently 
and accurately even though relatively narrow ranges of pressure 
differential are involved. 
Relatively friction-free sealing elements, carried by the piston of the 
valve mechanism and disposed in sliding contact with a bore within which 
the piston is disposed, may incorporate an annular sealing band disposed 
within around the piston and having the outer periphery thereof disposed 
in sealing engagement with other seals inside the bore. The annular 
sealing band may have an inwardly extending groove at each extremity 
thereof serving to retain an O-ring element, that is also disposed within 
the annular groove, to prevent the O-ring element from being displaced 
from the annular groove by fluid pressure. The annular sealing band may 
also be a cylindrical portion of the shuttle valve alternately disposable 
in sealing contact between annular sealing edges in the bore.

IN THE DRAWINGS 
FIG. 1 is a partial sectional view of a pilot valve mechanism connected to 
a support and pressure communicating manifold block; the pilot valve 
mechanism having portions thereof broken away and shown in section; 
FIG. 2 is a fragmentary sectional view of a pilot valve mechanism shown in 
FIG. 1 illustrating the shuttle valve mechanism thereof in greater detail; 
FIG. 3 is a fragmentary sectional view of a pilot valve mechanism 
representing a further modified embodiment of the present invention, 
incorporating a shuttle valve mechanism essentially as illustrated in 
FIGS. 1 and 2, but incorporating a pair of spaced apart annular sealing 
elements; 
FIG. 4 is a fragmentary sectional view of the pilot valve structure of FIG. 
1, illustrating the sliding piston seal, "slipper seal" in detail; 
FIG. 5 is a partial sectional view of a pilot valve mechanism representing 
a modified embodiment of the present invention with the shuttle valve 
mechanism having a tapered seal in the pressure sensing end portion 
thereof; 
FIG. 6 is a partial sectional view of a pilot valve mechanism representing 
a modified embodiment of the present invention with the shuttle valve 
mechanism employing a radially inwardly divergent peripheral groove shaped 
to retain an annular O-ring seal and a seal in the pressure sensing end 
portion thereof; 
FIG. 7 is a fragmentary sectional view of the pilot valve mechanism of FIG. 
6, illustrating the piston and seal elements in greater detail; 
FIG. 8 is a fragmentary sectional view of a shuttle valve mechanism 
representing a modified embodiment of the shuttle valve mechanism shown in 
FIGS. 6 and 7 employing a separable seal ring support assembly to clamp an 
O-ring in place; 
FIG. 9 is a partial sectional view of a pilot valve mechanism representing 
a modified embodiment of the present invention with the shuttle valve 
mechanism having a cylindrical mid-portion disposed between longitudinally 
splined portions thereof and being movable between alternate positions 
engaging annular seals in the valve body; 
FIG. 10 is an enlarged cross-sectional view of the pilot valve mechanism 
shown in FIG. 9 taken on line 10--10 in FIG. 9 illustrating the 
arrangement thereof in greater detail; 
FIG. 11 is a partial sectional view of a pilot valve mechanism representing 
a modified embodiment of the present invention with the shuttle valve 
mechanism having a spherically shaped enlarged portion of the valve 
element; and 
FIG. 12 is a partial sectional view of a portion of a pilot valve mechanism 
representing a modified embodiment of the present invention with the 
shuttle valve element having a spherically shaped enlarged portion and 
being in close and direct connection with the spring system. 
BRIEF DESCRIPTION OF THE RELATED PATENT APPLICATION 
Illustrated in FIG. 1, of the related application, is a typical high-low 
pilot valve assembly including a low pressure responsive pilot valve 
mechanism, illustrated on the right-hand portion of the figure, and a high 
pressure sensitive pilot valve mechanism, illustrated on the left-hand 
portion of the figure, both of which are substantially identical in 
construction and are threadedly connected to a pressure conducting 
manifold and support block having a passage therein and being in 
communication with a manifold and support block inlet through which 
pressurized fluid is connected from a pressurized system for which 
operation control is desired. For example, a pressure conducting conduit 
may communicate pressurized fluid from a flow line that is controlled by a 
valve and valve actuator assembly to the chamber defined by the passageway 
inside the manifold and support block. This pressure is communicated into 
the high and low pressure pilot valves simultaneously. Depending upon 
whether the pressure sensed is within the limits defined by the high and 
low pressure pilot valve, then the pilot valves will allow communication 
of a pilot supply pressure source with the valve actuator, thereby 
maintaining the actuator in an operative condition or the pilot valves 
will vent the fluid to maintain the actuator in a inoperative condition. 
In the event the pressure should rise above an acceptable level or fall 
below an acceptable level, one of the pilot valve mechanisms will 
interrupt flow from the pilot supply source to the actuator and will 
communicate the actuator with a vent, thereby allowing venting of the 
actuator pressure and causing automatic movement of the actuator to a 
position closing the valve with which it is associated. As shown, the 
pressure being sensed is within the predetermined acceptable pressure 
range and, therefore, fluid is communicated from a pilot supply source 
through the low pressure pilot valve, through a connecting conduit and 
through the high pressure pilot valve mechanism to a pilot pressure supply 
conduit that is in communication with the valve actuator. The high and low 
pressure pilot valve mechanisms, as shown in FIG. 1 of the related patent 
application are disposed in a "non-venting" position and the valve 
actuator, being controlled thereby, is therefore disposed in its operative 
position. 
DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1 of the accompanying drawings, the pilot valve 
mechanism of the present invention is indicated generally at 10 and 
incorporates an intermediate body portion 12 housing body sections 14 and 
16 connected thereto. Intermediate body portion 12 has an internally 
threaded extremity 18 that receives the externally threaded axial 
extension 20 of an intermediate connector element 22. Intermediate 
connector element 22 is sealed with respect to body portion 12 by means of 
an annular sealing element 24 that may conveniently take the form of an 
O-ring received within an annular groove formed on the intermediate 
element. Intermediate connector element 22 may likewise have internal 
threads 26 formed at the lower extremity for receiving the externally 
threaded portion 28 of a lower connector element 30. An annular sealing 
element 32, such as an O-ring or the like, may establish sealed 
relationship between the lower connector element 30 and the intermediate 
connector element 22. 
The intermediate connector element 22 may have an axial bore 34 formed 
therein that is disposed in co-axial relationship with an axial bore 36 
defined within the lower connector element 30 and with an axial bore 38 
defined in the body section 16. A piston element 40 may be disposed within 
an elongated passageway defined collectively by the bores 34 and 36 and by 
an enlarged bore 42 defined within the intermediate connector element 22. 
Piston element 40 may be disposed for axial reciprocation within limits 
defined by annular shoulders 44 and 46 defined respectively on the 
intermediate and lower elements 22 and 30. An annular enlarged portion of 
the piston element 40 will engage the surfaces 44 and 46 to limit movement 
of the piston element in either axial direction thereof. 
At the lower extremity of the piston element, as illustrated in FIG. 1, an 
annular seal assembly is disposed about the piston element and establishes 
sealed engagement with the bore 36 thus preventing pressure sensed by the 
pilot valve from entering the valve chamber of the valve. This seal 
assembly 48 is of frictionless or low friction characteristics and is 
described in detail hereinbelow in connection with FIG. 4. At the upper 
extremity of the piston element 40 the perimeter is reduced in diameter, 
slidably retained in bore 34 and provided with an annular seal element 52 
retained in a groove therearound to prevent pressure controlled by the 
pilot valve mechanism from escaping. Another annular sealing element 43 in 
the form of an O-ring is provided around the opposite end portion of the 
shuttle valve to prevent fluid leakage into the upper portion of the 
mechanism. A vent passage 54 is formed in the intermediate connector 
portion 22 and serves to vent any pressurized medium leaking past the 
sealing element 52 and seal assembly 48 thereby providing external 
indication that repair of the pilot valve assemble is necessary. 
The design of the lower extremity of the piston structure may be varied 
within the scope of the present invention, depending upon the particular 
pressure range that is to be sensed by the pilot valve assembly. Where 
variations in high fluid pressures are to be detected, piston structure 40 
may be of relatively small diameter, thus presenting a relatively small 
piston surfce area equivalent to the circular area defined by the bore 
that is acted upon by the pressurized medium being detected. Conversely, 
where variations in low pressure are concerned, the piston structure 40 
and the piston seal assembly may be of a relatively large diameter, thus 
presenting a relatively large piston area which is equivalent to the 
circular area defined by the piston bore against which the pressurized 
medium is being detected. In all variations the piston area equivalent is 
selected in relation to the force developed by the spring system at the 
opposite end of the pilot valve. 
Axial bores 34 and 38 communicated with enlarged annular bore or chamber 
56, which, together with the axial bores, may constitute a valve chamber. 
A shuttle valve assembly, illustrated generally at 58 and shown in 
enlarged detail in FIG. 2, is movably disposed within valve chamber 56 
and, upon being moved, responsive to variations in pressure differential 
sensed by the pilot valve mechanism, may control the flow of actuating 
pressure, also referred to as pilot pressure, to a remotely located device 
for actuation thereof. 
Shuttle valve support extensions 60 and 62 are provided on the shuttle 
valve 58. Support extension 60 has a depression 64 in the end thereof to 
receive a pointed support portion 66 of shuttle valve support element 68. 
Shuttle valve support element 62 is rigidly attached in axial alignment 
with piston element 40. Shuttle valve support element 62 can be integrally 
formed with piston element 40 if desired. 
Shuttle valve support element 68 is positioned axially of bore 38. Shuttle 
valve support element 60 is urged downwardly by a tension spring 70 
carried by a spring adjustment element 72. The tension spring 70, always 
being in tension, will not have any tendency to buckle or bend and, 
therefore, it will not be susceptible to rubbing friction contact with the 
internal surfaces of the valve mechanism nor will it have any tendency to 
establish rubbing contact with the stem 68. The spring rate of the tension 
spring will always remain stable and, therefore, the pressure response 
range of the pilot valve mechanism will not vary from its precise setting 
because of spring interference. Moreover, maintenance of the spring 70 in 
tension will effectively eliminate the problem of spring override and, 
therefore, will prevent convolutions of the spring from interfering with 
one another and otherwise altering the spring rate of the spring. Spring 
adjustment element 72 is provided with an externally threaded portion 74 
disposed in threaded engagement with an internally threaded bore 76 
defined in the upper extremity of upper valve body section 16. 
At the upper extremity of the stem 68 is provided a frusto-conical portion 
80 that may be received within a conical depression formed in a spring 
retainer element 82 that is in turn secured within the upper extremity of 
the tension spring 70. The lower extremity of tension spring 70 is secured 
to a spring retainer 84 having a lower annular flange 86 received within a 
corresponding recess in the lower portion of the adjustment element 72, 
thereby serving to positively restrain movement of the lower portion of 
the tension spring. 
Upper body section 16 has an axial extension 88 threadedly engaged in 
intermediate body portion 12. A seal element in the form of an O-ring 90 
is provided around axial extension 88 at the juncture of upper body 
section 16 and intermediate body section 12 to prevent fluid leakage to 
the exterior of the mechanism. Upper body section axial extension 88 is 
similar to intermediate connector element axial extension 20. Seal 
elements in the form of O-rings 90 and 92 are provided in grooves in 
intermediate body section 12 around axial extensions 88 and 20 
respectively. Axial extensions 88 and 20 have adjacent ends thereof spaced 
apart with inner annular edges thereof defining annular sealing edges 94 
and 96 respectively. Valve chamber 56 includes enlarged bore portions 98 
and 100 at respective end portions of axial extensions 88 and 20 which 
join respective sealing edges 94 and 96. 
A plurality of flow passages 102, 104, and 106 are disposed through body 
section 12 and axial extensions 88 and 20 in communication with the valve 
chamber 56 and, depending upon utilization of the valve mechanism for high 
pressure or low pressure responsive control or depending upon utilization 
of pilot valves in high-low pressure sensing combination, the ports may 
have different functions. For example, assuming the pilot valve mechanism 
to be utilized as the high pressure pilot valve of a high-low pressure 
pilot valve combination assembly, such as generally described above and 
set forth in FIG. 1, port 104 will represent an inlet port through which 
pilot fluid may flow from the low pressure pilot valve mechanism into the 
valve chamber 56. Port 106 will represent an outlet port through which 
fluid may flow from the valve chamber 56 to control the valve and actuator 
mechanism with which the pilot valve assembly may be associated. Port 102, 
under this circumstance, will represent a vent port through which fluid 
may be vented from the valve and actuator mechanism through the port 106 
in the event of high pressure shut-in. 
The intermediate connector element axial extension 20 is cut away to define 
an external annular groove 108 cooperating with the wall structure of the 
valve body portion 12 to define an annular chamber disposed in 
communication with the port 102. Fluid communication, between the annular 
chamber defined by the groove 108 and the valve chamber within which the 
shuttle valve is movably disposed, may be defined by one or more points 
110, formed through the wall structure of the axially extending portion 
20. A similar annular groove 112 may be formed in body section axial 
extension 88 and a similar port or ports 114 provided to establish fluid 
communication between valve chamber 56 and port 104. 
Referring now specifically to FIG. 2, shuttle valve element 58 is disposed 
for reciprocal movement within valve chamber 56. Shuttle valve element 58 
may incorporate an enlarged intermediate portion 116 having an annular 
groove 118 formed therein, which groove may receive an annular sealing 
element 120. The sealing element 120 may conveniently take the form of an 
elastomeric O-ring or any other suitable sealing device without departing 
from the spirit and scope of the present invention. 
It is to be noted that annular sealing element or O-ring 120, when disposed 
in touching engagement with an annular sealing edge 96 of body axial 
extension 20, will be slightly spaced from the other annular edge 94 
defined by the opposite body axial extension 88. This feature promotes 
rapid operation of the valve mechanism upon slight axial movement of the 
shuttle valve element 58, because it is only necessary that the O-ring 120 
be moved a few thousandths of an inch in order to be brought into sealing 
engagement with the sealing edge of the opposite body axial extension. 
Full flow communication between the outlet port 106 and one of the high 
pressure or low pressure ports 104 and 102, respectively, may be 
effectively accomplished upon slight movement of the O-ring element, 
responsive to slight movement of the shuttle valve 58. Further movement of 
the shuttle valve in either direction will merely cause O-ring 120 to be 
moved within the respective bore defined within the appropriate valve body 
axial extension. Since opening and closing of the shuttle valve mechanism 
will occur upon slight movement of shuttle valve 58, it is obvious the 
pilot valve mechanism will be immediately responsive to slight pressure 
changes above or below the preset pressure level for which actuation of 
the valve mechanism is desired. 
The shuttle valve assembly may achieve a sealing function by moving annular 
sealing element 120 into sealed abutment with respective annular sealing 
edges 94 and 96. The valve construction is such that a slight movement of 
O-ring sealing element 120, away from the respective annular sealing edge, 
will facilitate development of a flow passage of a dimension at least as 
great as the dimension of the valve ports 102, 104, and 106. This feature 
allows rapid development of sufficient flow passage dimension to allow 
maximum flow of pilot fluid from the valve and actuator mechanism during 
venting, thereby facilitating extremely rapid shut-in, responsive to 
sensing of undesirable pressure conditions. During tests, it has been 
determined that valve movement of as little as 0.020 inch is effective to 
achieve a flow passage dimension as great as the dimension of the inlet, 
outlet or vent ports. 
In pilot valve mechanisms it is highly desirable to provide a mechanical 
apparatus that is responsive to sensation of pressure variations to 
provide a flow of pressurized control fluid or to allow control fluid to 
be bled from an acuator mechanism. It is also desirable that the pilot 
valve mechanism has exceptional repeatability, i.e., repeated actuation at 
precise pressure levels and that it be capable of functioning within 
relatively narrow ranges of pressures. 
It is common to employ O-rings in pilot valve mechanisms for control of 
fluid flow therethrough and for separation of areas of unbalanced pressure 
such as in the lower portion of the pilot valve mechanisms shown herein. 
O-rings that slide against cylindrical surfaces to achieve sealing between 
movable elements are quite effective in operation, but tend to detract 
from desired features of repeatability and narrow pressure range operation 
of pilot valve assemblies, because of the substantial level of friction 
that is often developed between the O-rings and the respective sealing 
surfaces. It is also well known that O-rings tend to be displaced or 
squeezed from the annular grooves thereof as pressure applied to the 
O-rings is increased, which displacement causes the O-rings to enlarge and 
substantially increase in frictional sealing contact with the cylindrical 
surfaces against which the O-rings slide. This feature causes frictional 
interference to vary as pressure varies and, therefore, causes pressure 
responsive pilot valve operation to be erratic in nature. 
The erratic nature of O-ring utilization is further evident because 
O-rings, when allowed to remain stationary for long periods of time, tend 
to stick to the sealing surfaces. Considerable pressure differential is 
typically necessary to break the O-rings loose from the sealing surfaces 
and such pressure differential obviously detracts from accurate operation 
of the pilot valve mechanism. 
According to the present invention, one suitable construction for providing 
a sealing mechanism that has low friction capability to promote 
repeatability in operation which promotes narrow pressure range operation 
of pilot valve mechanisms and which also will not stick when allowed to 
remain stationary for long periods of time may conveniently take the form 
of the seal assembly indicated generally at 48 and illustrated in FIG. 4. 
The piston element 40 may be provided with a reduced diameter portion 122 
that is received in close fitting, but non-touching relation within the 
bore 36. The reduced diameter portion 122 may be provided with a further 
reduced diameter axially extending portion 124 that receives seal assembly 
48 that may be referred to as a "slipper seal assembly" and incorporates 
an inner soft elastomeric sealing element that serves both as a sealing 
element and as an urging means for a stable friction resistant element 
disposed thereabout. 
The soft elastomeric sealing element 126 may be disposed about the 
generally cylindrical sealing surface 128 in sealing engagement therewith 
and may be received in encircled relation within a relatively thin annular 
sealing band 132 having exceptional sealing ability and low friction 
characteristics and which does not have an affinity for sticking to the 
cylindrical sealing surface established by the bore 36. 
The slipper seal assembly may be retained in assembly with the axially 
extending portion 124 of the piston element 56 by an annular retainer 
element 134 that is received within an annular groove 136 formed in the 
axial extension 124 and which retainer element may conveniently take the 
form of an O-ring composed of any suitable elastomeric material. It should 
be borne in mind that slipper seal assembly 48 will be subjected to 
pressure from one direction only and, therefore, it is not necessary that 
the retainer element 134 be capable of retaining the slipper seal when the 
seal is subjected to fluid pressure from both directions. Retainer element 
134 serves to retain the slipper seal in position on the axial extension 
124 during assembly of the valve mechanism and also retains the slipper 
seal in position on the extension during periods when the valve mechanism 
is not subjected to pressure. 
Slipper seal assembly 48 may comprise an annular sealing band 132 composed 
of a friction resistant material such as polotetrafluoroethylene, for 
example, which will establish sealing engagement within the bore 36, but 
will not be susceptible to sticking. Moreover, the slipper seal assembly 
may include a soft annular elastomeric sealing element having the 
capability of yielding to fluid pressure and enhancing the sealing ability 
of the sealing band. As depicted in detail in FIG. 4, an elastomeric 
annular sealing element 126, which also functions as an urging means, is 
received in close fitting relation about the reduced diameter portion 124 
of the piston and is interposed between the reduced diameter portion of 
the piston and the annular sealing band, serving to impart radial forces 
to the thin sealing band that urges the peripheral portion of the sealing 
band into sealing engagement with the internal surface defined by bore 36. 
One difficulty, attendant with the use of O-rings for the purpose of 
sealing under high pressure conditions, is the fact that the O-rings may 
tend to extrude outwardly of the O-ring recess where it may become damaged 
or subjected to extensive wear as it slides within the bore with which 
sealing contact is to be maintained. To prevent extrusion of the O-ring 
134 from the groove 136, the annular sealing band 126 may be provided with 
a pair of annular inwardly extending flanges 138 and 140 having inwardly 
tapered generally frusto-conical surfaces 142 and 144 defined respectively 
thereon. The frusto-conical surfaces 142 and 144 provide a camming 
function tending to urge the annular sealing element 126 toward a 
centralized position between the flanges 138 and 140. Should the sealing 
element 126 be moved in either lateral direction, responsive to 
application of pressure, the annular retainer flanges 138 and 140 will 
effectively prevent O-ring element 126 from being extruded from the groove 
where it might be damaged or become excessively worn. Moreover, as soon as 
the pressure being sensed by the O-ring and sealing band structure has 
dissipated to an acceptable level, the O-ring will tend to be returned 
toward a centralized position between the cam surfaces 142 and 144 by the 
camming action of respective ones of the cam surfaces. 
To establish a relatively friction-free sliding relationship between the 
annular sealing band 132 and the wall structure 38 of the bore, the 
sealing band may be composed of a material having low friction 
characteristics and which will not tend to become adhered to the wall 
structure of the bore 38. It has been determined that sealing band 
composed of polytetrafluoroethylene, or any other similar acceptable 
plastic material, may be utilized quite efficiently. The annular sealing 
element 132 may be composed of any one of a number of suitable elastomeric 
materials, depending upon the characteristics of the fluid with which it 
may come into contact. 
Referring now to FIG. 3, it may be desirable to provide a shuttle valve 
mechanism having a pair of annular O-rings instead of the single O-ring 
type shuttle valve element set forth in FIGS. 1 and 2. It will be 
desirable to space axial extensions 146 and 148 to such extent that one of 
the O-rings 150 will engage an annular edge 152 thereof while the opposite 
O-ring sealing element 154 will be disposed in slightly spaced 
relationship with the opposite annular edge to achieve interruption of the 
flow between the outlet part 158 and either of the high or low pressure 
parts 160 and 162. 
Referring now to FIG. 6, there is disclosed a pilot valve mechanism 
illustrated generally at 170 which constitutes a further modified 
embodiment of the present invention and incorporates an intermediate body 
section 172 having upper body sections 174 and intermediate coupler 
element 176 connected thereto. Axially extending portions 178 and 180 of 
upper body section 174 and intermediate coupler element 176 are threadedly 
engaged with the intermediate body section 172 and provide valving 
extensions 182 and 184 that are disposed in closely spaced opposed 
relationship as shown in detail in FIG. 7. The valving extensions 182 and 
184 are disposed in sealed relationship with the intermediate body section 
172 by means of annulr sealing elements 186 and 188, respectively, which 
may conveniently take the form of O-rings, retained within annular O-rings 
grooves, or in the alternative, may take any other desirable form as 
deemed appropriate. The valving extensions 182 and 184 may have annular 
grooves 190 and 192 defined in the outer peripheral portion thereof which 
grooves may be disposed in communication with shuttle valve element 
receiving bore 194 by appropriate transverse passages 196 and 198 
respectively. 
A valving element, illustrated generally at 200 in FIG. 7, may be disposed 
for reciprocal movement within the bore 194 and within an annular chamber 
202 defined by the annulus existing immediately about the shuttle valve 
element 200 and between end portions of valving extensions 182 and 184. 
Shuttle valve element 204 having an annular groove 206 formed therein, 
which groove may receive an annular sealing element 208. The sealing 
element 208 may conveniently take the form of an elastomeric O-ring or any 
other suitable sealing device without departing from the spirit and scope 
of the present invention. Annular groove 206 can be formed as shown with a 
generally trapezoidal cross-section and having opposing sides thereof 210 
and 212 divergent from the open outer portion of the groove toward the 
bottom or closed end portion thereof. The extension 214 of the 
intermediate portion of shuttle valve element 200 is reduced in diameter 
relative to bore 194 except for the portion adjacent to groove 206 which 
protrudes radially outward for support of O-ring 208 and to form outer 
portions of sides 210 and 212. Valving extensions 182 and 184 are 
respectively provided with annular facing surfaces 216 and 281 which each 
respectively have outwardly divergent frusto-conical inner edge surfaces 
intersecting bore 194 at sealing edges 220 and 222. Valve body 
intermediate section 172 has an enlarged annular portion 224 therein 
around the adjacent end portions of valving extensions 182 and 184. 
It is to be noted that annular sealing element 208, when disposed in 
touching engagement with an annular sealing edge 222 of the valving 
extension 184, will be slightly spaced from the annular edge 220 on the 
opposite valving extension. This feature promotes rapid operation of the 
valve mechanism upon slight axial movement of the shuttle valve element 
200, because it is only necessary that the O-ring 208 be moved a few 
thousandths of an inch in order to be brought into sealing engagement with 
the sealing edge of the opposite valving extension. Full flow 
communication between the outlet port 226 and one of the high pressure or 
low pressure ports 228 and 230, respectively, may be effectively 
accomplished upon slight movement of the O-ring element, responsive to 
slight movement of the shuttle valve 200. Further movement of the shuttle 
valve in either direction will merely cause the O-ring element 208 to be 
moved within the respective bore defined within the valving extension. 
Since opening and closing of the shuttle valve mechanism will occur upon 
slight movement of the shuttle valve, it is obvious that the pilot valve 
mechanism will be immediately responsive to slight pressure changes above 
or below the present pressure level for which actuation of the valve 
mechanism is desired. 
Section 174 of the valve housing may be internally threaded as shown as 232 
in order to receive an externally threaded portion 234 of a spring housing 
element 236 that also provides a cover for a compression spring 238 that 
is retained in assembly with an adjustment element 340 threadedly mounted 
in spring housing element 236. A stem 242 has a spring abutment element 
244 thereof which rests in contact with one end of spring 238. Stem 242 
has a conical extremity 246 to engage a conical indentation of shuttle 
valve element 200. Compressive force of spring 238 may be adjusted simply 
by rotating the adjustment element 240 relative to spring housing element 
236, thereby causing the compression of the spring 238 to be increased or 
decreased as is desired for appropriate setting of the pressure range to 
which the pilot valve mechanism is responsive. 
The shuttle valve element 200 may be disposed in abutment with an elarged 
portion 248 of a piston element 250 which piston element has a sealing 
portion thereof received within a bore 252 defined within a lower body 
section 254. A slipper seal mechanism indicated generally at 256, 
constructed and functioning essentially identical as compared with the 
slipper seal mechanism illustrated and described in connection with FIG. 
4, may be provided at one extremity of the piston 250 in order to 
establish friction resistant sealing capability with respect to the bore 
252. The enlarged portion 248 of the piston element 250 may engage 
abutment surfaces 258 and 260 to limit axial movement of this piston and 
the shuttle valve element in either aixal direction thereof. Enlarged 
portion 248 has a conical surface 249 on the lower end thereof which may 
engage a conical seat surface 251 around bore 252 at abutment surface 258 
when enlarged piston portion 248 is in the lowered position as shown. The 
sealing surfaces are an important feature of the pilot valve mechanism of 
this invention because it provides a metal-to-metal seal in the pressure 
exposed portion of the mechanism which will seal in the event other 
resilient seals are destroyed such as by fire. 
Referring now to FIG. 5, there is disclosed a pilot valve mechanism 
indicated generally at 201 which constitutes a further embodiment of the 
present invention and includes the basic features of pilot valve mechanism 
170 shown in FIG. 6 but further includes minor changes in the shuttle 
valve element 203, the intermediate body portion 205, and the enlarged 
piston portion 207. Intermediate body portion 205 is constructed to 
directly contain the bore 209 which slidably receives and contains shuttle 
valve element 203. Shuttle valve element 203 has one enlarged intermediate 
portion with an O-ring seal member mounted in an annular groove therein 
which contacts bore 209 and moves across an outlet opening 211. Outlet 
opening 211 is in fluid communication with an outlet port through body 
intermediate portion 205. Inlet and vent ports are provided through 
intermediate body portion 205 in fluid communication with the valve 
chamber defined by the bore around shuttle valve element 203. A spring 
assembly is provided on the upper end of shuttle valve element 203 to urge 
it downward in opposition to fluid pressure acting on the pressure sensing 
piston. Operation and functioning of pilot valve mechanism 201 is the same 
as the pilot valve mechanism shown in FIG. 6. 
Enlarged piston portion 207 is provided with oppositely tapered conical 
sealing surfaces 213 and 215 on opposing upper and lower ends thereof 
which engage in respective seat surfaces 217 and 219 in upper and lower 
portions of the chamber enclasing piston enlarged portion 207 such that 
metal-to-metal seating is accomplished between the piston and the valve 
body. This metal-to-metal seating of enlarged piston portion 207 is an 
important feature of this invention because such provides an auxiliary 
seal to prevent fluid leakage from the fluid pressure being sensed and the 
valve chamber. This metal-to-metal seating around enlarged piston portion 
207 insures sealing in case other resilient seals are destroyed such as by 
a fire. 
Now referring to FIG. 8, there is disclosed a shuttle valve element 
indicated generally at 262 which constitutes a modified embodiment of the 
shuttle valve incorporated in the pilot valve of this invention. Shuttle 
valve element 262 is an alternate or equivalent structure for shuttle 
valve element 200 shown in FIGS. 6 and 7 and can be substituted for 
shuttle valve element 56 shown in FIGS. 1 and 2. This shuttle valve 
element 262 includes a pair of axially aligned segments 264 and 266 joined 
together at a reduced diameter mid-portion thereof by a further reduced 
diameter externally threaded bore 270 of segment 266. Segments 264 and 266 
abut a slightly reduced diameter portions 272 and 274 respectively. A pair 
of seal element support collars 276 and 278 encircle reduced diameter 
portions 272 and 274 and extend the combined axial length of these reduced 
diameter portions such that they are firmly retained between segments 264 
and 266 when such segments are secured together. Collars 276 and 278 abut 
each other around inner annular portions of adjoining ends thereof and 
have cross-sectionally concave curved cuter portions 280 and 282 
respectively which join the periphery of the collars. Such concave 
portions cooperate to secure sides of an annular seal element 284 which 
can conveniently be in the form of an elastomeric O-ring. Concave sides 
280 and 282 contact the annulus portion and opposing sides of O-ring 284 
with only an outer peripheral edge portion of O-ring 284 protruding from 
collars 276 and 278 for contacting bore 194 and sealing edges 200 and 222. 
Grooves 286 and 288 are provided around the large diameter opposite end 
portions of shuttle valve element 262 for mounting O-rings as an opposing 
ends of the other shuttle valve element. 
Referring now to FIG. 9, there is disclosed a pilot valve mechanism 
illustrated generally at 290 which constitutes a further modified 
embodiment of the present invention and incorporates an intermediate body 
section 292 having an upper end body section 294 and an interconnecting 
end body section 296 connected thereto. A lower body section 298 is 
connected to interconnecting body section 296. Axially extending portions 
300 and 302 of the body portions 294 and 296 are threadedly engaged with 
intermediate body section 292 and have separate respective valving or 
sleeve extensions 304 and 306 fitting within the central bore of body 
section 292 the ends of which are disposed in closely spaced opposed 
relationship as shown. The valving extensions 304 and 306 are disposed in 
sealed relationship with the intermediate body section 292 by means of 
annular sealing elements 308, 310, 312 and 314 respectively, which may 
conveniently take the form of O-rings, retained within annular O-ring 
grooves in the outer circumference of sleeve extensions 304 and 306, or in 
the alternative, may take any other desirable form as deemed appropriate. 
The valving extensions 304 and 306 have transverse passageways 316 and 318 
through the outer peripheral portion thereof with such passageways 
disposed in communication with bore 320 through the valving extensions. 
Annular seal members 321 and 323 are provided in valving extensions 304 
and 306 respectively within annular O-ring grooves around the interior of 
bore 320 at end portions of the bore to provide a fluid seal at opposite 
end portions of shuttle valve element 322. Sleeve extensions 304 and 306 
thus provide separate inserts within the central bore of intermediate body 
section 292. 
Shuttle valve element, illustrated generally at 322 is disposed for 
reciprocal movement within the bore 320 of sleeve inserts 304 and 306 and 
within an annular chamber defined by the portion of bore 320 immediately 
about shuttle valve element 322 and between valving extensions 304 and 
306. A pair of annular O-ring sealing elements 326 and 328 are mounted in 
grooves inside the bore 320 of respective valving extensions 304 and 306 
at the mutually adjacent ends thereof. Annular sealing elements 326 and 
328 form annular sealing edges for contacting the valve element. Shuttle 
valve element 322 includes a central segment having an essentially 
cylindrically shaped mid-portion 330 forming a sealing section disposed 
between longitudinally fluted or splined opposed portions 332 and 334, and 
outer segments 336 and 338 joining splined portions 332 and 334 and 
supporting shuttle valve element 232 in bore 320. Outer segments 336 and 
338 join splined portions 232 and 234 respectively at reduced diameter 
segments thereof and such are disposed in fluid communication with 
passageways 316 and 318. FIG. 10 shows a cross section of pilot valve 
mechanism 290 taken transversely through shuttle valve splined portion 334 
illustrating the construction thereof in detail. Splined portion 334 is 
formed by a plurality of spaced grooves 240 cut in the shuttle valve 
element. Grooves 240 are preferably arranged in a regular spaced relation 
as shown in FIG. 10. The formation of grooves 240 can be done by cutting 
from the end the centrally enlarged portion thereof toward the center 
portion thereof terminating in a uniform spaced relation to ends of the 
centrally enlarged portion. 
Grooves 240 are cut such that the sealing section 330 is slightly shorter 
than the distance between the annular sealing edges of sealing elements 
326 and 328 so that when a seal is established between one sealing edge 
and cylindrical sealing section 330 there will not be a seal with the 
other sealing edge. This feature promotes rapid operation of the valve 
mechanism upon slight axial movement of the shuttle valve element 322, 
because it is only necessary that sealing section 330 be moved a few 
thousandths of an inch in order to be brought into sealing engagement with 
the sealing edge of the opposite valve extension. Full flow communication 
between the outlet port 342 and one of the high pressure or low pressure 
parts 344 and 346 respectively, may be effectively accomplished upon 
slight movement of the sealing section 330, responsive to slight movement 
of the shuttle valve 322. Further movement of the shuttle valve in either 
direction will merely cause sealing section 330 to be moved within the 
respective bare defined within the valving extension. Since opening and 
closing of the shuttle valve mechanism will occur upon slight movement of 
the shuttle valve, it is obvious that the pilot valve mechanism will be 
immediately responsive to slight pressure changes above or below the 
present pressurelevel for which actuation of the valve mechanism is 
desired. 
Section 294 of the valve housing may be internally threaded as shown at 348 
in order to receive an externally threaded portion 350 of a spring housing 
element 354 that is retained in assembly with an adjustment element 356 
threadedly mounted in spring housing 352. A stem 358 has a spring abutment 
element 360 which rests in contact with one end of spring 354. Stem 358 
has a conical extremity 360 engaging a conical indentation of shuttle 
valve element 322. Compression force of spring 354 may be adjusted simply 
by rotating the adjustment 353 relative to the threaded portion of spring 
housing section 352, thereby causing the tension of the spring 354 to be 
increased or decreased as is desired for appropriate setting of the 
pressure range to which the pilot valve mechanism is responsive. 
The shuttle valve element 322 may be disposed in abutment with an enlarged 
portion 362 of a piston element 364. Piston element has a sealing portion 
thereof received within a bore 366 defined within a body section 298. A 
slipper seal mechanism indicated generally at 368, constructed and 
functioning essentially identical as compared with the slipper seal 
mechanism illustrated and described in connection with FIG. 4, may be 
provided at one extremity of the piston 364 in order to establish friction 
resistant sealing capability with respect to bore 366. The enlarged 
portion 362 of the piston element 364 may engage abutment surfaces 370 and 
372 to limit axial movement of the piston and the shuttle valve element in 
either axial direction thereof. 
Referring now to FIG. 11, there is disclosed a pilot valve mechanism 
illustrated generally at 370 which constitutes a further modified 
embodiment of the present invention and incorporates an intermediate body 
section 372 having an upper body section 374 and a lower body section 376 
connected thereto. Axially extending portions 378 and 380 of the 
respective body portions 374 and 376 are threadedly engaged in the 
intermediate body section 372. A valving extension 383 extends from axial 
extending portion 378 into a mid-portion of intermediate body portion 372. 
The valving extension 382 is disposed in a sealed relationship with the 
intermediate body section 372 by means of annular sealing element 384 
between body portions 374 and 372 and another sealing element around 
valving extension 378. Sealing elements 384 and 386 may conveniently take 
the form of O-rings, retained within annular O-ring grooves, or in the 
alternative, may take any other desirable form as deemed appropriate. The 
valving extension 378 has an annular groove 388 defined in the outer 
peripheral portion thereof which such groove is disposed in communication 
with a bore 390 by appropriate transverse passages 392. An enlarged 
portion 394 of bore 390 in the opposite end portion of intermediate body 
372 is connected by a passageway 396 to a port. 
A valving element, illustrated generally at 398 is disposed for reciprocal 
movement within bore 390 and within an annular chamber 400 defined by the 
annulus existing immediately about the shuttle valve element 398 and 
including the adjacent portion of bore 390. Valve element 398 has an 
enlarged substantially spherically shaped enlarged portion 402 rigidly 
mounted on a mid-portion of an elongated stem element 404 that is disposed 
for longitudinal sliding movement in bore 390. Stem 404 is smaller is 
diameter than bore 390 through the portion thereof located in valve 
chamber 400. Stem 404 has an annular seal support member 406, an annular 
seal member 408 and a seal retainer member 410 on the lower end portion 
thereof and a similar seal support member 412, annular seal 414, and seal 
retainer 416 on the opposite or upper end thereof. 
It is to be noted that the annular sealing element 402, when disposed in 
touching engagement with the annular sealing edge 418 of intermediate body 
portion 372 such will be slightly spaced from the annular sealing edge 420 
of the valving extension 382. This feature promotes rapid operation of the 
valve mechanism upon slight axial movement of the shuttle valve element 
398, because it is only necessary that the sealing element 402 be moved a 
few thousandths of an inch in order to be brought into sealing engagement 
with the sealing edge of the opposite valving extension. Full flow 
communication between the outlet port 422 and one of the high pressure or 
low pressure ports 424 and 426, respectively, may be effectively 
accomplished upon slight movement of the O-ring element, responsive to 
slight movement of the shuttle valve 398. Further movement of the shuttle 
valve in either direction will merely cause the portion of sealing element 
402 adjoining stem to be moved within the respective portion of bore 390 
defined within valving extension 398 or intermediate body portion 372. 
Since opening and closing of the shuttle valve mechanism will occur upon 
slight movement of the shuttle valve, it is obvious that the pilot valve 
mechanism will be immediately responsive to slight pressure changes above 
or below the preset level for which actuation of the valve mechanism is 
desired. 
Section 374 of the valve housing may be internally threaded as shown at 428 
in order to receive an externally threaded portion 430 of a spring 
adjustment element 432 that also provides a cover mechanism for a 
compression spring 434. One end of spring 434 abuts a shoulder inside 
spring adjustment element 432. An elongated force transmitting stem 436 
extends through spring 434 into spring adjustment element 432 and has a 
conical lower end portion 438 resting in a conical depression in the upper 
end of valve stem 404. A collar 440 of friction resistant material is 
located in an internal annular groove in spring adjustment element 432 to 
contact force transmitting stem 436. A spring abutment element 442 is 
rigidly secured to force transmitting stem 436 and abuts the lower end of 
spring 434. The tension of the spring 434 may be adjusted simply by 
rotating the adjustment element 432 relative to the threaded portion 428 
of housing section 374, thereby causing the tension of the spring 434 to 
be increased or decreased as is desired for appropriate setting of the 
pressure range to which the pilot valve mechanism is responsive. 
The shuttle valve element 398 may be disposed in spaced relation to an 
enlarged portion 444 of a piston element 446 which has a sealing portion 
thereof received within a bore 448 defined within a body section 376. A 
slipper seal mechanism 450, constructed and functioning essentially 
identical as compared with the slipper seal mechanism illustrated and 
described in connection with FIG. 4, is provided at the lower extremity of 
the piston 446 in order to establish friction resistant sealing capability 
with respect to the bore 448. A vent passageway 447 connects the chamber 
enclosing piston end 444 to the atmosphere through body section 372. The 
enlarged portion 444 of the piston element 446 may engage abutment 
surfaces 452 and 454 to limit axial movement of the piston in either axial 
direction thereof. It is to be noted that piston 446 is a member separate 
from shuttle valve element 398. The lower end 456 of shuttle valve element 
398 is spaced from the upper end 458 of piston 446 when the piston is in 
the lowered position as shown, such that spherical valve element 402 will 
contact sealing edge 418 under the full force from spring 434. Where fluid 
pressure raises in bore 448 piston 446 is displaced upward contacting 
shuttle valve lower end 456 and unseating spherical valve element 402. The 
spacing of shuttle valve element end 456 and piston upper end 458 is 
necessary to insure positive seating of spherical valve element 402. 
Referring now to FIG. 11, there is depicted a modified embodiment of the 
shuttle valve mechanism of this invention, the modification relating to 
the shuttle valve mechanism and upper portion of the valve body. The pilot 
valve mechanism of this embodiment is generally indicated at 460 and 
includes an intermediate body section 462 having a threadedly mounted 
upper body section 464 and a lower body intermediate coupler 466. A lower 
body section 468 is threadedly mounted on the lower end of lowr body 
intermediate coupler 466 with piston 470 enclosed therein. Upper body 
section 464 threadedly mounts spring adjustment element 472 on the upper 
end thereof and has an axial extension on the lower end thereof with the 
inner end most portion being a valving extension 474. Shuttle valve 
element, indicated generally at 476, is enclosed in a chamber 478 defined 
by the zone immediately therearound and adjoining portions of the bore 
480, and includes a substantially spherically shaped valve element 482 
mounted on one end portion of a valve stem 484 slidably disposed in bore 
480. Stem 484 is substantially smaller in diameter than bore 480 and has 
an annular seal element 486 supported between a collar 488 and a retainer 
member 490 which engage bore 480 to guide the lower end of stem 484. Valve 
stem 484 has a conical depression in the upper end thereof to receive a 
conical end portion 492 of a spring force transmitting stem 494. Spring 
stem 494 is centrally disposed through a compression spring 496 enclosed 
in body section 462. Spring stem 494 is smaller in diameter on the lower 
end portion 984 which extends through the portion of bore 480 in valving 
extension 474. Because lower spring stem portion 948 is smaller than bore 
480 fluid communication is established between valve chamber 478 and the 
spring chamber 500. 
Intermediate valve body section 462 contains outlet port 502 which 
communicates with valve chamber 478 and inlet port 604 which communicates 
with bore 480 below chamber 478. Bleed port 506 is located in upper body 
section 464 communicating with spring chamber 500. Spherical valve element 
482 contacts a sealing edge 508 in intermediate body section 462 when in 
the lowered position as shown in FIG. 12 and when in the raised position 
the opposite side of the spherical valve element 482 is in sealing contact 
with either sealing edge 508 or 510, the end portion thereof extends into 
bore 480 and beyond the associated sealing edge. Further, it is to be 
noted that the pilot valve mechanism of this embodiment has a piston and 
slipper seal structure similar to that shown in FIG. 11 and described in 
conjunction therewith. 
OPERATION 
Referring to the pilot valve mechanism shown in FIG. 1 and assuming that a 
pair of such mechanisms are connected in a high-low series relation, both 
mounted on a common manifold and operably connected in a safety system as 
described above, both the high and low pressure pilot valve mechanisms 
will be disposed in the non-venting position thereof as long as pressure 
communicated into the manifold is within a normal operating range. If, for 
some reason, the pressure should fall below the operating range, the 
tension spring will urge the shuttle valve 58 downwardly, in both pilot 
valve mechanisms, thereby causing sealing element 120 thereof to engage 
the lower annular sealing edge 96, causing the supply of pilot pressure to 
be blocked and allowing pilot pressure medium from the associated valve 
and actuator assembly to be communicated through a conduit to port 106 of 
the high pressure pilot valve and through a conduit connecting the pilot 
valves and through the low pressure pilot valve to the bleed port 104 
thereof where it will be vented to the atmosphere, or in the alternative, 
will be conducted to a suitable receiver for disposal. As discussed above, 
only slight axial movement of the piston and shuttle valve element is 
necessary to achieve full opening of a flow passage area through the pilot 
valve assembly that is at least as great as the dimension of the bleed and 
pilot supply passages. The valve actuator will, therefore, vent quite 
rapidly, allowing rapid shut-in of the valve with which the actuator is 
associated. The high pressure pilot, under these conditions, will remain 
in the position illustrated in FIG. 1 with the shuttle valve element 58 in 
its lowermost position. 
In the event fluid pressure within the manifold should become excessive, 
such pressure in the high pressure pilot valve mechanism acting upon the 
piston assembly 40, will urge the shuttle valve element 58 upward, thereby 
blocking communication between conduits 106 and 104 and opening 
communication between conduit 106 and the vent port 102. Pressurized 
medium within the valve actuator, under this circumstance, will be allowed 
to vent through the bleed port 102 of the high pressure pilot valve 
mechanism and the valve actuator and valve assembly will again be 
immediately moved to a predetermined safe condition. It is, therefore, 
evident that the pilot valve construction of the present invention may be 
utilized either as a high or low pressure sensing pilot, depending solely 
upon the parameters of design. It is also obvious that the pilot valve 
mechanism of the present invention may be efficiently utilized separately 
for single pressure function control of a remotely located pilot pressure 
operated device, such as valve actuator and valve assembly. 
The pilot valve mechanism of the present invention has been found through 
tests to have excellent repeatability even though narrow ranges of 
pressure variation are involved. Repeatability and accuracy of the pilot 
valve mechanism is accomplished largely through the use of relatively 
friction-free piston sealing means and through the use of a tension spring 
for developement of force urging the piston and shuttle valve assembly 
downwardly against the influence of pressure within the pressure system 
being monitored. Repeatability and accuracy is further enhanced by the 
fact that the shuttle valve element need move only a slight distance from 
the annular sealing surface in order to allow full opening of a flow 
passage through the valve chamber, which opening is at least equal to the 
dimension of the port through which the pilot fluid is to flow either 
during supply or venting. The pilot valve mechanism of the present 
invention also includes sealing elements for both the piston mechanism and 
the shuttle valve assembly which sealing elements are prevented by 
appropriate retainer means from being displaced by fluid pressure. 
Moreover, the seal assembly for the piston mechanism incorporates a 
relatively friction-free sealing element that is urged by an O-ring or 
other suitable urging means into proper sealed engagement with the wall 
structure of the bore within which the piston is movably disposed. The 
friction-free sealing element, because of its composition, will not tend 
to adhere to the wall structure of the piston bore and, therefore, will 
not influence operating characteristics of the valve mechanism. 
In view of the foregoing it is apparent that the present invention is one 
well adapted to attain all of the objects hereinabove set forth, together 
with other advantages which will become obvious and inherent from a 
description of the apparatus itself. It will be understood that certain 
combinations and subcombinations are of utility and may be employed 
without reference to other features and subcombinations. As many possible 
embodiments may be made of this invention without departing from the 
spirit or scope thereof, it is to be understood that all matters herein 
set forth or shown in the accompanying drawings are to be interpreted as 
illustrative and not in a limiting sense.